High PBT Research Articles

The occurrence, tissue distribution, and PBT potential of per- and polyfluoroalkyl substances in the freshwater organisms from the Yangtze river via nontarget analysis

Numerous emerging per- and polyfluoroalkyl substances (PFASs) occur in the aquatic environment, posing a threat to aquatic ecosystems and human health. In this study, we conducted a nontarget analysis on 3 surface water samples and 92 tissue samples of 16 fish collected from the Yangtze River to investigate the patterns, tissue distribution, and environmental impacts of emerging PFASs. A total of 43 PFASs from 11 classes were identified, including 17 legacy PFASs and 26 emerging PFASs. Among the 43 PFASs, seven PFASs were reported in biota for the first time while five PFASs were reported in the environment for the first time. Chlorine substituted perfluoroalyl ether sulfonic acids were the major emerging PFASs detected in organisms. Our results showed that most emerging PFASs tended to accumulate in the liver whereas perfluorinated sulfonamides tended to accumulate in the blood, and all of the emerging PFASs accumulated less in the muscle. Methods for evaluating the persistence, bioaccumulation, and toxicity (PBT) of PFASs were developed by combining the in-silico methods and experimental methods. Long-chain PFASs were found to have extremely high PBT scores compared to short-chain PFASs. Additionally, most emerging PFASs exhibited comparable PBT characteristics with legacy PFASs, especially Cl-substituted PFASs.

PBT/adipic acid modified PEG solid-solid phase change composites

The complicated preparation process and difficulty of recycling were serious obstacles to the widespread use of solid-solid phase change materials (PCMs). Herein, we reported a novel thermoplastic solid-solid PCMs prepared by a facile one-step feeding method. In this study, the esterification and transesterification among the molten mixture of PBT, PEG and adipic acid were conducted to prepare thermoplastic PEG/PBT/Adipic acid copolymer-based PCMs. Adipic acid, as an auxiliary encapsulation agent, could prevent effectively PEG leakage of PEG/PBT/Adipic acid copolymer-based PCMs with high PEG and low PBT content during the phase change process. For PCM-6 containing 91 wt% PEG, 8 wt% PBT and 1 wt% adipic acid, there were no changes in the shape and chemical structure after multiple thermal cycles. The TG results presented that the initial thermal degradation temperature of PCMs-6 was above 200 °C, which was much higher than the processing and working temperature of PCMs-6. The latent heat of PCMs-6 could reach 136.8 J/g, showing great potential for energy storage, especially in the field of green buildings.

Effect of PBT molecular weight and reactive compatibilization on the dispersed‐phase coalescence of PBT/SAN blends

AbstractPoly(butylene terephthalate) (PBT)/styrene‐acrylonitrile copolymer (SAN) blends were investigated with respect to their phase morphology. The SAN component was kept as dispersed phase and PBT as matrix phase and the PBT/SAN viscosity ratio was changed by using different PBT molecular weights. PBT/SAN blends were also compatibilized by adding methyl methacrylate‐co‐glycidyl methacrylate‐co‐ethyl acrylate terpolymer, MGE, which is an in situ reactive compatibilizer for melt blending. In noncompatibilized blends, the dispersed phase particle size increased with SAN concentration due to coalescence effects. Static coalescence experiments showed evidence of greater coalescence in blends with higher viscosity ratios. For noncompatibilized PBT/SAN/MGE blends with high molecular weight PBT as matrix phase, the average particle size of SAN phase does not depend on the SAN concentration in the blends. However noncompatibilized blends with low molecular weight PBT showed a significant increase in SAN particle size with the SAN concentration. The effect of MGE epoxy content and MGE molecular weight on the morphology of the PBT/SAN blend was also investigated. As the MGE epoxy content increased, the average particle size of SAN initially decreased with both high and low molecular weight PBT phase, thereafter leveling off with a critical content of epoxy groups in the blend. This critical content was higher in the blends containing low molecular weight PBT than in those with high molecular weight PBT. At a fixed MGE epoxy content, a decrease in MGE molecular weight yielded PBT/SAN blends with dispersed nanoparticles with an average size of about 40 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010

Tooth Element Levels Indicating Exposure Profiles in Diabetic and Hypertensive Subjects from Mysore, India

Element contents of teeth elucidate exposure nature, but less is known about association of tooth element concentrations of diabetics and hypertensives with exposure profile. Present study aims to estimate copper, chromium, iron, zinc, nickel, and lead concentrations in the permanent teeth of control, diabetic, and hypertensive subjects from Mysore. The results show that lead levels of teeth (Pb-T) are higher in the hypertensives and diabetics, whereas copper levels of teeth (Cu-T) are lower in the hypertensives and users of stainless steel utensils than that of controls and users of mixed utensils. The elevated Cu-T levels found in the users of mixed utensils that being made of several metals are ascribed to leaching effect of sour and spicy food of Indian cuisine. The element levels were influenced by diet (Zn-T), place of living, sex and income (Pb-T) of the subjects, but not by age, drinking water from different sources, and certain habits viz., smoking, alcohol consumption, chewing betel, and nut. Thus, it is evident that high Pb-T and low Cu-T levels may be related with diabetes and hypertension and high Pb-T and Cu-T levels, respectively, in the urbanites, and the users of mixed utensils may show different exposure profiles from environment and utensils.

Conjugated effects of the compatibilization and the dynamic vulcanization on the phase inversion behavior in poly(butylene terephthalate)/epoxide-containing rubber reactive polymer blends

The conjugated effects of both reactive compatibilization and dynamic vulcanization on the phase inversion behavior of poly(butylene terephthalate) (PBT)/epoxide-containing rubber blends have been studied in detail. Pure ethylene–methyl acrylate random copolymer (E-MA) and ethylene–methyl acrylate–glycidyl methacrylate random terpolymer (E–MA–GMA) were used as non reactive or reactive rubber phase, respectively. Location of the phase inversion region was studied using several techniques, including transmission electron microscopy (TEM) and dynamical mechanical thermal analysis (DMTA). To evaluate the relative influence of the blend compatibilization and the dynamic vulcanization on the phase inversion behavior, the relative kinetics of the two reactions were modified using different PBT and E–MA–GMA grades. The obtained results show unambiguously that the position and the width of the phase inversion region is essentially governed by the kinetic of the dynamic vulcanization process. The effect of the blend compatibilization remains quite limited even in the case of fast interfacial reaction. The crosslinking of the rubber phase induces an important shift of the phase inversion composition to higher rubber content. For blends containing low molecular weight PBT, up to 60 wt% of rubber can be homogeneously dispersed in the PBT matrix at long mixing time. In this case, development of high performance PBT based thermoplastic vulcanisates can be envisioned.

In vivo and in vitro degradation of poly(ether ester) block copolymers based on poly(ethylene glycol) and poly(butylene terephthalate)

Two in vivo degradation studies were performed on segmented poly(ether ester)s based on polyethylene glycol (PEG) and poly(butylene terephthalate) (PBT) (PEOT/PBT). In a first series of experiments, the in vivo degradation of melt-pressed discs of different copolymer compositions were followed up for 24 weeks after subcutaneous implantation in rats. The second series of experiments aimed to simulate long-term in vivo degradation. For this, PEOT/PBT samples were pre-degraded in phosphate buffer saline (PBS) at 100°C and subsequently implanted. In both series, explanted materials were characterized by intrinsic viscosity measurements, mass loss, proton nuclear magnetic resonance spectroscopy ( 1H-NMR) and differential scanning calorimetry (DSC). In both studies the copolymer with the higher PEO content degraded the fastest, although all materials degraded relatively slowly. To determine the nature of the degradation products formed during hydrolysis of the copolymers, 1000 PEOT71PBT29 (a copolymer based on PEG with a molecular weight of 1000 g/mol and 71 wt% of PEO-containing soft segments) was degraded in vitro at 100°C in phosphate buffer saline (PBS) during 14 days. The degradation products present in PBS were analyzed by 1H-NMR and high performance liquid chromatography/mass spectroscopy (HPLC/MS). These degradation products consisted of a fraction with high contents of PEO that was soluble in PBS and a PEOT/PBT fraction that was insoluble at room temperature. From the different in vitro and in vivo degradation experiments performed, it can be concluded that PEOT/PBT degradation is a slow process and generates insoluble polymeric residues with high PBT contents.

Organic short fibre/thermoplastic composites: morphology and thermorheological analysis

A study to evaluate the thermorheological properties of organic in situ composites with short polymer fibres dispersed in a thermoplastic matrix has been carried out. High-density polyethylene/Poly(butylene terephtalate) HDPE/PBT, HDPE/EVA-9/PBT and HDPE/(EVA-9-Bu2SnO)/PBT (in situ compatibilised blends) were melt blended in a twin-screw extruder, drawn at the die exit and cooled. Morphological results revealed that it is possible to generate fibrillar morphologies for high PBT concentration and draw ratios higher than 1. Compatibilisation with in situ generated PBT-g-EVA-9 compatibiliser was achieved. Rheological properties in the melt state and in the solid state were used to analyse the compatibilisation and the reinforcing effect of fibrils. Two phenomenological models, Takayanagi and Halpin-Tsaı̈, were used to describe the variations of E′ and tanδ as a function of temperature.

New Thermoplastic Elastomers by Incorporation of Nonpolar Soft Segments in PBT-Based Copolyesters

The incorporation of hydroxy-functionalized hydrogenated polybutadienes (HO−PEB−OH, KRATON liquid polymer) into PBT-based copolyesters by a conventional two-step melt polycondensation procedure is described. The usually occurring macrophase separation with nonpolar soft segments is avoided by chain extension of HO−PEB−OH with ethylene oxide to yield the corresponding hydroxy-terminated PEO−PEB−PEO triblock copolymers. Several PEO−PEB−PEO triblock copolymers with different PEO block lengths have been synthesized by means of anionic synthesis and incorporated into PBT-based copolyesters with varying PBT content. We show that the chain extension of HO−PEB−OH with ethylene oxide compatibilizes the nonpolar KRATON with the polar reactants 1,4-butanediol and dimethyl terephthalate during melt polycondensation, leading to a complete incorporation of the triblock copolymer into the copolyester. Morphological studies using SFM as well as mechanical testing show that the morphology is strongly influenced by the soft segment leading to dispersed PBT crystallites in a matrix of the soft phase. Thermal characterization of the synthesized copolyesters by DSC exhibits a low glass transition temperature and a high PBT melting point even at high soft segment contents, making these materials suitable for low- and high-temperature range applications.

Effect of PBT melt viscosity on the morphology and mechanical properties of compatibilized and uncompatibilized blends with ABS

The toughness and morphology of poly(butylene terephthalate), PBT, blends with acrylonitrile–butadiene–styrene, ABS, materials are very sensitive to the PBT molecular weight or melt viscosity. High PBT melt viscosity is shown to lead to improved ABS (and styrene–acrylonitrile copolymer, SAN) dispersion which improves the low temperature fracture toughness of PBT/ABS blends. Compatibilization by methyl methacrylate, glycidyl methacrylate, ethyl acrylate terpolymers, or MGE, was shown to further improve ABS and SAN dispersion and reduce the ductile–brittle transition temperature. Addition of the compatibilizer broadens the window of acceptable processing temperatures. The minimum quantity of ABS required to toughen PBT is lower the higher the PBT melt viscosity. The tensile properties of PBT/ABS/MGE blends were shown to be relatively insensitive to PBT melt viscosity or reactive compatibilization.

Crystallization behavior in poly(ether imide)/poly(butylene terephthalate) blends using a spectroscopic method

Crystallization behavior of poly(butylene terephthalate) in poly(ether imide)(PEI)/poly(butylene terephthalate)(PBT) blends was analyzed by FT-IR ATR spectroscopy. The crystalline characteristic IR peaks of PBT were investigated as a function of the annealing time. It was also found that CO stretching peak of PEI/PBT blend shifted to lower wavenumber as the crystallization of PBT in PEI/PBT blends proceeded. The trend of CO peak shift in PEI/PBT blends was in good agreement with the crystallinity change of PBT. Crystallization behavior of PBT in PEI/PBT blend strongly depended on the composition of PEI/PBT blends. In case of high PBT weight fraction (2/8, 4/6 composition), crystallization of PBT occurred without any phase separation. However, PBT crystallization proceeded mainly in the PBT rich-phase after the phase separation at low PBT weight fraction (6/4, 8/2 composition).

Hot drawing of partially miscible blends of polycarbonate and poly(butylene terephthalate)

Samples of PC-PBT blends over the entire composition range were drawn at 1600°C to high extensions, 2.1-5.8, to study the mechanical reinforcement and the molecular structure development upon deformation. Elastic modulus E' increases with extension ratio for all compositions and temperatures. Blends with 25 and 40 wt % of PC show higher E' at low temperature than pure PBT blends do. Crystallinity increases with extension ratio and is relatively smaller with increasing PC content. The influence of the reversible α to β crystal form transformation was also studied. The second moment of the orientation function f for both crystal forms increases to high values > 0.9 at relatively low extensions. f decreases with PC content for α crystals but decreases for β crystals. The α fraction is high fbr PBT and decreases with PC content and extension ratio in the blends. Strain recovery experiments show that the α to β transformation is also elastic in nature at high extension ratios and that the reinforcing effect in high PHT content blends is not due to the α/β ratio.

Hot drawing of partially miscible blends of polycarbonate and poly(butylene terephthalate)

Samples of PC-PBT blends over the entire composition range were drawn at 160°C to high extensions, 2.1–5.8, to study the mechanical reinforcement and the molecular structure development upon deformation. Elastic modulus E' increases with extension ratio for all compositions and temperatures. Blends with 25 and 40 wt% of PC show higher E' at low temperature than pure PBT blends do. Crystallinity increases with extension ratio and is relatively smaller with increasing PC content. The influence of the reversible α to β crystal form transformation was also studied. The second moment of the orientation function f for both crystal forms increases to high values > 0.9 at relatively low extensions. f decreases with PC content for α crystals but decreases for β crystals. The α fraction is high for PBT and decreases with PC content and extension ratio in the blends. Strain recovery experiments show that the α to β transformation is also elastic in nature at high extension ratios and that the reinforcing effect in high PBT content blends is not due to the α/β ratio. © 1996 John Wiley & Sons, Inc.

Compatibilization of PP/PBT and PP/PA6 blends with a new oxazoline-functionalized polypropylene

Aim of this work was to study the effectiveness of a novel oxazoline-functionalized polypropylene as a compatibilizer for PP/PBT and PP/PA6 blends. This polypropylene-based compatibilizer mixes well with the polypropylene and is capable of reacting with the carboxylic and amine end groups of PBT and PA6. Significant improvements in blend toughness were achieved without reduction in strength and stiffness. These effects were related to stabilized morphology of finely dispersed minor phase well attached to the matrix. The enhanced interfacial interactions between the two phases, in particular at high PBT content were evidenced by increased melt viscosity.

Poly(butylene terephthalate)/phenoxy blends: Synergistic behavior in mechanical properties

Abstract The mechanical properties of miscible poly(butylene terephthalate) (PBT)/poly (hydroxy ether of bisphenol A) (phenoxy) blends obtained by melt mixing have been studied by means of the tensile test. The crystallinity of the blends has been studied by means of DSC and density measurements. A synergistic behavior, principally in the break properties, at high PBT contents in the blends is observed. As can be seen from the torque and density data, this synergistic behavior is related with the high level of miscibility which seems to exist at high PBT contents compared with that of the high phenoxy content region.