Effect of enzymolytic product on the curing characteristics and physico-mechanical properties of natural rubber

The natural latexes with different protein contents were prepared by centrifugation and then treated by alkaline protease to hydrolyze protein on the rubber particle surface, and the effects of protein hydrolysates on curing characteristics and dynamic behavior of natural rubber were studied. The results showed that with the increment of centrifugation times nitrogen mass fraction decreased from 0.27% to 0.13%, complex viscosity of raw rubber and curing rate of compound decreased, cross-linking density and mechanical properties of natural rubber vulcanizates declined, and storage modulus reduced under strain and frequency sweep. However, complex viscosity, curing rate, mechanical properties and storage modulus of natural rubber treated by multi-centrifugation and enzyme increased compared with those of natural rubber treated by only multi-centrifugation, due to the role of protein hydrolysates, and especially for the natural rubber treated by twice centrifugation and enzyme, curing rate could reach 17.8 min-1 and tensile strength could reach 23.73 MPa, which were significantly higher than curing rate of 9.59 min-1 and tensile strength of 20.52 MPa of natural rubber treated by only twice centrifugation, respectively