Strain hardening of HNBR

Date: September 14, 2023 2:00 pm (ET)


  • Christoph Gögelein
    ARLANXEO Deutschland GmbH


Strain hardening of HNBR

Christoph Gögelein and Marjan Hemstede-van Urk, ARLANXEO

Therban® hydrogenated nitrile rubber (HNBR) is a specialty elastomer used in demanding applications in the automotive, industrial, and oil and gas markets. It has a combination of good heat, oil and abrasion resistance in addition to its good mechanical strength, and good dynamic and compression set properties. It is well known that HNBRs with acrylonitrile (ACN) contents above ~ 40 wt% show strain-induced crystallization (SIC), caused by the crystallization of alternating ethylene-ACN units [1]. For HNBR polymers with lower ACN contents, crystallization occurs in longer ethylene units derived from hydrogenated butadiene sequences [2].

Besides these well-established findings, there is an ongoing debate up to which temperature SIC occurs for HNBR [3] [4]. Therefore, we investigated the strain hardening behavior of peroxide crosslinked HNBR polymers with ACN contents varying from 20 to 50 wt% in the temperature range from room temperature (RT) up to 100 °C. Moreover, we studied strain hardening of these HNBR vulcanizates at varying crosslink densities and varying filler loadings.

Our results reveal that there is a significant strain hardening behavior for HNBR vulcanizates with high ACN content, i.e., for > 43 wt% ACN content. The effect is still observed at 60 °C, but not at 80 °C. For samples with ≤ 43 % ACN content, strain hardening disappears between 40 and 60 °C. Most interestingly, for HNBRs vulcanizates with ≥ 43 wt% ACN content, tensile tests for varying rubber crosslink densities and filler loadings indicate that the strain hardening effect is very similar to that of natural rubber (NR). In contrast, for < 43 wt% CAN content, a qualitatively different behavior is observed. We rationalize these differences by means of the polymer’s microstructures and crystallization behaviors.

1-W. Obrecht, “Hydrierter Nitrilkautschuk – ein Werkstoff mit neuen Eigenschaften,” Die angewandte makromolekulaire Chemie, vol. 145/146, pp. 161-179, 1986.

2-R. E. Uschold and J. B. Finlay, “Elastomeric copolymers of ethylene and acrylonitrile,” J. Appl. Polym. Sci. Symp., vol. 25, pp. 205-222, 1974.

3-K. Narynbek Ulu, M. Dragicevic, P.-A. Albouy, B. Huneau, A.-S. Beranger and P. Heuillet, “Strain-induced crystallization ability of hydrogenated nitrile butadiene rubber,” in Constitutive Models for Rubber X, Munich, 2017.

4-B. H. K. Shaw, “Characterisation of elastomers for dynamic sealing applications, PhD thesis,” Queen Mary University of London, London, 2019.


Christoph Goegelein is working as a Principal Scientist at ARLANXEO Deutschland GmbH. He graduated in both Physics and Mechanical Engineering and received a PhD in Soft Matter Physics. Afterwards, Christoph stayed as a Postdoc at the Max-Planck-Institute for Dynamics and Self-Organization in Goettingen and joined ARLANXEO in 2012. His current research focuses on rubber networks. He is a member of the German Physical Society and the IUPAC Subcommittee for Industrial Polymers.