Browsing by Author "Ju, MY"

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Compatibilization of PET/PS blends through SMA and PMPI dual compatibilizers
(2000-03-01)
Ju, MY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Tn this study, dual compatibilizers composed of styrene maleic anhydride random copolymer (SMA-8 wt.% MA) and poly[methylene (phenylene isocyanate)] (PMPI) have demonstrated to effectively compatibilize the immiscible and incompatible blends of poly(ethylene terephthalate) (PET) and polystyrene (PS). SMA with low MA content is totally miscible with PS to make the PS phase quasi-functionalized, so that PMPI has the chance to contact and react with PET and SMA simultaneously to form PET-co-PMPI-co-SMA copolymers at the interface. These desired copolymers are able to anchor along the interface and serve as efficient compatibilizers. The compatibilized blends, depending on the quantity of dual compatibilizers employed, exhibit higher viscosity, finer phase domain, and improved mechanical properties. Moreover, the crystallization behavior of the PET component in these compatibilized blends has been affected. (C) 1999 Elsevier Science Ltd. All rights reserved.
Crystal polymorphism of poly(butylene-2,6-naphthalate) prepared by thermal treatments
(2002-03-01)
Ju, MY
;
Huang, JM
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The crystal polymorphisms of the poly(butylene-2,6-naphthalate) (PBN) prepared by various thermal treatments in bulk state were investigated. Crystalline forms obtained from different thermal treatments were characterized using wide-angle X-ray diffraction (WAXD) measurements. The a-form crystal is obtained by annealing the quenched PBN sample in the solid state or by crystallizing from the static melt at a relatively lower temperature (T-C < 205 degreesC). On the other hand, an exclusive beta-form crystal is generated through unique thermal treatment by non-isothermal crystallization at a cooling rate of 0.1 degreesC min(-1) from 280 to 25 degreesC. Additionally, both alpha- and beta-form crystals appear in the sample melt-crystallized at a relatively higher temperature, and the relative ratio of the a- and P-forms depends on the predetermined crystallization temperature. In this study, it was found that the crystalline form transition never occurs in the solid state. Optical microscopic observations indicate that the a-form crystal exhibits a typical spherulite morphology, while the P-form crystal displays a dendritic spherulite morphology due to the extremely slow spherulite growth rate. Fourier transform infrared spectroscopy was used to examine the crystal structures of both a- and P-forms of the PBN. It is proposed that the main difference between these two crystal structures of PBN prepared by different thermal treatments lies in the packing efficiency of the crystal chains, rather than in the conformation change of the glycol residue, with the beta-form possessing tighter packing efficiency than the alpha-form. (C) 2002 Elsevier Science Ltd. All rights reserved.
Crystallization and melting behaviors of poly(trimethylene terephthalate)
(1999-10-01)
Huang, JM
;
Ju, MY
;
Chu, PP
;
Chang, FC
;
應用化學系
The crystallization and melting behaviors of poly(trimethylene terephthalate) (PTT) have been studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and solid-state NMR. At certain crystallization temperatures (T-c) for a given time, the isothermally crystallized PTT exhibits two melting endotherms, which is similar to that of PBT and PBT. At higher crystallization temperature (T-c = 210 degrees C), the low-temperature endotherm is related to the melting of the original crystals, while the high-temperature endotherm is associated with the melting of crystals recrystallized during the hearing. The peak temperatures of these double-melting endotherms depend on crystallization temperature, crystallization time, and cooling rate from the melt as well as the subsequent heating rate. At a low cooling rate (0.2 degrees C/min) or a high heating rate (40 degrees C/min), these two endotherms tend to coalesce into a single endotherm, which is considered as complete melting without reorganization. WAXD results confirm that only one crystal structure exists in the PTT sample regardless of the crystallization conditions even with the appearance of double melting endotherms. The results of NMR reveal that the annealing treatment increases proton spin lattice relaxation time in the rotation frame, T-1 rho(H), of the PTT. This phenomenon suggests that the mobility of the PTT molecules decreases after the annealing process. The equilibrium melting temperature (T(m)degrees) determined by the Hoffman-Weeks plot is 248 degrees C.
Morphologies and mechanical properties of polyarylate liquid crystalline polymer blends compatibilized by a multifunctional epoxy resin
(2000-12-06)
Ju, MY
;
Chen, MY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Full Paper: The tetrafunctional epoxy resin, tetraglycidyl-4',4'-diaminodiphenyl methane (TGDDM), has been investigated as an efficient reactive compatibilizer for the blends of polyarylate (PAr) with a liquid crystalline polymer (LCP). TGDDM can react with PAr and LCP at the interface simultaneously to produce the PAr-co-TGDDM-co-LCP mixed copolymers during melt blending. These copolymers tend to anchor along the interface as the result of the interfacial reaction and thus serve as effective compatibilizers to reduce the interfacial tension and to enhance the interfacial adhesion in the solid state. The morphologies of the PAr/LCP blends were inspected by means of scanning electron microscopy (SEM). It is observed that the dispersed LCP phase domains reduce,obviously after compatibilization. Furthermore, it is also found that the reduced interfacial tension caused by the addition of TGDDM plays a vital role in affecting the deformation of the LCP phase domains in the compatibilized PAr/LCP blends. The LCP phase tends to,deform into greater numbers and finer fibrils with high aspect ratio after the addition of TGDDM in those blends containing adequate LCP content (>10 %). In the blend containing low amount of LCP (Par / LCP = 95/5) with high TGDDM content (0.3 phr or higher), however, the LCP phase can only exist as fine but short fibrils or even ellipsoids, The overall mechanical properties of the PAr/LCP blends are substantially improved after compatibilization by this coupling-type reactive compatibilizer. The generation of LCP fibrils with high aspect ratio and improved interfacial adhesion are the two hinges to enhance the performance of the compatibilized PAr/LCP blends.
Multiple melting behavior of poly(butylene-2,6-naphthalate)
(2001-05-01)
Ju, MY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Multiple melting behaviors of poly(butylene-2,6-naphthalate) (PBN) prepared by various crystallization conditions were studied by differential scanning calorimetry at a heating rate of 10 degreesC/min. It is found that the crystallization rate of PEN is so rapid that the glass transition temperature cannot be detected by simply heating the quenched sample. Two melting peaks are generally perceptible in a heating scan for isothermally crystallized samples that can be properly explained by the model proposed by Zhou and Clough (Polym Engng Sci 28 (1988) 65). The low-temperature melting peak can be ascribed to the melting of primary and secondary crystals generated during the crystallization or annealing process, while the high-temperature melting peak comes from the significant contribution of the melting of recrystallized species formed during heating. The step-crystallization was performed to clarify the relationship between the melting behavior and crystal modifications of PEN. In this study, it is found that the melting behavior of PEN is independent of the crystal forms and dominated by the crystal lamellar thickness and the perfection of crystals, which are dependent upon the thermal history. Finally, an equilibrium melting temperature of 276 degreesC is obtained for the neat PEN, which is lower than that published in the literature. (C) 2001 Elsevier Science Ltd. All rights reserved.
Polymer blends of PA6 and PPE compatibilized by poly[methylene(phenyleneisocyanate)] (PMPI) coupler
(1998-04-01)
Chiang, CR
;
Ju, MY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
An oligomeric isocyanate, poly[methylene(phenylene isocyanate)] (PMPI), is demonstrated to be an efficient reactive compatibilizer for blends of polyamide-6 (PA6) and poly(2,6-dimethyl-1,4-phenylene ether)(PPE). Use of this compatibilizer results in substantial improvements in mechanical properties. The multiple functional isocyanate acts as a coupling agent and reacts with PA6 and PPE endgroups during melt processing to produce a PA6-co-PMPI-co-PPE mixed copolymer at the interface. This in situ-formed copolymer tends to reside at the interface to reduce the melt interfacial tension and enhance interface adhesion.
Polymer blends of poly(ethylene-2,6-naphthalate) with polystyrene compatibilized by styrene-glycidyl methacrylate copolymers. I. Rheology, morphology, and mechanical properties
(2003-02-07)
Huang, JM
;
Ju, MY
;
Hung, CJ
;
Luoh, WC
;
Chang, FC
The compatibilization of blends of poly(ethylene-2,6-naphthalate) (PEN) with polystyrene (PS), through the styrene-glycidyl methacrylate copolymers (SG) containing various glycidyl methacrylate (GMA) contents, was investigated in this study. SG copolymers are able to react with PEN terminal groups during melt blending, resulting in the formation of desirable SG-g-PEN copolymers in the blend. These in situ formed copolymers tend to reside along the interface preferentially as the result of interfacial reaction and thus function as effective compatibilizers in PEN/PS blends. The compatibilized blends exhibit higher viscosity, finer phase domain, and improved mechanical properties. It is found that the degree of grafting of the in situ formed SG-g-PEN copolymer has to be considered as well. In blends compatibilized with the SG copolymer containing higher GMA content, heavily grafted copolymers would be produced. The length of the styrene segment in these heavily grafted copolymers would be too short to penetrate deep enough into the PS phase to form effective entanglements, resulting in the lower compatibilization efficiency in PEN/PS blends. Consequently, the in situ formation of SGg-PEN copolymers with an optimal degree of grafting is the key to achieving the best performance for the eventually produced PEN/PS blends through SG copolymers. (C) 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 967-975, 2003.