Electromagnetic shielding effectiveness of needle-punched composite nonwoven fabrics with stainless steel fibres

In the study, electromagnetic shielding efficiency (EMSE) absorption and reflectivity properties of fabric produced from staple stainless-steel fibres and recycled staple polyester fibres by carding and needling technologies were investigated. The bi-component core/sheath polyester fibres at a fixed ratio of 20% in producing all nonwoven fabrics were used. The staple stainless-steel fibres and recycled staple polyester fibres were blended at 13 different ratios such as 1%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, 27.5%, 30%. The fibre webs were formed at wool type carding machine and then the folded webs were bonded mechanically with needle punching machines. Half of the produced nonwoven composite fabrics were bonded by thermal bonding technology with oven and calender machines. As the conductive fibres were costly, the study aimed to obtain optimum shielding effectiveness with the usage of minimum conductive fibres. Electromagnetic shielding properties, absorption and reflection characteristics of needle-punched nonwoven fabrics with calendered or un-calendered were performed by coaxial transmission line method according to ASTM-D4935-10 in the frequency range of 15 MHz to 3000 MHz. It is a known fact that electromagnetic shielding effectiveness increases with the increase in the amount of conductive fibre. It was found that nonwoven fabric produced with a usage of 17.5% stainless steel fibre has at least 90% electromagnetic shielding percentage in general use with 15 dB at a frequency of 1800 MHz. Increased stainless steel fibre content in nonwoven fabrics resulted in decreased nonwoven fabric thickness and tensile strength. Such a nonwoven composite material with electromagnetic shielding property could be used for construction and building applications.