The Origin of Strength of Natural Rubber: Network of Raw Rubber and Vulcanized Rubber

The green strength of un-vulcanized NR is elastic response with stain-induced crystallization while the one of un-vulcanized synthetic polyisoprene (IR) is viscous (polymer melt) without strain-induced crystallization. Vulcanization makes IR to be elastic rubber though vulcanized IR does not catch up vulcanized NR. Non rubber components and functional groups of rubber chains of NR have been considered to react with each other to make a kind of network. But the active non-rubber components are not specialized and the functional groups are also not defined yet. We like to compare NR, de-proteinized natural rubber (DPNR) and IR in order to find active non-rubber components and functional groups using synchrotron X-ray. It is revealed that phospholipids are major player in the network in un-vulcanized NR and proteins do not play as network points but agglomerates of proteins contribute to modulus and strength as kinds of fillers.