Preparation And Properties Of Polypyrrole/Polyvinyl Alcohol Composite Conductive Fiber

Polypyrrole(PPy) was a conductive polymer material which had many good features, such as high electrical conductivity, simple synthesis and cheap. In recent years, manufacturing conductive paper endowed with polypyrrole by in-situ polymerization was becoming one of the research hotspots in conductive material field. When natural plant fiber was used as base material, the mechanical property of conductive paper was very poor, which hindered the application. Polyvinyl alcohol fiber(PVA) was a hydrophilic synthetic fiber which containing many hydroxyl groups. Meanwhile, the mechanical property of PVA was higher than plant fiber and PVA was easy to melt to reinforce mechanical properties of conductive paper. In this paper, 60 ℃ water-soluble(PVA) was selected as the base material to synthesis the PPy/PVA composite conductive fiber, the conductive paper was manufactured by mixing it with plant fibers in a certain proportion. The cationic modification achieved on PVA fiber could improve the the adsorption of PPy and the mechanical property of conductive paper.The PPy/PVA composite conductive fiber(PPy·Fe Cl3/PVA, PPy·APS/PVA) was synthetized via in-situ polymerization using ferric chloride, ammonium persulfate as oxidants, p-toluene sulfonic acid as the doping agent. Furthermore, a variety of analytical techniques was employed to determine the structure, morphology and thermal stability of conductive fiber. Fourier transform infrared spectrum(FT-IR) showed the effect of oxidants on the structure of PVA/PPy, which was mainly due to the different doping level of PPy. Scanning electron microscopy(SEM) and atomic force microscopy(AFM) showed that the morphology of PPy was coralline with Fe Cl3 as oxidant, and the PPy conductive coating was more compact and complete. The morphology of PPy with APS as oxidant was spherical particles, the PPy conductive coating on fiber surface was not complete. The results of X-ray photoelectron spectroscopy(XPS) and elemental analysis showed the doping level of PPy was higher with Fe Cl3 as oxidant. Thermogravimetric analysis(TGA) showed that the thermal stability of PPy·Fe Cl3/PVA was higher than PPy·APS/PVA fiber.A series of composite conductive paper was manufactured by mixing the PPy/PVA conductive fiber with plant fiber in a certain proportion. The effects of preparative conditions on the conductivity and mechanical property of conductive paper were investigated in detail. The optimum preparative conditions were as follows: the content of monomer Py was 40 %(compared to the dry PVA fiber), the mole ratio of PTSA to Py was 1 : 1, the mole ratio of Fe Cl3 to Py was 2 : 1, reaction in ice bath for 5 h, the mass ratio of PPy/PVA conductive fiber to plant fiber was 6 : 4, the drying tempreture was 105℃. The conductive paper manufactured under this condition was excellent in both conductivity and mechanical property. The storage temperature and atmospheric condition had an important influence on the conductivity stability. When exposed to atmosphere at high temperature, PPy tended to be oxidated easily, conductivity decay of paper was serious. Vacuum environment was beneficial to maintain the conductivity stability.Cationic PVA fiber was synthesized via grafting copolymerization with methacryloyloxy ethyl trimethyl ammonium chloride(DMC) as monomers and ammonium ceric nitrate(CAN) as initiator. The influence of the concentration of DMC and CAN, the temperature of reaction on the grafting rate and the charge density was investigated. The results showed that, when the concentration of DMC was 0.6 mol/L, the concentration of CAN was 16×10-3 mol/L and the temperature was 40℃, the grafting rate could reach 41%, the charge density of PVA fibers was 927 mmol/Kg. FT-IR spectra of modified PVA fiber indicate that grafting copolymerization of DMC took place on the surface of PVA fiber. The surface micro topography of cationic PVA fiber, PPy/c-PVA conductive fiber and composite conductive paper was detected via SEM. The photographs showed that: the surface of modified PVA fiber became rough; the adsorption of PPy on c-PVA fiber became more complete; PPy/c-PVA conductive fiber and plant fiber were banded together closely. The surface charge density of c-PVA fiber had an important influence on the conductivity and mechanical property of composite conductive paper. When the surface charge density was 844 mmol/Kg, the surface resistivity of conductive paper could reach 21.55 ?·cm, the tensile strength was 54.2 N·m/g and the folding endurance was 58 times.