Impact of microextrusion and addition of graphite nanoplatelets on bulk and surface mechanical properties of UHMWPE

A new processing route for producing ultra‐high molecular weight polyethylene (UHMWPE) nanocomposite combining swelling in toluene, microextrusion, and compression‐molding was developed. Using this novel method, extruded neat UHMWPE (e‐PE), and extruded UHMWPE blended with 0.5 wt % of graphite nanoplatelets (e‐PE/g) were processed. UHMWPE was also processed by compression‐molding (PE) as reference material. Bulk mechanical behavior of the materials was evaluated by tensile, bending and impact tests, while surface mechanical behavior was assessed by scratch and sliding wear experiments. We found that e‐PE/g has a brittle tensile behavior in comparison with the two other grades. Bending and impact toughness increase in this order: PE ≈ e‐PE/g < e‐PE. Scratch behavior of the materials is quite similar, e‐PE has however the lowest friction coefficient, and hence, exhibits antifriction properties. The cumulative sliding energy increases in this order: e‐PE ≈ PE < e‐PE/g, indicating that e‐PE/g may have a lower wear resistance as compared to the two other materials. The combination of extrusion with compression‐molding caused the formation of well‐consolidated meso‐domains containing oriented chains. Such a new morphology is at the origin of the high tensile strength, high fracture toughness, and antifriction properties of e‐PE that appears like a promising material for medical or machine construction applications. The addition of graphite nanoplatelets induces a poor consolidation that resulted from the segregation of the fillers between powder grains of UHMWPE. This explains the brittle tensile behavior and the high cumulative sliding energy of the UHMWPE nanocomposite.