Preparation and properties of fluoride-free water repellents of waterborne polyurethane stearic acid modified hyperbranched polyester

The waterborne polyurethane (WPU) was synthesized using hydroxy-terminated polydimethylsiloxane(number-average molecular weight is 2 000), trimethylolpropane (TMP), N-methyldiethanolamine (N-MDEA) and toluene diisocynate (TDI) etc. as raw materials. To introduce the hydrophobic branched chain, hydroxy-terminated hyperbranched polyesters were modified by stearic acid, hyperbranched polyesters end-capping with stearic acid were obtained. The composites consisting of WPU and stearic acid modified hyperbranched polyesters (SA-HBPE-3) were compounded and appled to fabric. The structures of WPU and SA-HBPE-3 before and after modification were characterized by infrared spectroscopy. The effect laws of SA-HBPE-3 content on water resistance, surface energy and water repellents of SA-HBPE-3/WPU film were studied by static water contact angle, water absorption rate and application test. The results show that when the SA-HBPE-3 content increases from 0 to 30wt%, the water absorption rate of SA-HBPE-3/WPU film reduces to 6.63%, and the static water contact angle of coating fabric rises to 135.3°. The water resistance of SA-HBPE-3/WPU films and the water repellency of coating fabric increase with the addition of SA-HBPE-3. When the SA-HBPE-3 content is 20wt%, the waterproof performance evaluation gets the highest 90 points.