Effect of moisture exposure on scratch behavior of four model cast polyurethane (CPU) elastomers with different soft segments is investigated. Two model CPU systems contain less polar ether groups and the other two contain more polar ester groups in the soft segment polyols. The ASTM D7027/ISO 19252 standard scratch test was chosen to determine the scratch behavior of the model CPU systems in dry and water-saturated conditions. It is found that the absorbed moisture alters the surface characteristics, mechanical properties and the corresponding scratch behaviors of PU elastomers in different fashions, depending on the PU chemical constituents. The homogeneously absorbed water molecules in the less polar polyether-based PU elastomers serve as plasticizer to degrade the mechanical properties and increase the coefficient of friction (COF), thus leading to deterioration in scratch resistance. However, for the more polar polyester-based PU elastomers, because of the interaction between water molecules and the polar bonding sites, clustering of water occurs on the surface and acts as lubricant to decrease the COF, which improves the scratch resistance. A 3-D finite element method (FEM) modeling was conducted to further understand the observed scratch-induced deformation in the model systems. The present study provides guidelines for preparing scratch-resistant PU elastomers that are exposed to humid environment during service.

研究了湿气暴露对具有不同软链段的四种模型浇铸聚氨酯（CPU）弹性体的划痕行为的影响。在软链段多元醇中，两个模型CPU系统包含更少的极性醚基，另外两个CPU系统包含更多极性酯基。选择ASTM D7027 / ISO 19252标准刮擦测试来确定CPU模型在干燥和水饱和条件下的刮擦行为。发现吸收的水分取决于PU化学成分以不同方式改变PU弹性体的表面特性，机械性能和相应的刮擦行为。极性较小的聚醚基PU弹性体中被均匀吸收的水分子充当增塑剂，从而降低机械性能并增加摩擦系数（COF），因此导致耐刮擦性变差。但是，对于极性更大的聚酯基PU弹性体，由于水分子与极性键合位点之间的相互作用，水在表面上发生团聚，并起润滑剂的作用，降低了COF，从而提高了耐刮擦性。进行了3-D有限元方法（FEM）建模，以进一步了解模型系统中观察到的刮擦引起的变形。本研究提供了制备在使用过程中暴露在潮湿环境中的耐刮擦PU弹性体的指导原则。水在表面上聚集，并起润滑剂作用以降低COF，从而提高了耐刮擦性。进行了3-D有限元方法（FEM）建模，以进一步了解模型系统中观察到的刮擦引起的变形。本研究提供了制备在使用过程中暴露在潮湿环境中的耐刮擦PU弹性体的指导原则。水在表面上聚集，并起润滑剂作用以降低COF，从而提高了耐刮擦性。进行了3-D有限元方法（FEM）建模，以进一步了解模型系统中观察到的刮擦引起的变形。本研究提供了制备在使用过程中暴露于潮湿环境中的耐刮擦PU弹性体的指导原则。