Synthesis of Waterborne Curing Agent and its Applications in Waterborne Polyurethane Adhesives

A novel waterborne curing agent (SWCA) is obtained by the reaction of isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG) and pentaerythritol (PE). Different quantities of SWCA were added to a waterborne polyurethane (WPU) to form a SWCA-modified WPU emulsion (SWPU). The structure of SWCA is characterised by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The effect of SWCA content on the initial tack, peel strength, solvent resistance and curing time are illustrated by T-peel strength, solvent resistance and curing time tests. The rheological properties of SWPU were assessed. The absorption peak at 2263 cm1 in the ATR-FTIR spectra shows that -NCO groups exist in SWCA. While the content of the curing agent increased from 0% to 4%, the initial strength increased from 1.82 N/mm to 3.87 N/mm; the final peel strength increased from 5.02 N/mm to 7.08 N/mm; and the water and ethanol absorption rate decreased from 11.3% to 6.14% and 15.38% to 11.52%, respectively. The curing time of the SWPU adhesives decreased with increasing curing temperature. The rheological test shows the SWPU emulsion exhibits elastic behaviour.