Journal of Thermal Analysis and Calorimetry, Vol. 67 (2002) 327–333 THERMAL ANALYSIS OF IONIZING RADIATION EFFECTS ON RECYCLED POLYAMIDE-6 M. C. Evora 1* , L. D. B. Machado 2 , V. L. Lourenço 1 , O. L. Gonçalez 1 , H. Wiebeck 3 and L. G. de Andrade e Silva 2 1 Centro Técnico Aeroespacial CTA / Instituto de Estudos Avançados/EFA-A, Caixa Postal 6044, 12231-970, São José dos Campos-SP, Brazil 2 Instituto de Pesquisas Energéticas e Nucleares IPEN-CNEN/SP, São Paulo-SP, Brazil 3 Escola Politécnica, Universidade de São Paulo, São Paulo-SP, Brazil Abstract The aim of this work is to study the ionizing radiation effects on thermal properties of the recycled polyamide-6. This polymer was irradiated with an electron beam of 1.5 MeV with different doses. The thermal properties of the samples were determined by TG, DSC and DMA measurements. It was observed that the irradiated samples of recycled polyamide-6 undergo a crosslinking process. Keywords: crosslinking, DMA, DSC, polyamide-6, recycled polyamide-6, TG Introduction Successive recycling promotes changes in several material properties, such as breaks of structures, increase of melt index, decrease of molecular mass and of mechanical resis- tance. These changes depend on the kind of recycled plastic resin, how and how long the recycle process takes place and the temperature and shearing strain applied [1, 2]. The interaction of the ionizing radiation with polymers results in energy transfer to them. This phenomenon may cause permanent modifications in the structure of the molecules. The induced modifications may bring degradation of the polymer or im- provement of its properties by crosslinking, which are simultaneous and competing processes, depending on the radiation dose applied. The ionizing radiation has suffi- cient energy to convert at least one electronically neutral atom or molecule in an ion pair. The energy released by this kind of radiation is so intense that the molecular spe- cies can be broken and, possibly, rearranged after a short period. This is the base for polymer research using ionizing radiation [3]. Studies of structural and many physical effects of gamma and electron beam irradia- tion on virgin poliamide-6 have been made previously, but controversies exist [4–8]. There is no investigation on the ionizing radiation effect on recycled polyamide-6. 1418–2874/2002/ $ 5.00 © 2002 Akadémiai Kiadó, Budapest Akadémiai Kiadó, Budapest Kluwer Academic Publishers, Dordrecht * Author for correspondence: E-mail: cecilia@ieav.cta.br