Silane cross‐linking of PVC. II. Influence of silane type and conditions on cross‐linking by water

The cross‐linking of plasticized and unplasticized poly(vinyl chloride) (PVC) grafted with amino‐ and mercaptoalkyltrialkoxysilanes has been studied in water and in air at 20–140°C. In both media, the cross‐linking occurs faster for plasticized PVC grafted with aminosilanes; however, at temperatures above 100°C, the effect of degradation cross‐linking is apparent. For mercaptosilanes, a marked dependence of the cross‐linking rate on the silane structure was found; plasticized PVC with grafted 3‐mercaptopropyltrimethoxysilane was cross‐linked in water at 100°C after 6 h, whereas this process took 12 h for 5‐mercaptopentyltriethoxysilane. Practically no cross‐linking occurred in unplasticized PVC below Tg, whereas the rate at 100°C was comparable with that for plasticized PVC. The cross‐linking rate is affected by the chain mobility, water content, and diffusion of water into the material; a very slight dependence on the thickness of the material was found for plasticized PVC.