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Polyurethane dispersions (PUDs) have been an active area of research since the early 1940s because of legislative restrictions on the use of organic solvents in conventional solvent-based products and also because PUDs exhibit almost the same high performance levels as solvent-borne polyurethanes. In the present study, properties of conventional waterborne PUDs are modified with epoxy-acrylic graft copolymer blocks. The epoxy-acrylic graft copolymers were first modified with ethylene diamine to give amine-terminated blocks which in turn reacted with isocyanate-terminated prepolymer (prepolymer mixing process) to give modified PUDs. Several experimental sets were prepared with varying compositions. The experimental sets were also prepared using conventional poly(ethylene glycol) blocks and ethylene diamine chain-extenders. The physico-chemical properties and film characteristics of the experimental sets show the dramatic improvement in important mechanical properties of PUDs due to grafting with epoxy-acrylic copolymer blocks.

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Copolymers containing 50% dehydrated castor oil fatty acids (DCOFA) derived from renewable resources, were synthesized via free radical solvents less polymerization with maleic anhydride, styrene, and butyl acrylate. The copolymer was crosslinked further with polyethylene glycol 400 (PEG 400) to increase its molecular weight. The copolymers with and without crosslinking were then neutralized with sodium hydroxide to prepare polymeric dispersants DFCD1 and DFCD2 respectively in aqueous medium. It was observed via surface-tension measurement that both DFCD1 and DFCD2 transfer to the air-water interface before forming any aggregates, and the ease of forming the aggregates is in the order of DFCD1 > DFCD2. The efficacy of these dispersants was examined in the dispersion of the titanium dioxide pigment and conventional extenders like calcite, talc, and china clay using flow point and zeta potential measurements. The results reveal that DFCD2 improved the dispersing ability for the pigment and extenders studied. The performance of these polymeric dispersants was also studied and compared in waterborne flat paint as a rheology modifier and pigment-dispersing agent. The paint rheology profile and dE data indicate the superior performance of the paint containing dispersant DFCD2. When used in combination with conventional styrene-acrylic latex, DFCD1 and DFCD2 reduced the minimum film-forming temperature (MFFT) of the polymer latex.