| Summary: | 博士 === 國立成功大學 === 化學工程學系碩博士班 === 90 === The morphology and the curing behavior of a diglycidylether of bisphenol-A (DGEBA) epoxy which was cured with 4,4'-diamino diphenylsulfone (DDS) and its blends with poly(4-vinylphenol) (PVPh) of various compositions were mainly studied using a differential scanning calorimeter (DSC). Miscibility according to criterion of a single glass transition temperature in the complete composition has been demonstrated in the cured epoxy/PVPh blends. In addition, the morphology of these blends was examined using a scanning electron microscope (SEM) and a homogeneous single-phase DDS-cured PVPh/epoxy network has been observed in the blends of the complete compositions. These results were mainly dependent on the chemical reactions between epoxy and PVPh. By using Fourier-transform infrared spectroscopy (FT-IR) and 13C nuclear magnetic resonance (NMR) techniques, mechanisms of reactions leading to a homogeneous network between the DGEBA epoxy resin and PVPh polymer have been proven using model compounds. Because the para-alkyl group in the aromatic of PVPh belongs to the electron-donating group (EDG), it would ionize the phenyl-hydroxyl group to form the phenoxide ion to attack the epoxide ring of DGEBA at high temperatures. Therefore, at elevated temperatures, the epoxy/PVPh mixture developed a network-like homogeneous solid, which was a result of reactions between the epoxide of DGEBA epoxy and phenyl-hydroxyl of the linear PVPh polymer. In addition, the addition of PVPh into DDS amine-cured epoxy significantly affected curing reaction of the DGEBA/PVPh/DDS blend. The cure reaction rates for the epoxy blends with PVPh were higher than that of DDS-cured neat epoxy. However, an autocatalytic kinetic mechanism could be found for the curing behavior of DDS-cured epoxy/PVPh blends, which remained independent of the addition of PVPh.
The other part of this study was to investigate poly(ethylene oxide) (PEO) growth kinetics and morphology as influenced by the state of cure in a crosslinking system. PEO was miscible with a crosslinking epoxy system (DGEBA/DDS) (in the amorphous domains) before and after cure. Thermal analysis, growth kinetics analysis, morphology characterization and the intermolecular interaction were performed and the results are in good agreement. The morphology and growth kinetics of the PEO crystals was in turn affected by the contents and chemical structures (functional group, molecular weight, crosslink, etc.) and the entrapment of the amorphous diluents (ie., epoxy/DDS). Owing to the effect of the entrapment of the amorphous phase, PEO spherulites presented a feather-like morphology. The hydrogen bonding interaction was more significant before cure due to the interactions between the ether group of PEO and the amine group of DDS. The interaction between PEO and epoxy/DDS become less in the cured network. Therefore, the hydrogen bonding interactions in DGEBA/PEO/DDS mixtures before and after cure have significant influence on the morphology and growth kinetics of the PEO crystals.
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