An experimental study was carried out to develop and examine the properties of a new type of structural insulated panel (SIP). SIP prototypes conducted from this research consisted of insulated foam manufactured from natural rubber filled with wood particles as the core layer and three kinds of commercial wood-composite boards (plywood, cement particleboard, and fiber-cement board) as the surface layers. Polyurethane was used as an adhesive bond between the surface and the core layer. This preformed panel was placed into a clamping device and compressed until adhesive curing was achieved. The physical and mechanical properties of the SIP prototypes were consequently evaluated. The test results indicated that the types of surface layer materials played a significant effect on the SIP properties. The SIP covered with cement particleboard and fiber-cement board revealed high mechanical properties and high water resistance. The SIP prototype covered with plywood showed desirable properties (such as low density, high resistance of screw withdrawal, and low thermal transmittance). However, high water absorption and low fire resistance were drawbacks of the SIP covered with plywood. These properties should be improved.

The strength of an adhesive joint plays a major role in the implementation of engineering wood products; therefore, joint performance receives intense scrutiny. This study investigated a wooden adhesive joint, made from densified wood, the performance of which was dramatically enhanced. The wood sample was developed by performing mechanical compression and polymer impregnation on rubberwood. This treated rubberwood was additionally prepared by simple surface sanding prior to jointing. The highest wettability was found on surfaces sanded with the largest grit sandpaper. Consequently, glueline thickness increased with progressively larger grit (smaller grit number) sandpaper. In addition, the maximum shear strength for the joint made from the densified rubberwood was greater than that of that made from the original one, by 40%. Surprisingly, with the optimal sanding treatment, the shear strength of the wooden joint gradually increased with an increase in the density of the densified rubberwood from 1.05 to 1.30 g/cm³. Moreover, the rate of wood failure also increased throughout the stated density range.