Browsing by Author "Tseng, CR"

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Chain conformation and crystallization behavior of the syndiotactic polystyrene nanocomposites studied using Fourier transform infrared analysis
(2001-04-24)
Wu, HD
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Tseng, CR
;
Chang, FC
;
應用化學系
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Department of Applied Chemistry
Analyses of the effects of montmorillonite (clay) on the chain conformation and crystallization of syndiotactic polystyrene (s-PS) thin films are investigated using FTIR spectroscopy, X-ray diffraction, and TEM. The clay is dispersed into the s-PS matrix using a solution blending with scale in 1-2 nm or in a few tenths to 100 nm, depending on whether a surfactant is added or not. Upon adding clay, the chain conformation of s-PS tends to convert to TTTT from rTTGG after drying because the highly dispersed clay overcomes the energy barrier of chain conformation transformation. This phenomenon leads to a change in a conventional mechanism of molecular packing for s-PS in the drying stage. During melt-crystallization, clay plays a vital role in facilitating the formation of the thermodynamically favored all-trans p form crystal, particularly on the s-PS thin film. When the s-PS is melt-crystallized at a cooling rate of 1 degreesC/min from 320 degreesC, the highest absolute crystallinity of beta form up to 0.56 occurs in the clay dispersibility of few tenths to 100 nm in the s-PS matrix; then dispersibility is of 1-2 nm (0.49), and the final one is of pure s-PS (0.42). Evidently, clay significantly affects the chain conformation and crystallization of s-PS.
Crystallization behavior of syndiotactic polystyrene nanocomposites for melt- and cold-crystallizations
(2002-12-05)
Tseng, CR
;
Wu, SC
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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.
Crystallization kinetics and crystallization behavior of syndiotactic polystyrene/clay nanocomposites
(2001-09-01)
Tseng, CR
;
Lee, HY
;
Chang, FC
;
應用化學系
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Department of Applied Chemistry
We investigated the effects of montmorillonite (clay) on the crystallization kinetics of syndiotactic polystyrene (sPS) with isothermal differential scanning calorimetry analyses. The clay was dispersed into the sPS matrix via melt blending on a scale of 1-2 nm or up to about 100 nih, depending on the surfactant treatment. For a crystallization temperature of 240 degreesC, the isothermal crystallization data were fitted well with the Avrami crystallization equation. Crystallization data on the kinetic parameters (i.e., the crystallization rate constant, Avrami exponent, clay content, and clay/surfactant cation-exchange ratio), were also investigated. Experimental results indicated that the crystallization rate constant of the sPS nanocomposite increased with increasing clay content. The clay played a vital role in facilitating the formation on the thermodynamically more favorable all-beta -form crystal when the sPS was melt-crystallized. (C) 2001 John Wiley & Sons, Inc.
Poly(oxypropylene)-amide grafted polypropylene as novel compatibilizer for PP and PA6 blends
(2001-01-01)
Tseng, FP
;
Lin, JJ
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Tseng, CR
;
Chang, FC
;
應用化學系
Poly(oxypropylene)-amide grafted polypropylene (PP) was prepared in an extruder by the reaction of poly(oxypropylene) (POP)diamines and maleated PP (PP-g-MA). The resulting POP-grafted PP copolymers are confirmed by the FTIR analysis, and used as compatibilizers for polyamide 6 (PA6) and polypropylene blends, These compatibilizers, POP-functionalized PPs (PP-g-MA-co-POPs), have different amphiphilic properties depending on the content of MA in the starting PP-g-MA and the molar ratio of MA/amine. The compatibilization effect is examined in terms of morphologies, thermal and mechanical properties. The morphologies, affected by the molecular weight of POP diamine in PP-g-MA-co-POP copolymer, show a decreasing size of the dispersed PA6 particles as the molecular weight of POP diamine increasing from 230 to 400 to 2000. Using these PP-g-MA-co-POP copolymers, the compatibilized blends show improvements in mechanical properties, including Izod impact strength and tensile toughness, over a conventional compatibilizer. The POP and amide functionalities in the compatibilizers can facilitate the formation of hydrogen bonding with PA6 and, therefore, the compatibilizing effect. During the compounding process, the compatibilizers further react with PA6 in situ to afford the mixture of PP-g-MA-co-POP-PA6, PP-g-MA-co-POP-co-PA6 and PP-g-MA-co-PA6 copolymers, which further improves the compatibilizing effect. (C) 2000 Elsevier Science Ltd. All rights reserved.
Poly(oxypropylene)-amide grafted polypropylene as novel compatibilizer for PP and PA6 blends (vol 42, pg 713, 2001)
(2001-05-01)
Tseng, FP
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Lin, JJ
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Tseng, CR
;
Chang, FC
;
應用化學系
Preparation and characterization of polystyrene-clay nanocomposites by free-radical polymerization
(2002-08-15)
Tseng, CR
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Wu, JY
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Lee, HY
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Chang, FC
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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.
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.