A frequency sweep experiment was performed to better understand the viscoelastic properties of the materials. Figures and show the dependence of E' and tanδ on the oscillation frequency, respectively. All materials have stable viscoelastic properties in the frequency range of 0.1 -100 Hz. For all of them, the damping coefficient practically does not exceed 5%, confirming the elastic properties of the materials. In turn, the absolute values of the E' moduli again show the same trend as during the temperature sweep over the whole frequency range. Figure shows representative stress-strain curves for each material. In turn, Figs. show the parameters of strain at break, tensile modulus and tensile strength. All the mechanical parameters determined are listed in Table . As can be seen in Figure , the addition of hydroxyapatite significantly affected the deterioration of the copolymer ductility. A similar phenomenon in PBS/nHAp composites was also observed by Wenmin Guo . In Figure , it can be seen that these decreases are greater for nHAp than for µHAp. The may be due to the tendency of nanoparticles to agglomerate, resulting in disruption of continuity and weakening of the polymer structure. In turn, Figures and again show the effect of filler addition on tensile modulus and tensile strength, and here the opposite phenomenon occurs -material strengthening. Regarding the tensile strength parameter, the highest reinforcement was obtained for the sample with 20% micro-hydroxyapatite content (about 17%). In turn, the analogous composite with nano-hydroxyapatite was only strengthened by only 6%. Similarly, in the case of the tensile modulus, apatite micro-whiskers showed a greater strengthening efficiency. The results obtained are consistent with literature reports indicating the particular strengthening potential of whisker-like HAp particles . The mechanical properties (flexural modulus, stress at 3.5% of strain) of the materials subjected to static bending were also significantly improved after the addition of the filler, but no major differences were observed between the PBS/DLS/nHAp and PBS/DLS/µHAp composites (Figures ).