Molecular Weight Controls Entanglement Heterogeneity in Sintered UHMWPE

ABSTRACT The molecular weight of ultra‐high molecular weight polyethylene (UHMWPE) influences the mechanical properties of its sintered products, which is related to the development of entanglement networks in the bulk phase and interfacial phase. Herein, the impact strength of sintered UHMWPE products is investigated across a range of molecular weights. The results reveal a trend of an initial increase followed by a decrease as molecular weight increases, with a critical molecular weight ( M η = 150 × 10 4 g/mol) identified. Based on McLeish's theory, the chain entanglement dynamics in both bulk phase and interfacial phase are quantitatively analyzed. For low‐molecular‐weight UHMWPE ( M η < 150 × 10 4 g/mol), the interfacial entanglement network establishes faster than the sintering time, so the impact strength is primarily determined by the entanglement density of the bulk phase. Both higher molecular weight and a narrower molecular weight distribution promote bulk‐phase entanglement, thereby enhancing impact strength. In contrast, for high‐molecular‐weight UHMWPE ( M η > 150 × 10 4 g/mol), the formation of interfacial entanglements requires longer than the sintering time, making the impact strength dominantly controlled by the entanglement state at the interfacial phase. This research provides new insights into achieving high‐performance sintered UHMWPE products through the modulation of molecular weight and its distribution.