| Wool textiles offer many excellent properties including good elasticity, high moisture absorption, good wearing comfort, and are popularly accepted by consumers. In addition, the excellent process-ability of wool fibres makes them one of the best natural fibre materials widely used in the textile industries. Along with growing demand for wool textiles and the progress in wool textile technology, accurate design and manufacture of wool textile products with light weight and improved comfort have become increasingly important. In recent years, high quality wool textiles made of superfine wool fibres have received much attention and are welcomed by high-end consumers. From the manufacturing point of view, however, the finer are the wool fibres,the greater is the manufacturing difficulty. The traditional processing technology of wool textiles encounters great difficulty in processing the superfine wool fibres, which hinders the batch production of such high quality products.The fundamental problem found in processing of superfine wool fibres is the fibre damage incurred during the processes of washing, carding and dyeing, and that caused in subsequent processes due to unsuitable handling of the fibres.. During the process of washing, carding and dyeing, the use of chemicals, the processing parameters such as temperature and pH value, and the action of mechanical force would all contribute to the deterioration of the interior chemical structure of fibres and hence physical and mechanical properties. Such damages to fibre properties resulting from chemical and physical structures within the fibre and morphology structure outside,will affect the processing properties of the fibres, and will also influence the quality and style of wool textiles such as elasticity, handle and luster. Therefore, in order to make the best use of the precious superfine wool fibres in developing high quality wool textiles, it is necessary to understand the damage mechanisms for superfine wool fibres in the manufacturing process, and to develop new processing technologies aiming for minimal damage in superfine wools. This research will be a significant step in superfine fibre processing and in satisfying the requirements of the market for high quality wool products.This research is carried out using 13.0μm superfine Australian wool. The aim of the research is to gain systematic understanding the damage mechanisms at different processing stages and to provide solutions to minimise the superfibre damage caused by fibre processing. The objectives of the research include the characterization of superfine wool in terms of structures and properties,establishment of a low damage washing device, optimisation of the carding process for superfine wool fibre, and low damage dyeing technology.In the chararcterisation of the 13.0μm superfine Australian wool, the structure and properties such as outside morphology, density, specific surface area, properties in felting, strength and extension, friction, dyeing, and Allw?rden reaction were measured and analysed. Compared to the ordinary 17.5μm wool, the superfine wool has a similar chemical structure to that of the ordinary wool, but superfine wool has more and smoother surface scales, which are thinner and more tightly lined up with smaller height. The fineness of superfine wool is obviously smaller with more scales and crispation per unit length of fibre. The average density and specific surface area of superfine wool are higher than the ordinary one. The cell membranes on the scale surface of the superfine wool are complete and Allw?rden reaction showed big and continuous bubbles on the surface. Superfine wool has lower strength, greater extension, larger specific broken work, and smaller initial modulus. Superfine wool has greater directional friction effect, in which the static friction effect is larger than the kinetic frictional effect, leading to the smaller felt ball than ordinary wool. These specific characteristics indicate that superfine wool fiber is easier to be felted. The comparison also indicates that the initial dyeing rate of superfine wool is faster and equilibrium dye uptake is slightly higher than that for the ordinary wool, which is possibly caused by its larger specific surface area and the smaller fineness.Due to the superfineness, superfine wool fibre is found easily felted at the washing stage, and this makes it difficult for down-stream carding process. A novel hanging basket for washing superfine wool fibres was designed and manufactured to monimise the fibre damage due to washing. This invention was granted a Chinese patent titled “Fibre Washing Method and Washing Device”. Based on the use of this device and the neutral washing method, the influences of detergent concentration, temperature, time and pH value, and so on on the washing quality of superfine wool were investigated by means of single parameter analysis and orthogonal experiment. A set of low damage washing parameters were identified based on this novel basket washing device, in which detergent concentration(2~4 trough) was chosen to be 2.2g/L,1.8g/L,1.4g/L; the temperature(1~6 trough) levels were 26℃,58℃,56℃,52℃,48℃,42℃; and the time durations(1~6 trough) were 80 s, 85 s, 85 s, 80 s, 80 s, 80 s. The results clearly show that the superfine wools washed with the novel hanging basket are with clean and smooth surfaces. The scales had lower damage and bubbles were continuously formed on the fibre surface in theAllw?rden reaction except for partially smaller unbroken bubbles. Compared to traditional washing processing, the average strength and the whiteness of superfine wool have been increased4.8% and 6.2%. Experiments also showed that production efficiency and production rate in the following spinning process have also been improved. The hanging basket solution is proven to be effective in achieving low damage washing processing for the superfine wool.The entanglement and fibre breakage problem associated with the superfine wool during carding was also investigated, using average fibre length and fuds ratio as the criteria. Processing parameters such as working-roll space, speed ratio, norms of carding fabrics and their distribution were studied for the influence on fibre damage. Orthogonal experiment was applied to optimize the carding processing. TEAM-3 predictor formula was employed in the establishment of quality monitoring diagram. The optimised parameters for low damage processing of superfine wool are found to be: 2# roll space, 3# speed ratio, the tooth density of cylinder wire cloth and doffer wire cloth to be 60.7teeth/cm2 and 62.5teeth/cm2 respectively, and the top production rate at 20g/m。The experimental results showed that the top yield of superfibre wool in low damage carding processing was increased, the number of neps were decreased, yarn evenness, the production efficiency and product quality were improved.Research was also carried out at the uneven dyeing, color difference between inside and outside wool top bulk, and the decrease of fibre strength, associated with the dyeing of superfine wool using Lanasol active dyes. Through the analysis on the causes of damage during dyeing process of superfine wool using the orthogonal experiment planning, the influences of dosage of auxiliary, dyeing temperature, dyeing time and pH value on the fibre strength, dye uptake, color yield(K/S value) and color fastness were studied, which has lead to the establishment of the understanding of mechanisms for superfine wool damage during dyeing. The optimised low damage processing condition for the dyeing of superfine wool was identified to be: temperature90℃,time 70 min,and pH value 4.0. Under this dyeing condition, the dyeing exhaustion reached98% with level dyeing, the rubbing and washing colour fastness were above grade 4. Compared to the traditional dyeing through the measurement of fibre strength, observation of SEM and Allw?rden reaction, the optimised dyeing processing worked to maintain the fibre strength of superfine wool during dyeing most notably, and the damage to the fibre scales was decreased.Such results marks the success in achieving the low damage dyeing of superfine wool fibres.In conclusion, the use of chemicals in washing and dyeing processes and the hostile conditions such as high dyeing temperature have found to cause fibre strength reduction and felting for superfine wool fibres, which lead to further physical damage of the wool fibres in the subsequent processing stages. Carding can cause physical damage directly by the mechanical action. All these cause the problems in superfine wool fibre processing, leading to low producingrate, low efficiency and low pass rate of the final products. The quality and style of final wool textiles could suffer consequently. In this systematic study, the factors influencing the various properties of superfine wool in washing, carding and dyeing were investigated, which led to improved understanding on fibre damage mechanisms associated with the chemical, physical, and mechanical processing conditions encountered in washing carding and dyeing. A novel and effective hanging basket for low damage washing of superfine wool fibres was designed and manufactured. A set of processing technology in washing, carding and dyeing for effective reduction of damage to the superfine wool fibres has been established. The findings of this research will not only scientifically support the development and production of high quality superfine wool textiles, and it will also contribute to the promotion of wool products for the high-end textile market. |
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