Development and Fabrication of Conductive Metallic Thin Films on Polyether Ether Ketone Monofilament in Wet Chemical Method

Abstract

The aim of this work is to develop and fabricate conductive metallic silver thin films on polyether ether ketone (PEEK) monofilament surface. It was coated with silver particles using wet chemical method after being treated with low-pressure glow discharge plasma of gases like air, nitrogen, oxygen, etc. at a definite condition of plasma parameters. The wet chemical method was based on the use of metallic salt silver nitrate (AgNO3) and ammonium hydroxide (NH4OH), which are well-suited to form a silver diamine complex and tetra ethylene pentamine (TEPA) used as an adhesion promoter. Catalytic silver was used to coat the modified monofilaments and after chemical reduction, the cationic silver transforms into metallic silver particles on the filament surface. The concentration of AgNO3 and reducing agent are varied at different stages of wet chemical method. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX) analysis were used to observe the morphology of the silver particles and characterize the elemental analysis of the silver coated filaments respectively. The silver particle size was determined by ImageJ software. The atomic force microscopy (AFM) was used to monitor the surface roughness of the plasma treated and silver coated filament. The oxygen/carbon (O/C) ratio on the plasma treated surface was determined by x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) pattern was used to find out the crystallite size of the PEEK and silver particles. The thermogravimatric analysis (TGA) is performed to find out the thermal stability and silver percentages present on silver coated monofilaments. Electrochemical impedance spectroscopy (EIS) analyzer was used to determine the electrical resistance on dependency of frequency through the silver coated PEEK monofilaments and alternating current (AC) conductivity is measured. To find out how the modification affects the mechanical properties of plasma-modified and silver-coated PEEK monofilaments, universal strength tester was used. The coated monofilaments were also integrated into textile to investigate the capability of resisting the friction during sewing of silver coated monofilaments into the cotton woven plain fabric. PEEK monofilament surfaces have been rough due to low-pressure glow discharge air, N2, and O2 plasma treatment. The roughness of plasma treated monofilaments is higher than the unmodified surface as well as the O/C ratio is increased on the plasma treated surfaces of the monofilaments. Both exhibit synergistic effect on plasma modified surface for adhesion of metallic silver particles. The particles are distributed on plasma modified surface homogeneously and covered the surface as thin films. The roughness of the plasma modified surface has been reduced after deposition and dispersion of silver particles on the modified surface. The characteristic diffraction peaks of PEEK are not remarkably altered by covering the surface with silver nanoparticles. The breaking force and elongation of plasma treated and silver coated monofilament are not significantly changed in comparison with the normal monofilament. The thermal decomposition of normal PEEK and plasma modified-silver coated PEEK both exhibit above 500 °C which indicates thermal behavior has not been remarkably changed. In terms of electrical properties, AC conductivity was increased with the increment of silver percentages on plasma modified-silver coated surface. The increment of silver wt. (%) on the surface of the plasma modified PEEK monofilament has remarkably changed and turned it from insulating to conductive behavior. The electrical conductivity of silver thin film coated monofilament increases with the increase of concentration of AgNO3 and the silver contents (wt.%) on the surface of plasma modified PEEK monofilament. A pronounced non-linear dependence of electrical conductivity is observed on the silver coated PEEK monofilament. The surface morphology, roughness, particles distribution, elemental composition and apparent silver content (wt.%) of O2 plasma modified-silver thin film coated PEEK monofilament intensely influences the electrical conductivity over air and N2 plasma modified-silver coated PEEK monofilaments. Finally, silver thin film coated PEEK monofilament has been integrated into woven fabric to observe resistance of friction between coated filament and fabric during sewing manually. The electrical resistance was measured after integration into textile. The electrical resistance remains stable within range, which indicates that the silver coated monofilament can be integrated into textile and used as conductive threads for smart textiles.