Polyetherimide/Epoxy 熱塑型/熱固型 高分子合金之研究

Abstract

以4-4'-diamino diphenyl sulfone (DDS) 為硬化劑, 硬化PEI/ Epoxy的 熱塑型/熱固型高分子合金時，PEI會在環氧樹脂基材中形成圓形顆粒的分 散相，而成為非均相的PEI/epoxy高分子合金。PEI和環氧樹脂有很好的相 容性並可以溶解在環氧樹脂的預聚合物，但在環氧樹脂硬化時，相容性變 差，而形成相分離。當加入少量促進劑1-cyanoethyl-2-ethyl- 4-methyl-imidazole(CEMI)時，環氧樹脂硬化速率明顯增加，可以得到透 明均相的PEI/Epoxy高分子合金，此乃促進劑的加入使環氧樹脂達凝膠點 的硬化速度增快，PEI線性高分子無法從環氧樹脂網狀結構中擴散出來， 本論文證明了利用硬化反應動力學之觀點可以控制高分子合金的相結構並 印證K. Yamanaka所提出的相分離模型。添加PEI於環氧樹脂中，除了均相 高分子合金之IZOD Impact外，無論是非均相或均相高分子合金皆可以增 加未改質環氧樹脂的破壞韌性，但增韌機構全然不同，均相高分子合金是 增加裂縫尖端的塑性變形區，而非均相高分子合金是因PEI顆粒相造成應 力集中，使環氧樹脂基材形成多重局部切變降伏變形(multiple localized shear yield deformation)而達到增韌的目的。 In the thermoplastic/thermoset polymer alloy of PEI/Epoxy, the content of accelerator in the sytem is able to control the curing rate of the thermoset epoxy. When the curing rate is above a critical level, the thermoplastic PEI resin oringinally dissolved in the pre-cured epoxy monomer is being trapped within the epoxy network and can not diffuse out of the epoxy matrix to form a separate phase, a homogeneous polymer alloy is formed. Inhomegeneous polymer alloy can be formed with PEI separated as spherical particles if the epoxy curing rate is below the critical level. Both types of polymer alloys can improve the epoxy toughness significantly by different toughening mechanisms. The homogeneous polymer alloy fractures by a mechanism similar to the unmodified epoxy except larger crack tip plastic zone during crack initiation. In the phase separated polymer alloy, the PEI particles act as stress concentrators to initiate multiple shear nduced cracks and also function as cracki terminators.