不锈钢纤维填充导电膜片的性能研究

为探究不锈钢纤维长度与填充量对导电膜片导电性能与电磁屏蔽性能的影响,将不锈钢纤维均匀地铺撒在涂有脲醛树脂和丙烯酸树脂的表层纸上热压,制备具有电磁屏蔽功能的不锈钢纤维填充导电膜片。首先通过微观结构表征,分析不锈钢纤维在导电膜片平面和断面内的搭接状况;然后采用四电极法与同轴线法测试导电膜片的体积电阻率及电磁屏蔽效能;最后通过理论模拟探究不锈钢纤维填充导电膜片的电磁屏蔽机理。结果表明:1)随着不锈钢纤维填充量的增加,导电膜片平面和断面内不锈钢纤维之间交叉排列的混乱程度不断增加,并以随机排列的形式相互交织形成了有效的“三维导电网络”。2)随着不锈钢纤维长度和填充量的不断增加,导电膜片的体积电阻率逐渐减小,而其电磁屏蔽效能逐渐增大。3)不锈钢纤维的填充量、导电膜片厚度对导电膜片的导电性能影响显著。4)当不锈钢纤维长度为15 mm、填充量为250 g/m2时,导电膜片的体积电阻率降低为6.493×10-3 Ω·cm,电磁屏蔽效能为37.77～51.42 dB,达到中等屏蔽效果,适用于对电磁兼容要求较高的场合。5)理论模拟结果表明,吸收损耗在导电膜片对电磁辐射的屏蔽效果中占有很大的比重,导电膜片表现出了很好的吸波特性。 

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.