Polycaprolactone (PCL) polyol was prepared by a ring opening polymerization of ε-caprolactone initiated by palm kernel oil (PKO) based polyol and 1,6-hexanediol to form a PCL/PKO based polyol. The properties of polyol were varied by their initiator:co-initiator weight ratio. The completion of polyol formation was characterized through Fourier Transformation Infrared (FTIR) spectroscopy. Other parameters such as acid number and hydroxyl number of polyol were also studied to monitor the progress of reaction. FTIR results showed the significant changes particularly for the OH and C=O stretching peaks.

Polyurethane (PU) adhesives were prepared from three different polyols based on polycaprolactone (PCL)/palm kernel oil (PKO) with an aromatic and cycloaliphatic diisocyanate. The adhesives were characterized through Fourier Transformer Infrared (FTIR) spectroscopy in order to ensure the formation of urethane and the completeness of polymer reaction. The effects of NCO/OH ratios and types of diisocyanate on PU adhesive strength were investigated. The adhesive strength of metal to metal bonding was determined by single lap shear joint testing. The correlation between crosslinking of PU network and adhesive strength was also studied by performing swelling tests.