The full text of this item is not available at this time because the student has placed this item under an embargo for a period of time. The Libraries are not authorized to provide a copy of this work during the embargo period, even for Texas A&M users with NetID.
Mechanical Characterization of Irradiated Polymers for Medical Applications
Abstract
Single use medical devices implement a variety of polymers and must be sterilized to destroy microorganisms and prevent disease transmission. Over the past several decades, gamma irradiation has been the primary sterilization technique for most medical devices. However, gamma irradiation utilizes cobalt-60 which poses a security threat as a radioactive source and has been challenged recently by growing shortages in supply. Non-isotope-based methods including e-beam and X-ray represent potentially beneficial alternatives to gamma radiation, but concerns remain that these modalities may adversely affect properties of the polymers relative to gamma irradiation. To fill in data gaps associated with a potential transition from gamma to e-beam or X-ray sterilization, this dissertation investigates the effects of gamma, e-beam, and X-ray irradiation on the mechanical, thermal, and structural properties of polymers that are commonly used in sterilized medical products.
Three prototypical commercial devices (VacutainerTM Plus tube and VacutainerTM Push Button Blood Collection Set) from Becton, Dickinson, and Company (BD) and (Stryker MixeVac-III® bone cement mixer, ME3) from Stryker instruments were investigated. These devices are currently sterilized by gamma irradiation. Standard specimen of six distinct polymer materials commonly used in the medical device industry, including low-density polyethylene (LDPE), chlorobutyl rubber (CIIR), and polyethylene terephthalate (PET), polypropylene (PP), polyolefin elastomer (POE), and polyvinyl chloride (PVC) as well as the devices themselves were exposed to target doses (15, 35, 50, and 80 kGy for BD devices and polymers, and 15, 25, 50, and 70 kGy for Stryker devices) using gamma, e-beam and X-ray radiation, and mechanical properties including tensile properties and hardness were then measured. Several chemical and thermal characterization techniques such as gel permeation chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR), dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC) were utilized to provide insight into the radiation-driven changes in chemical structure, and correspondingly how these chemical changes drive changes in mechanical properties. The results indicated that neither e-beam nor X-ray adversely altered the mechanical properties of the devices relative to that of gamma irradiation at sterilization-relevant doses for the vast majority of the polymers investigated.
Additionally, this dissertation investigates potential avenues toward sterilization and re-use of personal protective equipment (PPE). Since the onset of the COVID-19 pandemic, healthcare workers across the world have reported severe shortages of PPE, putting patients and frontline healthcare workers at risk of getting or transmitting COVID-19. E-beam irradiation and plasma reactive oxygen species (ROS) are potential candidates for decontamination of PPE for re-use during national emergencies in which supplies are diminished. This study assesses the structural integrity of commonly used PPE after these treatments, including N95 respirators, KN 95 respirators, gowns, and raw materials of polypropylene (PP) and polyester (PE). The tests indicate a decreasing tensile strength and elongation at break of AAMI and Activgard gowns with increasing dose of e-beam irradiation, whereas the plasma ROS treatment exhibits less detrimental effects and thus appears to be a strong candidate for bioburden reduction or decontamination of PPE.
Subject
PolymersRadiation effects
Sterilization
Gamma
X-ray
Electron beam
Reprocessing
Personal protective equipment
Citation
Hasan, Md Kamrul (2022). Mechanical Characterization of Irradiated Polymers for Medical Applications. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198606.