Effects of co‐hard segments on the microstructure and properties thermoplastic poly(ether ester) elastomers

A thermoplastic poly(ether ester) elastomer (TPEE) is composed of polyester hard segments and polyether soft segments. Polyester and polyether segments are often homopolymer segments. This work aims at incorporating poly(butylene phthalate (PBP) as co‐hard segments in the hard segments of poly(butylene terephthalate) (PBT)‐b‐poly(tetramethylene oxide) (PTMO) thermoplastic elastomer, and investigating structures and properties of the resulting materials, denoted as (PBT‐co‐PBP)‐b‐PTMO. (PBT‐co‐PBP)‐b‐PTMO was synthesized from dimethyl terephthalate (DMT), dimethyl phthalate (DMP), PTMO (M_n = 1000 g/mol), and 1,4‐butanediol (BDO). The crystallinity of (PBT‐co‐PBP)‐b‐PTMO first decreased and then increased with increasing PBP content from 5% to 10% due to a decrease in the average sequence length of the PBT hard segments. Its elongation at break was increased by 200–350%. When the mass fractions of PBT and PBP were 42% and 8%, respectively, the (PBT‐co‐PBP)‐b‐PTMO showed the best performance in terms of permanent deformation, strength, and hardness whose values were 30%, 25 MPa, and 37 D, respectively. All the synthesized copolymers had good thermal stability with a decomposition temperature of 400°C or so. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43337.     

Low Temperature Endotherm in Multiblock Terpoly(ester‐b‐ether‐b‐amide) Thermoplastic Elastomers

The phenomenon of the occurrence of a middle‐temperature thermal effect in crystallizable multiblock thermoplastic elastomers, the so‐called annealing endotherm has not yet been univocally explained, hence, it was subjected to DSC analysis. The formation of this endotherm in response to the time and temperature of conditioning (stabilisation) of the sample has been followed. The investigations have been performed for a specific polymer system, poly(tetramethylene terephthalate)‐block‐poly(oxytetramethylene)‐block‐polylaurolactam‐(PBT‐b‐PTMO‐b‐PA12)‐_n. The specific property of this elastomer is the solubility or a partial solubility of one of the components (PBT block) in the two remaining ones being mutually insoluble. The occurrence of the two different amorphous phases (PBT and PA12) in this elastomer with glass transition temperatures T_g > 20°C is also possible. This specific system permits to observe an interesting phenomenon, since at the points determining the middle‐temperatures of the glass transition temperatures of the elastomer, the two small endotherms are shaping; after proper stabilisation they are approaching each other, and as a result of this process they would form one extreme. This extreme comprises the thermal effect of the dispersion of the mesomorphic aggregates being the intermediate form between the amorphous state and the crystalline state. The mesomorphic aggregates constitute the additional network points of the physical polymer network of the elastomer.     

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     

Synthesis and thermal characterization of random poly(butylene terephthalate‐co‐2‐methyl‐ethylene terephthalate) copolyesters

Poly(butylene terephthalate‐co‐2‐methyl‐ethylene terephthalate) (PBT/MET) was synthesized by incorporating 1,2‐propandiol(1,2‐PDO) into PBT chains. The molar composition and chemical structure of PBT/MET copolyesters were confirmed by means of FT‐IR and ¹H‐NMR. To investigate the effect of 1,2‐PDO on the thermal properties of PBT/MET copolyesters, the copolymerizations were carried out by varying various contents of MET units, and the prepared materials were evaluated by differential scanning calorimetry and thermogravimetric analysis. Results suggested that with the increase of the content of 1,2‐PDO, the amount of crystallinity and the melting temperature decline, while the glass transition temperature increases and the copolyesters become more transparent and brittle with respect to PBT homopolymer. In addition, the T_g‐composition and T_m‐composition data are well subjected to the Wood equation and Flory's equation, respectively. All these copolyesters are found to consist of the general trend displayed by copolymers reported elsewhere. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Phase behavior of blends containing amorphous poly(resorcinol phthalate‐block‐carbonate) and semicrystalline polyesters

The phase behavior of poly(resorcinol phthalate‐block‐carbonate) (RPC) with engineering polyesters was investigated by using differential scanning calorimeter (DSC) and dynamic mechanical analysis. RPC was found to form miscible blends with poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), and poly(cyclohexylmethylene terephthalate) (PCT), but was partially miscible with poly(1,4‐cyclohexanedimethylene‐1,4‐cyclohexanedicarboxylate) (PCCD) in the melt state and below the melting temperature (T_m). The degree of melting‐point depression indicates that the RPC is most miscible with PCT followed by PET and then PBT. Furthermore, with the help of empirical DSC data and the Nishi–Wang equation, the interaction parameters between RPC and PET, PBT, and PCT were quantified to be ?0.36, ?0.33, and ?0.54, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effect of segment length on some properties of thermoplastic poly(ester–siloxane)s

A series of novel thermoplastic elastomers, based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were synthesized by catalyzed two‐step, melt transesterification reactions of dimethyl terephthalate and methyl esters of carboxypropyl‐terminated poly(dimethylsiloxane)s (M?_n = 550–2170 g mol^?1) with 1,4‐butanediol. The lengths of both the hard and soft segments were varied while the weight ratio of the hard to soft segments in the reaction mixture was maintained constant (57/43). The molecular structure, composition and molecular weights of the poly(ester–siloxane)s were examined by ¹H NMR spectroscopy. The effectiveness of the incorporation of the methyl‐ester‐terminated poly(dimethylsiloxane)s into the copolymer chains was verified by chloroform extraction. The effect of the segment length on the transition temperatures (T_m and T_g) and the thermal and thermo‐oxidative degradation stability, as well as the degree of crystallinity and hardness properties of the synthesized TPESs, were studied. Copyright © 2003 Society of Chemical Industry     

Isothermal crystallization kinetics and melting behaviors of poly(butylene terephthalate) and poly(butylene terephthalate‐co‐fumarate) copolymer

The isothermal crystallization kinetics and melting behaviors after isothermal crystallization of poly(butylene terephthalate) (PBT) and poly(butylene terephthalate‐co‐fumarate) (PBTF) containing 95/5, 90/10, and 80/20 molar ratios of terephthalic acid/fumaric acid were investigated by differential scanning calorimetry. The equilibrium melting temperatures of these polymers were estimated by Hoffman–Weeks equation. So far as the crystallization kinetics was concerned, the Avrami equation was applied and the values of the exponent n for all these polymers are in the range of 2.50–2.96, indicating that the addition of fumarate does not affect the geometric dimension of PBT crystal growth. Crystallization activation energy (ΔE) and nucleation constant (K_g) of PBTF copolymers are higher than that of PBT homopolymer, suggesting that the introduction of fumarate hinders the crystallization of PBT in PBTF. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Polycarbonate/polyalkylene terephthalate blends: Interphase interactions and impact strength

Blends of polycarbonate (PC) and poly(alkylene terephthalate) (PAT) such as poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) were investigated. It was learned that processes of phase separation in blends consisting of PC and PAT can cause variations in properties of both the amorphous and crystalline phases. In PC/PBT blends the DSC technique did not detect crystalline portion of PBT with its concentrations up to 20 wt %. For PBT = 40 wt %, it forms a continuous phase, and blend's crystallinity is close to the additive values. The glass transition temperature (T_g) shifts to the lower temperature region. The relaxation spectrometry revealed strong adhesion between phases in the blends over the temperature range from the completion of β‐transition to T_gPAT. This interaction becomes weaker between T_gPAT and T_gPC. Temperature‐dependent variations in the molecular mobility and interphases interactions in the blends affect their impact strength. Over the temperature range where interphases interactions occur and the two components are in the glassy state, the blend is not impact resistant. Over the temperature range between T_gPAT and T_gPC the blends become impact‐resistant materials. This is because energy of crack propagation in the PAT amorphous phase—being in a high‐elastic state—dissipates. It is postulated that the effect of improving the impact strength of PC/PAT blends, which was found for temperatures between the glass transition temperatures of the mixed components, is also valid for other binary blends. © 2002 Wiley Perioodicals, Inc. J Appl Polym Sci 84: 1277–1285, 2002; DOI 10.1002/app.10472     

Synthesis and characterization of poly(butylene terephthalate) nanocomposite fibers: Thermo‐mechanical properties and morphology

Nanocomposites of poly(butylene terephthalate) (PBT) with the organoclay C₁₂PPh‐MMT were prepared using in situ intercalation polymerization. Hybrids with various organoclay contents were processed for fiber spinning to examine their thermal behavior, tensile mechanical properties, and morphologies for various draw ratios (DRs). The thermal properties (T_g, T_m, and T_Dⁱ) of the hybrid fibers were found to be better than those of pure PBT fibers and were unchanged by variation of the organoclay loading up to 2 wt %. However, these thermal properties remained unchanged for DRs ranging from 1 to 18. Most clay layers were dispersed homogeneously in the matrix polymer, although some clusters were also detected. The tensile properties of the hybrid fibers increased gradually with increasing C₁₂PPh‐MMT content at DR = 1. However, the ultimate strengths and initial moduli of the hybrid fibers decreased markedly with increasing DR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1247–1254, 2006     

Effects of water sorption on the physical properties of PET,PBT, and their long fibers composites

The behavior of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) on water aging has been studied above and below the glass transition temperature (T_g). The aging process is caused by: degradation of the matrix and an increase in crystallinity above T_g, and microcavitation at the amorphous/crystalline interface below T_g. Such behavior well explains the deviation of the sorption kinetics from the Fickian model. The apparent water diffusion coefficients and the transport activation energies of PET and PBT have been calculated at temperatures above and below T_g. The mechanical behavior of the two polymers on water aging has been measured by means of fracture mechanics and Izod impact tests at different stress concentration factors. An increase of toughness of PET at short aging times has been shown by mechanical tests and SEM analysis fracture surfaces of differently aged samples. Izod tests of PET and PBT composites reinforced by long glass fibers have shown the contribution of fibers to the total fracture energy.     

Phase behavior of ternary PBT–PC/phenoxy blends

Ternary polymer blends were obtained by melt mixing, mixing up to 30% poly(butylene terephthalate) (PBT) with polycarbonate (PC) and phenoxy in an attempt to improve the miscibility of the PC/phenoxy binary blend. Although most of the blends with a PBT content higher than 10% appear as transparent, two T_g's appeared at all the blend compositions. These T_g's correspond to PC-rich and phenoxy-rich phases where a low amount of the main component of the other phase and all PBT are dissolved in amounts that are a function of the PC/phenoxy ratio of the blend. Increasing the PBT contents in the blends closes to linearity the torque versus composition plot, so that a relationship between miscibility level and viscosity exists in these blends.     

Ternary polymer mixtures: Polyarylate/phenoxy/poly(butylene terephthalate)

The intended objective of this work was to bring together two immiscible polymers, polyarylate (PAr) and Phenoxy [poly(hydroxy ether of bisphenol-A)], preparing ternary mixtures with a third component, poly(butylene terephthalate) (PBT). Experimental results showed that ternary mixtures containing 30% or more PBT gave single glass transition temperatures by DSC. Moreover, the PBT melting point depended on the composition of the mixtures. These results, which could be indicative of the existence of a single amorphous phase in these blends, have been discussed. Nevertheless, results must be considered with caution, given the peculiarities of the T_g–composition diagrams for the miscible pairs PAr/PBT and Phenoxy/PBT. Hypothetic interchange reactions during melting have been found to be unimportant.     

Non-isothermal crystallization kinetic of recycled PET and its blends with PBT modified with epoxy-based multifunctional chain extender

A fundamental understanding of crystallization behavior is essential for the processing of both virgin and recycled polymers. This research delves into the crystallization characteristics and non-isothermal crystallization kinetics of recycled polyethylene terephthalate (rPET) and its blends with poly butylene terephthalate (PBT), which have been modified using epoxy-based multifunctional chain extenders (CE). The preparation of rPET/PBT blends involved a twin-screw extruder, with varying weight ratios and different CE concentrations. Differential scanning calorimetry was employed to perform crystallization analysis on the samples. The results underscore the profound impact of blend composition on the thermal characteristics of the system, with CE exerting only a marginal influence. The glass transition temperatures (T_g) of the two polymers were measured at 49 and 79°C. During blending, the T_g values demonstrated variations relative to the proportions but did not adhere to the Fox equation. Furthermore, PBT was found to enhance the crystallization tendencies of rPET, resulting in an increase in relative crystallinity from 11% to 36%. Notably, the crystallization rate of PBT at 0.40 min⁻¹ exceeded that of rPET at 0.36 min⁻¹. PBT minimally affected the crystallization rate constant of rPET-dominant blends, while rPET significantly reduced the crystallization rate in PBT-dominant blends.     

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     

Effect of the compatibilization of linear low‐density polyethylene‐g‐acrylic acid on the morphology and mechanical properties of poly(butylene terephthalate)/linear low‐density polyethylene blends

A poly(butylene terephthalate) (PBT)/linear low‐density polyethylene (LLDPE) alloy was prepared with a reactive extrusion method. For improved compatibility of the blending system, LLDPE grafted with acrylic acid (LLDPE‐g‐AA) by radiation was adopted in place of plain LLDPE. The toughness and extensibility of the PBT/LLDPE‐g‐AA blends, as characterized by the impact strengths and elongations at break, were much improved in comparison with the toughness and extensibility of the PBT/LLDPE blends at the same compositions. However, there was not much difference in their tensile (or flexural) strengths and moduli. Scanning electron microscopy photographs showed that the domains of PBT/LLDPE‐g‐AA were much smaller and their dispersions were more homogeneous than the domains and dispersions of the PBT/LLDPE blends. Compared with the related values of the PBT/LLDPE blends, the contents and melting temperatures of the usual spherulites of PBT in PBT/LLDPE‐g‐AA decreased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1059–1066, 2002; DOI 10.1002/app.10399     

Preparation and characterization of nano‐Sb2O3/poly(butylene terephthalate) composite powders based on high‐energy ball milling

In this work, a kind of composite powders with good dispersion and distribution of nano‐Sb₂O₃ particles in poly(butylene terephthalate) (PBT) was prepared by the high‐energy ball milling (HEBM). The effects of the milling time on the structure, morphology, particle size distribution, and thermal behavior of the nano‐Sb₂O₃/PBT composite powders were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, laser diffraction particle size analyzer, and thermal analysis (TGA, DTG and DSC) techniques. The results showed that the regular shape of PBT powders was converted into flakes and the nano‐Sb₂O₃ particles were well deagglomerated and better dispersed in the PBT matrix during the HEBM process. The mechanochemical activation that was provided by the HEBM process caused a reduction in the molecular weight of PBT, which result in favoring the first step of thermal degradation. Furthermore, two T_g’s were obtained in the case of the nanocomposite powders when the milling time was over 3 h, one of them being slightly higher than that of the pure PBT, which indicated that there was a special interaction between PBT and nano‐Sb₂O₃ particles. However, the HEBM process leaded to a decreasing of the PBT crystallinity. J. VINYL ADDIT. TECHNOL., 25:91–97, 2019. © 2018 Society of Plastics Engineers     

Synthesis and characterization of poly(ester ether siloxane)s

A series of novel thermoplastic elastomers based on ABA‐type triblock prepolymers, poly[(propylene oxide)–(dimethylsiloxane)–(propylene oxide)] (PPO‐PDMS‐PPO), as the soft segments, and poly(butylene terephthalate) (PBT), as the hard segments, was synthesized by catalyzed two‐step melt transesterification of dimethyl terephthalate (DMT) with 1,4‐butanediol (BD) and α,ω‐dihydroxy‐(PPO‐PDMS‐PPO) (M?_n = 2930 g mol^?1). Several copolymers with a content of hard PBT segments between 40 and 60 mass% and a constant length of the soft PPO‐PDMS‐PPO segments were prepared. The siloxane‐containing triblock prepolymer with hydrophilic terminal PPO blocks was used to improve the compatibility between the polar comonomers, i.e. DMT and BD, and the non‐polar PDMS segments. The structure and composition of the copolymers were examined using ¹H NMR spectroscopy, while the effectiveness of the incorporation of α,ω‐dihydroxy‐(PPO‐PDMS‐PPO) prepolymer into the copolyester chains was controlled by chloroform extraction. The effect of the structure and composition of the copolymers on the transition temperatures (T_m and T_g) and the thermal and thermo‐oxidative degradation stability, as well as on the degree of crystallinity, and some rheological properties, were studied. Copyright © 2006 Society of Chemical Industry     

Sequence analysis and fiber properties of a blend of poly(ethylene terephthalate) and poly(ethylene terephthalate‐co‐4,4′‐bibenzoate)

Blends of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate‐co‐4,4′‐ bibenzoate) (PETBB) are prepared by coextrusion. Analysis by ¹³C‐NMR spectroscopy shows that little transesterification occurs during the blending process. Additional heat treatment of the blend leads to more transesterification and a corresponding increase in the degree of randomness, R. Analysis by differential scanning calorimetry shows that the as‐extruded blend is semicrystalline, unlike PETBB15, a random copolymer with the same composition as the non‐ random blend. Additional heat treatment of the blend leads to a decrease in the melting point, T_m, and an increase in glass transition temperature, T_g. The T_m and T_g of the blend reach minimum and maximum values, respectively, after 15 min at 270°C, at which point the blend has not been fully randomized. The blend has a lower crystallization rate than PET and PETBB55 (a copolymer containing 55 mol % bibenzoate). The PET/PETBB55 (70/30 w/w) blend shows a secondary endothermic peak at 15°C above an isothermal crystallization temperature. The secondary peak was confirmed to be the melting of small and/or imperfect crystals resulting from secondary crystallization. The blend exhibits the crystal structure of PET. Tensile properties of the fibers prepared from the blend are comparable to those of PET fiber, whereas PETBB55 fibers display higher performance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1793–1803, 2004     

Synthesis and characterization of a poly(ether–ester) copolymer from poly(2,6 dimethyl‐1,4‐phenylene oxide) and poly(ethylene terephthalate)

A series of poly(ether–ester) copolymers were synthesized from poly(2,6 dimethyl‐1,4‐phenylene oxide) (PPO) and poly(ethylene terephthalate) (PET). The synthesis was carried out by two‐step solution polymerization process. PET oligomers were synthesized via glycolysis and subsequently used in the copolymerization reaction. FTIR spectroscopy analysis shows the coexistence of spectral contributions of PPO and PET on the spectra of their ether–ester copolymers. The composition of the poly(ether–ester)s was calculated via ¹H NMR spectroscopy. A single glass transition temperature was detected for all synthesized poly(ether–ester)s. T_g behavior as a function of poly(ether–ester) composition is well represented by the Gordon‐Taylor equation. The molar masses of the copolymers synthesized were calculated by viscosimetry. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Crystallization in blends of poly(ethylene terephthalate) and poly(butylene terephthalate)

Blends composed of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) were melt-mixed in a Brabender cam mixer at different mixing speeds. The glass transition (T_g) and the crystallization behavior of the blends from glassy state were studied using DSC. It was found that although the blends had the same composition and exhibited the similar T_g, their properties of crystallization could be different; some exhibited a single crystallization peak and some exhibited multiple crystallization peaks depending upon experimental conditions. Results indicated that the behavior of crystallization from glassy state were influenced by entanglement and transesterification of chains. The crystallization time values were obtained over a wide range of crystallization temperature. From curve fitting, the crystallization time values and the temperature, at which the crystallization rate reaches the maximum, were found.