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Microcellular sheet extrusion system process design models for shaping and cell growth control.
Microcellular plastics are innovative polymeric foams based on inert gas blowing agents such as carbon dioxide and nitrogen that have been demonstrated on thermoplastic, thermoset, elastomers, and liquid crystal polymers. Industrial application of these materials hinges on the development of processIng platforms capable of high volume production rates and compatible with existing infrastructure. Recent advances in microcellular polymer processing have demonstrated the feasibility of microcellular extrusion processes (1, 2). One of the critical steps in microcellular extrusion is maintaining the nucleation cell density of the polymer melt during shapIng operations through cell growth control. To prevent cell coalescence and deterioration of the nucleated cell density, one of these extrusion processes utilizes staged pressure drops to elimInate premature cell growth and maintain sufficiently small cell sizes (1, 3). Proper design of the extrusion system requires thoughtful design of the melt flow channel to maintain the accurate staged pressure drop and prevent loss of nucleated cells through cell coalescence. The complicated nature of the two phase polymer/gas solution flow precludes design of the flow channel using standard extrusion die design equations. In this paper, a series of design models are presented that approximate the pressure drop and flow rate experienced by a two-phase polymer/gas solution flow through a die channel. The intent of these design models is to capture the major physical attributes of the complicated flow and provide a means of quickly estimating the required flow channel geometry and/or evaluating, to first order, the feasibility of a flow channel design. These models have been implemented in spreadsheet form for rapid design turnaround.
Microcellular processing consists of three main processing elements: forming a polymer/gas solution, inducing a rapid thermodynamic instability that simultaneously nucleates a very large number of micro-voids, and controlling/stabilizing the expanding microcells (4-13). A scanning electron microscope (SEM) micrograph of a typical microcellular polymer cross-section is shown in Fig. 1. Microcellular polymers are characterized by cells sizes on the order of 10 [[micro]meter] and cell densities on the order of [10.sup.9] cells/[cm.sup.3]. in addition to superior performance in some applications (14-16), microcellular processing has the attractive feature of independent control over cell size and cell density allowing the materials to be designed for specific applications. Detailed descriptions of microcellular polymers and microcellular processing can be found elsewhere (5, 9, 10, 17).
In order to develop design models for rapid evaluation and feedback process control, the models have been based on first order approximations capturing the critical physics of the microcellular growth process. The primary application of these models is for use in initial concept design of microcellular foaming dies providing designers a rapid method for comparing various design strategies. The utility of such first order design models allow for rapid evaluation of design concepts and enable designers to approach the foaming die design from a "what if" prospective. Once the foaming die design concept is selected and the basic layout identified, detailed design analysis should be carried out using more robust and physically accurate models as presented by Amon and Denson (29), Arefmanesh et al. (23), Ramesh et al. (24), and Hah and Yoo (28).
The literature is rich with theoretical, and to a lesser extent, experimental treatments of cell growth in viscous, viscoeleastic, and elastic media. Epstein and Plesset (18) present one of the first theoretical treatments of cell growth in a supersaturated liquid-gas solution using an approximate solution. Gent and Tompkins (19, 20) and Hobbs (21) present theoretical and experimental treatments of cell growth in elastomeric materials. Amon and Denson (22) present a cell model to predict cell growth where neighboring cells compete for available gas. Arefmanesh et al. (23) have extended this analysis by relaxing the assumption that a single cell is representative of all cells. Recently, Ramesh et al. (24) have presented a numerical and experimental study of cell growth in microcellular processing comparing Newtonian, power-law, and viscoelastic models.
An additional class of models that have been developed focus on the injection molding process. Throne (25, 26) presents one of the earliest models predicting cell growth during injection of a gas-saturated polymer in structural foam molding. Many of the concepts introduced by Throne have been integrated into the design models presented in this work. Villamizar and Han (27) present one of the first empirical studies of foam injection molding, while Han and Yoo (28) present empirical data for structural foam molding as well as a theoretical cell growth model of a single spherical gas bubble in a viscoelastic matrix during isothermal mold filling. The focus of this model is to predict mold filling caused by expansion of the single cell when a short shot of a polymer/blowing agent system is injected into the mold. Using the DeWitt model, they are able to capture important viscoeleastic phenomena such as shear-dependent viscosity, normal stress effects, and stress relaxation. Amon and Denson (29) present a comprehensive study of cell growth during structural foam molding based on the cell model as a microscopic analysis for a short shot mold filling process. Their experimental data is based on bulk density measurements during mold filling. Upadhyay (30) developed a viseoelestic model based on the Leonov constitutive equation for the growth of a single bubble in an infinite medium comparing his model predictions with the data of Han and Yoo (28).
The continuous processing of microcellular polymers presented in previous work (1) is based on three sub-processes that include the processing of the polymer matrix, the processing of the microcellular structure, and the processing the net shape.(*) The creation of a microcellular structure is achieved by dissolving large gas concentrations into a polymer matrix and subjecting the saturated system to a rapid thermodynamic state change. This creates an unstable or supersaturated matrix that drives the nucleation of billions of microcells. Stable cells then grow as gas diffuses into the cells and reduces the bulk density of the material. based on these fundamental processing requirements, a hierarchical design strategy is used to synthesize the overall production system such that each of the processing functions is independently satisfied by a unique design parameter or process variable.
A schematic of the microcellular sheet extrusion system is shown in Fig. 2. The basic concept of this design is the use of a single screw plasticating extruder to process the polymer matrix, a staged pressure loss to produce a microcellular structure, and a foaming/shaping die to produce the net shape. The plasticating extruder is used to melt and pump the pellets so the polymer is suitable for downstream processing. The polymer processing is accomplished in the first stage of a two-stage extruder. At the beginning of the second extruder stage, the polymer/gas solution formation system begins. Here, a metered amount of gas or supercritical fluid is injected into the polymer melt and mixed to form a single phase solution using a technique presented previously (2, 31). The solution formation system supplies a single-phase solution at the exit of the breaker plate/flow stabilizer. Next, the single-phase solution flows into the foaming die system. The foaming die accomplishes the nucleation and cell growth functions of the microcellular processing system and the shaping function of the sheet processing system. A microcellular sheet then exits the foaming die and can be post-processed to achieve an appropriate molecular orientation, surface finish, etc. A comprehensive presentation of the microcellular extrusion system and the microcellular extrusion process is presented by Baldwin et al. (1).
The three critical processing functions of the foaming die are continuous nucleation, cell growth control, and shaping. In general, cell nucleation must be accomplished independently of cell growth and shaping, and cell growth must be accomplished independently of sheet shaping. To this end, the concept of shaping a nucleated polymer/gas solution flow is presented and experimentally verified. As an integral part of this development, first-order process models were developed to aid in the design process. Preliminary results indicate these models adequately quantify the limited experimental results supporting their relevance in microcellular foaming die design. Moreover, the results of the critical experiments verify the overall performance of the microcellular extrusion system.
To satisfy the pre-shaping cell growth control requirement, it is necessary to design a shaping and cell growth control die that can maintain the required shaping pressures in order to minimize cell coalescence and loss of nucleated cell density. The design of a shaping and cell growth control die requires knowledge of the pressure loss effects of nucleated polymer/gas solutions. in general, the flow of a nucleated polymer/gas solution is complex and involves a heterogeneous system consisting of a polymer melt with dispersed cells having relatively large center-to-center spacing compared with the average cell diameters [ILLUSTRATION FOR FIGURE 3 OMITTED]. The pressure loss in the flow results from frictional effects at the die walls. As the pressure decreases along the die channel, the nucleated cells grow resulting in an increase in the specific volume (or the decrease of density) of the two-phase system and the volumetric flow rate. Cell growth is driven by the pressure within the cells and diffusion of solution gas into the cells. Gas diffusion into the cells results from the decrease in solubility as the solution pressure decreases along the die channel. As the heterogeneous system expands, there is less polymer across any given area of the flow channel to support the shear stresses generated by the wall friction. This implies that the expanding solution has a lower apparent viscosity. The apparent viscosity also tends to decrease as a result of shear thinning as the volumetric flow rate increases.
The flow of a nucleated polymer/gas solution in a slit of height 2[center dot]B is sketched in Fig. 3 where [P.sub.s] is the nucleated solution pressure entering the die slit, [P.sub.exit] is the system pressure at the die exit, and L is the die slit length. Figure 3 also illustrates the influence of the high shear regions near the die walls that tend to elongate the expanding cells near the walls. The shear thinning nature of the polymer flow leads to relatively fiat velocity profiles in the center characteristic of plug flow. Similar two-phase flow morphologies are presented by Han and Villamizar (32) based on visualization studies for HDPE and PS flows blown with chemical agents.
For the purposes of designing foaming dies to satisfy the shaping and cell growth control requirements, it is necessary to develop models to estimate the pressure loss and flow rate of a nucleated polymer/gas solution during die flow. The problem can be divided into four limiting cases that span the range of possible flow configurations. The first case accounts for the fact that gas diffuses into the cells as the solution pressure decreases such that cell growth during the die flow is driven by both the gas pressure in the cells and the diffusion of gas into the cells. The second case assumes that negligible gas diffuses into the cells after nucleation such that cell growth during the die flow is driven by the gas pressure in the cells post-nucleation. This case represents an upper limit on the pressure loss during die flow. The third case assumes that all of the available solution gas diffuses into the cells prior to flowing into the die slit such that cell growth is driven by the gas pressure in the cells. This case represents a lower limit on the pressure loss in the die flow. The fourth case is similar to case two but accounts for the diffusion of gas into the cells prior to entering the foaming die and neglects gas diffusion during die flow. In the following discussion, each of the four modeling cases will be presented.
While the following analysis incorporates a number of simplifying assumptions, it is important to keep in mind the intent of the analysis, which is to develop and approximate design model for estimating the pressure loss and flow rates of nucleated polymer/gas solutions so that foaming dies can be sized appropriately. In this analysis, the model is kept as simple as possible while capturing the major physics of the complex two-phase flow. Such models have great utility in the design of prototype shaping and cell growth control devices. More important, they provide reasonable guidelines to the basic interactions of the major processing variables involved in continuous shaping and cell growth control operations.
Nucleated Flow With Concurrent Gas Diffusion
For the modeling case where the gas diffuses into the cells as the pressure decreases (i.e., the concurrent diffusion case), the pressure loss and volumetric flow rate of a nucleated polymer/gas solution can be estimated based on the frictional losses at the die walls. This is accomplished by treating the nucleated solution as a non-Newtonian fluid having a bulk viscosity and flow rate that are dependent on the volume fraction of cells (voids) in the polymer matrix (given by Eqs 1 and 2, respectively, where [[Phi].sub.v] is the volume fraction of voids).
[[Eta].sub.f] [equivalent to] [Eta]([[Phi].sub.v]) (1)
Q [equivalent to] Q([[Phi].sub.v]) (2)
Based on the apparent viscosity measurements of Oyanagi and White (33), the rheological behavior of polymeric foams follows similar shear-thinning behavior to the neat polymer. Moreover, Oyanagi and White's results indicate that the presence of a blowing agent tends to decrease the apparent viscosity by a multiplicative constant (i.e., showing equivalent power law factors, n). The developments of Draynik (34) in polymer foam theology also indicate decreases in apparent viscosity for many thermoplastic foam flow fields. Therefore, as a first order approximation, the non-Newtonian viscosity of the nucleated solution, [[Eta].sub.f], will be given by the modified power law relation of Eq 3 where [m.sub.f] is the power law constant of the foam.
[Mathematical Expression Omitted] (3)
The ability of the nucleated solution to resist shear forces is a strong function of the solution void fraction where the presence of cells or voids reduces the effective area of polymer resisting shear. Moreover, the viscosity of the gas within the voids is negligible compared with the viscosity of the polymer matrix. Therefore, the non-Newtonian viscosity of the nucleated solution can be approximated by Eq 4. For the case where the mass fraction of gas is relatively small, Eq 4 simplifies to Eq 5 where [[Rho].sub.p] is the polymer density and [v.sub.g/p] is the specific volume of the gas phase relative to the polymer mass. In this analysis, the expected decrease in the apparent viscosity due to the presence of dissolved gas in the polymer matrix has been neglected since reliable estimates for polystyrene/C[O.sub.2] systems are not available. Estimates of the apparent viscosity of polymer/gas solutions have been presented in two studies. Blyler and Kwei (35) have reported viscosity decreases of 20% and 22% in low and high density polyethylene containing 0.32% dissolved gas from the decomposition of a chemical blowing agent. Under the assumption that the gases produced from a decomposed chemical blowing agent are completely dissolved in a polymer melt, Han and Villamizar (32) estimated from experimental measurements an apparent viscosity decrease of 10 to 37% for polystyrene containing dissolved C[O.sub.2]. The impact of the apparent viscosity is discussed further in the model comparison section, where predicted results account for both reduced base polymer power law factors m due to dissolved gas and base polymer power law factors m for the neat polymer.
[m.sub.f] [equivalent to] m(1 - [[Phi].sub.v]) (4)
[m.sub.f] [equivalent to] m (1 - 1/1 + 1/[[Rho].sub.g][v.sub.g/p]) (5)
Using the power law approximation of Eqs 3 and 5, the bulk flow of a nucleated polymer/gas solution can be described by Eq 6 for steady, fully developed, non-Newtonian flow through a constant cross-section slit of height 2[center dot]B and width W (36). It should be noted that using the lubrication approximation, this analysis can be modified to accommodate gradual tapers in cross-sectional area where W = W(z) and B = B(z). in addition, as a first order approximation, the flow will be assumed isothermal and entrance effects will be neglected. The former assumption neglects any viscous work that can raise the flow temperature. For capillary flows, the viscous dissipation localized near the capillary walls can increase the melt temperature by 10 to 15 K (36). The later assumption can lead to large pressure errors in some flow fields, particularly at higher flow rates (37, 38).
- dp/dz = [[2 + 1/n/2W[B.sup.2]Q].sup.n] [m.sub.f]/B (6)
The total pressure loss can then be obtained by integrating Eq 6 over the slit length, L, where [P.sub.s] is the solution pressure at the slit entrance and [P.sub.exit] is the solution pressure at the slit exit. In Eq 7, the volumetric flow rate, Q, and the power law coefficient, [m.sub.f], are both functions of the local pressure, p.
[Mathematical Expression Omitted] (7)
In order to integrate Eq 7, the pressure dependence of the volumetric flow rate and power law factor must be determined. The volumetric flow rate of the nucleated solution can be determined by accounting for the specific volume of the polymer/gas system, [v.sub.m], which is a strong function of the local pressure. In the case of relatively low gas concentrations, the volumetric flow rate is given by Eq 8, where [Mathematical Expression Omitted] is the polymer mass flow rate.
[Mathematical Expression Omitted] (8)
Again using the approximation that the gas concentration is relatively low, the specific volume of the polymer/gas system is given by the sum of the specific volume of the gas phase relative to the polymer mass, [v.sub.g/p], plus the specific volume of the polymer matrix. Neglecting any swelling of the polymer matrix caused by the dissolved gas, the specific volume of the polymer is given by the inverse of the neat polymer density, [[Rho].sub.p]. In this case, the volumetric flow rate is given by
[Mathematical Expression Omitted]. (9)
To determine [v.sub.g/p], the gas within the cells can be treated as being in quasi-static equilibrium and approximated as a perfect gas such that the total volume of the gas phase, [V.sub.g], is given by
[V.sub.g] = [m.sub.g] RT/[P.sub.g] (10)
where [m.sub.g] is the mass of gas phase, R is the gas constant (equal to the universal gas constant divided by the molecular weight of the gas), T is the absolute temperature, and [P.sub.g] is the pressure of the gas phase. Here the gas phase in each cell is treated uniformly throughout the polymer/gas system (i.e., the cells are treated as having an equivalent average cell size). Mass conservation of the gas maintains that the mass of gas phase must equal the mass of the total gas initially dissolved into the polymer, [m.sub.T], less the mass of gas remaining in solution, [m.sub.s]. Equation 10 then becomes
[V.sub.g] = ([m.sub.T] - [m.sub.s]) RT/[P.sub.g]. (11)
The initial mass of dissolved gas is given by the initial gas concentration times the polymer mass. The mass of the remaining dissolved gas can be approximated usIng Henry's law assuming at any given instant the solution gas concentration is uniform and the system is in quasi-static equilibrium. Normalizing Eq 11 relative to the polymer mass then yields
[v.sub.g/p] = [V.sub.g]/[m.sub.p] = ([c.sub.[infinity]] - [K.sub.s](T)[P.sub.g])RT/[P.sub.g] (12)
where [c.sub.[infinity]] is the Initial gas concentration and [K.sub.s] is Henry's law constant. Inherent to Eq 12 is the assumption that at any given instant, a sufficient amount of gas has diffused Into the cells to establish a quasistatic equilibrium. Such a state is typified by uniform solution gas concentrations (i.e., no gas depleted regions around the cells). Strictly speaking, this assumption does not hold, although it provides a useful approximation in obtaining an estimate of the pressure loss and flow rates In the nucleation solution flows.
Based on the quasi-static approximation, the pressure of the gas phase can be related to the local solution pressure using Laplace's Eq 13 where the cells are treated as having a uniform radius, R, P is the solution pressure, and [[Gamma].sub.bp] is the surface tension of the gas/polymer interface. Note that the uniform cell radius is typically a reasonable assumption in microcellular processing because of the narrow cell size distributions achieved with this technology. Inherent to Eq 13 is the assumption that the cell growth dynamics are sufficiently rapid to allow near-equilibrium conditions to be achieved at any given instant. In addition, it should be noted that Eq 13 treats the flow field as a viscous medium and neglects the elastic energy of the polymer matrix. At higher melt temperatures, this is a reasonable approximation for many polymers. An alternate to Eq 13 would be to treat the expanding matrix as neo-Hookean and use the developments of Denecour and Gent (39) and Gent and Tompkins (19, 20).(**)
[P.sub.g] = 2[[Gamma].sub.bp]/R + P (13)
Next, it is necessary to relate the radius of the cells back to the specific volume of the gas phase. This can be achieved using Eq 14 for a known density of nucleated cells, [[Rho].sub.c] (remember that the cell density is determined by an independent processing step). Rearranging Eq 14 yields the average cell radius given by Eq 15.
[V.sub.g] = [[Rho].sub.c] [m.sub.p]/[[Rho].sub.p](4/3 [Pi][R.sup.3]) (14)
R [(3[[Rho].sub.p]/4[Pi][[Rho].sub.c] [v.sub.g/p]).sup.1/3] (15)
By combining Eqs 12, 13, and 15, an expression relating the gas phase pressure and the solution pressure is derived and given by Eq 16.
[Mathematical Expression Omitted] (16)
Calculating the gas phase pressure for a given solution pressure, requires Eq 16 to be solved iteratively, precluding a closed form solution of Eq 7. Therefore, a finite difference technique can be used to solve Eq 7. Using Fig. 3 as a reference, the slit flow can be divided into N elements of length [Delta]z. The incremental pressure drop [Delta]P over element i + 1 is then given by
[Delta][P.sub.i+1] [approximately equal to] [[2 + 1/n/2W[B.sup.2] [Q.sub.i]].sup.n] [m.sub.fi]/B [Delta]z (17)
and the total pressure at i + 1 is given by
[P.sub.i+1] [approximately equal to] [P.sub.i] + [Delta][P.sub.i+1] (18)
Equations 17 and 18 can be solved using the boundary condition that at the slit exit the solution pressure is given by P(x = L) = [P.sub.exit] = P(i = N). The solution to Eqs 17 and 18 is accomplished by determining the local gas phase pressure, [P.sub.g], at the solution pressure, [P.sub.i], via Eq 16. Equations 5, 9, and 12 can then be used to calculate the local power law coefficient, [m.sub.fi], and the local flow rate, [Q.sub.i]. The values of [m.sub.fi] and [Q.sub.i] are then used to calculate the local pressure drop, [Delta][P.sub.i+1], and the local pressure, [P.sub.i+1], using Eqs 17 and 18. This iterative solution proceeds until i equals N-1.
Pressure loss and flow rate estimates typical of nucleated solution flows during shaping and cell growth operations are presented in Fig. 4. The model parameters used for the calculations were for a polystyrene/C[O.sub.2] system having T = 150 [degrees] C, [[Rho].sub.p] = 1.04 g/[cm.sup.3], [[Gamma].sub.bp] = 0.0314 N/m (40), [[Rho].sub.c] = 1.5 x [10.sup.9] cells/[cm.sup.3], [K.sub.s] = 0.0039 kg(C[O.sub.2])/kg(PS)MPa (31), [c.sub.[infinity]] = 0.05, [Mathematical Expression Omitted], n = 0.29, and m = 40750 Pa [s.sup.n]. The slit dimensions used were B = 0.32 mm, W = 25.4 mm, L = 20.3 mm, and N = 20 (i.e., [Delta]z = 1.02 mm). The boundary condition used was [P.sub.exit] = 0.965 MPa (140 psi). This boundary condition is based on the findings of Han et al. (41) and Han and Villamizar (32). Hah and coworkers measured pressure profiles of polymer foam flows through various die geometries. These measurements revealed exit pressure losses equal to nearly 10% of the die entrance pressures.
Figure 4 demonstrates some of the important aspects of nucleated solution flows during shaping and cell growth operations. Notice that the volumetric flow rate increases parabolically along the slit length, and the solution pressure decreases non-linearly along the slit length. In contrast, a neat polymer flow would have a constant flow rate and a linear decrease in pressure over the slit length. The pressure loss trends of Fig. 4 can be understood by looking back at Eq 6. The decrease in pressure gradient along the slit length results from the decrease in the effective viscosity of the heterogeneous polymer/gas matrix along the slit length. The viscosity decrease follows from the expansion of the nucleated solution that reduces the effective area supporting the shear stresses. In this case, the viscosity decrease is sufficiently large to overcome the contributions of the increasing flow rate along the slit length. Notice from Eq 6 that an increasing flow rate tends to increase the pressure loss. The nonlinear pressure profiles predicted by this macroscopic treatment of nucleated solution flow agree in form with the experimental findings of Hah et al. (41) and Hah and Villamizar (32). Han and co-workers present pressure profile measurements in polymer foam flows indicating nonlinear trends similar to those of Fig. 4 with the exception of the pressure profiles near the exit reported by Han et al. (41), which show increased pressure gradients near the die exit.
Nucleated Flow With Post Gas Diffusion
In addition to the concurrent diffusion case presented above, it is important to understand the limiting cases for the flow of nucleation polymer/gas solutions. Predicting the limiting cases will provide a useful comparison for the intermediate models and will further illustrate the critical processIng characteristics that need to be addressed in the design of shaping and cell growth control devices.
As a limiting case, consider the flow of a nucleated polymer/gas system in which only the gas present in the stable nuclei is available for expanding the cells (i.e., the post-diffusion case). In this case, gas diffusion into the cells is treated as being very slow compared with the flow rate during shaping operations. All of the appreciable gas diffusion occurs post-shaping. The analysis follows the same lines and is restricted by the same assumptions of the previous section. Again, the flow field of interest is a planar slit flow of a nucleated polymer/gas solution as shown in Fig. 3.
The gas phase present in the stable nuclei can be determined based on classical nucleation theory. For spherical nuclei, the critical radius size, [R.sub.o], is given by
[R.sub.o] [r.sup.*] = 2[[Gamma].sub.bp]/[Delta][P.sub.nuc] (19)
where [Delta][P.sub.nuc] is the pressure change used to instigate the thermodynamic instability for nucleation. The mass of the gas phase can then be determined by equating Eqs 10 and 14 and substituting Eq 19 for the solution conditions post-nucleation. Immediately after nucleation, the solution temperature is [T.sub.n] and the pressure of the gas phase in the cells is [P.sub.go] [approximately equal to] [Delta][P.sub.nuc]. The mass of the gas phase immediately after nucleation is then given by
[Mathematical Expression Omitted]. (20)
Substituting Eq 20 into Eq 10 yields the specific volume of the gas phase relative to the polymer mass given by Eq 21. The specific gas volume applies at any point along the flow field under the assumption that the gas amount is fixed at the nucleation stage.
[Mathematical Expression Omitted] (21)
In Eq 21, T is the solution temperature during the slit flow that can be different from the solution temperature at nucleation.
Finally, an expression for the gas phase pressure as a function of the solution pressure can be obtained by substituting Eq 15 and 21 into Eq 13.
[P.sub.g] = P + [Delta][P.sub.nuc] [[T/[T.sub.n] [Delta][P.sub.nuc]/[P.sub.g]].sup.-1/3] (22)
Equation 22 can then be used to evaluate the pressure of the gas phase as a function of the local solution pressure. In order to determine the local pressure change and the local solution pressure via Eqs 17 and 18, Eq 22 can be used to evaluate the local gas phase pressure, [P.sub.g]. Equation 21 can then be used to calculate the local specific volume of the gas. The local volumetric flow rate and the local power law coefficient can then be determined from Eqs 9 and 5. Finally, the pressure loss and the volumetric flow rate profiles along the slit can be determined using a finite difference technique.
Nucleated Solution Flow With Complete Gas Diffusion
As a second limiting case, consider the flow of a nucleated polymer/gas system in which all of the available gas has diffused into the cells prior to shaping or cell growth operations (i.e., the pre-diffusion case). In this case, gas diffusion into the cells is treated as being very rapid compared with the flow rate such that all of the available gas diffuses into the cells prior to shaping. The analysis follows the same lines and restrictions as above. Again, the flow field of interest is a planar slit flow of a nucleated polymer/gas solution as shown in Fig. 3.
By assumption, all of the available gas has diffused into the cells prior to the slit flow. Therefore, the mass of the gas phase is constant throughout the shaping process. In this case, the initial gas concentration is determined independently by the solution formation system such that the mass of the gas is given by
[m.sub.g] = [c.sub.[infinity]][[m.sub.p]. (23)
The specific volume of the gas phase relative to the polymer mass is obtained by substituting Eq 23 into Eq 10.
[v.sub.g/p] = [c.sub.[infinity]] RT/[P.sub.g] (24)
In the case of complete gas diffusion, the local gas phase pressure can be obtained by substituting Eqs 24 and 15 into Eq 13, yielding
[P.sub.g] = P + 2[[Gamma].sub.bp] [[3[[Rho].sub.p]/4[Pi][[Rho].sub.c] RT/[P.sub.g] [c.sub.[infinity]].sup.-1/3] (25)
Equation 25 can then be used to evaluate the pressure of the gas phase as a function of the local solution pressure. In order to determine the local pressure change and the local solution pressure via Eqs 17 and 18, Eq 25 can be used to evaluate the local gas phase pressure, [P.sub.g]. Equation 24 can then be used to calculate the local specific volume of the gas. The local volumetric flow rate and the local power law coefficient can then be determined form Eqs 9 and 5. Finally, the pressure loss and the volumetric flow rate profiles along the slit can be determined using a finite difference technique.
Nucleated Solution Flow With Partial Gas Diffusion
A final case to consider for the flow of a nucleated polymer/gas solution is a variation of that presented above. In this case, the gas is assumed to diffuse into the cells prior to slit flow creating a quasi-static equilibrium state where the gas concentrations are uniform and the mass of gas in the cells is uniquely determined by the solution pressure at the inlet to the slit, [P.sub.s] (i.e., the partial pre-diffusion case).
First, the gas mass available prior to entering the slit flow must be determined. To accomplish this, it is assumed that a quasi-static equilibrium condition is reached just upstream of the slit where equilibrium mass of gas has diffused into the cells and uniform gas concentrations have been achieved in the solution. Using Henry's law and an initial gas phase pressure, [P.sub.go], just upstream of the slit, the constant mass of the gas phase is given by
[m.sub.g] = ([c.sub.[infinity]] - [K.sub.s](T)[P.sub.go])[m.sub.p]. (26)
Substituting Eq 26 into Eq 10 gives the specific volume of the gas phase.
[v.sub.g/p] = [V.sub.g]/[m.sub.p] = ([c.sub.[infinity]] - [K.sub.s](T)[P.sub.go]) RT/[P.sub.g] (27)
Using an analogous derivation of the gas phase pressure presented in the previous section, the initial gas phase pressure just upstream of the slit, [P.sub.go], is given by Eq 28 where [P.sub.s] is the solution pressure just upstream of the slit. Equation 28 can be used to determine [TABULAR DATA FOR TABLE 1 OMITTED] the gas phase pressure when the inlet solution pressure, [P.sub.s], is known.
[P.sub.go] = [P.sub.s] + 2[[Gamma].sub.bp] [[3[[Rho].sub.p]/4[Pi][[Rho].sub.c] RT/[P.sub.go] ([c.sub.[infinity]] - [K.sub.s](T)[P.sub.go])].sup.-1/3] (28)
Similarly, the gas phase pressure at any point in the slit flow field is given by Eq 29.
[P.sub.g] = P + 2[[Gamma].sub.bp] [[3[[Rho].sub.p]/4[Pi][[Rho].sub.c] RT/[P.sub.g] ([c.sub.[infinity]] - [K.sub.s](T)[P.sub.go])].sup.-1/3] (29)
Equation 28 can be used to evaluate the initial pressure of the gas phase at the slit inlet using an estimated solution pressure at the slit inlet. Equation 29 can then be used to evaluate the pressure of the gas phase as a function of the local solution pressure. In order to determine the local pressure change and the local solution pressure via Eqs 17 and 18, Eq 29 can be used to evaluate the local gas phase pressure, [P.sub.g]. Equation 27 can then be used to calculate the local specific volume of the gas. The local volumetric flow rate and the local power law coefficient can then be determined form Eqs 9 and 5. Finally, the pressure loss and the volumetric flow rate profiles along the die slit can be determined using the finite difference technique discussed above.
Comparison of Nucleated Solution Flow Models
In order to compare these four models, the parameters given in Table 1 for a polystyrene/C[O.sub.2] system typical of microcellular polymer sheet extrusion were used. The pressure profile results from the concurrent diffusion model, the post-diffusion model, the pre-diffusion model, and the partial pre-diffusion model are plotted in Fig. 5. Notice first that the post-diffusion case (i.e., where only the nucleated gas phase is present during slit flow) and the pre-diffusion case (i.e., where all of the solution gas is present in the gas phase) give the upper and lower pressure loss limits for the nucleated solution flow. The total pressure losses predicted by these limiting eases differ by 63%. The post-diffusion case is interesting in that it has a constant pressure gradient similar to the neat polymer flow. From closer inspection of this case, it is found that the post-diffusion case and the neat polymer flow are identical based on the approximation that the apparent viscosity of the polymer/gas system is equal to that of the neat polymer. This results from the assumption that only the nucleated gas phase is available for expanding the cells during slit flow. Since the nucleated gas phase has very little volume, the initial cell size is quite small, which leads to large surface tension contributions and negligible cell growth as the solution pressure decreases.
A similar situation holds for the partial pre-diffusion case where it is assumed equilibrium concentrations exist prior to slit flow, and gas diffusion during slit flow is negligible. This case also demonstrates a nearly constant pressure gradient. In addition, notice that the pressure gradient is less than that of the post-diffusion ease (the neat polymer flow). The lower pressure gradient results from the finite cell size and specific volume of gas phase existing upstream of the slit. The presence of these cells tends to lower the bulk viscosity of the nucleated solution flow.
The pressure loss results for the concurrent diffusion and pre-diffusion cases both show nonlinear behavior with decreasing pressure gradients along the slit length. The decreasing pressure gradients indicate that the viscosity changes dominate the pressure loss despite the fact that the flow rates increase along the slit length.
Since the rationale of designing the die is to maintain small cell sizes during shaping operations, it is important to compare the estimated average cell sizes for the four models. The post-diffusion model estimates an average cell radius at the slit inlet of 0.00021 [[micro]meter]. At the other limit, the pre-diffusion case estimates a cell radius of 4.0 [[micro]meter]. The concurrent diffusion and partial pre-diffusion cases estimate entrance cell radii of 1.9 [[micro]meter] and 2.2 [[micro]meter], respectively. Since the final cell size range for microcellular polymers is 10 to 20 [[micro]meter], initial shaping cell sizes around 2 [[micro]meter] should be sufficient to prevent degradation of the cell density and therefore satisfy the pre-shaping cell growth control functional requirement. Indeed this is the ease based on the initial experimental results presented later in this section. In terms of the final cell sizes, the pre-diffusion, concurrent diffusion, partial pre-diffusion, and post diffusion models predict final cell radii of 8.5, 8.3, 5.2, and 0.002 [[micro]meter], respectively.
The estimates of Figs. 5 and 6 have a number of implications on the design of shaping and cell growth control devices. in general, each of these eases can be associated with a particular type of die design and system flow depending on a dimensionless parameter consisting of the characteristic flow rate and the characteristic gas diffusion rate. The characteristic flow rate of a fluid particle is given by
[Mathematical Expression Omitted] (30)
where L is the channel length and A is the channel cross-sectional area. The characteristic diffusion rate is given by
[Mathematical Expression Omitted] (31)
where the characteristic diffusion distance is approximated by the center-to-center distance between cells, [Mathematical Expression Omitted].
In general, one can associate the different flow cases with a particular foaming die configuration as summarized in Table 2 based on the ratio of Eq 32. Notice, at very high processing rates, the nucleated solution flow would tend to behave more like the post-diffusion flow of Figs. 4 and 5. This follows since at very high processing rates the die flow occurs over a much shorter time frame then that of gas diffusion into the cells. For foaming die designs having large post-nucleation channel volumes ([L.sub.pn] [A.sub.pn]) and relatively small shaping channel volumes ([L.sub.s] [A.sub.s]), the nucleated solution flow would tend to behave like the partial pre-diffusion case. In this case, enough time is allowed for gas diffusion to equilibrate prior to slit flow. However, during slit flow, velocities are sufficiently large to inhibit appreciable gas diffusion. If the flow rates and diffusion rates are on the same order, then the concurrent diffusion case would tend to estimate the correct pressure loss and flow rates. Finally, under conditions where the flow rates are low and the flow channel volumes (L A) are high, the pre-diffusion case would tend to estimate the correct pressure losses and flow rates of nucleated polymer/gas solutions.
[Mathematical Expression Omitted] (32)
To verify the general applicability of the design models, a critical experiment was conducted to compare the flow rate results of a specific foaming die design, namely the die design of Table 1, with the analysis results of Figs. 4 through 6. The details of the experiment are presented elsewhere (1, 3). The plots in Figs. 4 through 6 correspond to the same flow parameters as the planar sheet extrusion experiments presented previously (1, 3). In this experiment, the microcellular sheet extrusion system of Fig. 2, without post sheet processing heaters or stretching, was used with the process parameters of Table I to produce microcellular sheets. Details of the die design and processing system are presented by Baldwin, Park, and Suh (1-3, 9, 31). For the experimental microcellular sheet extrusion system, Eq 32 yields:
[Mathematical Expression Omitted]
Therefore, the nucleated sheet die flow fell between the concurrent diffusion case and the pre-diffusion case based on Table 2. Furthermore, the shaping pressure achieved by the foaming die, [P.sub.s] = 9.65 MPa (1400 psi) (also plotted in [ILLUSTRATION FOR FIGURE 5 OMITTED]), was in reasonable agreement with the predicted values of 10 MPa and 11.5 MPa (1450 psi and 1670 psi) for the pre-diffusion and concurrent diffusion flow configurations. Moreover, if in Eq 4 one accounts for the lower apparent viscosity of polymer/gas solutions, the model results and experiment comparison improves. based on Han and Villamizar's (32) measurements, an estimated average apparent viscosity decrease for polystyrene/gas systems is 20% (where values reported range from a 10 to 37% reduction). Note that an average is used to approximate the increase in apparent viscosity expected as the dissolved gas diffuses from solution into the expanding cells thereby lowering the dissolved gas concentrations in solution during the growth process. If in Eq 4, m is decreased by 20% to reflect an average apparent viscosity decrease for a polystyrene/C[O.sub.2] solution, the pre-diffusion, concurrent diffusion, partial pre-diffusion, and post-diffusion models predict shaping pressures (at the foaming die inlet) of 8.8, 10.2, 12.7, and 14.4 MPa, respectively. This also illustrates the importance of accurate apparent viscosity data for polymer/gas solutions. While the results of Blyler and Kwei (35) and Han and Villamizar (32) provide important insights to this phenomena, it is clear that further research in this area is needed.
Based on the cell morphology and geometry of the extruded microcellular PS for a nucleated cell density of 1.5 x [10.sup.9] cells/[cm.sup.3] with an average cell size of 11[[micro]meter], the feasibility of nucleating and post-shaping a polymer/gas solution and extruding microcellular polymers has been demonstrated. Also, notice the predictions based on the neat polymer flow over-predicted the actual pressure loss by 66%. Thus, the pressure loss estimates from the nucleated solution flow models appeared to capture the major physics of the shaping and cell growth processes to provide reasonable estimates for foaming die designs.
The volumetric flow rate results for the four nucleated polymer/gas solution flow models are shown in Fig. 6. Notice first the limiting flow rates given by the post-diffusion case and the pre-diffusion case. The post-diffusion case demonstrates a constant flow rate equal to the neat polymer flow that results from the negligible expansion of the nucleated gas phase during slit flow. in contrast, the pre-diffusion case shows a rapid increase in flow rate over the slit length resulting from the expanding cells that contain all the available gas. Notice further that the pre-diffusion case has an initial flow rate twice that of the neat polymer because of the larger initial cell size at the slit entrance. The intermediate case of concurrent diffusion shows flow rate trends similar to the pre-diffusion case with slightly larger gradients near the slit exit because of the larger expansion rates occurring for simultaneous gas diffusion. The other intermediate case of partial pre-diffusion, where equilibrium conditions are reached prior to entering the slit and no diffusion occurs in the slit, shows a more gradual change in the flow rate over the slit length since the gas available to expand the cells is limited.
Finally, the analysis of the previous sections applies equally well for tubular filament flows. in this case, Eq 33 is substituted for Eq 6 where D is the diameter of the tube. The solution to Eq 33 proceeds in a similar manner to the slit flow case where a finite difference technique is used to locally solve the relative pressure loss and solution pressure.
[Mathematical Expression Omitted] (33)
Again, a critical experiment was conducted to compare the flow rate results of a specific foaming die design, namely the tubular filament die design of Table 1, with the analysis results of Fig. 7. The shaping pressure achieved by the foaming die, [P.sub.s] = 6.89 MPa (1000 psi) plotted in Fig. 7, was in reasonable agreement with the predicted values of 7.2 MPa and 8.1 MPa (1040 psi and 1170 psi) for the pre-diffusion and concurrent diffusion flow configuration plotted in Fig. 7. based on the cell morphology and geometry of the extruded microcellular PS for a nucleated cell density of 1.0 x [10.sup.9] cells/[cm.sup.3] with an average cell size of 10 [[micro]meter], the feasibility of nucleating and post shaping a polymer/gas solution and extruding microcellular polymers has also been demonstrated for filaments. This reconfirms that the nucleated solution flow models appeared to capture the major physics of the shaping and cell growth processes to provide reasonable estimates for foaming die designs.
In this paper, a new microcellular sheet extrusion system was presented based on the principle of shaping a nucleated polymer/gas solution flow under pressure and close temperature control. In this way, the initial cell growth was controlled to prevent degradation of the nucleated cell density during shaping. Cell growth control was achieved using carefully designed foaming dies. The die designs were accomplished using a series of design models that comprise the majority of this paper. The sheet extrusion systems and design models were verified form experiments validating the concept of shaping a nucleated polymer/gas solution.
The feasibility of shaping a nucleated polymer/gas solution represents a significant advancement for microcellular plastics process technology. Through proper design of the foaming die, nucleated solution flows can be shaped to arbitrary dimensions while maintaining the functional independence of cell nucleation, cell growth, and shaping. To maintain functional independence, stringent pressure and temperature design specifications, which supersede those of conventional foam processing, must be met by the foaming die design. As a means of aiding the design process, a series of models were developed for predicting pressure losses and flow rates of nucleated polymer/gas solutions. A comparison of the model predictions and the actual foaming die design performance showed good agreement for limited data. Moreover, the relatively simple models capture the major physics of the complicated two-phase flow field and provide a sound base from which scale-up of the foaming die concept to industrial levels can be achieved.
In general, the concurrent diffusion and the pre-diffusion models showed the best agreement with the limited experimental data. Moreover, these models predicted a nonlinear pressure loss through the die that has been experimentally measured by Han and coworkers (29, 41). The decreasing pressure gradients predicted by the concurrent diffusion and pre-diffusion models indicate that viscosity changes dominate the pressure loss despite the fact that the flow rates increase along the die length. It is also found that predictions based on the neat polymer flow over-predict the actual pressure loss by 66%. The concurrent diffusion and pre-diffusion models predict highly nonlinear volumetric flow rates in contrast to the constant flow rate predicted for the neat polymer flow and the post-diffusion model. Finally, a convenient method for classifying nucleated polymer/gas solution flow was presented based on the dimensionless ratio of the characteristic flow rate to the characteristic gas diffusion rate. Flow classification allows for the rapid identification of the appropriate design model for microcellular foaming die design.
The authors would like to thank Dr. Bruce M. Kramer and Dr. Maria Burka for their interest in this work and the National Science Foundations, Grant Number CTS-9114738, for supporting this research. This work was performed at the MIT-Industry Microcellular Plastics Research Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts.
B = Half slit height of channel [m].
c = Instantaneous or local equilibrium concentration of gas molecules [kg(gas)/kg(polymer)].
[c.sub.eq] = Equilibrium concentration of gas in a polymer [kg(gas) / kg(polymer)].
[c.sub.w] = Gas concentration at the cell wall surface [kg(gas)/kg(polymer)].
[c.sub.[infinity]] = Initial equilibrium gas concentration [kg(gas)/kg(polymer)].
D = Diameter of tubular flow channel [m].
[K.sub.s] = Henry's law constant [kg(gas)/kg(polymer)Pa].
L = Flow channel length [m].
m = factor in power law constitutive equation [Pa [s.sup.n]].
[m.sub.f] = Power law coefficient for the nucleated polymer/gas solution [Pa [s.sup.n]].
[m.sub.g] = Mass of the gas phase [kg].
[m.sub.p] = Mass of the polymer [kg].
[m.sub.s] = Mass of the gas remaining in solution [kg].
[m.sub.T] = Total mass of the gas [kg].
[Mathematical Expression Omitted] = Polymer mass flow rate [kg/s].
n = Exponent in power law constitutive equation.
[p.sub.g] = Gas pressure in a cell or bubble [Pa].
[p.sub.[infinity]] = Pressure of the polymer far from the cells [Pa].
[P.sub.b] = Barrel pressure at the gas injection port [Pa].
[P.sub.exit] = Pressure at the foaming die exit [Pa].
[P.sub.g] = Pressure of the gas phase in the calls [Pa].
[P.sub.n] = Pressure at the nucleation device [Pa].
[P.sub.s] = Shaping pressure at the foaming die inlet [Pa].
[Delta]P = Pressure loss along the flow channel ([P.sub.inlet] - [P.sub.outlet]) [Pa].
[Delta][P.sub.nuc] = Effective pressure change driving nucleation [Pa].
Q = Volumetric flow rate [[m.sup.3]/s].
R = Average cell radius [m].
R = Universal gas constant/molecular weight of the gas [J/kg K].
T = Absolute temperature [K].
[T.sub.n] = Temperature at nucleation [K].
[T.sub.s] = Temperature at shaping [K].
[v.sub.g/p] = Specific volume of the gas phase relative to the polymer mass [[m.sup.3]/kg].
[v.sub.m] = Specific volume of the polymer/gas system [[m.sup.3]/kg].
[v.sub.r] = Radial velocity component of the polymer or polymer/gas interface [m/s].
W = Width of the flow channel slit [m].
[Delta]z = incremental distance along the flow channel (L/N) [m].
[[Phi].sub.v] = Volume fraction of gas phase.
[[Gamma].sub.bp] = Surface energy of the polymer/bubble interface [N/m].
[Eta] = Non-Newtonian apparent viscosity [Pa s].
[[Rho].sub.p] = density of polymer [kg/[m.sup.3]].
* A detailed presentation of the microcellular sheet extrusion system design is presented by Baldwin (1, 2).
** If the expanding cells are treated as having thin shells d thickness, [t.sub.o], supporting the extensional stresses, then the relationship between the cell pressure and radius is given by (where G is the shear modulus and [R.sub.o] is the initial cell radius)
[P.sub.g]/G = (2[t.sub.o]/[R.sub.o])(([R.sub.o]/R) - [([R.sub.o]/R).sup.7]).
If the expanding cells are approximated as having thick or infinite walls, then the cell pressure is given by
[P.sub.g]/G = 5/2 - 2([R.sub.o]/R) - (([R.sub.o]/R).sup.4])/2.
See Gent and Tompkins (19, 20) for similar expressions accounting for the pressure surrounding the cells.
1. D. F. Baldwin, C. B. Park, and N. P. Suh, Polym. Eng. Sci., 36, 1446 (1996).
2. C. B. Park, D. F. Baldwin, and N. P. Sub, Polym. Eng. Sci. 35, 432 (1995).
3. D. F. Baldwin, PhD thesis, Mech. Eng., MIT, Cambridge, Mass, (1994).
4. J. E. Martini-Vvedensky, N. P. Suh, and F. A. Waldman, U.S. Patent 4,473,665 (1984),
5. J. Martini, F. A. Waldman, and N. P. Suh, SPE ANTEC Tech. Papers, 28, 674 (1982).
6. V. Kumar and N. P. Suh, Polym. Eng. Sci., 30, 1323 (1990).
7. J. S. Colton and N. P. Suh, U.S. Patent 5,160,674 (1992).
8. S. W. Cha, N. P. Suh, D. F. Baldwin, and C. B. Park, U.S. Patent 5,158,986 (1992).
9. N. P. Suh, D. F. Baldwin, S. W. Cha, C. B. Park, T. Ota, J. Yang, and M. Shimbo, Proc. 1993 NSF Des. Manuf. Sys. Grantees Conf., 315 (1993).
10. D. F. Baldwin, D. E. Tate, C. B. Park, S. W. Cha, and N. P. Sub, J. Jap. Soc. Polym. Proc., 6, 187 & 245 (1994).
11, D. F. Baldwin, M. Shimbo, and N. P. Sub, J. Eng. Matls. Tech., 117, 62 (1995).
12. D. F. Baldwin, C. B. Park, and N. P. Suh, Polym. Eng. Sci., 36, 1425 (1996).
13. D. F. Baldwin, C. B. Park, and N. P. Suh, Polym. Eng. Sci, 36, 1437 (1996).
14. F. A. Waldman, S. M. thesis, Mech. Eng,, MIT, Cambridge, Mass. (1982].
15. J. Youn and N. P. Sub, Polym. Compos., 6, 175 (1985).
16. D. I. Collias, et al., Polymer, 35, 3978 (1994).
17. V. Kumar, Proc. Manuf. Composite Matls., ASME, 185 (1991).
18. P. S. Epstein and Pesset, J. Chem. Physics, 18, 1505 (1950).
19. A. N. Gent and D. A. Tompkins, J, Appl. Phys.. 40, 2520 (1969).
20. A. N. Gent and D. A. Tompkins, J. Polym. Sci.: A-2, 7, 1483 (1969).
21. S. Y. Hobbs, Polym Eng. Sci., 16, 270 (1976).
22. M. Amon and C. D. Denson, Polym. Eng. Sci., 24, 1026 (1984).
23. A. Arefmanish, S. G. Advani, and E. E. Michaelides, Polym. Eng. Sci., 30, 1330 (1990).
24. N. S. Ramesh, D. H. Rasmussen, and G. A. Campbell, Polym. Eng. Sci., 31, 1657 (1991).
25. J. L. Throne, Sci. Tech. Polym. Proc., N. P. Suh and N-H Sung, eds., MIT Press, Cambridge, Mass. (1979).
26. J. L. Throne, J. Cellular Plast., 12, 161 (1976).
27, C. A. Villamizar and C. D. Han, Polym. Eng. Sci., 18, 699 (1978).
28. C. D. Han and H. J. Yoo, Polym. Eng. Sci., 21, 518 (1981).
29, M. Amon and C. D. Denson, Polym. Eng. Sci., 26, 255 (1986).
30. R. K. Upadhyay, Adv. Polym. Tech., 5, 55 (1985).
31. C. B. Park, PhD thesis, Mech. Eng., MIT, Cambridge, Mass. (1993).
32. C. D. Han, and C. A. Villamizar, Polym. Eng. Sci., 18, 687 (1978).
33. Y. Oyanagi and J. L. White, J. Appl. Polym. Sci., 23, 1013 (1979).
34. A. M. Kraynik, Polym. Eng. Sci., 21, 80 (1981).
35. L. L. Blyler and T. K. Kwei, J. Polym. Sci.: C, No. 35, 165 (1971).
36. R. B. Bird, R. C. Armstrong, and O. Hassager, Dynamics of Polymeric Liquids: Volume 1. Fluid Mechanics, John Wiley & Sons, New York (1987).
37. Z. Tadmor and C. G. Gogos, Principles of Polymer Processing, Wiley, New York (1979).
38. S. A. White, A. D. Gotsis, and D. G. Baird, J. Non-New. Fluid Mech., 24, 121 (1987).
39. R. L. Denecour and A. N. Gent, J. Polym. Sci.: A-2, 6, 1853 (1968).
40. S. Wu, Polymer Interface and Adhesion, p. 67, Marcel Dekker, New York (1982).
41. C. D. Han, Y. W. Kim, and Malhotra, K. D., J. Appl. Polym. Sci., 20, 1583 (1976).
Reader Opinion
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|Baldwin, Daniel F.; Park, Chul B.; Suh, Nam P.
|Polymer Engineering and Science
|Apr 1, 1998
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text:
28 containers transform orphanage in South Africa
February 15, 2013
Having last looked at a temporary use of shipping containers as building blocks, with O+A's festival backdrop in Amsterdam, we're back in permanent territory (as permanent as new buildings are, that is) with 4D and A Architects' shipping container housing at New Jerusalem Orphanage at Gauteng, South Africa. The project is among the more ambitious uses of shipping containers we've seen, using 28 containers in all. Gizmag spoke briefly to its designers to find out more about it.
In an email to Gizmag, Mia Anfield of 4D and A wrote that the idea to use shipping containers came from the fact that two were already on site for storage. The company had already been interested in the work of Adam Kalkin, an American architect and prefabrication specialist who was among the first to put shipping containers to use as houses. The designers, it seems, simply put two and two together.
Completed in December, 2011, the entire construction period lasted six months, though Anfield points out that this was delayed by the arrival of materials to the site, many of which were donated. The project used 28 6- and 12-meter (20- and 40-foot) containers arranged both vertically and horizontally.
One consideration when building with shipping containers is thermal performance, particularly during cold weather or on hot, sunny days. We put this to Anfield, who said that design measures included "orientation of the building, timber screens constructed of eco-friendly composite decking, use of a roof garden for thermal mass and the inside walls and ceilings of the containers were clad in dry wall plus 50mm Isotherm foam insulation." The containers were raised on plinths to encourage the flow of air.
As part of the project, the old brick-built sleeping accommodation was converted into a new kitchen and dining room. The orphanage has also been fitting with solar thermal and photovoltaic systems.
Update September 7, 2013: This article has been amended, as the previously stated dimensions of the shipping containers, at 12 x 6 m, were incorrect.
The problem with architects is that they are always trying to make a pretty picture. While I am glad that the children get the comforts provided I think more good could have been done had they used containers to create maximum inclosed floor space inside and between the containers.
I would have gone with all solar thermal and used Stirling cycle engines to generate electricity using stored heat and combustion to provide 24/7 power.Slowburn
I think it is a very clever idea to use containers for the orphanage. I like the way it uses what they have to create a building.BigGoofyGuy
This is a beautiful idea. Orphans don't demand for much and here we see how they have built with little. I only hope that much care has been given to fire and health concerns.
I hope that this container approach gives rise to many more orphanages around the world. The best part is that these containers can be painted in beautiful colours!Nantha
I love it. I disagree with Slowburn, creative environments breeds creativity. (Just look at the Google offices) Growing up in a pretty and creative building will surely have a positive impact on these children.
Imagine the wonder on the face of a deprived oprhan seeing this building for the first time, and standing looking up into the tower.Riaanh
While I think it is a great idea to use shipping containers for an orphanage, I have often wondered why they are not being used as temporary housing for the people in Haiti? The tents they are staying in offer very little protection from the environment and the people are unsafe from invasion.Lynn Russell
Hey,Slowburn- Built any orphanages lately? What good is "would have done"? I say it's a great job and they should make it beautiful and artistic! What point did the little bluebird sculpture have? What point did it have to have? Orphans need healing-not just housing.
This is a showcase work of art that illustrates what one of the ugliest industrial symbols of "waste in the name of efficiency" on this earth can become through Love and Art!
Hey, I say make inspiration-entertainment toys based on this that can teach and inspire junior "art-chitects" while helping raise funds and awareness for the real deal!
There is more to life than illusions of efficiency and busy-ness.Griffin
The wooden floors look pretty standard for the containers I have seen.Doyle Dowd
Healing comes from people interacting in beneficial ways. The question of greatest good. Does giving 100 orphans luxurious accommodation do more good than merely giving 200 orphans safe dorms?Slowburn
Thanks for the wonderful comments, we can't keep everybody happy as art or architecture is subjective......when I entered the orphange once it was occupied, I found a newspaper article cut-out and stuck on the cupboard of one the orphans, she had written above the article "my new five star home" I think we achieved the unthinkable - a place of belongingSean Wall
Very impressive and artsy too! The ornate staircase looks more expensive than it needed to be, however. No mention of how many children live here, tho Slowburn mentioned 100 in his/her droll comment. I say skip the fancy $tuff and build hundreds more of these little beauties! The kids have got to love 'em.WagTheDog

subset: commoncrawl


text:
I was kinda shocked at first because I totally remember reading about this blatant Uncharted rip-off like a year ago, if not longer. I guess it's sorta... heart-warming to see that it's actually amounted to something even still, even if that something is looking to be a poorly made ripoff that looks and animates like a HD PS2 game. I can't imagine there are many Saudi-Arabian games being developed these days, though, so I'm definitely intrigued about this thing all the same.
Probably not enough to pay like £6 on PSN for it, however. Especially since that's only for the first episode for what then must be an episodic series. A quick-look could be pretty fun at least.
Here's a story trailer anywhoo so as to wet your appetite for now...
Kinda funny how they've got David Lodge voicing both the narrator and the evil villain guy, doing the bare minimum to mix up his voice.


text:
Thyroid Disorders Center - Grand Forks, ND
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A subspecialty certification by the Board of Internal Medicine; practitioners treat disorders of the internal (endocrine) glands such as the thyroid and adrenal glands. Endocrinology also deals with disorders such as diabetes, metabolic and nutritional disorders, pituitary diseases, and menstrual and sexual problems.
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text:
Munmorah Power Station
|Munmorah Power Station
Munmorah Power Station
|near Doyalson, Lake Munmorah, New South Wales
|33°12′42.41″S 151°32′31.78″E / 33.2117806°S 151.5421611°ECoordinates: 33°12′42.41″S 151°32′31.78″E / 33.2117806°S 151.5421611°E
|Commission date
|Decommission date
|Delta Electricity
|Thermal power station
|Primary fuel
|Bituminous coal
|Steam Turbine
|Power generation
|Units operational
|Nameplate capacity
Munmorah Power Station was a coal fired electricity power station with four 300 MW English Electric steam driven turbo-alternators for a combined capacity of 1400 MW. The station is located near Doyalson, on the shores of Lake Munmorah, New South Wales, Australia and is owned and operated by Delta Electricity, a company owned by the New South Wales Government.
4 Gas Turbine Plants at Colongra have been installed recently, however the coal fired generators have been permanently retired from service.
History and facilities[edit]
The station was constructed with 4 English Electric 350 MW turbo-alternators. Munmorah had a total capacity of 1,400 MW. Steam was supplied at a pressure of 2,500Psi and a temperature of 460degC. One unit was completed in 1967, another in 1968, and the remaining two in 1969. Units 3+4 had fabric filters fitted in the 1980s and this reduced load to 320 MW each. Units 1 and 2 were relegated to emergency use from 1992.
Munmorah used salt water from Lake Munmorah for condenser cooling. The coal for Munmorah came from two local underground mines, and Vales Point power station. It was delivered by conveyor belt.
In September 2007, the New South Wales State Government announced the commencement of a trial of 'clean coal' technology at Munmorah Power Station. The A$5 million trial by the CSIRO and Delta Electricity is the first part of a larger A$150 million trial jointly funded by the coal companies.[1]
On 15 October 2007, 15 Greenpeace activists entered the power station property and switched off one of the conveyor belts as a protest against the climate change policies of the Liberal Party of Australia and Australian Labor Party in the run up to the 2007 federal election.[2]
As at 2012, Carbon Monitoring for Action estimates this power station emits 4.246 million tonnes of greenhouse gases each year as a result of burning coal.[3]
Delta Electricity announced via media statement on the 3rd of July 2012 the closure of Munmorah power station after 45 years of operation due to decreasing energy demand. Units 3 & 4 had been maintained on standby but have not been in production since August 2010. (http://www.businessspectator.com.au/bs.nsf/Article/Delta-Electricity-closes-Munmorah-power-station-pd20120703-VU8HQ?opendocument&src=rss)Munmorah was disconnected from the grid in May 2014 and completely de-commissioned. Plans are underway to demolish the station and it's out buildings and sell off the 500 acres of surrounding land for housing.
See also[edit]
- Lake Munmorah
- Eraring power station
- Vales Point power station
- Colongra Gas Generation Plant
- Delta Electricity - Government-owned corporation that is the holding company for Munmorah Power Station
- ^ Wilkinson, Marian (27 September 2007). "NSW trial for clean power from coal". The Sydney Morning Herald. Retrieved 28 September 2007.
- ^ Welch, Dylan (15 November 2007). "Activists seize coal plant". The Sydney Morning Herald. Retrieved 15 November 2007.
- ^ "Plant overview: Munmorah". Carbon Monitoring for Action. Center for Global Development. 2007. Retrieved 30 January 2012.
External links[edit]
- Delta Electricity page on Munmorah


text:
Welcome to Nutbourne Vineyards.
Part of the new renaissance in English Wine, Nutbourne is a family run boutique wine producer making award winning Still and Sparkling wines in the heart of West Sussex.
All our wines are made from grapes grown on the estate and every part of the winemaking process takes place on site in our state of the art winery.
Nutbourne is a beautiful place to visit and we encourage members of the public or trade customers to come to the vineyard. Our ancient windmill tasting room is open throughout the summer months and at other times by appointment.
Nutbourne wines are sold throughout the South East by wine merchants, restaurants and hotels. We also supply selected restaurants and major Special Events in London, and private customers everywhere. Please contact us for more information.
Nutbourne Vineyards are open to visitors from May to October, Tuesday to Friday 2pm-5pm and Saturdays 11am-5pm.


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Susan Marie Kansier
Las Vegas, NV
Basic information on Susan Marie Kansier, Las Vegas NV. Find Susan Marie Kansier's age, gender, possible aliases, associates and professional status.
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Zodiac SignAries
StatusManager, Information Systems at UnitedHealth Group Inc.
StatusManager, Information Systems at UnitedHealth Group Inc.
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The superiority of 'Smaug'
Making a successful sequel to a box office blockbuster film is really quite like squaring off with a dragon: It's an unenviable task that becomes more difficult the larger the dragon. Yet
some sequels of big first films were also some of the best, ever, and obviously better than their predecessors, "The Empire Strikes Back," "The Dark Knight" and "The Godfather: Part II," among them.
Director Peter Jackson's "The Hobbit: The Desolation of Smaug" faces the double challenge of not only following "The Hobbit: An Unexpected Journey," but the two prequel films to Jackson's "Lord of the Rings" (LOTR) trilogy will face endless comparisons to his earlier Middle-earth works.
Middle-earth fans take comfort: "Smaug" is much, much better than the film it follows. It does not have to deal with introducing armies of characters or explaining the motivations behind the first important quest. Instead, "Smaug" is brisk and action-packed for most of its nearly three-hour running time, with the characters effectively running through most of that time.
Unlike Jackson's LOTR trilogy, where each film is based on one of the three books comprising J.R. Tolkien's fantasy classic trilogy, "Smaug" is one of three movies adapting Tolkien's first book, 1937's "The Hobbit, or There and Back Again." Instead of having to condense and delete material, screenwriters Jackson, Fran Walsh, Philippa Boyens and Guillermo del Toro had to add material and expand the book's world to fit three movies.
Coherent, rousing
"Smaug" shows that such a process can produce coherent, rousing movie-making and still stay true to the source material. It's a monster of an undertaking, one managed by Jackson and his own fellowship (including LOTR composer Howard Shore, cinematographer Andrew Lesnie and world builders Weta Workshop).
Set 60 years before the events of LOTR, "Smaug" finds the characters—Hobbit Bilbo Baggins (Martin Freeman), wizard Gandalf the Grey (Ian McKellen) and the 13 Dwarves, led by Thorin Oakenshield (Richard Armitage)—barely getting away from pursuing orcs and wargs. Unlike the Bilbo-centric "Journey," they have to split up, the movie splintering into several separate threads.
Bilbo and the Dwarves encounter spiders and Elves, including the lady warrior Tauriel (a new creation, played by Evangeline Lilly of "Lost") and the arrogant archer Legolas (still played by Orlando Bloom). The company passes through Laketown, in the shadow of their ultimate destination—the Lonely Mountain—where a man named Bard (Luke Evans) speaks of a prophecy that could destroy the town. All this leads to the film's central conflict: The company versus the dragon Smaug.
Freeman gets less screen time here but is fun to watch as Bilbo displays newfound determination. It is Armitage who gets the dramatic moments, effectively conflicted as a king without a crown. In this massively CGI-empowered film, Jackson has continued to revel in the visual vocabulary of
Middle-earth. What a world he has created, one that displays technology's power to transform cinema with every subsequent release.
But the film's masterpiece is Smaug himself. Voiced and motion-captured by "Sherlock's" Benedict Cumberbatch, Smaug may be the most impressive CGI creature ever rendered. Cumberbatch is perfect, as his booming baritone drips with casual terror and the tone of a predator playing with prey.
Come for the Hobbit, stay for the dragon. After watching this sequel, you will be counting the 12 long months until that final film, "The Hobbit: There and Back Again."
"The Desolation of Smaug" outshines its predecessor by a Middle-earth mile—it reminds us this prequel trilogy can be every bit as magical as the three LOTR films.
Warner Bros.' "The Hobbit: The Desolation of Smaug" opens in theaters Wednesday.
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May 22, 2015
DALLAS (May 22, 2013)--A chandelier by glass artist Dale Chihuly that once belonged to former Central Texas tycoon R. Allen Stanford was sold at auction Wednesday for $158,500.
The money will help compensate victims of Stanford's Ponzi scheme.
The 7-foot tall, 6-foot wide chandelier of cascading blue glass was sold Wednesday by Dallas-based Heritage Auctions and was expected to fetch more than $60,000.
Stanford was convicted last year on 13 fraud-related counts and sentenced to 110 years in prison.
The chandelier was offered through the federal court-appointed receivership overseeing the sale of assets previously owned by Stanford.
A 42-foot-long sculpture by Terence Main called "Terrestrial Tale," was also put on auction, but did not sell.
Stanford's assets have been sold at several auctions over the last few years.
Stanford is a Mexia native, Baylor University graduate and one-time Waco businessman.
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Mississippi State News
Local news for Mississippi State, MS continually updated from thousands of sources on the web.
Arkansas' Andrew Benintendi named SEC player of the year
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Breaking down Ole Miss' 5-run, 9th-inning comeback against Mississippi State
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Mort Künstler
|This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (May 2014)
Mort Künstler (born 28 August 1931) is an American artist known for his illustrative paintings of the American Civil War. His works are primarily sold as mass-produced printed reproductions.[1] He is also known for earlier commercial illustration before turning to Civil War themes in the early 1980s, a body of work that dealt with America's national story: from portraits of prehistoric American life to the odyssey of the space shuttle. His work has also been published in illustrated books and magazines and used by advertising agencies.
Künstler studied art at Brooklyn College, U.C.L.A. and Pratt Institute. After graduating he worked as a freelance artist in New York, where he received assignments from book and magazine publishers. In 1953, he supplied painted covers for several Classics Illustrated titles, including Pitcairn's Island and A Study in Scarlet.[2] He drew covers and other art for paperback books and men's adventure magazines. Künstler completed at least three cover illustrations and two inside illustrations every month, for MagazineManagement alone. During this time he published under at least two pen names, Martin Kay and Emmett Kaye ('plays' on his initials of "M" and "K"). Künstler said, "The editors didn't want it to look like one person was doing all the art."[citation needed] He also did art for Aurora model kit boxes, such as the Raising the Flag on Iwo Jima kit. He used the alias "Mutz" to draw back covers for issues of Mad Magazine,[3] and did posters for movies such as the original The Poseidon Adventure and the original The Taking of Pelham One Two Three.
In 1982, a commission from CBS-TV to do a painting for the 3-part mini-series The Blue and the Gray (televised November 1982) directed Mr. Künstler's interest towards the Civil War. Although the research was painstaking, he devoted much time to making sure that his painting The High Water Mark was meticulously correct. The painting was unveiled at the Gettysburg National Military Park Museum on July 2, 1988 in celebration of the 125th anniversary of the battle.
In 1992 the U.S. Postal Service commissioned Mr. Künstler to do a painting of the Buffalo Soldiers. The stamp was issued on April 22, 1994, in Dallas, Texas.
In Virginia, Governor James Gilmore officially declared a "Mort Künstler Day" in 1999, and in 2000, Governor Gilmore officially opened an exhibition at the Museum of the Confederacy in Richmond called The Confederate Spirit: The Paintings of Mort Künstler, which was the first one-man exhibition of a contemporary artist ever held at the museum. Later that year, a book by the same name was published by Rutledge Hill Press with a narrative by James I. Robertson, Jr. In a similar ceremony north of the Mason–Dixon line in Ohio, Mr. Künstler was selected as the Official Artist of the Ohio State Bicentennial, and his painting of General John Hunt Morgan's raid through Ohio was featured in a long-term exhibit at the Cincinnati Museum Center.
In 2001, Mr. Künstler was named the official artist for the motion picture Gods and Generals, and in 2002 Greenwich Workshop Press published his newest book: Gods and Generals: The Paintings of Mort Künstler. He also served as a consultant for the heralded Ron Maxwell motion picture, Gods and Generals, and his art publisher, American Spirit Publishing, released a series of historical Civil War limited edition prints of key historical events on which the motion picture was based. In 2002, Mr. Künstler became the first artist to be honored by a six-month one-man exhibition at the new National Civil War Museum in Harrisburg, Pennsylvania. In 2003, he received the Jefferson Davis Southern Heritage Award from the Military Order of the Stars and Bars - composed of descendants of the Southern officer corps - which followed his 2001 receipt of the Henry Timrod Southern Culture Award by the M.O.S.B.
Mr. Künstler has also been named as an Official Artist for the H.L. Hunley, and unveiled a new painting of the H.L. Hunley during ceremonies in Charleston, South Carolina on April 17–18, 2004. He has also been commissioned to design and furnish all the artwork for the Middletown, Ohio Veterans Memorial, which was unveiled on July 4, 2004.
In 2010 the Nassau County Museum of Art held their third exhibit of Künstler's Civil War paintings in commemoration of the 150th anniversary of the Civil War. For Us the Living - The Civil War in Paintings by Mort Künstler consisted of approximately 50 paintings accompanied by a selection of documentary objects. Visitors to a Künstler exhibition gained an inside look into the artist's creative process through a display of his sketches, drawings, and preliminary studies.
Mr. Künstler was commissioned to paint an accurate depiction of Washington crossing the Delaware. Washington's Crossing was unveiled at the New-York Historical Society on December 26, 2011 - the 235th anniversary of the actual event.
In recognition of the 150th anniversary of the Civil War, a collection of over thirty original Civil War paintings by Künstler have been on exhibit at various museums. This traveling exhibit started in February 2012 at the VMI Museum in Lexington, Virginia and continued on to the Virginia Museum of the Civil War at New Market Battlefield State Historic Park and the South Carolina State Museum in Columbia, South Carolina. During 2013 the Reading Public Museum in Reading, Pennsylvania will host the exhibit, followed by the North Carolina Museum of History in Raleigh, North Carolina. The traveling exhibit will conclude at the Washington County Museum of Fine Arts in Hagerstown, Maryland in 2014.
On September 13, 2012, the U. S. National Archives in Washington, DC hosted "An Evening with Mort Künstler." Mr. Künstler discussed pivotal moments in his career with Laurie Norton Moffat, Executive Director of the Norman Rockwell Museum, accompanied by a slide show of his works.
Mr. Künstler will be the sixth artist honored by the Booth Western Art Museum of Cartersville, Georgia with their Lifetime Achievement Award on February 15, 2014. He will join Howard Terpning, G. Harvey, Ken Riley, Fred Fellow, and Glenna Goodacre as the only honorees in the history of the award.
Künstler's artwork features dramatic interpretations of American historical events, namely, the American Civil War. The majority of Künstler paintings are done in oil on canvas. They are sold as mass-produced reproductions sold at print shops and through the internet.
Over the years (since the late 1990s and/or early 2000s), the Postal Commemorative Society [PCS] has offered a Civil War commemorative envelope set known as the "Philatelic History of the Civil War featuring artwork by MKünstler." The 100 envelopes in this collection are cacheted [cachet -- kă / shā : a commemorative illustration on an envelope or post card created by an individual or company] with Künstler's Civil War artwork (in part/detail and whole); include Civil War related commemorative postage stamps; and, are postmarked on an anniversary date of the event commemorated on the envelope. The envelopes and accompanying "Fact Cards" are available only through a 'subscription service' at the rate of four envelopes/cards per month. Though recent advertising literature mentions the 150th anniversary of the Civil War, the collection itself is not a sesquicentennial commemorative [years of postmarks found in one completed collection are 1996 and 2005 through 2013].
- Images of the Civil War: the Paintings of Mort Künstler (1992), ISBN 978-0-517-07356-8
- Gettysburg: The Paintings of Mort Künstler (Text by James M. McPherson) (1993), ISBN 1-878685-79-1
- Jackson & Lee: Legends in Gray (1995), ISBN 978-1-55853-333-2
- Mort Künstler's Old West. Cowboys. (1998), ISBN 978-1-55853-588-6
- Mort Künstler's Old West. Indians. (1998), ISBN 978-1-55853-589-3
- Gods and Generals: the Paintings of Mort Künstler (2002), ISBN 978-0-86713-084-3
- The Civil War Paintings of Mort Künstler (2006), ISBN 978-1-58182-556-5
- For Us the Living: The Civil War in Paintings and Eyewitness Accounts (2010), ISBN 978-1-4027-7034-0
Museums and institutions – permanent collections (list incomplete)[edit]
- California: San Mateo County Historical Museum, San Mateo; San Joaquin County Historical Museum, Lodi; California State Railroad Museum, Sacramento; Lowie Museum of Anthropology, Berkeley; California Museum of Science and Technology, Los Angeles; Ronald Reagan Library, Simi Valley.
- Canada: The Glenbow Museum, Calgary.
- Colorado: The Air Force Museum, Boulder.
- Delaware: The Hagley Museum, Wilmington.
- Florida: Daytona Beach Museum of Arts and Sciences, Daytona Beach.
- Georgia: Booth Western Art Museum, Cartersville.
- Germany: Erstes Imaginares Museum, Wasserburg.
- Indiana: Midwest Museum of American Art, Elkhart.
- Maryland: U.S. Naval Academy Museum, Annapolis; Washington County Museum of Fine Arts, Hagerstown.
- Missouri: Dunnegan Gallery of Art, Bolivar.
- New Jersey: Hudson County Court House, Jersey City.
- New York: National Art Museum of Sport, Madison Square Garden, New York; Vanderbilt Museum, Centerport; Old Orchard Museum, Sagamore Hill National Historic Site, Oyster Bay; Museum of American Illustration, New York; Nassau County Museum of Art, Roslyn; Federal Hall, National Parks Foundation, New York; Mark Twain Center, Elmira; Hillwood Gallery, C.W. Post Campus, Long Island University, Greenvale; Museum of American Immigration at the Statue of Liberty and Ellis Island, New York; United States Merchant Marine Academy Museum, Kings Point; Bayville Museum, Bayville.
- North Carolina: Alamance County Historical Museum, Burlington; North Caroliniana Society, Chapel Hill; North Carolina Museum of History, Raleigh.
- Oregon: Favell Museum, Klamath Falls.
- Pennsylvania: United States Army War College, Carlisle Barracks; The National Civil War Museum, Harrisburg.
- South Carolina: Ft. Sumter National Monument Museum, Charleston; Charleston Museum, Charleston; Old Exchange and Provost Dungeon, Charleston.
- South Dakota: Buechel Memorial Lakota Museum, St. Francis, Rosebud Sioux Reservation.
- Tennessee: The Hermitage, Nashville; Tennessee State Museum, Nashville.
- Texas: Diamond M Museum, Snyder.
- Virginia: Museum of the Confederacy, Richmond.
- Washington, DC: U.S. Navy Memorial Museum; U.S. Marine Corps Museum; NASA; U.S. Secret Service; National Guard Bureau, Pentagon; Museum of American History, Smithsonian Institution; U.S. House of Representatives; U.S. Senate.
One Man Exhibitions
- 1977 Daytona Beach Museum of Arts and Sciences, Daytona Beach, Florida
- 1977 Hammer Galleries, New York
- 1978 Old Orchard Museum, Sagamore Hill National Historic Site, Oyster Bay, New York
- 1979 Hammer Galleries, New York
- 1979 U.S. Navy Memorial Museum, Washington, D.C.
- 1981 Hammer Galleries, New York
- 1981 Pittsburgh Center for the Arts, Pittsburgh, Pennsylvania
- 1982 Hammer Galleries, New York
- 1982 Hillwood Gallery, C.W. Post Campus, Long Island University, Greenvale, New York
- 1982 U.S. Navy Memorial Museum, Washington, D.C.
- 1983 Saks Galleries, Denver, Colorado
- 1984 Old Orchard Museum, Sagamore Hill National Historic Site, Oyster Bay, New York
- 1985 Hammer Galleries, New York
- 1986 Hammer Galleries, New York
- 1986 Washington County Museum of Fine Arts, Hagerstown, Maryland
- 1987 Conacher Galleries, San Francisco. California
- 1989 Museum of Westward Expansion, Jefferson National Expansion Memorial, St. Louis, Missouri
- 1989 Hammer Galleries, New York
- 1991 Dunnegan Gallery of Art, Bolivar, Missouri
- 1992 Gettysburg National Military Park, Gettysburg, Pennsylvania
- 1992 Hall of Valor Museum, New Market Battlefield, Virginia
- 1992 Hammer Galleries, New York
- 1993 Gettysburg National Military Park, Gettysburg, Pennsylvania
- 1993 Hammer Galleries, New York
- 1995 Hammer Galleries, New York
- 1995 North Carolina Museum of History, Raleigh, North Carolina
- 1998 Nassau County Museum of Art, Roslyn, New York
- 1998 Hammer Galleries, New York
- 1999 Leon Loard Gallery, Montgomery, Alabama
- 2000 Museum of the Confederacy, Richmond, Virginia
- 2000 Hammer Galleries, New York
- 2002 The National Civil War Museum, Harrisburg, Pennsylvania
- 2003 Hammer Galleries, New York
- 2004 Hammer Galleries, New York
- 2005 Booth Western Art Museum, Cartersville, Georgia
- 2006 Nassau County Museum of Art, Roslyn, New York
- 2006 Hammer Galleries, New York
- 2010 Nassau County Museum of Art, Roslyn, New York – September 25, through January 9, 2011
Major Commissions (List Incomplete) American Cyanamid, Crum & Forster, Exxon, F&M Bank-Winchester, General Electric, Hesston Corporation, Landmark Bancshares Corporation, National Distillers, New York Bank for Savings, Rockwell International, Texaco, Twentieth Century Fox, U.S. Army War College, U.S. Bank and Trust Company, U.S. Steel, Warner Brothers, Westvaco.
Participation in Museum Exhibitions (List Incomplete)
- Boston Museum of Science, Boston, Massachusetts
- Colorado History Museum, Denver, Colorado
- Daytona Beach Museum of Arts and Sciences, Florida
- Gettysburg National Military Park, Gettysburg, Pennsylvania
- Hall of Valor Museum, New Market Battlefield, Virginia
- Mint Museum of Art, Charlotte, North Carolina
- Museum of Westward Expansion, Jefferson National Expansion Memorial, St. Louis, Missouri
- New York Hall of Science, Queens, New York
- New York Historical Society Museum, New York, New York
- North Carolina Museum of History, Raleigh, North Carolina
- Oakland Museum, Oakland, California
- Old Orchard Museum, Sagamore Hill National Historic Site, Oyster Bay, New York
- Sewall Art Gallery, Rice University, Houston, Texas
- Steamtown National Historic Site, Scranton, Pennsylvania
- Tennessee State Museum, Nashville, Tennessee
- Union Carbide Gallery, New York, New York
- U.S. Customs House Gallery, New York, New York
- U.S. Navy Memorial Museum, Washington, D.C.
- Washington County Museum of Fine Arts, Hagerstown, Maryland
- Woodbridge Museum, Woodbridge, New Jersey
- pag 235-236 The American Spirit, Art by Mort Künstler, text by Henry Steel Commanger
- pag 5-6, Heritage Auction Galleries, catalogue May 2010
- pag 5-10 Franklin Hill Perrell, The American Spirit, catalogue 2006
Other sources[edit]
- Mort Künstler feted as painting's unveiled
- Crossing the Delaware, More Accurately
- Mort Künstler at American Art Archives
- Interview at the Pritzker Military Museum & Library
- Mort Künstler – The American Spirit, essay by Franklin Hill Perrell
- Applying Brushstrokes to the Civil War, NYTimes.com
External links[edit]


text:
Newly acquired Houston Texans safety Ed Reed underwent arthroscopic surgery last week to repair a small labral tear in his hip, according to a report from the Houston Chronicle. Reed previously had reconstructive surgery three years ago to replace a torn labrum and also about 6 to 7 inches from his iliotibial band. He ended up missing the first seven weeks of the 2010 season. This time around it's not as serious, and he's expected to be ready for training camp in late July. NFL.com's Chris Wesseling writes: ' Considering Reed's history, that timetable seems a bit on the optimistic side. We wonder if the injury also played a role in the Baltimore Ravens' willingness to let Reed walk rather than matching the Texans' offer. If there's a silver lining to the surgery, it's that promising second-rounder D.J. Swearinger will pick up key reps with the starters throughout the offseason program. '
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