Tribological and Thermomechanical Properties of In-Situ Prepared TPU/Graphene Nanocomposites

摘要

Thermoplastic polyurethane (TPU) is well-known for its excellent mechanical properties, high abrasion resistance, and thermal and chemical stability. TPU and other elastomers are replacing traditional metal components due to the easy manufacturing of lightweight and low cost parts. Increasing demand from the medical and automotive industries is driving the development of TPUs with specific properties, in particular, the improvement of dry sliding friction in order to remove the need for liquid lubrication agents. Graphite and graphene have excellent solid lubricating ability, with an ultralow coefficient of friction of 0.03 regardless of the layer number when tested under micro-scale scratch tests. The goal of this study is to improve the dry sliding friction of TPU by incorporation of graphite and/or graphene fillers by in-situ polymerization. Incorporation of a solid lubrication agent during the polymerization reaction allows for improved coefficient of friction without further processing of the material or continual need for liquid lubrication during use. While improving the tribology of TPU is desirable, maintaining the mechanical performance is critical. In that regard, the effect of the solid lubricant on the thermomechanical performance of the TPU was evaluated by tensile and dynamic mechanical analysis, including creep recovery. The dry sliding friction was determined with tribology accessories on an ARES-G2 rheometer, allowing for the study of both load force and the rate-dependence of friction. The influence of filler aspect ratio and network strength on tribological properties was also investigated.