Charoen Nakason, Watcharin Sainumsai, Azizon Kaesaman, and Pairote Klinpituksa

pp. 63 - 73

Abstract

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.