Effect of pretreatment conditions on the hydrolysis and water absorption behavior of poly(ethylene terephthalate) fibrous assembly

Poly(ethylene terephthalate) (PET) fibers are very hydrophobic and are therefore treated by alkaline hydrolysis to reduce their hydrophobicity, which not only reduces their weight but also enhances their softness, flexibility and drapability. In addition, if alcohol is used as a pretreatment agent, the form of the fibers can be changed and more benefits can be obtained from the subsequent alkaline hydrolysis treatment. Therefore various alcohols were used as pretreatment agents and their effect was investigated. Treatment with 1-decanol leads to more weight loss of the PET fibers than treatment with the other alcohols investigated. Treatment with sodium hydroxide leads to weight loss in PET fabrics because terephthalic acid and ethylene glycol are separated by the hydrolysis of the ester group in the PET chains. Weight loss increases with increasing hydrolysis time and the reaction does not immediately reach equilibrium. The microvoids of the PET surface hold water molecules. The surface morphology of PET shows that the pretreatment reagent attacks almost the entire surface of a fiber, causing surface etching. As the surface etching progresses, it propagates inside the fiber, resulting in the formation of elongated cavities on the surface. A polyester fabric treated with various alcohols showed higher water absorption. Hydroxyl groups were crowded at the parts with craters made by the alcohol pretreatment, and this increased the water absorption.