ELASTOMERS, SYNTHETIC - POLYISOPRENE

Chlorosulfonated polyethylene, Vol. 8, Ethylene—acrylic elastomers, Vol. 8, Ethylene—propjiene—diene mbber, Vol. 8, Eluorocarbon elastomers, Vol. 8, 

The preparation of a synthetic polyisoprene was first reported in 1879 by Bouchardat (1), who treated isoprene [78-79-5] obtained from the destmctive distillation of natural mbber with hydrochloric acid. This discovery led to a search for a way of converting isoprene into a material dupHcating natural mbber (Hepea brasilienses). During World War II, scientists extensively studied the polymerization of isoprene with the hope of replicating natural mbber since the United States was temporarily cut off from sufficient natural mbber suppHes. These studies were not successful. PinaHy, in 1954 the B.E. 

In Table 1 some of the properties of raw synthetic hj -l,4-polyisoprene (Goodyear s Natsyn) and natural mbber (Hevea) are presented along with references that contain additional thermal, optical, electrical, and mechanical property data. Some properties of synthetic /n j -l,4-polyisoprene (Kuraray TP-301) are also given. Molecular weights and mol wt distribution are determined by gel-permeation chromatography (gpc) (11). 

Property cis-1,4- P olyis op rene tram-1,4- P olyis op rene  

The Goodyear The Rubber Co., Ziegler Ti—A1 catalyst. Gel content = 0% volatile matter = 0.3%. 

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Polymerization. Isoprene polymeri2ation can proceed by either 1,4- or l,2-(vinyl)addition (see Elastomers, synthetic-polyisoprene). 

Tires, natural mbber tubes, and butyl tubes are the main sources of scrap and reclaim (see Elastomers, synthetic-polyisoprene). Specialty reclaim materials are made from scrap siUcone, chloroprene (CR), nitrile— butadiene (NBR), and ethylene—propjlene—diene—terpolymer (EPDM) mbber scraps (see... 

Footwear -NBRm [ELASTOMERS, SYNTHETIC - NITRILE RUBBER] (Vol 8) -cis-l,4-polyisoprene m [ELASTOMERS SYNTHETIC - POLYISOPRENE] (Vol 9)... 

Natural rubber - [RUBBERCOMPOUNDING] (Vol 21) - [ELASTOMERS, SYNTHETIC - SURVEY] (Vol 8) -in adhesives [ADHESIVES] (Vol 1) -cellular forms [FOAMED PLASTICS] (Vol 11) -compared to polyisoprene [ELASTOMERS SYNTHETIC - POLYISOPRENE] (Vol 9) -fluonnahon of [FLUORINECOMPOUNDS,ORGANIC - DIRECTFLUORINATION] (Vol 11)... 

The use of alkali metals for anionic polymerization of diene monomers is primarily of historical interest. A patent disclosure issued in 1911 (16) detailed the use of metallic sodium to polymerize isoprene and other dienes. Independendy and simultaneously, the use of sodium metal to polymerize butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene was described (17). Interest in alkali metal-initiated polymerization of 1,3-dienes culminated in the discovery (18) at Firestone Tire and Rubber Co. that polymerization of neat isoprene with lithium dispersion produced high t /s- 1,4-polyisoprene, similar in structure and properties to Hevea natural rubber (see Elastomers, synthetic-polyisoprene Rubber, natural). 

With the availability of polymerization catalysts, extensive efforts were devoted to developing economical processes for manufacture of isoprene. Several synthetic routes have been commercialized. With natural rubber as an alternative, the ultimate value of the polymer was more or less dictated by that market. The first commercial use of isoprene in the United States started in 1940. It was used as a minor comonomer with isobutylene for the preparation of butyl mbber. Polyisoprene was commercialized extensively in the 1960s (6). In the 1990s isoprene is used almost exclusively as a monomer for polymerization (see Elastomers, synthetic-polyisoprene). 

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