Thermal Degradation and Oxygen Absorption of PVC

Carbonyl and hydroxyl groups are formed as a result of dehydrochlorination and oxidation of PVC which is subjected to thermal degradation in the air. Determination of the absolute quantity of combined oxygen is impossible through investigation of infrared absorption alone, so direct microanalysis of oxygen is resorted to. Elementary analysis indicates that removal of one molecule of Cl is accompanied by elimination of about two molecules of H and addition of about 1/2 molecule of oxygen. In the case of 180-°C thermal degradation, 1725cm-1 infrared absorption and analytical value of oxygen are linearly related with each other, but absorption around 685cm-1 and analytical value of chlorine are not. Concerning a deteriorated sample, ultraviolet absorption, intrinsic viscosity, solubility to cyclohexanone, specific gravity and Xray diffraction are investigated ; specific gravity increases through thermal degradation, but no change in X-ray diffraction is observed.