Tribo-mechanical properties of pure thermoplastic polyurethane and functionalized monolayer graphene-reinforced thermoplastic polyurethane polymer nanocomposites are investigated by molecular dynamics simulations. Initially, the mechanical properties of the thermoplastic polyurethane and functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposites are measured by applying constant stain method. Subsequently, interfacial layer models are developed to apply confined shear on the iron layers to find out the coefficient of friction and the abrasion rate of pure thermoplastic polyurethane and functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposites. The results imply that by the incorporation of 0.5 wt.% functionalized monolayer, graphene shows the increase of 20% in Young’s modulus, 15% in shear modulus and 6.66% in bulk modulus of pure thermoplastic polyurethane, respectively, which are in good agreement with the previous experimental studies. Maximum enhancement of mechanical properties can be obtained up to 3 wt.% addition of functionalized monolayer graphene addition in thermoplastic polyurethane matrix. Further, it is observed that 3 wt.% of functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposite results in minimum coefficient of friction (0.42) and abrasion rate (19%) under constant normal load (5 kcal/mol/Å) and maximum sliding velocity (11 m/s). However, further reduction in minimum values of coefficient of friction and abrasion rate at 3 wt.% of functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposites is seen under the minimum sliding velocity (1 m/s) considered with the same normal load condition. Finally, the inherent mechanisms for enhancement of tribo-mechanical properties in functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposites are analysed by the atomic density profile, free volume and Connolly surface at the atomic level.

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基于分子动力学的功能化石墨烯增强热塑性聚氨酯纳米复合材料摩擦学性能研究

通过分子动力学模拟研究了纯热塑性聚氨酯和功能化单层石墨烯增强热塑性聚氨酯聚合物纳米复合材料的摩擦力学性能。最初，热塑性聚氨酯和功能化单层石墨烯增强热塑性聚氨酯纳米复合材料的机械性能是通过应用恒定染色法测量的。随后，开发了界面层模型以对铁层施加有限剪切，以找出纯热塑性聚氨酯和功能化单层石墨烯增强热塑性聚氨酯纳米复合材料的摩擦系数和磨损率。结果表明，通过掺入 0.5 wt.% 的功能化单层，石墨烯的杨氏模量增加了 20%，纯热塑性聚氨酯的剪切模量分别为 15% 和 6.66%，体积模量分别为 15%，这与之前的实验研究非常吻合。在热塑性聚氨酯基体中添加最多 3 wt.% 的官能化单层石墨烯，可以最大程度地提高机械性能。此外，观察到 3 wt.% 的官能化单层石墨烯增强热塑性聚氨酯纳米复合材料在恒定法向载荷 (5 kcal/mol/Å) 和最大滑动下产生最小摩擦系数 (0.42) 和磨损率 (19%)速度 (11 m/s)。然而，摩擦系数和磨损率的最小值在 3 重量％时进一步降低。在相同正常负载条件下考虑的最小滑动速度 (1 m/s) 下，可以看到官能化单层石墨烯增强热塑性聚氨酯纳米复合材料的百分比。最后，通过原子密度分布、自由体积和康诺利表面在原子水平上分析了功能化单层石墨烯增强热塑性聚氨酯纳米复合材料摩擦力学性能增强的内在机制。