Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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2 resultados
Resultados da Pesquisa
- Assessment of the utilization of different peroxide dispersion media on the controlled degradation of polypropylene(2013-01-05) MUNOZ, P. A. R.; BETTINI, S. H. P.A two-step investigation of polypropylene-controlled degradation was performed. First the controlled degradation of polypropylene was investigated by assessing the effects of using dicumyl peroxide (DCP) and 2,5-dimethyl-2,5- di(t-butylperoxy) hexane (DHBP) in different suspensions (neat, calcium carbonate, and organically modified montmorillonite). The second part of this research was performed according to a factorial design at two levels (2 2 experimental design) with center point, in which peroxide concentration and reaction time were studied. Polypropylene degradation was assessed by melt flow rate (MFR) and parallel plate rheometry. Results showed that DCP presented higher molar efficiency in polypropylene degradation reactions in relation to DHBP; likely due to radical recombination reactions. The results also indicate that clay may catalyze the recombination reactions of polypropylene radicals. Copyright © 2012 Wiley Periodicals, Inc.
- Montmorillonite as support for peroxide in the melt grafting of maleic anhydride onto polypropylene(2016-11-10) MUNOZ, P. A. R.; BETTINI, S. H. P.© 2016 Wiley Periodicals, Inc.Grafting of maleic anhydride onto polypropylene was performed in a Haake torque rheometer, in the presence of organically modified montmorillonite, MMT (used as support for the peroxide), according to a 23 factorial design, where the maleic anhydride concentration (CMA), peroxide concentration (Cper) and reaction time (tr) were varied. For comparison, the reaction in the absence of MMT was also conducted. Polypropylene degradation was assessed by parallel plate rheometry and size exclusion chromatography (SEC) and percentage of reacted maleic anhydride (%MAg) was obtained by titration and FTIR spectroscopy. The results showed differences in both systems, conventional and in the presence of MMT. The structure of polypropylene grafted with maleic anhydride, PP-g-MA, indicates longer branches are formed in the presence of MMT compared to in its absence, demonstrated by FTIR analysis. As in conventional reaction systems, an increase in Cper caused an increase in %MAg and a reduction in molar mass. The variable CMA showed to be not significant in the grafting reaction in the presence of MMT, even at high DCP levels, at a 5% significance level. On the other hand, increase in CMA resulted in significant increase in viscosity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44134.