Effect of chemical blowing agent on cell structure and mechanical properties of EPDM foam, and peel strength and thermal conductivity of wood/NR composite–EPDM foam laminates

Melt-laminates of wood/natural rubber (wood/NR) composite and ethylene-propylene diene rubber (EPDM) foam were prepared by compression molding technique. Two different forms of 4,4′oxybis(benzenesulfonylhydrazide) (OBSH) blowing agent were used; pure OBSH (designated as OBSH) and ethylene-propylene bound OBSH (designated as EPR–b-OBSH). The effect of the OBSH concentration on the cell structures and mechanical properties of EPDM foam, and the peel strength and thermal conductivity of wood/NR composite–foamed EPDM laminates was examined. It was found that the EPR–b-OBSH gave EPDM foam with greater number of cell structures, higher porosities and resistances to water penetration on the foam surface. However, the EPDM with EPR–b-OBSH agent had worse elastic recovery as compared to that with OBSH due to deformation of cell structures after prolonged compression loading. The recommended concentrations for EPR–b-OBSH and OBSH blowing agents were 3.0 and 5.0 phr, respectively, for the optimum interfacial adhesion and low thermal conductivity.