Efeito da irradiação por feixe de elétrons sobre as propriedades físicas e químicas de uma resina de polipropileno. / Effect of electron beam irradiation by on the physical and chemical properties of a resin polypropylene.

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

30/03/2011

RESUMO

A polypropylene resin was modified in the present work by submitting standard tensile specimens to electron beam irradiation, with doses corresponding to 20, 40, 60, 100, 200 and 300kGy. The effect of this irradiation upon the polymer\ s chemical and physical properties was investigated, in particular seeking a possible correlation between these properties and instrumented indentation results, as it is common usage in the case of metals and alloys. The polymer was submitted to tensile, instrumented indentation, X-ray diffraction (DRX), electron spectroscopy (UV-VIS), vibrational infrared spectroscopy (FTIR), melt-flow index, gel fraction and thermal analysis tests. Concerning the chemical properties, it was observed that up to 20kGy dose there is no evidence of radiolytic oxidation in the polymer. Above 40kGy dose it was observed the irreversible yellowing of the samples, indicating the growing presence of chromophore groups (e.g. -C=O), which was confirmed by the UV-VIS results. The FTIR data could not confirm this hypothesis, but it was observed that the sample preparation method severely affected the FTIR spectra, casting doubt about its representativity. This failure of the FTIR data to identify the growing presence of carbonyl groups does not invalidate the previous results. Concerning the physical properties, X-ray diffraction showed that irradiation did not change the crystal structure of the polymer and no significant changes in lattice parameters could be identified either. The samples crystallinity, however, shows a remarkable reduction up to 60kGy dose. At the 100kGy sample, however, it was observed a recover of the crystallinity, which was attributed to radiation induced recrystallization. The thermal degradation resistance of the polymer enhanced up to 60kGy dose and remained approximately constant for higher doses. The yield strength of the samples kept approximately constant up to 60kGy dose, but decreased after that. Finally the instrumented indentation results where not sensible enough to detects the macroscopic mechanical properties, but the estimated Young\ s modulus shows a remarkable reduction for radiation doses equal or higher than 100kGy, which correlated well with the other chemical and physical properties.

ASSUNTO(S)

ionizing radiation mechanical properties of the solution polypropylene propriedades mecânicas da solução radiação ionizante resinas resins

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