Interface madeira-adesivo e resistência de juntas coladas com diferentes adesivos e gramatura

• Autor(a) principal: Bianche, Juliana Jerásio
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/603
• topic: Madeira - Adesivo; Mamona; Silicato; Wood - Adhesive; Castor; Silicate; CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL::TECNOLOGIA E UTILIZACAO DE PRODUTOS FLORESTAIS

Studies involving wood-adhesive interactions in species of eucalyptus and pine glued with adhesives based on castor beans and silicate are scarce and knowledge about them is needed. This study aimed to analyze the wood-adhesive interface and the joints' resistance bonded with different adhesives and weight. Five adhesives [castor beans , sodium silicate, modified silicate, PVA (Polyvinyl acetates), and resorcinol- formaldehyde], three weights (150 g/m 2 , 200 g/m 2 , and 250 g/m 2 ), and two species (Eucalyptus sp. and Pinus sp.) were used. The adhesives properties (viscosity, solids content, pH, and working time), the contact angle of the adhesives, and the wood s properties (buffering capacity and pH, anatomical analysis, chemical analysis, and basic density) were determined. Collages and evaluation of shear strength were made in the glue line from the bonded joints. The techniques of optical and scanning electron microscopy were used to study the wood-adhesive interface. The PVA adhesive showed higher viscosity and greater contact angle and lower wettability and humectancy. However, the castor beans adhesive showed higher solids content, less working time, and lower contact angle; it was the adhesive with greater wettability and humectancy. Chemical bonds originated from polymerization of resorcinol- formaldehyde and bicomponent of castor beans adhesives conferred to them larger strength in the glue line. The weight and adhesive interaction showed significant effect on the values of shear strength and failure percentage of bonded eucalyptus joints in dry condition with no isolated effects on adhesive and weight. The type of adhesive that was used had significant effect on the values of shear strength and failure percentage (wet condition) of glued joints of eucalyptus and pine. Castor beans and resorcinol-formaldehyde adhesives showed the highest values of shear strength on the glue line and failure on the wood. Adhesives of castor beans, PVA, and resorcinol penetrated the woods, filling cell cavities adjacent to the main glue line in eucalyptus (vessels, rays, parenchyma) and pine (cells of early and late wood, xrays, and pits). Castor beans adhesive showed performance for bonding eucalyptus and pine. Further studies are recommended for analyzing the relationship among different proportions of polyol/isocyanate, to evaluate the strength of glued wood, and to analyze alternatives that can increase the working time of the castor beans adhesive so as to facilitate the bonding process of the wood.