高介電環氧樹脂之研究

Abstract

本論文主要探討如何提高環氧樹脂的介電常數。首先比較不同的極性官能基在環氧樹脂系統中，對介電常數的貢獻。從DEA測量的結果可以知道，帶有-NO2官能基的有機化合物明顯的提高樹脂的介電常數，其次是-CN，這與極性基的偶極矩有關，也就是極性越高的電偶極，當施加一個外加電場時，其極化性(polarizability)越大，所以介電常數越高。光敏電阻法適用於樹脂在耐候實驗中，因為高溫及紫外光造成劣化(degradation)現象會造成樹脂黃變而使透光度有所變化。 本論文亦比較不同硬化劑的樹脂系統中，添加不同分子量及含量的聚乙二醇(polyethylene glycol，PEG)對介電常數的貢獻。結果發現當PEG的分子量越小，電偶極越容易隨著外加電場的方向排列成順向性(orientation)，所以越容易產生極化(polarization)，介電常數越高。PEG的分子量越大分子鏈越長，分子鏈段(molecular segment)上的偶極子(dipole)較難跟著電場的方向去排列，所以介電常數越低。而PEG的含量多寡也會造成樹脂系統極性的大小，因此介電常數也會不同。選用不同硬化劑的樹脂系統，會造成Tg的差異，當Tg小於DEA測試的溫度(40℃)時，系統呈現出rubbery state，分子鏈較柔軟且運動性較好，因此介電常數會提高；而Tg大於40℃的系統，在測試狀態是屬於glassy state，整個樹脂系統變得較堅硬，故會造成介電常數變化不大。輸入電壓的頻率也會影響介電常數的大小，當頻率越低時，分子中的電偶極變得很容易而且快速的能夠跟得上電場的方向去排列，故介電常數會比在高頻時大很多。 本系統添加高分子量的環氧樹脂，由於其交聯密度降低，有助於分子鏈段的運動，而會顯現較高的介電常數。本研究亦使用環己胺及苯胺聚合高分子量樹脂，並得到較高的介電常數。

The study focused on the dielectric properties of epoxy resin. The NO2 group shows significant effect on increasing the dielectric constant of the system, and the C≡N group also has similar effect for the polarity of these functional groups. The photoresistor method is used to measure the degradation of the system. The yellowing of the system is caused by the high test temperature or the exposure under the UV light. The study also reports the effect of different curing agent, molecular weight and quantity of PEG modifier on the dielectric properties. The lower molecular weight PEG has higher orientation under the electric field for the polar chain end and high chain mobility, thus shows a higher dielectric constant. The increase of the PEG content also shows a higher polarity and dielectric constant of the system. In addition, the Tg of the system also imparts the increment of the dielectric constant When the Tg is lower than the test temperature, (40℃) the system is at rubbery state and shows a higher dielectric constant. On the contrast, the dielectric constant increment is limited for the higher Tg system. The lower frequency of electric field obtains a higher dielectric constant data for the fully orientation of the molecular chain. The high molecular weight of epoxy resin shows lower crosslinking density and higher dielectric constant. This study uses cyclohexylamine and aniline to synthesize higher molecular weight epoxy and obtains a higher dielectric constant system.