Enzymatic treatments surface dyeing

Dye assays can be employed in a more direct approach to quantify hydroxyl and carboxyl groups on the PET polymer surface introduced by enzymatic treatments [34]. Improved dye uptake of enzyme-treated fabrics shown by an increase in the color shade of samples dyed with cationic or reactive dyes determined by reflectance measurements indicated a partial enzymatic hydrolysis of PET surfaces [2, 11, 27, 84, 107]. Likewise, the formation of free carboxyl groups formed by enzymatic treatment of PET films can be analyzed following esterification using a fluorescent alkyl bromide [23]. 

Alternatively, surface hydrolysis of PET can be achieved by treatment with enzymes that introduce polar groups to the polymer surface. A number of hydrolytic enzymes, such as lipases, cutinases, and esterases, have shown potential for surface functionalization of PET [36, 99]. The biocatalytic method can be performed under mild reaction conditions avoiding the use of large amounts of chemicals and energy for the finishing and dyeing processes. The enzymatic modifications are specific and can be limited to the polymer surface. Consequently, the bulk properties and mechanical stability of the polymer are not compromised, and material savings and products of better quality or with new functionalities can be obtained. 

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