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The morphological, mechanical, thermal, and tribological properties of high‐density polyethylene (HDPE) composites reinforced with organo‐modified nanoclay (3 and 6 wt%) were studied. A commercial maleic anhydride‐based polymeric compatibilizer (PEgMA) was used to improve the adhesion between the polyethylene and clay. Transmission electron microscopy (TEM) characterization of composites revealed that nanoclay exists mainly in a multilayered structure in the HDPE matrix. Mechanical testing of composites showed that Young's modulus and tensile strength increased with nanoclay content. Coefficients of the linear thermal expansion (CLTE) of HDPE–PEgMA–clay composites were slightly lower in the flow direction than those of HDPE–PEgMA. The tribological properties were measured in dry conditions against a steel counterface. The friction coefficient of the matrix was decreased by the addition of clay. Electron microscopic results suggested that the wear mechanism for HDPE and HDPE composites was mainly adhesive. Clay agglomerates were observed on the worn surfaces of the composites, which may partly explain decreased friction. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

An effective solution mixing method starting from a synthesis solution of SiO 2 nanoparticles was developed for dispersing nanoparticles into high-density polyethylene (HDPE). Spherical SiO 2 nanoparticles with narrow size distribution (50-100 nm) were prepared by Stöber method, and solvents of the synthesis solution (EtOH/ NH 4 OH) were gradually replaced with toluene by evaporation under reduced pressure. The SiO 2 nanodispersion, in toluene and residual ethanol, was mixed and refluxed with dissolved maleic anhydride grafted polyethylene (PEgMA) at a relatively high SiO 2 content (17.8 wt %). The PEgMA-SiO 2 masterbatch was filtered, dried under vacuum, and mixed with HDPE by melt compounding. SiO 2 contents in the final HDPE nanocomposites were 3 and 5 wt %. SEM images of the masterbatch and final composites showed the SiO 2 nanoparticles to be well dispersed in HDPE. No agglomerates were observed. FTIR results suggest that the interactions between the maleic anhydride group of PEgMA and hydroxyl groups of SiO 2 surface involve ester and/or hydrogen bonding. Addition of SiO 2 particles and PEgMA to HDPE slightly increased Young's modulus, tensile strength, breaking strength, and elongation at break, indicating enhanced toughness of the nanocomposites. The measured Young's moduli of HDPE-PEgMA-SiO 2 composites agreed well with Young's moduli predicted by Mori-Tanaka composite theory.