Cure and physical properties of natural rubber and epoxidized natural rubber compounds using various types of accelerators

Cure characteristics and tear properties of epoxidized natural rubber (ENR-33) and natural rubber were studied. Three types of accelerators, namely 2-mercaptobenzothiazole (MBT), 2-morpholinothiobenzothiazole (MBS) and N-tert-butyl-2-benzothiazyl sulphenamide (TBBS) were used in this work. The conventional valcanization (CV) system was used. Cure characteristics were determined using a Monsanto Oscillating Disk Rheometer (ODR 2000) at 150ºC. Also, a systematic study of tear strength was carried out before and after ageing at 70ºC for 72 h. A Hounsfield tensometer (Model H10KS) operating at 500 mm/min was used to determine the tear strength using standard angle test pieces. The results indicated that scorch time and cure time of natural rubber are greater than those of ENR-33 compounds. However, the contrary was observed for the minimum and maximum torques and the torque differences. The observation is attributed to the activation of a double bond by the adjacent epoxide group in ENR-33. Furthermore, we found that the change in tear strength of aged ENR sample was greater than that of NR vulcanizates