ABS/石墨奈米複合材料之電性質和機械性質的探討

Electrical and Mechanical Property of ABS/graphite Nanocomposites

鄭鈞晏(CHENG CHUN YEN)

指導教授 ： 葉樹開

國立臺北科技大學/工程學院/化學工程研究所/碩士(2012年)

摘要

高分子材料在工程方面應用很廣，而高分子奈米複合材料其性質會因為添加物的不同而有更多的應用價值，例如:添加奈米層狀石墨因為其價格便宜，所以常被用來增加其基材本身的導電性質，由於高分子本身是絕緣體，加入導電填充料之後可讓高分子由絕緣體變成半導體，可應用於電磁遮蔽。除了電性之外，擁有高長寬比的填充料可增加高分子材料的機械性值。
本實驗目的想探討不同的加工方法對於複合材料其電性和機械性質的影響，所以將分為二個部分進行探討，第一部分為固態材料，第二部分為發泡材料。在固態材料部份使用不同長寬比的石墨利用溶液混合法和熔融混煉法加入高分子基材內，製備出高分子導電複合材料，在溶液混合法方面，由於石墨粒徑很小，石墨分子間常會因凡得瓦力的吸引產生聚集現象，所以石墨先以超音波分散後在與高分子進行混合。在熔融混煉法方面，則是利用預混方式來增加其分散性，並且將押出材料直接浸入冰水冷卻以避免降解。製備出的導電複合材料再經由熱壓成型探討其表面電阻率，再由射出成型探討拉伸性質。由溶液混合法的結果來看，長寬比較大的石墨在基材裡接觸的機會較高，其滲流閥值較低，但是熔融混合法的結果發現，兩種不同長寬比的石墨其滲流閥值相同，這是因為石墨的長寬比被破壞的關係，這點可由SEM觀察到，最後結果顯示出在溶液混合法所製備出的導電複合材料其電性最好，其percolation threshold最高可達3wt%。為了預測被剪切應力破壞的石墨長寬比，我們利用滲流閥值模型來預測，並用Halpin-Tsai方程式來進行模擬，發現在1wt%可準確預測材料的電性與力學性質之關連性，但是在3wt%和5wt%時因為石墨團聚和被破壞的關係，導致理論值和實驗值之間有差距。在導電發泡材料方面，我們發現，當泡材的密度越大，其電性越好，percolation threshold從14wt%提升到10wt%，而泡材密度為0.9時，雖然percolation threshold與固態材料一樣，但10wt%到12wt%的表面電阻率從3.7x1013降到3.1x108，比起固態材料表面電阻從3.8x1013降到1x1010的下降幅度還大，表示其電性有更好的現象。

關鍵字

丙烯睛-丁二烯-苯乙烯 ； 高分子導電複合材料 ； 表面電阻率 ； 奈米層狀石墨

並列摘要

Polymeric materials are used in many fields. Polymer nanocomposites can have more applications by adding different types of nanoparticles to the polymer matrix. For example, nanographite platelets(NGP) are common materials that are added to polymer matrices to increase the electrical conductivity of composites due to their lower price. Adding conductive fillers into a matrix can change a polymer from an insulator into a semiconductor. These conductive polymer composites can be used in electromagnetic interference applications. As well as the conductive properties, the mechanical properties of the composites can also be increased due to the rigidity of nanoparticles.
This article focuses on the different processes that could affect the electrical and mechanical property of materials. Two different issues were studied, one is solid material, while the other one is foamed material. In the case of solid material, compounding ABS with nanographites of different aspect ratios by solvent blending and by melt compounding to fabricate polymer conductive composites. In the case of solvent blending, due to the small size of NGP, the Van Der Waals force can make the graphite aggregated. Before blending, ultra-sonication was used. In the case of melt compounding, we pre-mixed the graphite powder with ABS particles before feeding it into the extruder. The compounded samples were either compression molded for electrical conductivity testing or injection molded for mechanical properties testing. In the case of solvent blending, since the aspect ratio of the nanographite can be maintained, the percolation threshold will be lower than samples made by compounding. Percolation threshold can be as low as3wt%. To predict the aspect ratio of graphite after compounding, the percolation model and the Halpin-Tasi equation were applied. It is found that the dispersion and aspect ratio of the filler in the polymer matrix are the important factors that decide the fitting result between the experimental modulus data and theoretical predictions using Halpin-Tsai equations.
In the case of foam materials, we find that the electrical properties increase with the foam density, percolation threshold rise from 14wt% to 10wt%. For the foam materials,surface resistivity dropped from 3.7x1013 to 3.1x108 with the concentration from 10wt% to 12wt%.

並列關鍵字

Acrylonitrile Butadiene Styrene ； Polymer Conductive Composite ； Surface Resistivity ； Nano-Graphite Platelets

參考文獻

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