Development of Conductive Knitted- Fabric-Reinforced Thermoplastic Composites for Electromagnetic Shielding Applications

Abstract

This paper presents a feasibility study to develop conductive knitted-fabric-reinforced thermoplastic composites for electromagnetic shielding applications. Polypropylene is the matrix phase, and glass fibers are the reinforcement phase of the composite material. Stainless steel wires and staple yarns are incorporated as conductive fillers to facilitate the electromagnetic shielding properties of the composite material. Owing to their high stiffness, knitting of glass fibers and stainless steel wires is very difficult. To facilitate the knitting, uncommingled yarns comprising stainless steel wires, glass, and polypropylene fibers are produced using a hollow spindle spinning method. Different kinds of weft knitted fabrics are produced, which are subsequently consolidated into composite materials using a compression molding method. The electromagnetic shielding effectiveness (EMSE) of various knitted composites is measured in the frequency range of 300 kHz to 3 GHz. The variations of EMSE of knitted composites with the fabric structure, stitch density, number of plies, and amount of stainless steel are described. The suitability of the knitted composites developed in this study for electromagnetic shielding applications is also discussed.