PBT Content Research Articles

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.

Evaluation of proton beam therapy pedagogy within the UK's pre-registration radiotherapy and oncology higher education setting

IntroductionProton Beam Therapy (PBT) continues to expand across the United Kingdom (UK). It is estimated that by the end of 2021, there will be seven clinically operational PBT centres across the UK, such prospects raise questions related to training and recruitment of PBT competent workforce. Comprehensive academic education in the field of PBT can be a suitable solution to ensure adequate representation of competent staff for the future. However, at present, little is known in this sphere which warrants the need for exploration of this topic. MethodsAn online questionnaire was distributed among Higher Education Institutes (HEIs) of radiotherapy & oncology pre-registration courses within the UK setting. The study aimed to explore current PBT content that is taught to radiotherapy students. ResultsFive HEIs providing radiotherapy & oncology course providers, participated in the study (5/12). Each institution provided at least one HCPC approved course that led to professional registration as Therapeutic Radiographer (TR). All courses identified in the study included module(s) related to PBT however, the content varied across the spectrum. A deficiency was identified where PBT based education appeared to lack in learner exposure to clinical PBT pedagogy. ConclusionAlthough training resources within the area of PBT practice appear limited, it is apparent that HEIs have endeavoured to evolve their PBT content inclusion; however, there is scope for further enhancements required to meet PBT stakeholder needs appropriately and collaboratively. Implications for practicePost-qualification training that is designed for a select group of professionals may be a rational approach in fulfilling service demand; however, a clear need for stronger collaboration between HEIs is encouraged in order to standardise and unify the knowledge provided for students, nationwide.

Development of in situ nanofibrillar poly (lactic acid)/poly (butylene terephthalate) composites: Non-isothermal crystallization and crystal morphology

Tuned one-step melt spinning of poly (lactic acid) (PLA)/poly (butylene terephthalate) (PBT) blends containing 1–10 wt% of PBT, was carried out successfully to induce in situ nanofibrils of PBT with average diameter of 23–51.4 nm. Scanning electron microscopy (SEM) images showed the morphology of PBT nanofibrils (NFs) in the PLA matrix and it was found that the aspect ratio of PBT NFs was more than 400. The crystal morphology of the PLA melt spun fibers in the presence and absence of PBT NFs was analyzed using polarized optical microscopy. Dramatic changes in the crystal morphology of PLA were observed in the presence of PBT NFs. Scattered spherulites in the PLA fibers changed to very small crystals oriented in the PBT NFs direction in the PLA/PBT fibers. Non-isothermal crystallization studies of PLA in the in situ nanofibrillar composites (NFCs) prepared by compression molding demonstrated a significant improvement of crystallinity (27.5%) as well as crystallization rate. Enhanced crystallization rate provided comparative conditions to study the crystal forms of PLA and their relative populations nucleated during the cold and melt crystallizations. Moreover, the crystallization behavior of PLA/PBT blend with droplet-matrix morphology was compared with that of the NFC sample at the same PBT content to emphasize the tremendous effect of the morphological tailoring of blends.

Synthesis of poly(butylene terephthalate)-block-poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) multiblock terpolymers via a facile PROP method

We present here the application of in situ cascade polycondensation-coupling ring-opening polymerization (PROP) method for the facile synthesis of a series of three-component poly(butylene terephthalate)-block-poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) multiblock terpolymers (PBT-b-PEO-b-PPO-b-PEO-b-PBT)n, using cyclic oligo(butylene terephthalate)s (COBTs) as monomers and dihydroxyl end-functional PEO-b-PPO-b-PEO (EPE) as macroinitiator. The structure details of these copolymers were characterized by 1H-1H gCOSY and 1H-13C gHSQC NMR spectra. With the assignment of multiblock chain ends, block segmental ends and corresponding groups for each segment, the number-average molecular weights for multiblock terpolymers and each block segment were estimated by the quantitative 1H NMR spectra. Polymerization kinetics studies confirm the PROP mechanism. With crystalline PBT and PEO segments, the multiblock terpolymers are double-crystalline polymers, where the melting point and crystallinity of PBT and PEO segments increase with corresponding PBT and PEO content, respectively. The covalent linking of PBT segments with PEO segments leads to the confined crystallization environment for both blocks, where a strong depression on melting point of PEO crystals was observed, which becomes amorphous at an EPE triblock content of 50%. TEM and SAXS results show interesting lamella-like microphase separation morphologies in these multiblock terpolymers.

Studying the formation mechanism ofin situpoly(butylene terephthalate) microfibrils prepared by one‐step direct extrusion via orthogonal experimental design

Polypropylene/poly(butylene terephthalate) (PP/PBT) microfibrillar composites (MFCs) were prepared throughin situone‐step direct extrusion using a triangle‐arrayed triple‐screw extruder (TTSE) at a processing temperature between the melting points of two components. The orthogonal experimental method was designed to assess the effects of the PBT content and processing parameters (temperature, screw speed, and feed rate) on the morphology of PBT fibrils. It can be found that the most important influence factor on the fibril formation is the PBT content, followed by temperature, feed rate, and screw speed. Furthermore, the morphological evolution procedures of the dispersed phase started from spherical pellets to ellipsoids or ribbons, forming short fibrils, and consequently high‐aspect‐ratio fibrils appeared under the alternating shear‐extensional flow field. Moreover, the rheological properties of linear PP incorporating fibrillated PBT were thoroughly investigated. The relaxation time of blends with various fibrous PBT was linearly proportional to the aspect ratio of fibrils. Strain‐hardening in extensional flow was observed for blends with long fibrils, and the strain‐hardening factor grew with the fibrillar aspect ratio, indicating the formation of a physical entanglement network between fibrils and matrix. POLYM. ENG. SCI., 58:1166–1173, 2018. © 2017 Society of Plastics Engineers

PBT-b-PEO-b-PBT triblock copolymers: Synthesis, characterization and double-crystalline properties

We demonstrated here a facile method to synthesize novel double crystalline poly(butylene terephthalate)-block-poly(ethylene oxide)-block-poly(butylene terephthalate) (PBT-b-PEO-b-PBT) triblock copolymers by solution ring-opening polymerization (ROP) of cyclic oligo(butylene terephthalate)s (COBTs) using poly(ethylene glycol) (PEG) as macroinitiator and titanium isopropyloxide as catalyst. The structure of copolymers was well characterized by 1H NMR and GPC. TGA results revealed that the decomposition temperature of PEO in triblock copolymers increased about 30 °C to the same as PBT copolymers, after being end-capped with PBT polymers. These triblock copolymers showed double crystalline properties from PBT and PEO blocks, observed from DSC and WAXD measurements. The melting and crystallization peak temperatures corresponding to PBT blocks increased with PBT content. The crystallization of PBT blocks showed the strong confinement effects on PEO blocks due to covalent linking of PBT blocks with PEO blocks, where the melting and crystallization temperatures and crystallinity corresponding to PEO blocks decreased significantly with increment of PBT content. The confinement effect was also observed by SAXS experiments, where the long distance order between lamella crystals decreases with increasing PBT length. For the triblock copolymer with highest PBT content (PBT54-b-PEO227-b-PBT54), this effect shows a 30 °C depression on PEO crystals' melting temperature and 77% on enthalpy, respectively, compared to corresponding PEO homopolymer. The crystal morphology was observed by POM, and amorphous-like spherulites were observed during PBT crystallization.

Miscibility and properties of poly(l-lactic acid)/poly(butylene terephthalate) blends

Binary blends of poly(l-lactide) (PLLA) and poly(butylene terephthalate) (PBT) containing PLLA as major component were prepared by melt mixing. The two polymers are immiscible, but display compatibility, probably due to the establishment of interactions between the functional groups of the two polyesters upon melt mixing. Electron microscopy analysis revealed that in the blends containing up to 20% of poly(butylene terephthalate), PBT particles are finely dispersed within the PLLA matrix, with a good adhesion between the phases. The PLLA/PBT 60/40 blend presents a co-continuous multi-level morphology, where PLLA domains, containing dispersed PBT units, are embedded in a PBT matrix. The varied morphology affects the mechanical properties of the material, as the 60/40 blend displays a largely enhanced resistance to elongation, compared to the blends with lower PBT content.

Study on the Reaction and Thermo-Physical Properties of PC and PBT Blend

Blends of polycarbonate (PC) and poly(butylene terephthalate) (PBT) were investigated. For 40 wt % PBT, it forms a continuous phase, the glass transition temperature (Tg) shifts to the lower temperature region. This direct comparison of XRD patterns of pure PBT and PBT containing 1.1% TPPi studied the impact of the crystallization of PBT and TPPi. We can see that diffraction peaks of XRD diagram of PBT/TPPi were broadened. When PBT content was added to 1.1% TPPi, the FWHM increases from 3.8 to 4.2 when diffraction angle was in the range of 16.9 degrees to 17.1 degrees. Thus, the addition of TPPi resulted in the small spherulite size of PBT phase, thus elaborating the sample transparency phenomenon.

Influence of the morphology on the fire behavior of a polycarbonate/poly(butylene terephthalate) blend

AbstractPolycarbonate/Poly(butylene terephthalate) (PC/PBT) blends are used in various industrial sectors, particularly in the cable industry. In this work, the fire behavior of PC/PBT blends was studied for the entire range of blend composition to investigate the relation between fire properties and blend morphology. The morphology of the binary blends used presents a phase inversion point for 25–30 wt % PBT. Various tests have been performed to characterize the fire behavior [limiting oxygen index (LOI), epiradiator test, cone calorimeter, and pyrolysis combustion flow calorimeter (PCFC)]. A change in fire behavior has been observed when the PBT content increases from 20 to 30 wt %, corresponding to the phase inversion, from a continuous rich‐PC phase to a continuous rich‐PBT phase. Consequently, it can be suggested that the control of the morphology of binary polymer blends is crucial to improve their fire properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Melting, crystallization behaviors, and nonisothermal crystallization kinetics of PET/PTT/PBT ternary blends

AbstractThe melting, crystallization behaviors, and nonisothermal crystallization kinetics of the ternary blends composed of poly(ethylene terephthalate), poly(trimethylene terephthalate) (PTT) and poly(buthylene terephthalate) (PBT) were studied with differential scanning calorimeter (DSC). PBT content in all ternary blends was settled invariably to be one‐third, which improved the melt‐crystallization temperature of the ternary blends. All of the blend compositions in amorphous state were miscible as evidenced by a single, composition‐dependent glass transition temperature (Tg) observed in DSC curves. DSC melting thermograms of different blends showed different multiple melting and crystallization peaks because of their various polymer contents. During melt‐crystallization process, three components in blends crystallized simultaneously to form mixed crystals or separated crystals depending upon their content ratio. The Avrami equation modified by Jeziorny and the Ozawa theory were employed to describe the nonisothermal crystallization process of two selected ternary blends. The results spoke that the Avrami equation was successful in describing the nonisothermal crystallization process of the ternary blends. The values of the t1/2 and the parameters Zc showed that the crystallization rate of the ternary blends with more poly(ethylene terephthalate) content was faster than that with the lesser one at a given cooling rate. The crystal morphology of the five ternary blends investigated by polarized optical microscopy (POM) showed different size and distortional Maltese crosses or light spots when the PTT or poly(ethylene terephthalate) component varied, suggesting that the more the PTT content, the larger crystallites formed in ternary blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Studies on blends of binary crystalline polymers: Miscibility and crystallization behavior in PBT/PAr(I27-T73)

The miscibility and crystallization behavior of binary crystalline blends of poly(butylene terephthalate) [PBT] and polyarylate based on Bisphenol A and a 27/73 mole ratio of isophthalic and terephthalic acids [PAr(I27-T73)] have been investigated by differential scanning calorimetry (DSC). This blend system exhibits a single composition-dependent glass transition temperature over the entire composition range. The equilibrium melting point depression of PBT was observed, and Flory interaction parameter χ 12 = −0.96 was obtained. These indicate that the blends are thermodynamically miscible in the melt. The crystallization rate of PBT decreased as the amount of PAr(I27-T73) increased, and a contrary trend was found when PAr(I27-T73) crystallized with the increase of the amount of PBT. The addition of high- T g PAr(I27-T73) would suppress the segmental mobility of PBT, while low- T g PBT would have promotional effect on PAr(I27-T73). The crystallization rate and melting point of PBT were significantly influenced when the PAr(I27-T73) crystallites are previously formed. It is because not only does the amorphous phase composition shift to a richer PBT content after the crystallization of PAr(I27-T73), but also the PAr(I27-T73) crystal phase would constrain the crystallization of PBT. Thus, effects of the glass transition temperature, interaction between components, and previously formed crystallites of one component on the crystallization behavior of the other component were discussed and compared with blends of PBT and PAr(I-100) based on Bisphenol A and isophthalic acid.

Crystallization Behavior and Crystal Morphology of PTT/PBT Blends

The crystallization behavior and crystal morphology of the poly(trimethyl terephthalate) (PTT)/poly(butylene terephthalate) (PBT) blends were investigated by means of differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD) and polarized light microscopy (PLM) techniques. It was found that the two components crystallized simultaneously in the crystalline regions. The degree of crystallinity changed with PTT content. Crystalline properties were worse when the ratio of PBT and PTT contents was close to 50:50, but were better when PBT content was greatly different from PTT content.

The effect of the mass ratio of hard and soft segments on some properties of thermoplastic poly(ester‐siloxane)s

AbstractA series of thermoplastic elastomers based on soft polydimethylsiloxane (PDMS) and hard poly(butylene terephthalate) (PBT) segments was synthesized using a two‐step transesterification reaction in the melt. The molar mass of the soft PDMS component was constant (M̄nPDMS = 1056 g mol−1) while the starting reaction mixture compositions were varied to obtained copolymers with a mass ratio of hard to soft segments in the range from 70/30 to 40/60. The structure and composition of the copolymers was verified by 1H NMR spectroscopy. It appeared that there was a pronounced molar mass maximum when the PBT content of the copolymers was approximately 60 mass%, whereas all samples were considerably inhomogeneous with respect to the distribution of the lengths of the hard segments. Differential scanning calorimetry (DSC) thermograms showed that the melting and crystallization temperature increased with increasing PBT content, as did the total degree of crystallinity, which was confirmed by wide‐angle X‐ray scattering (WAXS) analysis. Thermogravimetric analysis (TGA) performed in nitrogen gave subtle differences for samples of different composition, including that of the PBT homopolymer, whereas in oxygen these differences were more pronounced in the way the thermo‐oxidative stability of the obtained copolymers decreased with decreasing PBT content. Finally, it was shown that the hardness depended directly on the PBT content, ie the higher the PBT content, the greater the hardness of the corresponding copolymer. Copyright © 2004 Society of Chemical Industry

Deformation of Polyether-Polyester Thermoelastoplastics: Mechanothermal and Structural Characterisation

The complex investigation of copoly(ether-ester) based on poly(butylene terephthalate) (PBT) and poly(tetramethylene oxide) (PTMO) reveals its microphase separated nanodomain structure. Initial morphology includes the stacks of crystalline blocks of α-PBT embedded in amorphous matrix with the different degree of continuity of the crystalline network. Two types of amorphous regions can be distinguished, the PTMO-rich phase and the other one containing the PTMO and PBT segments. Reduction of PBT content and proper decrease of its fragments length results in dramatic change in crystalline ordering, the crystallites became smaller and distorted, and more and more PBT segments are included in the amorphous phase. The initial reversible stage of deformation is controlled mostly by elastic deformation of amorphous phase, highly constrained by the network of crystallites. The further stretching results in plastic deformation and reorganisation of the crystalline blocks of PBT and a new crystalline morphology arises. Moreover, at large deformations the soft blocks of PTMO can crystallise and form very distorted paracrystalline regions. Finally, at high enough stress (≈25–30 MPa) the transition from α to β crystalline form in PBT crystal lattice occurs due to conformational changes in the tetramethylene segments. After large deformation, both the morphology and the polymer conformations are far from the equilibrium state. Annealing of the stretched samples at high temperature results in partial recovery of material properties, however the morphology is still far from the initial one even after such annealing.

Poly(ethylene oxide)/poly(butylene terephthalate) segmented block copolymers: the effect of copolymer composition on physical properties and degradation behavior

In this study, the influence of copolymer composition on the physical properties and the degradation behavior of thermoplastic elastomers based on poly(ethylene oxide) (PEO) and poly(butylene terephthalate) (PBT) segments is investigated. These materials are intended to be used in medical applications where degradability of the implant is desired. PEOT/PBT copolymers are microphase separated and up to four thermal transitions are measured by differential scanning calorimetry. Phase separation in the system is enhanced by increasing the molecular weight of starting poly(ethylene glycol) (PEG) or by increasing the PBT content. The mechanical properties, swelling characteristics and degradation rates of the copolymers are influenced by the phase separation. By changing the PEOT/PBT composition, tensile strengths vary from 8 to 23 MPa and elongations at break from 500 to 1300%. Water uptake ranges from 4 to 210%. The in vitro degradation of PEOT/PBT copolymers occurs via hydrolysis and oxidation. In both cases, degradation is more rapid for copolymers with high contents of PEO. Deterioration of copolymer films takes place when the films are exposed to light in the absence of antioxidant. In preventing oxidation under daylight conditions, Irganox 1330 turned out to be a more efficient antioxidant for the copolymers than vitamin E.

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.

Synthesis and characterization of poly[(butylene succinate)-co-(butylene terephthalate)]-b-poly(tetramethylene glycol) segmented block copolymer

Polyester-polyether segmented block copolymers of poly[(butylene succinate)-co-poly(butylene terephthalate)] (PBS–PBT) and poly(tetramethylene glycol) (PTMG) (Mn = 2000) with various compositions were synthesized. PBT content in the PBS was adjusted to ca. 5 mol %. Their thermal and mechanical properties were investigated. In the case of copolymer, the melting point of the PBS–PBT control was 107.8°C, and the melting point of the copolymer containing 70 wt % of PTMG was 70.1°C. Crystallinity of soft segment was 5 ∼ 17%, and that of hard segment was 42 ∼ 59%. The breaking stress of the PBS–PTMG control was 47 MPa but it decreased with increasing PTMG content. In the case of copolymer containing 70 wt % of PTMG, breaking stress was 36 MPa. Contrary to the decreasing breaking stress, breaking strain increased from 300% for PBS–PBT control to 900% for a copolymer containing 70 wt % of PTMG. The shape recovery ratios of the copolymer containing 70 wt % PTMG were almost twice of those of copolymers containing 40 wt % PTMG. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2067–2075, 2001

Preparation and characterization of biaxially oriented films from polybutylene terephthalate based thermoplastic elastomer block copolymers

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 β form of crystalline PBT was found only in the stretched PBT films, but not in the TPE films.

Polypropylene-phenol formaldehyde-based compatibilizers. III. Application in PP/PBT and PP/PPE blends

A new class of compatibilizers suitable for blends or alloys of polypropylene (PP) and engineering polymers having aromatic residues or functionality complimentary to hydroxyl were evaluated in blends of isotactic PP and poly(butylene terephthalate) (PBT), and poly(phenylene ether) (PPE) PP-based blends with 10–30 wt % PBT or PPE were studied. From response modeling of the PP/PBT and PP/PPE blends, it was evident that the viscosity ratio among the blend component, compatibilizer content, and PBT or PPE content were important for the final blend properties. Impact strength was observed to be the most sensitive response to blend compatibilization. The PP-g-PF compatibilizer was observed to be more efficient in blends of PBT than of PPE. The main reason for that was the availability of reactive end-groups in the case of PBT, making covalent bonding between the compatibilizer and PBT possible. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 361–370, 2000

A controlled release system for proteins based on poly(ether ester) block-copolymers: polymer network characterization

The properties of a series of multiblock copolymers, based on hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(butylene terephthalate) (PBT) blocks were investigated with respect to their application as a matrix for controlled release of proteins. The degree of swelling, Q, of the copolymers increased with increasing PEG content and with increasing molecular weight of the PEG segment. Within the composition range tested, Q varied from 1.26 for polymers with PEG segments of 600 g/mol and a PBT content of 60 weight.% up to 3.64 for polymers with PEG segments of 4000 g/mol and a PEG/PBT weight ratio of 80:20. Equilibrium stress (compression)–strain measurements were performed in order to estimate mesh sizes. The mesh size of the copolymers ranged from 38 to 93 Å, which was experimentally confirmed by diffusion of vitamin B12 (hydrodynamic diameter dh=16.6 Å), lysozyme (dh=41 Å) and bovine serum albumin (dh=72 Å). The in vitro degradation of PEG/PBT copolymers with a PEG block length of 1000 g/mol and PEG/PBT weight ratios of 70:30, 60:40 and 40:60 was studied. Matrices with increasing PEG contents exhibited a faster weight loss in phosphate-buffered saline (pH 7.4) at 37°C. Over a degradation period of 54 days, Mn decreased by about 35–45%, while the composition of the matrices, determined by NMR, remained almost constant.