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.