【作者】 高志强；

【导师】 邱夷平；

【作者基本信息】 东华大学 ， 纺织材料与纺织品设计， 2010， 博士

【摘要】 等离子体处理是一种物理和化学方法相结合的气态处理技术,与传统的物理化学方法相比,具有低污染、低能耗、不耗水、不用化学试剂等优点。尤其是低温等离子体中高能量的电子及其他激发态或电离态的粒子仅在被处理物体表面几十纳米深度范围内引起物理和化学变化,而较低的气体温度使得材料内部的性质不发生变化,因此,低温等离子体表面处理可以用于高分子材料的表面改性。等离子体作为一种环保型的高分子材料表面改性技术,在材料预处理和后整理等方面的应用越来越受欢迎,已经呈现出其有效性和舒适性,具有广阔的应用前景。在各种等离子体处理设备中,常压等离子体处理技术由于不需要使用复杂昂贵的真空设备,并可实现处理过程连续化,成为今后等离子体技术的产业化发展的方向。等离子体刻蚀去除了材料表面的弱层或低分子片段从而产生链段剪切。等离子体中的活性粒子可以打断材料表面的化学键再形成交联。等离子体刻蚀速率主要受处理条件的影响,概括来讲,等离子体的刻蚀效果主要受等离子体处理时间、处理功率、气体种类以及气体流量、喷头与试样的距离以及试样的回潮率和溶剂等的影响。但是,至今还没有关于这些处理因素对等离子体刻蚀速率影响方面系统的研究报道。本研究将常压等离子体处理技术应用于聚酰胺6膜的表面改性处理,以改善他们的表面能、润湿性以及粘接性能,从而进一步研究等离子体处理条件对材料刻蚀性的影响。通过一系列的现代表面分析测试技术,如接触角、扫描电子显微镜（SEM）、原子力显微镜（AFM）、X射线光电子能谱（XPS）以及剥离强度（T-peel strength）等,在分析等离子体处理后材料表面的性能随处理条件变化的基础上,对常压等离子体对材料的刻蚀速率等进行了系统深入的研究。本文首先研究了等离子体处理时间对刻蚀效果的影响。随着等离子体处理时间的增加,刻蚀速率先增大而后又减小,这主要是由于等离子体刻蚀主要作用于材料的非晶区,随着处理时间的增加,非晶区在逐渐减小,且随着刻蚀的进行有一部分刻蚀掉的颗粒又会沉积在试样的表面,从而使刻蚀速率减小。亲水性测试显示试样的亲水性得到改善即接触角显著减小,但是接触角随着处理时间的增加变化不是很明显只是稍微有所减小而已。AFM观察发现处理后试样的表面粗糙度增加。XPS显示随着处理时间的增加在试样表面引入了更多的含氧基团。本文还研究了常压等离子体处理功率对刻蚀效果的影响。等离子体刻蚀速率随着等离子体处理功率的增大而增大。这主要是由于随着处理功率的增大,等离子体活性粒子的密度变大、能量增大,促进了等离子体刻蚀的速率。亲水性测试表明等离子体处理后试样的亲水性增加,即接触角显著减小,且随着处理功率的增大,接触角减小,但是减小的趋势减缓。XPS表明处理后试样表面的羧基和羟基增多,因此试样表面的氧含量增加而碳含量降低,处理功率越大,含氧基团越多。随着等离子体处理功率的增大,AFM显示试样表面的粗糙度增加,失重也增加。为了研究常压射流等离子体中气体成分对处理效果以及刻蚀性的影响,选择纯氦气、氦气+1%氧气、氦气+2%氧气为工作气体。聚酰胺6膜经等离子体处理后,Ols的强度随着混合气体中O₂含量的增加而增大,试样表面粗糙度也随着O₂含量的增加而增大,表面的含氧量和亲水基团都增加,从而使接触角更小,提高了剥离强度。当混合气体中氧气含量增加后,等离子体刻蚀速率增大,这主要是由于随着氧气含量的增加,等离子体气体中氧离子、原子等的密度增加,促进了氧活性粒子与材料的化学反应从而使刻蚀速率增大。随着等离子体处理时间的增加,处理后试样的剥离强度也是增大的,经过相同的处理时间,氦气+2%氧气等离子体处理后试样具有最大的剥离强度。本文还研究了常压等离子体喷头与试样距离对刻蚀效果的影响。刻蚀速率随着喷头与试样距离的增加先增大然后减小。当喷头与试样的距离小于1mm或大于6mm时,等离子体刻蚀速率几乎是零,而当距离为2-3 mm时,刻蚀速率是最大的。这是由于当喷头与试样的距离太小时,喷头喷出的气体几乎全部被试样阻挡,基本是沿着试样表面平行喷出起不到刻蚀的作用。但是当喷头与试样的距离太大时,等离子体活性粒子由于碰撞寿命会很短,因此,活性粒子的活性在到达材料表面时已经基本消失。在喷头与试样的距离为2 mm或3 mm时,接触角比原样有所减小。但是当喷头与试样的距离为1 mm或6 mm时,接触角基本没有变化。喷头与试样的距离为2 mm或3 mm时,剥离强度增大,当距离为2 mm时剥离强度是最大的。但是当喷头与试样的距离为1 mm或6 mm时,剥离强度基本没有变化,这与SEM结果一致。本文还研究了氦气/四氟化碳常压等离子体对聚酰胺6刻蚀性的影响。在等离子体短时间处理时,接触角减小,剥离强度增加,同时伴随着试样表面的氧含量的大幅增加和氟含量的小幅增加。然而,当等离子体处理时间增加时,试样表面的氟含量的大幅增加和氧含量的小幅增加,由于含氟基团具有一定的拒水性,因此试样的接触角有所增加,剥离强度减小。此外,随着处理时间的增加,试样表面的粗糙度逐渐增加而等离子体的刻蚀速率是逐渐减小的,这主要是由于等离子体对材料的非晶区的刻蚀速度远大于其对晶区的刻蚀速度,随着处理时间的增加,非晶区在减小,且随着刻蚀的进行有一部分刻蚀掉的颗粒又会沉积在试样的表面,从而使刻蚀速率减小。常压等离子体处理和低压等离子体处理的一个很大的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,使等离子体处理效果受到影响,因此本文对聚酰胺6的回潮率对处理效果的影响进行了研究。研究发现:材料回潮率越大,等离子体处理后材料表面的粗糙度越大且刻蚀速率也越大。材料吸收的水分促进了等离子体的刻蚀,这主要是因为吸收的水分使得材料的非结晶区增加而结晶区减小,而等离子体刻蚀主要是对非晶区的刻蚀。本文还研究了乙醇对常压等离子体处理聚酰胺6的影响。等离子体直接处理的试样比原样具有更小的接触角,而乙醇预处理的试样处理后和原样的接触角无显著差异。等离子体直接处理的试样具有最大的表面粗糙度,含氧基团增加,剥离强度增大。而乙醇预处理的试样其剥离强度与原样无显著差异。等离子体直接处理的试样重量减小,而乙醇预处理的试样经等离子体处理后重量稍有减小,但是仍然比原样的重量重,这主要是由于乙醇预处理在试样的表面形成了一层保护膜,在等离子体处理中有抑制等离子体刻蚀的作用。综上所述,本论文通过一系列先进的表面分析测试手段,对等离子体处理后的聚酰胺6的表面性能进行了分析研究,并对常压等离子体刻蚀进行了深入探讨。本文认为除了设备自身的各种处理参数的影响之外,等离子体刻蚀还受被处理材料的回潮率和不同溶剂的影响。在实际生产应用中,我们可以通过控制材料回潮率并采取最优工艺参数,促进等离子体与材料表面的相互作用,使等离子体刻蚀获得最佳效果。更多还原

【Abstract】 Plasma treatment is a gaseous technology which combines physical and chemical reactions. Compared with traditional physical and chemical treatments, it has advantages of low pollution and low energy consumption without involving water and chemicals. In low temperature plasmas, electrons with high energy and other excited or ionized particles initiate physical and chemical reactions only on the surface of the substrate with the thickness of several nanometers, leaving the bulk properties unchanged. Therefore, as an environmentally friendly surface modification technology, low temperature plasma treatments have been widely used to modify polymer surfaces.Recently more attention has been paid to atmospheric pressure plasma treatment due to advantages such as no need for a vacuum system, online process capabilities, high efficiency and scalability to a larger area. Plasma etching removes a weak boundary near the surface of the polymers or the low-molecular-weight fragments formed as a result of chain scission induced by the plasma. The active species in radio frequency plasma have the ability of breaking primary chemical bonds and inducing cross-linking. The plasma etching rate is related to the chemical structure of the polymer at a given plasma treatment condition. It is also greatly affected by the plasma treatment conditions such as treatment duration, output power, gas flow rate, jet to substrate distance and moisture regain. However, no systematic study has been reported on how these treatment conditions influence the etching rate.This research is aimed to employ the atmospheric pressure plasma treatment on polyamide 6 （PA 6） films to improve their surface properties including the enhancement of wettability, surface energy and T-peel strength. The change of the surface properties after atmospheric pressure plasma treatment and the etching effect of the treatment were studied and the mechanisms were discussed systematically based on the surface analysis method such as contact angle measurement, scanning electron microscope （SEM）, atomic force microscopy （AFM）, X-ray photoelectron spectroscopy （XPS） and T-peel strength.In this study, atmospheric pressure plasma is used to etch the surface of PA 6 films to investigate the etching behavior of PA 6 film surface by APPJ with helium/oxygen gases with different treatment time. The etching rate first increases and then decreases as the plasma treatment time increases. The hydrophilicity tests reveal the improvement of the hydrophilicity of the surface as the decrease of water contact angle measured after the plasma treatments, but the values do not change significantly with longer treatment time although slightly smaller values are observed for time in the 60-180 s range. AFM showed that the surface roughness increased after the plasma treatment. The deterioration of the surface morphology is more severe after a longer treatment time as rougher surfaces are observed due to the plasma etching effect. XPS results show a significant increase in oxygen content with the addition of carboxylic and hydroxylic groups and a decrease in the carbon content of the surface. It can be concluded that more oxygen containing polar groups are introduced after longer plasma treatment time.The influence of plasma treatment power on the atmospheric pressure plasma treatment is also investigated. The hydrophilicity tests reveal that the water contact angle decreases significantly after the plasma treatment. A higher treatment power results in a lower water contact angle. XPS results show a significant increase in oxygen content with the addition of carboxylic and hydroxylic groups and a decrease in the carbon content of the surface. AFM shows that the surface roughness and the weight loss also increase with the increase of plasma treatment power.To investigate the relationship between the etching effect and the gas composition of atmospheric pressure plasma treatment, pure helium, helium + 1% oxygen and helium + 2% oxygen are used as the working gases, the output power is 40 W, and the treatment time was 30 s. The He and He + O₂ plasma treated polyamide 6 films show increased surface roughness, surface oxygen contents and hydrophilic polar groups, leading to lower water contact angles, and higher T-peel strength than those of the control. When the amount of oxygen increases from 1% to 2% in the plasma gas mixture, all the above favorable effects are further enhanced. Plasma etching rate is promoted as the amount of oxygen in the plasma gas mixture increases. The T-peel bonding strengths of the plasma treated PA 6 films is raised steadily as the treatment time increases and among three types of gas mixture, He + 2% O₂ plasma has the highest bonding strength for the same duration of plasma treatment.PA 6 films are treated using atmospheric pressure plasma with different jet-to-substrate distance. Decrease in contact angle is observed under 2 mm or 3 mm of jet-to-substrate distance. However, the contact angle does not change when jet-to-substrate distance is 1 mm or 6 mm. It can be seen that the peel strength increases when jet-to-substrate distance is 2 mm or 3 mm, and the peel strength is the largest when jet-to-substrate distance is 2 mm. However, the peel strength does not change when jet-to-substrate distance is 1 mm or 6 mm. These results correspond to the SEM results. The etching rate increases first and then decreases as the jet-to-substrate distance increases. When the distance is smaller than 1 mm or larger than 6 mm, the plasma etching rate is almost zero. When the distance is 2 - 3 mm, the etching rate is the largest.The etching behavior of He/CF₄ atmospheric pressure plasma treatment to PA 6 film surfaces is also investigated. For a short treatment time, a decrease in contact angle and an increase in T-peel strength are observed corresponding to a relatively large increase in surface oxygen content and relatively small increase in surface fluorine content. However, as the treatment time increases further, the contact angle increases and T-peel strength decreases accompanied by a large increase in fluorine content and a relatively small increase in surface oxygen content. In addition, the surface roughness continuously increases and the plasma etching rate steadily decreases as the plasma treatment time prolongs. 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. The influence of the moisture regains of PA 6 film on plasma etching behavior is also studied. It is found that a higher moisture regain leads to greater surface roughness and a higher etching rate. Moisture absorbed into the film facilitated the plasma etching reactions on the PA 6 film surfaces, because the moisture in the film increases the amorphous area and breaking up the intermolecular bonds in the amorphous region.In this part, the effect of ethanol on the atmospheric pressure plasma treatment is investigated. The plasma directly treated sample has a significantly lower water contact angle than that of control while the ethanol pretreated sample has a water contact angle similar to that of the control. The surface of the plasma directly treated samples has the greatest roughness. Most of the oxygen containing polar groups increase （such as -C-O-, CONH and -COO-） after the plasma treatment. The T-peel strength increased after plasma treatment. However, with the ethanol pretreatment, the T-peel strength values for the samples are similar to that of the control. This is mainly due to the ethanol pretreatment quenches the etching effect of the films in plasma treatment.In conclusion, polyamide 6 films have been studied through surface analysis methods after atmospheric pressure plasma treatment. The treatment effect can be optimized and the etching effect of the atmospheric pressure plasma treatment can be promoted through selecting most suitable process parameters to optimize the material surface modification.更多还原