Preparation and properties of waterborne polyurethanes based on triblock glycol (CL)4.5-PTMG-(CL)4.5 for water vapor permeable coatings: Effect of soft segment content

A series of waterborne polyurethanes (WBPU) were prepared from 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI), 2,2-bis(hydroxylmethyl) propionic acid (DMPA), ethylenediamine (EDA), triethylamine (TEA), and triblock glycol TBG, (ε-caprolactone)_4.5-poly(tetramethylene ether) glycol (MW=2000)-(ε-caprolactone)_4.5: (CL)_4.5-PTMG-(CL)_4.5, MW=3000] as a soft segment. Two melting peaks of TBG at about 14°C and 38°C were observed indicating the presence of two different crystalline domains composed of CL and PTMG dominant component. The effect of soft segment content (60–75 wt%) on the colloidal properties of dispersion, and thermal and mechanical properties of WBPU films, the water vapor permeability (WVP) and water resistance (WR) of WBPU-coated Nylon fabrics, and the adhesive strength of WBPU-coated layer and Nylon fabrics was investigated. As soft segment contents increased, the water vapor permeability of WBPU-coated Nylon fabrics increased from 3615 to 4502 g/m²day, however, the water resistances decreased from 1300 to 500 mmH₂O.