A study on the effect of construction parameters of metallic wire/core spun yarn based knitted fabrics on electromagnetic shielding

Metallic wire based single jersey knitted fabrics were produced in different construction to study the electromagnetic shielding characteristics. In one construction, bare silver coated copper wire along with cotton yarn was used to knit fabric by ‘plating’ technique. In another construction, core spun metallic wire yarn produced by ring spinning was used to knit fabrics in two different loop lengths. Scattering ( S) parameters for reflection ( S ₁₁ ) and transmission ( S ₂₁ ) obtained for the fabrics by ASTM D4935 standard using coaxial transmission fixture and network analyser were analysed in the frequency range of 30–1500 MHz. All fabrics exhibited shielding effectiveness of 40 dB and above in low frequency region, the minimum mark for safer application to solve electromagnetic interferences. Fabric produced by ‘plating’ technique showed better electromagnetic shielding than core spun yarn knitted fabrics whereas no marked difference in shielding was noticed between the core spun yarn fabrics produced in two different loop lengths. However, fabric with smaller loop length showed a marginal increase in shielding at low frequency. Core spun yarn knitted fabrics show resonance peaks of reflection at different frequencies which suggest the possibility of tailoring frequency selective surfaces for high pass/no pass filtering. Antibacterial activity of the fabrics as per AATCC 100 test method was moderate with 60–63% bacterial reduction against the bacterium Escherichia coli.