Impact of Short-Chain Maleated Polyethylene Addition on Viscosity, Moldability, and Strength–Ductility Combination of UHMWPE Blends for Commercial Scale Manufacturing of Acetabular Liner

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) has long been used as a bearing component in joint replacement devices, particularly in total hip arthroplasty (THA) and total knee arthroplasty (TKA). These implants are conventionally manufactured using the machining route, and an alternative approaches to produce net-shaped UHMWPE implants has been explored to a limited extent. In this context, its high melt viscosity poses significant challenges in molding complex and thicker components, with uncompromised mechanical strength and ductility. To address both these aspects, a new processing strategy has been presented here, where a tailored amount of short-chain polyethylene grafted maleic anhydride (mPE) is introduced into UHMWPE via the melt compounding technique to enhance moldability. We optimized the injection molding parameters—including melt temperature, mold temperature, injection pressure, and injection time—within a narrow window to achieve a UHMWPE blend with enhanced mechanical properties. When compared to pristine UHMWPE 4% mPE blend exhibited a better melt flow index from 6.2 to 8.2 g/10 min and enhanced ultimate tensile strength (27.5 to 31.4 MPa) and elongation at break (46.4% to 77.7%). Additionally, the crystallinity of the mPE blends decreased to 51%, facilitating better flow characteristics, as indicated by a reduction in complex viscosity from 18.83 to 12.30 kPa·s. Using the optimised molding parameters, we successfully molded acetabular liners of commercial design with acceptable dimensional tolerances (shrinkage: 2.1%–2.4%; ovality: 0.06–0.09 mm) and without detectable internal defects, as analysed using micro-computed tomography (micro-CT). The present work highlights the potential of mPE blends in injection molding for producing high-performance orthopedic implants, addressing a critical gap in scalable manufacturing processes for components of varying sizes and shapes in biomedical applications.