Thermal Stability and Heat Transfer of Polyurethanes for Joints Applications of Wooden Structures

Wood characterized by desired mechanical properties and wood joining material is essential for creating wooden structures. The polymer adhesives are suitable for such applications due to the possibility of energy dissipation from stresses generated by wooden structures and the elimination of thermal bridging, which are common problems in metal joining materials. This research focuses on the thermophysical properties of the laboratory-prepared flexible and rigid polyurethanes to select an appropriate polymer adhesive. Our results showed that the highest thermal stability was in the case of the new PSTF-S adhesive, which reached 230 degrees C, but the lowest mass loss in the air environment was around 54% for the PS material. The mean thermal expansion coefficient for F&R PU adhesives was 124-164 center dot 10-6 K-1. The thermal diffusivity of examined adhesives varied between 0.100 and 0.180 mm2s-1. The thermal conductivity, depending on the type of polyurethane, was in the 0.13-0.29 W center dot m-1 center dot K-1 range. The relative decrease in thermal diffusivity after heating the adhesives to 150 degrees C was from 2% for materials with the lowest diffusivity to 23% for the PU with the highest value of heat transfer. It was found that such data can be used to simulate wooden construction joints in future research.