Miscibility and crystallisation behaviour of poly(ethylene terephthalate)/polycarbonate blends

Poly(ethylene terephthalate)/polycarbonate blends were produced in a twin-screw extruder with and without added transesterification catalyst, lanthanum acetyl acetonate. The miscibility of the blends was studied from their crystallisation behaviour and variation in glass transition temperature with composition using differential scanning calorimetry, scanning electron microscopy and change in mechanical properties. The blends prepared without the catalyst showed completely immiscible over all compositions, while those prepared in the presence of the catalyst showed some limited miscible. The presence of PC inhibited the crystallisation of PET but this was much greater in the blends prepared in the presence of catalyst suggesting that some reaction had taken place between the two polyesters. The tensile properties showed little differences between the two types of blends.     

Morphological origin of super toughness in poly(ethylene terephthalate)/polyethylene blends

A compatibilization strategy for poly(ethylene terephthalate) (PET) and polyethylene (PE) blends to achieve high toughness is described. Maleic anhydride functionalized styrene–ethylene–butylene–styrene (MA-g-SEBS) block copolymer at 20 pph was found to produce an intricate multidomain morphology in which the two major components (50% PE, 50% PET) and the compatibilizer coexist on a hierarchal order. A portion of the PET was dispersed as interconnected rodlike domains oriented along the injection direction. The rest of the PET and the PE constituted beadlike nano domains which served as the matrix. The blend at all these morphological levels responded to deformation in a cooperative fashion giving rise to a super tough material. That is, a blend whose elongation at break (600%) was superior to its two major components (90% for PET and 300% for PE). © 1993 John Wiley & Sons, Inc.     

Annealing of poly(trimethylene terephthalate)/polycarbonate blends

A blend of poly(trimethylene terephthalate) (PTT) and polycarbonate with a weight ratio of 50/50 was studied by means of differential scanning calorimetry (DSC) and dielectric spectroscopy (DS) after melt annealing that enables transesterification. The DSC results show that with increasing the residence time in the melt, the melting temperature and the heat of fusion of PTT crystals decrease. Prolonged thermal treatment at 300 °C gives rise to a copolymer that no longer reveals melting or crystallization. Additional annealing of such samples below the melting temperature of PTT results in restoration of the crystallization ability. The amorphous phase dynamics is studied by means of DS demonstrating that the glass transition relaxations are very sensitive to the crystallinity changes. The random copolymer is characterized by only one α-relaxation indicating a more or less homogeneous amorphous phase. In contrast to this, the physical blend and the block copolymers show two α-relaxation processes attributed to the existence of two amorphous fractions. Analysis of the relaxation process in terms of Vogel–Fucher–Tammann–Hesse model reveals a correlation between the fragility parameter and the extent of trans-reaction. The crystallization kinetics of the blocky copolymer determined from the changes of the dielectric constant with time are discussed and compared with pure PTT.     

The morphology and deformation behavior of poly(butylene terephthalate)/BPA polycarbonate blends

Summary In this communication the results of a series of recent studies of the morphology and deformation behavior of toughened poly(butylene terephthalate) (PBT)/BPA polycarbonate (PC) blends are briefly summarized. Several papers containing a more detailed account are currently in press (1–3). Among the unique morphological features of these blends are the consistent isolation of the core/shell impact modifier (IM) in the PC phase and the crystallization and phase separation of the PBT from the partially miscible PBT/PC melt on slow cooling. DSC studies provide corroborating evidence for melt miscibility of the two resins. The blends deform through a combination of cavitation and shear processes. In all cases cavitation occurs exclusively within the IM particles and is suppressed at higher PC concentrations and elevated temperatures.     

Crystallization of poly(ethylene terephthalate)/polycarbonate blends. I. Unreinforced systems

The crystallization and transition temperatures of poly(ethylene terephthalate) (PET) in blends with polycarbonate (PC) is considered using thermal analysis. Additives typically used in commercial polyester blends, transesterification inhibitor and antioxidant, are found to enhance the crystallization rate of PET. Differential scanning calorimetry (DSC) reveals two glass transition temperatures in PET/PC blends, consistent with an immiscible blend. Optical microscopy observations are also consistent with an immiscible blend. Small shifts observed in the T_g of each component may be due to interactions between the phases. The degree of crystallinity of PET in PET/PC blends is significantly depressed for high PC contents. Also, in blends with PC content greater than 60 wt %, two distinct crystallization exotherms are observed in dynamic crystallization from the melt. The isothermal crystallization kinetics of PET, PET modified with blend additives, and PET in PET/PC blends have been evaluated using DSC and the data analyzed using the Avrami model. The crystallization of PET in these systems is found to deviate from the Avrami prediction in the later stages of crystallization. Isothermal crystallization data are found to superimpose when plotted as a function of time divided by crystallization half-time. A weighted series Avrami model is found to describe the crystallization of PET and PET/PC blends during all stages of crystallization. © 1996 John Wiley & Sons, Inc.     

Properties of poly(ethylene terephthalate)/poly(ethylene naphthalate) blends

Blends composed of poly(ethylene terephthalate) (PET) as the majority component and poly(ethylene naphthalate)(PEN) as the minority component were melt-mixed in a single screw extruder at various PET/PEN compound ratios. Tensile and flexural test results reveal a good PET/PEN composition dependence, indicating that the compatibility of the blends is effective in a macrodomain. In thermal tests, single transitions for T_g, T_m and T_c (crystallization temperature), respectively, are observed from DSC as well as single T_g from DMA except for 50/50 blends. These results suggests that the compatibility is sufficient down to the submicron level. Moreover, isothermal DSC tests along with Avrami analysis indicate that PET's crystallization is significantly retarded when blended with PEN. Results in this study demonstrate that PEN is a highly promising additive to improve PET's spinnability at high speeds.     

Calorimetric and dielectric study on poly(trimethylene terephthalate)/polycarbonate blends

Poly(trimethylene terephthalate) (PTT)/polycarbonate (PC) blends with different compositions were prepared by melt blending. The miscibility and phase behavior of melt-quenched and cold-crystallized blends were studied using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy. The blends of all compositions display only one glass transition (T _g ) in both states. The melting temperature and the crystallinity of PTT in the blend decrease with increasing PC content. The dielectric results for the melt-quenched blends, for PC content up to 60 wt.%, exhibited two merged relaxation peaks during the heating scan; the lower temperature relaxation peak represent the normal glass-transition (α) relaxation of the mixed amorphous phase and the higher temperature relaxation due to the new-constrained mixed amorphous phase after crystallization. Cold-crystallized blends displayed only one glass transition α-relaxation whose temperatures varied with composition in manner similar to that observed by DSC. The dielectric α-relaxation of cold crystallized blends has been analyzed. Parameters relating to relaxation broadening, dielectric relaxation strength, and activation energy were quantified and were found to be composition dependent. The PTT/PC blends could be considered as two-phase system, a crystalline PTT phase and a mixed amorphous phase consisting of a miscible mixture of the two polymers. However, the crystallinity was only detected for blends containing greater than 40 wt.% PTT.     

Effects of mixing time on phase structure and mechanical properties of poly(ethylene terephthalate)/ polycarbonate blends

The effects of interchange reactions on the solid‐state structure and mechanical properties of a 70/30 poly(ethylene terephthalate) (PET)/bisphenol A polycarbonate (PC) blend were studied. Increasing reaction levels were obtained by means of lower screw speeds in the extruder. The progressive production of copolymers with the reaction time increased the amount of each component in the other phase. The concomitant degradation of PET led to a maximum in ductility and tensile and impact strengths whereas the modulus of elasticity and the yield stress were held constant. The maximum in properties took place at a reaction time close to 2.6 min; at longer reaction times the negative effect of degradation began to overcome the positive effect of the interchange reactions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 121–127, 2001     

Dynamic rheological behavior and morphology of poly(trimethylene terephthalate)/poly(ethylene octene) copolymer blends

The dynamic rheology and morphology of poly(trimethylene terephthalate) and maleic anhydride grafted poly(ethylene octene) composites were investigated. A specific viscoelastic phenomenon, that is, a second plateau, appeared at low frequencies and exhibited a certain dependence on the content of elastomer particles and the temperature. This phenomenon was attributed to the formation of an aggregation structure of rubber particles. The analyses of the dynamic viscoelastic functions suggested that the heterogeneity of the composites was enhanced as the particle content or temperature increased. The microstructural observation by scanning electron microscopy confirmed that maleic anhydride could react with the end groups of poly(trimethylene terephthalate) to form a stable interfacial layer and result in a smaller dispersed‐phase particle size due to the reduced interface tension. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Molecular orientation and relaxation in poly(butylene terephthalate)/polycarbonate blends

Rheo-optical Fourier-transform infrared (FTIR) spectroscopy is based on the simultaneous acquisition of stress-strain data and FTIR spectra on-line to the mechanical treatment of polymers and is frequently applied for the characterization of transient structural changes during deformation and stress-relaxation. In the present communication, this technique has been employed in order to investigate the distribution of molecular orientation and its relaxation in uniaxially drawn solution-cast films of semicrystalline partial miscible blends of poly(butylene terephthalate) (PBT) with polycarbonate (PC) containing 10, 30 and 50 wt% PC. The uniaxial deformation of these blend films having a PBT-crystallinity degree ranging from 31 to 12%, in unstretched blends, leads to a appreciable high segmental orientation for the crystalline PBT due to a structural transformation from lamellae to microfibrils. The formation of this fibrillar structure is attributed to non-reversibility of an extended phase with all-trans conformational sequence of the aliphatic segments of PBT, occurring during elongation. The rate of relaxation of this conformational transition, however, increases with increasing amorphous content in the blends. Also it is observed that even with increasing amorphous content in the PBT/PC blends the crystalline PBT shows significant orientation. In such cases, apart from the few lamellae which transform to microfibrils, it is suggested that a stress induced transformation of PBT chains in amorphous PBT-component to irreversible all-trans extended crystalline form also contributes to PBT crystalline orientation. In contrast with this high crystalline orientation, the amorphous PBT located in the interlamellar regions inside the PBT-spherulites show a lower orientation in blends as compared in pure PBT.On the other hand, an overall segmental orientation of PC chains in blends is of lower order which is attributed mainly to low stretching temperature compared to T_g of pure PC. The results are discussed in terms of the resulting spherulitic morphology and the temporary network formed by the elongated PBT and PC chains inside the interlamellar regions, in blends.     

Deformation and morphology development of poly(ethylene terephthalate)/polyethylene and polycarbonate/polyethylene blends with high interfacial contact during elongation

Immiscible blends of poly(ethylene terephthalate) (PET)/polyethylene (PE) and polycarbonate (PC)/PE were examined to study the influence of the high interfacial contact (pseudo‐adhesion) on the mechanical properties and the morphology developed during elongation. The high interfacial contact resulted from the contraction difference of the two polymers during cooling from the processing temperature to room temperature. As a result of the pseudo‐adhesion, the tensile strength and modulus of the PET/PE and PC/PE blends increased steadily with the increase of PET and PC concentration. In PC/PE blends, numerous PC microfibers were formed in‐situ, while in PET/PE blends, slippage took place between the PET particles and the matrix. Moreover, the macroscopic morphology development of both blends upon elongation was quite different. For PET/PE blend, necking was initiated at one point close to the non‐gate end of the specimen, and then propagated uniformly from this point. For the PC/PE blend, necking‐initating sites and propagation were irregular, and consequently the whole tested zone was deformed. The recoil of partially elongated specimens indicated that the recoverability of the PC/PE blend is higher than that of the PET/PE blend. Polym. Eng. Sci. 44:1561–1570, 2004. © 2004 Society of Plastics Engineers.     

Miscibility and melting behavior of poly(ethylene terephthalate)/poly(trimethylene terephthalate) blends

The miscibility and melting behavior of binary crystalline blends of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) have been investigated with differential scanning calorimetry and scanning electron microscope. The blends exhibit a single composition‐dependent glass transition temperature (T_g) and the measured T_g fit well with the predicted T_g value by the Fox equation and Gordon‐Taylor equation. In addition to that, a single composition‐dependent cold crystallization temperature (T_cc) value can be observed and it decreases nearly linearly with the low T_g component, PTT, which can also be taken as a valid supportive evidence for miscibility. The SEM graphs showed complete homogeneity in the fractured surfaces of the quenched PET/PTT blends, which provided morphology evidence of a total miscibility of PET/PTT blend in amorphous state at all compositions. The polymer–polymer interaction parameter, χ₁₂, calculated from equilibrium melting temperature depression of the PET component was ?0.1634, revealing miscibility of PET/PTT blends in the melting state. The melting crystallization temperature (T_mc) of the blends decreased with an increase of the minor component and the 50/50 sample showed the lowest T_mc value, which is also related to its miscible nature in the melting state. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

High impact poly(lactic acid)/poly(ethylene octene) blends prepared by reactive blending

Poly(ethylene octene) grafted with glycidyl methacrylate (POE‐g‐GMA) was prepared and used to toughen poly (lactic acid) (PLA) via reactive blending. It was found that the notched Izod impact strength of PLA/POE‐g‐GMA blends improved dramatically when the content of elastomer was higher than 10 wt%. Reactive compatibilization between PLA and POE‐g‐GMA were studied by Fourier transform infrared spectroscopy (FTIR) and “Molau test,” the results showed the end carboxyl groups of PLA reacted with the epoxide groups of POE‐g‐GMA during blending. This considerably improved the compatibilization, leading to better wetting of the dispersed phase by the PLA matrix and finer dispersed POE‐g‐GMA particles with narrow distribution. Moreover, the critical interparticle distance (L_c) of the dispersed domains for PLA/POE‐g‐GMA blends system at room temperature was also identified. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Partial miscibility of poly(butylene terephthalate)/BPA polycarbonate melt blends

Summary Differential scanning calorimetry (DSC) measurements have been carried out on a number of poly(butylene terephthalate) (PBT)/BPA polycarbonate (PC) blends prepared by melt compounding and solution casting from hexafluoroisopropanol (HFIP). The results clearly indicate that appreciable mixing of the two polymers takes place in the melt phase whereas complete separation is observed in cast films. The failure of the casting procedure to mimic the melt blending results is related in part to liquid-liquid phase separation and to crystallization of both polymers from the casting solvent.     

Miscibility of poly(ether imide)/poly(ethylene terephthalate) blends

Summary Miscibility of blends of poly(ether imide) (PEI) and poly(ethylene terephthalate) (PET) were studied by differential scanning calorimetry (DSC). Single and composition-dependent T_g's are observed over the entire composition range, indicating that the blends are miscible in the amorphous region. The overall crystallization rate of PET in the blends decreased with increasing the PEI content. The interaction energy density B, which was calculated from the melting point depression of the blends using Nishi-Wang equation, was-5.5 cal/cm³.     

Properties of ultrasound-assisted blends of poly(ethylene terephthalate) with polycarbonate

This study investigated the effect of ultrasound irradiation on blends of polyethylene terephtalate (PET) and polycarbonate (PC). The blends of PET/PC were prepared by a twin-screw extruder with an attached ultrasonic device. Thermal, rheological, and mechanical properties and morphology of the blends with and without sonication have been analyzed. The two distinct T_gs of the blends measured by DSC showed immiscibility over all compositions. The theoretical PET content that is miscible in PC-rich phase calculated using the Fox equation showed that ultrasonic waves made the blends more miscible. From mechanical test results, when sonication was not applied, the 20/80 blend was the most miscible composition. At that composition, the impact strength of sonicated blend was surprisingly high. It was believed to be due to the enhancement of compatibility by a reaction such as transesterification. The results from the morphology of the 20/80 sonicated blend were in agreement with DSC and impact test results.     

Miscibility and crystallization kinetics of poly(trimethylene terephthalate)/amorphous poly(ethylene terephthalate) blends

The miscibility and crystallization kinetics of the blends of poly(trimethylene terephthalate) (PTT) and amorphous poly(ethylene terephthalate) (aPET) have been investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that PTT/aPET blends were miscible in the melt. Thus, the single glass transition temperature (T_g) of the blends within the whole composition range and the retardation of crystallization kinetics of PTT in blends suggested that PTT and aPET were totally miscible. The nucleation density of PTT spherulites, the spherulitic growth, and overall crystallization rates were depressed upon blending with aPET. The depression in nucleation density of PTT spherulites could be attributed to the equilibrium melting point depression, while the depression in the spherulitic growth and overall crystallization rates could be mainly attributed to the reduction of PTT chain mobility and dilution of PTT upon mixing with aPET. The underlying nucleation mechanism and growth geometry of PTT crystals were not affected by blending, from the results of Avrami analysis. POLYM. ENG. SCI., 47:2005–2011, 2007. © 2007 Society of Plastics Engineers     

Crystallization and spherulitic growth kinetics of poly(trimethylene terephthalate)/polycarbonate blends

The macroscopic and microscopic melt‐crystallization kinetics of poly(trimethylene terphthalate) (PTT)/polycarbonate (PC) blends have been measured by differential scanning calorimetry (DSC), and optical microscopy (OM). The results are analyzed in terms of the Avrami equation and the Hoffman–Lauritzen crystallization theory (HL model). Blending with PC did not change the crystallization mechanism of PTT, but reduced the crystallization rate compared with that of neat PTT at the same crystallization temperature. The crystallization rate decreased with increasing crystallization temperature. The spherulitic morphology of PTT was influenced apparently by the crystallization temperature and by the addition of PC. X‐ray diffraction shows no change in the unit cell dimension of PTT was observed after blending. Through the HL theory, the classical regime II→III transition was detected for the neat PTT and the blends. The nucleation parameter (K_g), the fold‐surface free energy (σ_e), and the work of chain folding (q) were calculated. Blending with PC decreased all the aforementioned parameters compared with those of neat PTT. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

PEN/PET共混物结晶行为研究

用差示扫描量热法(DSC)研究了不同共混比例PEN/PET共混物的熔体结晶行为,并进行了等温结晶动力学测定。结果表明:随着两种组分向中间比例(50/50)靠近,共混物的熔融温度越低,结晶速率也越慢。