Mechanical properties of rubber vulcanizates containing Ethylene Propylene Diene Rubber waste at different types of vulcanization system

Abstract

Ethylene Propylene Diene Rubber (EPDM) waste filled Natural Rubber (NR) that cured by using conventional vulcanization (CV), semi-efficient vulcanization (semi-EV) and efficient vulcanization (EV) system was successfully compounded by an internal mixer. The ratio of sulphur and accelerator is different for each vulcanization system, that finally affect the vulcanizate properties due to the different structural features of an accelerated sulphur vulcanizate of NR. 60 phr of pulverized EPDM waste was incorporated into 40 phr of NR in each vulcanization system. Studies about the usage of abundantly available EPDM waste as a potential filler is essential towards green environment and minimize landfill area in future. It is found that the cured rubber with CV system has the best properties due to high degree of crosslinking of polysulphidic crosslink. Tensile properties and abrasion resistance of the rubber compound indicated its mechanical properties were investigated. Density and hardness test were also done to study its physical properties. For tensile strength, CV system has 14% increment from EV system because of a stress-relieving mechanism that exhibited in this vulcanization system. As for tensile modulus, M500 for CV system shown 29% increment than EV system. As a result of the decreased chain flexibility caused by the increased crosslinking density in the CV system, the elongation at break of the vulcanizate is the lowest (174 mm) when compared to the EV system (336 mm). CV system shown highest Abrasion resistance index (ARI) i.e. 1820%. This indicate that very small amount of mass loss obtained for the CV cured rubber during the testing. CV system gives highest density and hardness values i.e. 1.0747 g/cm3 and 52.5 Shore A, respectively. Thus, the results indicated that NR containing EPDM waste cured by CV system is able to be utilized in the development of rubber compound with a compromise property.