Scratch and Wear Behaviors of Polyurethane Elastomers

Given the unique block copolymer structure of polyurethane (PU) elastomers, each segment of them can be modified independently to obtain a wide range of properties that meet the needs of various engineering applications. However, the susceptibility of PU elastomers to surface damages like scratch and wear significantly limits their usage in applications where surface structural integrity and aesthetic appearance are of great importance. In order to gain fundamental understanding of scratch and wear behaviors of PU elastomers, this research focuses on experimental study along with numerical analysis of scratch and wear-induced deformation in PU elastomers, leading to effective design of scratch and wear resistant PU systems. Scratch process involves a single-pass sliding of a single-asperity across the polymer surface under the influence of an applied normal load. Wear process is more complicated, since it generally involves multi-passes and multi-asperities. Abrasive wear is one of the most common wear damages that polymers may experience during service. It is generated as the result of removal of material from polymer surface through penetration and sliding of sharp and hard asperities of the counterface, which is similar to the relatively well-establish scratch damage phenomenon. The present research work starts with the investigation on scratch behavior of PU elastomers using a standardized scratch test, various materials characterization techniques and finite element method simulation to determine the key material properties and surface characteristics that are related to scratch resistance of PU elastomers under two environmental conditions, i.e., dry and water-saturated. Afterwards, abrasive wear behavior of PU elastomers is investigated using a custom built multi-axis tribometer in a pin-on-flat configuration to establish physical correlation between abrasive wear and scratch behaviors. It is found that the key material property that is responsible for scratch resistance can be extended to abrasive wear resistance of PU elastomers. Ultimately, research effort is performed to explore the possibility of design of scratch and abrasive wear resistant PU elastomers by modifying their molecular weight, which has significant influence on the material properties of PU elastomers