Effects of alkanolamide and epoxidation in natural rubber and epoxidized natural rubbers compounds

The effects of alkanolamide (ALK) loading and epoxidation on cure characteristics, crosslink density and mechanical properties of unfilled natural rubber (NR) and epoxidized natural rubbers (ENRs) compounds have been investigated. The NR, ENR-25 and ENR-50 having 0, 25 and 50 mol % of epoxidation were utilised. It was found that the cure and scorch times decreased with increasing ALK loading. At similar ALK loading, ENR-50 possessed the lowest scorch and cure times followed by ENR-25 and NR compounds. Compared to the control compound (without ALK), the mechanical properties of the three rubbers have been enhanced by the ALK addition. However at a similar ALK loading, the mechanical properties viz. tensile modulus, tensile strength and hardness of ENR-50 vulcanisates were the highest followed by ENR-25 and NR vulcanisates. The superiority in mechanical properties of ENR-50 was due to its highest degree of crosslink density.