Investigation Of Phospholipids On Vulcanization Characteristics Of Natural Rubber

Natural rubber(NR), obtained from Hevea brasiliensis, is an important industrial and strategic material due to its excellent comprehensive performances, such as high elasticity, creeping resistance, flexing resistances and low hysteresis loss. The contents and compositions of non-rubber constituents are generally varied with the planting environments and technologies and impact on the vulcanization characterizations of NR and hereby decrease the quality consistency of NR obviously. In this paper, the effects of phospholipids, the key component of non-rubber substance, on vulcanization characteristics of NR were studied systematically. The vulcanization rate differences among NR from different clones were reduced by regulating their phospholipids contents.The effects of phospholipids on the vulcanization characteristics and processabilities of NR and also the cross-linking densities and mechanical properties of vulcanizates were investigated by adding phospholipids in fresh latex. When the dry mass fraction of phospholipids added was increased to 1wt%, the vulcanization time of NR might be reduced by 19.45% and the retention percentages of the tensile strength and total crosslinking density of vulcanizate could be increased by 14.39% and 6.71%, respectively. The processabilities of NR were improved as the phospholipids amounts increased.The effects of the phospholipids adding methods on the vulcanization characterizations of NR and the mechanical properties of vulcanizates were also studied. By adding phospholipids at mixing step, the vulcanization time was shortened and the processabilities of NR were improved much obviously. When the dry mass fraction of phospholipids was increased to 1wt%, the vulcanization time of NR with adding phospholipids at mixing step might be reduced by 37.81% as compared with that by adding phospholipds into fresh latex.The effects of phospholipids hydrolysis on the vulcanization characterizations of NR were further studied. The vulcanization time of NR was almost kept in constant by adding pre-hydrolyzed phospholipids into fresh latex. However, the vulcanization time of NR was increased by 30.08% and the retention percentage of tensile strength was decreased by 14.57% by prolonging the storing time of fresh latex for 13 days.The total contents of phospholipids of NR from different clones were further regulated by adding phospholipids and the variance of vulcanization rate of NR thus obtained were reduced from 0.6093 to 0.0105. The quality consistency of NR might improved by regulating phospholipids contents to reduce the differences in vulcanization and processabilities.