Simultaneous Enhancement of Mechanical and Dynamic Mechanical Properties of Natural Rubber/Recycled Ethylene-Propylene-Diene Rubber Blends by Electron Beam Irradiation

Abstract

Mechanical and dynamic mechanical properties of natural rubber/recycled ethylene-propylene-diene rubber (NR/R-EPDM) blends were simultanoeusly enhanced by electron beam (EB) irradiation. The cross-linking promoter, trimethylolpropane triacrylate (TMPTA), was also introduced into the blends to induce the cross-linking. By applying EB irradiation, the tensile modulus, hardness, swelling, cross-link density, and storage modulus increased with increase in the irradiation dose; an irradiation dose of 50 kGy was efficient to gain optimum tensile strength. The formation of irradiation-induced cross-links after EB irradiation is a major concern for the enhancement of mechanical, swelling resistance, and dynamic mechanical properties of the blends.

Keywords:

• Dynamic mechanical analysis
• Electron beam irradiation
• Mechanical properties
• Natural rubber
• Recycled ethylene-propylene-diene rubber

Notes

SMR L = standard Malaysian rubber L, R-EPDM = recycled ethylene-propylene-diene rubber, ZnO = zinc oxide, CBS = N-cyclohexyl-benzothiazyl-sulfenamide, TMPTA = trimethylolpropane triacrylate.

M _L  = elastic minimum torque (dN · m), M _H  = elastic maximum torque (dN · m), M _H – M _L  = torque difference (dN · m), ts ₂  = scorch time (min), tc ₉₀  = curing time (min), CRI = cure rate index (CRI).

M100 = stress at 100% elongation, M300 = stress at 300% elongation.