Influence of compositional variables and testing temperature on the wear of hydrogenated nitrile rubber

Abstract

The influence of the nature and level of the curing system, the loading of carbon black and the resin content on the abrasion loss,V, dynamic coefficient of friction, μ, and frictional force,F, of hydrogenated nitrile rubber (HNBR) against silicone carbide abrader, is reported at different temperatures.V, μ, andF decrease with cross-link density. At equal cross-link density, these parameters are the same for both peroxide and sulphur-curing systems. Incorporation of resin decreasesV, μ, andF progressively.V decreases, but μ and Fincrease with loading of carbon black at any particular testing temperature, and the opposite trend is observed with increasing temperature. Experimental results on natural rubber (NR) and styrene-butadiene rubber (SBR) are also compared with those of HNBR. The abrasion loss of HNBR is much lower than that of NR and SBR. The abraded surface of NR and SBR is tar-like and ridges are found at all temperatures. In the case of HNBR compounds no ridge, except plough marks in the direction of abrasion, is observed at 25°C. However, at high temperature (> 50°C) the abrasion mechanism changes, and ridge formation takes place. The ridge spacing,Rs, reduces with carbon black loading and decreasing temperature.Rs is related to dynamic shear modulus,G′, byRs=const. (1/G′)1.55.V increases linearly withRs. The abradability, A, is related to reciprocal of breaking energy,Eb, byA-itC/Eb, where C is a constant having a value of the order of 10−12 m3.