Synthesis and Properties of Branched Waterborne Polyurethane Thickener With Multiple Arms

ABSTRACT Hydrophobically modified ethoxylated urethane (HEUR), a typical polymer associative thickener, is extensively applied in aqueous coatings, textile printing, and resin coatings to regulate the rheological properties of the system. However, conventional branched HEURs face two critical limitations: (1) the risk of excessive cross‐linking during the chain‐expansion stage due to high monomer reactivity; (2) the phase‐separation phenomenon in some branched HEUR aqueous solutions upon standing. To overcome these challenges, we designed and synthesized a polyhydroxy hyperbranched structure (PU‐OH 3‐6 ). This structure features two main advantages: a larger central backbone and a greater spacing between active groups (OH). The hyperbranched HEUR 3‐6 synthesized using PU‐OH 3‐6 as a branched‐type chain extender is more controllable and viable in the production process. Moreover, various testing methods were employed to assess the thickening performance, salt resistance, and water retention of HEUR in a pure‐water system. The results indicated that the branched structures of HEUR 3‐6 have better thickening properties compared with the previously reported HEUR with a linear structure (HEUR L ), and branched HEUR with using gamma‐triol (HEUR GI ), pentaerythritol (HEUR P ), and xylitol (HEUR X ) to expand the chain. Among them, HEUR 5 demonstrated the best thickening effect in pure‐water systems, while in salt‐containing solutions, HEUR 6 with a six‐branched degree showed more pronounced anti‐electrolyte properties.