ASTM F2695-12 (2020) pdf free.Standard Specification for Ultra-High Molecular Weight Polyethylene Powder BlendedWith Alpha-Tocopherol (Vitamin E) and Fabricated Forms forSurgical lmplant Applications.
This specification is intended to describe the properties required and the procedures to be followed in testingunirradiated raw materials of UHMWPE blended with alphatocopherol for medical implant applications.This specificationdoes not purport to address the testing that is needed forimplants that are fabricated from the raw materials specifiedherein.
Alpha-tocopherol is a biocompatible stabilizer ofpolyolefins (1-6) and is intended to reduce oxidative degradation during processing, radiation processing, shelf life storage,and invivo exposure of UHMWPE.Several laboratory studieshave demonstrated that alpha-tocopherol will stabilize irradiated UHMWPE from accelerated aging conditions intended tosimulate a variety of severe oxidative challenges (7-12).Human clinical use of implants fabricated from alpha-tocopherol blended UHMWPE is reported to have begun in2004.At present,the extent to which alpha-tocopherol willhelp stabilize UHMWPE implants from invivo oxidation hasnot yet been determined.While beneficial for oxidative stability，levels ofalphatocopherol ≥1000 ppm may later interfere with subsequent radiation crosslinking steps (7，10) during subsequentstages of the implant manufacturing process. With 1000 ppm ofalphatocopherol,Oral et al. have reported an average reduction of 17 % in crosslink density following a dose of 100 kGy(7).On the other hand, levels of alpha tocopherol in the range125 to 500 ppm appear to be effective for stabilization ofUHMWPE,although the level of stabilization depends uponthe dose of radiation and the type of oxidative challenge (7,11,12).Thus，crosslinking will be a function of both the alphatocopherol content and the radiation dose, both of which maydepend upon the choice of the manufacturer. This specification is intended to describe the proper-ties required and the procedures to be followed in testingunirradiated raw materials of UHMWPE blended with alpha-tocopherol for medical implant applications.This specificationdoes not purport to address the testing that is needed forimplants that are fabricated from the raw materials specifiedherein. Alphatocopherol is a biocompatible stabilizer ofpolyolefins (1-6) and is intended to reduce oxidative degradation during processing, radiation processing, shelf life storage,and invivo exposure of UHMWPE.Several laboratory studieshave demonstrated that alpha-tocopherol will stabilize irradiated UHMWPE from accelerated aging conditions intended tosimulate a variety of severe oxidative challenges (7-12).Human clinical use of implants fabricated from alpha-tocopherol blended UHMWPE is reported to have begun in2004.At present,the extent to which alphatocopherol willhelp stabilize UHMWPE implants from invivo oxidation hasnot yet been determined.ASTM F2695 pdf download.