Navegando por Palavras-chave "Emulsion polymerization"

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    Effect of geometry and hybrid adhesive on strength of finger joints of Pinus elliottii subject to humidity and temperature
    (Taylor & Francis Ltd, 2018) Messmer, Nigel R. [UNIFESP]; Anjos, Erick G. R. [UNIFESP]; Guerrini, Lilia M. [UNIFESP]; Oliveira, Mauricio P. [UNIFESP]
    The optimized bonding of glued finger joints is required for structural and nonstructural applications. The use of nonspecific adhesives, combined with the joint geometry and exposure of joints to humidity and temperature, are factors that can compromise the durability of glued joints. The main objective of this study is the development of cross-linking poly(vinyl acetate) (PVAc) hybrid adhesive to produce nonstructural finger joints of Pinus elliottii with finger lengths of 6.5 and 4.5 mm. The adhesives were produced by emulsion copolymerization of vinyl acetate with n-butyl acrylate with different amounts of N-methylol acrylamide and blended with resorcinol-formaldehyde resin (RF) and aluminum chloride (AlCl3). The rheological behavior of adhesives was investigated. We found that the joint configuration and the exposition time employed influenced joint strength. The PVAc/RF adhesive showed a thicker bond line and consequent deeper penetration into the pores of the wood as verified by microscopy analysis. Statistically differences in bond strength of the adhesive joints were found with respect to different conditioning times and finger length. The highest values were exhibited by the joints produced with a finger length of 6.5 mm and glued with the hybrid adhesive (AD-4) than that joints produced with a finger length of 4.5 mm.
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    Effect of itaconic acid on the wet scrub resistance of highly pigmented paints for architectural coatings
    (Springer, 2011-07-01) Oliveira, Mauricio Pinheiro de; Silva, Caroline Reggiani; Guerrini, Lilia Mueller [UNIFESP]; BASF SA R&D; Universidade Federal de São Paulo (UNIFESP)
    This study investigates the influence of carboxylic monomers, such as itaconic acid (IA), on the colloidal properties of the latexes made by semi-continuous emulsion copolymerization of styrene (STy) with n-butyl acrylate (BA). A number of copolymerization runs were carried out with different IA concentrations. the effect of functional monomer on the overall conversion, the colloidal properties of the latexes, and the distribution of the carboxylic groups (buried, particle surface and aqueous phase) were examined. the carboxylic groups present in the latexes were analyzed using conductimetric and potentiometric titrations. the behavior of the IA on the wet scrub resistance of highly pigmented paints for architectural coatings was examined and correlated with the distribution of the carboxylic groups. the results obtained showed that the properties of highly pigmented paints are greatly dependent on the amount and distribution of the carboxylic groups. the carboxylic acid distributed in the aqueous phase has a strong influence on the wet scrub resistance and on the characteristics of the final products.
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    Síntese de látices com baixa concentração de compostos orgânicos voláteis (COVs): efeito das técnicas de redução dos COVs nas propriedades dos látexes e das tintas
    (Associação Brasileira de Polímeros, 2014-08-01) Oliveira, Maurício Pinheiro de [UNIFESP]; Silva, Caroline Reggiani da; Universidade Federal de São Paulo (UNIFESP); BASF S.A. Laboratório de Aplicações Técnicas
    The reduction of volatile organic compounds (VOCs) in the latexes produced by emulsion polymerization is a viable option, but it may compromise the performance of the latex in some situations. Different techniques for reduction of residual monomers and VOCs concentrations were studied for understanding the effect of these techniques and VOCs concentrations on the application properties of latexes and paints. Styrene/2-ethylhexyl acrylate latices functionalized with acrylic acid and acrylamide were produced by emulsion polymerization, followed by removal of residues and other VOCs with a chemical or physical technique, or with the combination of both. The effect of various parameters related to reduction techniques of VOCs, type of initiator, reducing agent and nitrogen stripping with steam were studied and correlated with the properties of latexes and paints. The combination of chemical and physical techniques was more effective for reducing the monomers and VOCs to latexes. The techniques employed for reduction of VOCs had a negative effect on the end-use properties of latex and paints. The abrasion resistance of the paint film was dependent on the technique employed and on VOCs concentration.