| In the textile industry, many starches and modified starches, polyvinyl alcohol (PVA) and polyacrylate are widely used as sizing agent for fabric. But sized fabrics have to be desized to meet the subsequent processing (dyeing, printing and finishing). In conventional desizing processes, the sized fabrics are washed with hot water and NaOH to remove size agents. Because of the high pH values in this method, the treatment should be followed by intensive rinsing and neutralizing, which means that large amount of water and energy is also consumed. The status shows that about900millions tons of waste water is used every year in textile industry. Moreover, the aggressive scouring treatment conditions frequently damage the fiber. Obviously, this desizing process is unable to meet the requirement of environmental protection and quite adverse to the sustainable development of textile industry. Therefore, in order to deal with the problems, the processing route of desizing and finishing needs to be improved.Compared with the conventional chemical processes, plasma treatment does not require the use of water and chemicals, resulting in the drastic reduction in pollutants and a corresponding cost reduction for effluent treatment. Plasma treatment is an environmentally friendly technique without affecting the bulk properties of textiles. As a high-efficiency surface modification technology, more and more researchers pay close attention to the application of plasma treatment in the pre-treatment and finishing of textiles. If plasma technology can be applied in textile desizing process, both chemical agents and wastewater will be significantly reduced. Meanwhile, the consumption of energy and water can be greatly decreased. Therefore, it has great environmental and economical benefits.However, previously study mostly focused on the treatment of low-pressure plasma to textiles. The low-pressure plasma involves a vacuum system and thus may not be continuous processes. Compared with low-pressure plasma, the atmospheric pressure plasma treatments do not require a vacuum system and therefore can be applied on-line for substrates. And it is not doubtable that the electron temperature is much lower in the atmospheric pressure plasma in comparison to the typical low-pressure reactor, therefore they are particularly suited to apply to textile processing because most textile materials are heat sensitive polymers. In addition, it is a versatile technique, where a large variety of chemically active functional groups can be incorporated into the textile surface. The possible aims of this are improved wettability, adhesion of coatings, printability, induced hydro-and/or oleophobic properties, changing physical and/or electrical properties, cleaning or disinfection of fiber surfaces etc. But, there is difference in interaction of plasma and textiles between low and atmospheric pressure. At atmospheric pressure, especially for atmospheric pressure plasma jet, plasma is generated in noddle and ejects to form plasma jet, then reaches onto the surface of the materials. So, the plasma treatment parameters, such as the distance between noddle and material, treatemt time, component and flow velocity of gas, etc., influence the plasma treatment effect. Moreover, because the atmospheric pressure plasma treatment is in atmosphere, the substrate material may absorb significant amount of water. The existence of water molecules can lead to a more complicated interaction between active species in plasma and substrate surfaceThe previously study of plasma desizing mostly focused on the removal of the single size agent (such as PVA). and up to now, there are few report about plasma desizing blended size and combination of plasma and traditional desizing method. Therefore, the objective of this study is to investigate the influence of plasma-wet treatment on desizing of sized fabrics with blended size agent by atmospheric pressure plasma jet (APPJ), andi studied the influence of plasma treatment parameters and moisture content in fabric on plasma etching and surface morphological of size film. Morphological and chemical changes on the fabric surface are characterized by Scanning Electron Microscope (SEM), Atomic force Microscope (AFM) and X-ray Photoelectron Spectra (XPS), respectively. My measurement of weight loss and percent desizing rate lo discuss and analyse the inlluence of plasma treatment on plasma directly removal of size and on subsequence wet desizing effect. The wettability of desized fabric is characterized by wicking height.Firstly, the inlluence of different processing parameters (treatment lime, jet to substrate distance and gas flow rale) on the etching effect and surface morphology of blended size film of phosphate starch and PVA by He/O2atmospheric pressure plasma jet (APPJ). The results show that as the increase of treatment time and O2flow rate, the weight loss, surface roughness and surface area of size film increase. But, after treatment time is over45s, the increment of weight loss decreases. Moreover, the weight loss, surface roughness and surface area of size film increase firstly and then decrease as the jet to substrate distance increases. When the distance is over6mm, there almost are no treatment effect on the surface, but when the distance is2mm, the best treatment effect can be observed. The research results also show that plasma treatment can introduce more oxygen-contained active groups onto the size film surface, which improve the hydrophilcity of blended size.Secondly, to investigate the relationship between the absorbed moisture and plasma treatment effect, atmospheric pressure plasma jet (APPJ) is used to treat the blended size film of phosphate starch and PVA with moisture regain (MR) of3.2%、10.5%and79.2%corresponding to10%、65%and97%relative humidity (RH), respectively. Atomic Force Microscope (AFM) result shows that after plasma treatment, the surface roughness of all three group samples obviously increase. As the increase of absorbed moisture, the surface roughness increase firstly and then decrease. When increase the RH from10%to65%. the surface roughness increase from16.01nm to16.62nm. But further increase RH to97%. the roughness is only13.59nm. The weight loss result indicates that the weight loss increase as the increase of absorbed moisture. But compared with surface roughness, there is no direct relation between weight loss and roughness under certain conditions, that is higher etching rate may be not result in rougher surface after plasma treatment. The desizing results show that as the increase of plasma treatment, the percent desizing rale (PDR) increase for the all samples. And the PDR decrease as the increase of absorbed moisture of blended size. When plasma treatment is under10%RH, the PDR is the biggest, about96%. But when RH is97%. the PDR is only about90%.To investigate the influence of plasma treatment on conventional wet desizing. the sized fabrics are treated by He/O2atmospheric pressure plasma jet (APPJ). subsequently the treated fabrics are desized by NaHCO3. AFM analysis shows that the surfaces of sized fabrics become rougher after plasma treatment. The Ra values were2.2.8.9and26.8nm and the Rms values were2.8,11.4and33.1nm for untreated, the plasma treated for15and45s. respectively. XPS analysis indicates that the surface chemical composition of sized fabrics is greatly changed after plasma treatment. Compared to the untreated, the oxygen content increased significantly indicating oxygen containing polar groups introduced onto the surface after He/O2plasma exposure, which improves the hydrophilicity of blended size. The desizing results show that plasma pre-treatment significantly improves the NaHCO3desizing effect. As the increase of plasma treatment time, the percent desizing rate of NaHCO3increases. Only about77%PDR could be reached for the untreated fabrics, whereas more than95%PDR was achieved after45s plasma treatment followed by the same NaHCO3desizing process. Plasma pre-treatment can decrease the NaHCO3desizing temperature to some extent, and significantly shorten NaHCO3desizing time.To investigate the influence of plasma pre-treatment on ultrasound desizing, the sized fabrics with blended size is treated by APPJ, and subsequently the treated fabric is desized by ultrasound. As the increase of plasma treatment time, the surface of sized fabric becomes rougher, and more oxygen-containing polar groups are introducted onto the surface of fabric. The desizing results show that only ultrasound treatment almost can not remove the size from fabric surface. But, only plasma treatment can observe about95%PDR at80°C. However, the combination of plasma and ultrasound can observe higher PDR at lower desizing temperature. The PDR reached98.3%for the fabrics with50s plasma treatment followed by ultrasound desizing at60°C for20min. And as the increase of plasma treatment time, the PDR of ultrasound treatment increase. Moreover, compared with the samples with plasma treatment only, the relative increase of the capillary height of the fabrics desized by the plasma-ultrasound were9.7%.12.9%.15.1%and10.1%. respectively. The increase of capillary heights indicated that plasma treatment followed by the ultrasound desizing could effectively remove most of the blended size on cotton fabricsFinally, the relationship between APPJ and NaHCO3removing polyacrylate sixes from PET fabric is also studied. AFM analysis shows that the surfaces became progressively rougher after the plasma treatment. The Ra values are0.93,9.15and15.97nm for the untreated sample, the plasma treated for35and50s. respectively. And compared to the untreated sample, the O/C ratios for all two plasma-treated fabrics increased dramatically with an increase of treated time suggesting that oxidation occurred and a higher level of oxygen-based functional groups (C-O-H, O=C-O)were formed on the surface exposed to He/O2APPJ. The increase of these polar groups is responsible for the higher hydrophibilily of the polyaerylate size. The weight loss result indicates that the weight loss increased with an increase of plasma treatment time. Hlowever, after50s exposure time, the increment of weight losses slow down. The desizing results show that as the helium/oxygen plasma treatment time increase, the PDR has a significant increase after wet desizing. More than99%PDR was achieved after65s plasma treatment followed by a5min wet desizing, whereas only about28%PDR can be reached for the untreated fabrics. Moreover, the PDR of the all samples increases with the increase of wet desizing temperature and time. Meanwhile plasma treatment can not observably decrease desizing temperature but dramaticlly reduce desizing time. |
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