Abstract
Polypyrrole (PPy) shows a favorable application in the electromagnetic interference (EMI) shielding due to its good electrical conductivity and outstanding air stability. Conducting PPy films with high conductivity and good adhesion were successfully polymerized on the surface of insulating epoxy resin substrates using chemical polymerization. The factors affecting the properties of PPy films, such as the surface morphology, adhesion between PPy film and substrate, electrical conductivity, EMI shielding effectiveness (SE), were investigated. The adhesion was improved significantly through a three-step surface pretreatment of epoxy resin substrates including removing impurities, roughening, and surface modification with silane coupling agent. An enhancement in the conductivity of PPy films of about one order of magnitude was achieved by adding dopant in FeCl3 solution. The higher the conductivity, the better the shielding effectiveness. Taking sodium p-toluenesulfonate doped PPy film as example, EMI SE was in the practically useful range of about 30 dB over a wide frequency range from 30 MHz to 1500 MHz. The PPy film samples were characterized by scanning electron microscopy (SEM), infrared spectra (IR), X-ray photoelectron spectroscopy (XPS) and the flange coaxial transmission device. The four-point probe method was used to measure conductivity of PPy films.
Highlights
Polypyrrole (PPy) is considered one of the most investigated conducting polymers and is the focus in many studies with various practical applications because of its high conductivity, outstanding air stability and special physical, chemical properties compared with other conducting polymers[1 4]
Most of this research focused on electrochemical polymerization, but the dimension of electrode restricted the area of PPy film[12 15]
The electromagnetic interference shielding effectiveness (SE) is proportional to electrical conductivity according to Schelkunoff theory[16, 17]
Summary
Polypyrrole (PPy) is considered one of the most investigated conducting polymers and is the focus in many studies with various practical applications because of its high conductivity, outstanding air stability and special physical, chemical properties compared with other conducting polymers[1 4]. A three-step pretreatment including removing impurities, roughening and silane coupling agent modification of the surface of insulating epoxy resin substrates was carried out first. PPy film was chemically polymerized on the surface of epoxy resin in FeCl3 oxidant solution.
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