Preparation and performance study of GLC/TMP double crosslinking modified waterborne polyurethane for wood coatings

A glucose-modified double crosslinked waterborne polyurethane (WPCU) was synthesized by glucose (GLC) and trimethylolpropane (TMP) as crosslinking agents, polycarbonate diol (PCDL) as the functional soft segment material, and isophorone diisocyanate (IPDI) as the hard segment. The effects of GLC and TMP on the structure and material characteristics of WPCU were examined and evaluated using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and other tests. The experimental results demonstrate the favorable comprehensive performance of the modified WPCU. The double-crosslinked polyurethanes exhibited excellent mechanical strength (30.9 MPa for WPCU-0.9 film), a higher water contact angle (82.9° for WPCU-0.3 film), and superior thermal stability compared to single-crosslinked polyurethanes modified solely with GLC. In addition, a new type of double crosslinked waterborne wood paint was formulated by adding various additives. It was subjected to painting experiments on wood panels. The newly developed wood coatings using double crosslinked WPCU emulsions exhibit good chemical resistance (to alcohols, acids, and bases), dry heat resistance, and adhesion (adhesion class I). Paint films achieve a hardness of 2H when the GLC content exceeds or equals 1.2%, exhibiting excellent adhesion resistance, which could contribute to the development of high-stiffness waterborne polyurethanes in the future.