Rubber conducting species

Chemically the NR produced by the Hevea brasiliensis species is almost pure cw-l,4-polyisoprene. So far none of the manufacturers of synthetic cis-, A-polyisoprene is able to achieve more than 95% of the cis isomer in their commercial products. Jitladda and coworkers have conducted extensive studies on the molecular structures of the NR molecules found in Hevea and correlated these to the biosynthesis of this in the trees. This is intrinsically linked to the end groups of the rubber molecules involving the phospholipids and proteins that are linked to the charging mechanism at the latex particle surface and hence has a direct impact on the stability of the latex. 

Continuous low level current measurements are used to investigate the vulcanisation of natural rubber with sulphur, 2-mercaptobenzothiazole and zinc oxide in the presence and absence of stearic acid. At elevated temperatures, the mixtures showed increased conductivity, which was attributed to the presence of ions. Current curve maxima, characteristic of transitory ionic species are detected. Possible ions are discussed in coimection with references in the literature. For the mixture NR/S/MBT/ ZnO/StAc, the comparison with the rheometer measurements demonstrates a relationship between the formation of ionic intermediates and crosslinking of the polymer. The suitability of the electrochemical method for the investigation of ionic species in crosslinking reactions is demonstrated. 20 refs. 

Among the various plastic materials used for chrome-plated parts, ABS (copolymer of acrylonitrile-butadiene-styrene) and PC/ABS (blends of ABS with polycarbonate) are most common. Nearly 85% of the total plated plastic surface area is based on ABS or PC/ABS. The technology for etching out the rubber particles from the ABS phase using an oxidative mixture of sulfuric and chromic acid has been widely used in the industry for nearly 40 years. The etched surface is subsequently activated using precious metal species, which is then followed by an electroless deposition of a thin layer of nickel or copper. In this marmer, the smface of the otherwise non-conductive plastic is rendered electrically conductive. Subsequently, multiple layers of different... 

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