Properties of conductive films filled with stainless steel fiber.

In order to analyze the effects of stainless steel fiber length and filling amount on conductivity and shielding effectiveness (SE) of the conductive films, the stainless steel fiber was uniformly dispersed on the surface paper coated with urea formaldehyde (UF) resins and acrylic resin to prepare conductive films filled by stainless steel fiber with electromagnetic shielding performance by hot pressing. Firstly, stainless steel fiber distributions in the plane and cross-section of conductive films were analyzed by microstructure characterization. And then the conductivity and shielding effectiveness (SE) of the conductive films were investigated by four-electrode method and transmission line method, respectively. Finally, further analysis on shielding mechanism of conductive films filled with stainless steel fiber was conducted according to theoretical simulation. Results revealed that: 1) Random distributions of the stainless steel fiber in the plane and cross-section were improved and an effective “three-dimensional conductive network” was observed to form in the conductive films with the stainless steel fiber filling amount rising. 2) Conductivity and SE of the conductive films were improved with the increase of stainless steel fiber length and filling amount. 3) The filling amount of stainless steel fiber and thickness of conductive films exhibited significant influence on conductivity of the conductive films. 4) When the filling amount of 15 mm long stainless steel fiber increased to 250 g/m2, volume resistivity of the conductive films was reduced to 6.493×10-3 Ω·cm. And the corresponding SE ranged from 37.77 to 51.42 dB, had moderate shielding performance and could meet high requirements of electromagnetic compatibility. 5) Results of the theoretical simulation revealed that absorption loss plays an important role in the SE of conductive films. And the conductive films exhibited excellent wave absorbing property.