Investigations into the Influence of Temperature on the Tensile Shear Strength of Various Adhesives

Abstract

The temperature resistance of glued timber, which is crucial for glued wood construction, represents a significant assessment criterion. To gain insights into this aspect, this study utilized methods such as a shear strength test in accordance with EN 302-1:2013-06 under thermal loading (from 20 °C to 200 °C), and Differential Scanning Calorimetry (DSC) to determine the glass transition temperature (Tg). An increase in thermal load resulted in a decrease in shear strength and an increase in wood breakage. A hierarchy of adhesive groups was established based on strength performance and wood failure percentage (WFP) at 200 °C. Thermoset adhesives (MF: Melamine Formaldehyde, PRF: Phenol Resorcinol Formaldehyde) led the ranking, followed by elastomer adhesives (1C-PUR: One-Component Polyurethane, EPI: Emulsion Polymer Isocyanate), with thermoplastic adhesive (PVAc: Polyvinyl Acetate) last. Thermoset adhesives further cured under heat. PUR adhesives exhibited higher strength performance at 150 °C and lower temperatures.

Burning Properties of Combined Glued Laminated Timber

“…However, under applied heat flux, PUR adhesives might undergo softening or experience a reduction in bond strength.Contrarily, resorcinol-phenol formaldehyde (RPF) adhesives showcase notable high thermal stability, capable of enduring elevated temperatures compared with many other adhesive varieties. These adhesives retain their bond strength and structural integrity, even under significant heat exposure[50]. RPF adhesives exhibit robust resistance to softening, melting, or delamination when subjected to high temperatures, rendering them suitable for applications where fire resistance and heat stability are critical[51].…”