Surface characterizations of polyurethanes having different types of soft segment

Waterborne polyurethanes have been designed and synthesized based on different types of soft segment, viz. poly(tetramethylene adipate) glycol (PTAd; Mn¯=4000), poly(2,4-diethyl-1,5-pentamethylene adipate) glycol (PDPAd; Mn¯=1000), and their copolyester polyol. Surface and adhesive properties of the dispersion cast films were analyzed by angle resolved X-ray photoelectron spectroscopy (ARXPS), contact angle and adhesion measurements. It was found that PDPAd segments were preferentially segregated at the free surface and gave much high instant adhesion to rubber surfaces, whereas PTAd segments gave high permanent strength, and the results were interpreted in terms of high tack and crystallization of each soft segment.