Friction reduction due to plasmapolymeric coating in spite of lubrication deficiency

Reducing friction and thereby saving energy is of special interest for several industries like automotive, wind energy and any other section using elastomeric components, for example sealing rings. Unpredictable, deficient lubrication can occur and damage the sealing. Applying a plasmapolymeric coating on elastomers the friction can be reduced. Four elastomer types (acrylic rubber, fluoric rubber and two different nitrile butadiene rubbers) were investigated each with and without plasmapolymeric coating. The experiments were performed on coated and uncoated flat elastomer plates and the friction reduction was measured using a Universal Material Tester (UMT3) system with oscillating Pin-on-plate contact geometry. The face of a cylindric wheel bearing with 6 mm in diameter was used as counterpart. The contact geometry was chosen due to the differentiability of lubricants in oscillating tests as well as the 104 times bigger contact area compared with the sealing lip of a r adial shaft sealing. The tribological tests were done under ambient conditions with a velocity of 200 mm/s and a stroke length of 11 mm. The used normal force of 10.6 N represents an initial contact pressure of 0.5 MPa. The tests were performed using different small amounts of fully formulated gear oil down to avoiding lubricants to demonstrate the effect of lubrication deficiency. The coated elastomers showed a reduced friction compared to the uncoated ones. If a coating was applied to the elastomers the measurements without any lubrication showed the lowest friction. Friction coefficients down to 0.17 were achieved. Compared to 0.48 for the dry measurement with uncoated substrate, a friction reduction of 65 % was reached. This demonstrates emergency running properties for plasmapolymeric coated components. For the lubricated measurements differences between the different lubrications appeared.