Polyisoprene peroxide cross-linked

Fig. 32. First derivatwe ESR spectrum at 123 A from peroxide cross linked cis-polyisoprene, tensile tested at 77 K in an oxygen free nitrogen atmosphere...

Silicone, natural, and synthetic rubbers have been used for the fabrication of implants. Natural rubber is made mostly from the latex of the Hevea brasiliensis tree and the chemical formula is the same as that of cw-1,4 polyisoprene. Natural rubber was found to be compatible with blood in its pure form. Also, cross-linking by x-ray and organic peroxides produces rubber with superior blood compatibility compared with rubbers made by the conventional sulfur vulcanization. 

M = 182 X 10 g.moLe" ) and 25 % of polyisoprene chains of low molecular weight (M = 50,000), the microstructure of which is similar to that of IR 307. Tfiese matrices (99 %) were mixed in solution with labeled anionic polyisoprene chains containing a dimethylanthracene (DMA) fluorescent group at their centers. The labeled polyisoprene had the same microstructure as IR 307 and its molecular weight was M = 60.10 g.mole. Samples were molded and cross-linked with dicumyl peroxide. Measurements of stress and orientation were done during uniaxial stretching at constant cross-head speed, V = 50 mm/min, and at a temperature of 298 K. 

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