Study On High Temperature Rapid Vulcanization System Of Natural Rubber And Its Application In Thick Walled Rubber Articles

Normally,the cure time of thick walled rubber articles need to be prolonged in order to ensure the inside of the product reach positive vulcanization because of the poor thermal conductivity of the rubber compound.The prolonged cure time not only reduces production efficiency significantly,but also increases energy consumption greatly.Therefore,it is particularly important to shorten the cure time of thick walled rubber products and to maintain or even improve their performance.The effects of TP/S,thermal conductive agents such as aluminum trioxide,carbon nanotubes and their combination on processability and properties of NR vulcanizates were systematically studied.The results showed that the substitution of accelerator TBTD and silane Si-69 with dilkyl dithiophosphate TP/S could significantly improve the reversion resistance,shorten the optimum cure time t90,and improve the cure rate natural rubber（NR）.TP/S could improve compression set hot-air aging resistance of NR vulcanizates significantly,while TP/S has little effect on mechanical properties and brittle temperature of NR,the optimal content of TP/S was 1.6～2.4 phr.The replacement of accelerator CZ with DM can further improve the reversion resistance of NR compounds,reduce the compression set of NR vulcanizates,but the t90 was extended slightly.The effect of the alumina on Mooney viscosity,scorch time and the flatness of the cure curves were not obvious.The thermal conductivity of NR was increased by 14%to 0.2 W/（m·K）when the content of alumina was 20 to 30 phr.With the increasing of the alumina content,the tensile strength and the elongation at break of NR reduced,and other mechanical properties increased slightly.The compression set of NR was improved when the content of alumina exceeds 30 phr.Carbon nanotubes（CNTs）could shorten the scorching time t10 optimum cure time t₉₀,and CNTs showed no effect on flatness of cure curves,the reversion rate was basically maintained at about 10%,4 phr CNTs could increase Mooney viscosity significantly.CNTs could significantly improve the thermal conductivity of NR vulcanizates,the thermal conductivity is 0.24 W/（m·K）with the CNTs content of 4phr,which is 38%higher than the original formulation.CNTs could improve the tear strength,modulus and hardness of NR significantly,CNTs didn’t affect the brittle temperature of NR,but could significantly increase the compression set which was up to 67%when the content of CNTs was 4 phr.The combination of CNTs and alumina could improve the thermal conductivity of NR further and reduce compression set of NR.When the TP/S content was 1.6 phr,the alumina content was 30 phr,and the CNTs content was 2 phr,the cure time of the thick walled rubber articles could be reduced by 30%.