Adhesion and Cohesion Strength of Phenol-Formaldehyde Resin Mixed with Different Types and Levels of Catalyst for Wood Composites

Phenol-formaldehyde (PF) resin is one of the most well-known adhesives for exterior use. PF adhesive is one of the commercial thermoset polymers that is used extensively due to its many benefits. This study investigated the influence of different types and levels of catalysts, i.e., NaOH and CaCO3 at 1% and 5% based on the solids content of PF resin on the adhesive properties, adhesion, and cohesion strength of PF resin. The results show that the catalyst type significantly influenced the PF adhesive viscosity and pH. Furthermore, the catalyst level significantly affected the PF adhesive’s solids content, viscosity, and gelation time. The cohesion strength of PF-CaCO3-1% was more significant than the PF control at 75 °C. According to the DMA analysis, the mixed PF-NaOH-5% provided the highest storage modulus, followed by the PF-CaCO3-1%, with values that were not statistically different from one another. The adhesion strength of PF-CaCO3-1% was the highest, whereas the adhesion strength of the PF control was the lowest, as confirmed by the cohesion strength. According to the findings, adding CaCO3-1% as a catalyst of PF resin would result in better adhesive adhesion and cohesion properties for wood composites in the future.