Effect of Gamma and X-ray Irradiation on Polymers Commonly Used in Healthcare Products
Philip Roxby, Hervé Michèl, Céline Huart, Samuel Dorey
Abstract
Synthetic organic polymers commonly are used in the construction of healthcare product and medical device components.Medical devices often are sterilized to ensure that they are free from viable microorganisms.A common technique to achieve this is using ionizing radiation, usually gamma.A trend exists in industrial sterilization to supplement gamma with alternative accelerator technologies (e.g., X-ray).In the current work, studies were performed to characterize polymer modifications caused by gamma and X-ray sterilization processes and to assess the comparative equivalency.The studies were developed to evaluate two key process parameters: dose and dose rate.Three commonly used polymers were selected: high-density polyethylene, low-density polyethylene, and polypropylene.Four grades of each family were chosen.The dose assessment involved sample exposures to both gamma and X-ray irradiation at two dose levels (30 and 55 kGy).All other processing conditions, including dose rate, were controlled at standard processing levels akin to each sterilization technology.The dose rate assessment expanded on each dose level by introducing two additional dose rate parameters.Subsequent laboratory testing used techniques to characterize physico-chemical properties of the polymers to ascertain equivalency across test groups.Initial results indicated positive levels of equivalency between gamma and X-ray irradiation. Materials and Methods SamplesTo ensure this study was industry relevant, the sample materials chosen were of grades used in components that are found in various products (provided by Sartorius, Aubagne, France).A total of 12 polymer grades were tested.Ten were tested in molded component form, and two were tested as molded dogbones.Samples were not sterilized prior to the study.The three material families selected were: 1. High-density polyethylene (HDPE): Identified as HPDE-1, HPDE-2, HPDE-3, and HPDE-4, with density values ranging from 0.947 to 0.962 g/cm 3 and melt flow index [MFI] ranging from 6 to 26 g/10 min at 190C/2.16 kg. 2. Linear low-density polyethylene (LDPE):