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     

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     

Crystallization behaviour of random block copolymers of poly(butylene terephthalate) and poly(tetramethylene ether glycol)

The morphology and crystallization behaviour of random block copolymers of poly(butylene terephthalate) and poly(tetramethylene ether glycol) have been investigated. Single crystals have been grown in thin films crystallized from the melt. Well defined lamellae, exhibiting (hkO) single crystal electron diffraction patterns have been observed in copolymers containing down to 49 wt% (0.83 mole fraction) poly(butylene terephthalate). WAXS and electron diffraction support a model of a relatively pure poly(butylene terephthalate) crystal core with the poly(tetramethylene ether glycol) (soft segment) sequences and short hard segments being rejected to the lamellar surface and the soft segment rich matrix. The lateral dimensions of the lamellae are determined by the number of hard segment sequences long enough to traverse the stable crystal size at the crystallization temperature. This leads to an initial population of crystals formed at T_c and a second set of smaller crystals that grow from the short hard segment sequences upon cooling to room temperature. The result is fractionation by sequence length due to a coupling of the sequence distribution with the stable crystal size at the crystallization temperature.     

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     

Rheology modification of PVC plastisols with poly(butylene terephthalate)-b-poly(tetramethylene glycol)

A few percent of poly(butylene)-b-poly(tetramethylene glycol) was able to turn a liquid plasticizer into a gel, and thus imparted yield stresses to the fluid. When the plasticizer contained as little as 2.5 wt % of the block copolymer, sag free plastisols were obtained. A reduction in tensile strength was found for the modified plastisols, while the elongation was not affected. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 749–753, 1997     

Mechanical and dynamic mechanical thermal properties of heat‐ and oil‐resistant thermoplastic elastomeric blends of poly(butylene terephthalate) and acrylate rubber

Poly(butylene terephthalate) (PBT) and acrylate rubber (ACM) were melt‐blended in a Brabender Plasticorder at 220°C and 40 rpm rotor speed. The blends were dynamically vulcanized by the addition of hexamethylenediamine carbamate (HMDC) during the melt‐blending operation in the Brabender. Dynamic mechanical thermal analysis (DMTA) of the blends suggests a two‐phase morphology of the blends with two separate T_g 's for both components. The blends were also compatibilized by the addition of a dibutyl tin dilaurate (DBTDL) catalyst, which enhanced the extent of the transesterification reaction between the two polymers. The transreaction results in softer blends with higher elongation properties. The above blends also show very good oil and heat resistance at elevated temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1001–1008, 2000     

Melting behavior and crystallization kinetics of poly(butylene terephthalate‐co‐diethylene terephthalate) and poly(butylene terephthalate‐co‐triethylene terephthalate) copolyesters

The melting behavior of poly(butylene terephthalate‐co‐diethylene terephthalate) and poly(butylene terephthalate‐co‐triethylene terephthalate) copolymers was investigated by differential scanning calorimetry after isothermal crystallization from the melt. Multiple endotherms were found for all the samples, and attributed to the melting and recrystallization processes. By applying the Hoffman‐Weeks' method, the equilibrium melting temperatures of the copolymers under investigation were obtained. Two distinct peaks in the crystallization exothermic curve were observed for all the samples. Both of them appeared at higher times than that of PBT, indicating that the introduction of a comonomer decreased the crystallization rate. The observed dependence of this latter on composition was explained on the basis of the content of ether–oxygen atoms in diethylene and triethylene terephthalate units, and of the different sizes of these units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3545–3551, 2001     

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     

PBTA/TPS共混物的结构、性能和断裂行为

将热塑性淀粉(TPS)与聚(对苯二甲酸丁二醇酯-己二酸丁二醇酯)(PBAT)挤出共混并注塑成型,制备了可完全生物降解的TPS/PBAT复合材料制品。采用扫描电子显微镜研究了注塑复合材料的层次结构与微观形态,测试了不同组分复合材料的性能和应力应变行为。结果表明：TPS在PBAT中呈皮芯结构分布,随含量增加逐渐由芯层向皮层分布。当含量为45%时,芯层到皮层形成均匀的以纤维为主的分散相形态,提高了复合材料的力学性能。加入TPS后会改变复合材料的形变行为,由类似半结晶聚合物的应力应变行为转变为屈服-冷拉行为。     

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     

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T_m), cold crystallization and glass transition (T_g) decreased with the copolymerization. T_m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T_g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.     

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     

Mechanical properties of poly(ethylene terephthalate) modified with functionalized polymers

This study examined the effect of blending poly(ethylene terephthalate) (PET) with 5% of a functionalized polymer. The blends were characterized by particle size and size distribution, unnotched tensile behavior, toughness, and notch sensitivity. The improved properties of blends that incorporated a functionalized elastomer were consistent with in situ formation of a graft copolymer by reaction with PET end groups. Triblock copolymers were examined that had styrene end blocks and an ethylene/butylene midblock (SEBS) with grafted maleic anhydride. The present study extended previous investigations that focused on level of grafting to examine the effects of component molecular weight and PET hydroxyl‐to‐carboxyl end‐group ratio. Increasing the molecular weight of the SEBS and decreasing the hydroxyl‐to‐carboxyl ratio of the PET increased the effectiveness of the SEBS. In addition, a mix of an unfunctionalized SEBS with a functionalized SEBS was more effective than a single SEBS with the same total anhydride content. The same elastomers were the most effective for modifying a lower molecular weight PET (intrinsic viscosity 0.73) and a higher molecular weight PET (intrinsic viscosity 0.95). Some functionalized polypropylenes included in the study did not enhance the properties of PET. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 203–219, 1999     

聚对苯二甲酸丁二酯纤维热裂解分析

采用裂解气相色谱-质谱法研究了400～700℃聚对苯二甲酸丁二酯(PBT)纤维热裂解作用,并对其裂解机理进行了分析。结果表明:400℃时PBT裂解,仅检测到9种主要裂解产物。随裂解温度上升,裂解产物增加。在600℃时,检测到28种裂解产物,较高相对含量的主要裂解产物为苯甲酸、1,4-苯二甲酸-3-丁烯酯、1,4-苯二甲酸-二-3-丁烯酯、苯甲酸丁烯酯、苯、四氢呋喃等6种裂解碎片。1,4-苯二甲酸-3-丁烯酯、1,4-苯二甲酸-二-3-丁烯酯、苯甲酸丁烯酯、二苯甲酸-1,4-丁酯、对甲基苯甲酸丁烯酯、3-丁烯基苯等裂解产物是PBT特征性产物。1,4-苯二甲酸-3-丁烯酯、1,4-苯二甲酸-二-3-丁烯酯、苯甲酸丁烯酯是鉴别PBT纤维的主要碎片峰。PBT裂解过程中,发生链剪切作用,由聚合物链断裂成二聚体。     

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     

纳米粒子填充改性聚对苯二甲酸丁二醇酯

讨论了纳米粒子填充改性聚对苯二甲酸丁二醇酯（PBT）的研究进展，分别采用插层聚合和熔体聚合的方法制得PBT／纳米复合材料，讨论了结构和性能的关系。     

Strain recovery of post-yield compressed semicrystalline poly(butylene terephthalate)

Cubic specimens of a semicrystalline poly(butylene terephthalate) (PBT) have been compressed up to post-yield deformation levels with a fast (3.0 × 10⁻² s⁻¹) and a slow (1.5 × 10⁻⁴ s⁻¹) strain rate at three different temperatures (25 °C, 45 °C, and 100 °C, i.e. below, close and above the glass transition temperature of the material, T_g, respectively). Differently from literature results reported for amorphous polymers, semicrystalline PBT shows that, after a post-yield deformation, recovery occurs also at temperatures higher than T_g, and that an irreversible deformation, ?_irr, is set in the material. The irreversible strain component has been evaluated as the residual deformation after a thermal treatment of 1 h at 180 °C.After unloading, isothermal strain recovery has been monitored for time periods of 1 h at various temperatures. From the obtained data, strain recovery master curves have been constructed by a time-temperature superposition scheme. The features of the recovery process for the various deformation conditions have been analysed. In particular, it appears that specimens deformed below T_g show a lower irreversible component, whereas, when deformed above T_g, they display a higher irreversible deformation and a slower recovery process. Moreover, the effect of deformation rate appears particularly marked for samples deformed above T_g.     

ABS-g-GMA增韧聚对苯二甲酸丁二醇酯的研究

用甲基丙烯酸环氧丙酯（（MA）接枝的丙烯腈／丁二烯／苯乙烯（ABs）接枝共聚物（ABS-g-GMA）改善聚对苯二甲酸丁二醇酯（PBT）的缺口冲击韧性。动态力学分析、差示扫描量热分析以及流变性能测试结果表明，GMA引入到ABS中，随GMA含量的增加，PBT与ABS的玻璃化转变温度相互靠近，PBT的熔点降低，共混体系的扭矩、温度提高，这些结果表明GMA提高了PBT与ABS之间的相容性；增容反应导致ABS在PBT基体中均匀、稳定分散，有利于共混物性能的改善；交联反应导致交联聚集网状结构的生成，使共混物性能变差。冲击强度结果表明，1％（质量含量。下同）GMA含量就可以导致PBT／ABS-g-GMA共混物冲击韧性显著改善，当ABS-g-GMA1含量为30％时，共混物冲击强度高达850J／m。     

PBT共混改性研究最新进展

综述了最近几年国内外聚对苯二甲酸丁二醇酯(PBT)共混改性的研究进展,分类介绍PBT/聚烯烃、PBT/同系聚酯、PBT/液晶、PBT/弹性体、PBT/聚碳酸酯等不同共混体系,讨论了各体系中的相行为、相容性、热稳定性、力学性能等,并对该类共混物的发展趋势作了简要的分析。