Navegando por Palavras-chave "nanopartículas de prata"

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    Desenvolvimento de nanocompósitos de poli(3-hidroxibutirato-co-3-hidroxivalerato) com nanopartículas de prata
    (Universidade Federal de São Paulo (UNIFESP), 2016-02-25) Costa, Flavio de Souza [UNIFESP]; Passador, Fabio Roberto [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The utilization of biodegradable polymers from natural sources has been attracting attention from the academy and industry due to environmental issues. Among biodegradable polymers, PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)), a polyhydroxyalkanoate (PHA), is an example of a polymer of renewable origin that presents good biodegradability and processability. In this work PHBV films were developed with the addition of silver nanoparticles (AgNP), synthesized by the Turkevich method of reduction of Ag+ ions of silver nitrate by the oxidation of citrate ions and particle size were controlled by the addition of ammonium hydroxide. During the study the AgNP synthesis temperature were varied (90 °C and 97 °C) and so did the time of addition of ammonium hydroxide (6 minutes and 9 minutes for the synthesis at 90 °C and 3 minutes for the synthesis at 97 °C), in order to obtain the AgNP. Ammonium hydroxide was added to the colloidal suspension to guarantee stability and the nanometric size of the AgNP. The characterization of colloidal nanometric silver suspensions was evaluated by particle size analysis by dynamic light scattering (DLS), measures of zeta potential of the nanoparticles surface, UV-VIS spectroscopy of the colloidal suspensions and also wide angle X-ray diffraction (WAXD) and scanning electronic microscopy (SEM) of the dried powders. The films of neat PHBV and PHBV / AgNP nanocomposites containing 0.1, 0.5, 1.0, 1.5 and 2.0 wt % of AgNP were produced by solution mixing followed by solvent evaporation. The characterization of the films was evaluated by SEM, thermogravimetry (TGA) and differential scanning calorimetry (DSC). Biodegradable essays were carried out in liquid medium to verify the effect of addition of AgNP in the biodegradation process of neat PHBV films and PHBV / AgNP nanocomposites. It wasn´t observed difference in size between the AgNP synthesized at 90 °C with the addition of ammonium hydroxide having happened at 6 minutes or at 9 minutes. The synthesis at 97 °C led to the production of instable AgNP and was discarded as a possible route to synthesize the AgNP. The addition of AgNP to the PHBV matrix increases the crystallinity degree and decreases the thermic degradation temperature of the polymer. The biodegradable essay revealed that the addition of 0.5 wt% of AgNP inhibited the bacteria growth, which avoided the biodegradation of the PHBV matrix.