| It has always been a hot issue of material research to obtain a new-style antifriction wear-resistant materials of both excellent mechanical properties and tribological performance. Polymer matrix composites have been considered to be one of the most promising wear-resistant materials because of their low friction coefficient, low wear rate, high anticorrosion property, and light weight.The comprehensive performance of composites mainly depends on the matrix, the reinforced phase, and the interface between the matrix and the reinforced phase. Therefore, in this paper, the regulation and control on the mechanical properties and tribological performance of composites has been achieved by a reasonable selection of matrix and reinforcement materials, the optimization of process parameters, the interface optimization design based on the interfacial bonding mechanism of the composite materials. It is of great important for the development and investigation of the high-performance antifriction wear-resistant materials.Based on the above, in the present work, the polyetheretherketon (PEEK) is chosen as the matrix material for its excellent tribological properties, mechanical behavior and chemical properties, while the potassium hexatitanate whisker (PTW) is chosen as the reinforced phase for its high strength, high thermal stability and high cost-effective. The PTW/PEEK composites are prepared by extrusion and injection molding. The influence and its law of the reinforcing phase PTW and its surface modification on the mechanical and tribological properties of composites are investigated systematically. Further, the microscopic interface behavior of PTW/PEEK composites are analyzed by the First-principle calculations method based on density functional theory (DFT). It is expected to establish models including interface bonding strength, mechanical properties, and tribology properties of composites.The mechanical properties of PTW/PEEK composites are investigated on the whisker and its surface treatment. The results show that the impact strength of the composites filled with un-modification whiskers are decreased compared to the pure PEEK, while the tensile properties are nearly keep unchanged. However, the modified PTW can effectively improve increasingly the mechanical properties of composites with increasing whiskers. For the PEEK composites with15wt%of PTW, the tensile strength, bending strength, compression strength and impact strength are respectively increased by20.62%,20.45%,34.58%and73.68%to pure PEEK.The tribological properties of PTW/PEEK composites are investigated. It is found that the PTW can significantly improve the tribological properties of PEEK, especially affter its surface modification by the silanol. For the PEEK composites reinforced with15wt%of PTW, the friction coefficient and wear loss decreased by60.50%and59.21%compared to pure PEEK.The analysis of wear surface morphology shows that the addition of a proper amount of whiskers can enhance the plough resistance and abrasive wear resistance of the matrix. The whiskers can hinder the adhesive wear between PEEK and mating plate, which is helpful to improve the wear resistance of materials. The addition of another10wt%PTFE can further enhance the antifriction properties of PTW/PEEK composites.In order to explore the interfacial bonding behavior between the reinforcement phase and the matrix in PTW/PEEK composites, the micro-structure and physical properties of K2Ti6O13are studied by the First-principles calculations. It is found that K2Ti6O13crystal presents a kind of tunnel structure, which is connected by TiO6octahedron in the edges or faces and of high structure stability. Analysis of the electronic structures shows that within K2Ti6O13crystal, the Ti-O bonding interactions are stronger than that of K-O, and the structural stability of K2Ti6O13is closely associated with the bonding interactions between Ti (d) and O (p) orbitals. Further calculations on elastic properties show that K2Ti6O13is a high stiffness and brittle materials with small anisotropy in shear and compression properties. Based on the investigation on the physical properties of K2Ti6O13whisker, the microscopic interface bonding behavior between PEEK and PTW are further studied by the First-principle calculations method. It is found that the adsorption characteristic of silanol on K2Ti6O13(010) surface turns from physical adsorption to chemical adsorption due to the existence of hydroxyl, which enhances significantly the bonding strength between silanol and K2Ti6O13surface and further improves coupling agent modification effect. Analysis of the electronic structure shows that the inherent reason of the enhaced bonding strength between silanol and K2Ti6O13surface should be attributed to the contributions of O(s)(p) orbitals involved in hydroxyl and silanol. The combination between PEEK and silanol is achieved through imine followed alcoholamine which generated by the nucleophilic addition of the carbonyl group in PEEK chain and the silanol group.In addition, the influence mechanism of interface on tribological and mechanical properties of composites is discussed. Based on the theoretical analysis of mechanics, the interface shear strength is calculated, and the influence of the interface strength on the mechanical properties is well explained. Based on the theory of friction energy, fracture of surface material and fatigue fracture are analized, and the influence of the interface strength on the wear properties is explained. The intrinsic relation among interface bonding strength, tribology and mechanical properties of composites are established.The obtained results are expected to be the guidance for interface design and performance optimization of high performance polymer matrix antifriction wear-resistant composites. |
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