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PBT
Terms modified by PBT Selected AbstractsContaminant pattern and bioaccumulation of legacy and emerging organhalogen pollutants in the aquatic biota from an e-waste recycling region in South ChinaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2010Ying Zhang Abstract Legacy pollutants, polychlorinated biphenyls (PCBs), dichlorodiphenyl trichloroethane and its metabolites (DDTs), and some emerging organhalogen pollutants, such as polybrominated diphenyl ethers (PBDEs), hexabromobenzene (HBB), pentabromotoluene (PBT), 2,3,4,5,6-pentabromoethyl benzene (PBEB), 1,2- bis (2,4,6-tribromophenoxy) ethane (BTBPE), and dechlorane plus (DP), were detected in an aquatic food chain (invertebrates and fish) from an e-waste recycling region in South China. Polychlorinated biphenyls, DDTs, PBDEs, and HBB were detected in more than 90% of the samples, with respective concentrations ranging from not detected (ND),32,000,ng/g lipid weight, ND,850,ng/g lipid weight, 8 to 1,300,ng/g lipid weight, and 0.28 to 240,ng/g lipid weight. Pentabromotoluene, PBEB, BTBPE, and DP were also quantifiable in collected samples with a concentration range of ND,40,ng/g lipid weight. The elevated levels of PCBs and PBDEs in the organisms, compared with those in non-e-waste regions in South China, suggest that these two kinds of pollutants derived mainly from e-waste recycling practices. Hexabromobenzene was significantly correlated with PBDEs, implying that HBB come from the release of e-waste along with PBDEs and/or the pyrolysis of BDE209. Most of the compounds whose trophic magnification factor (TMF) could be calculated were found to biomagnify (TMF > 1). Hexabromobenzene was also found, for the first time, to biomagnify in the present food web, with a TMF of 2.1. Environ. Toxicol. Chem. 2010;29:852,859. © 2010 SETAC [source] Hepatic phenylalanine metabolism measured by the [13C]phenylalanine breath testEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 4 2001T. Kobayashi Background The amino acid clearance test including phenylalanine is known to reflect liver functional reserve, which correlates with surgical outcome; however, the procedure is not clinically useful because of its laborious and time-consuming nature. This study evaluates whether phenylalanine oxidation capacity measured by a breath test could reflect liver functional reserve. Design We determined phenylalanine oxidation capacity in 42 subjects using the l -[1- 13C]phenylalanine breath test (PBT). The 13CO2 breath enrichment was measured at 10-min intervals for 120 min after oral administration of 100 mg of l -[1- 13C]phenylalanine. Subjects were divided into the following three groups according to their plasma retention rate of indocyanine green at 15 min (ICG R15): Group I (ICG R15 <,10%), Group II (ICG R15 10,20%), and Group III (ICG R15 >,20%). First, we determined the parameters of the phenylalanine oxidation capacity that differentiated these groups and then, using these parameters, we compared the PBT with the ICG clearance test, Child,Pugh classification score and standard liver blood tests. Results The %13C dose h,1 at 30 min and cumulative excretion at 80 min were significantly different among the three groups (P < 0·05). These two parameters significantly correlated with the ICG R15, Child,Pugh classification score (P < 0·0001) and results of standard liver blood tests (P < 0·05). Conclusions Phenylalanine oxidation capacity measured by the PBT was reduced according to the severity of liver injury assessed by the ICG clearance test, Child,Pugh classification, and standard liver blood tests. These results indicate that the PBT can be used as a noninvasive method to determine liver functional reserve. [source] A Comparative Study of the Optical and Electroluminescent Properties of EuIII Complexes with TTA and 2-(2,-Pyridyl)azoles: The Crystal Structure of [Eu(TTA)3(PBO)]EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2006Li-Hua Gao Abstract Two EuIII mixed-ligand complexes, namely [Eu(TTA)3(PBO)]and [Eu(TTA)3(PBT)] [TTA = 1,1,1-trifluoro-3-(2-thenoyl)acetonato, PBO = 2-(2,-pyridyl)-1,3-benzoxazole, and PBT = 2-(2,-pyridyl)-1,3-benzothiazole], have been synthesized. [Eu(TTA)3(PBO)] has been structurally characterized by single-crystal X-ray diffraction analysis. The complex crystallizes in the monoclinic space group C2/c. The lattice parameters are a = 41.346(4), b = 10.0538(8), c = 20.3793(16) Å, , = 110.922(2)°, Z = 8. The EuIII ion is eight-coordinate, with three bidentate TTA, anions and one bidentate N,O-chelated PBO molecule. A comparative study by UV and emission spectroscopy was carried out and electroluminescent properties of the related complexes [Eu(TTA)3(PBO)] and [Eu(TTA)3(PBT)] are reported as well. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Characterization of the migration of lung and blood T cells in response CXCL12 in a three-dimensional matrixIMMUNOLOGY, Issue 4 2010Caroline E. Day Summary The ability of T cells to microlocalize within tissues, such as the lung, is crucial for immune surveillance and increased T-cell infiltration is a feature of many inflammatory lung conditions. T-cell migration has mainly been studied in two-dimensional assays. Using three-dimensional collagen gels to mimic the extracellular matrix of lung tissue, we have characterized the migration of T lymphocytes isolated from peripheral blood (PBT) and lung (LT) in response to interleukin-2 (IL-2) and CXCL12. Freshly isolated PBT and LT showed a low degree of migration (blood 4·0 ± 1·3% and lung 4·1 ± 1·7%). Twenty-four hours of culture increased the percentage of migrating PBT and LT (blood 17·5 ± 2·9% and lung 17·7 ± 3·8%). The IL-2 stimulation modestly increased migration of PBT after 6 days (32·3 ± 6·0%), but had no effect on the migration of LT (25·5 ± 3·2%). Twenty-four hours of stimulation with anti-CD3/CD28 caused a small but significant increase in the migration of PBT (to 36·4 ± 5·8%). In a directional three-dimensional assay, CXCL12 failed to induce migration of fresh PBT or LT. Twenty-four hours of culture, which increased CXCR4 expression of PBT 3·6-fold, significantly increased the migration of PBT in response to CXCL12. Migration of PBT to CXCL12 was blocked by pertussis toxin, but not by the phosphoinositide 3-kinase inhibitor wortmannin. Twenty-four-hour cultured LT did not respond to CXCL12. CD3/CD28-stimulation inhibited CXCL12-mediated migration of PBT. These results suggest that the migration pattern of PBT is distinct from that of LT. [source] Synthesis and properties of poly(butylene terephthalate)/multiwalled carbon nanotube nanocomposites prepared by in situ polymerization and in situ compatibilizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Fangjuan Wu Abstract A novel cyclic initiator was synthesized from dibutyl tin(IV) oxide and hydroxyl-functionalized multiwalled carbon nanotubes (MWNTs) and was used to initiate the ring-opening polymerization of cyclic butylene terephthalate oligomers to prepare poly(butylene terephthalate) (PBT)/MWNT nanocomposites. The results of Fourier transform infrared and NMR spectroscopy confirmed that a graft structure of PBT on the MWNTs was formed during the in situ polymerization; this structure acted as an in situ compatibilizer in the nanocomposites. The PBT covalently attached to the MWNT surface enhanced the interface adhesion between the MWNTs and PBT matrix and, thus, improved the compatibility. The morphologies of the nanocomposites were observed by field emission scanning electron microscopy and transmission electron microscopy, which showed that the nanotubes were homogeneously dispersed in the PBT matrix when the MWNT content was lower than 0.75 wt %. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermal properties of the nanocomposites. The results indicate that the MWNTs acted as nucleation sites in the matrix, and the efficiency of nucleation was closely related to the dispersion of the MWNTs in the matrix. Additionally, the thermal stability of PBT was improved by the addition of the MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Poly(butylene terephthalate)/clay nanocomposite compatibilized with poly(ethylene- co -glycidyl methacrylate).JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Abstract Poly(butylene terephthalate) (PBT)/clay nanocomposite was prepared by blending PBT and commercial modified montmorillonite clays via a extruder by using poly(ethylene- co -glycidyl methacrylate) (PEGMA) as a compatibilizer (PBT/PEGMA/Clay). PEGMA and clay were also blended with PBT to prepare PBT/PEGMA and PBT/Clay, respectively. The morphology was investigated by wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The clays were aggregated together and phase separation was observed in PBT/Clay. The clays were exfoliated in PBT/PEGMA/Clay. The equilibrium melting temperature was estimated by linear and nonlinear Hoffman-Weeks relation. The influence of the PEGMA and clay on the PBT crystallizable ability was also investigated by Avrami model and undercooling (difference between crystallization and equilibrium melting temperature). Hoffman-Lauritzen relation was used to estimate chain fold surface free energy. The exfoliated silicates cause a large number nucleus center to enhance the crystallization in PBT/PEGMA/Clay. The presence of PEGMA can react with the PBT and an increase in viscosity would reduce molecular mobility and crystallization in PBT/PEGMA. The aggregated clays have a confinement effect on the segmental motion of PBT and hinder the crystallization in PBT/Clay. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Shear-induced migration of nanoclay during morphology evolution of PBT/PS blendJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Joung Sook Hong Abstract In this study, we investigated clay migration and its localization in multiphase blend nanocomposite systems during the evolution of blend morphology to elucidate how a hydrodynamic stress and chemical affinity between the polymer and clay induce them. To observe the morphology evolution, a multilayered blend, alternatively superposed poly(butylenes terephthalate) (PBT) and polystyrene (PS)/clay films or PBT/clay and PS films, was subjected to homogeneous shear flow, 1 s,1. Furthermore, the morphology was observed at different shear rates 1 s,1. When the PBT/(PS/clay) multilayered blend is subjected to flow, the clay dispersed in the PS layer first migrates to the interface depending on the amount of applied strain. The clay at the interface causes the average drop size of blend morphology to become smaller and the blend morphology becomes more stable because of the coalescence suppression effect. As more shear is applied, the clay at the interface moves further into more compatible phase, PBT, although the viscosity of PBT is higher than PS. On the contrary, the clay in the PBT layer does not migrate to the PS phase at any shear rate, which means that its chemical affinity is strong enough to prevent shear-induced migration. The clay increases the viscosity of the PBT phase and results in a different morphology with a droplet, cocontinuous structure. As a result, when the clay is induced to migrate by hydrodynamic stress, it migrates into thermodynamically more stable positions at the interface or in the chemically more compatible phase, depending on the applied strain. Once it is located at a thermodynamically more stable position, it is difficult to push it out only by hydrodynamic stress. The location of clay is significantly affected by the morphology during evolution, which means that the blend morphology can control the droplet form and cocontinuous structure by control of the clay migration kinetics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Crystallization of poly(butylene terephthalate)/poly(ethylene octene) blends: Nonisothermal crystallizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Jiann-Wen Huang Abstract Poly(ethylene octene) (POE), maleic anhydride grafted poly(ethylene octene) (mPOE), and a mixture of POE and mPOE were added to poly(butylene terephthalate) (PBT) to prepare PBT/POE (20 wt % POE), PBT/mPOE (20 wt % mPOE), and PBT/mPOE/POE (10 wt % mPOE and 10 wt % POE) blends with an extruder. The melting behavior of neat PBT and its blends nonisothermally crystallized from the melt was investigated with differential scanning calorimetry (DSC). Subsequent DSC scans exhibited two melting endotherms (TmI and TmII). TmI was attributed to the melting of the crystals grown by normal primary crystallization, and TmII was due to the melting of the more perfect crystals after reorganization during the DSC heating scan. The better dispersed second phases and higher cooling rate made the crystals that grew in normal primary crystallization less perfect and relatively prone to be organized during the DSC scan. The effects of POE and mPOE on the nonisothermal crystallization process were delineated by kinetic models. The dispersed phase hindered the crystallization; however, the well- dispersed phases of an even smaller size enhanced crystallization because of the higher nucleation density. The nucleation parameter, estimated from the modified Lauritzen,Hoffman equation, showed the same results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effect of molecular relaxation of acrylic elastomers on impact toughening of polybutylene terephthlateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Nafih Mekhilef Abstract In this study, we examined the performance of two core-shell acrylic-based impact modifiers (AIM) prepared by emulsion polymerization. The rubber core was prepared from ethyl hexyl acrylate (EHA) and n -octyl acrylate (n -OA). In such as process, the particle size and particle-size distribution of the modifiers were precisely controlled, so that performance differences observed in polybutylene terephthlate (PBT), used as matrix resin, could only be interpreted in terms of the nature of the elastomeric component of the modifiers. When isolated, the rubber core of the modifiers showed identical glass transition temperatures (Tg) by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) despite the fact that they were made from two different acrylic monomers. Temperature-frequency superposition principle inferred from the classical WLF equation showed that the rubber components exhibit the same Tg at all frequencies including at the time scale at which mechanical impact typically occurs. However, significant differences in low temperature impact performance measured at ,30°C using notched Izod impact test according to ASTM D 256 were obtained even though their rubber components had identical Tg. Such differences were attributed to the dynamic relaxation behavior of the rubber components and identified as inherent properties of the elastomers due to the structure of the monomers' repeat units. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Synthesis and characterization of poly(butylene terephthalate)/mica nanocomposite fibers via in situ interlayer polymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Jin-Hae Chang Abstract Intercalated nanocomposites consisting of poly(butylene terephthalate) (PBT) incorporated between mica layers were synthesized from dimethyl terephthalate (DMT) and 1,4-butanediol (BD) by in situ interlayer polymerization. PBT nanocomposites of varying organoclay content were melt-spun to produce monofilaments. The samples were characterized using wide angle X-ray diffraction, electron microscopy, thermal analysis, and tensile testing. Some of the clay particles were found to be well dispersed in the PBT matrix, but other clay particles were agglomerated at a size level greater than approximately 20 nm. The glass transition temperatures (Tg) and the thermal degradation properties (TDi) of undrawn PBT hybrid fibers were found to improve with increases in the clay content. At draw ratio (DR) = 1, the ultimate tensile strengths of the hybrid fibers increased with the addition of clay up to a critical content and then decreased. However, the initial moduli monotonically increased with increases in the amount of organoclay in the PBT matrix. The ultimate strengths were found to decrease linearly with increases in DR from 1 to 18. In contrast to the trend for the tensile strengths, the initial moduli of the hybrid fibers increased only slightly with increases in DR up to 18. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Design of a high-efficiency hydrofoil through the use of computational fluid dynamics and multiobjective optimizationAICHE JOURNAL, Issue 7 2009N. Spogis Abstract A computational fluid dynamics (CFD) model is proposed, based on ANSYS-CFX tools coupled to optimization models inside the commercial optimization software modeFRONTIER in order to obtain an optimal design of a high-efficiency impeller for solids suspension. The analysis of impeller shape performance was carried out using the shear-stress transport (SST) turbulence model with streamline curvature correction. This turbulence model combined the advantages of the ,,, and ,,, models, ensuring a proper relation between turbulent stress and turbulent kinetic energy, allowing an accurate and robust prediction of the impeller blade flow separation. The multiple frames of reference and the frozen rotor frame change models were used for the rotor/stator interaction inside the mixing vessel. The optimization procedure used seven design variables, two nonlinear constraints and two objective functions. The objective functions chosen (among many other possible options) to evaluate the impeller performance were the maximum solid distribution throughout the vessel (homogeneous suspension) reflected by a low variance between local solid concentration and average solid concentration inside the vessel and the higher pumping effectiveness, which was defined as the quotient of the flow and power numbers. The first objective function searches for impeller configurations able to provide good solid suspension, since it aims to achieve homogeneous suspension. The second objective function aims to reduce power consumption for a high-pumping capacity of the impeller. These criteria were considered enough to characterize the optimized impeller. Results indicated that the optimized impeller presented an increase of the pumping impeller capacity and homogeneous solid suspension with low-power consumption, especially when compared with the PBT 45° impeller. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The incorporation of rigid diol monomers into poly(butylene terephthalate) via solid-state copolymerization and melt copolymerization,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2008M. A. G. Jansen Abstract Incorporation of 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane (Dianol 220®) into poly(butylene terephthalate) (PBT) via solid-state copolymerization (SSP) showed that Dianol, besides being the reactant, also acts as a swelling agent for rigid amorphous PBT chain segments. Being swollen, these amorphous chain segments become sufficiently mobile to contribute to the SSP process. The thermal behavior of the resulting copolyesters is comparable with melt copolymerized copolymers, although having a different chemical microstructure. The main reason is a full miscibility in the melt of unmodified PBT chain segments and modified chain segments, which eliminates the advantages of a blocky microstructure for the SSP copolyesters. However, incorporation of 2,2,-biphenyldimethanol (BDM) into PBT resulted in a higher crystallization temperature compared with PBT,Dianol copolymers of equal composition. Preordering of polymer chains in the melt by incorporating rigid, phase separating BDM-moieties, preferably via SSP to obtain a non-random distribution, may be the origin of the enhanced crystallization temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1203,1217, 2008 [source] Preparation and characterization of poly(butylene terephthalate)/poly(ethylene terephthalate) copolymers via solid-state and melt polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2007M. A. G. Jansen Abstract To increase the Tg in combination with a retained crystallization rate, bis(2-hydroxyethyl)terephthalate (BHET) was incorporated into poly(butylene terephthalate) (PBT) via solid-state copolymerization (SSP). The incorporated BHET fraction depends on the miscibility of BHET in the amorphous phase of PBT prior to SSP. DSC measurements showed that BHET is only partially miscible. During SSP, the miscible BHET fraction reacts via transesterification reactions with the mobile amorphous PBT segments. The immiscible BHET fraction reacts by self-condensation, resulting in the formation of poly(ethylene terephthalate) (PET) homopolymer. 1H-NMR sequence distribution analysis showed that self-condensation of BHET proceeded faster than the transesterification with PBT. SAXS measurements showed an increase in the long period with increasing fraction BHET present in the mixtures used for SSP followed by a decrease due to the formation of small PET crystals. DSC confirmed the presence of separate PET crystals. Furthermore, the incorporation of BHET via SSP resulted in PBT-PET copolymers with an increased Tg compared to PBT. However, these copolymers showed a poorer crystallization behavior. The modified copolymer chain segments are apparently fully miscible with the unmodified PBT chains in the molten state. Consequently, the crystal growth process is retarded resulting in a decreased crystallization rate and crystallinity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 882,899, 2007. [source] Silicone-based impact modifiers for poly(vinyl chloride), engineering resins, and blendsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2004Akira Yanagase Abstract Silicone-based impact modifiers were prepared in a previous study. The modifiers were composed of silicone/acrylic rubber cores and grafted acrylic shells. They improved the toughness of poly(vinyl chloride) (PVC) and poly(methyl methacrylate). The silicone emulsion that was used to produce the silicone-based impact modifiers was prepared via two routes: emulsion polymerization and bulk polymerization of octamethyltetracyclosiloxane. Many silicone-based impact modifiers were produced that had different silicone/acrylic rubber characteristics. Through a toughness examination of modified PVC, the best composition of the silicone-based impact modifiers was obtained, and the silicone content in the rubber composition was 25 wt %. The morphology of the silicone-based impact modifiers, determined by transmission electron microscopy, was as follows: core and second shell polymers were mainly poly(butyl acrylate), and the first shell polymer was silicone. The silicone-based impact modifiers were blended with engineering resins such as PVC, polycarbonate (PC), poly(butylene terephthalate) (PBT), and PC/PBT mixtures. The impact strength under standard conditions and after weathering test conditions for blends of the silicone-based impact modifiers were investigated with respect to two commercially available acrylic and methyl methacrylate/butadiene/styrene impact modifiers. The results showed good weatherability and good toughness under low-temperature conditions for the silicone-based impact modifiers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1112,1119, 2004 [source] Investigation of Soft Component Mobility in Thermoplastic Elastomers using Homo- and Heteronuclear Dipolar Filtered 1H Double Quantum NMR ExperimentsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2004Marko Bertmer Abstract Summary: Information about segmental mobility in thermoplastic elastomers was obtained using static 1H double quantum (DQ) NMR experiments in combination with homo- and heteronuclear dipolar filters, e.g. 13C editing of 1H DQ buildup curves. Block copolymers of poly(butylene terephthalate) (PBT) as hard blocks and poly(tetramethylene oxide) (PTMO) as soft blocks (PBT- block -PTMO) were investigated by varying composition and block length. By simulation of the DQ buildup curves, residual dipolar couplings and with this the average order parameter were deduced for the mobile PTMO blocks which are sensitive to the segmental mobility responsible for the viscoelastic properties of thermoplastic elastomers. A strong correlation exists between residual dipolar coupling and composition. Furthermore, the average order parameter correlates linearly with the amount of PTMO in a PTMO-rich phase as determined in previous studies. Additionally, 1H transverse magnetization relaxation measurements revealed a direct correlation between the effective T2 relaxation time of the soft domain and the composition of the thermoplastic elastomers. Correlation of the average order parameter vs. the fraction of PTMO in the PTMO-rich phase. [source] Deformation Behavior of PET, PBT and PBT-Based Thermoplastic Elastomers as Revealed by SAXS from SynchrotronMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2003Norbert Stribeck Abstract The present paper discloses the changes in the nanostructure as revealed by small-angle X-ray scattering (SAXS) of synchrotron radiation of anisotropic semi-crystalline samples of polyester and poly(ether ester) type differing in their chemical composition, while subjected to controlled progressive elongation. From the group of polyesters poly(ethylene terephthalate) (PET), and poly(butylene terephthalate) (PBT) were selected. Two PBT-based commercial poly(ether ester)s were also studied differing in the molecular weight of their soft segments (poly(tetramethylene glycol), PTMG) being 1000 and 2000, respectively. A blend of PBT and EM550 (40/60 by wt.) was also characterized. All materials underwent the same sample preparation process resulting in highly oriented "bristles" of 1 mm diameter. It was found that ,b, the elongation at break, strongly depends on the flexibility of the glycol residues of the materials studied , ranging from ,b,=,8% for PET that contains ethylene glycol residues, through ,b,=,18% for PBT including the more flexible tetramethylene glycol (TMG) up to ,b,=,510% for the PEE containing the longest PTMG moieties. During straining the relationship between the external elongation , and the changes in the long spacing L was determined. After relaxation from each deformation step the relationship between the tensile set ,r and the long period L was also followed and discussed. Such analysis led to a model describing the nanostructure evolution during the deformation-relaxation cycle that finally was verified and refined utilizing the multidimensional chord distribution function computed from the anisotropic SAXS patterns. 2D SAXS patterns (pseudo color) of bristles of PET (PBT), respectively, cold drawn, ,,=,3.5 (,,=,2.3) and annealed with fixed ends for 6 h at 240,°C (180,°C), recorded at room temperature at a forced tensile deformation , or tensile set (residual elongation) ,r in percent. [source] On Toughness and Stiffness of Poly(butylene terephthalate) with Epoxide-Containing Elastomer by Reactive ExtrusionMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2004Zhong-Zhen Yu Abstract Summary: To obtain a balance between toughness (as measured by notched impact strength) and elastic stiffness of poly(butylene terephthalate) (PBT), a small amount of tetra-functional epoxy monomer was incorporated into PBT/[ethylene/methyl acrylate/glycidyl methacrylate terpolymer (E-MA-GMA)] blends during the reactive extrusion process. The effectiveness of toughening by E-MA-GMA and the effect of the epoxy monomer were investigated. It was found that E-MA-GMA was finely dispersed in PBT matrix, whose toughness was significantly enhanced, but the stiffness decreased linearly, with increasing E-MA-GMA content. Addition of 0.2 phr epoxy monomer was noted to further improve the dispersion of E-MA-GMA particles by increasing the viscosity of the PBT matrix. While use of epoxy monomer had little influence on the notched impact strength of the blends, there was a distinct increase in the elastic stiffness. SEM micrographs of impact-fracture surfaces indicated that extensive matrix shear yielding was the main impact energy dissipation mechanism in both types of blends, with or without epoxy monomer, and containing 20 wt.-% or more elastomer. SEM micrographs of freeze-fractured surfaces of PBT/E-MA-GMA blend illustrating the finer dispersion of E-MA-GMA in the presence of epoxy monomer. [source] Microwave dielectric properties of polybutylene terephtalate (PBT) with carbon black particlesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2005L. C. Costa Abstract The synthesis of composites based on polymers containing carbon as additives is rather relevant because it has been found that applications in several industries are increasing, particularly due to their unusual mechanical and electrical properties. By choosing the adequate doping concentrations, we can precisely control the electrical properties in the microwave frequencies, in order to tailor the desired behavior. In this study, we present the results of the complex-permittivity measurements, ,* = ,, , í ,,, at 2.7, 5, and 12.8 GHz, on polybutylene terephtalate (PBT), with different concentration of black carbon particles, using the resonant-cavity method. Measuring the shift in the resonant frequency of the cavity, ,f, caused by the insertion of the sample, we can calculate to the real part of the complex permittivity, ,,, while the measure of the change in the inverse of the quality factor of the cavity, ,(1/Q), allow us to calculate the imaginary part, ,,. Maxwell,Wagner,Sillars (MWS) and Looyenga mixture laws are applied to the obtained results. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 61,63, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20901 [source] Separation and quantification of the cellular thiol pool of pea plants treated with heat, salt and atrazinePHYTOCHEMICAL ANALYSIS, Issue 4 2007Sergei Veselinov Ivanov Abstract A novel procedure for the separation of the cellular thiol pool according to the molecular weight and localization of compounds with sulphydryl groups is presented. This simple and rapid method allows the differentiation of thiols into three major fractions,low molecular weight (LMT, primarily glutathione and free cysteine), protein-bound (TPT) and pellet-bound (PBT, associated with cell walls and broken organelles). Moreover, determination of the ratio between surface (readily reactive) thiols (ATG) and those that are more or less buried in the protein structure (BTG) can be achieved. In intact pea leaves, the amounts of the total thiols (LMT + PBT + TPT) varies from 2.5 to 4.8 µmol/g of fresh material. The data for LMT, PBT and TPT were related to each other in the approximate ratio 1:2:7. Treatments of pea plants with high temperature, salinity and low amounts of atrazine affect these sulphydryl types differently. For a greater understanding of the applicability of this method to physiological research, the main mechanisms leading to alterations in the cellular thiol pool are discussed. Furthermore, it is suggested that the proportion of available to buried thiols (ATG/BTG) in proteins could be used as a convenient marker for stress impacts. Copyright © 2007 John Wiley & Sons, Ltd. [source] In situ reinforcement of poly(butylene terephthalate) and butyl rubber by liquid crystalline polymerPOLYMER COMPOSITES, Issue 5 2009S. Kumar Ternary in situ butyl rubber (IIR)/poly(butylene terephthalate) (PBT) and liquid crystalline polymer (LCP) blends were prepared by compression molding. The LCP used was a versatile Vectra A950, and the matrix material was IIR/PBT 50/50 by weight. Morphological, thermal, and mechanical properties of blends were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry, and thermogravimetric analysis (TGA). Microscopy study (SEM) showed that formation of fibers is increasing with the increasing amount of LCP A950. Microscopic examination of the fractured surface confirmed the presence of a polymer coating on LCP fibrils. This can be attributed to some interactions including both chemical and physical one. The increased compatibility in polymer blends, consisting of IIR/PBT, by the presence of LCP A950 may be explained by the adsorption phenomena of the polymer chains onto the LCP fibrils. SEM and AFM images provided the evidence of the interaction between IIR/PBT and the LCP. Dynamic mechanical analyses (DMA) and TGA measurements showed that the composites possessed a remarkably higher modulus and heat stability than the unfilled system. Storage modulus for the ternary blend containing 50 wt% of LCP exhibits about 94% increment compared with binary blend of IIR/PBT. From the above results, it is suggested that the LCP A950 can act as reinforcement agent in the blends. Moreover, the fine dispersion of LCP was observed with no extensional forces applied during mixing, indicating the importance of interfacial adhesion for the fibril formation. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Valorization of poly(butylene terephthalate) wastes by blending with virgin polypropylene: Effect of the composition and the compatibilizationPOLYMER ENGINEERING & SCIENCE, Issue 8 2008Najoua Barhoumi Blends of recycled poly(butylene terephthalate) (PBT) parts obtained from scrapped cars, and virgin polypropylene (PP), were prepared in a twin-screw extruder at different compositions. Selected compositions were also prepared with the presence of ethylene- co -glycidyl methacrylate copolymer (E-GMA) and ethylene/methyl acrylate/glycidyl methacrylate terpolymer (E-MA-GMA) compatibilizers. The effect of the composition and the type of compatibilizer, as well as the mixing conditions, on the morphology phase, thermal, viscoelastic behavior, and mechanical properties of the blends has been investigated. Blends PP/PBT of various composition exhibit a coarse morphology and a poor adherence between both phases, resulting in the decrease of ductility, whereas at weak deformation, PBT reinforced the tensile properties of PP. Addition of E-GMA and E-MA-GMA to the PP/PBT blend exhibited a significant change in morphology and improved ductility because of interfacial reactions between PBT end chains and epoxy groups of GMA that generate EG- g -PBT copolymer. Moreover, thermal and viscoelastic study indicated that the miscibility of PP and PBT has been improved further and the reactions were identified. The E-MA-GMA results in the best improvement of ductility. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Crystallization and thermal behavior of multiwalled carbon nanotube/poly(butylenes terephthalate) compositesPOLYMER ENGINEERING & SCIENCE, Issue 6 2008Defeng Wu Multiwalled carbon nanotube/poly(butylene terephthalate) composites (PCTs) were prepared by melt mixing. The nonisothermal crystallization and thermal behavior of PCTs were respectively investigated by X-ray diffractometer, polarized optical microscope, differential scanning calorimeter, dynamic mechanical thermal analyzer, and thermogravimetric analyzer. The presence of nanotubes has two disparate effects on the crystallization of PBT: the nucleation effect promotes kinetics, while the impeding effect reduces the chain mobility and retards crystallization. The kinetics was then analyzed using Ozawa, Mo, Kissinger, Lauritzen-Hoffman, and Ziabicki model, and the results reveal that the nucleation effect is always the dominant role on the crystallization of PBT matrix. Thus the crystallizability increases with increase of nanotube loadings. In addition, the presence of nanotubes nearly has no remarkable contribution to thermal stability because nanotubes also play two disparate roles on the degradation of PBT matrix: the Lewis acid sites to facilitate decomposition and the physical hindrance to retard decomposition. Hence the nanotubes act merely as inert-like filler to thermal stability. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Effect of mold temperature on the long-term viscoelastic behavior of polybutylene terepthalatePOLYMER ENGINEERING & SCIENCE, Issue 5 2008K. Banik The effect of mold temperature variation during injection molding on the long-term viscoelastic behavior of polybutylene terepthalate (PBT) was studied by dynamic mechanical thermal analysis (DMTA) and flexural creep tests. The time,temperature superposition (TTS) principle was applied to the experimental data and the master curves were created to predict their long-term behavior. The WLF and Arrhenius models were verified for the shift data in the investigating temperature range and the activation energies for the deformation process were calculated based on the Arrhenius equation. Further a four-element Burger model was applied to the creep results to represent the creep behavior of the PBT processed at two different mold temperatures and to better understand the deformation mechanism. Differential scanning calorimetry (DSC) and density measurements were accomplished to characterize the process-dependent microstructures. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Poly(butylene terephthalate)/poly(,-caprolactone) blends: Miscibility and thermal and mechanical propertiesPOLYMER ENGINEERING & SCIENCE, Issue 3 2007Maria Laura Di Lorenzo Miscibility and thermal and mechanical properties of poly(butylene terephthalate) (PBT) blends with poly(,-caprolactone) (PCL) were analyzed as a function of the molecular mass of PCL. It was found that the components are miscible when oligomeric PCL is blended with PBT, probably due to favorable interactions between OH end groups of poly(,-caprolactone) and ester groups of PBT. In the blends containing high molar mass PCL, the concentration of hydroxyl end groups is lower, allowing only partial miscibility of the components. The resulting materials display good mechanical properties, with enhanced performance at rupture compared to plain PBT. POLYM. ENG. SCI., 47:323,329, 2007. © 2007 Society of Plastics Engineers. [source] Preparation and characterization of PBT nanocomposites compounded with different montmorillonitesPOLYMER ENGINEERING & SCIENCE, Issue 6 2004Domenico Acierno Because of their superior mechanical and thermal properties, light weight, and favorable cost/performance ratio, nanocomposite materials appear to be suitable replacements for metals and alloys in many industrial applications in fields such as automotive, structural plastics, electronics, packaging, and so on (1). The technological relevance of this large-scale market for polymers is evidenced by the numerous patents issued over the last few years, even though only few applications have entered the market. Polymer-clay nanocomposite systems were successfully prepared by melt compounding using several thermoplastic matrices (polyamides, polyolefins, etc.), but few data are reported in the scientific literature on polyester-based nanocomposites (2). Because of the high commercial relevance of polyesters, we have investigated the effect of organoclay inclusion on the structure and properties of these hybrid systems. In particular, we have studied the relationships between processing conditions, hybrid composition (organoclay type and content), nanoscale morphology and properties of poly(butylene terephthalate) (PBT) nanocomposites based upon several commercial organo-modified montmorillonites at different weight percentages. The melt compounding was performed using a twin-screw extruder, at extrusion rates of 90 or 150 rpm. Polym. Eng. Sci. 44:1012,1018, 2004. © 2004 Society of Plastics Engineers. [source] Crystallization kinetics of poly(trimethylene terephthalate)POLYMER ENGINEERING & SCIENCE, Issue 2 2001Hoe H. Chuah The bulk isothermal crystallization kinetics of poly(trimethylene terephthalate) (PTT) was studied using a differential scanning calorimeter. Avrami's theory was used to analyze the data. Based on crystallinity growth rate, Avrami rate constant, K, and crystallization half-time, PTT's crystallization rate is between those of poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) when compared at the same degree of undercooling. PBT has the highest crystallization rate with K in the order of 10,2 to 10,1 min,n. It is about an order of magnitude faster than PTT at 10,3 to 10,2 min,n, which in turn is an order of magnitude faster than PET with K of 10,4 to 10,2 min,n. Contrary to previous reports (PTT was not included in the study) that aromatic polyesters with odd numbers of methylene units were more difficult to crystallize than the even-numbered polyesters, PTT did not fit in the prediction and did not follow the odd-even effect. [source] Preparation and characterization of biaxially oriented films from polybutylene terephthalate based thermoplastic elastomer block copolymersPOLYMER ENGINEERING & SCIENCE, Issue 11 2000Hang Li Film casting and biaxial stretching of a series of polyester thermoplastic elastomers (TPEs) were studied. Biaxial orientation in the stretched films was characterized by wide-angle X-ray diffraction and birefringence measurements. Biaxial orientation factors were determined. The X-ray diffraction and birefringence clearly indicated the development of planar biaxial orientation in the stretched films with biaxial stretching. The phenyl groups in the stretched PBT and TPE films gradually became more parallel to the film surfaces with increasing biaxial orientation. The lower the PBT content in the stretched TPE films, the lower the planar biaxial orientation achieved. The , form of crystalline PBT was found only in the stretched PBT films, but not in the TPE films. [source] Copolymers based on poly(butylene terephthalate) and polycaprolactone- block -polydimethylsiloxane- block -polycaprolactonePOLYMER INTERNATIONAL, Issue 6 2010Vesna V Anti Abstract A series of novel thermoplastic elastomers, based on poly(butylene terephthalate) (PBT) and polycaprolactone- block -polydimethylsiloxane- block -polycaprolactone (PCL-PDMS-PCL), with various mass fractions, were synthesized through melt polycondensation. In the synthesis of the poly(ester-siloxane)s, the PCL blocks served as a compatibilizer for the non-polar PDMS blocks and the polar comonomers dimethyl terephthalate and 1,4-butanediol. The introduction of PCL-PDMS-PCL soft segments resulted in an improvement of the miscibility of the reaction mixture and therefore in higher molecular weight polymers. The content of hard PBT segments in the polymer chains was varied from 10 to 80 mass%. The degree of crystallinity of the poly(ester-siloxane)s was determined using differential scanning calorimetry and wide-angle X-ray scattering. The introduction of PCL-PDMS-PCL soft segments into the polymer main chains reduced the crystallinity of the hard segments and altered related properties such as melting temperature and storage modulus, and also modified the surface properties. The thermal stability of the poly(ester-siloxane)s was higher than that of the PBT homopolymer. The inclusion of the siloxane prepolymer with terminal PCL into the macromolecular chains increased the molecular weight of the copolymers, the homogeneity of the samples in terms of composition and structure and the thermal stability. It also resulted in mechanical properties which could be tailored. Copyright © 2010 Society of Chemical Industry [source] Toughening effects of poly(butylene terephthalate) with blocked isocyanate-functionalized poly(ethylene octene)POLYMER INTERNATIONAL, Issue 8 2009Ligang Yin Abstract BACKGROUND: Blocked isocyanate-functionalized polyolefins have great potential for use in semicrystalline polymer blends to obtain toughened polymers. In this study, poly(butylene terephthalate) (PBT) was blended with allyl N -[2-methyl-4-(2-oxohexahydroazepine-1-carboxamido)phenyl] carbamate-functionalized poly(ethylene octene) (POE- g -AMPC). RESULTS: New peaks at 2272 and 1720 cm,1, corresponding to the stretching vibrations of NCO and the carbonyl of NHCON, respectively, in AMPC, appeared in the infrared spectrum of POE- g -AMPC. Both rheological and X-ray photoelectron spectroscopy results indicated a new copolymer was formed in the reactive blends. Compared to uncompatibilized PBT/POE blends, smaller dispersed particle sizes with narrower distribution were found in the compatibilized PBT/POE- g -AMPC blends. There was a marked increase in impact strength by about 10-fold over that of PBT/POE blends with the same rubber content and almost 30-fold higher than that of pure PBT when the POE- g -AMPC content was 25 wt%. CONCLUSION: The blocked isocyanate-functionalized POE is an effective toughener for semicrystalline polymers. Super-toughened PBT blends can be obtained when the POE- g -AMPC content is equal to or more than 15 wt%. Copyright © 2009 Society of Chemical Industry [source] Supramolecular selectivity of poly(ethylene oxide) in semi-crystalline polymer nanocompositesPOLYMER INTERNATIONAL, Issue 12 2007Li Zhou Abstract Semi-crystalline polymer nanocomposites were prepared using successive meltings and recrystallizations techniques by intercalation of small guest molecules such as 4-chlorotoluene (PCT), 4-bromotoluene (PBT) and 1,4-dibromobenzene (PDBB) into poly(ethylene oxide) (PEO) crystals. Differential scanning calorimetry, Fourier transform infrared spectroscopy and wide-angle X-ray diffraction experimental results show that supramolecular selectivity exists for the PEO,PDBB/PBT ternary system, while there is no supramolecular selectivity for PEO,PCT/PBT ternary nanocomposites. The interactions between PEO chains and small guest molecules have an important influence on the polymer conformation, which results in the dramatic difference in intercalation behavior. 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