Comparison of the properties of waterborne polyurethane-ureas containing different triblock glycols for water vapor permeable coatings

Four types of triblock glycols [(CL)_4.5-PEG-(CL)_4.5, (CL)_4.5-PTAd-(CL)_4.5, (CL)_4.5-PTMG-(CL)_4.5, and (CL)_4.5-PPG-(CL)_4.5, Mn=3,000] were synthesized by end-capping reactions of ɛ-caprolactone (CL) and poly(ethylene) glycol (PEG, Mn=2,000), poly(tetramethylene adipate) glycol (PTAd, Mn=2,000), poly(tetramethylene) glycol (PTMG, Mn=2,000), or polypropylene glycol (PPG, Mn=2,000)]. Waterborne polyurethanes (WBPUs) were prepared by polyaddition reaction using 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI), 2,2-bis (hydromethyl) propionic acid (DMPA), ethylene diamine (EDA), triethyl amine (TEA), and the triblock glycol. Studies have been conducted on the effects of triblock glycol type on the colloidal properties of dispersion, the hardness and mechanical properties of WBPU films, the water vapor permeability (WVP), and water resistance (WR) of WBPU-coated nylon fabrics. The WVP (%WVP based on control nylon fabric) of WBPU-coated nylon fabrics based on (CL)_4.5-PEG-(CL)_4.5, (CL)_4.5-PTAd-(CL)_4.5, (CL)_4.5-PTMG-(CL)_4.5 and (CL)_4.5-PPG-(CL)_4.5 were 3,975(81), 3,115(62), 3,124(64), and 2,569(52) g/m² day (%), respectively. However, the WBPU based on (CL)_4.5-PEG-(CL)_4.5 was not applicable for coating material, because its dispersion and film had relatively high viscosity (3,000 cps at 50°C) and low mechanical properties, respectively. In this work, the triblock glycols (CL)_4.5-PTMG-(CL)_4.5 and (CL)_4.5-PTAd-(CL)_4.5 were found to be desirable glycols for water vapor permeable coating materials.