Abstract This work evaluated the influence of impregnation of boron compounds, in three concentrations, on Pinus sp. veneers, and its effect on the properties of plywood. The experiment was carried out in a completely randomized design, in a 3 × 3 + 1 factorial scheme, with three boron compounds (boric acid, borax, and disodium octaborate tetrahydrate) and three solution concentrations (1%, 3%, and 5%) plus the control. The panels were produced with three or five veneers, depending on the test, impregnated by dipping in boron compound solutions for 15 min and bonded with urea-formaldehyde adhesive. The apparent density, water absorption, thickness expansion, hygroscopicity, resistance to static bending (parallel and perpendicular to the grain) and shear strength were evaluted. All tests were carried out following the European Committee for Standardization, and the results were compared to the Brazilian Association of Mechanically Processed Wood requirements. Based on the results, it is recommended to use boric acid at a concentration of 1% or 3% or the other compounds tested at a concentration of 1%. sp veneers plywood design scheme borax tetrahydrate 1%, (1% 5% 5 control test ureaformaldehyde urea formaldehyde adhesive density absorption expansion hygroscopicity parallel grain evaluted Standardization requirements (1 (

Resumo Objetivou-se avaliar a influência da impregnação de compostos de boro, em três concentrações, em lâminas de Pinus sp., e seu efeito nas propriedades de compensados. O experimento foi realizado em delineamento inteiramente casualizado, em esquema fatorial 3 × 3 + 1, sendo três compostos de boro (ácido bórico, bórax e octaborato dissódico tetrahidratado) e três concentrações (1%, 3% e 5%) mais o controle. Os painéis foram produzidos com três ou cinco lâminas, encolados com uréia-formaldeído, com as lâminas impregnadas por imersão nas soluções de compostos de boro por 15 min. Foram avaliadas a densidade aparente, absorção de água, expansão de espessura, higroscopicidade, resistência à flexão estática (paralela e perpendicular à grã) e resistência ao cisalhamento. Todos os testes foram realizados de acordo com o Comitê Europeu de Padronização. Para o controle de qualidade, os resultados foram comparados com as exigências da Associação Brasileira de Madeira Processada Mecanicamente. Com base nos resultados, recomenda-se usar ácido bórico na concentração de 1% ou 3% ou os demais compostos testados na concentração de 1%. Objetivouse Objetivou se sp sp. compensados casualizado 1 tetrahidratado 1%, (1% 5% 5 uréiaformaldeído, uréiaformaldeído uréia formaldeído, formaldeído uréia-formaldeído min aparente água espessura higroscopicidade paralela grã cisalhamento Padronização qualidade Mecanicamente recomendase recomenda (1 (

Abstract The objective of the study was to identify the influence of heat treatment in obtaining condensable tannins compounds from Pinus spp bark residues for adhesive production. The heat treatments were: (a) bark without heat treatment (control); (b) bark exposed at 60 °C for 50 h dry; (c) bark exposed at 120 °C for 10 h in steam; (d) bark attached to the trunk exposed at 120 °C for 10 h in steam. For the chemical characterization of the material, the crust was ground and classified, the tannic compounds were extracted under reflux with distilled water for 2 h, and in addition, sodium carbonate and sodium sulphite salts were added, both at 5% in relation to dry mass. The properties of commercial tannin from Acacia mearnsii (acacia negra) were evaluated as the control. The tannin extraction process was carried out in an autoclave, and then used for the evaluation of properties such as viscosity, pH, gel formation time, solids content and density. It was determined that both the bark exposed at 120 °C for 10 h in steam and the bark adhered to the trunk (subjected to steam at 120 °C for 10 hours) for both salts, have higher tannin yields. Tannic extracts obtained from sodium carbonate have an alkaline structure, high viscosity, and shorter gel formation time. However, extracts obtained from sodium sulphite provide an acidic character and solids content close to those found in aqueous tannic extracts obtained from black acacia.

Resumen Se identificó la influencia del tratamiento térmico en la obtención de compuestos tánicos condensables a partir de residuos de corteza de Pinus spp para la producción de adhesivo. Los tratamientos térmicos fueron: (a) corteza sin tratamiento térmico (testigo); (b) corteza expuesta a 60 °C durante 50 h en seco; (c) corteza expuesta a 120 °C durante 10 h en vapor; (d) corteza adherida al tronco expuesta a 120 °C durante 10 h en vapor. Para su caracterización química, la corteza fue molida y clasificada. Se extrajeron los compuestos tánicos mediante reflujo con agua destilada durante 2 h; se adicionaron sales de carbonato de sodio y sulfito de sodio, ambos a 5% en relación con la masa seca. Para el testigo fueron evaluadas las propiedades del tanino comercial de Acacia mearnsii (acacia negra). El proceso de extracción de taninos fue realizado en autoclave y se evaluaron las siguientes propiedades: viscosidad, pH, tiempo de formación de gel, contenido de sólidos y densidad. Tanto la corteza expuesta a 120 °C durante 10 horas en vapor como la adherida al tronco sometida a 120 °C a vapor durante 10 h, para ambas sales, exhibieron los mayores rendimientos de taninos. Los extractos tánicos obtenidos a partir de carbonato de sodio presentaron una estructura alcalina, alta viscosidad y menor tiempo de formación de gel. Sin embargo, los extractos obtenidos a partir de sulfito de sodio proporcionaron un carácter ácido y contenido de sólidos próximos a los encontrados en los extractos tánicos acuosos obtenido de la acacia negra.