Material propertiesThe effect of the addition of alkanolamide on properties of carbon black-filled natural rubber (SMR-L) compounds cured using various curing systems

The properties of carbon black (CB)-filled natural rubber (SMR-L) compounds, with and without the addition of Alkanolamide (ALK), based on various curing systems such as efficient, semi-efficient and conventional vulcanisation systems were investigated. The ALK loading was fixed at 5.0 phr. It was found that ALK gave improvements to the cure rate, torque difference, crosslink density, filler dispersion, rubber-filler interaction and reinforcing efficiency of CB. ALK also enhanced the tensile modulus, hardness, resilience, tensile strength and elongation at break of CB-filled SMR-L vulcanisates for each curing system. The degree of improvement of cure characteristics and mechanical properties depended on the level of sulphur and the ratio of accelerator to sulphur in each system. Scanning electron microscopy (SEM) proved that the CB-filled SMR-L vulcanisates with ALK for each curing system displayed a greater matrix tearing line and surface roughness due to greater rubber-filler interaction.