Abstract
The objective of this work was to analyze the shear strength of edge-glued panels (EGP) made from the H. dulcis Thunb. wood thermally modified by the VAP HolzSysteme® process. Initially, the Hovenia dulcis samples were heat-annealed by the VAP HolzSysteme® process, and then bonded with Resorcinol-formaldehyde (RF), Melamine-urea-formaldehyde (MUF), Isocyanate Polymer Emulsion (EPI) and Polyvinylacetate (PVAc) and submited to pre-treatments for dry, humid and external environment and without pre-treatment to evaluate the shear strength, 5th percentile and failure in the wood. It was observed a decrease in the shear strength of the thermorrectified H. dulcis wood for all adhesives. All adhesives obtained results superior to the minimum required by the standard EN13354 (2009) for the wood without pre-treatment as for the wood without thermoregulation as well as for the heat treated wood, and may be used for non-structural purposes. However, for the external environment (three cycles) only the MUF adhesive obtained value that meets the minimum standards of the standard, in this way, it is suggested to glue the EGP of H. dulcis without thermortification and with thermorrectification using the MUF adhesive, which has achieved better performance offering greater resistance in dry, wet and external environments.
Highlights
Heat treatment is a process of modifying wood pieces from the application of heat to high temperatures, which may vary between 180 and 260°C; below 140°C, the modifications occurred are irrelevant and, above 260°, the treatment starts to compromise the integrity of the samples (HILL, 2006)
The aim of the present study was to analyze the bonding quality of edge-glued panels (EGP) (Edge-Glued Panel) panels produced with Hovenia dulcis Thunb. wood without heat treatment and thermorectified bonded with four different adhesives
Esteves and Pereira (2009) corroborate that the hygroscopic sites that absorb the humidity of the environment and increase the equilibrium humidity of the wood are responsible for the chemical bond with the adhesive and, according to Carvalho et al (2015), the decomposition of these sites hinders the mechanical bonding of the adhesive with the wood, reducing the shear strength after heat treatments with higher temperatures
Summary
Heat treatment is a process of modifying wood pieces from the application of heat to high temperatures, which may vary between 180 and 260°C; below 140°C, the modifications occurred are irrelevant and, above 260°, the treatment starts to compromise the integrity of the samples (HILL, 2006). The heat treatment processes are those that have evolved the most in commercial terms in recent years. According to Hill (2006), among all the wood modification processes, heat treatment has the most commercially advanced technology, which proposes improvements in dimensional stability by reducing hygroscopicity, improving resistance to biodeterioration and weathering, in addition to changing the color of the FLORESTA, Curitiba, PR, v. The heat treatment is able to improve the qualities of commercial wood, producing alternative products for use and production of materials resistant to external use
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