Browsing by Author "Fu, HK"

Now showing 1 - 2 of 2

Enhanced thermal properties of PS nanocomposites formed from montmorillonite treated with a surfactant/cyclodextrin inclusion complex
(2005-01-26)
Yei, DR
;
Kuo, SW
;
Fu, HK
;
Chang, FC
;
應用化學系
We have prepared polystyrene/clay nanocomposites using an emulsion polymerization technique. The nanocomposites were exfoliated at 3 wt% content of pristine clay relative to the amount of polystyrene (PS). We employed two surfactants for the montmorillonite: cetylpyridinium chloride (CPC) and the CPC/alpha-CD inclusion complex. Prior to polymerization, each surfactant intercalates into the layers of the pristine clay dispersed in water. The inclusion complex was characterized by X-ray diffraction, C-13 CP/MAS NMR spectra, and H-1 NMR spectroscopy, and TGA. X-ray powder patterns of the CPC/alpha-CD complex indicate that the alpha-CDs units form channels. The C-13 CP/MAS NMR spectrum of the complex suggests that a CPC chain is included in the channel formed by the alpha-CDs. The H-1 NMR spectra of the complexes indicate that the stoichiometry of the complexes is 1:2 (i.e. one CPC molecule and two alpha-CD units). The TGA reveals that the inclusion complex has higher thermal stability relative to the virgin CPC. We employed both X-ray diffraction (XRD) and transmission electron microscopy (TEM) to characterize the structures of the nanocomposites. The value of T-g of the PS component in the nanocomposite is 6degreesC higher than that of the virgin PS and its thermal decomposition temperature is 33degreesC higher. The CPC/alpha-CD-treated clay is more effective than is virgin CPC-treated clay at enhancing the thermal stability of polystyrene. (C) 2004 Published by Elsevier Ltd.
Synthesis of a novel benzoxazine monomer-intercalated montmorillonite and the curing kinetics of polybenzoxazine/clay hybrid nanocomposites
(2006-01-15)
Yei, DR
;
Fu, HK
;
Chen, WY
;
Chang, FC
;
應用化學系
Polybenzoxazine (PBZ), which has a structure similar to that of phenolic resin, is formed through the thermal self-curing of benzoxazine, that is through a heterocyclic ring opening reaction that requires no catalyst and releases no condensation byproducts. We have used the solvent blending method to prepare PBZ/clay nanocomposites possessing various clay contents. We synthesized a monofunctional benzoxazine monomer (MBM) and then treated the clay with this intercalation agent. The results of X-ray diffraction (XRD) analysis indicated that MBM intercalated into the galleries of the clay; the nanocomposite possessed an exfoliated structure at 3% clay content. To better understand the curing kinetics of the PBZ/clay nanocomposites, we performed dynamic and isothermal differential scanning calorimetry (DSC) measurements. We describe the thermodynamics of the curing process, using all three of the Kissinger, Ozawa, and Kamal models. The Kissinger and Ozawa methods gave fairly close results for the calculated activation energies, which decreased upon increasing the clay content. The Kamal method, based on an autocatalytic model, suggested a total reaction order of between 2.4 and 2.8. The glass transition temperature (T,) decreased upon increasing the clay content. Thermogravimetric analysis (TGA) indicated that the nanocomposites have higher decomposition temperatures than does the pristine PBZ; this finding suggests an enhancement in their thermal stability. (c) 2005 Wiley Periodicals, Inc.