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Now showing 1 - 10 of 12

Synthesis and characterization of novel segmented polyurethane clay nanocomposite via poly(epsilon-caprolactone)/clay
(1999-07-01)
Chen, TK
;
Tien, YI
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A novel segmented polyurethane/clay (PU/clay) nanocomposite based on poly(caprolactone), diphenylmethane diisocyanate, butanediol, and poly(caprolactone)/ clay prepolymer was synthesized as evidenced by FTIR and X-ray diffraction studies. Poly(caprolactone)/clay (PCL/clay) prepolymer was first synthesized in a nanocomposite form as confirmed by X-ray diffraction. X-ray diffraction study showed that PU/clay contained crystalline structure due to the presence of PCL/clay. In mechanical properties, about 1.4% PCL/clay in PU/clay resulted in a large increase in the elongation of PU/clay. However, when the amount of PCL/clay was 4.2%, the elongation of PU/clay was reduced drastically. This behavior indicated that PU/clay can be transformed from an elastomer to a thermoplastic material as the amount of PCL/clay in PU/clay increased. Additionally, the lap shear stress of PU/clay was at least three times that of neat PU as a result of the PCL/clay component. (C) 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2225-2233, 1999.
Mechanical properties of clay-polyimide (BTDA-ODA) nanocomposites via ODA-modified organoclay
(2000-11-15)
Tyan, HL
;
Wei, KH
;
Hsieh, TE
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Clay-polyimide [3,3', 4,4'-benzophenone tetracarboxylic dianhydride-4,4'-oxydianiline (BTDA-ODA)] nanocomposites were synthesized from ODA-modified montmorillonite (organoclay) and poly(amic acid). The layered silicates of organoclay were intercalated by polyimide (BTDA-ODA), as confirmed by X-ray diffraction and by transmission electron microscopy, and the tensile mechanical properties of the nanocomposites were measured. It was found that the modulus and the maximum stress of these organoclay/BTDA-ODA nanocomposites were much higher than those of pure BTDA-ODA: a twofold increase in the modulus and a one-half-fold increase in the maximum stress in the case of 7/93 organoclay-BTDA-ODA. In addition, the elongation-for-break of organoclay/BTDA-ODA nanocomposites is even slightly higher than that of pure BTDA-ODA, which is a sharp contrast to that of conventional inorganics-filled polymer composites. (C) 2000 John Wiley & Sons, Inc.
Interaction mechanism of a novel polymer electrolyte composed of poly(acrylonitrile), lithium triflate, and mineral clay
(2001-10-15)
Chen, HW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The addition of optimum cetyl pyridium chloride (CPC)-modified montmorillonite (CM) increases the ionic conductivity of poly(acrylonitrile)-based electrolytes by roughly two orders of magnitude. Specific interactions between the silicate layer, the nitrile group, and the lithium cation were investigated by FTIR, solid-state NMR, dielectric analyzer, and alternating current impedance. IR and NMR spectra confirm that the negative charges in the silicate layers alter the ionic charge environment of the PAN-based electrolyte composites, which have the same function as the polar group in PAN. The optimum CM content to achieve the maximum ionic conductivity is 6 phr. However, untreated montmorillonite leads to insignificant polymer intercalation, the negative charges in the silicate layers fail to appreciably disturb the attractive force of the lithium salt, and the resulting conductivity improvement is also less than that of the CM additives. (C) 2001 John Wiley & Sons, Inc.
The novel polymer electrolyte nanocomposite composed of poly(ethylene oxide), lithium triflate and mineral clay
(2001-11-01)
Chen, HW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
This work has demonstrated that the addition of optimum content of D-2000 modified montmorillonite enhances the ionic conductivity of the poly(ethyl oxide) (PEO) based electrolyte by nearly sixteen times more than the plain system. Specific interactions among silicate layer, ethyl oxide and lithium cation have been investigated using alternating current impedance (A.C, impedance), differential scanning calorimetry (DSC) and Fourier- transform infrared (FT-IR). The DSC characterization confirms that the initial addition of clay is able to enhance the PEO crystallinity due to the interaction between the negative charge from the clay and the lithium cation. Three types of complexes are present; complex I is present in the PEO phase, complex II resides at the interphase, and complex III is located within the clay domain. Complex 11 plays the key role in stabilizing these two microstructure phases. FT-IR spectra confirm that the existence of clay is able to dissolve the lithium salts, easier than the plain electrolyte system and thus increases the fraction of free ions. (C) 2001 Published by Elsevier Science Ltd.
Preparation and crystallization behavior of syndiotactic polystyrene-clay nanocomposites
(2001-12-01)
Tseng, CR
;
Wu, JY
;
Lee, HY
;
Chang, FC
;
應用化學系
Syndiotactic polystyrene/modified-clay nanocomposites have been prepared by solution blending by mixing pure s-PS and organophilic clay with adsorbed cetyl pyridium chloride (CPC) in dichlorobenzene. The dispersability of the clay in syndiotactic polystyrene/modified-clay nanocomposites was studied using X-ray and transmission electron microscopy. The clay is well dispersed into the s-PS matrix using solution blending with scale in 1-2 nm or in a few tenths similar to 100 nm depending on surfactant treatment. The CPC is partially compatible with s-PS and allows syndiotactic polystyrene chains intercalating into clay layers. The crystallization behavior of alpha- and beta -crystals for syndiotactic polystyrene nanocomposite has been thoroughly examined using the Fourier transform infrared and differential scanning calorimetry. Our results further demonstrate that the presence of the clay plays a vital role in facilitating the formation on the thermodynamically more favorable beta form crystal when the s-PS is melt- or cold-crystallized. (C) 2001 Elsevier Science Ltd. All rights reserved.
Conductivity enhancement mechanism of the poly(ethylene oxide)/modified-clay-LiClO4 systems
(2002-07-01)
Chen, HW
;
Chiu, CY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
This study demonstrates that adding clay that was organically modified by dimethyldioctadecylammonium chloride (DDAC) and d2000 surfactants increases the ionic conductivity of polymeric electrolyte. A.C. impedance, differential scanning calorimetric (DSC), and Fourier transform infrared (FTIR) studies revealed that the silicate layers strongly interact with the dopant salt lithium perchlorate (LiClO4) within a poly(ethylene oxide) (PEO)/clay/LiClO4 system. DSC characterization verified that the addition of a small amount of the organic clay reduces the glass-transition temperature of PEO as a result of the interaction between the negative charge in the clay and the lithium cation. Additionally, the strength of such a specific interaction depends on the extent of PEO intercalation. With respect to the interaction between the silicate layer and the lithium cation, three types of complexes are assumed. In complex I, lithium cation is distributed within the PEO phase. In complex II, lithium cation resides in an PEO/exfoliated-clay environment. In complex III, the lithium cation is located in PEO/ agglomerated-clay domains. More clay favors complex III over complexes II and I, reducing the interaction between the silicate layers and the lithium cations because of strong self-aggregation among the silicate layers. Notably, the (PEO)(8)LiClO4/DDACmodified clay (DDAC-mClay) composition can form a nanocomposite electrolyte with high ionic conductivity (8 x 10(-5) S/cm) at room temperature. (C) 2002 Wiley Periodicals, Inc.
Preparation and characterization of polystyrene-clay nanocomposites by free-radical polymerization
(2002-08-15)
Tseng, CR
;
Wu, JY
;
Lee, HY
;
Chang, FC
;
應用化學系
The polymerizable cationic surfactant, vinylbenzyldimethylethanolammouium chloride (VBDEAC), was synthesized to functionalize montmorillonite (MMT) clay and used to prepare exfoliated polystyrene-clay nanocomposites. The organophilic MMT was prepared by Na(+) exchanged montmorillonite and ammonium cations of the VBDEAC in an aqueous medium. Polystyrene-clay nanocomposites were prepared by free-radical polymerization of the styrene containing intercalated organophilic MMT. Dispersion of the intercalated montmorillonite in the polystyrene matrix determined by X-ray diffraction reveals that the basal spacing is higher than 17.6 nm. These nanocomposites were characterized by differential scanning calorimetry (DSC), transmission electron micrograph (TEM), thermal gravimetric analysis (TGA), and mechanical properties. The exfoliated nanocomposites have higher thermal stability and better mechanical properties than the pure polystyrene. (C) 2002 Wiley Periodicals, Inc.
Crystallization behavior of syndiotactic polystyrene nanocomposites for melt- and cold-crystallizations
(2002-12-05)
Tseng, CR
;
Wu, SC
;
Wu, JJ
;
Chang, FC
;
應用化學系
Analyses of the effects of montmorillonite (clay) on the crystallinity and crystallization behavior of syndiotactic polystyrene (s-PS) were investigated by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The dispersibility of the clay in s-PS nanocomposites was studied by X-ray and transmission electron microscopy (TEM). The clay was dispersed into the s-PS matrix by melt blending on a scale of 1-2 nm or few tenths-100 nm, depending on the surfactant treatment. On adding clay, the crystallization behavior of the s-PS tends to convert into the beta-crystal from the alpha-crystal after being cold-crystallized because the clay plays a vital role in facilitating the formation of the thermodynamically favored beta-form crystal when the s-PS is cold- or melt-crystallized. This phenomenon leads to a change in a conventional mechanism of molecular packing for the s-PS. Evidently, the clay significantly affects the crystallinity and crystallization behavior of the s-PS. (C) 2002 Wiley Periodicals, Inc.
Syntheses and characterizations of in situ blended metallocence polyethylene/clay nanocomposites
(2003-12-01)
Kuo, SW
;
Huang, WJ
;
Huang, SB
;
Kao, HC
;
Chang, FC
In this paper, we report the preparation of in situ blends of metallocence polyethylene (mPE) with montmorillonite (clay). The polymerization activity of polyethylene decreases upon increasing the amount of the clay feed. The mPE nanocomposites still possess their original melting and crystallization temperatures, but the melting and crystallization enthalpies decrease upon increasing the clay content. In addition, the polymer interaction parameter between mPE and exfoliated clay sheets was calculated to be -0.204 based on a modified Kim-Bae equilibrium melting depression equation. All of the isothermal crystallization kinetics data fit well to the Avrami crystallization equation. We found that increasing the clay content results in a faster rate of crystallization, but pure mPE still crystallizes the fastest. Using a small amount of pretreated clay results in a more homogeneous and finer dispersion of the clay in the polymer matrix, as determined by wide-angle X-ray diffraction and transmission electron microscopy analyses. Both the values of T-1rho(H) in the solid-state NMR spectra of the fast and slow components show increment upon increasing the clay content, which indicates that either the mobile phase tends to increase its rigidity in the clay-containing system. (C) 2003 Elsevier Ltd. All rights reserved.
Properties of covalently bonded layered-silicate/polystyrene nanocomposites synthesized via atom transfer radical polymerization
(2005-02-01)
Li, CP
;
Huang, CM
;
Hsieh, MT
;
Wei, KH
;
材料科學與工程學系
Covalently bonded layered silicated/polystyrene nanocomposites were synthesized via atom transfer radical polymerization in the presence of initiator-modified layered silicate. The resulting nanocomposites had an intercalated and partially exfoliated structure, as confirmed by X-ray diffraction and transmission electron microscopy. The thermal properties of the nanocomposites improved substantially over those of neat polystyrene. In particular, a maximum increase of 35.5 degreesC in the degradation temperature was displayed by these nanocomposites. Additionally, the surface elastic modulus and hardness of these nanocomposites were more than double those of pure polystyrene. (C) 2004 Wiley Periodicals, Inc.

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