Archive for April, 2010
Synthetic Polyisoprene Rubbers (IR)
Trade Name : Natsyn (Goodyear Tire and Rubber Co.), Shell Isoprene Rubber (Shell international Chemical Co.)
Chemistry : IR is synthetic natural rubber that is cis-1,4 polyisoprene. It doesn’t contain the nonrubber substances that are present in NR. The different between two basic types of synthetic polyisoprene depend on the polymerization catalyst system used and are commonly referred to as “high” cis and “low” cis types.
The high cis grades contain approximately 97% cis-1,4 polyisoprene. Because of the high degree of stereoregularity, they are able to crystallize on stretching like NR. Consequently, they can be compounded without fillers, giving tensile strength nearly as high as that of unfilled NR vulcanizates.
The low cis grades contain about 93% cis-1,4 polyisoprene. They have limited use because the physical properties of their vulcanizates are inferior to those of high cis types.
Compounding : Synthetic IR can be compounded using the same ingredients used for NR and it can be blended with other diene rubbers such as NR, SBR and BR.
Applications :Synthetic IR can be used alone or in blends with NR in the manufacture of most products where NR is the traditional choice.