Preparation and Characterization of Low-gloss Waterborne Polyurethane Coatings

Abstract

In this research, a series of anionic low-gloss waterborne polyurethanes were prepared, and their surface structures were studied. S amples were prepared with terminal hydroxyl polydimethylsiloxane (PDMS ), polyethy- lene glycol (PEG) of different molecular weight, toluene diisocyanate (TDI), dimethylolpropionic acid (DMPA), in the presence of dibutyltin dilaurate (DBTDL) catalyst, neutral- lized by triethylamine (TEA). Preparation process was optimized to get better emulsion stability and matting effect of coating. The preparation process is: at 90 ℃ , react terminal hydroxyl polydimethylsiloxane, polyethylene glycol, toluene diisocyanate and dibutyltin dilaurate catalyst together for 4h. Cool the performed polymer to 50 ℃, then add quantified dimethylolpropionic acid and solvent such as tetrahydrofuran, heat to 70 ℃ and react for 2h. Cool polymer to room temperature, add quantified triethyl-amine and deionized water to make emulsions. Matting aqueous polyurethane under the conditions of R = 1.2, DMPA mass fraction of 6%, PEG molecular weight of 1000, PEG / PDMS molar ratio = 1: 3, catalyst mass fraction of 0.5%, neutralization degree 100%, latex solid content of 20%, gets the best overall performance, 60 ° gloss of 3.3, in line with matting standards.