Abstract
有鑑於橡膠改質環氧樹脂之商業用途極廣泛，而其性質又因組成、硬化過 程等之不同會有許多的變化，本研究的目的即在找出微結構生成的機理， 提供作為控制橡膠改質環氧樹脂之性質的依據。本研究選擇 CTBN 增韌 DGEBA/DICY 系統，作為研究的對象，進行一系列系統性的實驗與分析。 在聚合反應過程中，會生成一種在連續相中有許多球狀第二相顆粒分佈的 微結構，為實地了解相分離的發生過程，吾人首次採用即時光學顯微鏡技 巧，將硬化反應過程中第二相顆粒生成與成長的過程忠實的記錄下來，作 為探討相分離機理的依據。由反應動力學及分子量變化的分析，可以掌握 反應系統的進展（如反應率），並結合化學流變學分析，吾人獲得環氧樹 脂的化學結構（如分子量、黏度）隨硬化反應而變化的細節，且可以透過 理論模型加以預測。在探討發生相分離的微結構變化方面，由理論上反應 系統之熱力學變化分析，可了解不可逆性之硬化反應促使第二相的生成是 可能的，吾人進一步引用兩相間界面能量與環氧樹脂分子量變化之間的關 係，使分析更符合實際狀況。本研究引用了傳統均質系統的核胞理論，結 合前述的實驗與理論分析，證實吾人可以利用「核胞生成與成長」的機理 加以描述相分離程序。吾人發展了一組模型，可用來預測在橡膠改質之熱 固性樹脂聚合反應過程中分散相的凝聚數量與大小，此模型乃是結合 Flory-Huggins 方程式的熱力學關係，與描述硬化反應及核胞成長速率的 基本方程式而得，藉此吾人可以半定量化的解釋與描述第二相自反應性混 合物中產生的相分離過程。在聚合反應初期，反應性混合物處於均質狀態 ；當反應進行到某一特定程度時，會出現半徑達到或大於臨界直徑的富橡 膠相且處於穩定狀態，同時該富橡膠的第二相隨聚合反應的持續進行開始 成長。在聚合反應過程中的兩相形態學變化，是肇因於富環氧樹脂相的基 材分子量的增加，球狀區域的構造因而產生並逐漸被固定。當核胞生成成 為相分離的控制因素時，球狀第二相的核胞產生時間及其成長速率，將直 接受到反應過程的兩相間界面強度、環氧樹脂分子量的增加量、熱力學特 性、及組成梯度的影響。 The phase separation process of rubber-modified epoxy system during curing was described in terms of nucleation-growth mechanism. It was derived from morphological observations that spherical domains were developed during polymerization in a continuous matrix. The morphological changes were recorded in real time by means of optical microscopy. We have applied a model to predict the amount and radius of the dispersed phase that segregated during a thermosetting polymerization. The model was based on a Flory-Huggins equation for thermodynamic description as well as constitutive equations for nucleation and growth rates. Using this model, we could semi- quantitatively interpret and describe the phase separation process of second phase from curing mixture. During the initial polymerization period the mixture remained homogeneous; at a certain reaction extent a thermodynamically stable rubber-rich phase with critical particle's size of critical radius or larger was grown spontaneously. The build-up of molecular weight in the matrix during polymerization resulted in the changing of two-phase morphology and the fixation of the spherical domain structure. Nucleation was the controlling factor of phase separation process. We concluded that the nucleation and growth of spherical second phase was expected to be directly related to the interfacial tension, increasing of molecular weight, thermodynamic properties and composition gradient.