Aminosilane crosslinking of plasticised poly(vinylchloride) : processing, properties and characterization
The extensive use of Poly(vinyl chloride) (PVC) is partly due to the modification of properties which is possible by the addition of plasticizer. Although plasticized PVC is used at temperatures well above Tg, the properties are favourable and the material has a rubberlike behaviour. This is generally considered to be due to the presence of a physical network consisting of small crystallites. However, its service range is limited by its thermoplastic nature. At temperatures above 100 C it has a tendency to flow and to have a reduced mechanical strength. One way to increase the maximum temperature of plasticized PVC is to introduce a permanent chemical network. The reaction of plasticized PVC with [N-(2-amino ethyl)-3-aminopropyl trimethoxy silane] yielded si lane-grafted PVC that was crosslinked by a hydrolitic mechanism. The grafting of the aminosilane was carried out during processing in both a roll mill followed by compression moulding and in a single screw extruder. A controlled reaction was observed when a tin stabilizer was selected. It was found that other thermal stabilizers accelerate the grafting reaction, but destabilize the polymer. The crosslinking of the grafted PVC has been studied in water at different temperatures. The crosslinking occurred faster at high temperatures and was diffusion controlled.....