利用奈米石墨薄片與碳黑提升EVA複材抗電磁波干擾能力之研究

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

劉建偉(Jian-Wei Liu)

指導教授 ： 黃繼遠

大同大學/工程學院/材料工程學系所/碩士(2010年)

摘要

本實驗利用膨脹石墨及奈米碳黑雙導電填充材，來提升乙烯醋酸乙烯酯（Ethylene-Vinyl Acetate, EVA）複材之抗電磁干擾能力，針對奈米石墨薄片進行酸洗、摻混煉時的剪力變化、碳黑種類及利用鈦系偶合劑作表面處理，來改善複材抗電磁干擾能力。並利用4點探針、掃描式電子顯微鏡、能量散佈光儀、X光繞射儀、網路分析儀、頻譜儀對複材作相關分析。
體積電阻量測結果，奈米石墨薄片形成導電複材的滲濾值約是40phr，藉由酸洗純化來改善其導電性，提高混煉剪力與超音波震盪來分離奈米石墨薄片，但仍無法有效提升複材之電磁波遮蔽值，因為奈米石墨薄片在複材內部屬於2D結構其結構，無法形成一個連續導電通路所致，所以添加10phr，20phr，30phr的XC-72導電碳黑，或BP-2000超級導電碳黑對其產生石墨薄片之連結，實驗結果得知碳黑種類以BP-2000有較佳的遮蔽值，但因為其表面積過大會造成混煉扭矩過大導致複材難加工。當在XC-72導電碳黑添加20phr即有99.7﹪之入射能量遮蔽。再利用Lica 38鈦系偶合劑對奈米碳黑作表面處理，可降低碳黑顆粒之間的作用力，使混煉扭矩下降約2~3 N.m並保持原有遮蔽值。碳黑的添加可提供一個額外的電子跳躍路徑，藉此來提升複材電磁波遮蔽值，因而遮蔽值從原本8dB提升至40dB。並可達10﹪能量吸收。
雙導電填充材是結合二種以上填充材的優點，使原本EG/EVA複材的2D導電通路藉由添加奈米導電碳黑進而形成3D連續導電通路，藉此大幅提升電磁波遮蔽值。

關鍵字

奈米石墨薄片

並列摘要

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.

並列關鍵字

graphite nanoplatelet

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