OLIANI, W.L.PARRA, D.F.LIMA, L.F.P.C.LUGAO, A.B.2014-11-192014-11-192015-04-012014-11-192014-11-192015-04-01OLIANI, W.L.; PARRA, D.F.; LIMA, L.F.P.C.; LUGAO, A.B. Thermooxidative degradation of high melt strength polypropylene (HMS-PP). In: MEETING OF THEN IONIZING RADIATION AND POLYMERS SYMPOSIUM, 9th, October 25-29, 2010, Maryland, USA. <b>Abstract...</b> Disponível em: http://repositorio.ipen.br/handle/123456789/21285.http://repositorio.ipen.br/handle/123456789/21285Modified properties of polyolefins, including iPP, must find an explanation in terms of the basic irradiation processes: crosslinking , branching and degradation. HMS-PP in pellets form was synthesized by the gamma irradiation (60Co) of PP under a crosslinking atmosphere of acetylene with doses of 5, 12.5 and 20 kGy. After irradiation the samples were submitted to a thermal treatment at 90 °C for 1h to eliminate residual radicals [1,2]. A common approach for characterizing ageing response in a more practical time frame is to conduct accelerated ageing tests at temperature above the expected service limits. The thermal stability of the HMS-PP was evaluated after thermal ageing of dumbbell samples using a stove at temperature of 120 °C, in presence of air at different periods of time. The surface of PP , pristine and modified, (i.e., irradiated), was studied using optical microscopy (OM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X ray scattering. The effects of elevated temperature ageing were evaluated in HMS-PPs exposed surfaces according to the order: HMS-PP 20 >12.5 >5 kGy, showing intense crack formation in all the exposed surfaces due to thermooxidative degradation. The results were compared with previous work [1] where no evidence of thermoxidation was reached, exposition applied test at temperature of 90°C. The new condition is more conclusive about the effect of the thermooxidative degradation in the irradiated materials.openAccesspolypropyleneirradiation procedurescross-linkingthermal degradationpelletsgamma radiationcobalt 60post-irradiation examinationheat treatmentsagingResumo de eventos científicoshttps://orcid.org/0000-0002-1737-3191https://orcid.org/0000-0002-7626-880X