Plasma technology in wool

Abstract

The textile industry processes a large quantity of fibres obtained from various animals of which wool is commercially the most important. However, it has some technical problems which affect the quality and performance of the finished products such as felting shrinkage, handle, lustre, pilling and dyeability. These problems may be attributed mainly to the presence of wool scales on the fibre surface. The scales are relatively hard and have sharp edges which are responsible for causing fibre directional movement and shrinkage during felting. Furthermore, the scales also serve as a barrier for diffusion processes which will adversely affect the sorption behaviour. In recent years, there has been an increase in the modification of wool surface scales by physical means such as mechanical, thermal and ultrasonic treatments, and chemical methods such as oxidation, reduction, enzyme and ozone treatments which can solve the felting and sorption problems to a certain extent. Hitherto, chemical treatments are still the most commonly used descaling methods in the industry. Owing to the effect of pollution caused by various chemical treatments, physical treatments such as plasma treatment have been introduced recently as they are capable of achieving a similar descaling effect. Since the 1960s, scientists have successfully exploited plasma techniques in materials science. The plasma technologies have been fully utilised to improve the surface properties of fibres in many applications. The fibres that can be modified by plasmas include almost all kinds of fibre such as textile fibres, metallic fibres, glass fibres, carbon fibres, fabrics and other organic fibres. Plasma-treated wool has different physical and chemical properties when compared with the untreated one. The changes in fibre properties alter the performance of the existing textile processes such as spinning, dyeing and finishing to produce a series of versatile wool products with superior quality. Therefore, the aim of this monograph is to give a critical appreciation of the latest developments of plasma treatment of wool. In this monograph, different surface treatments of wool including plasma treatment will be precisely described. Since plasma treatment can be used to alter material surfaces by removing outer layers, thus the method of generation of plasma and the reaction mechanisms between material surface and plasma species will be highlighted in this monograph. Similar to other chemical reactions, the factors such as (i) the nature of gas used, (ii) gas flow rate, (iii) system pressure and (iv) discharge power affecting the final results of plasma treatments will be described. The main content of this monograph includes the application of plasma treatment on wool under different industrial conditions such as dyeing and shrinkproofing processing which will be reported and discussed respectively. In addition, the common analytical methods such as Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy and Fourier Transform Infrared Spectroscopy with Attenuated Total Internal Reflectance mode analysis employed for characterising the surface properties of plasma-treated wool will be discussed. Based on the surface characterisation results, more details about the mechanism of plasma treatment that affects the wool processing such as dyeing and shrinkproofing can be explored. In the latter part of the monograph, the serviceability of plasma-treated wool fabrics is discussed and the possibility of applying the plasma-treated wool fabric to industrial use is evaluated based on standard performance specification, e.g. ASTM. The fabric performance in terms of tailorability and sewability are also discussed with reference to the Kawabata Evaluation System for Fabric (KES-F) results. As the plasma process is a “dry” process, i.e. the water used in the plasma system can be recycled, thus it can solve the industrial effluent problem resulting in providing an effective means for the modification of wool fabrics.