Purification of peroxide-prevulcanised natural rubber latex: Unveiling the mechanistic role of proteins and enhancing mechanical and dynamic performances

Abstract

Peroxide-based vulcanisation of natural rubber (NR) latex has attracted significant interest as a safer and cleaner alternative to the conventional sulphur-based system. In this study, NR latices both before and after enzymatic deproteinisation were vulcanised using tert-butyl hydroperoxide (t-BHP) and fructose to systematically investigate changes in allergenic protein, vulcanisation efficiency, and the mechanical and dynamic properties of the resulting vulcanisates. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that the vulcanisation process modified certain allergenic proteins. Vulcanised NR film exhibited effective crosslinking, achieving relatively high mechanical strength (15.90 MPa) and favourable dynamic mechanical performance. In contrast, deproteinised NR (DPNR) film showed markedly reduced vulcanisation efficiency, resulting in relatively low tensile strength (1.67 MPa). These findings suggest that proteins facilitate redox-mediated vulcanisation, likely acting as reducing agents that promote radical initiation and potentially participate in the formation of additional radicals and crosslinks of rubber chains through protein-derived radicals. To enhance latex purity while maintaining essential material properties, NR latex vulcanised at 60°C for 3 h was purified by repeated surfactant washing and compared with enzymatic proteolysis. The results demonstrated that allergenic and extractable proteins, as well as other extractable contaminants, in the vulcanised NR latex were effectively eliminated through multiple washing cycles, with even greater efficiency achieved through enzymatic treatment. Importantly, the purified films retained good mechanical and dynamic properties, highlighting the successful preparation of high-purity prevulcanised NR latex suitable for medical applications.