Resilience and Hysteresis of Nitrile Rubber Prodducts
Manufacturer: We are manufacturing rubber parts using Nitrile rubber. Please explain the resilience and hysteresis of nitrile rubber products compared to natural rubber. We would also appreciate your comment on ozone resistance of our nitrile rubber products.
John Woon (Senior Latex Consultant): I hate to disappoint you but NBR (Nitrile Rubber) has quite a poor resilience compared to either natural rubber, SBR (Styrene Butadiene Rubber) or
polychloroprene rubber although they are superior to butyl rubber.
Also, hysteresis is equally poor and hence NBR is not normally used where heat build-up on flexing is to be encountered.
However, you can improved theses properties to some extent by using soft carbon black, ester plasticizer along with a tighter cure. The resilience would increase if the content of acrylonitrile in NBR is reduced.
As regards ozone resistance of NBR, this also leaves a lot to be desired due to the presence of the "butadiene" component in the NBR structure. You could of course improve the ozone resistance by adding good antiozonants and waxes. However, when your products are exposed to oil and chemicals during services (I presume this being the reason for your choice of NBR), the antiozonants and waxes may be extracted leading to the products being prone to ozone again!