Abstract
The aim of the present study was to determine whether electron beam (E-beam) radiation has any depth dependent effect on the mechanical and degradation properties of a typical degradable polymer used for medical applications. Any such effect could be utilised to tailor the properties of degradable polymers for a specific application. The material investigated in the present study is a form of polylactide (PLA). Thin layers of the material were compression moulded and arranged at various depths within a framework, with acrylic spacers separating them. The samples were then dosed with 40 kGy of E-beam radiation. Following irradiation the samples were subjected to accelerated aging through hydrolytic degradation in phosphate buffer solution at 70°C. Gel permeation chromatography testing showed that samples within a certain distance of the irradiated surface had consistently lower molecular weight than deeper samples throughout degradation. Corresponding to this, the shallower samples also had lower tensile and flexural strengths than the deeper samples, though no significant variation in modulus was recorded. The results of this study indicate that E-beam radiation can produce a depth dependant variation in mechanical and degradation properties of PLA. The potential therefore exists to modify the through thickness properties of a degradable polymer in such a way as to improve its suitability for a specific medical application.
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