Injection‐Molded Ultrahigh Molecular Weight Polyethylene Material with Improved Moldability for Artificial Joint Implants Design

Abstract

Ultrahigh molecular weight polyethylene (UHMWPE) is a linear (nonbranching), semicrystalline polymer with unique mechanical, physical, chemical, and tribological properties. [1,2] The UHMWPE structure is formed by the repetition of elementary units (C 2 H 4 )n, where n > 36 000 is the polymerization degree, arranged in both crystalline and amorphous regions to form extremely long chains with molecular mass greater than 10 6 g mol À1 . [3] Owing to this considerably high molecular mass, UHMWPE attained its exceptional characteristics such as outstanding impact strength, crack propagation resistance, relatively high strength, excellent fatigue resistance, low friction coefficient, selflubrication, high chemical resistance, and recognized biocompatibility. [4,5] Moreover, UHMWPE is the thermoplastic polymer with the highest wear resistance in almost all types of wear modes. [6] By virtue of these matchless properties, UHMWPE became the preferred polymer for bearing surfaces in total joint implants since the 1970s. [1,[7][8][9]

Replication Study of Molded Micro-Textured Samples Made of Ultra-High Molecular Weight Polyethylene for Medical Applications

“…UHMWPE has an essentially zero melt flow index, poor dissolution, and extremely high melt viscosity, and it is hard to process by conventional extrusion and injection molding (IM) technologies [ 16 , 17 , 18 , 19 , 20 ]. Indeed, the main processing technology for UHMWPE is compression molding, which, however, has a lower replication capability with respect to injection molding and it is not suitable for mass production.…”

“…Indeed, the main processing technology for UHMWPE is compression molding, which, however, has a lower replication capability with respect to injection molding and it is not suitable for mass production. In other words, the injection molding of UHMWPE is still a challenge, especially with the need for micro-features to be replicated accurately and repeatability [ 17 , 20 ]. Yilmaz G. et al [ 17 ] addressed the issue of the delamination on the injection-molded UHMWPE parts.…”

“…Sánchez-Sánchez X. et al [ 19 ] implemented an ultrasonic-assisted injection molding to optimize the filling phase of UHMWPE. Recent progress was achieved with the high-temperature melting (HTM) technique using a significantly higher melt temperature and injection pressure to process UHMWPE by injection molding [ 20 ]. These issues are amplified with surface micro-texturing, where the replication capability of molds is crucial.…”