Perbunan® & Krynac®


ARLANXEO NBR clearly sets itself apart from other synthetic rubbers not only with regard to its oil resistance but also regarding its other strong properties. In addition to the key properties of our trademark products Perbunan® and Krynac®, processability is a further extremely important consideration when selecting NBR products. The compound produced from Perbunan® or Krynac® needs to pass through a variety of process stages due to the wider range of forms and processes. This creates special requirements in terms of flow and crosslinking behavior:

  • A faster cure rate paves the way for short cycle times and thus higher production rates
  • A slower cure rate determines the processing reliability with regard to: 

        - Improved scorch safety and significant longer flow paths

        - The shelf life of the ready-to-vulcanize compound


With an otherwise identical compound composition, there is a correlation between vulcanization rates and crosslinking densities, i.e.:

  • Faster vulcanization results in a higher modulus
  • Slower vulcanization results in a lower (but often adequate) modulus


Accordingly, ARLANXEO offers a comprehensive portfolio including everything from medium-curing grades to special fast- and slow-curing grades:

  • FC.CHM - Fast-curring grades with maximum purity    
  • FC.HM - Fast-curring grades
  • MC - Grades with a medium-curring rate
  • SC - Slow-curring grades


For illustration purposes, the following diagram shows the MDR t10 and t80 times characterizing the vulcanization rate. It also includes Smax as a measure of the modulus and crosslinking density. Krynac® MC grades with a medium cure rate are compared with faster-curing Perbunan® FC.CHM and FC.HM grades with a higher modulus. Krynac® SC grades are a little slower, which ensures optimal processing reliability.

Statistical average of Rheovulcametry-tests on various grades: Compound acc. to ISO 4658, Rheometer at 160°c.


In addition to these products with different vulcanization rates, there are two other Krynac® groups with special properties:

  • XL - Pre-crosslinked                                                      
  • X - Carboxylated                                                           


The individual product characteristics and the resultant benefits for compounders, processors and, ultimately, users are described in detail below.


Test conditions: MDR rheometer, 160 °c  /  Krynac®  and Perbunan® polymer: Acrylonitrile content: 28 %, Mooney viscosity (mL 1+4/100 °c): 45 MU Compound composition: see ISO 4968 (crosslinking with sulfur, sulfenamide).