Novel poly(butylene terephthalate)/poly(vinyl butyral) blends prepared by in situ polymerization of cyclic poly(butylene terephthalate) oligomers

Blends of in situ polymerized PBT from cyclic oligomers (c-PBT) and PVB were prepared with varying compositions and compared with mechanical blends of conventional PBT and PVB. The materials were characterized by a variety of techniques including DSC, DMTA, DETA, FTIR, NMR and GPC. It was found that the in situ prepared blend of c-PBT/PVB has one glass transition temperature and shows evidence of miscibility. In contrast, the conventional blend of PBT/PVB shows incompatibility after blending. The cause of miscibility in the in situ prepared PBT/PVB blends is thought to be the formation of a graft copolymer. These results show that there are unique possibilities for in situ processing by combining polymerization of cyclic polyester oligomers with blending.     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/poly(ethylene terephthalate)/glass fiber composites

The influences of the glass fiber (GF) content and the cooling rate for nonisothermal crystallization process of poly(butylene terephthalate)/poly(ethylene terephthalate) (PBT/PET) blends were investigated. The nonisothermal crystallization kinetics of samples were detected by differential scanning calorimetry (DSC) at cooling rates of 5°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min, respectively. The Jeziony and Mozhishen methods were used to analyze the DSC data. The crystalline morphology of samples was observed with polarized light microscope. Results showed that the Jeziony and Mozhishen methods were available for the analysis of the nonisothermal crystallization process. The peaks of crystallization temperature (T_p) move to low temperature with the cooling rate increasing, crystallization half‐time (t_1/2) decrease accordingly. The crystallization rate of PBT/PET blends increase with the lower GF contents while it is baffled by higher GF contents. POLYM. COMPOS. 36:510–516, 2015. © 2014 Society of Plastics Engineers     

Crystallization and melting behaviour of poly(butylene terephthalate) in poly(butylene terephthalate)/polyarylate blends

Summary The crystallization and melting behaviour of poly(butylene terephthalate) has been studied in the pure state and in its blends with a polyarylate of bisphenol A and isophthalic/terephthalic acids. Differential scanning calorimetry has been used as experimental technique and the effects of different thermal treatments have been analyzed. Results show the hindrance for the crystallization of poly(butylene terephthalate) imposed by the presence of polyarylate, as well as the existence of multiple melting after isothermal crystallization. Explanations are given for the observed behaviours.     

Commingled poly(butylene terephthalate)/unidirectional glass fiber composites: Influence of the process conditions on the microstructure of poly(butylene terephthalate)

The microstrocture of poly(butylene terephthalate) (PBT) has been investigated at the different stages of the manufacture of a new generation of composite materials, i.e., commingled Twintex® PBT/glass fiber composites. From differential scanning calorimetry and wide angle X‐ray scattering analysis in addition to density measurements and optical microscopy observations, it was concluded that the different stages of the composite manufacture induce some changes in the crystalline forms of PBT. In particular, the drawing of PBT can promote the formation of the β phase. The analysis of the crystallization kinetics points out the nucleation role played by the fibers. It is concluded that the growth of a transcrystalline region in the vicinity of fibers is promoted by the elevated pressure and temperature used in the manufacturing process of the composites.     

Preparation and properties of poly(ethylene terephthalate)/inorganic whiskers composites

To improve the crystallization and mechanical properties of poly(ethylene terephthalate) (PET), in this work, PET/SiO₂‐MgO‐CaO whiskers composites were prepared via in situ polymerization. The morphology, crystallization, and mechanical properties of the prepared composites were investigated. It was found that inorganic whiskers could be easily dispersed in PET matrix, as demonstrated by SEM and PLM. DSC and PLM observation indicated a strong nucleation capability of inorganic whiskers for PET. Mechanical analysis results showed that the glass transition temperature, tensile strength, and modulus of the composites were greatly improved. A possible chemical bonding between PET chains and the surface of whiskers was observed by FTIR, TGA, and sedimentation experiment. It could be the main reason for the good dispersion and improved properties of the prepared composites. This work is important for the application of PET due to the low cost but high reinforcing efficiency of this inorganic whisker. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel fire resistant matrixes for composites from cyclic poly(butylene terephthalate) oligomers

The objective of the work is to exploit the processing advantages of c-PBT oligomers, essentially required in industrial practice to produce new, robust, multifunctional hybrid copolymers of c-PBT oligomers in a single reaction-molding step, which will be suitable for the use in continuous fiber composites with excellent flame retardant properties. In this article a series of copolyesters were synthesized by using in situ polymerization of cyclic poly(butylene terepthalate) oligomers (c-PBT) and hydroxyl terminated bisphenols and hydroxylated siloxanes in the presence of a tin catalyst at a moderate temperature. The in situ copolymerization was conducted with various c-PBT/tetrabromobisphenol A (TBBPA), bisphenol A diglycidyl ether (BPADGE) and Carbinol PDMS feed ratios respectively. The copolyesters were characterized by GPC, NMR, and DSC techniques. Pyrolysis-combustion flow calorimeter (PCFC) and pyrolysis gas chromatography/mass spectrometry (PyGC/MS) studies were performed to characterize the fire retardant properties of the copolymers during combustion. POLYM. ENG. SCI., 47:1536–1543, 2007. © 2007 Society of Plastics Engineers     

Sequence analysis of poly(ethylene terephthalate)/poly(butylene terephthalate) copolymer prepared by ester-interchange reactions

The molecular structure of the copolyester formed through the interchange reaction in poly(ethylene terephthalate)/poly(butylene terephthalate) blends was investigated with ¹³C-NMR spectroscopy. The molar fractions of heterolinkage triads in the copolyesters were lower than the values calculated by Bernoullian statistics; this indicates that the sequence of heterolinkages was far from a random distribution at the initial stage of the interchange reaction. However, the randomness increased and the number-average sequence length decreased with reaction time. The solubility of the blend decreased with increasing sequence length, resulting from the formation of block copolymers with long sequence lengths at the initial stage of the interchange reaction. The solubility of the copolyester formed by a dibutyltin dilaurate (DBTDL)-catalyzed reaction was higher than that of the copolyester formed by a titanium tetrabutoxide-catalyzed reaction; this is related to the fact that alcoholysis prevailed in the DBTDL-catalyzed reaction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 159–168, 2001     

Properties of poly(butylene terephthalate)/functionalized polyolefin blends

The object of this study was to investigate the physical properties and morphology of melt-mixed blends containing poly(butylene terephthalate) (PBT) with several functionalized polyolefins such as ethylene/vinyl acetate copolymer (EVA), EVA-g-maleic anhydride (EVA-g-MAH), EVA-g-ACID, EVA-g-ACID/ACRYLATE, ethylene methacrylate-g-MAH (EMA-g-MAH), ethylene/ethyl acrylate copolymer (EEA) and an ethylene ionomer. Special focus was made on PBT/EVA-g-MAH and PBT/EMA-g-MAH blends compared with PBT/EVA and PBT/EMA blends. Blends were prepared in a counter-rotating twin-screw extruder. Mechanical and thermal properties, glass transition temperature and morphology were examined using a tensile testing machine, differential scanning calorimeter (DSC), dynamic mechanical analysis and Scanning Electron Microscope (SEM). PBT/EVA-g-MAH and PBT/EMA-g-MAH blends exhibited better impact strength than PBT/EVA and PBT/EMA blends because of the larger interfacial adhesion of EVA-g-MAH and EMA-g-MAH with PBT than EVA and EMA.     

Preparation and characterization of poly(butylene terephthalate) nanocomposites with various organoclays

Layered‐silicate‐based polymer–clay nanocomposite materials were prepared depending on the surface modification of montmorillonite (MMT). Nanocomposites consisting of poly(butylene terephthalate) (PBT) as a matrix and dispersed inorganic clay modified with cetyl pyridinium chloride (CPC), benzyl dimethyl N‐hexadecyl ammonium chloride, and hexadecyl trimethyl ammonium bromide by direct melt intercalation were studied. The organoclay loading was varied from 1 to 5 wt %. The organoclays were characterized with X‐ray diffraction (XRD) to compute the crystallographic spacing and with thermogravimetric analysis to study the thermal stability. Detailed investigations of the mechanical and thermal properties as well as a dispersion study by XRD of the PBT/clay nanocomposites were conducted. X‐ray scattering showed that the layers of organoclay were intercalated with intercalating agents. According to the results of a differential scanning calorimetry analysis, clay acted as a nucleating agent, affecting the crystallization. The PBT nanocomposites containing clay treated with CPC showed good mechanical properties because of intercalation into the polymer matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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

Poly(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.     

Formation and morphology development of poly(butylene terephthalate) nanofibers from poly(butylene terephthalate)/cellulose acetate butyrate immiscible blends

Nano‐scale poly(butylene terephthalate) (PBT) fibers were prepared from PBT/cellulose acetate butyrate (CAB) immiscible polymer blends due to in situ microfibrillar formation during a melt extruding process. The morphological development of the dispersed phase was studied with samples collected at different zones in a twin screw extruder. It was found that the holistic developmental trends of PBT dispersed phase were nearly the same. Fibers began to form even under the shear flow of the twin‐screw extruder. The morphology developmental mechanism of the dispersed phase involved the formation of sheets, holes and network structures, then the size reduction and formation of nanofibers. The effect of viscosity ratio, blend ratio, and shear rate on the morphology evolution was also studied by analyzing the shape and size distribution of the samples. The diameter distribution of the nanofibers could be affected by viscosity ratio, blend ratio, and shear rate. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effect of ultrasound on the processability and mechanical properties of poly(butylene terephthalate)/talc composites

Poly(butylene terephthalate) (PBT)/talc composites were prepared through a single‐screw extruder in the absence or presence of ultrasonic irradiation. A special exit die, which could be regarded as a capillary, was attached to the extruder to measure the effect of ultrasound on the melting temperature and pressure. The experimental results show that with the introduction of ultrasound and with its increasing intensity, the processability of the composites was improved. The morphology of the composites was also investigated by scanning electron microscopy. It was shown that ultrasonic oscillations improved the dispersion of talc in PBT and, furthermore, increased the crystallinity of PBT. Therefore, the mechanical properties were promoted through ultrasonic extrusion but decreased once the ultrasonic intensity was higher than 200 (or 150) W. This deterioration of the mechanical properties was induced by the ultrasonic degradation of PBT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/montmorillonite nanocomposites

The melt intercalation method was employed to prepare poly(butylene terephthalate) (PBT)/montmorillonite (MMT) nanocomposites, and the microstructures were characterized with X‐ray diffraction and transmission electron microscopy. Then, the nonisothermal crystallization behavior of the nanocomposites was studied with differential scanning calorimetry (DSC). The DSC results showed that the exothermic peaks for the nanocomposites distinctly shifted to lower temperatures at various cooling rates in comparison with that for pure PBT, and with increasing MMT content, the peak crystallization temperature of the PBT/MMT hybrids declined gradually. The nonisothermal crystallization kinetics were analyzed by the Avrami, Jeziorny, Ozawa, and Mo methods on the basis of the DSC data. The results revealed that very small amounts of clay (1 wt %) could accelerate the crystallization process, whereas higher clay loadings reduced the rate of crystallization. In addition, the activation energy for the transport of the macromolecular segments to the growing surface was determined by the Kissinger method. The results clearly indicated that the hybrids with small amounts of clay presented lower activation energy than PBT, whereas those with higher clay loadings showed higher activation energy. The MMT content and the crystallization conditions as well as the nature of the matrix itself affected the crystallization behavior of the hybrids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3257–3265, 2006     

Reactive compatibilization of poly(butylene terephthalate)/low‐density polyethylene and poly(butylene terephthalate)/ethylene propylene diene rubber blends with a bismaleimide

The reactive compatibilization effect of a small molecule, bismaleimide (BMI), on poly(butylene terephthalate) (PBT)/low‐density polyethylene (LDPE) and PBT/ethylene propylene diene (EPDM) rubber blends were investigated. All the blends were prepared by melt blending in the mixing chamber of a Haake Rheocord. The particle size of dispersed phase was reduced by >ten times by adding 1.2 wt % of BMI as observed with scanning electron microscopy. The torque‐time curve recorded during mixing showed that the addition of BMI leads to a significant increase in the viscosity of PBT, LDPE, EPDM, and the blends. This indicates that a chemical reaction has taken place. It was confirmed that free radicals are involved in the reactions because the addition of a stabilizer to the blends has removed all the compatibilizing effect, and the torque‐time curve does not show any increase in viscosity. A possible mechanism of compatibilization is proposed. The shear forces during melt mixing cause the rupture of chemical bond in the polymers, which form macroradicals of PBT, LDPE, or EPDM. These macroradicals react with BMI to form PBT‐BMI‐LDPE or PBT‐BMI‐EPDM copolymers. These in situ‐formed copolymers act as compatibilizers to give a significant refinement of the blend morphology. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2049–2057, 1999     

Thermal and mechanical properties of poly(butylene terephthalate)/epoxy blends

In this study, melt blends of poly(butylene terephthalate) (PBT) with epoxy resin were characterized by dynamic mechanical analysis, differential scanning calorimetry, tensile testing, Fourier transform infrared spectroscopy, and wide‐angle X‐ray diffraction. The results indicate that the presence of epoxy resin influenced either the mechanical properties of the PBT/epoxy blends or the crystallization of PBT. The epoxy resin was completely miscible with the PBT matrix. This was beneficial to the improvement of the impact performance of the PBT/epoxy blends. The modification of the PBT/epoxy blends were achieved at epoxy resin contents from 1 to 7%. The maximum increase of the notched Izod impact strength (≈ 20%) of the PBT/epoxy blends was obtained at 1 wt % epoxy resin content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Multiblock terephthalate copolymer as impact modifier for poly(propylene)/poly(butylene terephthalate) blends

The melt polycondensation method was investigated for the synthesis of a multiblock copolymer. The copolymer consisted of hard segments of poly(butylene terephthalate) (PBT) and soft segments of dimerised fatty acid. This multiblock copolymer was characterised by ¹H and ¹³C NMR and FTIR spectroscopies and differential scanning calorimetry. The ¹H NMR method was used for estimating quantitatively the amount of the hard/soft segments. The polymer morphology was characterised using light microscopy and transmission electron microscopy. The investigated polymer was used in a small amount as an additive to poly(propylene)/PBT blends in order to evaluate its influence on the morphology and impact properties of these blends.     

Preparation,characterization, and thermal properties of poly (methyl methacrylate)/boron nitride composites by bulk polymerization

Poly (methyl methacrylate)/boron nitride (PMMA/BN) composites were prepared by dispersing BN particles into methyl methacrylate monomer phase by bulk polymerization method. BN particles modified with silane coupling agent, γ‐methacryloxypropyl trimethoxy silane, were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. Effects of modified BN particle content on thermal conductivity were investigated, and the experimental values were compared with those of theoretical and empirical models. With 16 wt% of BN particles, the thermal conductivity of the composite was 0.53 W/(m·K), 1.8 times higher than that of pure PMMA. The microstructures of the PMMA/BN composites were examined by scanning electron microscopy, energy‐dispersive X‐ray analysis, and transmission electron microscopy. Dynamic mechanical analysis and thermogravimetric analysis traces also corroborated the confinement of the polymer in an inorganic layer by exhibiting an increase in glass‐transition temperatures and weight loss temperatures in the thermogram. Mechanical properties and electrical insulation property of the PMMA/BN composites were also determined. These results showed that PMMA/BN composites may offer new technology and business opportunities. POLYM. COMPOS., 36:1675–1684, 2015. © 2014 Society of Plastics Engineers