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In situ polymerization is a prominent current topic in the research of skin-core structure polyaniline (PANI) conductive fibers owing to its advantages such as the convenience of preparation and high conductivity of fiber, but it is difficult to realize the continuous fabrication of conductive fibers using this method. In our previous work, we presented a novel method based on in situ polymerization and achieved the continuous fabrication of conductive yarns. In order to reduce the consumption of raw materials such as aniline, doping acid, and oxidant in the preparation, a further improvement is proposed in this paper. Electrical conductive silk fibroin (SF) yarns covered with PANI were prepared by using an improved method based on in situ polymerization. The results show that the improved method has lower consumption than the previous method, and the reduction of raw materials can reach more than 90% compared to the previous method. The structure and properties of the treated SF yarns were studied in detail. The treated SF yarns characterized using scanning electron microscopy and Fourier transform infrared spectroscopy improved the surface of the SF fibers and the gaps between them were covered by conductive PANI; further, interactions such as van der Waals' force, electrostatic interaction, and hydrogen bonding existed between the SF macromolecules and PANI. Thermogravimetric analysis indicated that the thermal stability of the treated yarns was reduced owing to the existence of PANI. The treated yarns exhibited good conductive properties; with the increase in oxidant concentration, the conductivity of coated yarns increased first and thereafter decreased; the maximum conductivity of coated yarn could reach 60 S/m, and the maximum conductivity of PANI was as high as 180 S/m. Compared to the SF yarn, the breaking strength, breaking elongation, and initial modulus of coated yarns were reduced and the loss was increased with the increase in oxidant concentration.

With the development of wearable sensing technology, increasing attention has been given to flexible wearable sensors with textile structures. With a change in the coil structure, conductive knitted fabric can show satisfactory strain sensing performance and can be used to monitor human activities and physical signs. In this paper, polyaniline (PANI)/cotton conductive knitted fabric was prepared via the deposition of a PANI conductive layer on the fabric surface via in situ polymerization of aniline. The surface morphology, chemical structure, electrical conductivity and mechanical properties of the conductive knitted fabric were investigated, and a flexible fabric strain sensor was fabricated with the conductive knitted fabric as a sensing element. In addition, the sensor is applied to monitor the state of human activity/signs. The results demonstrate that the resistivity of the conductive knitted fabric is reduced by more than 8 orders of magnitude compared with the untreated cotton fabric to 0.275 × 103 Ω cm The conductive knitted fabric shows satisfactory strain sensing performance with high linearity and a maximum gauge factor of more than 30. The strain influences the sensing repeatability of conductive knitted fabric. If the strain is less than 10 %, the repeatability is satisfactory, and if the strain increases to 20 %, the repeatability decreases. Through an analysis of the resistance change of the fabric sensor during the movement of parts of the human body, such as elbows, knees, fingers, and the throat, the sensor shows satisfactory performance in monitoring human movement and physical signs.

Poly(p-phenylenetere phthamide) fiber is a high-performance synthetic fiber whose reinforced composites are widely used for their advantages of high strength and lightweight. However, the further potential usage of poly(p-phenylenetere phthamide) and its reinforced composites is limited in areas such as antistatic materials, conducting materials, and electromagnetic shielding materials due to their high electrical insulation. To improve the electrical conductivity, an online polymerization coating technology was used to manufacture conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns continuously. The conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns’ structure and properties such as surface morphology, electrical conductivity, Fourier-transform infrared spectroscopy spectra, thermogravimetric performance, and mechanical properties were studied in details. Then, three kinds of multiaxial composites were prepared by using the conductive poly(p-phenylenetere phthamide)/polyaniline composite yarn as the reinforcement and unsaturated polyester resin as a matrix, and the electromagnetic shielding performance of the composites was measured. The results indicated that the conductivity of conductive poly(p-phenylenetere phthamide)/polyaniline composite yarn can reach to ∼160 S/m. The thermogravimetric performance of poly(p-phenylenetere phthamide) was reduced after conductive treatment. The mechanical properties of the composite yarns, such as the breaking strength and elongation, remained unchanged when the oxidant concentration was lower than 0.6 mol/L and decreased with the increase in the oxidant concentration. The electromagnetic shielding composites show a certain anti-electromagnetic radiation capability, and the shielding effectiveness value increased with the axial number and density of the conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns. For the tetra-axial composite with a conductive yarn density of 37 yarns per inch, the average shielding effectiveness value in the frequency range of 100 MHz to 1500 MHz can exceed 22 dB.