| The electromagnetic radiation can be found in every corner with the development of technology and the growing amount of electronic products and devices, which jeopardize health of human beings. Conductive textiles, with antistatic property, were applied widely to shield electromagnetic radiation. However, etching, sensitization activation were the critical pretreatment procedures for traditional electroless plating to fabricate conductive textiles. Therefore, one new pretreatment proposal was submitted in this paper where chitosan and polyvinyl alcohol were used to fabricate self-catalyzed film on fabrics surface, thereby avoiding etching and sensitization process and reducing PdCl2consumption during activation process. This method has promising market value as it simplifies the traditional process significantly and reduces environment pollution and production cost.Chitosan consists of-NH2and-OH group, which has the nature to absorb heavy metal ions like pd2+.However, the pure CS film was brittle with poor mechanical properties and cannot be used in acidic environment. In this case, aldehydes were added into CS as cross-linking agent to promote film property. But during application, the film would release free formaldehyde which cannot meet the environmental standard these days.Considering the toxicity of aldehydes and environment safety, polyvinyl alcohol (PVA) was carried out in preparing CS/PVA blending film.The hydrogen bonds existed between CS and PVA can improve the two-phase compatibility, which is beneficial to form blending film with interpenetrating networks (IPN) structure. Compared to the traditional activation where40-300ppm PdC12was needed, the self-catalyzed film in this work can be fabricated by adding8ppm PdCl2into blending film with the absorption of-OH and-NH2to metal ions and triggers electroless nickel plating successfully on fabrics afterwards.Through orthogonal and single factor experiments, the results demonstrated that strength of complex film decreases with the increase of PVA concentration while the elongation goes up, leading to the improvement of application properties. The optimum conditions to prepare complex film were shown as below:PVA/(CS+PVA)(mass concentration)20%, dry at80℃for20min.From Fourier transform infrared (FT-IR) test, red shift was observed at3428cm-1corresponding to-OH and-NH2stretching vibration, while narrowing and blue shift occurred at acylamino bending vibration peak (1553cm-1) which means strong hydrogen bond interaction was formed between CS and PVA. The film morphology was characterized by scanning electron microscopy (SEM), which shows that CS and PVA can mix evenly to prepare smooth blending film. Also, the tensile strength of blending film was tested. From several above tests, it can be speculated that CS/PVA complex film with strong hydrogen bond interaction and IPN structure was successfully prepared in this study.Then, electroless nickel plating on PET and PA fabrics surface with self-catalyzed film was analyzed. Through orthogonal and single factor experiments, the optimum conditions for PET and PA nickel electroless plating were nickel sulphate40g/L, sodium hypophosphite25g/L, sodium citrate17g/L, sodium acetate17g/L, temperature45℃, time57min; nickel sulphate37g/L, sodium hypophosphite25g/L, sodium citrate17g/L, sodium acetate17g/L, temperature45℃, time57min.The square resistance of nickel-plated PET and PA fabric is40-160mΩ/cm2and40-180mΩ2/cm2, respectively by adopting the optimal operating conditions.SEM photos reveal that compact and uniform metal layer was formed on fabrics after electroless plating.The thermal stability of fabrics before and after plating was characterized by thermal gravity (TG) investigation. It shows that remainder ratio of nickel plated fabrics is much higher than that of untreated fabrics, which means metal layer can hinder polymer chain activation to some extent and block the volatilization of degradation products. The shielding effectiveness (SE) test illustrates that SE of nickel plated PET and PA fabrics can reach to40-80dB and55～75dB, respectively, which is higher than the civil and industrial standard(30dB)... |
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