product is available in different solvents as 20% solutions. Nomenclature Silicon-nitrogen compounds with alternating silicon- ("sila") and nitrogen atoms ("aza") are designated as silazanes. Simple examples of silazanes are disilazane H3Si–NH–SiH3 and hexamethyldisilazane (H3C) 3Si–NH–Si(CH3)3. If only one silicon atom is bound to the nitrogen atom, the materials are known as silylamines or aminosilanes (for example triethylsilylamine (H5C2)3Si–NH2). If three silicon atoms are bound to each nitrogen atom, the materials are called silsesquiazanes. Small ring-shaped molecules with a basic network of Si-N are named cyclosilazanes (for example cyclotrisilazane [H2Si–NH] 3). In contrast to this, polysilazanes are silazane polymers consisting of both large chains and rings showing a range of molecular masses. A polymer with the general formula (CH3)3Si–NH–[(CH3)2Si-NH] n–Si(CH3)3 is designated as poly(dimethylsilazane). According to the IUPAC rules for the designation of linear organic polymers, the compound would actually be named poly[aza(dimethylsilylene)], and according to the preliminary rules for inorganic macromolecules catena-poly[(dimethylsilicon)-m-aza]. The labels normally used to describe the structure of silicones (M, D, T, and Q) are rarely employed for polysilazanes. Characteristics Polysilazanes are colorless to pale yellow liquids or solid materials. Conditional of manufacturing, the liquids often contain dissolved ammonia that can be detected by smell. The average molecular weight can range from a few thousand to approximately 100,000 g/mol while the density normally lies around 1 g/cm3. The state of aggregation and the viscosity are both dependent on the molecular mass and the molecular macrostructure. Solid polysilazanes are produced by chemical conversion of the liquid materials (crosslinking of smaller molecules). The solid materials can be fusible or unmeltable and can be soluble or insoluble in organic solvents. As a rule, polysilazane solids behave as thermosetting polymers, but in some cases, thermoplastic processing is possible. After the synthesis, an aging process frequently takes place in which dissolved ammonia plays an important role. The R3Si–NH2 groups resulting from the ammonolysis reaction form silazane units by splitting off ammonia. If ammonia can not escape, the silazane units can be split again into R3Si–NH2 groups. Therefore, frequent venting of ammonia can lead to an increase in molecular mass. Also, functional groups that are not bound directly into the polymer backbone can react under suitable conditions (for example Si–H with N–H groups) and increase crosslinking of the rings and chains. An increase in molecular weight can also be observed during storage at higher temperatures or in sunlight. With contact to water or