Cyclic oligomers in poly(1,4-butylene terephthalate)

The cyclic oligomers present in poly(1,4-butylene terephthalate) have been extracted and quantitatively determined by high pressure liquid chromatography.     

Synthesis and physicochemical properties of new (bio)degradable poly(ester-urethane)s containing polylactide and poly[(1,4-butylene terephthalate)-co-(1,4-butylene adipate)] segments

(Bio)degradable poly(ester-urethane)s containing polylactide (PLA) and poly[(1,4-butylene terephthalate)-co-(1,4-butylene adipate)] (BTA) segments in the main chain were synthesized and their properties were examined. Novel poly(ester-urethane)s were obtained from isophorone diisocyanate (IPDI), synthetic PLA-diol and/or synthetic BTA-diol oligomers in a two-step process. PLA-diol and BTA-diol oligomers were received via glycolysis of their respective polymers: PLA and BTA. Butanediol (BD) was used as a polymer chain extender.The synthesized poly(ester-urethane)s were characterized by DSC, NMR, GPC, FTIR and X-ray methods. The poly(ester-urethane)s that were examined had a single glass transition temperature (T_g), which pointed to a one-phase system. The biodegradability of the received poly(ester-urethane)s was examined under industrial composting conditions. The results prove the possibility of synthesizing new perspective application materials, surrendering (bio)degradation in the environment.     

Synthesis, characterization, and properties of poly(ethylene terephthalate)/poly(1,4-butylene succinate) block copolymers

Reactive blending at 290 °C of a series of mixtures of poly(ethylene terephthalate) (PET) and poly(1,4-butylene succinate) (PBS) led to the formation of block PET/PBS copolyesters. The block lengths of the resulting copolymers decreased with the severity of the treatment. Copolyesters with PET/PBS molar compositions of 90/10, 80/20, 70/30, and 50/50 were prepared by this method and their composition and microstructure were characterized by ¹H and ¹³C NMR, respectively. The T_g, T_m, and crystallinity of the copolymers decreased as the content in PBS and the degree of randomness increased. The elastic modulus and tensile strength of the copolymers decreased with the content of PBS, whereas, on the contrary, the elongation at break increased. The PET/PBS copolymers exhibited a pronounced hydrolytic degradability, which increased with the content in 1,4-butylene succinic units. Hydrolysis mainly occurred on the aliphatic ester groups.     

Microenvironments in poly(1,4-butylene terephthalate) solids revealed by fluorescence spectroscopy

The relationship between the fluorescence behavior and crystallinity of poly(1,4-butylene terephthalate) (PBT) films, prepared by a spin-casting method, was investigated. Throughout the fluorescence measurements of PBT thin films having different crystallinities, the main-chain phenylene fluorescence near 320 nm and that near 365 nm were assigned to monomer fluorescence mainly from crystalline regions and excimer fluorescence from amorphous regions, respectively. It was found that the ratio of the fluorescence intensity at 320 nm to that at 365 nm can be an effective indicator of PBT crystallinity. The present work should provide a quick and nondestructive method for determining the crystallinity of PBT factory products.     

Molecular weight–viscosity relationships for poly(1,4-butylene terephthalate)

The correlation between number-average molecular weight and intrinsic viscosity in 60:40 phenol-sym-tetrachloroethane at 30°C for poly(1,4-butylene terephthalate) was established from endgroup determinations as well as by gel permeation chromatography, eqs. (1) and (10a). The GPC data also yielded relationships between weight- and z-average molecular weight and intrinsic viscosity, eqs. (10b) and (10c). Melt viscosities, corrected for the thermal history of the melt, were measured at shear stresses in the range of 0.02–0.55 MPa. Linear PBT melts were found to become non-Newtonian at a shear stress of approximately 0.11 MPa, independent of molecular weight within the range studied. Correlations between melt viscosity at low shear stress versus intrinsic viscosity are presented, as well as the dependence of melt viscosity in the non-Newtonian region on shear stress and low-stress (Newtonian) melt viscosity.     

Effect of aging on the mechanical properties of cold-crystallized poly(trimethylene terephthalate)

The changes in the mechanical and thermal properties of cold-crystallized poly(trimethylene terephthalate) during aging at 60 and 80 °C were investigated. A significant increase in the tensile modulus and stress at yield and a decrease in strain at yield were observed for both aging temperatures. Differential scanning calorimetry (DSC) scans of the aged sample showed an endothermic annealing peak 10-20 °C above the previous aging temperature, the maximum temperature and enthalpic content of these peaks increased with aging time. Dynamic mechanical measurements indicated a relaxation process starting at about 20 °C above the aging temperature and correlate with the annealing peak detected by DSC. Density measurements and wide-angle X-ray scattering investigation revealed that neither the crystallinity increased significantly nor did the crystal structure changed. These results were explained by the existence of a third phase besides the crystalline and the ‘classical amorphous’ which involves oriented and constrained ‘non-crystalline’ polymer chain sequences close to the crystalline lamellae.     

聚(对苯二甲酸-1,3-丁二醇酯/对苯二甲酸-1,4-丁二醇酯)/PEG嵌段共聚物的合成及性能研究

用熔融缩聚法合成了一系列聚(对苯二甲酸-1,3-丁二醇酯/对苯二甲酸-1,4-丁二醇酯)/聚乙二醇的嵌段共聚物。用FT-IR,1H-NMR,DSC,TGA,水降解测试等方法表征了材料的结构与性能。FT-IR和1H-NMR分析表明合成得到的共聚物为预期产物;DSC分析显示,共聚聚酯随着1,3-丁二醇在共聚物中比例的增大,熔点(Tm)逐渐降低,由158.24℃下降至104.19℃,玻璃化温度(Tg)逐渐升高,由4.86℃升至24.56℃,合成得到的共聚酯趋向于无定形态;TGA分析表明1,3-丁二醇在共聚酯中比例增大会使聚酯的热稳定性下降,但合成得到的共聚酯依然具有较好的热稳定性,初始分解温度大于310℃,不需要在反应过程中添加热稳定剂;水降解测试结果表明共聚物随1,3-丁二醇比例的增加,降解速率大幅提升。     

Effect of styrene-co-acrylonitrile on cold crystallization and mechanical properties of poly(ethylene terephthalate)

Blends of poly(ethylene terephthalate) (PET) with small amounts of styrene-co-acrylonitrile (SAN) were prepared by melt blending, and cold crystallization of these mixtures was investigated by means of differential scanning calorimetry. The results suggest that SAN interacts with the amorphous phase of PET, as observed by variations in the glass transition temperature and in the morphology of the blends, analyzed by scanning electron microscopy. The addition of 1% SAN promoted a significant reduction in the crystallization rate of PET, in a manner similar to that of an antinucleating agent. However, the crystallinity of the PET/SAN blends was comparable with that of neat PET; hence, mechanical properties were only slightly affected. Kinetic parameters were determined using Avrami theory; Avrami plots presented a nonlinear behavior at the end of crystallization, indicating that cold crystallization proceeds in two stages. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Improved mechanical properties of poly(ethylene terephthalate) nanocomposite fibers

Improvements in Young's modulus and strength (tenacity) of poly(ethylene terephthalate) (PET) fibers were obtained by drawing unoriented nanocomposite filaments containing low concentrations (<3 wt%) of various organically modified montmorillonites (MMTs) in a second step at temperatures above the glass transition. Prior to melt spinning, solid‐state polymerization was used to rebuild lost molecular weight, due to MMT‐induced degradation, to a level suitable for producing high strength fibers. Greater improvements in mechanical properties occurred when the MMT stacks were intercalated with PET. A nominal 1 wt% loading of dimethyl‐dehydrogenated tallow quaternary ammonium surface modified MMT in drawn PET fiber showed a 28% and 63% increase in Young's modulus and strength, respectively. Relative to an unfilled PET fiber, these results surpassed the upper bound of the rule of mixtures estimate and suggested that both the type of surface modification and concentration of MMT affect the degree of PET orientation and crystallinity. Furthermore, drawability above T_g and elongation at break increased upon the addition of organically modified MMT to unoriented PET fibers, which was a key distinction of this work from others examining similar systems. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Morphology and mechanical properties of injection molded poly(ethylene terephthalate)

This work reports on the relationships between processing, the morphology and the mechanical properties of an injection molded poly(ethylene terephthalate), PET. Specimens were injection molded with different mold temperatures of 30°C, 50°C, 80°C, 100°C, 120°C, 150°C, while maintaining constant the other operative processing parameters. The thermomechanical environment imposed during processing was estimated by computer simulations of the mold‐filling phase, which allow the calculation of two thermomechanical indices indicative of morphological development (degree of crystallinity and level of molecular orientation). The morphology of the moldings was characterized by differential scanning calorimetry (DSC) and by hot recoverable strain tests. The mechanical behavior was assessed in tensile testing at 5 mm/min and 23°C. A strong thermal and mechanical coupling is evidenced in the injection molding process, significantly influencing morphology development. An increase in the mold temperature induces a decrease of the level of molecular orientation (decrement in the hot recoverable strain) and an increment in the initial crystallinity of the moldings (decrement in the enthalpy of cold crystallization), also reflected in the variations of the computed thermomechanical indices. The initial modulus is mainly dependent upon the level of molecular orientation. The yield stress is influenced by both the degree of crystallinity and the level of molecular orientation of the moldings, but more significantly by the former. The strain at break was not satisfactorily linked directly to the initial morphological state because of the expected morphology changes occurring during deformation. Polym. Eng. Sci. 44:2174–2184, 2004. © 2004 Society of Plastics Engineers.     

Effect of the temperature on the structure and mechanical properties of poly(ethylene terephthalate) fibres and yarns

The load—elongation diagrams were obtained for PETP yarns and monofilaments at different deformation temperatures, demonstrating the dependence of the σ(ε) curves on the testing temperature and the thermomechanical history of the samples. The dependences of the basic strain characteristics determined from the σ(ε) curves on the temperature can be used to predict the change in the mechanical properties of PETP yarns and fibres at high temperatures. In addition to the fundamental relaxation transition, the σ(ε) curves can be used to find a new transition in the 180°C region which controls the behavior of PETP yarns and fibres above the transition temperature. The thermomechanical tests and structural studies of the fibres at different temperatures allow correlating the transition found with crystallites and assigning it to an α_c transition based on the characteristic set of properties. St. Petersburg State University of Technology and Design. Translated fromKhimicheskie Volokna, No. 1, pp. 32–35, January–February, 2000.     

Effects of reprocessing on the structure and mechanical properties of poly(trimethylene terephthalate)

The effects of reprocessing by extrusion for up to four cycles on the structure and mechanical properties of poly(trimethylene terephthalate) (PTT) were studied. Reprocessing did not change the chemical structure of the polymer but led to both yellowing and molecular weight reduction. Young's modulus and the yield stress of PTT remained constant or decreased with successive extrusion cycles, probably because of the observed slight specific volume increase. The continuous reduction in the break properties due to reprocessing was smaller than that found in similar polyesters and was attributed to the molecular weight reduction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2775–2780, 2002     

Effect of recycling on the properties of poly(ethylene terephthalate) films

Different proportions of recycled poly(ethylene terephthalate) (PET) films were blended with virgin PET and evaluated for physicomechanical, chemical, thermal, optical and barrier properties. The safety evaluation of the films for food contact applications has also been carried out. The variations in properties, such as tensile behaviour, impact strength, tear resistance, burst strength, gloss, haze, barrier properties, crystallization temperature and melting temperature, are reported. © 2000 Society of Chemical Industry     

Effect of morphology on barrier properties of poly(ethylene terephthalate)

The effects of morphology on the barrier properties of poly(ethylene terephthalate) (PET) have been investigated. Various levels of crystallinity can be developed in PET as a result of thermal exposure, orientation, and heat setting. The morphologies of the crystalline phase are affected by the conditions of their formation. As a result of morphological differences, samples with equivalent levels of crystallinity have been found to exhibit different oxygen barrier properties. These differences are most apparent at low and intermediate levels of crystallinity. For thermally crystallized systems, at the same crystalline content, increasing superstructure size in the crystalline phase leads to greater tortuosity for the permeant molecules, resulting in lower permeability. For stretched and heat set PET, transport properties can be correlated with birefringence as well as overall orientation, measured in terms of fraction of molecules in the trans or extended chain conformation. At high levels of crystallinity, where the spherulites become volume filling, permeation takes place primarily through the interlamellar regions of the crystalline phase and is controlled by level of crystallinity, independent of the mode of crystallization. The barrier properties of PET, before spherulitic impingement occurs, are governed by the size and number of spherulites as well as by the amorphous orientation present in non‐crystalline regions. POLYM. ENG. SCI., 45:400–409, 2005. © 2005 Society of Plastics Engineers     

Composites from biodegradable and biocompatible methylcellulose,poly(d,l-lactide-co-glycolide) and poly(1,4-butylene succinate) with enhanced properties

Polymer materials based on fossil resources have brought great convenience to various industries. However, environmental pollution is becoming increasingly conspicuous due to their difficult degradation in nature. Therefore, biodegradable composites are highly desired. In the present work, a simple and feasible preparation approach was presented to fabricate biodegradable and biocompatible composite films including methylcellulose/poly(d ,l -lactide-co-glycolide) (MC/PLGA) and methylcellulose/poly(1,4-butylene succinate) (MC/PBS). The effects of MC/PLGA and MC/PBS mass ratios on the morphology, crystalline state, mechanical properties and thermal stability of the composite films were systematically investigated. At the same time, the influence of thermal compression treatment on mechanical properties (tensile strength and elongation) and the cyclic utilization of the composite films were also estimated. The composite films displayed enough good mechanical properties, re-usability and thermal stability.     

Structure‐mechanical properties relationship of poly(ethylene terephthalate) fibers

The correlation between the fiber structure and mechanical properties of two different poly(ethylene terephthalate) fiber types, that is, wool and cotton types produced by three producers, was studied. Fiber structure was determined using different analytical methods. Significant differences in the suprastructure of both types of conventional textile fibers were observed, although some slight variations in the structure existed between those fibers of the same type provided by different producers. A better‐developed crystalline structure composed of bigger, more perfect, and more axially oriented crystallites was characterized for the cotton types of PET fibers. Crystallinity is higher, long periods are longer, and amorphous domains inside the long period cover bigger parts in this fiber type in comparison with the wool types of fibers. In addition, amorphous and average molecular orientation is higher. The better mechanical properties of cotton PET fiber types, as demonstrated by a higher breaking tenacity and modulus accompanied by a lower breaking elongation, are due to the observed structural characteristics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3383–3389, 2003     

Structure and mechanical properties of highly oriented poly(ethylene terephthalate) films

The relationships between the supermolecular structure of poly(ethylene terephthalate) films subjected to cold drawing and subsequent zone annealing and their mechanical properties are investigated. The effectiveness of zone annealing is compared to that of annealing with fixed ends. Microstructural changes occurring during heat treatment and zone annealing are monitored using wide angle X-ray scattering, small angle X-ray scattering, infrared spectroscopy, differential scanning calorimetry, and static mechanical tests. The very high modulus and strength of the zone-annealed films are directly attributed to the large number of the molecules connecting the crystallites.     

Synthesis and characterization of poly(1,4-dihydroxyanthraquinone terephthalate)

A novel polymeric dye containing an anthraquinone ring was prepared by solution polycondensation. The molecule geometry was fully optimized on the basis of the AM1 method. The hydrogen bond was formed and retained coplanarity in the molecular structure. In its UV spectrum, a large hypsochromic shift and a hypochromic effect were observed due to polyesterification. The polymeric dye was also characterized by means of IR and TG. Its thermal degradation mechanism was elucidated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2246–2248, 2001     

Structure and mechanical properties of compatibilized poly(ethylene terephthalate)/poly(ethylene octene) blends

Poly(ethylene terephthalate) (PET) based blends were obtained by melt blending PET with up to 30 wt% poly(ethylene‐octene) either modified with maleic anhydride (mLLDPE) or not (LLDPE). Both PET/LLDPE and PET/mLLDPE blends were immiscible. The dispersed phase particle size was large in LLDPE blends, but upon mLLDPE addition, it decreased to a small (submicron) and rather constant value with composition. This indicated compatibilization, and was attributed to specific interactions between the ester and maleic groups of PET and mLLDPE, respectively, rather than grafting reactions between components. Linear decreases in Young's modulus and yield stress, and ductility increases were observed in blends with mLLDPE. Super‐toughness was achieved in blends with mLLDPE, which took place when the critical interparticle distance (ID_c) was below 0.17 μm and with only half the cross section of the specimens broken. The ID_c of these blends and those of other blends from bibliography were compared with the adhesion levels estimated from the expected main interactions between the components of the blends. This comparison strongly indicated that, at least through an adhesion range, ID_c depends on the adhesion level, and that ID_c decreases as the adhesion level increases. POLYM. ENG. SCI. 46:172–180, 2006. © 2005 Society of Plastics Engineers