321 – Bromobutyl (BIIR)

ASTM D-2000 classification: BA


Temperature Range:

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

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



Bromobutyl rubber is a derivative of butyl rubber derived from reacting butyl rubber with bromine in a continuous process. It is structurally similar to Chlorobutyl rubber and produced through the same halogenation process.

By adjusting the additives content in Bromobutyl rubber you can alter the range of polymer viscosities and cure responses. Compared with regular butyl rubber, Bromobutyl rubber provides faster and more stable cure through carbon-carbon linking.


Low permeability to air, gases and moisture.

Low glass transition temperature similar to regular butyl.

Wide vulcanization versatility.

Fast cure rates.

Processing safety: no nitrosamines or nitrosamines precursors.


EMI ReferenceSpecificationMVSGTensile Strength (MPa)Elongation at Break %Colour
321 – BIIR331Good Commercial33°0.9314400
321 – BIIR331Good Commercial40°0.9315400
321 – BIIR331Good Commercial45°0.9315400
321 - BIIR701Good Commercial70°0.9227500
321 - BIIR801Good Commercial80°0.9227500

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.