Preparation of waterborne polyurethanes using an amphiphilic diol for breathable waterproof textile coatings

The application of polyurethanes (PUs) on breathable waterproof fabric coatings requires a balance of water vapor permeability (WVP) and water resistance which can be achieved by tailoring hydrophilic and hydrophobic segments. PU prepolymers were prepared from isophorone diisocyanate, dimethylol butanoic acid, and a mixture of various ratios of amphiphilic PPG2050 (copolymer of ethylene oxide and propylene oxide with -OH end groups) and hydrophobic poly(tetramethylene ether glycol) (PTMEG). After neutralization with triethylamine, the prepolymers were chain-extended with ethylene diamine/1,4-butanediol (1:1 by molar). The WVP values of the fabric coatings prepared using various waterborne PUs were very similar (910-990 g/m² × 24 h). When waterborne PUs prepared using a mixture of PPG2050 and PTMEG were employed for the textile coatings, the resulting PU-coated textiles exhibited excellent waterproof properties (>10,000 mm H₂O). The textile coatings prepared from PPG2050/PTMEG-based waterborne PUs were significantly more waterproof than those prepared from poly(ethylene glycol) (PEG)/poly(propylene glycol) (PPG)/PTMEG-based waterborne PU. This is probably due to a more even distribution of hydrophobic segments in the PUs, even though the WVP values of the PEG/PPG/PTMEG-based PU coatings were considerably smaller than those of the PPG2050/PTMEG-based PU coatings.