The crystallization rate of poly(ethylene terephthalate) accelerated by co[poly(butylene terephthalate‐p‐oxybenzoate)] copolyesters

Poly(ethylene terephthalate) (PET) was blended with three different kinds of co[poly(butylene terephthalate‐p‐oxybenzoate)] copolyesters, designated B28, B46, and B64, with the level of copolyester varying from 1 to 15 wt %. All samples were prepared by solution blending in a 60/40 by weight phenol/tetrachloroethane solvent at 50°C. The crystallization behavior of samples was then studied via differential scanning calorimetry. The results indicate that these three copolyesters accelerate the crystallization rate of PET in a manner similar to that of a nucleating agent. The acceleration of PET crystallization rate was most pronounced in the PET/B28 blends with a maximum level at 10 wt % of B28. The melting temperatures for the blends are comparable with that of pure PET. The observed changes in crystallization behavior are explained by the effect of the physical state of the copolyester during PET crystallization as well as the amount of copolyester in the blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 587–593, 2000     

Co[poly(ethylene terephthalate-p-oxybenzoate)] and its blends with poly(ethylene terephthalate): Transesterification reaction and fractured surface morphology

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°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. © 1996 John Wiley & Sons, Inc.     

Thermal and crystallization characteristics of poly(ethylene terephthalate) with poly(oxybenzoate‐p‐trimethylene terephthalate) copolymer

Poly(ethylene terephthalate) (PET) was blended with two different poly(oxybenzoate‐p‐trimethylene terephthalate) copolymers, designated T28 and T64, with the level of copolymer varying from 1 to 15 wt %. All samples were prepared by solution blending in a 60/40 (by weight) phenol/tetrachloroethane solvent at 50°C. The crystallization behavior of the samples was studied by DSC. The results indicate that both T28 and T64 accelerated the crystallization rate of PET in a manner similar to that of a nucleating agent. The acceleration of PET crystallization rate was most pronounced in the PET/T64 blends with a maximum level at 5 wt % of T64. The melting temperatures for the blends are comparable to that of pure PET. The observed changes in crystallization behavior are explained by the effect of the physical state of the copolyester during PET crystallization as well as the amount of copolymer in the blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1599–1606, 2002     

Characterizations for blends of phosphorus-containing copolyester with poly(ethylene terephthalate)

High molecular weight phosphorus-containing copolyesters, poly(ethylene terephthalate)-co-poly(ethylene DDP) (PET-co-PEDDP)s, were prepared and characterized with the objective of producing a non-halogen flame retardant system for practical applications. The phosphorus-containing copolyester with 30 wt% phosphorus (P30 copolyester) was blended with PET to evaluate their characteristics and flame retardancy. Higher phosphorus content results in lower crystallinity and higher char formation after thermal degradation. The rheological behavior remains similar to that of PET. The P30/PET blend possesses higher crystallization rate than the corresponding phosphorus-containing copolyester containing equal phosphorus content. Thermal and rheological behaviors of P30/PET blends are similar to PET or the phosphorus-containing copolyesters. The P30/PET blends are miscible or compatible base on single T_gs detected by DSC or DMA. The SEM/EDX phosphorus mapping image of the P30/PET blend shows uniform distribution of the phosphorus moieties within the P30/PET matrix, another indication of a compatible or miscible blend between the phosphorus-containing copolyester P30 and PET. Flame retardancy of the P30/PET blend is identical to that of the phosphorus-containing copolyester with identical phosphorus content. Blending of high phosphorus content copolyester with virgin PET provides a feasible method to obtain a flame resistant PET with LOI greater than 28.     

Co[poly(ethylene terephthalate-p-oxybenzoate)] thermotropic copolyester. II. X-ray diffraction analysis

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. © 1993 John Wiley & Sons, Inc.     

Studies on co[poly(ethylene terephthalate-p-oxybenzoate)] thermotropic copolyester (I): Synthesis and thermogravimetric behavior

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. © 1993 John Wiley & Sons, Inc.     

Blends of poly(butylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)]: Crystallization behaviors

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. © 1996 John Wiley & Sons, Inc.     

Interchange reactions between poly(ethylene terephthalate) and its copolyesters

Poly(ethylene terephthalate) (PET) was blended with two kinds of co[poly-(ethylene terephthalate-p-oxybenzoate)] (POB-PET) copolyester, designated P46 and P64. The PET and POB-PET copolyester were combined in the ratios of 85/15, 70/30, and 50/50. The blends were melt-mixed in a Brabender Plasticorder at 275, 285, and 293°C for different times. The interchange reactions detected by proton nuclear magnetic resonance analysis occur during the processing at a greater level if the blending time increases. The interchange reactions are as a function of temperature, blending times, and composition of blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1591–1595, 1998     

Study on the kinetics of transesterification reaction between poly(ethylene terephthalate) and its copolyesters

Polyethylene terephthalate (PET) was blended with two kinds of co[poly(ethylene terephthalate-p-oxybenzoate)] (POB–PET) copolyester, designated as P46 and P64, respectively. The PET and POB–PET copolyester were combined in the ratios of 85/15, 70/30, and 50/50. The blends were melt mixed in a Brabender Plasticorder at 275, 285, and 293°C for different amounts of time. The transesterification reactions during the melt mixing processes of PET with POB–PET copolyester blends were detected by proton nuclear magnetic resonance analysis. The values of the rate constants are a function of temperature and the composition of blends. The transesterification reactions that may occur during the melt mixing processes have been discussed also. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2727–2732, 1999     

Studies on co[poly(ethylene terephthalate-p-oxybenzoate)] thermotropic copolyester (IV) thermal history by differential scanning calorimetry

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. © 1994 John Wiley & Sons, Inc.     

Studies on co[poly(ethylene terephthalate-p-oxybenzoate)] thermotropic copolyester: Thermomechanical and thermodynamic properties

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. © 1995 John Wiley & Sons, Inc.     

MELTING BEHAVIOR OF POLYETHYLENE TEREPHTHALATE COPOLYESTER AND POLYSTYRENE BLENDS

The melting behavior of polyethylene terephthalate (PET) copolyester/polystyrene (PS) blends was studied using differential scanning calorimetry. Multiple melting endotherms were observed for the PET copolyester as well as the PET copolyester/PS blend at T_c = 483 and 493 K, respectively. A higher crystallization temperature resulted in the reorganization of the crystalline species and an increase in area under the reorganization peak. Higher melting temperatures for PS-rich blends may be attributed to the formation of a stiffer matrix around the crystallites and the possible inhibition of crystal thickening. Melting behavior shows that the PET copolyester and PS form miscible blends up to 30 wt.% of PS, whereas with the lowering of the isothermal crystallization temperature to 483 K, miscibility was found only up to 10 wt.% of PS.     

Preparation and biodegradation of copolyesters based on poly(ethylene terephthalate) and poly(ethylene glycol)/oligo(lactic acid) by transesterification

The poly(ethylene terephthalate‐co‐ethyleneoxide‐co‐DL ‐lactide) copolymers were successfully prepared by the melt reaction between poly(ethylene terephthalate), poly(ethylene glycol), and DL ‐oligo(lactic acid) without any catalysts. The transesterification between ethylene terephthalate, ethyleneoxide, and lactide segments during the reaction was confirmed by the ¹H NMR analysis. The effect of reaction temperatures and the starting feed ratios on the molecular microstructures, molecular weights, solubility, thermal properties, and degradability of the copolyesters was extensively studied. The values of crystallization temperature, melting temperature, crystallization, and melting enthalpy of the copolyesters were found to be influenced by the reaction temperatures, starting feed ratios, etc. The copolyesters showed good tensile properties and were found to degrade in the soil burial experiments during the period of 3 months. The morphology of the copolyester films were also investigated by scanning electron microscopy during soil burial degradation. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Syntheses and characterization of poly(ethylene terephthalate) modified with p-acetoxybenzoic acid

Though the structure and properties of a copolyester of 40 mole % of polyethylene terephthalate (PET) and 60 mole % p-hydroxybenzoic acid (PHB) (PET/60PHB) and their blends have been well documented, no work has been reported in an open literature on the systematic investigation of the PET copolymers modified with broad range of p-acetoxybenzoic acid (PABA) composition as yet. In this study, several PETA-x copolyesters having various PABA compositions from 10 to 70 mole % were prepared by the melt reaction of PABA and PET without a catalyst, where x denotes the mole % of PABA. And the modified polyesters obtained were characterized by ¹H-NMR spectrophotometry, X-ray diffraction pattern, polarizing microscopy, thermal analysis, and rheometry. The anisotropic phase appeared when x is above 50 mole % of PABA, and especially for the x's of 60 and 70 mole %, the nematic liquid crystalline texture appeared clearly on the whole matrix. As the mole % of PABA increased, melting temperature, heat of fusion, crystalline temperature, degree of crystallinity, and the glass transition temperature of the modified PET were decreased, but the thermal stabilities of those copolyesters were increased. The dependence of melt viscosity on the shear rate for PETA-50 ∼ 70 followed the typical rheological behavior of liquid crystalline polymers. Finally, it was concluded that the PETA-x copolyesters having compositions of higher than 50 mole % of PABA exhibit the behavior of thermotropic liquid crystalline polymers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1707–1719, 1999     

聚(对苯二甲酸乙二醇酯-co-对苯二甲酸异山梨醇酯)等温结晶行为研究

以对苯二甲酸(PTA)、乙二醇(EG)、异山梨醇(ISB)为原料,通过直接熔融缩聚法合成聚(对苯二甲酸乙二醇酯-co-对苯二甲酸异山梨醇酯)(PEIT)共聚酯。利用差示扫描量热法(DSC)研究了共聚酯的结晶行为,采用Avrami方程分析了共聚酯的等温结晶动力学。结果表明,PEIT共聚酯结晶行为受共聚组成和结晶温度影响。随着ISB用量的增加或结晶温度的降低,共聚酯半结晶周期t1/2增加、结晶速率变慢;ISB摩尔分数超过20%,共聚酯无法结晶。     

Microstructure and crystallization of melt‐mixed poly(ethylene terephthalate)/poly(ethylene isophthalate) blends

Physical blends of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI), abbreviated PET/PEI (80/20) blends, and of PET and a random poly(ethylene terephthalate‐co‐isophthalate) copolymer containing 40% ethylene isophthalate (PET₆₀I₄₀), abbreviated PET/PET₆₀I₄₀ (50/50) blends, were melt‐mixed at 270°C for different reactive blending times to give a series of copolymers containing 20 mol % of ethylene isophthalic units with different degrees of randomness. ¹³C‐NMR spectroscopy precisely determined the microstructure of the blends. The thermal and mechanical properties of the blends were evaluated by DSC and tensile assays, and the obtained results were compared with those obtained for PET and a statistically random PETI copolymer with the same composition. The microstructure of the blends gradually changed from a physical blend into a block copolymer, and finally into a random copolymer with the advance of transreaction time. The melting temperature and enthalpy of the blends decreased with the progress of melt‐mixing. Isothermal crystallization studies carried out on molten samples revealed the same trend for the crystallization rate. The effect of reaction time on crystallizability was more pronounced in the case of the PET/PET₆₀I₄₀ (50/50) blends. The Young's modulus of the melt‐mixed blends was comparable to that of PET, whereas the maximum tensile stress decreased with respect to that of PET. All blend samples showed a noticeable brittleness. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3076–3086, 2003     

Effect of monomer composition on the rheological properties of poly(p-oxybenzoate-co-ethylene terephthalate)s

Summary Effect of monomer composition on the dynamic viscoelastic properties and the steady flow properties of thermotropic liquid crystalline poly (p-oxybenzoate-co-ethylene terephthalate)s in the fluid state have been investigated as compared with the isotropic melt of the copolyester including 28 mol% p-oxybenzoate unit (POB). The liquid crystalline copolyesters show the rheological transition temperature, which increases with increasing the content of POB unit. Above the transition temperature, all the thermotropic copolyesters exhibit much higher compliance and much more shear-thinning behavior of the apparent viscosity than the isotropic melt of the non-liquid crystalline copolyester.     

Biodegradable poly(ethylene succinate) blends and copolymers containing minor amounts of poly(butylene succinate)

Poly(ethylene succinate) (PES), poly(butylene succinate) (PBS), and PES‐rich copolyesters were synthesized using an effective catalyst, titanium tetraisopropoxide. PES was blended with minor amounts of PBS for the comparison. The compositions of the copolyesters and the blends were determined from NMR spectra. Their thermal properties were studied using a differential scanning calorimeter (DSC), a temperature modulated DSC (TMDSC), and a thermogravimetric analyzer. No significant difference exists among the thermal stabilities of these polyesters and blends. For the blends, the reversible curves of TMDSC showed a distinct glass‐rubber transition temperature (T_g), however, the variation of the T_g values with the blend compositions was small. Isothermal crystallization kinetics and the melting behavior after crystallization were examined using DSC. Wide‐angle X‐ray diffractograms (WAXD) were obtained for the isothermally crystallized specimens. The results of DSC and WAXD indicate that the blends have a higher degree of crystallinity and a higher melting temperature than those of the corresponding copolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Crystallization of poly(butylene terephthalate)/poly(ethylene octene) blends: Nonisothermal crystallization

Poly(ethylene octene) (POE), maleic anhydride grafted poly(ethylene octene) (mPOE), and a mixture of POE and mPOE were added to poly(butylene terephthalate) (PBT) to prepare PBT/POE (20 wt % POE), PBT/mPOE (20 wt % mPOE), and PBT/mPOE/POE (10 wt % mPOE and 10 wt % POE) blends with an extruder. The melting behavior of neat PBT and its blends nonisothermally crystallized from the melt was investigated with differential scanning calorimetry (DSC). Subsequent DSC scans exhibited two melting endotherms (T_mI and T_mII). T_mI was attributed to the melting of the crystals grown by normal primary crystallization, and T_mII was due to the melting of the more perfect crystals after reorganization during the DSC heating scan. The better dispersed second phases and higher cooling rate made the crystals that grew in normal primary crystallization less perfect and relatively prone to be organized during the DSC scan. The effects of POE and mPOE on the nonisothermal crystallization process were delineated by kinetic models. The dispersed phase hindered the crystallization; however, the well‐ dispersed phases of an even smaller size enhanced crystallization because of the higher nucleation density. The nucleation parameter, estimated from the modified Lauritzen–Hoffman equation, showed the same results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008