| 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.
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