Browsing by Author "Ou, CF"

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Blends of poly(butylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)]: Crystallization behaviors
(1996-06-06)
Song, WJ
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Ou, CF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Polyblends of poly(butylene terephthalate) (PBT) with four different types of co[poly(ethylene terephthalate-p-oxybenzoate)] copolyester, designated as P28, P46, P64, and P82, were prepared by melt-blending. The crystallization behaviors of the blends were then studied by differential scanning calorimetry and polarized optical microscopy (POM). Crystallization rate and temperature of neat PBT are increased when less than 10 wt % of P28 is blended. On the contrary, crystallization rate and temperature of neat PBT decrease when 10 wt % of P46, P64, or P82 copolyesters is blended. The crystallization behaviors of the blends are confirmed by the POM observations at the cooling cycles of the melts. On the other hand, melting endotherm onset temperature and melting peak width for all blends are comparable with those of neat PBT. These results imply that the stability and distribution of PBT crystallites in the blends are not significantly influenced by blending. The effects of POB content in the composition of the blends on the crystalline morphology were also presented. It is found that the structure of crystallites of the blends changed gradually with increasing the POB content in the composition of copolyester from lamellar to cross-like spherulite structures. (C) 1996 John Wiley & Sons, Inc.
Blends of poly(ethylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)] .3. Crystallization behavior observed by polarized light microscopy
(1996-08-29)
Ou, CF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Poly(ethylene terephthalate) (PET) has been melt-mixed at 293 degrees C with two types of co[poly(ethylene terephthalate-p-oxybenzoate)] (POB-PET) copolyester, designated as P28 and P82, at the level of 10 wt %. The different p-acetoxybenzoic acid/PET mole ratios are 20/80 in P28 and 80/20 in P82. The blends were heated to 305 degrees C and then cooled to 25 degrees C at rate of 10 degrees C/min. The crystalline morphology of these blends in the range from 25 degrees C to 305 degrees C is monitored by polarized light microscopy. Morphologic observations revealed a quicker appearance of crystalline in the blends upon the addition of 10 wt % copolyester as a nucleating agent. It is found that P28, which contains fewer POB units, is much more advantageous to the nucleation process than P82, which contains more POB units. According to the optical photomicrographs, sufficient uniformity of distribution of copolyester domains in the PET matrix is reached after 8 min blending. (C) 1996 John Wiley & Sons, Inc.
Blends of poly(ethylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)] .3. Crystallization behavior observed by polarized light microscopy
(1996-08-29)
Ou, CF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Poly(ethylene terephthalate) (PET) has been melt-mixed at 293 degrees C with two types of co[poly(ethylene terephthalate-p-oxybenzoate)] (POB-PET) copolyester, designated as P28 and P82, at the level of 10 wt %. The different p-acetoxybenzoic acid/PET mole ratios are 20/80 in P28 and 80/20 in P82. The blends were heated to 305 degrees C and then cooled to 25 degrees C at rate of 10 degrees C/min. The crystalline morphology of these blends in the range from 25 degrees C to 305 degrees C is monitored by polarized light microscopy. Morphologic observations revealed a quicker appearance of crystalline in the blends upon the addition of 10 wt % copolyester as a nucleating agent. It is found that P28, which contains fewer POB units, is much more advantageous to the nucleation process than P82, which contains more POB units. According to the optical photomicrographs, sufficient uniformity of distribution of copolyester domains in the PET matrix is reached after 8 min blending. (C) 1996 John Wiley & Sons, Inc.
Blends of poly(ethylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)] .4. Interchange reactions and their effects on the thermal and crystallization behaviors
(1996-08-29)
Ou, CF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Poly(ethylene terephthalate) (PET) was blended with a co[poly(ethylene terephthalate-p-oxybenzoate)] (POB-PET) copolyester which is a liquid crystalline polymer consisting of p-oxybenzoate and ethylene terephthalate units in a 40/60 mol ratio (P46). The level of P46 liquid crystalline polymer varies from 10 to 50 wt %. All the blends were prepared by melt-mixing in a Brabender Plasticorder at 275 degrees C for different times. The thermal and crystallization behaviors of blends depend on the blending time and the composition of blends, viz., the content of the p-oxybenzoate (POB) moiety incorporated into the blends. The interchange reactions detected by proton NMR analysis occur during the processing at a greater level if the blending time increases. These interchange reactions hinder the crystallization processes of PET and result in a decrease of the melting point, the heat of fusion, crystallization temperature, and the heat of crystallization of the original PET. The effects of the interchange reaction on thermal and crystallization behaviors of the blends may be attributed to the insertion of the rigid POB units into the soft PET chain. (C) 1996 John Wiley & Sons, Inc.
Co[poly(ethylene terephthalate-p-oxybenzoate)] and its blends with poly(ethylene terephthalate): Transesterification reaction and fractured surface morphology
(1996-02-28)
Ou, CF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A series of co[poly(ethylene terephthalate-p-oxybenzoate)] copolyesters, viz., P28, P46, P64, and P82, were synthesized. These copolyesters were blended with poly(ethylene terephthalate) (PET) at the level of 10 wt % at 293 degrees C for different times. The results from proton NMR analysis reveal that a significant amount of the transesterification has been detected in the cases of PET/P28, PET/P46, and PET/P64 blends. The blending time necessary before any transesterification reaction could be detected depends on the composition of copolyester, e.g., a time less than 3 min is needed for both PET/P28 and PET/P46 blends, while a longer time of 8-20 min is needed for the PET/P64 blend. It is concluded that the higher the mol ratio of the POB moiety in the copolyester is the longer the blending time needed to initiate the transesterification. The degree of transesterification is also increased as the duration of melt blending is prolonged. Two-phase morphology was observed by scanning electron microscopy (SEM) micrographs in all the blends. It was observed that the more similar the composition between the copolyester and PET in the blends is the better the miscibility or interfacial adhesion between the two phases. Moreover, the miscibility can be markedly improved by the duration of melt blending. (C) 1996 John Wiley & Sons, Inc.