Abstract
The influence of artificial ageing on bonded heat-treated spruce lamellas was investigated. Heat-treated spruce lamellas with different degrees of thermal modification were bonded with PVAc and MUF and then exposed to 500 artificial weathering cycles, combined with rain, UV and IR radiation. The colour change of the exposed surface, weight change, delamination of the bonded joints and adhesive bond strength were measured. Artificial weathering caused cracking and delamination of the bonded joints and reduced the bond strength of both adhesives. The results show that delamination was higher for PVAc adhesive than MUF, but increased for both adhesives with the temperature of heat treatment of wood. The shear strength of bonds on the exposed side of the samples after the artificial weathering was lower than the average strength of the whole sample.
Highlights
The results show that delamination was higher for PVAc adhesive than MUF, but increased for both adhesives with the temperature of heat treatment of wood
Studies had shown that heat treated (HT) wood can be adequately bonded to most industrial wood adhesives with some modifications of the bonding process and/or adhesive
The spruce wood lamellae (Picea abies Karst) were heat treated at five different temperatures: 150, 170, 190, 210, 230 °C using the method of heat treatment with initial vacuum phase (Rep et al 2004)
Summary
Thermal modification of wood can influence the gluing process with adhesives (Kariz, 2011) and reduce the performance of glued joints (Sernek et al, 2008). The shear strength of glued joints is usually reduced due to the lower strength of the modified wood (Esteves and Pereira, 2009) and the lower adhesion to the modified wood surface. Studies had shown that heat treated (HT) wood can be adequately bonded to most industrial wood adhesives with some modifications of the bonding process (longer pressing time, lower wood moisture content) and/or adhesive . Kariz, Kitek Kuzman, Sernek: Effect of Artificial Ageing on Adhesive Bonds. What is less known is how the bonds in heattreated wood change over time due to modified wood properties
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