SHEAR STRENGTH IN THE GLUE LINE OF Eucalyptus sp. AND Pinus sp.WOOD

Abstract

-To evaluate the adhesive efficiency on the union of glued joints in a particular temperature and humidity conditions for a specified time the adhesive must be submitted to specific load tests, such as shear in the glue line. The objective of this study was to evaluate the shear strength in the glue line of Eucalyptus sp and Pinus sp.woods. Five adhesives (castor oil, sodium silicate, modified silicate, , PVA and resorcinolformaldehyde), three weights (150 g/m 2 , 200 g/m 2 , and 250 g/m 2 ) and two species (Eucalyptus sp. and Pinus sp.) of wood were used. Twelve specimens were obtained from each repetition per treatment, corresponding to 108 specimens that were conditioned at a temperature of 23 ± 1°C and relative humidity of 50 ± 2%. The interaction between the weight and type of adhesive was significant for the shear strength in the glue line of eucalyptus wood. However, no interaction between the weight and the adhesive was found for pinus, only the isolated from the adhesive effect. Chemical bonds originated in the polymerization of resorcinolformaldehyde adhesives and castor bi-component conferred upon these adhesives the greatest resistance in the glue line. Castor and resorcinol-formaldehyde adhesives showed the highest shear strength values in the line of glue and wood failure. Castor adhesive presented satisfactory performance for bonding of eucalyptus and pine woods.Keywords: Adhesives; Collage; Weight. RESISTÊNCIA AO CISALHAMENTO NA LINHA DE COLA DAS MADEIRAS DE Eucalyptus sp. E Pinus sp.RESUMO -Para avaliar a eficiência do adesivo na união das juntas coladas, sob uma determinada temperatura e condições de umidade, durante um tempo específico o adesivo deve ser submetido a testes de carregamento, como, por exemplo, o teste de cisalhamento na linha de cola. Portanto, o objetivo deste trabalho foi avaliar a resistência ao cisalhamento na linha de cola de amostras de madeiras de Eucalyptus sp. e Pinus sp. coladas com cinco diferentes adesivos (Bicomponente de mamona, silicato de sódio, silicato modificado, PVA e resorcinolformaldeído) e três gramaturas (150 g/m 2 , 200 g/m 2 e 250 g/m 2 ) . Foram obtidos 12 corpos de prova para cada repetição por tratamento, correspondendo a 108 corpos de prova por tratamento, totalizando 3240 corpos de prova, que foram condicionados a temperatura de 23+1º C e umidade relativa de 50 + 2%. Após atingirem a umidade de equilíbrio higroscópico, a resistência ao cisalhamento e a falha na madeira foram determinadas, nas condições seca e úmida. Foram ensaiados doze corpos-de-prova, sendo nove na condição seca e três na 1110Revista Árvore, Viçosa-MG, v.40, n.6, p.1109-1117, 2016 BIANCHE, J.J. et al.condição úmida. As ligações químicas originadas na polimerização dos adesivos de resorcinol-formaldeído e bicomponente de mamona conferiram a estes adesivos maiores resistências ao cisalhamento na linha de cola e falha na madeira.

Efficiency of castor oil-based polyurethane in the production of plywood panels

“…When submitted to the cold water condition they obtained for panels with 150 g / m 2 of adhesive shear strength of 2.76 MPa and 10.9% of failure in the wood; in panels with a glue line grammage of 200 g / m 2 the shear strength was 3.12 MPa and the wood failure was 20.3%. In panels whose glue line was thicker, 250g / m 2 , the authors noticed a reduction in shear strength and failure of the wood in both conditions (BIANCHE et al, 2016) The results obtained by Bianche et al (2016) and Dias and Lahr (2004) suggest that the higher weight of glue line, to an optimum point, allied to the characteristics of the wood used influence the shear strength, as well as the percentage of wood failure.…”

“…The plywood panels of the Eucalyptus grandis with adhesive castor oil-based polyurethane with adhesive grammage of 250 g/m 2 studied by Dias and Lahr (2004) show presented a shear stress of 3.1 MPa and 78% of failure in the wood in dry condition, 2.7 MPa and 32% of failure in the wood when wet and 1.9 MPa and 16% of failure in the wood after boiling. Bianche et al (2016) analyzed panels produced with Pinus sheets and adhesive polyurethane derived from castor oil with adhesive grammage of 150 and 200 g / m 2 . Considering glue line 150 g / m 2 , in dry condition, the shear strength was 4.67 MPa and the wood failure was 36%; already in line of glue grammage of 200 g / m 2 the resistance to the shear was of 4.24 MPa and the failure in the wood of 48%.…”

Collage Quality of Brazilian Woods for Use in Glued Laminated Timber Beams

“…Notes: an average of 7 specimens was considered for each glulam beam. fv,m= average value of shear strength of the glue lines of the beams; FW= wood failure (ImageJ); CV= coefficient of variation (DP/mean*100); DP = standard deviation; fv,k = characteristic value of shear strength according to [3]. Notes: an average of 7 specimens was considered for each glulam beam.…”

“…There are several factors that can influence the wood glue quality response with structural adhesives. According [3] an important factor is the density of the wood. Denser woods tend to be more difficult for the adhesive to penetrate.…”

“…On the other hand, using low viscosity adhesives can result in a hungry glue line or excessive absorption by the wood [3]. The Brazilian test method [1] for evaluating the quality of bonding is based on the delamination and shear strength 1 Julio Cesar Molina, EESC/USP -São Carlos School of Engineering of the University of Sao Paulo, Brazil, julio.molina@usp.br 2 Natália Andrade Bianchi, FEG -University of Sao Paulo State, Brazil, nataliabianchi95@gmail.com 3 Felipe Dutra Lisboa, UNESP -University of Sao Paulo State, Brazil, felipe.lisboa@unesp.br tests of the glue lines, proposed by the European standard [2] for the external environment. This study proposed the evaluation of the bonding quality of glulam beams based on the recommendations of the Brazilian test method [1].…”