Enhancing the Wear Resistance of Low-Density Polyethylene by Conversion into a Thermoset or Graphite-Reinforced Thermoset Nanocomposite, with Implications for Reducing Degradation to Microplastics

To enhance the poor wear resistance of thermoplastic low-density polyethylene (LDPE), precursor LDPE powders are prepared via solid-state shear pulverization (SSSP) containing 0-7 wt% as-received graphite and 0-3 wt% dicumyl peroxide (DCP) as radical initiator, then consolidated and cured by compression molding. X-ray diffraction confirmed substantial exfoliation of graphite by SSSP. Relative to neat LDPE, LDPE thermosets exhibit reduced crystallization onset temperature, crystallinity, and elongation at break with increasing cross-link density. Incorporating well-exfoliated graphite increases crystallization onset temperature, Young’s modulus, and ultimate strength relative to the respective neat LDPE and thermoset controls, with crystallinity unaffected within uncertainty. Cross-links and well-exfoliated graphite act synergistically to yield thermoset nanocomposites with enhanced wear resistance. Relative to neat LDPE, thermosets made with 3 wt% DCP and thermoset nanocomposites made with 3 wt% DCP and 3 wt% graphite exhibit wear volumes reduced sixfold and eightfold, respectively. Such thermosets and thermoset nanocomposites provide simple approaches to improve the wear performance of LDPE. Furthermore, the powder outputs from SSSP have known melt processability that could include extrusion, injection molding, powder coating, and rotational molding. Lastly, improved wear resistance should reduce polymer debris emissions; we discuss design principles as potential pathways to mitigate wear-induced microplastic generation.