Synthesis of Self-Colored Nano-Sized Water-Dispersion Polyurethane Coatings with Tunable Particle Size and Color: Anionomer vs. Cationomer

Hypothesis: Due to the outstanding properties of polyurethanes (PUs) and their widespread uses in various industries such as coatings, adhesives, and on the other hand, increasing the environmental concern to reduce VOC during production or application of  products, waterborne PUs have attracted much attention. In this study, a group of self-colored-PUs based-on isophorone and hexamethylene diisocyanate, PEG-400 and an azo-diol were synthetized. Dimethylol propionic-acid (DMPA) and N-methyl-diethanolamine (NMDA) were used as internal ionic groups, and then converted to the corresponding anionomer or cationomer using triethylamine or iodomethane, and finally dispersed in water by addition of water (PUDs). The effect of the anionizing group type and location (inner block (C) or outer block (T)), degree of neutralization and solid content of PUDs was studied on their dispersion viscosity and stability, color and particle size. The thermal properties, morphology, scratch resistance, and color migration of polymer films were studied. These studies were performed by rotational viscometry, DLS, FTIR and NMR spectroscopy, XRD, DMTA, TGA and DSC techniques.   The results indicate that anionomers are orange to reddish-fire-brick, and show increased viscosity and reduced particle size by increasing solid content. They showed decreased viscosity and increased particle size by reducing the degree of neutralization. Polymers with DMPA-T block, in higher solids content, have higher dispersion stability and smaller particle size than polymers with DMPA-C block. The cationomers are reddish-brown to dark-magenta. Cationomers with NMDA-C block exhibited smaller particle size and thermal stability than polymers with NMDA-T block. Generally, anionomers exhibited greater dispersion stability, lower particle size, and higher water absorption, scratch resistance and thermal stability than cationomers. T5% of PUD-DMPA-T and PUD-DMPA-C were 27°C and 250°C; respectively.