【作者】 俞丹；

【导师】 何瑾馨；

【作者基本信息】 东华大学 ， 纺织化学与染整工程， 2011， 博士

【摘要】 随着电子技术的快速发展,人们生产和生活中使用的电子产品和设备越来越多,各种电子器件都不同程度的产生电磁波辐射,电磁波辐射不仅造成电子产品之间的相互干扰,而且还污染人类生存的空间,危害人类的健康。由于优良的导电性和特殊的结构,表面镀覆各种金属的导电织物可用来屏蔽电磁波辐射和干扰,并且在一些特殊工作环境,可以避免衣物上的静电带来很多严重后果。在传统织物化学镀处理的过程中,为保证织物上化学镀金属层的均匀性以及与织物纤维的结合牢固度,除对化学镀液和敏化、活化溶液本身有较为严格的要求外,织物敏化前还需进行有效的除油和粗化等工序。在本论文中提出了新的导电织物化学镀的前处理方案,采用生态环保的壳聚糖与织物发生物理和化学作用,然后根据壳聚糖吸附重金属的特性将贵金属钯鳌合吸附在织物表面,主要是利用钯盐在壳聚糖上带有的—NH2、—OH的配位结合或静电吸引,从而获得无需Sn2+参与的牢固的活化层,完成一般意义上的活化过程。经活化处理的织物一旦引入化学镀Ni-P溶液中,表面吸附的Pd2+很快被镀液中的还原剂还原成金属钯,并在织物表面原位沉积。这种方法改变了织物与金属之间仅靠物理沉积作用结合的模式,使得镀层结合力更为牢固,导电性更为均匀,另外在减少贵金属钯的用量,减少制备工序,降低成本中也起到了一定的作用。本论文对导电织物的表面电阻、电磁屏蔽效能、壳聚糖对钯离子的吸附机理以及镀层与织物纤维的结合力和抗腐蚀能力等性能进行了重点研究。在整个制备过程中前处理对非金属基体材料化学镀是一个关键,因为非金属材料表面没有催化活性,若不进行前处理将无法实现化学镀,而且,前处理工艺一环扣一环,每个环节效果如何往往难以单独进行判断,需要借助于后续的甚至是通过化学镀效果和镀层性能测试才能推测出其效果。因此,对织物进行的前处理是否有效是化学镀的关键,也是研究的重点。首先对实验所用的壳聚糖进行了理论上的筛选,选用分子量在70000左右、脱乙酰度在90%以上的壳聚糖作为实验材料。在多种无机酸中选择比较适合的作为壳聚糖的溶剂,使壳聚糖溶液具有优良的成膜性,并且为提高壳聚糖整理液的稳定性和与织物的结合力,在其中加入交联剂。采用壳聚糖对涤纶、锦纶、棉和羊毛四种织物进行壳聚糖前处理工艺研究,通过正交实验得出壳聚糖前处理最佳工艺,对于涤纶织物,在壳聚糖浓度4 g/L、醋酸浓度2%、甲醛浓度10 mL/L、浸渍时间10min、轧车压力3 kg/cm2时,壳聚糖整理工艺效果较好,织物电磁屏蔽效能优异。之后分别讨论了几个单因素(如CTS浓度、交联剂浓度、醋酸浓度等)对织物表面方阻值和织物增重率的影响。在活化过程中分析并讨论了溶液pH值和PdCl2浓度对织物表面方阻和对钯离子吸附率的影响。得出壳聚糖对钯离子吸附的最佳条件：PdCl2为45mg/L,pH=2.5,吸附温度60℃和吸附时间40 min。对于锦纶,其化学镀前活化处理的最佳工艺：CTS浓度12 g/L、温度60℃、甲醛浓度12 mL/L、处理时间20 min、醋酸浓度为1%、氯化钯浓度45 mg/L。活化处理时间40min、活化处理温度60℃。棉织物适合的工艺条件：壳聚糖浓度7.5 g/L、柠檬酸浓度2.0 g/L、次亚磷酸钠浓度0.5 g/L温度20℃、时间30 min。最佳活化工艺为：PdCl2浓度为30 mg/L,在pH值为5-6,温度为55℃的条件下处理30 min。羊毛织物壳聚糖前处理的工艺条件：壳聚糖12 g/L,柠檬酸4.5 g/L,次亚磷酸钠1.0 g/L,温度60℃,处理时间10 min。最佳活化工艺为：PdCl2为50 mg/LpH=3,吸附温度60℃和吸附时间40 min。经最佳活化工艺条件处理后对织物进行了XRD、SEM、SPM和FT-IR表征。活化后织物的XRD图谱表明,在织物表面形成了薄且均匀的钯活化层；SPM、SEM的图像观察佐证了这一结论；通过红外光谱测试,谱图出现的特征峰主要显示织物本身的材质。这说明在织物表面沉积的CTS量较少、钯粒子粒径较小,但已能成功引发之后的化学镀。从热重分析TGA来看,活化处理对织物的热性能织影响较小,化学镀处理后使得织物的耐热性能有略微降低。此外,对化学镀后的织物进行了耐磨性、耐腐蚀性和金属镀层结合牢度等测试。结果表明,经过此方法处理得到的电磁屏蔽材料,通过镀层结合力实验发现镀层与基材具有良好的结合牢度和耐磨性能。化学镀整理后,各类织物除了有导电性外,还有非常优异的紫外防护和抗静电性。经计算化学镀后织物的电磁屏蔽效能在10 MHz-20 GHz的范围内均能达到30 dB以上,这相当于屏蔽掉了96.0%以上的电磁波,完全可以满足民用电磁防护用品的要求。接着,本论文通过一些基础性的研究工作为壳聚糖应用于织物上后的活化工艺机理提供了重要的理论基础。吸附实验在CTS前处理后的活化过程中进行,其内容包括：壳聚糖吸附性能的评价,通过平衡吸附实验,计算平衡吸附量,绘制吸附等温线,绘制动力学曲线,对吸附交换容量和吸附速率进行比较评价。应用Langmuir和Freundlich模型对等温平衡吸附数据进行拟合,并通过计算△S、ΔH、ΔG等热力学参数对吸附过程进行热力学分析,对吸附动力学的数据进行拟合。最后探讨壳聚糖对钯离子的配位吸附机理,为选用壳聚糖吸附贵金属在化学镀前处理中的应用提供理论指导。涤纶上壳聚糖对Pd2+的吸附动力学表明CTS对Pd2+吸附反应比较符合二级反应动力学特征,二级速率常数为0.1743 min-1,吸附在经过40 min左右时达到平衡。由此推之此吸附是化学吸附。此外经计算,该吸附反应的表观活化能Ea为18.84 kJ·mol-1,佐证了此吸附为化学吸附。通过Langmuir和Freundlich模型对吸附机理进行模拟,结果表明CTS对Pd2+的吸附在活化液初始浓度为10-50 mg/L范围内更符合Langmuir等温方程式。说明该吸附是单分子层吸附,间接反应出配位吸附是主要吸附过程。热力学结果表明,钯离子在壳聚糖颗粒上的吸附过程是自发过程(ΔG<0),伴随放热(ΔH<0),熵变为正值(△S>0)为化学吸附。最后,本论文以壳聚糖为修饰对象制备了几种壳聚糖衍生物。根据壳聚糖及其衍生物与金属离子配位的研究发现其与金属离子有较好的配位作用。通过引入羧甲基、氨基的方式制备了NOCC和BGC,采用戊二醛和壳聚糖交联的方式制备了GCC,并且采用过硫酸钾为引发剂,制备了壳聚糖与丙烯腈的接枝共聚物CCN。采用FT-IR和13CNMR进行表征。将这四种壳聚糖衍生物在化学镀前处理中进行应用,研究其在提高贵金属吸附性能和降低织物表面电阻值的作用。SEM等表明采用壳聚糖衍生物处理的化学镀织物镀层结构较致密和均匀,金属颗粒较小。同样对经壳聚糖衍生物前处理的织物的电磁屏蔽效能与壳聚糖前处理的相比较,发现屏蔽效能在整个频率范围内都能提高2dB左右(SE>99.9%),所以研究使用壳聚糖衍生物在导电织物化学前处理是对化学镀前处理的有效补充,也是值得进一步探索的方向。本文主要在以下几个方面进行了创新：1.在传统织物化学镀处理的过程中,为保证织物上化学镀金属层的均匀性以及与织物纤维的结合牢固度,通常采用“粗化-敏化-活化”三步法进行前处理。在本论文中提出了新的导电织物化学镀的前处理工序,首次采用生态环保的壳聚糖对织物进行前处理,根据壳聚糖吸附重金属的特性将贵金属钯牢牢吸附在织物表面,从而获得无需粗化、敏化过程,即可成功引发化学镀Ni-P,获得具有优良导电性、电磁屏蔽效能高、使用寿命长的电磁屏蔽用导电织物。过程简单环保,金属镀层更为牢固、致密。2.尝试将化学镀镍磷技术应用于制备导电棉织物和羊毛织物,赋予天然纤维织物良好的导电性和抗静电等性能。而之前在导电织物的制备研究主要集中于涤纶等合成纤维,随着人们自身防护意识的逐渐增强,防电磁辐射织物有机会从特殊领域走向民用市场。因此有必要进一步提高此类织物的舒适性,拓宽导电基材的范围以促进防辐射服装消费。3.早期的一些研究工作主要集中在壳聚糖作为固体吸附剂的应用方面,对于壳聚糖对钯离子吸附的理论研究报道较少,尤其将壳聚糖应用到织物上后对钯离子的吸附性质未见报道。因此本论文通过一些基础性的研究工作为壳聚糖应用于织物上后的配位吸附提供了重要的理论基础。对于吸附机理的理论研究有利于降低贵金属钯的消耗量,节约生产成本。更多还原

【Abstract】 As the rapid increase of electronic devices and communication instruments, electromagnetic interference (EMI) has been a problem for the lifetime and efficiency of the instruments. Due to the good conductivity and special shape, conductive fabrics coated with copper or nickel can be utilized for shielding electromagnetic radiation and interference. Many researches have focused on optimizing pretreatment conditions, continuous efforts should also devoted to improve the conductivity as well as EMI SE by producing an even and satisfactory metal deposition on the textiles.In this study, we took advantages of electroless Ni-P plating to fabricate conductive fabrics for EMI shielding with Chitosan (CTS) pretreatment and Palladium ions activation. This technique has advantages, such as coherent metal deposition, excellent conductivity, shielding effectiness and applicability to non-conductors with a brilliant appearance. Electroless plating (autocatalytic plating) of non-conducting materials must catalytically activate the substrate surface before metal deposit onto themselves. The surface being catalyzed (sensitization and activation) was generally applied to make sure the metal particle could be deposited on it. Chitosan, the N-deacetylated derivative of chitin and selectively absorbs transition metal ions due to the presence of amino groups and hydroxyl groups. Using the metal-adsorbing properties of CTS as an alternative method to prepare conductive fabrics, we successfully immobilized a palladium (Pd) catalyst for electroless metal plating. In this study, we choose CTS with molecular weight about 70,000 and deacetylated degree over 90%. The acid solvents and cross-linker were also selected to obtain the better membrane-forming property on fiber surface.The traditional process for preparing conductive fabrics is etching, sensitization, activation and electroless plating. Compared with the common way, the new process put forward in this study is CTS pretreatment, activation and electroless plating. Pretreatment is a determinant step in metallization by the electroless plating process. This step allows us to establish strong chemical bonds between the substrate and metallic film. Therefore, the important objective of this study is to introduce CTS and strongly absorbs Pd (Ⅱ) ions. The processes of pretreatment for polyester (PET), polyamide (PA), cotton and wool fabrics before electroless plating were investigated. The properties of conductive fabrics such as surface resistance, shielding effectiveness and adhesion of metal deposit to fabrics were investigated deeply. As a critical step in chemical plating of making electromagnetic shielding fabric, a variety of parameters of CTS pretreatment to obtain the anchoring effect on fabrics were investigated. For PET fibers: the best CTS pretreatment condition of PET fabrics is CTS 4 g/L, HAc 2%, HCHO 10mL/L and 10 min with a padding pressure 3 kg/cm2. The amino (-NH2) and hydroxyl (-OH) groups of CTS are the main reason for its ability to absorb metal ions through several mechanisms including electrostatic attraction or chelation, depending on the pH of the solution. The most proper activation process for PET fibers is PdCl2 50 mg/L, pH 2.5,60℃and 40 min. At this condition, the lowest surface resistance and best weight gain of PET fabrics are obtained after common electroless Ni-P plating. For PA fibers: the best CTS pretreatment condition is CTS 12 g/L, HAc 1%, HCHO 10mL/L and 30 min;activation process for PA fibers is PdCl2 45 mg/L, pH 2.5,60℃and 40 min.As for cotton and wool fibers, citric acid (CA) was used as the cross-linker and NaH2PO2 H2Oas catalyst in the CTS pretreatment. The best condition for cotton fibers is: CTS 7.5 g/L, CA 2.0 g/L, NaH2PO2 H2O 0.5 g/L,20℃and 30 min; activation process is PdCl2 40 mg/L, pH 5-6,60℃and 50 min. For wool fibers is:CTS 12 g/L, CA4.5 g/L, NaH2PO2·H2O 1.0 g/L,60℃and 10 min; activation process is PdCl2 50 mg/L, pH 3,60℃and 40 min.Conductive fabrics were prepared and characterized by scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy, thermal analysis (thermogravimetric (TG)) and so on. SEM shows that CTS-Pd is found on the surface of fabrics and effectively activated the electroless plating. FT-IR shows the adsorption of Pd (Ⅱ) ions on CTS is mainly controlled by physical adsorption. The results of TG A indicate that the metal layer on the fabric catalyzed the thermal degradation. The thermal ability is slightly influenced after the metal plating. According to the Schelkunoff theory, better conductivity leads to higher shielding effectiveness. The shielding effectiveness (SE) of the treated fabrics is more than 30 dB range from 100 MHz to 20 GHz. The properties of electroless plating fabrics were evaluated by various standard testing methods in terms of both physical and chemistry performances. Apart from conductitity, the fabrics stands out several benefits like ultraviolet protection and anti-static.Although CTS-supported Pd plays an important role as a catalyst in electroless metal plating on non-conducting surfaces, the metal-chelating mechanism on the textile surface had not been previously determined. The adsorption capability and kinetics of the adsorption of Pd (Ⅱ) on PET fabric treated with CTS have been studied in this study. Batch adsorption experiments were carried out in which the experimental parameters such as the initial metal ion concentration, adsorption time and temperature were varied. Langmuir and Freundlich isotherm models were employed to analyze the experimental data. The best approximation to the experimental data was given by Langmuir isotherm and the maximum adsorption capacity was found to be 1.241mg/gfor Pd (II) ions on CTS. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models. The data correlated well with pseudo-second-order kinetic model, indicating that the chemical sorption was the rate-limiting step. The thermodynamic parameters like Gibbs free energy (△G°), enthalpy (△H°) and entropy (△S°) were also evaluated by applying the Van’t Hoff equation. The results indicated the exothermic nature of the adsorption process. This study offers a general model for study of the kinetics of reactions between chitosan and metal ions on the base of PET fabric.Novel CTS derivatives were synthesized to increase metal ions chelation and metal adsorption capability. Introduction of carboxymethyl groups to CTS was accomplished to prepare NOCC, and dicyandiamide was used as raw materials to prepare BGC. CTS (in solid state) was mixed with glutaraldehyde solution to prepare CTS cross-linking derivative GCC and the grafting of acrylonitrile with CTS was also made as CCN. The structure of products were confirmed by FT-IR and13C NMR spectra. The four CTS derivatives were applied to pretreatment with the aim to increase the density of sorption sites, to broaden the pH value range for metal sorption and increase the sorption capacity. In addition, these noval derivatives’Pd adsorption properties were evaluated in the activation process and the results indicated that different derivatives had their advantages. From SEM characterization, the metal plated surface was more even and exhibited almost complete coverage of the fiber surface. Furthermore, EMI SE of the fabrics produced by CTS derivatives is raised about 2 dB over the whole range of frequency, which means shielding off 99.9% electromagnetic radiation.Therefore, the objective of this study is to develop the high quality of EMI shielding textile materials for protective clothing with improved performance and durability. The technology is friendly to environment, easy to operate and control, of lower production cost, and has strong resistance to risk, which can be applied commercially.The innovations in these investigations are as followed: (1) Electroless plating on fabrics is normally carried out by multistep process which included: etching, sensitization, activation and electroless plating. In order to gain high adhensive metallic coating, the textiles should be etched by KMnO4 or H2SO4. Even then, the metallic layer is intrinsically absorbed by weak van der Waals force, which means physical absorption. To overcome this problem, we have developed an effective method proposed by electroless Ni-P plating with PdCl2 solution and a chelating agent chitosan (CTS). The CTS pretreatment can reduce etching and sensitization steps and control the adsorption by utilizing interactions between CTS and Pd (Ⅱ) ions.(2) A great deal of work has been carried out on synthetic fibers, especially polyester. Comparatively less attention has been paid to natural fibers, such as cotton and wool. In this study, we are aiming to produce cotton and wool conductive textiles for apparel and technical end-uses. The overall results indicated the treatment on natural fibers could provide an effective conductivity and anti-static property. The encouraging results reported in this study open new perspectives for future application of electromagnetic shielding fabrics and the conductive fabrics for smart clothing.(3) The adsorption capability and kinetics of the adsorption of Pd (Ⅱ) ions on fabrics reacted with chitosan has been studied. Fabric was used as the substrate, and surface treatment with CTS was carried out before the uptake of Pd (Ⅱ) ions was studied. This fundamental research will be useful for further applications of chemical plating pretreatment on textiles, which is an important step to produce electromagnetic interference (EMI) shielding fabric.更多还原