Investigation of Enhanced EMI Shielding Effectiveness in a Hybrid Graphite nanoplatelet-Carbon Black Filled EVA Composites

• Main Authors: Jian-Wei Liu, 劉建偉
• Other Authors: none
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/08091565085703374373

碩士 === 大同大學 === 材料工程學系(所) === 98 === In this study, the expanded graphite and nano carbon black hybrid fillers method was applied to enhance the Electron Magnetic Interference Shielding Effectiveness (EMI SE) for EVA (ethylene–vinyl acetate) composites. Using acid to purify graphite nanoplatelets (GNP)、changing shear rate at blending 、ultrasound treatment、different type carbon black and titanate coupling agent for surface modification improve the EMI SE of composites. Analyzed by 4-point-probe method, SEM, EDS, VNA and EMI measurement, respectively. The percolation threshold value of the conducting composites was about 40 phr of GNPs. Using acid treatment to purify GNP increasing the conductivity and changing shear rate at blending、using ultrasound treatment to separate GNPs but composites still show a poor EMI SE. that was ascribed to GNP is 2D structure can not form a continues conductive network in composites. So we add 10phr, 20phr, 30phr XC-72 or BP-2000 highly conductive carbon black to bridge GNPs. a result of experiment BP-2000 has better EMI SE but the large surface area cause compounding process was hard to proceed. Adding 20phr XC-72 into 40phr GNPs/EVA at compounding composites show 99.7% of the power of the incident wave was shielded. then use Lica 38 titanate coupling agent for surface modification. It may reduce the interforce between carbon black make the torque value decreasing about 2 N.m also maintain the EMI SE. Adding carbon black was provided additional channels for the electron jump in the polymer matrix. Enhancing the EMI SE from 8 to 40 dB and 10% of the power of the incident wave was absorbed by the composite. Hybrid fillers method combined advantage of two fillers; making 2D conductive network of EG/EVA composites were formed 3D conductive network by adding carbon black. Increasing EMI SE largely.