聚丙烯結合碳纖維複合材料超臨界微細發泡射出成型之纖維配向對成型品導電度與拉伸強度之影響

至今對塑膠之需求已不止於使用便利，還須兼具高機械強度、高功能性與優良之品質，因此高分子複合材料因應而生，其纖維分佈與配向將決定品質與性能，因此控制纖維分佈與配向係最為關鍵之要點。本研究分為三部分，第一部分係以同為20wt%與30wt%之PP/CF與PP-g-MA/CF，以三種不同參數：射速、模溫與料溫進行實驗。第二部分導入超臨界微細發泡成型，固定減重比20wt%，新增氣體含量參數進行實驗，探討參數與基材對纖維配向、穿透導電度與拉伸強度之影響。最後探討傳統成型與超臨界微細發泡成型之差異與改善程度。結果顯示傳統成型於高射速下，纖維配向高，拉伸強度強，但穿透導電度低，高模溫與高料溫，表皮層纖維配向高，拉伸強度與穿透導電度皆提高。超臨界微細發泡成型於高射速下，纖維配向高，拉伸強度強，但穿透導電度低，而模溫與料溫則於50°C和220°C時，有最佳拉伸強度與穿透導電度，若溫度提升，氣泡形成通孔破壞結構與阻隔纖維，造成強度與導電度下降。氣體含量上升有助於纖維配向改善，但於0.3wt%易出現單一大型氣泡，而0.7wt%時易形成大型通孔，兩種情況皆不利於拉伸強度與穿透導電度。PP-g-MA/CF有較良好之拉伸性質，但導電性較PP/CF差。超臨界微細發泡成型與傳統成型，前者其纖維配向約下降20%~25%，穿透導電度因而提升3~9倍之多，拉伸強度則下降23%~36。參數對於實驗結果之影響，射出速度於傳統成型影響較為顯著，超臨界微細發泡成型，則關乎泡體成長，因此模溫與料溫影響實驗結果較為顯著。

關鍵字

碳纖維；超臨界微細發泡射出成型；纖維配向；拉伸強度；穿透導電度

並列摘要

Nowadays, the requirement for plastics has not only been facilitated, but also required high mechanical strength, various functions and excellent quality. Therefore, polymer composite was created. If conductive fillers are added, "conductive polymer composites " can be obtained. The distribution and orientation of the fibers will affect the quality and performance of the product. So, controlling the distribution and orientation of the fibers is the key point. This study had be divided into three parts. The first part, experiments had been conducted with three different parameters: injection speed, mold temperature, and melt temperature. The materails used had been PP/CF 20 wt% and 30 wt% and PP-g-MA/CF 20 wt% and 30 wt% in order to study the effect of parameters and materials on fiber orientation, conductivity and tensile strength. The second part had used microcellular injection molding. Experiments had been conducted with four different parameters: injection speed, mold temperature, melt temperature, and N2 content also study the effect of parameters and materials on fiber orientation, conductivity and tensile strength. The last part, we had combined the first part and the second part in order to discuss the difference and improvement between traditional injection molding and microcellular injection molding. The results had shown that the traditional injection molding at high injection speed had has high fiber orientation, strong tensile strength, and low conductivity. At high mold temperature and high melt temperature the fiber orientation in skin layer had been increased, but core layer had been decreased. Both tensile strength and conductivity had been better. The results of microcellular injection molding had shown that at high injection speed, fiber orientation had been higher, and tensile strength had been stronger, but conductivity had been decreased. When the mold temperature had been 50°C and the material temperature had been 220°C, there are the best tensile strength and conductivity. If the temperature had risen again, the bubbles would have been form through-holes, which could have damaged the structure and isolate fibers, resulting in a decrease in tensile strength and conductivity. The increase in the content of the Nitrogen content had contributed to the improvement of the fiber alignment, but a single large bubble had been likely to form at 0.3 wt%, and a large through hole had been easily formed at 0.7 wt%. Both cases had been not conducive to tensile strength and penetration conductivity, so 0.5 wt% had been the best parameter. PP-g-MA/CF had had better tensile strength than PP/CF, but its conductivity had been worse than that of PP/CF, and the fiber orientation of both had been similar. At last, the comparison between microcellular injection molding and traditional injection molding shows that the former had had a 20%~25% decrease in fiber orientation, a 3 to 9 times increase in conductivity, and a 23% to 36% decrease in tensile strength. The influence of the parameters on the overall experimental results, the injection speed had been more significant in the traditional molding, and the supercritical micro-foaming molding had been related to the growth of the bubble body, so the experimental results of the influence of the mold temperature and the material temperature had been more significant.