Blends of poly(ethylene terephthalate) and poly(butylene terephthalate)

Commercial grade poly(ethylene terephthalate), (PET, intrinsic viscosity = 0.80 dL/g) and poly(butylene terephthalate), (PBT, intrinsic viscosity = 1.00 dL/g) were melt blended over the entire composition range using a counterrotating twin‐screw extruder. The mechanical, thermal, electrical, and rheological properties of the blends were studied. All of the blends showed higher impact properties than that of PET or PBT. The 50:50 blend composition exhibited the highest impact value. Other mechanical properties also showed similar trends for blends of this composition. The addition of PBT increased the processability of PET. Differential scanning calorimetry data showed the presence of both phases. For all blends, only a single glass‐transition temperature was observed. The melting characteristics of one phase were influenced by the presence of the other. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 75–82, 2005     

Compatible and crystallization properties of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) blends

Differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis (DMA) properties of poly(lactic acid)/ poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) specimens suggest that only small amounts of poor PLA and/or PBAT crystals are present in their corresponding melt crystallized specimens. In fact, the percentage crystallinity, peak melting temperature and onset re‐crystallization temperature values of PLA/PBAT specimens reduce gradually as their PBAT contents increase. However, the glass transition temperatures of PLA molecules found by DSC and DMA analysis reduce to the minimum value as the PBAT contents of PLA_xPBAT_y specimens reach 2.5 wt %. Further morphological and DMA analysis of PLA/PBAT specimens reveal that PBAT molecules are miscible with PLA molecules at PBAT contents equal to or less than 2.5 wt %, since no distinguished phase‐separated PBAT droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLA/PBAT specimens, respectively. In contrast to PLA, the PBAT specimen exhibits highly deformable properties. After blending proper amounts of PBAT in PLA, the inherent brittle deformation behavior of PLA was successfully improved. Possible reasons accounting for these interesting crystallization, compatible and tensile properties of PLA/PBAT specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polymer blends of poly(trimethylene terephthalate) and polystyrene compatibilized by styrene‐glycidyl methacrylate copolymers

The compatibilizing effects of styrene‐glycidyl methacrylate (SG) copolymers with various glycidyl methyacrylate (GMA) contents on immiscible blends of poly(trimethylene terephthalate) (PTT) and polystyrene (PS) were investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and ¹³C‐solid‐state nuclear magnetic resonance (NMR) spectroscopy. The epoxy functional groups in the SG copolymer were able to react with the PTT end groups (? COOH or ? OH) to form SG‐g‐PTT copolymers during melt processing. These in situ–formed graft copolymers tended to reside along the interface to reduce the interfacial tension and to increase the interfacial adhesion. The compatibilized PTT/PS blend possessed a smaller phase domain, higher viscosity, and better tensile properties than did the corresponding uncompatibilized blend. For all compositions, about 5% GMA in SG copolymer was found to be the optimum content to produce the best compatibilization of the blend. This study demonstrated that SG copolymers can be used efficiently in compatibilizing polymer blends of PTT and PS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2247–2252, 2003     

Rheological and thermal properties of blends of modified poly(ethylene terephthalate) with p‐acetoxybenzoic acid and poly(butylene terephthalate)

Blending of thermotropic liquid crystalline polyesters (LCPs) with conventional polymers could result in materials that can be used as an alternative for short fiber‐reinforced thermoplastic composites, because of their low melt viscosity as well as their inherent high stiffness and strength, high use temperature, and excellent chemical resistance and low coefficient of expansion. In most of the blends was used LCP of 40 mol % of poly(ethylene terephthalate) (PET) and 60 mol % of p‐acetoxybenzoic acid (PABA). In this work, blends of several copolyesters having various PABA compositions from 10 to 70 mol % and poly(butylene terephthalate) (PBT) were prepared and their rheological and thermal properties were investigated. For convenience, the copolyesters were designated as PETA‐x, where x is the mol % of PABA. It was found that PET‐60 and PET‐70 copolyesters decreased the melt viscosity of PBT in the blends and those PBT/PETA‐60 and PBT/PETA‐70 blends showed different melt viscosity behaviors with the change in shear rate, while blends of PBT and PET‐x having less than 50 mol % of PABA exhibited totally different rheological behaviors. The blends of PBT with PETA‐50, PETA‐60, and PETA‐70 showed the morphology of multiple layers of fibers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1797–1806, 1999     

Miscibilities and rheological properties of poly(butylene succinate)–Poly(butylene terephthalate) blends

An aliphatic/aromatic polyester blend has been dealt with in this study. As an aliphatic polyester, poly(butylene succinate) (PBS) was used, which is thought to possess biodegradability, but it is relatively expensive. It has been blended with poly(butylene terephthalate) (PBT) in order to obtain a biodegradable blend with better mechanical properties and lower cost. The miscibilities of PBS–PBT blends were examined not only from the changes of T_g but also from log G′–log G" plots. Dynamic mechanical thermal analyzer (DMTA) was an appropriate, sensitive method to obtain the glass transitions properly. Thermal stabilities of PBS and PBT were also verified at the temperature of 240°C. A transesterification reaction between two polyesters at 240°C was hardly detectable so that it did not affect the miscibilities and properties of the blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 945–951, 1999     

Toughening of recycled poly(ethylene terephthalate) with clay‐compatibilized rubber phase

Recycled bottle‐grade PET (rPET) is a valuable low‐cost polymeric material. However, enhancement of its mechanical properties is necessary for many applications. This work is focused on clay‐reinforced/compatibilized rPET/elastomer system. Although the clay addition to various rPET/elastomer blends caused a remarkable refinement of structure, more pronounced for clay with less polar modification, both a gain or decrease in strength and toughness occurred, whereas an increase in modulus was found for all systems. This is a consequence of simultaneous complex affecting many parameters by clay and both antagonistic and synergistic combination of respective effects. Best results were found for low contents of EPR rubber and its preblending with clay. The presented results indicate that a suitable combination of nanosilicates with rubber can lead to rPET materials with fairly enhanced properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structure and mechanical properties of poly(sulfone of bisphenol A)/poly(butylene terephthalate) blends

Blends of poly(sulfone of bisphenol A) (PSU) with poly(butylene terephthalate) (PBT) were obtained by direct injection moulding across the composition range. The two components of the blends reacted slightly in the melt state, producing linear copolymers. The slight changes observed in the two glass transition temperatures indicate that the copolymers were present in the two amorphous phases of the blends. The observed reactions and the high viscosity of the matrix of the PSU‐rich compositions led to a very fine morphology which could not be attained in the PBT‐rich compositions due to the low viscosity of the matrix and the direct injection moulding procedure used. This procedure is fast and economically advantageous, but leads to poor mixing. The different morphologies influenced neither the modulus nor the yield stress, which tended to follow the rule of mixtures. However, the low fracture properties of the PBT‐rich compositions contrasted with the ductility behaviour, and even the impact strength of the PSU‐rich blends, which also tended to be proportional to the blend composition. Copyright © 2004 Society of Chemical Industry     

Sequence analysis of poly(ethylene terephthalate)/poly(butylene terephthalate) copolymer prepared by ester-interchange reactions

The molecular structure of the copolyester formed through the interchange reaction in poly(ethylene terephthalate)/poly(butylene terephthalate) blends was investigated with ¹³C-NMR spectroscopy. The molar fractions of heterolinkage triads in the copolyesters were lower than the values calculated by Bernoullian statistics; this indicates that the sequence of heterolinkages was far from a random distribution at the initial stage of the interchange reaction. However, the randomness increased and the number-average sequence length decreased with reaction time. The solubility of the blend decreased with increasing sequence length, resulting from the formation of block copolymers with long sequence lengths at the initial stage of the interchange reaction. The solubility of the copolyester formed by a dibutyltin dilaurate (DBTDL)-catalyzed reaction was higher than that of the copolyester formed by a titanium tetrabutoxide-catalyzed reaction; this is related to the fact that alcoholysis prevailed in the DBTDL-catalyzed reaction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 159–168, 2001     

Influence of the degree of grafting on the morphology and mechanical properties of blends of poly(butylene terephthalate) and glycidyl methacrylate grafted poly(ethylene‐co‐propylene) (EPR)

Poly(ethylene‐co‐propylene) (EPR) was functionalized to varying degrees with glycidyl methacrylate (GMA) by melt grafting processes. The EPR‐graft‐GMA elastomers were used to toughen poly(butylene terephthalate) (PBT). Results showed that the grafting degree strongly influenced the morphology and mechanical properties of PBT/EPR‐graft‐GMA blends. Compatibilization reactions between the carboxyl and/or hydroxyl of PBT and epoxy groups of EPR‐graft‐GMA induced smaller dispersed phase sizes and uniform dispersed phase distributions. However, higher degrees of grafting (>1.3) and dispersed phase contents (>10 wt%) led to higher viscosities and severe crosslinking reactions in PBT/EPR‐graft‐GMA blends, resulting in larger dispersed domains of PBT blends. Consistent with the change in morphology, the impact strength of the PBT blends increased with the increase in EPR‐graft‐GMA degrees of grafting for the same dispersion phase content when the degree of grafting was below 1.8. However, PBT/EPR‐graft‐GMA1.8 displayed much lower impact strength in the ductile region than a comparable PBT/EPR‐graft‐GMA1.3 blend (1.3 indicates degree of grafting). Morphology and mechanical results showed that EPR‐graft‐GMA 1.3 was more suitable in improving the toughness of PBT. SEM results showed that the shear yielding properties of the PBT matrix and cavitation of rubber particles were major toughening mechanisms. Copyright © 2006 Society of Chemical Industry     

Further studies of polycarbonate-poly(butylene terephthalate) blends

The mechanical properties (tensile strength, low temperature falling weight impact strength) of XENOY CL-100 (a blend of polycarbonate and polybutylene terephthalate) have been studied. This blend is comprised of tough components and the property combinations that result may be useful for certain applications. The hydrolysis resistance of the blend in deionised water at 40°C has been studied. After 30 weeks it did not lose its tensile strength, but subsequently it did lose 50% of the low temperature (?70°C) falling weight impact strength. If the ?70°C low temperature toughness is an important quality, this should be taken into account. However, the low temperature (?70°C) falling weight impact strength of pure polycarbonate and of pure poly(butylene terephthalate) is very low, whilst XENOY CL-100 is still tough material, even after 30 weeks immersion at 40°C. Further study of the composition of XENOY CL-100 showed that this blend is composed of polycarbonate. poly(butylene terephthalate) and crosslinked acrylic rubber; traces of titanium-catalyst residue for the poly(butylene terephthalate) polymeristaion and black dye have also been found.     

Synthesis and characterization of poly[(butylene succinate)‐co‐(butylene terephthalate)]‐b‐poly(tetramethylene glycol) segmented block copolymer

Polyester‐polyether segmented block copolymers of poly[(butylene succinate)‐co‐poly(butylene terephthalate)] (PBS–PBT) and poly(tetramethylene glycol) (PTMG) (M_n = 2000) with various compositions were synthesized. PBT content in the PBS was adjusted to ca. 5 mol %. Their thermal and mechanical properties were investigated. In the case of copolymer, the melting point of the PBS–PBT control was 107.8°C, and the melting point of the copolymer containing 70 wt % of PTMG was 70.1°C. Crystallinity of soft segment was 5 ∼ 17%, and that of hard segment was 42 ∼ 59%. The breaking stress of the PBS–PTMG control was 47 MPa but it decreased with increasing PTMG content. In the case of copolymer containing 70 wt % of PTMG, breaking stress was 36 MPa. Contrary to the decreasing breaking stress, breaking strain increased from 300% for PBS–PBT control to 900% for a copolymer containing 70 wt % of PTMG. The shape recovery ratios of the copolymer containing 70 wt % PTMG were almost twice of those of copolymers containing 40 wt % PTMG. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2067–2075, 2001     

Preparation and thermal behavior of random poly(butylene terephthalate/azelate) copolyesters

Poly(butylene terephthalate), poly(butylene azelate), and poly(butylene terephthalate/butylene azelate) random copolymers of various compositions were synthesized in bulk using the well‐known two‐stage polycondensation procedure, and characterized in terms of chemical structure and molecular weight. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. As far as the thermal stability is concerned, it was found to be rather similar for all copolymers and homopolymers investigated. All the copolymers were found to be partially crystalline, and the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of melting temperature with respect to pure homopolymers. Flory's equation was found to describe the T_m–composition data and permitted to calculate the melting temperatures (T^°_m ) and the heats of fusion (ΔH_u) of both the completely crystalline homopolymers. Owing to the high crystallization rate, the glass transition was observable only for the copolymers containing from 30 to 70 mol % of the terephthalate units; even though the samples cannot be frozen in a completely amorphous state, the data obtained confirmed that the introduction of the aromatic units gave rise to an increase of T_g, due to a chain stiffening. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2694–2702, 1999     

Crystallization kinetics of poly(1,4‐butylene‐co‐ethylene terephthalate)

The crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and their copolymers poly(1,4‐butylene‐co‐ethylene terephthalate) (PBET) containing 70/30, 65/35 and 60/40 molar ratios of 1,4‐butanediol/ethylene glycol were investigated using differential scanning calorimetry (DSC) at crystallization temperatures (T_c) which were 35–90 °C below equilibrium melting temperature . Although these copolymers contain both monomers in high proportion, DSC data revealed for copolymer crystallization behaviour. The reason for such copolymers being able to crystallize could be due to the similar chemical structures of 1,4‐butanediol and ethylene glycol. DSC results for isothermal crystallization revealed that random copolymers had a lower degree of crystallinity and lower crystallite growth rate than those of homopolymers. DSC heating scans, after completion of isothermal crystallization, showed triple melting endotherms for all these polyesters, similar to those of other polymers as reported in the literature. The crystallization isotherms followed the Avrami equation with an exponent n of 2–2.5 for PET and 2.5–3.0 for PBT and PBETs. Analyses of the Lauritzen–Hoffman equation for DSC isothermal crystallization data revealed that PBT and PET had higher growth rate constant G_o, and nucleation constant K_g than those of PBET copolymers. © 2001 Society of Chemical Industry     

Chain extension of poly(butylene terephthalate) by reactive extrusion

The chain extension reaction in poly(butylene terephthalate) (PBT) melt was studied in detail. A high‐reactivity diepoxy, diglycidyl tetrahydrophthalate, was used as a chain extender that can react with the hydroxyl and carboxyl end groups of PBT at a very fast reaction rate and a relatively high temperature. A Haake mixer 600 was used to record the torque during the chain extension reaction. The data show that this chain extension reaction could be completed within 2 to 3 min at temperatures above 250°C, and the reaction time decreased very fast with an increase in the temperature. Shear rate also had some effects on the reaction rate. The effect of the diepoxy chain extender on the flowability, thermal stability, and mechanical properties of PBT were investigated. The melt flow index (MFI) of the chain‐extended PBT dramatically decreased as the diepoxy was added to PBT. In addition, the notched Izod impact strength and elongation‐at‐break of the chain‐extended PBT also increased. The chain‐extended PBT is more stable thermally. Compared with the conventional solid post‐polycondensation method, this approach is simpler and cheaper to obtain high‐molecular‐weight PBT resins. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1827–1834, 1999     

Improvement of compatibility of poly(ethylene terephthalate) and poly(ethylene octene) blends by γ‐irradiation

Blends of poly(ethylene terephthalate) (PET) and poly(ethylene octene) (POE) were prepared by melt blending with various amounts of trimethylolpropane triacylate (TMPTA). The mechanical properties, phase morphologies, and gel fractions at various absorbed doses of γ‐irradiation have been investigated. It was found that the toughness of blends was enhanced effectively after irradiation as well as the tensile properties. The elongation at break for all studied PET/POE blends (POE being up to 15 wt %) with 2 wt % TMPTA reached 250–400% at most absorbed doses of γ‐irradiation, approximately 50–80 times of those of untreated PET/POE blends. The impact strength of PET/POE (85/15 wt/wt) blends with 2 wt % TMPTA irradiated with as little as 30 kGy absorbed dose exceeded 17 kJ/m², being approximately 3.4 times of those of untreated blends. The improvement of the mechanical properties was supported by the morphology changes. Scanning electron microscope images of fracture surfaces showed a smaller dispersed phase and more indistinct inter‐phase boundaries in the irradiated blends. This indicates increased compatibility of PET and POE in the PET/POE blends. The changes of the morphologies and the enhancement of the mechanical properties were ascribed to the enhanced inter‐phase boundaries by the formation of complex graft structures confirmed by the results of the gelation extraction and Fourier Transform Infrared analyses. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A constitutive law for poly(butylene terephthalate) nanofibers mats

A three‐dimensional structural constitutive equation is proposed to describe the mechanical properties of poly(butylene terephthalate) nanofibers mats. The model is formulated under the assumption that the mechanical response of the fibrous mat is determined by the individual fibers. The inelasticity, which has been observed when subjecting the fibrous mat to tensile tests, is assumed to be due to the gradual breakage of linear elastic fibers. The constitutive relation also takes the material anisotropy associated with the fibers' architecture into account. Uniaxial experimental data were used to assess the proposed model. The results demonstrate that the model is well suited to reproduce the typical tensile behavior of the fibrous mat. In agreement with the empirical observations, the model predicts that almost all the fibers fail when the poly(butylene terephthalate) fibrous mat sample breaks. Nevertheless, multiaxial stress–strain data and quantification of the fibers' orientation are required to completely validate the constitutive law. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5280–5283, 2006     

Mechanical properties in torsion for poly(butylene terephthalate) and a poly(ether ester) based on poly(ethylene glycol) and poly(butylene terephthalate)

The torsional behavior of poly(ether ester) (PEE) thermoplastic elastomer, based on poly(ethylene glycol) (PEG) and poly(butylene terephthalate) (PBT) was studied and compared with that of PBT itself. Two types of experiments were performed: (1) stress relaxation in torsion, and (2) measurement of intermittent couple-twist responses. It was shown that the relaxation of the torsional couple M could be represented as a sum of several exponential terms in the time, rather than as a simple exponential function. This sum might be called a Prony series on the analogy of the usual stress relaxation which occurs after stretching a sample to a certain deformation and holding it constant. The intermittent couple-twist experiments were carried out by analogy with similar experiments in elongation. For PEE the couple rises steadily with the twist, whereas for PBT it rises abruptly and remains constant within the experimental error for high twists. The residual twist, however, showed a similar trend for both PEE and PBT. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 495–502, 1998     

Melt characteristics,mechanical, and thermal properties of blown film from modified blends of poly(butylene adipate‐co‐terephthalate) and poly(lactide)

Blown films from poly(butylene adipate‐co‐terephthalate) and poly(lactide) (PLA) blends were investigated. The blends were prepared in a twin‐screw extruder, in the presence of small amounts of dicumyl peroxide (DCP). The influence of DCP concentration on film blowing, rheological, mechanical, and thermal properties of the blends is reported in this article. Rheological results showed a marked increase in polymer melt strength and elasticity with the addition of DCP. As a consequence, the film homogeneity and the stability of the bubble were improved. The modified blend films, compared with the unmodified blend, showed an improvement in tensile strength and modulus with a slight loss in elongation. Fourier transform infrared and gel results revealed that chain scission and branching were more significant than crosslinking when the DCP loadings in the blends were not higher than 0.7%. A reduction in melt temperatures of PLA was observed due to difficulty in chain crystallization. The concentrations of DCP strongly affected the melting temperatures but had an insignificant effect on the decomposition behavior of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Critical inter-particle distance dependence and super-toughness in poly(butylene terephthalate)/grafted poly(ethylene-octene) copolymer blends by means of polyarylate addition

New super-tough poly(butylene terephthalate) (PBT) materials were obtained modifying with 10 wt% polyarylate (PAr) a PBT/maleic anhydride grafted poly(ethylene-octene) copolymer (mPEO) blend with mPEO contents from 0 to 30 wt%. PAr was fully miscible in the PBT phase. The presence of mPEO did not influence either the nature or the crystallinity of the PBT-PAr matrix. The decrease in interfacial tension and particle size upon grafting of PEO, indicated that compatibilization took place. The maximum toughness obtained was very high (impact strength more than twenty-fold that of the PBT-PAr matrix). Moreover, it was attained with only 7.5% PEO maleinized at 0.63%, and was accomplished by an increase in stiffness of the blends. The successful modification of the matrix consolidates this method as a new one to improve impact toughness. The critical inter-particle distance (τ_c) appears as the parameter that control super-toughness in these blends, and it is proposed to depend on adhesion measured by means of the interfacial tension.