Application of Plasma in Textile Processing : --------------------------------------------------------- 1 Desizing ------------------- Atmospheric pressure plasma treatment on cotton grey fabric (sized by standard sizing recipe containing starch) with air and He gas mixture alters the surface morphology, gave rise to desizing effect and enhance the wettability and wicking action. The hitting of ions gave rise to loosening of the surfaces that were removed in subsequent process of washing. The surface roughness as well as formation of (-C=O, -OH or C-N) bonds created functional groups are responsible for improved hydrophilic properties. The loss of weight in desizing process was more for plasma treated fabric that too in initial part of treatment. These higher rates of desizing plasma pre treated fabric can save time, energy and water. Atmospheric plasma treatments are applied to Desizing the cotton (PVA were used for sizing) using air/He and air/He/O2 combinations. These treatments removed some PVA film and significantly improved PDR (percent desizing ratio) by washing, especially by cold water washing. The tensile strengths of cotton fabrics treated with atmospheric pressure plasma were the same as for the unsized fabric. Results of the plasma treated PVA films revealed surface chemical changes such as chain scission and formation of polar groups, which promoted the solubility of PVA in cold water. Air/He/O2 plasma is more effective than air/He plasma on PVA desizing (because of oxidation is more for Air/He/O2 plasma) 2 .Scouring ----------------- Low temperature plasma treatment modified the surface of cotton fabrics. The contact angles between the liquid (scouring bath) and the low temperature plasma treated cotton fabric surfaces decreased significantly. Furthermore, the O2 plasma treatment by changing the surface properties dramatically increased the wicking rate of cotton fabrics, making them more absorbent. The results for scourability revealed that low temperature plasma treatment increased the scouring rate of cotton fabrics. O2 plasma caused changes in the oil, fat, and wax contents by etching where the topmost of the layer of the substrate is stripped off. This increased rate means that a shorter time have been chosen for scouring, the process was more environmentally friendly, and energy consumption decreased because less time was needed to reach the desirable state. For the scouring process, 25 minutes have been used for plasma treated instead of 40 minutes needed for scouring cotton fabrics . 3. Dyeing ------------------ The O2 plasma treatment dramatically increases the wicking rate of cotton fabrics, making them more absorbent hence increase the dyeing rate of cotton fabrics. Holes were visible on the O2 plasma treated cotton fabric surfaces, which were caused by the ablation effect of this nonpolymerizing reactive plasma gas. These holes provided a new pathway for the dye to enter the fiber and hence increased the dyeing rate. For the dyeing process 50 minutes have been chosen after plasma treatment instead of 90 minutes needed for dyeing untreated cotton fabrics. The Modification of the Cuticle and Primary Wall of Cotton by Corona Treatment was studied in which the effects of corona treatment were limited to the cuticle and primary wall of cotton, although one or two experiments (radiation sensitivity, bundle strength) suggested possibility for deeper penetration through to the secondary wall. Some disturbance of the wax on cotton was indicated in air chlorine corona treatments, and both the wax and cellulose reacted with chlorine in an air chlorine corona to produce C-Cl covalent bonds. Air-chlorine corona treatments have greater effect than the air corona treatments and air-chlorine corona treated fabrics are more wettable. A possible practical application of these results was to reduce the scouring or kier boiling required achieving a given dyeing level or dyeing uniformity .The effect of low pressure plasma treatment on bleached and mercerized cotton fabrics was investigated with water vapour as working gas. Though bleached and mercerized cotton fabrics were hydrophilic, the change in hydrophilicity after plasma treatment has been tested and higher concentration of oxygen was founded on the surface of water vapour plasma treated surface. These higher oxygen concentrated surfaces gained higher hydrophilic properties. An increase in hydrophilicity revealed deeper dye ability of plasma treated fabrics .
Posted on: Wed, 16 Apr 2014 08:22:32 +0000
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