Crystallization Rate Of PBT Research Articles

Studies on the effects of 4,4′-dihydroxyphenyl on crystallization and melting behavior of poly (butylene terephthalate)

Abstract The blends of poly (butylene terephthalate) (PBT) and 4,4′-dihydroxyphenyl (DHP) were prepared by melt blending, and the effects of DHP on the crystallization and melting behaviors of PBT were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and polarized optical microscopy (POM). The results showed that crystallization temperature and crystallinity of PBT apparently decreased with the addition of DHP. A remarkably decline in crystallization rate of PBT was achieved, and the blends had higher σ e and q values than that of pure PBT as analyzed based on the Avrami equation and Lauritzen-Hoffman equation. The crystal structure of PBT did not change by the addition of DHP, while the spherulite size of PBT decreased.

Effects of Halloysite Nanotube on the Mechanical Properties and Nonisothermal Crystallization Kinetics of Poly(Butylene Terephthalate) (PBT)

In this study, poly(butylene terephthalate) (PBT)/halloysite composites having various amounts of halloysite, as a one-dimensional (1D) nanotubular alumina-silicate filler, were prepared by melt processing in a twin screw extruder. Nonisothermal crystallization behaviors of the samples were studied by DSC and XRD methods. The effect of halloysite amount on the nonisothermal melt crystallization kinetics of the PBT was analyzed with various kinetic models, namely the Ozawa, Avrami modified by Jeziorny, and Liu–Mo. Crystallization activation energies of the samples were determined by the Kissinger model. Viscoelastic properties of the samples were studied by DMA tests. By comparing the effect of halloysite amount on the melt crystallization kinetics of PBT, it was found that halloysite increased the crystallization rate of PBT. Crystallization activation energy values of the PBT and composite samples including 2%, 5%, and 10% of halloysite were found to be −341.8, −353.3, −373.6, and −419.6 kJ/mol, respectively. Based on the DMA tests, it was found that halloysite increased the elastic feature of the sample due to polymer-filler interactions.

Effect of PTW on crystallization kinetics of toughened PBT/PC blends

AbstractPoly(butylenes terephthalate) (PBT)/polycarbonate (PC)/poly(ethylenebutylacrylate- glycidyl methacrylate copolymer) (PTW) blends containing PTW as toughening modifier were obtained by extrusion and injection molding. The effect of PTW on the melt rheology of PBT/PC blend was examined by means of capillary calorimetry. The rheological properties of the blends suggested high reactivity between epoxy groups in PTW and terminal carboxylic acid group and/or hydroxyl group of PBT inhibited transesterification between PBT and PC. The effect of PTW on the crystallization of PBT in the PBT/PC/PTW blends was investigated by crystallization kinetics analysis under isothermal and nonisothermal conditions. Isothermal crystallization experiments were performed at crystallization temperature and analyzed based on the Avrami equation. A decrease of the half time of PBT crystallization t1/2, as well as an increase of the overall crystallization rate of PBT in the PBT/PC/PTW blends have been observed. Nonisothermal crystallization experiments were performed at given cooling rate. The Ozawa analysis is used to describe its nonisothermal crystallization behavior. It is observed that at a given cooling rate, the PTW increases the overall crystallization rate of PBT in the PBT/PC/PTW blends. This is consistent with the result obtained under isothermal crystallization condition.

Kinetics of isothermal and non‐isothermal crystallization of poly(butylene terephthalate)/ liquid crystalline polymer blends

AbstractThe melting behavior and isothermal and non‐isothermal crystallization kinetics of poly(butylene terephthalate) (PBT)/thermotropic liquid crystalline polymer (LCP), Vectra A950 (VA) blends were studied by using differential scanning calorimetry. Isothermal crystallization experiments were performed at crystallization temperatures (Tc), of 190, 195, 200 and 205°C from the melt (300°C) and analyzed based on the Avrami equation. The values of the Avrami exponent indicate that the PBT crystallization process in PBT/VA blends is governed by three‐dimensional morphology growth preceded by heterogeneous nucleation. The overall crystallization rate of PBT in the melt blends is enhanced by the presence of VA. However, the degree of PBT crystallinily remains almost the same. The analysis of the melting behavior of these blends indicates that the stability and the reorganization process of PBT crystals in blends are dependent on the blend compositions and the thermal history. The fold surface interfacial energy of PBT in blends is more modified than in pure PBT. Analysis of the crystallization data shows that crystallization occurs in Regime II across the temperature range 190°C‐205°C. A kinetic treatment based on the combination of Avrami and Ozawa equations, known as Liu's approach, describes the non‐isothermal crystallization. It is observed that at a given cooling rate the VA blending increases the overall crystallization rate of PBT.

Structure formation and miscibility of sheets from PBT and LCP blends

Sheets from blends containing poly(butylene terephthalate) (PBT) and liquid crystalline polymer (LCP) were prepared using a twin-screw extruder. The LCP used is a copolymer composed of 20 mol % ethylene terephalate (PET) and 80 mol % p-hydroxybenzoic acid (PHB). Thermal behavior, viscoelastic properties, and structure of the sheets of various compositions were investigated by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), microwave orientation analysis (MOA), and wide angle x-ray diffraction (WAXD). X-ray diffractograms of extruded sheets from PBT, LCP, and their blends show a high degree of orientation along extrusion direction. The orientation is mainly due to the high crystallization rate of PBT, although crystallization and orientation of PBT in the PBT and LCP blends could also be induced by adding LCP. In the PBT and LCP blends, the thermal properties of the constituents are slightly changed indicating that PBT and LCP are partially miscible. DSC measurements show that as the amount of LCP added to the blend increased, the melting point Tm of PBT in the blends decreased. The single glass transition temperature Tg for the PBT and LCP was observed by DMA. Furthermore, no evidence of transesterification in PBT and LCP blends was observed by WAXD.

The structure and physical properties ofin situ composites based on semiflexible thermotropic liquid crystalline copolyesteramide and poly(butylene terephthalate)

Liquid crystalline polymer–poly(butylene terephthalate) (LCP/PBT) blends were prepared by melt mixing. The LCP employed was a thermotropic copolyesteramide based on 30 mol % of p-amino benzoic acid (ABA) and 70 mol % of poly(ethylene terephthalate) (PET). The thermal, dynamic mechanical and rheological properties, morphology, and crystal structure of LCP/PBT blends were studied. The results showed that the semiflexible ABA30/PET LCP is miscible in the melt state with PBT, and they are partial miscible in the solid state. Differential scanning calorimetric measurements showed that the introduction of the semiflexible LCP into LCP/PBT blends retards the crystallization rate of PBT. However, the LCP dispersed phase acted as the sites for the nucleation of spherulites and enhance the degree of crystallinity of PBT. Hot-stage optical microscopy examination revealed that the LCP microfibers with random orientation are dispersed in the PBT matrix of compression molded LCP/PBT blends. Under the application of a shearing force, the LCP domains in the PBT matrix tended to deform into microfibers, and to orient themselves along the flow direction. The formation of microfibers resulted in an increase of the storage modulus. The torque measurements indicated that the melting viscosity of the LCP/PBT blends is much lower than that of the pure PBT. Finally, the wide-angle X-ray diffraction patterns indicated that PBT shows no structural change with the incorporation of LCP, but the apparent crystal sizes of several diffraction planes change significantly. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 403–414, 2000

Effect of Compatibilizer on the Crystallization Kinetics of Blends of Poly(butylene terephthalate) with a Liquid Crystalline Polyester

The effects of addition of 4,4′-dihydroxy-3,3',5,5′-tetramethyldiphenyl ether (TM-BPL) on the isothermal crystallization kinetics, mechanical properties, and morphologies for the blends of poly(butylene terephthalate) (PBT) with a liquid crystalline copolymer based on p-hydroxybenzoate and ethylene terephthalate, known as Novaccurate E310 (E310), were studied. The flexural strength and modulus of the PBT/E310 blend increased approximately in accordance with the upper-bound composite equation. When TM-BPL (2 phr) was added to the PBT/E310 (80/20) blend as a reactive compatibilizer, the flexural strength and modulus somewhat increased. The crystallization rate of PBT from the melt blend decreased with increasing E310 content and was further depressed by the presence of TM-BPL. The Avrami exponent (n) was evaluated to be approximately 3 in both the binaryl and the ternary blends. The slight improvement in the mechanical properties and the depression of the crystallization of PBT by the addition of TM-BPL are thought to be caused by the chemical reaction of TM-BPL with PBT and/or E310.

Effect of Compatibilizer on the Crystallization Kinetics of Blends of Poly(butylene terephthalate) with a Liquid Crystalline Polyester

The effects of addition of 4,4′-dihydroxy-3,3',5,5′-tetramethyldiphenyl ether (TM-BPL) on the isothermal crystallization kinetics, mechanical properties, and morphologies for the blends of poly(butylene terephthalate) (PBT) with a liquid crystalline copolymer based on p-hydroxybenzoate and ethylene terephthalate, known as Novaccurate E310 (E310), were studied. The flexural strength and modulus of the PBT/E310 blend increased approximately in accordance with the upper-bound composite equation. When TM-BPL (2 phr) was added to the PBT/E310 (80/20) blend as a reactive compatibilizer, the flexural strength and modulus somewhat increased. The crystallization rate of PBT from the melt blend decreased with increasing E310 content and was further depressed by the presence of TM-BPL. The Avrami exponent (n) was evaluated to be approximately 3 in both the binaryl and the ternary blends. The slight improvement in the mechanical properties and the depression of the crystallization of PBT by the addition of TM-BPL are thought to be caused by the chemical reaction of TM-BPL with PBT and/or E310.

Blends of poly(tetramethylene terephthalate) with a liquid‐crystalline polyester, poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate), 2. Crystallization kinetics and melting behaviour

AbstractThe isothermal crystallization kinetics, the morphology and melting behaviour of blends of poly(tetramethylene terephthalate) {poly(butylene terephthalate), (PBT)} with a thermotropic liquid‐crystalline polyester, poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate) (HTH10), were studied in the composition range 0—50 wt.‐% of HTH10 by optical microscopy and differential scanning calorimetry. The spherulite growth rate and the overall crystallization rate of PBT from melt blends are markedly depressed by the presence of the mesomorphic component. Changes of superstructure and of primary nucleation density of PBT spherulites in the blends were observed. The analysis of the melting behaviour of these samples indicates that the stability of PBT crystals and their reorganization processes on heating are dependent on the blend composition. A decrease of the equilibrium melting temperature of PBT is found with increasing the amount of HTH10. According to previously reported investigations on the same system, the results are discussed in respect of the onset of interactions between the two polymers in the liquid state.