Effect of different parameters on the tribological performance of polypropylene/thermoplastic polyurethane blends under dry sliding conditions

Abstract

In this study, polypropylene/thermoplastic polyurethane (PP/TPU) blends (weight ratios of 75/25 and 25/75) were produced by melt blending, and a maleic anhydride-grafted polypropylene (PP-g-MA) copolymer was used as a coupling agent. The effect of the concentration of the coupling agent (5–11 phr), TPU concentration (25–75%), normal load (2–4 N) and sliding velocity (60–72 rpm) on the wear properties of the blends were characterized through a pin-on-disc abrasive wear test. A \(2^{4}\) full-factorial experimental design was chosen to screen the significant factors and their interactions influencing the tribological performance of the blends. After the tests, the morphology of the worn surface of the samples was observed using scanning electron microscopy. Shore D hardness tests were also conducted and the relationships between these behaviours were analysed on the basis of the findings. According to the wear test results, the factors that have the greatest effect on the wear rates are as follows: normal load, TPU concentration, sliding velocity and PP-g-MA concentration, respectively. The wear rate of the blends increases by increasing the normal load, TPU concentration and sliding speed, and slightly decreases by increasing the PP-g-MA concentration. As expected, the wear and hardness results showed the apparent superiority of the \(\hbox {PP}_{75}/\hbox {TPU}_{25}\) blends over the \(\hbox {PP}_{25}/\hbox {TPU}_{75}\) blends, because of the higher content of rigid segments in the blends.