Navegando por Palavras-chave "Polymer Synthesis"

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    Desenvolvimento De Látexes Híbridos De Estireno/Acrilato De N-Butila/Lignina Via Polimerização Em Emulsão E Miniemulsão
    (Universidade Federal de São Paulo (UNIFESP), 2017-03-03) Messmer, Nigel Roderick [UNIFESP]; Oliveira, Mauricio Pinheiro De [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The use of Kraft Lignin (KL) to produce hybrid latexes has received much attention in recent years because it is derived from renewable resources, is available in large quantities from the pulp and paper industry and also contributes to reducing the final cost of the product. This study’s objective is to develop organic/organic hybrid latex by emulsion and miniemulsion polymerization techniques to synthesize copolymers of styrene (St), n-butyl acrylate (ABu), and methacrylic acid (AMA) with different concentrations of KL. The study intends to understand the effect of the KL on the properties not only of the latexes, but also on the copolymers themselves. The emulsion polymerizations were conducted varying 2 parameters: different concentrations of KL (0; 0,5; 1,0; and 2,0%), and different intervals of time between shots. The resulting latexes were characterized in relation to global conversion, average particle size and particle size distribution, zeta potential, residual monomer concentration and coagulum concentration, latex stability and particle morphology. The polymers were evaluated through thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy FTIR), nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC) and waterabsorption as well relative hardness. Latexes with different concentrations of KL were produced via emulsion and miniemulsion polymerization. Independent of the polymerization technique, increases in KL concentration cause reduction of: overall conversion, reaction velocity, particle diameter and surface tension. Further, we observed that increasing the reaction time had a small effect on the final overall conversion though insufficient to achieve conversion levels exhibited in reactions without the presence of KL. Among the concentrations tested, the greatest concentration of KL, 2%, exhibited the greatest effect on the properties of the latexes and the copolymers (morphology, water-resistance, and molar mass). The presence of KL also altered the color of the latexes and of the copolymers limiting its use in certain industrial applications.
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    Síntese De Nanopartículas Poliméricas Com Estímulo Resposta Ao Ph Obtidas Via Polimerização Em Emulsão Para Produção De Carpete Reciclável
    (Universidade Federal de São Paulo (UNIFESP), 2017-08-30) Cobianchi, Andreia Ferreira [UNIFESP]; Oliveira, Mauricio Pinheiro De [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Automotive and industrial carpets are produced by impregnating polyethylene terephthalate (PET) fibers with aqueous dispersion copolymers in order to fix the fibers, provide dimensional stability and abrasion resistance. Currently, approximately 35% of the national carpet production is composed of chips and leftovers from the manufacturing process, which are incinerated or disposed of in landfills because it is impossible to remove the polymers used in the impregnation of the carpet fibers. The objective of this work is to develop polymeric nanoparticles with stimulus pH response to produce industrial carpets, aiming at the recycling of polymer fibers and nanoparticles for the production of new materials. Polymeric nanoparticles were obtained by emulsion copolymerization of styrene (STy), n-butyl acrylate (Abu) and acrylonitrile (ACN) in the absence of emulsifier. As a polymerization stabilizer, a copolymer of poly (methacrylic acid-co-methacrylamide) obtained via copolymerization of methacrylic acid (AMA) with methacrylamide (MA) was used. The copolymers obtained were characterized in relation to the overall conversion, average particle diameter, zeta potential, viscosity, molar mass, molar mass distribution (MWD) and reemulsification of the polymer film at different values of pH. The industrial carpets were produced by total impregnation and evaluated in relation to reemulsification of the polymer film under different pH values. Stabilizers of poly (methacrylic acid-comethacrylamide) with molecular weigh less than 10,000 g/mol showed the most promising results to produce the nanoparticles with response stimulus and mean diameter 80 nm in the absence of emulsifier, allowing the re-emulsification of the polymeric film when in contact with alkaline solution.