title: High temperature homogenization improves impact toughness of vitamin E-diffused, irradiated UHMWPE.
abstract: Diffusion of vitamin E into radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is used to increase stability against oxidation of total joint implant components. The dispersion of vitamin E throughout implant preforms has been optimized by a two-step process of doping and homogenization. Both of these steps are performed below the peak melting point of the cross-linked polymer (<140°C) to avoid loss of crystallinity and strength. Recently, it was discovered that the exposure of UHMWPE to elevated temperatures, around 300°C, for a limited amount of time in nitrogen, could improve the toughness without sacrificing wear resistance. We hypothesized that high temperature homogenization of antioxidant-doped, radiation cross-linked UHMWPE could improve its toughness. We found that homogenization at 300°C for 8 h resulted in an increase in the impact toughness (74 kJ/m2compared to 67 kJ/m2), the ultimate tensile strength (50 MPa compared to 43 MPa) and elongation at break (271% compared to 236%). The high temperature treatment did not compromise the wear resistance or the oxidative stability as measured by oxidation induction time. In addition, the desired homogeneity was achieved at a much shorter duration (8 h compared to >240 h) by using high temperature homogenization. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1343-1347, 2017.
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, 55 Fruit Street, GRJ 1260, Boston, Massachusetts 02114.|Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Ebru
authors.initials: E
authors.lastname: Oral
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, 55 Fruit Street, GRJ 1260, Boston, Massachusetts 02114.
authors.forename: Caitlin
authors.initials: C
authors.lastname: O'Brien
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, 55 Fruit Street, GRJ 1260, Boston, Massachusetts 02114.
authors.forename: Brinda
authors.initials: B
authors.lastname: Doshi
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, 55 Fruit Street, GRJ 1260, Boston, Massachusetts 02114.|Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Orhun K
authors.initials: OK
authors.lastname: Muratoglu
mesh_terms: D005720:Gamma Rays; D006358:Hot Temperature; D007595:Joint Prosthesis; D011095:Polyethylenes / Q000737:chemistry* / Q000528:radiation effects; D014810:Vitamin E / Q000032:analysis*
chemical_list: D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D014810:Vitamin E
keywords: antioxidant stabilization; arthroplasty; crosslinking; homogenization; total joint implants