320 – Isoprene (IR)

ASTM D-2000 classification: AA


Temperature Range:

Low Temp:    -56°C (-70°F) Brittle -62°C (-80°F)

High Temp:   105°C (220°F) intermittent 120°C (250°F)



The isoprene rubber (or IR rubber) is very much like natural rubber but made artificially or synthetically. The chemical name of isoprene rubber is synthetic cis-polyisoprene. Essentially similar to natural rubber in properties, this rubber may be somewhat weaker because it is not 100% the cis-isomer. This rubber is used in the same type of products as natural rubber.

The physical properties of IR rubber are in general somewhat inferior to those of natural rubber but, in principle, the two types of rubber are quite similar. This rubber has almost the same chemical structure as natural rubber (polyisoprene) but it does not contain proteins, fatty acids and the other substances that are present in natural rubber.

Isoprene (IR) rubber demonstrates lower green strength, slower cure rates, lower hot tear, and lower aged properties than natural rubber. It also exceeds the natural types in consistency of product, cure rate, purity and processing. In addition, isoprene rubber has the unique properties in the mixing, extrusion, molding, and calandering processes.


EMI ReferenceSpecificationMVSGTensile Strength (MPa)Elongation at Break %Colour
320 - IR701Good Commercial70°0.9227500Black
320 - IR801Good Commercial80°0.9227500Black

Full data sheets for all grades are available on request.

* The information above is supplied in good faith and believed to be correct. This information is supplied upon the condition that persons receiving this will make their own determination as to its suitability for their purposes prior to use. EMI makes no representations or warranties, either expressed or implied with respect to the information or the product to which this information refers.