학술논문
A New Method to Determine the Locus of Radiation Damage in Retrieved Ultra-High Molecular Weight Polyethylene (UHMWPE) Components
Document Type
stp-paper
Author
Source
Characterization and Properties of Ultra-High Molecular Weight Polyethylene, Jan 1998, Vol. 1998, No. 1307, pp. 79-94.
Subject
Language
English
Abstract
Gamma-sterilization can damage ultra-high molecular weight polyethylene (UHMWPE) that, after three to five years or more, can lead to the embrittlement of the polymer. In many cases, thin cross sections (100 μm) of the polymer have a gross appearance of a “white band,” generally 1 to 2 mm below the surface. This white band consists of cracks induced during sectioning in areas of embrittlement. We studied oxidation changes resulting in chain scission by exploring the effects of hot (110°C) xylene extraction on aged UHMWPE acetabular components. Hot xylene is a good solvent for polyethylenes and extracts the lower molecular weight species from UHMWPE. In so doing, it also extracts the lower molecular weight species that result from chain scission.
The xylene extraction studies revealed two interesting observations. First, the extent of extraction-induced white band was substantially in excess of the sectioning-induced white banding. The infrared determination of the oxidation extent was more accurately indicated by extraction than sectioning. Secondly, microscopic observation of the material prior to and after xylene extraction showed that the regions of greatest extraction of polyethylene were at the interfaces between individual flakes of the starting material. This observation indicates that a major site of preferential removal of polyethylene was at the interfaces and supports the concept of preferential O2 diffusion along the boundaries between the flakes of the original polyethylene resin.
The xylene extraction studies revealed two interesting observations. First, the extent of extraction-induced white band was substantially in excess of the sectioning-induced white banding. The infrared determination of the oxidation extent was more accurately indicated by extraction than sectioning. Secondly, microscopic observation of the material prior to and after xylene extraction showed that the regions of greatest extraction of polyethylene were at the interfaces between individual flakes of the starting material. This observation indicates that a major site of preferential removal of polyethylene was at the interfaces and supports the concept of preferential O2 diffusion along the boundaries between the flakes of the original polyethylene resin.