CROSS-LINKING IN BLENDS OF NITRILE RUBBERS AND POLY(VINYL CHLORIDE)

Crosslinking of nitrile rubber (NBR) and poly(vinyl chloride) (PVC) can be accomplished separately using ethylenethiourea (ETU) with and without the presence of sulphur (S) respectively. ETU/S combination in appropriate doses brings about ready co-crosslinking of NBR and PVC in their blends. Comparative studies of the curing characteristics of some NBR-PVC blends and some important physical properties of the blend vulcanizates have been made using the test curative (ETU/S system) and a conventional curative (tetramethylthiuram disulphide (TMTD)/sulphur (S) system). The ETU/S curative system produces crosslinking effects which in some respects are comparable with, and in some other respects are even substantially better than, those produced by the conventional TMTD/S curative system, particularly with respect to consequential curing parameters and blend vulcanizate properties including morphological patterns and ageing behaviour.