Durable Press Finishing of Cotton Fabrics with Citric Acid: Enhancement of Whiteness and Wrinkle Recovery by Polyol Extenders

Abstract

A durable press finisher formula based on citric acid (CA), featuring polyol extenders, can be made to compare favorably to dimethylol dihydroxyethyleneurea (DMDHEU) or 1,2,3,4-butanetetracarboxylic acid (BTCA) in whiteness and wrinkle recovery performance. Durable press (DP) finishing of cotton fabrics with CA has long been implicated by inferior resilience enhancement and appreciable fabric yellowing, which hinder the industrialization of the technique despite the obvious merits of CA being cost-effective, nontoxic, and renewable. In this research, glycerol was used as the model compound for investigateing the mechanism of polyol’s whitening effect and for obtaining the optimized curing conditions. Then a series of polyols were investigated as extenders for the cross-linking of cotton with CA. Performance indicators such as the wrinkle recovery angle (WRA), CIE whiteness index (WI), tear strength (TS) retention, and DP rating of the treated fabrics were correlated with curing conditions and the structures of the extenders. It was found that the whitening power of the extenders is directly related to the number of primary hydroxyl groups. It was also found that polyols containing both primary and secondary hydroxyl groups are more effective at enhancing the resilience of treated fabrics. By using xylitol as the extender, DP ratings of 3.8–3.9 were imparted to both white and dyed cotton fabrics finished with CA without significant yellowing or discoloration. The addition of the extender was also favorable to the durability of the DP effects so that a DP rating of 3.5 was retained after 20 washing and tumble-drying cycles. It was shown that by using biobased extender xylitol two major drawbacks of DP finishing of cotton with CA could be eliminated, presenting an essentially green alternative to DMDHEU.