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Item type:Item, Transesterification in homogeneous poly(epsilon-caprolactone)-epoxy blends(1999-01-03) ;Chen, JL ;Huang, HM ;Li, MS ;Chang, FC應用化學系Transesterification has been investigated in poly(epsilon-caprolactone) (PCL)-epoxy blends. In the hot melt process, the hydroxyl on diglycidyl ether of bisphenol-il (DGEBA) monomers is too low to give a noticeable transesterification reaction. In the postcure process, model reactions reveal that the hydroxyls from a ring-opening reaction are able to react with the esters of PCL. In the meantime, the PCL molecular weight decrease and its distribution becomes broader. Nuclear magnetic resonance spectra reveal that fraction of the tertiary hydroxyls converts to secondary hydroxyls. In the cured DGEBA-3,3'-dimethylmethylene-di(cyclohexylamine)-PCL blend, a homogeneous morphology is achieved. PCL segments are grafted onto the epoxy network after postcuring and result in the lower T-g observed in the differential scanning calorimetry thermogram. A higher transesterification extent also results in broader transition peaks by dynamic mechanical analysis. (C) 1999 John Wiley & Sons, Inc.Item type:Item, Temperature-dependent phase behavior in poly(epsilon-caprolactone)-epoxy blends(2001-03-01) ;Chen, JL ;Chang, FC ;應用化學系Department of Applied ChemistryThe cured morphologies of poly(epsilon -caprolactone)/epoxy (PCL/epoxy) blends are examined by SEM micrographs. The phase separation mechanism of the blend can be deduced from cured morphologies influenced by the blend compositions and curing conditions. The LCST phase diagram is proposed for the system and the location of the critical point shifts with the curing temperature, which results in the change of phase separation mechanism. The curing rate promoted by higher curing temperature also influences the morphologies of the blends. The fraction of the epoxy-rich macrophase resulted from the long-distance diffusion decreases with the increase of the curing temperature. In contrast, the domain size of the epoxy microphase increases with the curing temperature, which cannot be dominated by the epoxy curing rate. (C) 2000 Elsevier Science Ltd. All rights reserved.Item type:Item, Phase separation and melting behavior in poly(epsilon-caprolactone)-epoxy blends cured by 3,3'-dimethylmethylene-di(cyclohexylamine)(2003-09-12) ;Chen, JL ;Chang, FC ;應用化學系Department of Applied ChemistryThe morphology and the melting behavior of poly(E-caprolactone)/epoxy blends (PCL/epoxy) have been investigated by SEM and DSC. The mechanism of phase separation varies with the curing temperature and PCL content, which can be deduced from the cured morphology of the blend. Higher temperature leads to lower blend viscosity and a higher curing rate, and the final morphology is determined by the competition of these two factors. The PCL melting behavior of the blend is influenced by the extent of phase separation and crystallization during curing. The dual melting behavior of the PCL blend can be ascribed to the interference of the epoxy, which results in the formation of less perfect PCL crystallites melted at lower temperature. (C) 2003 Wiley Periodicals, Inc.