Temperature resistance of spruce joints bonded with four adhesives and correlation with thermal behaviour of wood and thin adhesive films

Temperature resistance of spruce joints bonded with four adhesives and correlation with thermal behaviour of wood and thin adhesive films

Článek WoS

This paper investigates the temperature resistance of the load-bearing elements of bonded spruce joints subjected to static tensile shear stress immediately after thermal exposure. Four types of adhesives were used: polyurethane, melamine-urea-formaldehyde, resorcinol-phenol-formaldehyde, and epoxy. The joints were exposed to temperatures of 100, 120, 140, 160, and 180 °C for 1 and 2 hours. To evaluate the influence of temperature on potential wood degradation and its effect on the thermal resistance of bonded joints, the wood itself was subjected to the same conditions and tests as the bonded joints. To isolate the effect of the adhesives, thin films were prepared and their change in stiffness during heating up to 180 °C was measured using dynamic mechanical analysis. None of the adhesives were fully cured, and post-curing led to an increase in storage modulus and, in the case of phenolic adhesives, significant shrinkage of the films. The strength of all joints decreased with increasing temperature. A continuous decrease was observed in epoxy joints, whereas the other joints exhibited fluctuations in strength. The main cause is a change in the structure of the adhesive; at temperatures above 140 °C, the strength of the wood is also reduced (a significant drop after 2 hours). PUR-bonded joints exhibited the highest strength at 20 °C and after thermal exposure. In respect of the decrease in strength, a temperature of 100 °C already appears to be critical. Adhesives began to show thermal degradation at 140 °C, which led to an increased incidence of adhesive failure in the joints. Phenolic and PUR adhesives demonstrated considerable thermal resistance, and the duration of thermal exposure also had a significant effect.

This paper investigates the temperature resistance of the load-bearing elements of bonded spruce joints subjected to static tensile shear stress immediately after thermal exposure. Four types of adhesives were used: polyurethane, melamine-urea-formaldehyde, resorcinol-phenol-formaldehyde, and epoxy. The joints were exposed to temperatures of 100, 120, 140, 160, and 180 °C for 1 and 2 hours. To evaluate the influence of temperature on potential wood degradation and its effect on the thermal resistance of bonded joints, the wood itself was subjected to the same conditions and tests as the bonded joints. To isolate the effect of the adhesives, thin films were prepared and their change in stiffness during heating up to 180 °C was measured using dynamic mechanical analysis. None of the adhesives were fully cured, and post-curing led to an increase in storage modulus and, in the case of phenolic adhesives, significant shrinkage of the films. The strength of all joints decreased with increasing temperature. A continuous decrease was observed in epoxy joints, whereas the other joints exhibited fluctuations in strength. The main cause is a change in the structure of the adhesive; at temperatures above 140 °C, the strength of the wood is also reduced (a significant drop after 2 hours). PUR-bonded joints exhibited the highest strength at 20 °C and after thermal exposure. In respect of the decrease in strength, a temperature of 100 °C already appears to be critical. Adhesives began to show thermal degradation at 140 °C, which led to an increased incidence of adhesive failure in the joints. Phenolic and PUR adhesives demonstrated considerable thermal resistance, and the duration of thermal exposure also had a significant effect.

spruce, adhesive, temperature resistance

spruce, adhesive, temperature resistance

VANĚREK, J.; BÁLKOVÁ, R.; BĚŤÁK, A.; LACIKOVÁ, P.

25.03.2026

Springer

European Journal of Wood and Wood Products

84

49

Spolková republika Německo

18

https://rdcu.be/e99f2