Thermal,crystallization, mechanical,and rheological characteristics of poly(trimethylene terephthalate)/poly(ethylene terephthalate) blends

Blends of poly(trimethylene terephthalate) (PTT) and poly(ethylene terephthalate) in the amorphous state were miscible in all of the blend compositions studied, as evidenced by a single, composition‐dependent glass‐transition temperature observed for each blend composition. The variation in the glass‐transition temperature with the blend composition was well predicted by the Gordon–Taylor equation, with the fitting parameter being 0.91. The cold‐crystallization (peak) temperature decreased with an increasing PTT content, whereas the melt‐crystallization (peak) temperature decreased with an increasing amount of the minor component. The subsequent melting behavior after both cold and melt crystallizations exhibited melting point depression behavior in which the observed melting temperatures decreased with an increasing amount of the minor component of the blends. During crystallization, the pure components crystallized simultaneously just to form their own crystals. The blend having 50 wt % of PTT showed the lowest apparent degree of crystallinity and the lowest tensile‐strength values. The steady shear viscosity values for the pure components and the blends decreased slightly with an increasing shear rate (within the shear rate range of 0.25–25 s^?1); those of the blends were lower than those of the pure components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 676–686, 2004     

Relaxation behavior of poly(ethylene terephthalate)/poly(ethylene naphthalene 2,6‐dicarboxylate) blends prepared by cryogenic blending

A method including cryogenic grinding, melt pressing from the molten state, and quenching was used to prepare blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) in which the two phases were highly dispersed. The effect of melt‐pressing times on the thermal properties and relaxation behavior of PET/PEN films were characterized with differential scanning calorimetry and dielectric spectroscopy. For short melt‐pressing times, two glass‐transition, two crystallization, and two melting peaks were observed, indicating the presence of PET‐rich and PEN‐rich phases in these blends. Longer melt‐pressing times revealed a single glass transition and a single α‐relaxation process, showing that PET–PEN block copolymers were likely to be formed during the melt pressing. The experimental findings were examined in terms of the transesterification reactions between the blend components, as revealed by ¹H NMR measurements. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2570–2578, 2002     

Transesterification kinetics of poly(ethylene terephthalate) and poly(ethylene 2,6‐naphthalate) blends with the addition of 2,2′‐bis(1,3‐oxazoline)

The kinetics of the transesterification reaction between poly(ethylene terephthalate) (PET) and poly(ethylene 2,6‐naphthalate) (PEN) with and without the addition of a chain extender were studied with ¹H NMR. Different kinetic approaches were considered, and a second‐order, reversible reaction was accepted for the PET/PEN reactive blend system. The addition of 2,2′‐bis(1,3‐oxazoline) (BOZ) promoted the transesterification reaction between PET and PEN in the molten state. The activation energy of the transesterification reaction for the PET/PEN reactive blend with BOZ (94.0 kJ/mol) was lower than that without BOZ (168.9KJ/mol). The rate constant k took an almost constant value for blend samples with different compositions mixed at 275 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2607–2614, 2001     

Thermal and crystallization characteristics of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends were miscible in the amorphous state in all of the blend compositions studied, as evidenced by a single, composition-dependent glass transition temperature (T_g) observed for each blend composition. The variation in the T_g value with the blend composition was well predicted by the Gordon-Taylor equation, with the fitting parameter being 0.57. The cold-crystallization peak temperature decreased with increasing PTT content, while the melt-crystallization peak temperature decreased with increasing amount of the minor component. The subsequent melting behavior after both cold- and melt-crystallization exhibited melting point depression, in which the observed melting temperatures decreased with increasing amount of the minor component. During melt-crystallization, both components in the blends crystallized concurrently just to form their own crystals. The blend with 60% w/w of PTT exhibited the lowest total apparent degree of crystallinity.     

A DSC study of miscibility and phase separation in crystalline polymer blends of phenolphthalein poly(ether ether sulfone) and poly(ethylene oxide)

The miscibility of blends of phenolphthalein poly(ether ether sulfone) (PES-C) and poly(ethylene oxide) (PEO) was established on the basis of the thermal analysis results. Differential scanning calorimetry (DSC) studies showed that the PES-C/PEO blends prepared by casting from N,N-dimethylformamide (DMF) possessed a single, composition-dependent glass transition temperature (T_g), and thus that PES-C and PEO are miscible in the amorphous state at all compositions at lower temperature. At higher temperature, the blends underwent phase separation, and the PES-C/PEO blend system was found to display a lower critical solution temperature (LCST) behavior. The phase separation process in the blends has also been investigated by using DSC. Annealed at high temperatures, the PES-C/PEO blends exhibited significant changes of thermal properties, such as the enthalpy of crystallization and fusion, temperatures of crystallization and melting, depending on blend composition when phase separation occurred. These changes reflect different characteristics of phase structure in the blends, and were taken as probes to determine phase boundary. From both the thermal analysis and optical microscopy, the phase diagram of the blend system was established. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1383–1392, 1997     

Synthesis and characterization of a vinyl‐terminated benzoxazine monomer and its blends with poly(ethylene oxide)

A vinyl‐terminated benzoxazine (VB‐a), which could be polymerized through ring‐opening polymerization, was synthesized through the Mannich condensation of bisphenol A, formaldehyde, and allylamine. This VB‐a monomer was then subjected to blending with poly(ethylene oxide) (PEO), followed by thermal curing, to form poly(VB‐a)/PEO blends. The specific interactions, miscibility, morphology, and thermal properties of these blends were investigated with Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). Before curing, we found that PEO was miscible with VB‐a, as evidenced by the existence of a single composition‐dependent glass transition temperature (T_g) for each composition. The FTIR spectra revealed the presence of hydrogen‐bonding interactions between the hydroxyl groups of poly(VB‐a) and the ether groups of PEO. Indeed, the ring‐opening reaction and subsequent polymerization of the benzoxazine were facilitated significantly by the presence of PEO. After curing, DMA results indicated that the 50/50 poly(VB‐a)/PEO blend exhibited two values of T_g: one broad peak appeared in the lower temperature region, whereas the other (at ca. 327 °C, in the higher temperature region) was higher than that of pristine poly(VB‐a) (301 °C). The presence of two glass transitions in the blend suggested that this blend system was only partially miscible. Moreover, SEM micrographs indicated that the poly(VB‐a)/PEO blends were heterogeneous. The volume fraction of PEO in the blends had a strong effect on the morphology. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 644–653, 2007     

Studies of photooxidative degradation of poly(vinyl chloride)/poly(ethylene oxide) blends

The photooxidative degradation of blends (in a full range of compositions) of amorphous poly(vinyl chloride) (PVC) with semicrystalline poly(ethylene oxide) (PEO) in the form of thin films is investigated using absorption spectroscopy (UV–visible and Fourier transform infrared) and atomic force microscopy (AFM). The amount of insoluble gel formed as a result of photocrosslinking is estimated gravimetrically. It is found that the PVC/PEO blendsí susceptibility to photooxidative degradation differs from that pure of the components and depends on the blend composition and morphology. Photoreactions such as degradation and oxidation are accelerated whereas dehydrochlorination is retarded in blends. The photocrosslinking efficiency in PVC/PEO blends is higher than in PVC; moreover, PEO is also involved in this process. AFM images showing the lamellar structure of semicrystalline PEO in the blend lead to the conclusion that the presence of PVC does not disturb the crystallization process of PEO. The changes induced by UV irradiation allow the observation of more of the distinct PEO crystallites. This is probably caused by recrystallization of short, more mobile chains in degraded PEO or by partial removal of the less stable amorphous phase from the film surface. These results confirm previous information on the miscibility of PVC with PEO. The mechanism of the interactions between the components and the blend photodegradation are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 585–602, 2004     

Segmented block copolymers of poly(ethylene glycol) and poly(ethylene terephthalate)

A new series of segmented copolymers were synthesized from poly(ethylene terephthalate) (PET) oligomers and poly(ethylene glycol) (PEG) by a two‐step solution polymerization reaction. PET oligomers were obtained by glycolysis depolymerization. Structural features were defined by infrared and nuclear magnetic resonance (NMR) spectroscopy. The copolymer composition was calculated via ¹H NMR spectroscopy. The content of soft PEG segments was higher than that of hard PET segments. A single glass‐transition temperature was detected for all the synthesized segmented copolymers. This observation was found to be independent of the initial PET‐to‐PEG molar ratio. The molar masses of the copolymers were determined by gel permeation chromatography (GPC). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4448–4457, 2004     

Complete miscibility of ternary aryl polyesters demonstrating a new criterion and horizon for miscibility characterization

A ternary miscible blend system comprising only crystallizable aryl polyesters [poly(ethylene terephthalate), poly(trimethylene terephthalate), and poly(butylene terephthalate)] was characterized with the criteria of thermal analyses, microscopy, and X‐ray characterizations. The reported ternary miscibility (in the quenched amorphous state of blends of the three aryl polyesters) was truly physical and under the condition of no chemical transesterifications; this justified that transesterification was not a necessary condition for miscibility in polyester blends in this case. This study further proposed and tested a novel concept of a new criterion for miscibility characterization for polymer blends of only crystallizable polymers. A single composition‐dependent cold‐crystallization‐temperature (T_cc) peak in blends of only semicrystalline polymers was taken as an indication of an intimate mixing state of miscibility. The theoretical background for establishing the single composition‐dependent T_cc peak as a valid miscibility criterion for crystallizable polymer blends was examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2394–2404, 2003     

The effect of annealing on the crystallization of poly(ethylene terephthalate)/polycarbonate blends

The effect of annealing on the morphology and subsequent crystallization kinetics of poly (ethylene terephthalate)/polycarbonate blends have been investigated using differential scanning calorimetry (DSC), polarized light microscopy, and scanning electron microscopy (SEM). During annealing transesterification and phase coarsening occurred, and the final properties were compromizes between these two competing effects. Initially, the effect of phase separation dominated and the rate of cold crystallization of PET increased. Transesterification, however, became increasingly important and the rate of crystallization decreased progressively until finally the blend completely lost the ability to crystallize. At this stage in the reaction a single glass transition was observed and uniform glassy material observed in the SEM. The maximum crystallinity of the blend achieved on heating showed the same trend in first increasing and then decreasing with annealing time. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2129–2136, 2004     

New super‐tough poly(butylene terephthalate) materials based on compatibilized blends with metallocenic poly(ethylene‐octene) copolymer

New super‐tough poly(butylene terephthalate) (PBT)/poly(ethylene‐octene) copolymer (PEO) blends containing 2 wt% poly(ethylene‐co‐glycidyl methacrylate) (EGMA) as a compatibilizer were obtained by extrusion and injection molding. The blends comprised of an amorphous PBT‐rich phase with some miscibilized EGMA, a pure PEO amorphous phase, and a crystalline PBT phase that was not influenced by the presence of either PEO or EGMA. The blends showed a fine particle size up to 20 wt% PEO content. Super‐tough blends were obtained with PEO contents equal to or higher than 10%. The maximum toughness was very high (above 710 J/m) and was attained with 20% PEO without chemical modification of the commercial components used. Copyright © 2003 John Wiley & Sons, Ltd.     

Thermal degradation of poly(vinyl chloride)/poly(ethylene oxide) blends: Thermogravimetric analysis

Thermal stability of poly(vinyl chloride)/poly(ethylene oxide) (PVC/PEO) blends has been investigated by thermogravimetric analysis (TGA) in dynamic and isothermal heating regime. PVC/PEO blends were prepared by hot-melt extrusion (HME). According to TG analysis, PEO decomposes in one stage, while PVC and PVC/PEO blends in two degradation stages. In order to evaluate the effect of PEO content on the thermal stability of PVC/PEO blends, different criteria were used. It was found that thermal stability of PVC/PEO blends depends on the blend composition. The interactions of blends components with their degradation products were confirmed. By using multiple heating rate kinetics the activation energies of the PVC/PEO blends thermal degradation were calculated by isoconversional integral Flynn–Wall–Ozawa and differential Friedman method. According to dependence of activation energy on degree of conversion the complexity of degradation processes was determined.     

Effect of temperature on the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions

In this work the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions were measured at 283.1–313.1 K. The expansion factor of polymer chain was calculated by use of the intrinsic viscosities data. The thermodynamic parameters of polymer solution (the entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient) were evaluated by temperature dependence of polymer chain expansion factor. The obtained thermodynamic parameters indicate that quality of water was decreased for solutions of poly(ethylene oxide), poly(vinyl pyrrolidone) and poly(ethylene oxide)/poly(vinyl pyrrolidone) blends by increasing temperature. Compatibility of poly(ethylene oxide)/poly(vinyl pyrrolidone) blends were explained in terms of difference between experimental and ideal intrinsic viscosity and solvent–polymer interaction parameter. The results indicate that the poly(ethylene glycol)/poly(vinyl pyrrolidone) blends were incompatible.     

Phase behavior and crystallization of a poly(ethylene oxide)/cellulose acetate butyrate blend

The phase behavior of a partially miscible blend of poly(ethylene oxide) (PEO) and cellulose acetate butyrate (CAB) and the crystalline microstructure of PEO in the blend were studied with differential scanning calorimetry (DSC), optical microscopy, and synchrotron small‐angle X‐ray scattering (SAXS) methods. PEO/CAB showed a lower critical solution temperature (LCST) of 168 °C at the critical composition of PEO of 60 wt %. All blend compositions showed a single glass‐transition temperature (T_g) when they were prepared at temperatures lower than the LCST. However, with increasing CAB content, T_g of the blend changed abruptly at 70 wt % CAB; that is, a cusp existed. Below 70 wt % CAB, the change in T_g with blend composition was predicted by the Brau–Kovacs equation, whereas this change was predicted by the Fox equation at higher CAB contents. A gradual but small depression of the melting point of PEO in the blend with an increasing amount of CAB suggested that the PEO/CAB blends exhibited a weak intermolecular interaction. From DSC and SAXS experiments, it was found that amorphous CAB was incorporated into the interlamellar region of PEO for blends with less than 20 wt % CAB, whereas it was segregated to exist in the interfibrillar region in PEO for other blends with larger amounts of CAB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1673–1681, 2002     

Thermal oxidation of blends of poly(ethylene oxide) and poly(methyl methacrylate)

Thermal oxidation of poly(ethylene oxide) (PEO) and its blends with poly(methyl methacrylate) (PMMA) were studied using oxygen uptake measurements. The rates of oxidation and maximum oxygen uptake contents were reduced as the content of PMMA was increased in the blends. The results were indicative of a stabilizing effect by PMMA on the oxidation of PEO. The oxidation reaction at 140°C was stopped at various stages and PMMA was separated from PEO and its molecular weights were measured by gel permeation chromatography (GPC). The decrease in the number-average molecular weight of PMMA was larger as the content of PEO increased in the blends. The visual appearance of the films suggested that phase separation did not occur after thermal oxidation. The activation energy for the rates of oxidation in the blends was slightly increased compared to pure PEO. © 1992 John Wiley & Sons, Inc.     

Phase behavior,crystallization, and morphology in thermosetting blends of a biodegradable poly(ethylene glycol)‐type epoxy resin and poly(ϵ‐caprolactone)

Thermosetting blends of a biodegradable poly(ethylene glycol)‐type epoxy resin (PEG‐ER) and poly(?‐caprolactone) (PCL) were prepared via an in situ curing reaction of poly(ethylene glycol) diglycidyl ether (PEGDGE) and maleic anhydride (MAH) in the presence of PCL. The miscibility, phase behavior, crystallization, and morphology of these blends were investigated. The uncured PCL/PEGDGE blends were miscible, mainly because of the entropic contribution, as the molecular weight of PEGDGE was very low. The crystallization and melting behavior of both PCL and the poly(ethylene glycol) (PEG) segment of PEGDGE were less affected in the uncured PCL/PEGDGE blends because of the very close glass‐transition temperatures of PCL and PEGDGE. However, the cured PCL/PEG‐ER blends were immiscible and exhibited two separate glass transitions, as revealed by differential scanning calorimetry and dynamic mechanical analysis. There existed two phases in the cured PCL/PEG‐ER blends, that is, a PCL‐rich phase and a PEG‐ER crosslinked phase composed of an MAH‐cured PEGDGE network. The crystallization of PCL was slightly enhanced in the cured blends because of the phase‐separated nature; meanwhile, the PEG segment was highly restricted in the crosslinked network and was noncrystallizable in the cured blends. The phase structure and morphology of the cured PCL/PEG‐ER blends were examined with scanning electron microscopy; a variety of phase morphologies were observed that depended on the blend composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2833–2843, 2004     

Lamellar‐level morphology induced by combined crystallization and liquid–liquid demixing in a poly(ethylene terephthalate)/poly(ethylene‐2,6‐naphthalate) blend

The lamellar‐level morphology of an extruded poly(ethylene terephthalate) (PET)/poly(ethylene‐2,6‐naphthalate) (PEN) blend was investigated with small‐angle X‐ray scattering (SAXS). Measurements were made as a function of the annealing time in the melt and the crystallization temperature. The characteristic morphological parameters at the lamellar level were determined by correlation function analysis of the SAXS data. At a low crystallization temperature of 120 °C, the increased amorphous layer thickness was identified in the blend, indicating that some PEN was incorporated into the interlamellar regions of PET during crystallization. The blend also showed a larger lamellar thickness than pure PET. A reason for the increase in the lamellar thickness might be that the formation of thinner lamellar stacks by secondary crystallization was significantly restricted because of the increased glass‐transition temperature. At high crystallization temperatures above 200 °C, the diffusion rates of noncrystallizable components were faster than the growth rates of crystals, with most of the noncrystallizable components escaping from the lamellar stacks. As a result, the blend showed an interfibrillar or interspherulitic morphology. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 317–324, 2002     

Non-isothermal crystallization kinetics of poly(trimethylene terephthalate)/poly(ethylene 2,6-naphthalate) blends

The glass-transition temperature and non-isothermal crystallization of poly(trimethylene terephthalate)/poly(ethylene 2,6-naphthalate) (PTT/PEN) blends were investigated by using differential scanning calorimeter (DSC). The results suggested that the binary blends showed different crystallization and melting behaviors due to their different component of PTT and PEN. All of the samples exhibited a single glass-transition temperature, indicating that the component PTT and PEN were miscible in amorphous phase. The value of T_g predicted well by Gordon-Taylor equation decreased gradually with increasing of PTT content. The commonly used Avrami equation modified by Jeziorny, Ozawa theory and the method developed by Mo were used, respectively, to fit the primary stage of non-isothermal crystallization. The kinetic parameters suggested that the PTT content improved the crystallization of PEN in the binary blend. The crystallization growth dimension, crystallization rate and the degree of crystallinity of the blends were increased with the increasing content of PTT. The effective activation energy calculated by the advanced iso-conversional method developed by Vyazovkin also concluded that the value of E_a depended not only on the system but also on temperature, that is, the binary blend with more PTT component had higher crystallization ability and the crystallization ability is increased with increasing temperature. The kinetic parameters U^* and K_g were also determined, respectively, by the Hoffman-Lauritzen theory.     

Reaction to fire of recycled poly(ethylene terephthalate)/polycarbonate blends

In the present paper, we study the effect of both morphology and compatibilization on the reaction to fire of blends of recycled poly(ethylene terephthalate) (PETr) with recycled polycarbonate (PCr). It is shown that while the flame retardancy of blends containing less than 50% w/w of PCr increases almost linearly with PCr content, blends containing more than 50% w/w of PCr react to fire like pure PCr. This change of reaction to fire correlates with the formation of a continuous PCr phase in the blend.The compatibilization of the blend by a trans-esterification reaction leading to the formation of copolymers at the interface decreases the overall fire performances due to PETr chain breaking as a side effect which results in a strong decrease of blend viscosity and of the temperature at which mass loss begins.     

Poly (caprolactone)/poly (ethylene glycol) pervaporation blend membranes: Synthesis,characterization, and performance

Poly (caprolactone) membranes with addition of different poly (ethylene glycol) concentrations were prepared for separation of water/isopropanol azeotropic mixture by pervaporation process. Different characterization tests including Fourier transform infrared, scanning electron microscopy, water contact angle, and thermogravimetric analysis were carried out on the prepared membranes. In addition, the effect of poly (ethylene glycol) PEG content on the swelling degree and the performance of the prepared membranes in pervaporation process were investigated. According to the obtained results, all the membranes were water selective and the blend membrane containing 3 wt% PEG exhibited the best pervaporation performance with a water flux of 0.517 kg/m² hour and separation factor of 1642 at the ambient temperature. Hydrophilicity improvement of the blend membranes was confirmed by constant decrease in water contact angle of the membranes as PEG content increased in the casting solution. Scanning electron microscopy cross‐sectional images indicated that the blend membranes containing PEG had a closed cellular structure. Furthermore, mechanical and thermal properties of the membranes decreased by adding PEG.