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Polyisoprene elastomers (the synthetic version of natural rubber) are synthetic, predominantly stereoregular polymers that closely resemble natural rubber in molecular structure as well as in properties. Polyisoprene elastomers are produced via solution polymerization using stereospecific catalysts. Chemically, natural rubber is pure cis-1,4-polyisoprene, while commercial grades of synthetic cis-1,4 isoprene rubber (cis-1,4 IR) have greater than 90% cis-1,4-polyisoprene content. trans-1,4-Polyisoprene (trans-IR) is also produced synthetically, but is of minor commercial importance.
During initial commercial development half a century ago, polyisoprene was positioned to replace natural rubber in applications such as tires and tire products. Polyisoprene offers some performance advantages over natural rubber but not in terms of overall cost.
The following pie chart shows world consumption of polyisoprene elastomers:
Tires and tire products accounted for about 70–75% of world polyisoprene consumption in 2007, and for over 90% of consumption in Central and Eastern Europe. Russia is and will continue to be the world market leader In terms of global polyisoprene elastomer capacity, production and exports.
Consumption and production of polyisoprene in the next five years are expected to show little if any growth in the United States and Japan, as tire production is expected to remain stagnant. Western European consumption will increase modestly and total Asian demand is expected to grow at moderate annual rates mainly because of increasing production of tires and other end uses in certain Asian localities.
Historically, natural rubber has sold for less than polyisoprene and is generally used except in applications where polyisoprene’s unique properties are required. Sometimes, small amounts of polyisoprene are added to natural rubber to facilitate handling and processing. As of 2007, natural rubber prices had escalated, but were still slightly below those of polyisoprene. It is speculated that polyisoprene and natural rubber prices will continue to rise in the near future.
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