Protein-free Natural Rubber

Protein-free natural rubber was prepared by incubation of high ammonia natural rubber latex with urea, sodium dodecyl sulfate and polar solvent at room temperature followed by centrifugation. Total nitrogen content and extractable protein content of natural rubber were reduced from about 0.4 w/w% and 100 μg/ml to 0.00 w/w% and 0.0 μg/ml, respectively, after removing all proteins from the rubber. Nanophase separated structure of natural rubber, in which natural rubber particles with a diameter of about 1 μm were dispersed in matrix of non-rubber components with a thickness of several tens nm, disappeared when the proteins were completely removed from the rubber. Stress at break of unvulcanized natural rubber was significantly larger than unvulcanized protein free natural rubber, while it was identical to unvulcanized DPNR. Water-uptake was dependent upon total nitrogen content and it was lowest for protein free natural rubber. The vulcanization time of natural rubber was prolonged by removing proteins and tensile properties of the vulcanized protein free natural rubber were better than natural rubber after immersing into ethylene glycol solution. It is found that the protein free natural rubber is a novel, superior rubber, which is distinguished from natural rubber.