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Cotton fabric was esterified with C4-18 aliphatic monobasic acid chlorides in dimethyl formamide, with pyridine as acid scavenger, at temperatures of 30-85°C. Reaction for 15-60 min at 85°C produced 0.02-0.36 ester groups per monomer unit, which provided water-repellency ratings of 50-80 in the AATCC spray test; water-repellency generally improved with increasing chain length and reaction temperature. Dry-cleaning resistance was good in perchloroethylene alone, but addition of alkaline soap required longer chain lengths and preferably an aqueous post-rinse to retain water repellency. Air permeability decreased during the reaction, but this was due primarily to shrinkage rather than inherent in the pro duction of water repellency. Tensile strength decreased gradually with increasing chain length, temperature, and time, but it was possible to produce a maximum spray rating of 80 with a tensile loss of only 33% and spray ratings of 70 with tensile losses as low as 12%. [ABSTRACT FROM PUBLISHER]