Shear strength of wood to wood adhesive based on palm kernel oil

A polyurethane adhesive system was prepared by reacting a resin consisting of palm kernel oil‐based polyester and dimethyl cyclohexanediamine with an aliphatic adduct based on 2,4‐diphenylmethane diisocyanate (MDI). Brushing technique was used for applying the adhesive (of thickness 0.05–0.10 mm) onto the wood substrate. Shear strength test for substrates that have been exposed to moisture and various degrees of heat was carried out. Collected data indicated that the adhesive exposed to heat at 70°C has the highest shear strength. At this point, the shear force was at the maximum of 2562 N with strength of 2.65 MPa. However, at higher testing temperature, there is a decrease in the shear force and strength of the adhesive. The presence of moisture, however, does not affect much on the shear strength. The morphological observations via optical microscope were made to explain the relationship of heat and moisture with the shear strength of the adhesive.