Poly(Butylene Terephthalate)/Single Wall Carbon Nanotubes Composite Nanofibers by Electrospinning

Poly(buthylene terephthalate)(PBT)/single wall carbon nanotubes (SWCNTs) composite nanofibers were prepared by electrospinning. The effect of carbon nanotubes on the morphology, crystallization, and mechanical properties of the electrospun composite nanofibers were investigated by SEM, DSC, and tensile testing, respectively. SEM observations indicated that the presence of SWCNTs resulted in finer nanofibers for lower loading; however, a broader distribution, especially for the higher diameter ranges was found for nanofibers with higher amounts of carbon nanotubes. SWCNTs accelerated crystallization and acted as a nucleating agent; the degree of crystallinity increased with increasing content of SWCNTs, followed by a moderate decrease at higher content. Specific tensile strength and modulus of the PBT/SWCNTs composite nanofibers mats were higher than that of neat PBT nanofibers mat. However, the elongation at break of composite nanofibers mats was lower than that of the neat PBT nanofibers mat.     

聚对苯二甲酸丁二醇酯/聚(对苯二甲酸丁二醇酯-e-己内酯)二元结晶共混体系的相容性和结晶行为

聚对苯二甲酸丁二醇酯(PBT)/聚(对苯二甲酸丁二醇酯-e-己内酯)(PBT-PCl)是一个新制备的具有分子间排斥相互作用的A/AxB1?x型两元结晶共混体系. 根据两元平均场模型,报道对苯二甲酸丁二醇酯(BT)与"-己内酯(CL)结构单元的相互作用参数为0.305. DSC研究发现,此共混物呈现了与典型的共聚物/均聚物共混物不同的结晶特征. PBT-PCL影响PBT链的活动力和晶片堆积;同时PBT-PCL的结晶受到先期结晶的PBT晶粒的阻滞. 尽管拥有相同的BT单元,共混的两组分在组成变化范围内仍没有形     

Synthesis of Poly(butylene terephthalate)/Attapulgite Nanocomposites by In-Situ Polymerization and Its Crystallization Behavior

Poly(butylene terephthalate) (PBT)/attapulgite (AT) nanocomposites were prepared via in-situ polymerization without pre-modification of AT. By this method, PBT chains were successfully grafted onto the surface of AT, which was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis. Scanning electron microscope examination indicated the uniform dispersion of AT nanoparticles in PBT matrix. The crystallization behavior of PBT/AT nanocomposites was investigated by X-ray diffraction patterns, differential scanning calorimetry, and step-scan differential scanning calorimetry. The non-isothermal crystallization processes were analyzed with the Avrami, Ozawa, and Mo methods. Crystallization activation energies of the samples were also determined by the Kissinger method. The results indicated that AT could act as a heterogeneous nucleating agent in PBT crystallization and lead to an acceleration of crystallization, while AT also acted as a physical hindrance to retard the transport of polymer chains to the growing crystals.     

Fiber Structure,Tensile Behavior and Antibacterial Activity of Polylactide/Poly(butylene terephthalate) Bicomponent Fibers Produced by High-Speed Melt-Spinning

Abstract

Various types of bicomponent fibers composed of polylactide (PLA) and poly(butylene terephthalate) (PBT) with different molecular weights, arranging the polymers separately in the skin or core, were produced by high-speed melt-spinning. The bicomponent spinning, arranging the PLA with high molecular weight (melt flow rate =1.9?g/10?min, L-lactide content = 98.7%) in the skin and the PBT with low molecular weight (IV = 0.835–0.865 dL/g) in the core, resulted in orientation-induced crystallization in the PLA component at the spinning speed of 2?km/min. This crystallization effect was ascribed to a chain-extending treatment applied to the original PLA (MFR = 4.0?g/10?min) to increase its molecular weight. By the treatment the PLA could crystallize when spun even at 1?km/min in its single-component spinning. On the other hand, the bicomponent spinning system interfered with the orientation-induced crystallization of PBT in the core. As a result, the critical spinning speed needed to generate the orientation-induced crystallization in the core PBT was elevated to 4?km/min. The inferior tensile behavior of the bicomponent fibers, as compared to the single-component PLA or PBT fibers, suggested poor compatibility between PLA and PBT. Transesterification reactions rarely occurred at the interface of the two polymers. The bicomponent fibers prepared from high molecular weight PLA and low molecular weight PBT, however, showed sufficient antibacterial activity and physical properties to be suitable for designing medical clothing materials.     

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

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.     

Characterization of Nano-Structured Poly(D,L-lactic acid) Nonwoven Mats Obtained from Different Solutions by Electrospinning

Two different solvent mixtures, chloroform/dimethylformamide (DMF) and chloroform/ acetone, in 60/40 v/v concentrations, were used to electrospin poly(D,L-lactic acid) (PDLLA). The influence of solvent type, solution concentration, and processing conditions on the morphology and properties of the electrospun mats was studied. The nanofibers characterization was done by scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The smallest nanofibers’ diameters from both mixtures were obtained from solutions with 5 wt%/v PDLLA concentration using a 1.0 kV/cm electrical field. In general the nanofibers from the chloroform/DMF mixture had smaller diameters than the nanofibers from the chloroform/acetone mixture. However, the latter ones were porous, while the nanofibers from the chloroform/DMF mixtures were not. All the PDLLA nanofibers, independent of solvent mixture, had a very low amount of crystallinity and were composed of very small and imperfect α and β crystals.     

Wettability Improvement of Poly (Butylene Terephthalate) Nanofibrous Mats Prepared via Electrospinning by Blending With Regenerated Silk Fibroin

Poly (butylene terephthalate) (PBT)/regenerated silk fibroin (RSF) blend electrospun nanofibrous mats were manufactured to combine the excellent mechanical behavior of PBT with the extraordinary hydrophilic property of RSF. A 1:1 mixture of trifluoroacetic acid (TFA) and dichloromethane (DCM) was adopted as the solvents for PBT and RSF with 20% (w/v) PBT and 16 wt% RSF solutions being mixed in various proportions for electrospinning. The morphology, crystallization, Fourier transform infrared (FTIR) spectra, surface roughness, contact angle, and wetting time of the electrospun blended materials were studied. When the weight ratio of RSF was larger than 50%, a water drop on the surface of the electrospun mat was completely permeated within 300 s or less. Besides the chemical influence of the amino and carboxy groups in RSF, the physical characteristics of the RSF in the blend electrospun mats, such as random coil structure, lower crystallinity, rougher surface than PBT, etc., were a partial reason for the improvement of wettability. The blend nanofibrous mats may be especially applicable in biomedical fields.     

Nanofilled Polypropylene/Poly(trimethylene terephthalate) Blends: A Morphological and Mechanical Properties Study

Polypropylene (PP) /poly(trimethylene terephthalate), (PTT), binary blends in the presence of two interfacial modifier as well as two organically modified nanoclay additives were studied in terms of mechanical and morphological characteristics. Scanning electron microscopy confirmed the incompatibility of the system which was solved to some extent through incorporating the nanoclay as well as functional compatibilizers. An evaluation of the specimens via static mechanical tests in tensile mode gave credence to the assumption that the higher the PTT content, the higher the mechanical performance would be. Furthermore, the compatibilizer-containing blends not only exhibited higher toughness, but also possessed enhanced stiffness when a maleated compatibilizer was added. The tensile modulus was promoted further in the presence of clay nanoparticles; however, toughness was somewhat sacrificed. The Barentsen as well as Halpin-Tsai models were found to describe the binary blends modulus. The reinforcing impact of the nanoclay was exploited to a greater degree in the presence of the compatibilizer.     

Isothermal Melt Crystallization Kinetics for Poly(Trimethylene Terephthalate)/Poly(Butylene Terephthalate) Blends

The kinetics of isothermal melt crystallization of poly(trimethylene terephthalate) (PTT)/poly(butylene terephthalate) (PBT) blends were investigated using differential scanning calorimetry (DSC) over the crystallization temperature range of 184–192°C. Analysis of the data was carried out based on the Avrami equation. The values of the exponent found for all samples were between 2.0 and 3.0. The results indicated that the crystallization process tends to be two‐dimensional growth, which was consistent with the result of polarizing light microscopy (PLM). The activation energies were also determined by the Arrhenius equation for isothermal crystallization. The values of ΔE of PTT/PBT blends were greater than those for PTT and PBT. Lastly, using values of transport parameters common to many polymers (U*=6280 J/mol, T _∞=T _g – 30), together with experimentally determined values of T _m ⁰ and T _g, the nucleation parameter, K _g, for PTT, PBT, and PTT/PBT blends was estimated based on the Lauritzen–Hoffman theory.     

High-Pressure Analysis of the Multiple Melting Endotherms of Poly(ethylene succinate) and Poly(butylene succinate)

The origin of the multiple melting peaks in two linear polyesters, poly(ethylene succinate) (PES) and poly(butylene succinate) (PBS), of isothermally crystallized samples was investigated by differential scanning calorimetry (DSC) at atmospheric pressure and high-pressure differential thermal analysis (HP-DTA) at elevated pressures. In PES, the DSC melting curves showed three endothermic peaks at slow heating rates, which decreased to two with increasing heating rates. The HP-DTA curves showed that the area (qualitative) and peak height of the high-temperature peak decreased with increasing pressure and merged with the low-temperature peak at pressures above 450 MPa. This behavior supported the melting, recrystallization, and remelting model for the observed multiple melting endotherms. In PBS, the DSC melting curves were similar to those seen in PES. The HP-DTA curves were also similar to PES up to 400 MPa, but above this pressure the area and the peak height of the high-temperature peak and the temperature difference between the high- and low-temperature peaks remained unchanged. This observation suggested that the two peaks in PBS were due to the melting of two populations of crystals with different lamellar thickness originally present in the sample. The multiple melting behavior in isothermally crystallized PBS is proposed to incorporate both the melting of two populations of crystals and melting, recrystallization, and remelting.     

Toughening of Poly (Butylene Terephthalate) with Epoxy-Filled Poly (Ethylene–Octene) Copolymer

Toughened poly (butylene terephthalate) (PBT) with triglycidyl isocyanurate (TGIC)-filled poly (ethylene–octene) (POE) was prepared by melt reaction extrusion. For retarding the reaction extent between PBT and the epoxy component, the TGIC was first blended with POE to enwrap its reactive epoxy groups. Then, the TGIC-filled POE was used to melt blend with PBT. The Fourier transform infrared (FTIR) spectra showed that no other peaks appeared in the POE/TGIC specimens except for those originally existing in pure POE and TGIC. The rheological results further confirmed that no reaction occurred between the epoxy and the POE matrix. When the POE/TGIC was blended with PBT, a distinct increase of the viscosity suggested that the migration of the TGIC from POE to PBT during the melt processing induced chain extension reactions of PBT. The results obtained from DSC and DMA revealed that the chain extension of PBT induced by the reaction with TGIC restricted the mobility of PBT chains leading to a limitation of the recrystallization-remelting process and an increase of the glass transition temperature of PBT. The mechanical tests showed that the presence of TGIC in the POE phase distinctly improved the toughness of PBT. Compared to the case of a PBT/POE (80/20, wt%/wt%) blend, the elongation at break and impact strength of the system filled with 5 phr TGIC were increased more than three and six times, respectively.     

Preparation,Morphology and Properties of Poly(Trimethylene Terephthalate)/Thermoplastic Polyester Elastomer Blends

Poly(trimethylene terephthalate)(PTT)/thermoplastic polyester elastomer (TPEE) blends were prepared and their miscibility, crystallization and melting behaviors, phase morphology, dynamic mechanical behavior, rheology behavior, spherulites morphology, and mechanical properties were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), parallel-plate rotational rheometry, polarized optical microscopy (POM), wide angle X-ray diffraction (WAXD), universal tensile tester and impact tester, respectively. The results suggested that PTT and TPEE were partially miscible in the amorphous state, the TPEE rich phase was dispersed uniformly in the solid matrix with a size smaller than 2 μm, and the glass transition temperatures of the blends decreased with increasing TPEE content. The TPEE component had a good effect on toughening the PTT without depressing the tensile strength. The blends had improved melt viscosities for processing. When the blends crystallized from the melt state, the onset crystallization temperature decreased, but they had a faster crystallization rate at low temperatures. All the blends’ melts exhibited a predominantly viscous behavior rather than an elastic behavior, but the melt elasticity increased with increasing TPEE content. When the blends crystallized from the melt, the PTT component could form spherulites but their morphology was imperfect with a small size. The blends had larger storage moduli at low temperatures than that of pure PTT.     

Crystallization Behavior of Poly(Trimethylene Terephthalate)/Polycarbonate Blends

The crystallization behavior of poly(trimethylene terephthalate (PTT) in compatibilized and uncompatibilized PTT/polycarbonate (PC) blends are investigated in the research reported in this paper. The differential scanning calorimetry (DSC) results showed that the crystallization behaviors of PTT/PC blends were very sensitive to PC content. The onset (T_ci) and the peak (T_c) crystallization temperatures shifted to lower temperatures whereas the area of the exotherm decreased quickly as the PC content was increased. The Avrami exponent, n, decreased from 4.32 to 3.61 as the PC content was increased from 0 to 20 wt %, and the growth rate constant, Z _c , decreased gradually as well. This suggests that the nucleation mechanism exhibits the tendency of changing gradually from a thermal nucleation to an athermal mode although the growth mechanism still remains three‐dimensional. When epoxy (2.7 phr) was added as a compatibilizer during melt blending, the T_ci and T_c shifted slightly to higher temperature (≤2°C), and the crystallization enthalpy, however, exhibited an increased crystallinity with the exception of the 90/10/2.7 phr PTT/PC/Epoxy. This suggests that the epoxy make a positive contribution to the PTT crystallization. Moreover, the influences of epoxy on the crystallization behaviors of PTT/PC blends are related to the epoxy content. By contrast, the compatibilizer of ethylene‐propylene‐diene copolymer graft glycidyl methacrylate (EPDM‐g‐GMA, ≤6.3 phr) had little effect on the crystallization behavior of PTT/PC blends. For PTT/PC/Epoxy (2.7 phr) blends, the Avrami exponent, n, decreased to near 3, while the growth rate constant, Z _c , increased slightly as PC content was increased from 0 to 20 wt %. It is suggested that epoxy accelerated the process of the nucleation mechanism changing from thermal nucleation to an athermal mode. The EPDM‐g‐GMA had little effect on the nucleation mode and spherical growth mechanism. The PTT spherulite morphologies in PTT/PC blends were very sensitive to blend composition. Completely different morphologies were observed in pure PTT, PTT/PC, PTT/PC/Epoxy, and PTT/PC/EPDM‐g‐GMA blends.     

Discrimination of Poly(butylenes adipate-co-terephthalate) and Poly(ethylene terephthalate) with Fourier Transform Infrared Microscope and Raman Spectroscope

ABSTRACT

The analysis of plastics and fibers is of importance to forensic scientists, especially in the investigation of trace evidence. In this study, we use Fourier transform infrared microscope and confocal Raman spectroscope to investigate two kinds of polymers: poly(butylenes adipate-co-terephthalate) and poly(ethylene terephthalate), which are very similar in structure and cannot be discriminated easily with other instruments. Infrared and Raman spectra were tentatively interpreted. The indicative peaks (937 cm^?1, 1121 cm^?1 in Infrared spectra; 996 cm^?1, 1396 cm^?1 in Raman spectra) to distinguish the two polymers were also summarized. The data in this study can help forensic scientists identify these two polymers accurately and avoid wrong certificate of authenticity. The data also offer the producer and researchers an effective and fast method to characterize and identify the poly(butylenes adipate-co-terephthalate).     

Synergistic Effect of Polycarbonate on Reactive Core-Shell Particles Toughened Poly(Butylene Terephthalate)

Glycidyl methacrylate functionalized methyl methacrylate-butadiene-styrene copolymer (MBS-g-GMA) core-shell particles were prepared via an emulsion polymerization process. MBS-g-GMA was used to toughen poly(butylene terephthalate) (PBT) and the synergistic toughening effect of polycarbonate (PC) on PBT/MBS-g-GMA blends were investigated. Notched impact tests showed the percolation threshold became lower with the increase of PC content. Transmission electron microscopy displayed a very good dispersion of MBS-g-GMA particles in the PBT matrix with the different PC contents. The synergistic toughening effect was due to the encapsulation structure of PC which could facilitate the whole PBT matrix to yield. The more perfect the encapsulation structure formed, the more obvious the synergistic toughening the PC achieved. Sufficient strength of the phase interface was important to ensure the stress transfer effectively and facilitate the whole PBT matrix to yield. The interface strength between PC and MBS-g-GMA could be ensured by the good miscibility between Poly(methyl methacrylate) (PMMA) (grafted onto the polybutadiene-based rubber core) and PC. For the PBT/PC, the transesterification between PBT and PC improved the interface strength of the PBT and PC phases, as demonstrated by Fourier transform infrared spectroscopy (FTIR) scans. Scanning electron microscopy results showed shear yielding of the matrix and cavitation of the rubber particles were the major toughening mechanisms.     

Effect of Surfactant Concentration on Thermal and Mechanical Properties of Poly(Butylene Succinate)/Organoclay Composites

Composite materials consisting of poly(butylene succinate) (PBS) and montmorillonite (MMT), modified to various extents using trihexyltetradecylphosphonium chloride (THTDP) cations, were prepared using a simple melt intercalation technique. The surfactant contents were varied, i.e. 0.4, 0.6, 0.8, 1.0, and 1.2 times the cation exchange capacity (CEC) of the MMT. The intercalation of the surfactant molecules into MMT layers, confirmed by the increase in interlayer spacing and significant changes in the morphology of the modified MMT, facilitated the dispersion of the clay in the PBS matrix. The properties of the PBS-based composites were changed with increasing surfactant content. The melting and crystallization temperatures increased and the degree of crystallinity (χ_c) decreased. The storage modulus was significantly enhanced below the glass transition temperature (Tg), and Tg shifted to a higher temperature, with a maximum at a surfactant loading of 0.6 CEC. The mechanical properties, including tensile strength, flexural strength, flexural modulus and impact strength, increased and then decreased with surfactant loading, with the maximum observed also at a surfactant loading of 0.6 CEC. In conclusion, an ideal balance between thermal and mechanical properties can be obtained at a surfactant quantity equivalent to 0.6 times the clay CEC. Moreover, all the composites exhibited obvious improvement in thermal and mechanical properties as compared to those of neat PBS.     

Preparation and Characterization of Composites Based on Poly (Butylene Succinate) and Poly (Lactic Acid) Grafted Tetracalcium Phosphate

Tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O) was functionalized by poly (l-lactic acid) (PLLA) in order to improve the dispersion of TTCP particles in poly (butylene succinate) (PBS) matrices, and then a series of the PLLA grafted TTCP/PBS (g-TTCP/PBS) composites were prepared via melt processing. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (DTG/TGA) and melt rheological analysis were used to investigate the structure and properties of the g-TTCP/PBS composites. The results revealed that l-lactide could be grafted onto the surface of TTCP, and the g-TTCP/PBS composites showed the best mechanical properties when the content of g-TTCP was 10 wt%. The crystallization temperature of g-TTCP/PBS composites tended to increase with the increase of g-TTCP contents. The functionalized particles played an important role in augmenting the thermal degradation rate and the complex viscosity of the composites due to their unique structure and the reasonable interfacial interaction between the particles and PBS matrix.     

The Effect of Poly(Ethylene Succinate) on Mechanical Properties of PLLA/PES Blend Prepared by Melt-Blending

Fully biodegradable poly(L-lactide) and poly(ethylene succinate) (PLLA/PES) blends were prepared via melt-blending using PLLA and PES as reactants in a stainless steel chamber. The prepared PLLA/PES blend, as well as neat PLLA and PES, was characterized by Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD) to confirm the structure and the crystallization of PLLA in the blend. The mechanical properties of PLLA/PES blends were determined by bending and tensile tests and the effects of PES content on the mechanical properties of PLLA/PES blends were investigated. It was found that blending some amount of PES could significantly improve the elongation at break while still keeping considerably high strength and modulus. With increasing PES content, both strength and modulus gradually decreased; however the elongation at break significantly increased. SEM was used to examine the morphology of fracture surfaces of PLLA/PES blends.     

Electrospinning of Poly(Hydroxybutyrate-co-hydroxyvalerate) Fibrous Scaffolds for Tissue Engineering Applications: Effects of Electrospinning Parameters and Solution Properties

Electrospinning, a technology capable of fabricating ultrafine fibers (microfibers and nanofibers), has been investigated by various research groups for the production of fibrous biopolymer membranes for potential medical applications. In this study, poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), a natural, biocompatible, and biodegradable polymer, was successfully electrospun to form nonwoven fibrous mats. The effects of different electrospinning parameters (solution feeding rate, applied voltage, working distance and needle size) and polymer solution properties (concentration, viscosity and conductivity) on fiber diameter and morphology were systematically studied and causes for these effects are discussed. The formation of beaded fibers was investigated and the mechanism presented. It was shown that by varying electrospinning parameters within the processing window that was determined in this study, the diameter of electrospun PHBV fibers could be adjusted from a few hundred nanometers to a few microns, which are in the desirable range for constructing “biomimicking” fibrous scaffolds for tissue engineering applications.