Polyvinyl alcohol has a melting point of 230°C and a glass transition temperature ranging from 75°C to 85°C. When heated in air to temperatures exceeding 100°C, it gradually discolors and becomes brittle. Upon heating to 160–170°C, it undergoes dehydration and etherification, resulting in a loss of solubility; decomposition begins at 200°C. At temperatures exceeding 250°C, it transforms into a polymer containing conjugated double bonds.
Polyvinyl alcohol is a water-soluble polymer that is not synthesized directly through the polymerization of monomers, but rather obtained via the hydrolysis of polyvinyl acetate. It exists as a white, odorless solid in the form of flakes, floccules, or powder. The physical properties of polyvinyl alcohol are influenced by its chemical structure, degree of alcoholysis, and degree of polymerization. Two distinct chemical structures exist within the polyvinyl alcohol molecule-namely, the 1,3-ethylene glycol structure and the 1,2-ethylene glycol structure-though the predominant form is the 1,3-ethylene glycol structure, also known as the "head-to-tail" structure.
