Cure characteristics and mechanical properties of different accelerator systems for thick rubber article

Curing thick rubber article may create temperature gradient across the thickness of the article. Therefore, this may cause in the difference of properties between the inner and outer region. Thus, the thick rubber article was divided into several regions with different type of accelerators in each layer in order to produce uniform cured thick rubber article. In this study, the effect of different accelerators on cure characteristics and mechanical properties of natural rubber vulcanizates for the thick rubber article was investigated. The types of accelerators that were selected are N-cyclohexylbenzothiazole-2-sulphenamide (CBS), zinc diethyldithiocarbamate (ZDC) and diphenylguanidine (DPG). The cure characteristics, such as scorch time and cure time were studied at temperature range of 100-140 °C. The scorch time for control vulcanizate (NR140) showed the highest value (4.5 minutes) as the sulphanamide-type of accelerators was used. The combination of different accelerators produced almost similar scorch time at lower curing temperature for other vulcanizates (NR130, NR120, NR110 and NR100). The tensile strength and hardness values of all vulcanizates were also found to have similarity as compare to control vulcanizate (NR140), regardless of the different in type of accelerators and curing temperature that was applied for each vulcanizate. These indicate that the thick rubber article is able to be cured uniformly with less variation in the mechanical properties.