Effect of co‐agents on adhesion between peroxide cured ethylene–propylene–diene monomer and thermoplastics in two‐component injection molding

Abstract

Two-component (2K) injection-molded products combining ethylene-propylene-diene monomer (EPDM) with polar or nonpolar thermoplastics require strong interfacial bonding. To optimize the adhesion, co-agents trimethylolpropane trimethacrylate (TMPT) and triallyl cyanurate (TAC) are compared and concentrations were varied between 0 and 12 parts per hundred rubber (phr). Changes in material compatibility were characterized by contact angle measurements at high temperature, the adhesion was evaluated by tensile testing, and physicomechanical properties of the EPDM bulk were analyzed. Results show that with polypropylene, the adhesion increases to an optimum (3 phr TAC or 6 phr TMPT) independent of the co-agent type, while for polyethylene only TAC (1.5 phr) effectively boosts adhesion. It is surmised that these optimal concentrations promote crosslinking reactions at the interface. For polycarbonate and acrylonitrile-butadiene-styrene, increasing TAC concentration causes higher adhesion due to improved compatibility. Furthermore, physicomechanical bulk properties change significantly with co-agent concentrations, making the optimal curing composition application dependent. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48414.