Study and scientific rationalization of the last finishing stages for high quality wool fabrics

The excellence in quality of Italian wool fabrics, which ensures a worldwide leader position of the Biella district, depends fundamentally on three factors: the design, distinctive of the “Made in Italy”, the choice of very fine fibers and the adoption of particular finishing techniques, which ensure optimal physical characteristics especially for the tailorability of light fabrics with a special “hand”. Among the fundamental steps of the wool textile production, finishing is certainly the one that, still nowadays, depends largely on empirical knowledge. A critical review, aimed at rationalizing the process considering both the costs and the quality guarantee, requires the realization of two preliminary conditions: understanding physicochemical parameters and laws which rule the process and the development of measuring methods which allow to objectively evaluate the influence of the controlling variables. In the majority of finishing processes, the fabric is exposed to the action of water or steam, in different conditions. The main goal of finishing is relaxation and/or stabilization of internal stresses at molecular level (the so-called “setting”) generated by the complex macromolecular structure of wool fibers. This can be made by means of three basic operations: steaming, decatizing at atmospheric pressure and decatizing under pressure (KD). Actually, the last operation is the most critical one, because it is realized wrapping the textile material on a perforated drum, through which steam is fed. The whole operation is led in an autoclave, at variable temperature and pressure, depending on the textile product. A KD operation affects disulfide bonds, bringing about their redistribution, with a permanent effect. This action, called setting, is given by a fine tuning of the process variables: temperature, moisture content, treatment time and mechanical pressure. All these four variables interact reciprocally but their relationships have not been fully understood; therefore a scientific criterion is fundamental for rationalizing sequence and intensity of the operations. To reach these goals, two different approaches were adopted in the present work. The first one was based on a set of experiments on suitable bench scale equipments, carried out to monitor the process parameters (particularly temperature and moisture content) during the treatments and within the textile structure. The second approach concerns the development of theoretical models, whose application in a computer algorithm, thanks to a finite elements based simulation software, allowed to simulate the system behavior.