Production of plywood panels from Pinus taeda using veneers of differing densities and phenol-formaldehyde resin with high and low molecular weights

Abstract

This study aimed to evaluate the bonding quality of plywood panels from Pinus taeda using low and high molecular weight phenol-formaldehyde resin and veneers from three different density classes. The experiment consisted of six treatments, each of which produced three panels (replicates). Tests were conducted to evaluate glue line strength to shear stress after two boiling cycles and after 24 hours of cold water immersion. Also determined was the percentage of defects in wood samples. Results indicated that the density classes being assessed differed statistically. However, no significant difference was found between panels produced with high and panels produced with low molecular weight resin as to the mean values of glue line strength, whether subjecting them to two boiling cycles or after 24 hours of cold water immersion. Interactions between different density classes and adhesive formulations were found not significant either. Low molecular weight resin (BPM) and panels produced with higher density veneers were found to have better behavior, regarding both bonding strength and percentage of defects. It was concluded that the bonding quality of plywood panels from Pinus taeda was satisfactory after using different densities of veneer and also high and low molecular weight phenolic resins. All treatments were found to comply with minimum requirements established in European standard EN 314-1/1993, which addresses bonding quality of plywood panels.Key words: Plywood panels, Pinus taeda, veneers, phenol-formaldehyde. PRODUÇÃO DE PAINÉIS COMPENSADOS DE Pinus taeda COM LÂMINAS DE DIFERENTES DENSIDADES E RESINA FENOL-FORMALDEÍDO COM ALTO E BAIXO PESO MOLECULAR RESUMO: Neste trabalho, objetivou-se avaliar a qualidade da colagem de painéis compensados de Pinus taeda, produzidos com resina fenol-formaldeido de alto e baixo peso molecular, e lâminas de três diferentes classes de densidades. O experimento foi organizado em seis tratamentos, e para cada tratamento foram produzidos três painéis (repetições). Os ensaios de resistência da linha de cola aos esforços de cisalhamento foram realizados após dois ciclos de fervura e após 24 horas de imersão em água fria. Determinou-se, também, a porcentagem de falhas na madeira. Os resultados indicaram que as classes de densidade são

Water Resistant Plywood of Increased Elasticity Produced From European Wood Species

“…Investigations by Bal andBektas (2012, 2014) and Bal (2016) prove that mechanical properties (bending strength and modulus of elasticity) of LVL and plywood manufactured from eucalyptus are comparable to those made from beech. Research works conducted by Iwakiri et al (2006Iwakiri et al ( , 2013 also confirm that various types of eucalyptus wood can be successfully applied in the production of plywood. Satisfactory results have also been attained for three kinds of pine, i.e.…”

“…It depends on the characteristics of veneer surface, their moisture content, thickness, species and structure of wood, type and amount of adhesive and pressing conditions (Aydin et al 2006, Bekhta et al 2009, Šrajer et al 2013. Thicker veneers and those of lower density tend to absorb more resin and, as a result, the curing process occurs in the veneer rather than in the glue line (Muniz et al 2013, Muhammad-Fitri et al 2018. Taking into account the fact that the investigated veneers were made from various wood species of various density and thickness, the produced plywood was subjected to investigations on bond quality by determining their shear strength after boiling and soaking tests.…”