Thermosetting polymer composites for EMI shielding applications

Efforts have been made towards developing lightweight EMI shielding thermosetting composites materials using room temperature curing epoxy novalac cyclo aliphatic amine hardener system. Average Shielding efficiency (SE) values (100 KHz to 1 GHz) of above 50 dB have been obtained for Carbon Fibre Reinforced Polymeric (CFRP) composite laminates, with variants of glass fabric and aluminium mesh included along with. Sandwich constructions were also fabricated using syntactic foams as the core materials while the skins were designed as combinations of carbon, glass and aluminium. SE values of such constructions made out of conducting skins and both insulating as well as conducting cores were measured over the same frequency range (100 KHZ to 1 GHz). Carbon skin sandwiches have resulted in an average SE of 40-45 dB or above depending upon the nature of the core, whereas, alumesh/ GFRP skin sandwiches have measured an average SE of well over 60 dB. The viscoelastic properties of these composites were also evaluated by Dynamic Mechanical Analysis (DMA) in order to assess their mechanical properties as well as to determine their maximum use temperatures.