Improving Surface Energy and Hydrophilization of Poly(Ethylene Terephthalate) by Enzymatic Treatments

In order to increase the hydrophilicity and adhesion of poly (ethylene terephthalate) (PET) fabrics it was studied the action of three types of enzymes (Texazym PES sp5, Aspergillus niger and Aspergillus oryzae) applied at different incubation times and concentrations. This processes aims to modify morphologically and chemically the superficial structure of the polymeric materials (PET), forming new carboxyl, hydroxyl and other polar groups at the surface, in order to increase adhesion and hydrophilicity. The increase in the hydrophilicity of the fabric was evaluated by measuring the contact angle being the best results obtained for the Texazym PES (87.45o), much smaller than the non-treated fabric (122.95o); and by the wicking height, which revealed an important improvement in the hydrophilicity. The formation of carboxyl and hydroxyl groups was evaluated by a staining procedure with a cationic and reactive dye, respectively. It was also confirmed by the increasing in the polar component of the surface energy, determined by the Qwens-Wendt method. The higher surface energy and thus, the higher adhesion properties, were obtained for the esterase Texazym, using 0.12U during 90 minutes. The surface morphology of the non-enzymatic-treated and enzymatic-treated samples was analyzed by scanning electron microscopy (SEM) showing no degradation of fibers treated under the selected optimum conditions. In contrary, this method showed an important surface cleaning action by removing some undesirable polyester oligomers.