Covalent Modification of the Wool Fiber Surface: The Attachment and Durability of Model Surface Treatments

Abstract

Exposure of reactive chemical functional groups through controlled surface lipid removal provides a means for covalent attachment of novel molecular entities to the wool fiber surface. Cleavage of the dominant lipid in the epicuticle, 18-methyleicosanoic acid (18-MEA), from the underlying proteinaceous layer was employed, prior to further surface modification, by means of aqueous hydroxylamine treatment. Treatments utilizing covalent bonding to the surface through thiol, carboxyl, amine, or other reactive chemical groups offer improved durability to textile processing, such as dyeing and laundering. This surface modification investigation compared and assessed the attachment and durability of various wool fiber surface modification technologies and provided proof of principle for the manipulation of surface properties via covalent attachment of treatment compounds, providing enhanced fiber performance. Following removal of the surface lipid layer, wool fibers were modified using fluorescent and hydrophobic compounds and micro and nanoparticles. The extent of modification was assessed using scanning electron, light, and fluorescence microscopy, wettability testing and X-ray photoelectron spectroscopy (XPS). Surface treatments were evaluated with regard to effectiveness and durability to dyeing and laundering. Surface modification via attachment to thiol and other nucleophilic functionalities was observed to be greatly improved after hydroxylamine treatment, demonstrating the advantage of a customized exposed and accessible surface before secondary treatment. Increased durability and effective microparticle attachment was best accomplished employing zero or short-range crosslinking mechanisms, with zero-length attachment enhanced with the use of the crosslinking promoters, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Fluorescent and hydrophobic surface modifications exhibited high durability to laundering and demonstrated the viability of customizing surface hydrophobicity.