Vinyl-functionalized polysiloxane as radical scavenger during the degradation of poly(vinyl chloride)

Siloxane polymer containing vinyl groups was blended with poly(vinyl chloride) (PVC) to convey plasticization and stability against decomposition, that is likely to happen during thermal processing or following exposure to the ultraviolet (UV) light. The immiscibility between silicone rubber and PVC was proved from images acquired using scanning electron microscopy (SEM), which revealed worsening of the situation at higher loading (10 wt%) of silicone polymer. The thermal degradation profiles indicated that the inclusion of silicone polymer did not affect the thermal resistance significantly between 200°C and 350°C. However, it protected the matter from intensive decomposition at higher temperatures and increased the residual weight. Fourier transform infrared spectra were collected for the blends after exposure to UV radiation for 168 h, from which the absence of appreciable dehydrochlorination or change in the nature of the material was ensured. The hampering of dehydrochlorination is expected to have proceeded by instant attack of any appearing radicals on PVC backbone onto vinyl groups of the silicone polymer and buildup of a network structure.