Abstract
The understanding of thermo-mechanical degradation of poly(vinyl alcohol)s (PVAs) during thermoplastic processing is insufficient and deserves more attention due to the high potential of this technology. In this contribution the experimental data are provided revealing the effect of melt processing on properties of PVAs differing in degree of hydrolysis. NMR, FTIR, titration and size exclusion chromatography were used to demonstrate the effect of extrusion time on average length of the respective blocks and mutual ratio of vinyl acetate–vinyl alcohol monomer units, content of double bonds, amount of liberated acetic acid and molecular weight distribution. Partially hydrolysed PVAs are less resistant to degradation than fully hydrolysed PVAs, which primarily corresponds to the presence of vinyl acetate groups. Other factors, like microstructural heterogeneities and the presence of double bonds, may significantly influence the stability of partially hydrolysed samples. Addition of benzoic acid was used to prove that the mechanism of degradation involves the acidic catalysis by acetic acid liberated from vinyl acetate units.
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