CHEMICAL MODIFICATION OF BACTERIAL ELASTOMERS .2. SULFUR VULCANIZATION

Enhancement in the elastic response of a bacterial thermoplastic elast omer, poly(beta-hydroxyoctanoic-co-undecylenic acid), containing varyi ng amounts of unsaturation was attempted through sulfur vulcanization. Sol-gel analysis verified that crosslinking had occurred and that cro sslinking varied with vulcanizing agent type and concentration. Differ ential scanning calorimetry showed that crosslinking could eliminate a ll crystallinity. The elastic response was near ideal with less than a 5% tensile set after 200% elongation. In general, sulfur-vulcanized m aterials exhibited a decrease in tensile modulus, tensile strength and tear resistance which did not appear to vary with crosslink density. Unlike the case of peroxide crosslinking, material integrity was left intact and mechanical property results are reported. The network struc ture was elucidated through the determination of the molecular weight between crosslinks.