Component interactions and properties of crosslinked vinyl systems

Compositions based on poly(vinylchloride) (PVC) containing diisodecyl phthalate (DIDP) or trioctyl trimellitate (TOTM) plasticizers and, in several cases, also containing chlorinated polyethylene (CPE) as property modifier were cross‐linked by γ irradiation, using a trifunctional acrylic cross‐linking agent. Cross‐linking effectiveness was analyzed by solvent swelling data, and the effects of irradiation up to dosages of about 10 Mrad on the mechanical properties of the systems were recorded. The interaction potential of components used in these systems was determined by recently developed methods of inverse gas chromatography (IGC). These classify PVC and CPE as electron acceptors and the plasticizers as donors. Expectedly, increased moduli and decreased elongational properties follow exposure to γ‐rays. The plasticizers reduce the effectiveness of cross‐linking, the magnitude of the reduction being related to the degree of acid‐base interaction between PVC and plasticizing fluids. Interference with cross‐linking mechanisms thus is a function of the solvent power of the plasticizers. CPE competes with PVC for plasticizer so that for given quantities of DIDP or TOTM, the fraction available to solubilize the host polymer is reduced. In compounds with CPE, therefore, the cross‐linking effectiveness of irradiation is raised, consistent with the acid‐base balance of Interactions, as given by the IGC results. Twin yield points have been observed in the stress‐strain curves of compounds containing CPE. It is postulated that distinct, interpenetrating cross‐link networks are formed when these polymers are subjected to γ irradiation.