Preparation And Investigation On Performance Of The Conductive Aromatic Polyamide Fiber

Aramid fiber is a high-performance organic fiber with a unique combination of excellent mechanical properties, chemical resistance and thermal stability, which was developed for demanding industrial and advanced technology applications. The metallization of aramid fiber is very important because the final products combine the lightweight, high strength and flexibility of fibers with the conductivity of metals, which has great potential in fields of aerospace, healthcare, military and microelectronics. Up to now, several methods have been reported for metallization of fibers, among these methods, electroless plating has proven its advantages over other methods in depositing metal on fibers due to its lower cost, simple devices, ability to form uniform coatings on the surface of fibers, which is very attractive to a large number of scientists. To attain a good adhesion between the metal layer and the surface of fiber, electroless plating of fiber generally requires the modification of the surface, but it is difficult to modify the surface of aramid fiber effectively owing to its chemically inert surface with high crystallinity, which results in poor interfacial adhesion between the fiber matrix and the electroless deposit. Till now, most electroless plating surface-modification pretreatment methods conducted on the aramid fiber have many problems, such as resulting in a sharp reduction in mechanics performance of the fiber and weak adhesive force between the fiber and the plated layer, the utilization of expensive Pd as catalysts, the complicated operation processes during the synthesis and so on. Therefore, to develop a new surface-modification pretreatment method that not only can maintain the mechanical properties of the aramid fiber but also can enhance the interfacial adhesion between the plated layer and the fiber is the difficulty and key point in preparation of conductive aramid fiber with high performance.In order to solve the problems mentioned above, we proposed a novel swelling impregnation pretreatment method for electroless metal deposition on aramid fiber. Etching method is not adopted in this pretreatment process, so the plated fiber maintains the excellent mechanical properties of aramid. Besides, the palladium-free catalyzation pretreatment method is simple and results in a high adhesion strength between the plated layer and the aramid fiber.By swelling impregnation pretreatment method combined with electroless plating technology, we successfully prepared nickel plated aramid(Ni-plated aramid) and copper plated aramid(Cu-plated aramid). Besides, several analysis methods were employed to characterize the conductive aramid fiber: XPS and XRD were used to investigate the form of catalyst precursor existing in fiber surface after swelling impregnation pretreatment; SEM and AFM were employed to investigate the surface morphology of aramid fiber at different fabrication stages; XRD were used to characterize the crystalline structure of Ni-plated aramid and Cu-plated aramid; The chemical composition of the nickel coating and the copper coating were studied by EDS; The cross section of Ni-plated aramid fiber and aramid fiber after swelling impregnation pretreatment were investigated by TEM; The influence of using surfactant SDS during electroless nickel plating on surface morphology, surface roughness and the adhesion of the plated Ni layer to matrix was studied by SEM and AFM; The corrosion resistance of Ni-plated aramid in different corrosive environments were investigated by SEM; Electronic strength tester was employed to study the mechanical properties of aramid fiber at different fabrication stages and the influence of swelling impregnation pretreatment on mechanics performance of aramid; The influence of using 2, 2’-dipyridyl during electroless copper plating on surface morphology, surface roughness, grain size of the copper deposits was investigated by SEM, AFM and XRD.The results revealed:After the swelling impregnation and reduction treatment, the Ag particles formed in the region of fiber surface serve as catalysts for the electroless plating reactions as well as an anchor for the plated layer, the sizes of which range from several nanometers to 20 nm.The coating of Ni-plated aramid fiber is mainly composed of nickel(86.2 wt.%) and phosphorous(12.9 wt.%), and the deposit is typically amorphous. The electric resistance and maximum load of Ni-plated aramid fiber are 1.5 Ω/cm and 40.34 c N, respectively. The introduction of SDS in electroless Ni plating bath can enhance the anchoring strength of the Ni coating and reduce the surface roughness of the coating.The coating of Cu-plated aramid fiber is composed of copper(92.46 wt.%), carbon(5.48 wt.%) and oxygen(2.06 wt.%), and the deposit is crystalline. The electric resistance and maximum load of Cu-plated aramid fiber are 0.5 Ω/cm and 33.6 c N, respectively. The introduction of 2, 2’-dipyridyl in electroless Cu plating bath can reduce the surface roughness and the grain size of the Cu coating.