Preparation and properties study of waterborne polyurethane synthesized by mixing polyester diols and isocyanates

In view of environmental protection requirements, it is an inevitable trend for waterborne coatings to replace traditional coatings. Waterborne polyurethane (WPU), a kind of typical resin used in coatings, has become a research hot topic of waterborne coatings because of its advantages, such as non-polluting, safe and reliable, excellent properties, good compatibility, and easy modification. In this article, solvent-free WPU is prepared by mixing 4,4′-dicyclohexylmethane diisocyanate/ isophorone diisocyanate (HMDI/IPDI) and polycarbonate diol/ Polycaprolactone diol (PCDL/PCL). Through the comparison of the properties of the polymer, the best amount of raw materials was determined. Specifically, R = 1.35 (R is NCO/OH ratio), the content of dimethylolpropionic acid (DMPA) is 5.5%, the content of trimethylol propane (TMP) is 2.5%, the mole ratio of HMDI/IPDI is 2:1, the mole ratio of PCDL/PCL is 2:1, and the preeminent WPU shows the excellent thermal stability, the contact angle of 118.04°, the hardness is H. The chemical structures and rough surface morphologies of the WPU films were characterized by FT-IR, TG, AFM, and SEM, respectively. Therefore, considering the film properties, and the low cost, simple, and green process, this research will offer the possibility of application of this free-solvent WPU in industrial production and large-scale application.