Cyclic Butylene Terephthalate Oligomers Research Articles

The Preparation of Cyclic Butylene Terephthalate Fibers with Novel Morphology Based on Melt Electrospinning.

Electrospinning of low molecular weight compounds is relatively under-investigated compared to that of polymers. In this paper, cyclic butylene terephthalate oligomers (CBT) were fabricated into a novel fiber structure without any carrier polymer or template via melt electrospinning technique. The electrospun CBT fibers were prepared at 190 °C and characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). SEM images of the CBT fibers showed that they had a mean diameter of 1.8-2.6 μm. In contrast to most electrospun fibers, the CBT electrospun fibers were discontinuous and exhibited a rod-like morphology with an average length of 6.8-7.1 μm. This kind of morphology is rare in products made by electrospinning or electrospraying. In addition, the fiber morphology was not significantly affected by varying the preparation parameters, such as by collection distance or electric voltage value. FTIR and DSC results showed that CBT structure was not changed in the preparation process, but the degree of polymerization of CBT may be changed because of transesterification reaction. Furthermore, the formation mechanism of the discontinuous fibers was also discussed in this work.

Electrically and Thermally Conductive Carbon Fibre Fabric Reinforced Polymer Composites Based on Nanocarbons and an In-situ Polymerizable Cyclic Oligoester

There is growing interest in carbon fibre fabric reinforced polymer (CFRP) composites based on a thermoplastic matrix, which is easy to rapidly produce, repair or recycle. To expand the applications of thermoplastic CFRP composites, we propose a process for fabricating conductive CFRP composites with improved electrical and thermal conductivities using an in-situ polymerizable and thermoplastic cyclic butylene terephthalate oligomer matrix, which can induce good impregnation of carbon fibres and a high dispersion of nanocarbon fillers. Under optimal processing conditions, the surface resistivity below the order of 10+10 Ω/sq, which can enable electrostatic powder painting application for automotive outer panels, can be induced with a low nanofiller content of 1 wt%. Furthermore, CFRP composites containing 20 wt% graphene nanoplatelets (GNPs) were found to exhibit an excellent thermal conductivity of 13.7 W/m·K. Incorporating multi-walled carbon nanotubes into CFRP composites is more advantageous for improving electrical conductivity, whereas incorporating GNPs is more beneficial for enhancing thermal conductivity. It is possible to fabricate the developed thermoplastic CFRP composites within 2 min. The proposed composites have sufficient potential for use in automotive outer panels, engine blocks and other mechanical components that require conductive characteristics.

CYCLIC BUTYLENE TEREPHTHALATE AND PROMISING FIELD OF APPLICATION

Due to its unique characteristics, cyclic butylene terephthalate is used in novel developments of chemical industry. This article represents the review of the latest achievements in the field of processing, structure, properties of cyclic butylene terephthalate, its physical and chemical modifications as well as composites and nanocomposites based on it. In recent years, cyclic butylene terephthalate oligomers have drawn the attention of scientists. The oligomers can be acquired through the chemical reaction of cyclo-depolymerization and used as materials for ring-opening polymerization reactions. This method of polymerization has a variety of advantages compared to a standard method of synthesis polyesters. One of the main advantages of this method includes the capability to make polymerization reactions at standard atmospheric pressure, low required temperature, no side effects and obtaining a completely finished product as an outcome. The unique qualities of cyclic butylene terephthalate make it a promising material to be used as matrix for a variety of nano- and microcomposites and super concentrate. This study analyzes some of the examples of applying CBT as a super concentrate for creating materials like carbon nanotubes, laminated silicates, carbon fibers and glass fibers. In the majority of studies, the addition of nano-sized fillers into CBT leads to amplification of mechanical properties. In the cases of usage as fillers for carbon fibers and glass fibers, the possibility of replacing thermosetting resins with CBT is currently being researched. It could possibly lead to increase in manufacturability of carbon fibers and fiberglass and increase its possible area of application. Cyclic butylene terephthalate can also be used as a viscosity modifier for synthetic rubbers. In this case it can be both plasticizer and enhancing agent.For citation:Chukov N.A., Mikitaev M.A., Ligidov M.Kh., Bashorov M.T., Shogenov V.N., Pakhomov S.I. Cyclic butylene terephthalate and promising field of application. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 4-13.

Organocatalyzed ring‐opening polymerization of cyclic butylene terephthalate oligomers

ABSTRACTIn this study, various organic compounds, with different activation modes, have been tested as catalysts for the ring‐opening polymerization (ROP) of cyclic butylene terephthalate oligomers (CBT) in bulk at 210 °C, using tert‐butylbenzyl alcohol (tBnOH) as initiator. Among them, 1,3,5‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) appeared to be the most efficient, achieving high monomer conversions in short reaction times (within minutes). Analysis by size‐exclusion chromatography (SEC) of the poly(butylene terephthalate) (PBT) synthesized using this catalyst also showed that the polymerization follows the expected theoretical Mn trend for molecular weights up to 50 kg·mol−1. Chain‐end fidelity relatively to the alcohol initiator has been confirmed by MALDI‐TOF mass spectroscopy, which showed that all polymer chains possess the tert‐butylbenzyl moiety as chain‐end. Finally, to demonstrate the potential of this system for the synthesis of PBT‐based block copolymers, a monomethyl ether poly(ethylene glycol) (PEG) of 5000 g·mol−1 has been employed as initiator for the ROP of CBT. A PEO‐b‐PBT block copolymer of 15,000 g·mol−1 could thus been obtained, as confirmed by the shift of the SEC traces towards higher molecular weights and the same diffusion coefficient determined for 1H NMR signals of the PEO block and the PBT block. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1611–1619

Catalytic Ring-Opening (Co)polymerization of Semiaromatic and Aliphatic (Macro)lactones

The ring-opening polymerization (ROP) of cyclic butylene terephthalate oligomers (cBT) using an aluminum salen catalyst was investigated. The kinetic analysis of the ROP of cBT in tetrachloroethane (TCE) revealed a first-order dependence of the rate constant in catalyst as well as monomer concentration. Comparison with the ROP in other solvents showed that TCE significantly retards the reaction by short-term reversible catalyst deactivation and by long-term permanent deactivation. The apparent activation energy for the ROP of cBT and e-caprolactone (CL) were determined independently, and the difference in reactivity was used to investigate the possibility to synthesize blocky copolymers. Sequence distribution analysis of the copolymers obtained over a period of time from a single feed copolymerization revealed that over the full reaction range the degree of randomness was high. A sequential feed approach, in which CL was added after the polymerization of cBT was completed, showed that the propagation reac...

Preparation and Characterization of Multiwalled Carbon Nanotubes-Reinforced pCBT by Ring-Opening Polymerization of Cyclic Butylene Terephthalate

Multiwalled carbon nanotubes (MWCNT)-reinforced polymerized cyclic butylene terephthalate (pCBT) nanocomposites were prepared by in situ ring opening polymerization of cyclic butylene terephthalate oligomers (CBT). The results of differential scanning calorimetry (DSC) indicated that the melting peak located at the low temperature (Tm1) increased and that at higher temperature (Tm2) decreased with the increasing of content of the MWCNT. During the cooling the MWCNT served as nucleation points from where crystallization can start. The more the MWCNT in the system the earlier the crystallization starts. The Morphological investigations performed by scanning electron microscopy (SEM) shown that the MWCNT were embedded in the matrix and held tightly by the matrix. The modulus and strength increased with MWCNT concentration in the nanocomposites, however, the elongation at break, absorbed energy at break and impact strength were decreased with the increasing of MWCNT content.

Significantly enhanced surface electrical conduction of poly(butylene terephthalate) insulators by direct fluorination

Commercialization of cyclic butylene terephthalate oligomers has opened the door to bulky poly(butylene terephthalate) (PBT) matrix composite parts. In view of the potential applications of PBT in high voltage insulation or other sectors, where surface charge can play an unwanted role, PBT sheets were surface fluorinated in a laboratory vessel using a F2/N2 mixture with 12.5% F2 by volume at the different temperatures of 25, 55, and 85 ° C for the same time of 30 min, to enhance surface electrical conduction and to investigate the effect of fluorination temperature. Conductivity measurements reveal that the fluorinated samples have a much higher surface conductivity than the unfluorinated sample, and surface conductivity significantly increases with fluorination temperature. In accordance with the conductivity measurements, surface potential measurements after corona charging show that the fluorinated samples have a lower or much lower initial surface potential or even no surface potential, strongly depending on fluorination temperature and ambient humidity, compared with a high surface potential of the unfluorinated sample. ATR-IR analyses indicate that fluorination led to substantial changes in surface composition and structure, depending on fluorination temperature. SEM cross section and surface images show an increase of the fluorinated layer thickness with fluorination temperature and a modification of the surface morphology. Contact angle measurements of water show that fluorination also led to a significant increase in surface hydrophilicity, especially at higher fluorination temperatures. The intrinsic increase in surface electrical conduction is considered to be a result of competition between surface compositional changes and surface structural changes or the chemical traps and the physical traps.

Synchronous architecture of ring-banded and non-ring-banded morphology within one spherulite based on in situ ring-opening polymerization of cyclic butylene terephthalate oligomers

Ring-banded morphology of pCBT accompanied by the synchronous evolution of non-ring-banded patterns was investigated through the crystallization of pCBT prepared by ROP of CBT.

New Bismaleimide Resin Toughened by In Situ Ring-Opening Polymer of Cyclic Butylene Terephthalate Oligomer with Unique Organotin Initiator

A new organotin initiator with amino-terminated hyperbranched polysiloxane (HSiSn) for the ring-opening polymerization of cyclic butylene terephthalate (CBT) oligomer was synthesized. Compared with a traditional initiator, butyltin chloride dihydroxide (BCD), HSiSn has a moderate initiate speed, lower toxicity, and good reactivity. Poly(butylene terephthalate) (PBT) is the ring-opening polymer of CBT, of which the crystalline and molecular weight are almost independent of the initiator used, but the PBT initiated by HSiSn has better thermal stability than that by BCD. On this basis, a series of new toughened bismaleimide (BD) resins (HSiSn/CBT-BD) were prepared through the in situ formation of PBT during the prepolymerization of BD resin with HSiSn. Compared with BCD/CBT-BD and BD resins, HSiSn/CBT-BD resins with small loadings of CBT (≤5 wt %) have remarkably improved integrated performances, including higher impact strengths, improved flexural, and tensile properties, better dielectric properties, and e...

Styrene-Butadiene Rubber/Graphene Nanocomposites: Effect of Co-Milling with Cyclic Butylene-Terephthalate

Graphene nanoplatelets (GnP) reinforced styrene-butadiene rubber (SBR) nanocomposites were produced by two different methods. For reference purpose carbon black (CB) reinforced formulations served. In the first method the components were mixed on a two roll open mill directly. In the second method, GnP was subjected to milling in an attritor mill together with cyclic butylene-terephthalate oligomer (CBT) powder prior to the mixing on two roll mill. Samples were cured in a hot press. The rubber sheets were characterized by tensile and tear tests, and their fracture surfaces inspected in scanning electron microscopy (SEM). Results showed that GnP outperformed CB with respect to reinforcing effect. Previous co-milling of GnP with CBT caused a slight decrease in mechanical properties. SEM images proved, that the co-milling process did not affect significantly the dispersion of GnP, its particles were shredded into smaller pieces, which caused the slight decrease in the mechanical properties.

Novel Bifunctional Additive for Rubbers: Cyclic Butylene Terephthalate Oligomer

In this paper the effect of a novel bifunctional additive [cyclic butylene terephthalate (CBT)] was investigated on the rheological, curing and mechanical properties of natural rubber (NR), styrene butadiene rubber (SBR), oil extended styrene butadiene rubber (oSBR), acrylonitrile butadiene rubber (NBR) and ethylene propylene diene rubber (EPDM). Results showed, that CBT acted as an effective lubricant, decreasing the viscosity of the raw mixtures significantly. Furthermore CBT recrystallized upon cooling and acted as semi-active filler, slightly increased the mechanical properties of the tested non strain-crystallizable synthetic rubbers. The polarity of the rubber matrix had a strong effect on the adhesion between rubber and CBT, the higher the polarity of the rubber, the better the adhesion between the two phases was.

Carbon nanotube mat reinforced thermoplastic composites with a polymerizable, low-viscosity cyclic butylene terephthalate matrix

A fabrication method was developed to enhance the processability of a thermoplastic composite reinforced with a carbon nanotube (CNT) mat using an in situ polymerizable low-viscosity cyclic butylene terephthalate (CBT) oligomer. We obtained excellent electrical, thermal, and mechanical properties in the in-plane direction of the prepared CNT mat composites. For the CNT mat composites, the highest thermal diffusivity of 1.53×10−5 m2/s was obtained in the in-plane direction due to the continuously and fully connected CNTs within the CNT mat filler and the value was higher than that of alumina. The properties depended on the internal structure of the composites, such as the development of the morphology, waviness, and weight fraction of the CNT mat within the composites. These excellent properties were revealed under optimum processing conditions with combined high compression pressure, short processing time, and quenching to induce an ideal structure in the CNT mat within the composites.

Influence of a cyclic butylene terephthalate oligomer on the processability and thermoelectric properties of polycarbonate/MWCNT nanocomposites

The thermoelectric properties of melt-processed nanocomposites consisting of a polycarbonate (PC) thermoplastic matrix filled with commercially available carboxyl (–COOH) functionalized multi-walled carbon nanotubes (MWCNTs) were evaluated. MWCNTs carrying carboxylic acid moieties (MWCNT-COOH) were used due the p-doping that the carboxyl groups facilitate, via electron withdrawing from the electron-rich π-conjugated system. Preliminary thermogravimetric analysis (TGA) of MWCNT-COOH revealed that the melt-mixing was limited at low temperatures due to thermal decomposition of the MWCNT functional groups. Therefore, PC was mixed with 2.5 wt% MWCNT-COOH (PC/MWCNT-COOH) at 240 °C and 270 °C. In order to reduce the polymer melt viscosity, a cyclic butylene terephthalate (CBT) oligomer was utilized as an additive, improving additionally the electrical conductivity of the nanocomposites. The melt rheological characterization of neat PC and PC/CBT blends demonstrated a significant decrease of the complex viscosity by the addition of CBT (10 wt%). Optical and transmission electron microscopy (OM, TEM) depicted an improved MWCNT dispersion in the PC/CBT polymer blend. The electrical conductivity was remarkably higher for the PC/MWCNT-COOH/CBT composites compared to the PC/MWCNT-COOH ones. Namely, the PC/MWCNT-COOH/CBT processed at 270 °C exhibited the best values with electrical conductivity; σ = 0.05 S/m, Seebeck coefficient; S = 13.55 μV/K, power factor; PF = 7.60 × 10−6μW/m K−2, and thermoelectric figure of merit; ZT = 7.94 × 10−9. The PC/MWCNT-COOH/CBT nanocomposites could be ideal candidates for large-scale thermal energy harvesting, even though the presently obtained ZT values are still too low for commercial applications.

Rheological properties, morphology, mechanical properties, electrical resistivity and EMI SE of cyclic butylene terephthalate/graphite/carbon black composites

According to traits of cyclic butylene terephthalate (CBT) oligomer polymerizing into poly(butylene terephthalate) (PBT), the composites with high electromagnetic interference shielding effectiveness (EMI SE) were obtained based on CBT oligomer, graphite (GR) and carbon black (CB). The effects of GR and CB on rheological properties, morphology, mechanical properties, and electrical resistivity and EMI SE of PBT composites have been investigated using rheological rheometer, scanning electron microscope (SEM), material mechanical testing machine and electromagnetic shielding measuring instrument, respectively. The synergistic action of GR and CB was observed, which made PBT/GR/CB composites exhibit good mechanical properties, low electrical resistivity, and high vicat softening temperature (VST). Also, the incorporation of CB into PBT/GR composites improved largely EMI SE of composites, and the optimal EMI SE was determined to be ~ 60 dB over the frequency range of 30–3,000 MHz.

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/multiwalled carbon nanotubes nanocomposites prepared by in situ polymerization

ABSTRACTPoly(butylene terephthalate)/multiwalled carbon nanotubes (PBT/MWNT) nanocomposites were prepared by in situ ring‐opening polymerization of cyclic butylene terephthalate oligomers (CBT). The nonisothermal crystallization behavior of the neat PBT and the PBT/MWNT nanocomposites was analyzed quantitatively. The results reveal that the combined Avrami/Ozawa equation exhibits great advantages in describing the nonisothermal crystallization of PBT and its nanocomposites. The presence of MWNTs has the nucleation effect promoting crystallization rate for the nanocomposites, and the maximum one is observed in the nanocomposite having 0.75 wt % MWNT content. On the other hand, the addition of MWNTs has the impeding effect reducing the chain mobility and retarding crystallization, which is confirmed by the crystallization activation energies. However, the nucleation effect of MWNTs plays the dominant role in the crystallization of PBT/MWNT nanocomposites, in other words, the incorporation of MWNTs is increasing the crystallization rate of the nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40849.

Design of microwave plasma and enhanced mechanical properties of thermoplastic composites reinforced with microwave plasma-treated carbon fiber fabric

Microwave plasma equipment was designed and manufactured to improve the interfacial bonding and mechanical interlocking between carbon fiber fabric (CFF) and the polymer matrix. Tensile specimens for the composites reinforced with the as-received and microwave plasma-treated CFFs were prepared using high-speed fabrication with a polymerizable and low-viscosity cyclic butylene terephthalate (CBT) oligomer matrix. Compared with the polymerized CBT (pCBT) matrix, the tensile strengths of the as-received and plasma-treated CFF reinforced composites (CFFRCs) were enhanced by approximately 362.5% and 436.3%, respectively. A high carbon fiber content of 70vol.% was achieved without introducing pores and/or defects into the CFFRC due to the low viscosity and high impregnation characteristics of the CBT resin. It was confirmed that the microwave plasma can increase the surface roughness of the tested CFF without varying the chemical composition and defect level of the CFF. In addition, the interfacial bonding and mechanical interlocking between the CFF and polymer matrix were improved.

Improved tensile strength and thermal stability of thermoplastic carbon fiber fabric composites by heat induced crystallization of in situ polymerizable cyclic butylene terephthalate oligomers

Thermoplastic carbon fiber fabric reinforced composites (CFFRCs) were prepared using a novel fast manufacturing process with a low viscosity polymerizable cyclic butylene terephthalate (CBT) resin. Structure and properties of the composites altered by thermal annealing were investigated to develop appropriate post processing of the CFFRCs for fast production and lowering the processing cost. Annealing at 200°C for 120 min resulted in improved mechanical properties and thermal stability of the polymerized CBT (pCBT) based on differential scanning calorimetry, wide‐angle X‐ray diffraction, and thermo gravimetric analysis. The tensile strength of the CFFRC compression molded at 250°C for 2 min was 440 MPa and that of the CFFRC annealed at 200°C for 120 min after compression molding was 500 MPa, which is an improvement of 550 and 625% relative to the pCBT matrix, respectively. In addition, the thermal stability of the CFFRC annealed at 250°C for 120 min improved by 10°C. Therefore, tensile strength and thermal stability of the manufactured CFFRC can be improved by using the appropriate annealing conditions. POLYM. ENG. SCI., 54:2161–2169, 2014. © 2013 Society of Plastics Engineers

Temperature-dependent decyclopolymerization of cyclic oligomers and the implication on destructuring layered nanosheets for nanocomposite reinforcement

Abstract Taking advantages of low viscosity, self-consistent stoichiometry and explosive decyclopolymerization of cyclic butylene terephthalate oligomers (CBTs), the destruction of multi-layered silicate nanosheets of organically modified montmorillonite (OMMT) has been attempted to explore the reinforcing effect on polymer matrix. Because of the molecular weight and the viscosity imparted by cyclic structure, CBTs were successfully embedded into OMMT galleries, as evidenced by XRD presenting a large down-shift of basal plane peak along with decrease of peak intensity. Subsequent decyclopolymerization of CBTs in-between silicate nanosheets of OMMT has been found governed by polymerization temperature; when a poly(CBT) of high molecular weight is obtainable, efficient dissociation of OMMT to silicate nanosheets and their homogeneous dispersion allowing a notable increase of energy absorption for failure are yielded. A dissociation of OMMT mediated by the temperature-dependent decyclopolymerization presents the usability of cyclic oligomers in the formation of thermoplastic polymer-based nanocomposites exhibiting effective reinforcement which can be hardly accomplished through a conventional process.

Influence of textile preforming binder on the thermal and rheological properties of the catalyzed cyclic butylene terephthalate oligomers

The influence of an epoxy resin textile preforming binder on the thermal and rheological properties of the catalyzed Cyclic Butylene Terephthalate (CBT) oligomers was studied for the manufacturing of textile reinforced pCBT composites with bindered textile preforms. Thermal and rheological investigations were conducted with Differential Scanning Calorimetry (DSC) and plate-plate rheometry, respectively. Significant influences on both non-isothermal und isothermal crystallization of in situ polymerized Cyclic Butylene Terephthalate (pCBT) were observed due to the presence of preforming binder. The crystallization temperature and the crystallinity of pCBT polymer during cooling are both found to decrease with increasing filling fraction of preforming binder. The isothermal polymerization and crystallization process was confirmed to be influenced in the aspect of the starting time of crystallization, the crystallization rate and the crystal structures due to the addition of preforming binder. Furthermore, the processing time was found to be prolonged by adding the preforming binder.

The equilibrium melting temperature and isothermal crystallisation kinetics of cyclic poly(butylene terephthalate) and styrene maleimide (c-PBT/SMI) blends

The equilibrium melting point (\( T_{\text{m}}^{0} \)) and isothermal crystallisation kinetics of cyclic poly(butylene terephthalate) (c-PBT) and styrene maleimide (SMI) blends prepared by solid dispersion and in situ polymerisation of cyclic butylene terephthalate oligomers (CBT) within SMI were investigated. This c-PBT/SMI blend is a miscible semicrystalline–amorphous blend system. The \( T_{\text{m}}^{0} \) of c-PBT/SMI blends was determined using the Hoffman and Weeks method, while Avrami crystallisation kinetic model have been applied to study their isothermal crystallisation kinetics. It was found that \( T_{\text{m}}^{0} \) decreased with increasing SMI content in the blend compositions. All the crystallisation exotherms were obtained from differential scanning calorimetry under isothermal experimental conditions. The average value of Avrami exponent, n, is in the range of 2.4–2.8 for the primary crystallisation process for c-PBT and its blends, which suggest that heterogeneous nucleation of spherulites occurred and growth of spherulites was between two-dimensional and three-dimensional.