Cure Behaviour of a Fast Reacting Green Polyurethane Adhesive System

Abstract

Cure behaviour analysis of a fast reacting thermosetting system is critical in the manufacturing process of laminated composites. This study focuses on the investigation of the cure kinetics of polyurethane (PU) adhesive based on green polycaprolactone (PCL) polyol for aluminum laminated composites. Four different formulations of polyurethane adhesive by varying the NCO: OH ratio (1.3, 1.5, 1.7, 2.0) which were prepared from PCL polyol with a blend of aromatic and cycloaliphatic diisocyanate. The cure kinetics study was conducted by Differential Scanning Calorimetric (DSC) and evaluated by Star-e Mettler Toledo analytical software as a function of curing temperature and the ratio of isocyanate to a hydroxyl (NCO: OH). The results from dynamic calorimetric measurements clearly indicated that the increase of NCO: OH ratio effectively reduced the exothermic peak and temperature of the curing reaction. Isothermal calorimetric measurements suggested that the curing reaction time reduced as the isotherm temperature increased. This effectually increased the curing reaction rate and contributed to the reduction in the gelation time as well as working life of PU.