Tenacidade à fratura de policarbonato

ARTICLE IN PRESS

POLYMER TESTING
Polymer Testing 26 (2007) 315–322 www.elsevier.com/locate/polytest

Material Behaviour

Toughness behavior of gamma-irradiated polycarbonate
´ Naylor Sardinha de Melo, Ricardo Ponde Weber, Joao Carlos Miguez Suarezà ˜
ˆnica e de Materiais, Instituto Militar de Engenharia, Prac a General Tibu ´rcio 80, Sec a de Engenharia Meca - ˜o 22290-270 Rio de Janeiro, RJ, Brazil Received 28 September 2006; accepted 8 October 2006

Abstract The toughness behavior of polycarbonate sheets was investigated, before and after gamma irradiation in air, using physicochemical (determination of viscosity-average molecular weight and Fourier transform infrared spectroscopy) and mechanical (tensile and fracture toughness) tests. The failure mechanisms were analyzed by microscopy and related to the test results. It was found that, as the gamma irradiation dose is increased, there is a decrease in the molecular weight and an increase in the chain scission on carbonyl groups, as detected by infrared spectroscopy analysis. The mechanical properties of polycarbonate were affected by gamma irradiation, showing that polycarbonate presents a ductile-to-brittle transition as radiation dose increases, as confirmed by fractographic analysis. These results are presented and discussed. r 2006 Elsevier Ltd. All rights reserved.
Keywords: Polycarbonate; Gamma irradiation; Toughness; Fracture; Ductile-to-brittle transition

1. Introduction Polycarbonate (PC), an engineering thermoplastic, has found many applications in several industrial fields due to its high toughness, good ductility, high glass transition temperature, excellent optical clarity and dimensional stability. Among them is the use of PC in a variety of medical devices that must be sterilized before use. Ethylene oxide (ETO) is the standard choice in the sterilization process, but is being gradually replaced by gamma irradiation [1,2]. However, several polymer properties are subject to