Propriedades de painéis OSB fabricados com flocos esterificados

• Autor(a) principal: Cabral, Carla Priscilla Távora
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/574
• topic: OSB; Esterificação; Eucalipto; Pinus; OSB; Esterification; Eucalyptus; Pinus; CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL::TECNOLOGIA E UTILIZACAO DE PRODUTOS FLORESTAIS

There is at present an incessant struggle in the search for new technologies that enable the use of various types of raw materials, principally residues, in the manufacture of high quality products that could satisfy the demands of the consumer market. In the market of structural panels, there thus appear the types of OSB that compete with plywood. Aiming to improve some of the characteristics of the panels, the present work shows the technical viability of the use of wooden flakes when modified chemically, in order to improve the dimensional stability of OSB panels. The species used in this work were the genus Eucalyptus (Eucalyptus grandis) and the genus Pinus (Pinus caribeae var. hondurensis), originating from the city of Viçosa, Minas Gerais, with the respective densities: 0.51 and 0.49 g/cm ³. The OSB panels of these woods were manufactured from flakes originating from planks and boards, dimensions 20.00 x 0.46 x 90.00 mm, and with pre-established density values of 0.70 g/cm³). The flakes were classified by size in manual sieves. The adhesive used for the production of the OSB panels was phenol formaldehyde employed in the proportion of 8% of solids in relation to the dry mass of flakes. The panels had in their composition 50% untreated flakes and 50% flakes esterified by phtalic, maleic and acetic anhydrides. Since the first two anhydrides were solid, there was the need of solubilizing in organic solvents such as ethylic alcohol and ethyl ether for the phtalic anhydride, and ethyl acetate and acetone in the case of maleic anhydride. In case of the acetic anhydride, the acetic and phtalic acids were employed to catalyze the reaction. The panels were pressed at a temperature of 140°C and 32 kgf/cm² of pressure, and were tested according to the standards of the ABNT (NBR 14810-3) of 2002 and ASTM-D 1037 of 1991. The results were compared using the standards ANSI/A 208.1 (1993) and CSA 0437-93 (1993). For the statistical analysis the test of averages and the Tukey Test were used, at a level of significance of 5%. The panels that presented the highest averages for absorption of water vapor were those manufactured with flakes of Pinus caribeae, esterified with maleic anhydride and acetone, for 24 hours, whereas, those which presented the lowest averages were those made with flakes of the species Eucalyptus grandis, treated with acetic anhydride and acetic acid for 3 hours. For the linear expansion test, the panels that presented greater dimensional stability were those manufactured with wood of the species Eucalyptus grandis, treated with acetic anhydride and acetic acid. In the absorption of water within 2 hours, the panels that presented the lowest averages were those manufactured with flakes of Eucalyptus grandis, esterified by maleic anhydride with acetone for 48 hours. In the absorption of water for 24 hours, the panels that presented the best results were those manufactured with the species Pinus caribeae, esterified with maleic anhydride, acetic anhydride with acetic acid. For Janka hardness, the largest averages obtained were from the panels made with flakes treated with acetic anhydride and phtalic acid. In the perpendicular tensile strength and longitudinal compression, the lowest averages were for the panels made with acetic anhydride and acetic acid. For the moduli of rupture and elasticity, in the longitudinal sense, the lowest averages were also for the panels made with acetic anhydride and acetic acid. The acetylation employing acetic acid influenced in a positive way the following physical properties: adsorption of water vapor, expansion in thickness and linear expansion in the OSB panels, making those of acetylated flakes more dimensionally stable. Nevertheless, there was a loss of strength in mechanical properties such as screw withdrawal, longitudinal compression and perpendicular tensile strength. When the acetic anhydride was associated with phtalic acid, most of the mechanical properties had a strength gain. The panels manufactured with acetylated flakes, treated with maleic and phtalic anhydrides, were also influenced by the type of solvent and reaction time, improving and/or making their physical and mechanical properties worse. On the whole, the panels presented satisfactory average values. Beyond this, for some mechanical tests, the results were well above the minimum values established by the standard, for most of the tests. This shows that these anhydrides present a great potential to be explored by the panel industries, requiring, however, more research.