Browsing by Author "SHINN, TH"

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CO[POLY(ETHYLENE TEREPHTHALATE-P-OXYBENZOATE)] THERMOTROPIC COPOLYESTER .2. X-RAY-DIFFRACTION ANALYSIS
(1993-02-10)
SHINN, TH
;
LIN, CC
;
應用化學系
;
Department of Applied Chemistry
A series of co [poly (ethylene terephthalate-p-oxybenzoate)] thermotropic copolyester with different compositions were prepared by the copolymerization of either poly(ethylene terephthalate) (PET) polymer or its oligomer with p-acetoxy-benzoic acid. The polymeric products were subjected to solid-state polymerization for various time intervals. Effects of composition ratio and solid-state polymerization time on X-ray diffraction behavior were investigated. It is found that the effect of transesterification induced by solid-state polymerization causes an increase in crystallinity with the copolyesters having high mol % of p-oxybenzoic acid (POB) moiety and causes a decrease in crystallinity with the copolyesters having high mol % of PET moiety. In general, the crystallinity of copolyesters is first increased and then decreased as solid-state polymerization time proceeds. However, the crystallinity of copolyester having POB/PET = 80/20 composition is increased generally at 4-h solid-state polymerization. It is also found that the crystallinity of copolyesters is decreased by quenching. The copolyester based upon either PET oligomer with 4-h solid-state polymerization or PET polymer with 8-h solid-state polymerization shows the most similar X-ray diffraction pattern with that of Eastman 10109.
STUDIES ON CO[POLY(ETHYLENE TEREPHTHALATE-P-OXYBENZOATE)] THERMOTROPIC COPOLYESTER (III) - MORPHOLOGICAL OBSERVATION BY POLARIZING MICROSCOPY
(1993-08-10)
SHINN, TH
;
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)] thermotropic copolyesters with various compositions were prepared by the copolymerization of either poly (ethylene terephthalate) (PET) polymer or its oligomer as moiety (I) and p-acetoxybenzoic acid as moiety (II). A detailed description of the crystalline morphology of copolyesters with different compositions as well as under different preparation temperatures is discussed by using a polarized optical micrograph. It is found that the p-oxybenzoate (POB)/PET copolyesters with the POB moiety content above 60 mol % were shown to be highly anisotropic. It is also believed that the copolyester made from the PET oligomer (OET) as moiety (II) has shorter repeating units than that of the copolyester made from PET polymer (PET) in the main-chain structure. The solid-state polymerization may cause the randomization of two units due to a transesterification reaction that is examined by NMR spectroscopy analysis. Using the micrographs with different compositions, parallels between before and after the solid-state polymerization are contrasted. (C) 1993 John Wiley & Sons, Inc.
STUDIES ON CO[POLY(ETHYLENE TEREPHTHALATE-P-OXYBENZOATE)] THERMOTROPIC COPOLYESTER - SEQUENCE DISTRIBUTION EVALUATED FROM TSC MEASUREMENTS
(1995-01-01)
SHINN, TH
;
LIN, CC
;
LIN, DC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Relaxation!transition behaviours for copolyesters made from poly(ethylene terephthalate) (PET) and p-acetoxybenzoic acid (POB) have been characterized by thermally stimulated current (TSC) measurement. The sequence distribution, in terms of the degree of blockiness, in dual chemidomains of POB/PET copolyester is simulated from a model developed by us to predict the probability between block sequence and random sequence under a given composition and measuring condition. It is found that the degree of blockiness, a measure of sequence distribution, under the same polarization temperature generally increases with increasing POB content in the POB/PET copolyester. For copolyesters of the same composition, the degree of blockiness shows a large decrease after solid-state polymerization when high molecular weight PET is used, whereas it shows only a small decrease or an increase after solid-state polymerization when PET of lower molecular weight is used. It is concluded that the change in the degree of blockiness caused by the solid-state polymerization of copolyesters is dependent on the molecular weight of sequences of the PET moiety in the structure.
STUDIES ON CO[POLY(ETHYLENE TEREPHTHALATE-P-OXYBENZOATE)] THERMOTROPIC COPOLYESTER - THERMOMECHANICAL AND THERMODYNAMIC PROPERTIES
(1995-12-12)
SHINN, TH
;
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)] thermotropic copolyesters were prepared by the copolymerization of poly(ethylene terephthalate) (PET) as moiety (II) and p-acetoxybenzoic acid (POB) as moiety (I). The polymeric products obtained were subjected to solid-state polymerization. Characterization of the copolyesters by thermomechanical analysis shows that properties such as the coefficient of thermal expansion, transition temperature, and maximum softening rate temperature varied directly as a function of composition as well as did solid-state polymerization time. All thermomechanical data were found to increase with the solid-state polymerization time due to the increase in the degree of polymerization and the effect of annealing. The coefficient of thermal expansion behaves in a manner that is interpretable by the crystalline state of the copolyester. The relationship between the free-volume fraction and thermodynamic properties is further correlated for a more comprehensive discussion on its molecular arrangements. (C) 1995 John Wiley & Sons. Inc.
STUDIES ON CO[POLY(ETHYLENE TEREPHTHALATE-P-OXYBENZOATE)] THERMOTROPIC COPOLYESTER(IV) THERMAL HISTORY BY DIFFERENTIAL SCANNING CALORIMETRY
(1994-03-07)
SHINN, TH
;
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)] thermotropic copolyesters with various compositions were prepared by the copolymerization of either poly (ethylene terephthalate) polymer (PET) or its oligomer (OET) as moiety (II) and p -acetoxy-benzoic acid (POB) as moiety (I). The polymeric products obtained were then subjected to solid-state polymerization. The glass and melting transitions of the copolyesters obtained have been studied by differential scanning calorimetry (DSC). Effects of composition and solid-state polymerization on DSC are discussed. The melting point of copolyesters possesses a higher value if the PET polymer is used as PET moiety in the copolyesters. In the DSC scan of the POB rich composition, the endothermic peak shows obscurely and enthalpy of fusion becomes small due to the change in the crystalline morphology from isotropic to anisotropic. In general, the melting point of copolyesters is increased by the solid-state polymerization reaction. It is also found that both the melting temperature and enthalpy of fusion of the copolyesters can be increased simultaneously by the solid-state polymerization reaction only when the composition of POB / PET is 80 / 20. This phenomenum at this composition may be attributed to the annealing effect caused by the randomness of two moiety units on the backbone chain of copolyesters and the increased molecular weight as well. (C) 1994 John Wiley & Sons, Inc.
STUDIES ON CO[POLY(ETHYLENE TEREPHTHALATE-P-OXYBENZOATE)]THERMOTROPIC COPOLYESTER (I) - SYNTHESIS AND THERMOGRAVIMETRIC BEHAVIOR
(1993-02-15)
SHINN, TH
;
CHEN, JY
;
LIN, CC
;
應用化學系
;
Department of Applied Chemistry
A series of co[poly (ethylene terephthalate-p-oxybenzoate)] thermotropic copolyester was synthesized from various ratios of two different moieties of either poly(ethylene terephthalate) (PET) or its oligomer as moiety (II) with p-acetoxybenzoic acid as moiety (I) through the polycondensation process. The polymeric products obtained were then ground and subjected to solid-state polymerization under vacuum for various polymerization times. Thermogravimetric analysis (TGA) and the derivative thermogravimetric analysis (DTG) were performed with these samples obtained. Also, a commercial product, Eastman 10109, was analyzed in comparison with these samples. It was found that the copolyesters made of PET and of its oligomer in a p-oxybenzoate (POB):PET = 80:20 composition ratio and subjected to 8 and 4 h solid-state polymerization times, respectively, showed the most similar thermogravimetric behavior with Eastman 10109.