Effect of Thermal Cycles on Physical and Tensile Properties of Newly Modified NR/EPDM Blend

Abstract

Natural rubber/ethylene propylene diene monomer (NR/EPDM) blend is a well-known engineering material used in automotive as well as manufacturing components. It combines the superior physical and mechanical properties with excellent resistance to weathering except for heterogeneous dispersion of EPDM domains in NR which could be deleterious to mechanical properties especially under thermal effect. This study focuses on the effect of thermal cycles on tensile properties of newly modified NR/EPDM blend. The blends were prepared via melt blending using a Haake internal mixer at a temperature of 110 ºC, rotor speed of 40 rpm and mixed for 7 minutes and subsequently cured using a hot press machine at 150 ºC. The blends were then exposed to two different temperatures of 60ºC and 120 ºC and cooled down to room temperature alternately for 10 minutes and repeated for 0, 5, 35, 70, and 150 times. The tensile behavior of NR/EPDM blends illustrates consistent value at 60 ºC thermal cycles and changed drastically down to ~70% at 120ºC. It experienced molecular degradation due to absorption of thermal energy during the thermal cycles hence decreasing the crystallinity via transformation from rubbery to glassy behavior as supported by scanning electron microscopy and X-ray diffraction analyses.