No abstract

Poly(vinyl alcohol) (PVOH) was obtained from the alkaline hydrolysis of poly(vinyl acetate) (PVAc). Nonwoven membranes (mats) of PVOH nanofibers were produced by electrospinning of solutions of PVOH in water with and without aluminum chloride. The concentration of the PVOH/water solution was 12.4% w/v. The morphology of the mats was analyzed by scanning electron microscopy (SEM). The thermal properties and the degree of crystallinity of the nanofibers were measured by differential scanning calorimetry (DSC); the crystal structure of the mats was evaluated by wide-angle X-ray diffraction. The best nanofibers were obtained by electrospinning the PVOH/ water solution with aluminum chloride (45% w/v) in which an electrical field of 3.0 kV/cm was applied. It was observed that the addition of the aluminum chloride and the increase in the applied electrical field decreased the number-average nanofibers diameters. The mats without aluminum chloride had higher melting temperatures and higher degrees of crystallinity than the mats with the salt. The crystal structure of the mats was found to be monoclinic; however, the mats were neither highly oriented nor have a high degree of crystallinity.

This study investigates the influence of carboxylic monomers, such as itaconic acid (IA), on the colloidal properties of the latexes made by semicontinuous 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.

Resumo: Neste trabalho foi sintetizado o poli(álcool vinílico) (PVOH) através da hidrólise alcalina do poli (acetato de vinila). As mantas nanofibrílicas de PVOH foram processadas através da eletrofiação das soluções de PVOH/água e PVOH/ água/cloreto de alumínio, ambos na concentração de 12,4% m/v. A morfologia das fibras foi analisada através da microscopia eletrônica de varredura (MEV). O grau de cristalinidade dos materiais foi medido por calorimetria exploratória diferencial (DSC) e difração raios x de alto ângulo (WAXD). Os efeitos da tensão elétrica aplicada e da presença de cloreto de alumínio foram verificados na morfologia e no diâmetro médio das fibras de PVOH. Os resultados obtidos mostraram que as fibras de PVOH na ausência do cloreto de alumínio apresentaram diâmetros maiores do que na presença do cloreto de alumínio devido à diferença observada na condutividade elétrica das soluções. Variando-se a tensão de 15 a 18 kV foi observado um decréscimo 140 nm no diâmetro médio das fibras. A cristalinidade das fibras eletrofiadas com sal e sem sal é menor do que para o PVOH isotrópico. Palavras-chave: Eletrofiação, poli(álcool vinílico), nanofibras. Electrospinning of Aqueous Solution of Poly(vinyl alcohol)Abstract: Poly(vinyl alcohol) (PVOH) was prepared by solution polymerization of vinyl acetate. PVOH nanofibers were produced by electrospinning in aqueous solution of 12.4% w/v with and without 1% v/v of aluminum chloride. The nanofiber morphology was observed using a scanning electron microscope (SEM). The degree of cristallinity was measured by differential scanning calorimetry (DSC) and wide-angle x ray diffraction (WAXD). The effects of electric voltage and the addition of aluminum chloride were verified on the morphology and average fiber diameter. The results showed that the PVOH nanofibers without aluminum chloride had diameters higher than the nanofibers prepared with the salt due to the different electrical conductivity of the solutions. A decrease of 140 nm on the average diameter fibers was observed when the voltage varied from 15 to 18 kV. The nanofibers crystallinity with and without salt was lower than the isotropic PVOH.

The introduction of non-modified kraft LignoBoost® lignin (KL) to produce polymer hybrid latex has received much attention in recent years because it is derived from renewable resources. The focus of this work is to develop a polymer hybrid latex by emulsion and miniemulsion copolymerization of styrene with n-butyl acrylate and methacrylic acid in the presence of different concentrations of KL furnished by the pulp and paper industry. The study intends to substitute a styrene in the system to understand the effect of non-modified KL on the properties not only of the latexes, but also on the copolymers themselves. Each polymerization was carried out by shot-process of tertbutyl hydroperoxide and sodium formaldehyde sulfoxylate as the redox system. The polymer latexes were characterized in relation to overall conversion, particle diameter, particle morphology, coagulum formation, surface tension, zeta potential, and atomic force microscopy.The polymers were evaluated through gel permeation chromatography, water absorption, and thermal properties. The results show that the addition of non-modified KL results in inhibition of the polymerization and that KL acts as a colloid stabilizer. Small particles were generated in the initial stages of the polymerizations. The presence of the KL altered the color of the latexes; the increase in KL concentration resulted in increase in the absorption of water of the polymer films; the increase in KL concentration resulted in decrease of the molar mass of the copolymers.