Engenharia de Materiais

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https://repositorio.fei.edu.br/handle/FEI/17

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Navegando Engenharia de Materiais por Autor "Agnelli J.A.M."

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    Artigo
    Abiotic thermo-oxidative degradation of high density polyethylene: Effect of manganese stearate concentration
    (2017) Antunes M.C.; Agnelli J.A.M.; Babetto A.S.; Bonse B.C.; Bettini S.H.P.
    © 2017 Elsevier LtdThe effect of pro-degradant manganese (Mn) stearate concentration on the oxidative abiotic degradation of high-density polyethylene (HDPE) was investigated in thermo-oxidative tests at three temperatures (60, 70 and 80 °C) over time. Degradation monitoring was carried out, by determining carbonyl indices (CI), using infrared spectroscopy (IR), and by assessing molar masses and their distributions, using size exclusion chromatography (SEC) and tensile tests to assess mechanical properties. Deconvolution analyses of the absorbance bands obtained in the carbonyl region were performed to quantify the functional groups originated from degradation. Similar levels of degradation (equivalent molar mass and oxidation values) were obtained regardless of the investigated manganese concentration (50, 200 and 400 ppm). However, the results indicate that increasing Mn concentration may reduce the induction time for carbonyl formation. Deconvolution of the carbonyl region in IR spectra (between 1800 and 1650 cm−1) indicates that the addition of Mn results in increase in the concentration of oxidized functional groups (ketones, carboxylic acids, lactones, etc.) and that relationship between these groups varies depending on whether manganese stearate is present or not.
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    Artigo
    Correlating different techniques in the thermooxidative degradation monitoring of high-density polyethylene containing pro-degradant and antioxidants
    (2018) Antunes M.C.; Agnelli J.A.M.; Babetto A.S.; Bonse B.C.; Bettini S.H.P.
    © 2018 Elsevier LtdDifferent techniques were used to assess the effect of a primary and a secondary antioxidant, separately, and in combination with a pro-degradant (manganese stearate) on the thermooxidative abiotic degradation of high-density polyethylene (HDPE). The parameters measured over time at three temperatures (60, 70 and 80 °C) were variation in carbonyl index (CI), by means of infrared spectroscopy; reduction in tensile strain at break, by means of mechanical testing; reduction in molar mass distribution by means of size exclusion chromatography (SEC). Regardless of the presence of primary or secondary antioxidants, the same levels of degradation were attained. However, contrary to the secondary antioxidant, the primary antioxidant significantly increased induction time of HDPE oxidative degradation processes, evidenced by the shift in the “CI versus time” curve and by the considerably longer time for the strain at break to reach minimal values. Increase in thermooxidation temperature reduced induction time significantly.