Hydrophobically modified ethoxylated urethane polymers: terminal sticker group influences on thickening and dispersing

Abstract

Abstract In order to clearly demonstrate the influences of terminal sticker group on thickening & dispersing, series of ethoxylated urethane polymers were prepared with tristyrylphenol ethoxylate (TP) and polyethylene glycol methyl ether (MP) as terminal groups, respectively. Viscosity behaviors of both series were studied for polymer aqueous solutions and thickened latex. MP series did not show obvious thickening effects. For TP series, viscosity of polymer aqueous solutions and thickened latex increased with the hydrophobic group percentage in polymers, instead of Mw. It is assumed that higher hydrophobic group percentage means more sticker sites in system for aggregation or adsorption, which contribute to the thickening. PEG segments are the frame of the thickening network but need hydrophobic stickers to fix them as well as avoid entanglement. This is proved by the results of rheology testings. Adsorption of polymers on latex particles was observed with DLS and TEM. Obvious hydraulic layer around latex particles could be seen for TP series. Synthesized polymers were also utilized to disperse carbon black pigment, to see if we could combine thickener and dispersant together for paints applications. MP series showed good dispersing performance. For TP series, with the decreasing of hydrophobic sticker groups percentage, the polymers showed better dispersing performance. For particle size and viscosity, TP series are still worse than MP series; but for color strength, TP series were comparable or even better. This is because HEUR polymer chain could adsorb onto one pigment particle while flexible PEG chain curls to supply steric stability effect for pigment particle. With above observation, it will be possible to develop one type of dispersing & thickening 2-in-1 additives for paints.