【作者】 彭淑静；

【导师】 邱夷平；

【作者基本信息】 东华大学 ， 纤维材料物理， 2010， 博士

【摘要】 聚乙烯醇（PVA）在纺织工业中被广泛用作上浆剂。经PVA上浆的棉织物必须经过退浆处理,以满足后续加工（染色、印花、整理）要求。目前常用的退浆方法是使用热水在棉织物表面洗脱PVA,有时加入烧碱或氧化剂如H₂O₂等,该方法不仅耗能高,废水排放量大,而且排出的废水中含有大量的PVA和化学助剂,造成环境污染严重,不符合当今环保的要求,不利于产品的可持续发展,因此有利于生态环境的低温等离子体在纺织制品染整加工中的应用研究引起人们极大关注。如果能将低温等离子体运用于纺织工业的退浆工艺,在退浆工艺阶段就实现对PVA的降解,不仅能大大减少化学助剂用量和PVA废水的排放,还能降低能耗和减少用水,具有重大的环境效益和经济效益。然而,过去大多数等离子体处理过程都是在低压下进行,这不仅需要昂贵的真空体系,而且由于要抽真空,不能实现在线处理,使得较低附加值的纺织品一类的产品成本过高,难以实现工业化处理。与之相比,国际上最近几年来正在积极开发的常压非平衡低温等离子体技术,不需要抽真空,因此可以实现处理过程连续化。到目前为止,进入市场的常压等离子体处理设备中,主要有两种,即介质阻挡放电（DBD）和喷射式等离子体（Plasma Jet）。DBD为电容式,被处理物必须通过两块极板中的狭缝。而喷射式等离子体的活化气体是在喷头里产生,然后喷出来和被处理物接触。常压等离子体处理过程中和低压等离子体处理的一个很大区别在于试样置于外界大气环境中,会吸收外界环境中的水分而使材料保持一定的回潮率。而对于以往的低压等离子技术,试样在处理前需要被干燥以达到所需的真空度,所以不需要考虑水分的存在对处理效果的影响。水分子的存在使常压等离子体的成分及其和被处理物之间的相互作用变得更为复杂。也使得材料的微观结构和各种物理机械性能发生改变,从而影响等离子体的处理效果。PVA是一种水溶性聚合物,在液态水存在或高湿度环境下,其大分子链发生松弛,内部结构及性能明显改变,当PVA的含水率提高到10%以上,其玻璃化温度由68℃降至20℃以下。可见,水分对PVA内部结构和本身物理机械性能有很大的影响。近年来,国内外有关常压等离子体技术对棉织物上PVA浆料的去除有过不少研究。但是,有关水分对常压等离子体退除PVA浆料效果的影响方面目前还尚未有报道。本课题采用本实验室最近从国外引进的喷射式常压非平衡低温等离子体发生器和中科院研发的介质阻挡放电装置,从PVA薄膜到PVA上浆的棉织物系统地研究常压等离子体射流对棉织物退浆效果的影响,并探讨薄膜和织物中存在的水分对PVA刻蚀、溶解性能的影响及其对棉织物本身表面和力学性能的影响。通过一系列的表面分析测试方法,如扫描电子显微镜（SEM）、原子力显微镜（AFM）、傅立叶变换红外光谱（FTIR）及其X射线光电子能谱（XPS）等表面形态和化学分析方法探测PVA薄膜及其织物表面发生的物理和化学变化,通过动态力学热分析（DMA）和X射线衍射（XRD）等方法来测定等离子体处理后PVA薄膜内部微观结构的变化,通过测量薄膜和上浆棉织物的刻蚀失重率及其溶解率来分析等离子体的直接刻蚀效果和对后道水洗退浆效果的影响,通过芯吸高度和白度等测定方法来表征处理后棉织物吸湿性能和白度的变化,通过测定棉纱的拉伸强力和棉织物的低应力机械性能及其表面性能来分析等离子体退浆对织物本身的影响。首先,本文研究了常压射流等离子处理工艺参数（气氛、流量、功率、时间、喷头与薄膜距离、回潮率和垫层）对PVA薄膜刻蚀速率的影响。发现经等离子体处理后,刻蚀速率随功率、氧气流量、氦/氧混合气体流量及其薄膜回潮率的增加而增加;随处理时间和氦气流量的增加先上升后下降;随喷头与被处理样的距离增加而下降,当距离超过6mm,刻蚀速率几乎为0。研究还发现,不同垫层（塑料片、钢片和铝板）导热性能对刻蚀速率影响很小。在常压等离子体刻蚀作用下,PVA薄膜表面变得粗糙,表面氧元素含量增加,从而导致极性基团含量增加,薄膜吸湿性能提高。其次,为了研究水分对等离子体处理过的PVA薄膜溶解性能的影响,本文采用常压射流等离子体处理装置对回潮率分别为2.5%、9.3%和78.3%的PVA薄膜（在相对湿度分别为10%、65%和98%的环境中平衡24小时）进行处理,在氦气中加入氧气作为工作气体,处理时喷头温度约为60℃,处理功率为100W,处理速度为2mm/s。处理过程中采用塑料片、钢片和铝板三种导热系数不同的垫层,研究由此引起薄膜表面聚积温度的高低对处理后薄膜表面形貌的不同变化和对溶解性能大小的影响。考虑到由于加热引起的结晶度变化对处理效果可能造成的影响,我们对PVA薄膜退火处理,并与等离子体处理效果进行比较。发现经等离子体处理后,相对湿度为65%和98%的试样含氧量增加,而相对湿度为10%的试样略有下降;与相对湿度（10%和65%）较低的试样相比,相对湿度为98%的试样溶解性能最差。尤其经塑料片垫层处理过的薄膜更是如此。溶解性能的下降主要是由于水分增塑作用下,PVA薄膜的玻璃化温度远低于处理薄膜的表面温度,经等离子体高能粒子轰击后,裂解形成的小分子链段在无定型区重新排列,PVA薄膜表面发生重结晶,结晶度明显增加引起的,这点可以由SEM和XRD测试得到验证。为了研究水分对等离子体处理后织物的退浆效果,本文选择含PVA浆料的棉织物作为模型,在相对湿度分别为10%,65%和98%的大气环境中平衡24小时后,将棉织物置于铝板上,采用氦/氧常压射流等离子体处理,再经水洗,水洗温度为60℃。研究表明,处理后棉织物的退浆率增加,退浆时间缩短,在同样的处理条件下,相对湿度为10%的棉织物退浆效果最佳,该织物经64s等离子体处理后水洗20分钟纤维表面几乎和未上浆织物一样干净。棉织物退浆率的提高主要是由于等离子体的刻蚀失重和PVA大分子链断裂及含氧极性基团含量增加引起的。在等离子体高能粒子作用下,棉纤维表层覆盖着的蜡质、果胶等共生物发生氧化分解反应,织物的吸水性得到改善。此外,等离子体处理后织物的单纱强力均没有下降。在研究了常压等离子体射流对PVA浆料去除效果后,本文进一步探讨了棉织物经等离子体退浆处理引起的低应力机械性能及其表面性能变化。在等离子体的刻蚀作用下,棉纤维表面变得粗糙,三种相对湿度的棉织物表面性能包括表面摩擦和表面粗糙度均有所增加,其中相对湿度为98%的试样粗糙度最大,这点由AFM测试结果得到验证。增加的表面粗糙度进一步加大了纤维或纱线间的摩擦,阻碍了织物的应力变形及其变形回复能力,从而导致棉织物的低应力机械性能（拉伸、剪切和压缩性能）增大。最后,本文还研究了介质阻挡放电（DBD）中处理时间对上浆棉织物前处理效果的影响,并与常规前处理工艺进行比较。四组试样分别经氩气/氧气等离子体处理1、2、4和6分钟,再经热水和冷水洗涤,水洗温度分别为60℃和25℃。研究表明等离子体处理时间对刻蚀以及退浆效果有显著影响。通过SEM观察发现处理后棉织物表面的PVA浆料被打碎,随着处理时间的延长,纤维变得粗糙甚至出现裂痕。织物的热水洗退浆率增加,但冷水洗退浆效率无明显提高。处理后棉纤维上蜡质的连续覆盖层状态被破坏,织物芯吸高度增加,甚至优于常规煮炼的芯吸效果。经过等离子体处理的织物白度没有明显改善。此外,短时间的DBD处理并不会降低棉织物的单纱强力。因此我们得出,常压DBD等离子体处理棉织物可以达到常规退浆煮炼的效果。更多还原

【Abstract】 Poly（vinyl alcohol） （PVA） is widely used in textile industry as a sizing agent. But cotton fabrics treated with PVA have to be desized to meet the subsequent processing （dyeing, printing and finishing） requirements. In conventional desizing process, cotton fabrics are washed with hot water and sometimes NaOH or oxidant such as H₂O₂ is used to remove PVA. It is not only water and energy consuming but the wastewater from the textile plant contains large quantities of PVA and oxidant agents, resulting in serious environmental pollution. Obviously, this conventional desizing process is unable to meet requirement of environmental protection and quite adverse to the sustainable development of textile industry. For this reason, the application of environmentally friendly low-temperature plasma is of great interest to the textile industry. If plasma treatments could degrade PVA in the desizing process, both chemical agents and PVA concentration in the wastewater would be significantly reduced. Meanwhile, the consumption of energy and water could be greatly decreased. Therefore, it has great environmental and economical benefits.However, most of the previous plasma treatments were carried out at low pressure, which can not be integrated into the production line due to existence of the vacuum system. It is thus economically infeasible for industrial treatment of low cost products such as most of the textiles. On the other hand, the recently developed non-equilibrium low temperature surface treatment at atmospheric pressure can be directly added on to the processing line. So far, there are two main types of atmospheric pressure plasma equipments, namely dielectric barrier discharge （DBD） and plasma jet in the market. DBD is capacitive and the treated materials have to pass through a narrow slit between two polar plates, while plasma jet has no such limitation in substrate shapes. One of the main differences between a low-pressure plasma treatment and an atmospheric pressure plasma treatment is that in atmosphere, the substrate material may absorb significant amount of water which may potentially influence the plasma treatment effects. But it does not need to be taken into account in low pressure plasma treatment since all the moisture will be removed before the treatment chamber could reach the required degree of vacuum. The existence of water molecules could lead to a more complicated interaction between active species in plasma and substrate surface, which could alter the microstructures and mechanical properties of materials.Poly（vinyl alcohol）（PVA） is a water-soluble synthetic polymer and its macromolecular structure and physical properties change significantly when in contact with liquid water or high humidity due to the loosening of the intermolecular bonds. It is proposed that the glass transition temperature （Tg） of PVA will drop from 68°C to below 20°C when the moisture content increases by more than 10%. Clearly, water greatly affects the internal structure, physical and mechanical properties of PVA. However, recent researches only focus on atmospheric pressure plasma desizing effect of PVA on cotton fabric and no systematic study has been reported about how moisture pre-existed in PVA could influence the desizing of PVA by means of plasma treatments.This research is aimed to employ the atmospheric pressure plasma treatment on PVA size removal and study the influence of moisture on the desizing effect. The effect of moisture on etching and solubility of PVA film by atmospheric pressure plasma treatment is studied and the desizing effect of cotton fabrics with different moisture regain is discussed systematically based on the results of various surface analysis, namely scanning electron microscope （SEM）, atomic force microscopy （AFM）, x-ray diffractometry （XPS）, dynamic mechanical thermal analysis （DMA）, x-ray diffraction analysis （XRD）, wicking height, weight loss and solubility measurement.Firstly, the influence of various processing parameters on etching rate of PVA film by APPJ is investigated, including gas type, gas flow rate, output power, treatment duration, jet to substrate distance, moisture content and the underlining material. The etching rate increases as the output power, the oxygen flow rate, the flow rate of helium/oxygen mixed gas and the moisture regain increase. As the treatment duration and the helium flow rate increase, the etching rate increases initially and then decreases. The etching rate decreases as the jet to substrate distance increases and diminishes when the distance is above 6 mm. Meanwhile, the difference in thermal conductivity of underlining materials （plastic sheet, steel sheet and aluminium plate） has little effect on the etching rate. After the plasma treatment, the surface of the PVA film becomes rough and more polar groups are introduced, resulting in enhanced hydrophility.To investigate the relationship between the moisture and the solubility of the PVA film during plasma treatment, atmospheric pressure plasma jet （APPJ） is used to treat PVA films with moisture regain （MR） of 2.45%, 9.32% and 78.31% corresponding to 10%, 65% and 98% relative humidity （RH）, respectively. Three substrate underlining materials including plastic sheet, steel sheet and aluminum plate are selected. Helium/oxygen mixture is used as the working gas. The treatment nozzle temperature is about 60°C, the output power is 100 W and the sample moving speed is about 2 mm/s. Another group is annealed at 140°C for 20 min to discern the thermal effects from those due to plasma treatment. It is found that the surface oxygen concentration increases for the plasma treated films with 65% and 98% RH and decreases for the plasma treated films with 10% RH. Among the three plasma treated samples, the one with 98% MR has the highest etching rate but the lowest solubility, especially for the samples underlined with plastic sheet during the plasma treatment. The decrease of solubility could be resulted from plasma enhanced surface crystallization of PVA as shown in SEM images and XRD analysis.To investigate the influence of moisture absorption on the effectiveness of plasma desizing, PVA sized cotton fabric is chosen as a model system. Placed onto aluminum plate, samples with three relative humidities （RHs） （10%, 65% and 98% respectively） are treated with APPJ using mixed gas of helium/oxygen and then subjected to water washing at 60°C. Solubility measurement reveals that the percent desizing ratio （PDR） increases and the washing time is shortened. Fabric with 10% RH had the highest desizing efficacy and the fiber surfaces are nearly as clean as the unsized fibers after 64 s exposure plus 20 min washing. The improvement of PDR is due to etching induced weight loss, macromolecular chain scission as well as increased oxygen-containing polar groups. After the plasma treatment, the wicking ability of cotton fabrics is improved with the removal of wax and pectin on fabric surface caused by bombardment of plasma species. In addition, no significant decrease in single yarn tensile strength is observed for the plasma treated yarns.The influence of moisture on low-stress mechanical and surface properties of treated cotton fabric is also studied. Experimental results indicate that after the plasma treatment, surface properties such as surface friction （MIU） and surface roughness （SMD） increased for all three treated fabrics, especially for fabric with 98% MR as verified by AFM results. The enhancement of surface friction （MIU） increased interyarn or interfiber friction, hindered fabric stress deformation and recoverability and consequently led to an increase in low-stress mechanical properties, such as tensile, shear and compression properties.Finally, the relationship between DBD plasma treatment time and desizing effect for a cotton fabric is determined and compared with the conventional pre-treatment process. Four groups are treated by argon/oxygen DBD with treatment durations of 1, 2, 4 and 6 min respectively, followed by hot （60°C） and/or cold （25°C） wash. It is found that plasma treatment time has a significant influence on the etching effect and desizing efficacy. SEM shows that PVA on the fabric surface is broken into pieces after short time treatment. The fiber surface becomes somewhat rough and even micro-cracks appear as the treatment time prolongs due to intensive plasma etching. Solubility measurement reveals that plasma treatment increases PVA solubility in hot washing but less effective in cold washing. Wicking tests indicate that the capillary heights of plasma treated fabrics increase significantly due to the destruction of continuous cuticle layer, even larger than that of conventional scouring. The whiteness of the treated fabrics improves slightly. The yarn tensile strength test results show that short DBD exposure time has no negative effect on fabric tensile strength while the long treatment time may slightly reduce the fabric tensile strength. Therefore, the DBD treatment may assist the conventional desizing and meet scouring requirements.更多还原