ABSTRACT
Thermal degradation of PV A in the presence of oxygen can be adequately described by a two-stage decomposition scheme, with one modification. Oxidation of the unsaturated polymeric residue from dehydration reaction introduces ketone groups into the polymer chain. These groups then promote the dehydration of neighboring vinyl alcohol units producing a conjugated unsaturated ketone structure.2 The first-stage degradation products of PVA pyrolysed in air are fairly similar to those obtained in vacuum pyrolysis. In the range 260-280°C, the second-orderreaction expression satisfactorily accounts for the degradation of 80% hydrolyzed PV A up to a total weight loss of 40%. The activation energy of decomposition appears to be consistent with the value of 53.6 kcaVmol which is obtained from the thermal degradation of Polyvinyl Acetate.2
