The influence of plasticisers on the radiation crosslinking of trimethylolpropane trimethacrylate in poly(vinyl chloride)

Radiation crosslnking of poly(vinyl chloride) (PVC) was investigated with the aim of obtaining a suitable formulation for electrical-cable sheathing. Because of its high radiation sensitivity, trimethylolpropane trimethacrylate (TMPTM) was chosen as crosslinking agent. The radiation behaviour of TMPTM was studied in the presence of two different plasticisers, viz. di-isooctyl adipate (DIOA) and a trimellitate ester 'Reomol LTM' (tri-Linevol 79 trimellitate from Ciba-Geigy). Gel content was measured as a function of the dose in formulations containing various amounts of plasticisers and TMPTM. Mechanical properties of irradiated PVC which were measured include BS softness, modulus at 100% elongation, ultimate tensile strength and elongation at break. Other tests of practical importance were also carried out; they concern variation in relative density, swelling behaviour, heat deformation and volume resistivity. These results were discussed with emphasis on the role played by the plasticiser in the formation and the stability of the network. (author)