Non-rubber components tuning mechanical properties of natural rubber from vulcanization kinetics

Abstract

Natural rubber (NR) with complex components has superior mechanical properties to synthetic high cis-1, 4-polyisoprene. It is still a challenge to explore the reason why NR owns superior mechanical properties. In previous studies, the excellent properties of NR have been ascribed to strain-induced crystallization phenomenon. However, in this study we find non-rubber components (NRC) in NR affecting vulcanization process, which finally contributes to excellent properties of NR. Through the changes of NRC content, the mechanical properties of NR can be tuned. The differential scanning calorimeter is used to investigate vulcanization kinetics. The results show that NRC decrease the activation energy of vulcanization process, which causes higher crosslinking density and curing rate. Through additional protein verifying and mimicking the acceleration effect of NRC, mechanical properties of NR can be tuned from soft state to tough state. Therefore, NRC affecting vulcanization kinetics is another essential reason why NR owns superior mechanical properties. This work also provides more insightful understanding toward the structure-property relationship of NR.