Shear strength of Scots pine wood and glued joints in cold climate

The impacts of cold temperatures on the shear strength of Scots pine (Pinus sylvestris) joints (150 mm x 20 mm x 10 mm) glued with seven commercially available adhesives were studied in this work. The adhesives used here were: polyurethane (PUR), polyvinyl acetate (PVAc), emulsion-polymer-isocyanate (EPI), melamine-formaldehyde (MF), phenol-resorcinol-formaldehyde (PRF), melamine-urea-formaldehyde1 (MUF1), and melamine-urea-formaldehyde2 (MUF2). The cold temperatures investigated here were: 20, -20, -30, -40 and -50 °C. Generally, within the temperature test range, the shear strength of Scots pine solid wood and wood joints resisted more temperature effects than Norway spruce. As the temperature decreased, only some of the joints shear strength decreased significant. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. MF adhesive responded to temperature changes in a similar manner to that of the PUR and PVAc adhesives. The shear strengths of wood joints with PRF and EPI adhesives were more sensitive to temperature change. For dynamic tests of shear strength, the values for 12 hours and 6 days tests under cycled of temperature (-20°C and 0°C) were compared. For 6 days tests, the values for the various types of the adhesives are lower than for 12 hours. Therefore, the duration of the samples subjected to the same temperature had significant impact on shear strength. PUR is the most stable adhesive; MUF and PRF have significant decrease.Validerad; 2016; Nivå 2; 20150827 (aliwan)