Poly dienes vulcanization

Poly(diene) vulcanization can be carried out hot or cold. In the unaccelerated hot vulcanization at 120-160°C, sulfur attacks the a positions to double bonds and forms inter- and intramolecular cross-links, whereby some of the cis double bonds convert to trans double bonds (see also Section 23.5.3) ... 

Compatibilization along with dynamic vulcanization techniques have been used in thermoplastic elastomer blends of poly(butylene terephthalate) and ethylene propylene diene rubber by Moffett and Dekkers [28]. In situ formation of graft copolymer can be obtained by the use of suitably functionalized rubbers. By the usage of conventional vulcanizing agents for EPDM, the dynamic vulcanization of the blend can be achieved. The optimum effect of compatibilization along with dynamic vulcanization can be obtained only when the compatibilization is done before the rubber phase is dispersed. 

Abbreviations y x AFM AIBN BuMA Ca DCP DMA DMS DSC EGDMA EMA EPDM FT-IR HDPE HTV IPN LDPE LLDPE MA MAA MDI MMA PA PAC PB PBT PBuMA PDMS PDMS-NH2 interfacial tension viscosity ratio atomic force microscopy 2,2 -azobis(isobutyronitrile) butyl methacrylate capillary number dicumyl peroxide dynamic mechanical analysis dynamic mechanical spectroscopy differential scanning calorimetry ethylene glycol dimethacrylate ethyl methacrylate ethylene-propylene-diene rubber Fourier transform-infra-red high density polyethylene high temperature vulcanization interpenetrating polymer network low density polyethylene linear low density polyethylene maleic anhydride methacrylic acid 4,4 -diphenylmethanediisocyanate methyl methacrylate poly( amide) poly( acrylate) poly(butadiene) poly(butylene terephtalate) poly(butyl methacrylate) poly(dimethylsiloxane) amino-terminated poly(dimethylsiloxane)... 

The early synthetic rubbers were diene polymers such as poly butadiene. Diene elastomers possess a considerable degree of unsaturation, some of which provide the sites required for the light amount of cross-linking structurally necessary for elastomeric properties. The residual double bonds make diene elastomers vulnerable to oxidative and ozone attack. To overcome this problem, saturated elastomers like butyl rubber and ethylene-propylene rubber (EPR) were developed. These rubbers were, unfortunately, not readily vulcanized by conventional means. To enhance cure, it was therefore necessary to... 

For poly(styrene-b-butadiene-b-styrene) systems, and diene center blocks in general, the center block can be vulcanized following ordinary recipes. ... 

Fig. 8.1. Typical chemical groupings present in a sulphur-vulcanized natural rubber network, (a) Monosulphide cross-link (b) Disulphide cross-link (c) Poly sulphide cross-link (jc = 3-6) (d) Parallel vicinal cross-link (n = 1-6) attached to adjacent main chain atoms and which have the same influence as a single cross-link (e) Cross-links attached to common or adjacent carbon atom (f) Intra-chain cyclic monosulphide (g) Intra-chain cyclic disulphide (h) Pendent sulphidic group terminated by moiety X derived from accelerator (i) Conjugated diene (j) Conjugated triene (k) Extra-network material (1) Carbon-carbon cross-links (probably absent).

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