ABSTRACT
Wool and human hair fibers and nails can be considered as natural composite materials, with keratinous proteins being their main constituent. Wool and human hair consist of cortical and cuticular cells. The cuticular cells are located at the outermost surface of the fiber enveloping the cortical cells forming a layer of flat scales overlapping one another. The cuticular cells are formed by endocuticle, A
and B exocuticles and an exterior thin membrane called epicuticle. The epicuticle has a thickness of 5-7 nm and it consists of an outermost fatty acid monolayer (Flayer) and a protein layer with hydrophilic groups [1]. The fatty acids are covalently bound to proteins by ester or thioester bonds [2] and they confer surface hydrophobicity to keratin fibers. It is reported that both hydrophobicity and scaly surface nature exert a considerable influence on the felting shrinkage of wool fabrics during an aqueous washing process [3],
Today, the most promising shrink-resistance treatments for wool are the lowtemperature plasma (LTP) or glow discharge (GD) treatments, which are considered environmentally acceptable processes. Plasma is a partially ionized gas generated by an electrical discharge. Plasma consists of neutral particles (molecules, excited atoms, free radicals and metastables particles) and charged particles (electrons and ions). These particles exclusively affect the wool surface, whereas the bulk properties remain intact [4]. But the vacuum ultraviolet (VUV) radiation (A< 200 nm) generated in the plasma reactor chamber can lead to bond (e.g., CC, C-H) breakage and to the formation of free radicals [5-7]. The VUV radiation can penetrate to a depth of tens of nanometers, depending on the absorption coefficient of the substrate material.
