Abstract
Plastic sliding components are environmentally friendly, as they do not require the use of grease or oil, and much of this type of substance ends up in the environment as a result of accidents or spills. Unfortunately, at the end of the product lifecycle, plastic sliding component is a very bothersome waste. In addition, the products of wear are a source of microplastics entering the environment. Biodegradable polymers are the answer to waste problem. The aim of this article is to assess whether poly(lactic acid) (PLA), one of the most popular biodegradable polymers, has a chance to be used in sliding components. Since only a few reports on PLA friction and wear were found in the literature, a wide range of tests were carried out. The results obtained for PLA were compared to those obtained for polyamide 6 (PA6), which is a non-biodegradable material but is widely used in sliding components. The research showed that the biggest problem for PLA is its low temperature resistance. As a result, PLA can work with steel at significantly lower pressures and velocities than other plastics. At velocity of 1.0 m/s, PLA could cooperate with steel at a maximum pressure of 0.3 MPa, while PA6 could do it even at 2.0 MPa (at a pressure almost seven times higher). The wear and friction coefficient for PLA are also high (wear was 195 µm/km and coefficient of friction was 0.54 when velocity was 0.5 m/s and pressure was 0.7 MPa), and PLA also wore about four times more than PA6 during the abrasive wear test. When looking for a way to increase the ability of PLA to work at higher velocities and pressures, it is worth investigating annealed PLA, PLA blends with other biodegradable polymers, or PLA with the addition of hard fillers such as natural fibres or carbonates.