Insights into synergic antioxidant effects for vitamin E and sugar alcohol stabilized ultrahigh molecular weight polyethylene composites for artificial joints

Oxidation resistance is strongly necessary for the use of crosslinked ultrahigh molecular weight polyethylene (UHMWPE) in artificial joints. The hybrid antioxidant strategy emerged as a promising alternative to the single rival that relies on vitamin E (VE). The goal of this study was to investigate the universality of the antioxidant synergy between VE and sugar alcohol (SA). Three types of SA, including D-sorbitol, maltitol and erythritol, were employed to cooperate with VE. Compared to the use of VE alone, these hybrid antioxidants generally enabled the corresponding UHMWPE composites with prolonged oxidation induction time (OIT) and increased crosslink density. The correlation between OIT and crosslink density of VE/SA-stabilized UHMWPE composites showed low attenuation. The applicability of the hybrid antioxidants to protect UHMWPE against oxidation was further demonstrated using the in vitro clinically relevant accelerated aging. Among the used SA, D-sorbitol exhibited the strongest ability to enhance the synergetic efficiency. The possible mechanism was revealed from the following aspects: the number of secondary hydroxyls per molecular mass and the molecular polarity determined via polarity parameter calculation. These findings provide significant insights for fabricating UHMWPE bearing materials with superior comprehensive performance and extended service longevity.