Research Of Thermal-Resisting Polypyrrole/Nylon 6 Conductive Composite Fiber

Polypyrrole (PPy) is an especially promising conducting polymer owing to its high conductivity, cheap raw material and ease of synthesis. PPy has been in applications such as rechargeable batteries, electronic device, special coating, electronic textile, electromagnetic shielding material, photo-electrochemical batteries and so on. However, PPy is insoluble and infusible, which restricts its fabrication, and it has poor mechanical properties. In-situ polymerization is to diffuse pyrrole into the matrix of swelling polymer with soft segment, then pyrrole polymerize in the matrix. This method can be used to form the shaped composite material with good mechanical property and high conductivity. Variable environment in the application of PPy has a great impact on its property. The conductivity decrease when the temperature rises, which is an unrecovered destroy to PPy.We prepared PPy/Nylon6 composites fiber by oxidation polymerization of pyrrole in situ in pyrrole-aqueous solution. The effects of various parameters during the processing on the fiber conductivity were investigated in the paper. The results show that FeCl₃·6H₂O can beused as an effective oxidant and the optimal reaction conditions for excellent conducting performance are as follow: Pyrrole concentration 0.05mol/L, the initial mole ratio of oxidant/pyrrole 2.3, reaction temperature 20°C and reaction time 3h, the dopant concentration: 2-naphthalenesulfonic acid 0.02mol/L;p-toluenesulfonic acid monohydrate 0.05mol/L;5-sulfosalicylic acid dehydrate 0.09mol/L.The FTIR spectrums confirm that the composite is composed of PPy and nylon. The addition of dopants improves the conductivity in PPy and PPy/nylon6 composite fiber. The SEM photos show that the composite fiber presents skin-core structure and polypyrrole concentrates on the skin which forms conducting passage. The X-ray diffraction indicates that the addition of PPy don't effect nylon6 fiber's crystallinity for PPy's poor crystallinity. DSC melting curves shows that there is good consistency between PPy and nylon6.Comparisons of mechanical properties of PPy/nylon 6 and nylon6 indicate that the intensity and extensibility in composite fiber is lower than that in nylon 6 fibers which can be neglected. PPy/nylon6 composite fiber remains nylon 6 fiber's regain property and is stable in atmospheric circumstance and some organic solvents. The lack of an exact correlation with conductivity indicates that the mechanisms of thermo-oxidative degradation are complex and the conductivity decay is likely to be caused by a number of mechanisms. PPy/nylon6 composite fiber with dopants has good conductivity at high temperature. The thermal-stabilization mechanism has suggested that the reinforcement of oxygen bonding destroy the ^-conjugation and dopants having acidic substituents should suppress proton dissociation from the N-position of the PPy main chain and keep the ^-conjugation structure by supplying a proton from the acidicgroups.