We investigated the mechanical properties and structure of polymeric nanocomposites (PNCs) with an ultrahigh-molecular-weight polyethylene (UHMWPE) matrix and aluminum and silicon oxide and nitride nanoparticle (NP) fillers. Mixing with a paddle mixer or by joint mechanical activation in a planetary mill was used for the PNC preparation. Joint mechanical activation afforded PNCs with better mechanical properties than paddle mixing. Scanning electron microscopy suggested that the poorer mechanical properties can be attributed to the disordered regions and imperfect spherulites in the PNC supramolecular structure arising from paddle mixing. The better mechanical properties observed with joint mechanical activation may derive from the uniform NP distribution in the polymer matrix and absence of disordered regions.Keywords: Ultrahigh-molecular-weight polyethylene, Nanoparticle, Polymer nanocomposite, Mechanical characteristics, Supramolecular structure
IntroductionIn recent years, the design and controlled fabrication of nanostructured materials with defined physicochemical properties have gained considerable interest. 1 Nanocomposites based on polymers and inorganic nanoparticles (NPs) have, in particular, demonstrated significant performance in terms of mechanical properties, fire resistance, gas permeability, and electrical conductivity.1 Conventional sealing, structural, and antifriction materials usually undergo degradation under extreme conditions, such as very low temperatures.2 Therefore, materials for application in arctic environments require high strength as well as frost, wear, and corrosion resistance. Ultrahigh-molecular-weight polyethylene (UHMWPE) is known to retain its high mechanical and tribotechnical properties at low temperatures, including cryogenic conditions, 2,4 and under high loading. 5 UHMWPE also shows excellent self-lubrication properties, high-impact strength, and excellent corrosion and frost resistance in comparison with other polymers. High-density UHMWPE provides good stiffness characteristics and abrasion and chemical resistance. 5 In addition to the intrinsic characteristics of UHMWPE, its mechanical and tribotechnical properties have been improved by the addition of NP fillers to the polymer. 6 Briscoe et al. demonstrated that the addition of PbO and CuO fillers to high-density polyethylene reduced wear because of the formation of a strong transfer film.7 By manufacturing composites of UHMWPE and ceramics such as Al 2 O 3 , ZrO 2 , and Si 3 N 4 , biocompatible and wear-and scratch-resistant hybrid materials were successfully fabricated recently and found applications in orthopedics. 8,9 Metallic silver NPs in UHMWPE demonstrated good wear and tribochemical properties. 10 We have reported different techniques to modify polymer nanocomposites (PNCs) 2,11 to achieve good tribotechnical and mechanical properties. It is to be noted that the uniform distribution of NPs in the PNCs is critical to achieving high tribotechnical and mechanical properties.12 Here, we report joint mechanical ...