Effects of trimethylol propane and AAS salt on properties of waterborne polyurethane with low gloss

A series of waterborne polyurethane(WPU) dispersions containing different amounts of trimethylol propane(TMP) and/or 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt (AAS salt), were synthesized by prepolymer emulsification process. The effects of TMP and AAS salt on properties of WPU dispersions were discussed to find out the appropriate formulation of WPU dispersion with low gloss. The results showed the particle size of WPU increased as the TMP content increased, but a decrease to the gloss and transparency. Spherical granules emerged in the surface morphology of WPU films when the TMP content exceeded beyond 1% by weight via scanning electron microscope (SEM). In contrast, as the AAS salt content increased, the particle size of WPU decreased, and the gloss and transparency increased. It was most worth noting that the dispersion stability of WPU dispersions was enhanced dramatically with the increase of AAS salt content by measuring the Zeta potential of emulsion. Therefore, WPU dispersions with low gloss and high dispersion stability can be prepared successfully with the AAS content of 0.5% by weight and the TMP content of 1%-1.5% by weight when other influence factors were fixed to a suitable condition.