Effect of soft carbon black on tribology of deproteinised and polyisoprene rubbers

In this work, the tribological properties of deproteinised natural rubber (DPNR) were examined and compared with synthetic cis-1,4-polyisoprene rubber (IR), namely Natsyn 2200. The effect of adding carbon black (CB) (0, 25 and 50phr) to both DPNR and IR on the friction and wear characteristics was investigated. Dry abrasion tests were carried out using pin-on-cylinder tribometer with abrasive paper (Diamond 50) under different operating test conditions such as applied normal load (5-35 N), sliding speed (0.3-1.5 m/s) and sliding distance (90-450 m). Experimental results showed that the addition of CB has significantly affected the wear and friction characteristics of both DPNR and IR, i.e. it reduces the abrasion weight loss by more than 70% compared to unfilled rubber, depending on the test conditions and the concentration of CB. The friction coefficient of DPNR was decreased by about 12.5% upon the addition of 50 phr CB, compared to unfilled DPNR. Meanwhile, adding (25-50 phr) CB to IR drastically deteriorates the friction coefficient, i.e. an increase in the friction by about 200% at 25 phr CB and 300% at 50 phr CB compared to unfilled IR. Finally, scanning electron microscopy (SEM) technique is employed to observe the abrasion pattern of rubber in order to correlate the experimental test results to the wear mechanisms. (c) 2006 Elsevier B.V. All rights reserved.