The Performance Of Low-Protein Natural Rubber And The Effect Of Bovine Albumin On The Curing Properties

The fresh natural rubber latex contains rubber hydrocarbon and water, as well as some non-rubber substance accounting for about5%, such as proteins, lipids, organic acids, carbohydrates, etc,These non-rubber substance are important for the performance of natural rubber (NR), in which proteins involve in the vulcanization of rubber,and have a major impact influence on curing properties of NR. However the role of each protein components is not very clear. In this thesis, the properties of the low-protein natural rubber (LPNR) was investigated, and bovine albumin (BA) was added to investigate the curing properties of compounded LPNR and isoprene rubber(IR) in relation with BA.First, the structure and performance of the prepared LPNR was studied comparing with NR. The results show that the nitrogen content of LPNR is0.12%. Compared with NR, initial plasticity (P0) and Mooney index of LPNR is slightly larger, while plastic retention index(PRI) is lower, indicating that the antioxidant propery of LPNR is worse. The thermal analysis indicates that thermal stability of LPNR in air and nitrogen is lower than that of NR. Thermal oxidative degradation in air can be divided into two steps. Kinetics of first step in the main degradation was calculated with Broido method. The activation energy Ea of LPNR thermooxidative degradation is108.58kJ/mol-1, lower than of NR(117.31kJ/mol-1), while the’s for the thermal degradation of LPNR and NR in N2atmosphere are228.91kJ-mol-1and248.01kJ-mol-1, respectively. With respect to the vulcanizates, the crosslink density of LPNR and NR was analyzed by NMR method, which illustrates that the crosslink density of LPNR vulcanizate is lower than that of NR. Mechanical properties testing shows a lower strength for LPNR vulcanizate.Secondly, BA was added to LPNR and IR to study the effect on the curing properties. With the increment of BA amount, the scorch time (t10) and the vulcanization time (t90) of LPNR curing decreased, while the maximum torque value increased. Kinetics research shows that the rate constants increase with the increment of BA amount. The presence of BA bings about a drop in Ea. When the amount of BA in the range of1.0-3.0phr, the mechanical properties was improved, as well as retention rate of tensile strength after aging, which may be related to the accelerating effect of B A on the curing and consequently the crosslink density. The typical phenomenon for IR curing is it’s longer t10due to lack of non-rubber substances which complex with curing ingredient and bring about a longer time for induction. After adding BA, the t10and t90decreased and the maximum torque value increased. Analysis in the crosslink density shows that IR+3.0BA has a crosslink density abvious higher than IR, which indicates the accelerating effect of BA on curing. The mechanical properties was improved with the increment of the amount of BA, as well as retention rate of tensile strength after aging.This research emphasized to study the effect of protein on the performance of NR, especially the curing properties, and to provide a research basis getting to know the role of non-rubber components in NR.