Structural and mechanical studies of a blend of poly(butylene terephthalate) and poly(ether ester) based on poly(butylene terephthalate) and poly(ethylene glycol) (original) (raw)
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PET/PBT blends with and without a transesterification catalyst was studied by time-resolved small-angle X-ray scattering (SAXS), differential scanning calorimety (DSC) and wide-angle X-ray scattering in order to investigate the effects of the catalyst and blending on the morphological parameters of the PBT and PET. For the neat polymers, it was found that the catalyst worked as a nucleant agent, increasing the crystallization rate. For the PET/PBT blends, WAXS analysis showed that PET and PBT crystallize separated, since all the peaks of both polymers appear in the WAXS difractogram of the blend. SAXS results showed that both amorphous and crystalline lamellas of blend are larger than that found in the neat polymers, suggesting a miscibility between the amorphous phases and the occurrence of transesterification reactions during the blend mixture, probably forming a amorphous copolymer. This speculation is coherent with the result of dynamic mechanical thermal analysis (DMTA), which shows the presence of only one glass transition in the blend, located between the glass transitions of the neat polymers.
Materials Research, 2013
Poly(butylene terephthalate) (PBT)/ acrylonitrile-butadiene-styrene (ABS) terpolymer blends were prepared in a twin screw extruder and the use of methyl methacrylate-glycidyl methacrylate-ethyl acrylate (MGE) terpolymer as compatibilization additive was evaluated. The effect of different screw profiles and mixing conditions were evaluated on the crystallization of the blends. Differential scanning calorimetry (DSC) was used to evaluate melting and crystallization behaviors of the PBT/ABS blends. The binary PBT/ABS blend has shown a double melting peak when cooled at lower cooling rates, mainly due to its melt-recrystallization during the heating up step. ABS has not affected the melting characteristics of neat PBT. The presence of MGE, as a reactive compatibilizer, in the PBT/ABS blends has reduced its heat of fusion and has partially inhibited its melt-recrystallization under heating. As result, it has prevented the occurrence of double melting peak. The epoxy functional groups of the MGE may react in situ to the carbonyls and hydroxyls end groups of the PBT molecules, thereby hindering the mobility of PBT molecules during the crystallization process due to its grafting to the compatibilizer molecules. The melt mixed blends prepared at lower feeding rate have shown a higher degree of crystallinity for the PBT/ABS blend, probably due to degradation of PBT caused by longer residence time in the extruder. The highest shear stress imposed to the blends at higher screw speed increased the degree of crystallinity of PBT, also due to its degradation.
Polymer Journal, 2007
Annealing or heat scan-induced lamellar thickening and factors influencing crystal unit cells in polymorphic poly(hexamethylene terephthalate) (PHT) were probed using polarized-light optical microscopy (POM), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), synchrotron small-angle X-ray scattering (SAXS). The DSC and WAXD results show that post-scanning or annealing (up to 140 C) on 110 C-crystallized PHT neither transform crystal cell types nor does thin lamella into thick lamella. Rapid lamellar thickening in PHT could take place during DSC scanning, which was proven by comparing SAXS data. T max (final temperature of heating); within a range of 180 up to 220 C) does not influence the polymorphism or multiple melting peaks in PHT. All evidence suggests that kinetic factors are less influential on the polymorphism in PHT. Further, polymorphic poly(hexamethylene terephthalate) (PHT) was blended with monomorphic poly(pentamethylene terephthalate) (PPT) to form a crystalline/ crystalline blend system. The semicrystalline PPT and PHT are miscible in the melt state or quenched amorphous phase. The miscibility, via weak intermolecular interactions, in the amorphous phase of the PHT/PPT blends exerts almost no influence on the crystalline domains, where PPT does not interfere with the formation of or crystal forms in PHT, and vise versa, PHT does not interfere with the sole-crystal form in PPT.
Orientation and mechanical properties of PBT and its blends with a liquid-crystalline copolyester
Journal of Polymer Science Part B: Polymer Physics, 1992
Blends of poly (butylene terephthalate) (PBT) and a liquid-crystalline copolyester (60 mol % poly(p-hydroxy benzoic acid)/40 mol % polyethylene terephthalate) (LCP) were prepared in the melt state. The investigation of mechanical properties indicated that, for the processing conditions used, neither the addition of up to 30 wt % LCP to PBT nor the cooling history affected significantly the tensile modulus E. For oriented specimens, a marked improvement of E was obtained for all the blends, and increased with the LCP content. This improvement was more marked for slowly cooled samples. X-ray diffraction was used to quantify the orientation of the crystalline PBT and liquid-crystalline LCP phases. It was shown that neither the thermal history nor the presence of up to 30 wt % LCP affected the orientation behavior of the PBT crystalline phase. For the LCP phase, measurements were not possible for concentrations lower than 10 wt %, and were more difficult and less precise than for PBT. Nevertheless, it was possible to show that a better orientation was obtained for the slowly cooled samples and for higher concentrations of LCP in the blends. This correlated with the enhancement of mechanical properties observed for the oriented samples. Keywords: poly (butylene terephthalate) and blends, orientation and mechanical properties of blends of PBT and liquid crystalline copolyester, orientation and mechanical properties of liquid crystalline polymers, properties of blends of conventional polymers with
Phase morphology development during processing of compatibilized and uncompatibilized PBT/ABS blends
Journal of Applied Polymer Science, 2007
The development of the multiphase morphology of uncompatibilized blends of poly(butylene terephthalate) (PBT) and acrylonitrile-butadiene-styrene terpolymer (ABS) and PBT/ABS blends compatibilized with methyl-methacrylate glycidyl-methacrylate (MMA-GMA) reactive copolymers during compounding in a twin-screw extruder and subsequent injection molding was investigated. Uncompatibilized PBT/ABS 60/40 (wt %) and compatibilized PBT/ABS/MMA-GMA with 2 and 5 wt % of MMA-GMA showed refined cocontinuous morphologies at the front end of the extruder, which coarsened towards the extruder outlet. Coarsening in uncompatibilized PBT/ ABS blends is much more pronounced than in the compatibilized PBT/ABS/MMA-GMA equivalents and decreases with increasing amounts of the MMA-GMA. For both systems, significant refinement on the phase morphology was found to occur after the blends pass through the extruder die. This phenomenon was correlated to the capacity of the die in promoting particles break-up due to the extra elongational stresses developed at the matrix entrance. Injection molding induces coarsening of the ABS domains in the case of uncompatibilized PBT/ABS blends, while the reactive blend kept its refined phase morphology. Therefore, the compatibilization process of PBT/ABS/ MMA-GMA blends take place progressively leading to a further refinement of the phase morphology in the latter steps, owing to the slow reaction rate relative to epoxide functions and the carboxyl/hydroxyl groups.
Morphology and thermal and mechanical properties of PBT/HIPS and PBT/HIPS-g-GMA blends
Journal of Applied Polymer Science, 2002
The modification of high-impact polystyrene (HIPS) was accomplished by melt-grafting glycidyl methacrylate (GMA) on its molecular chains. Fourier transform infrared spectroscopy and electron spectroscopy for chemical analysis were used to characterize the formation of HIPS-g-GMA copolymers. The content of GMA in HIPSg-GMA copolymer was determined by using the titration method. The effect of the concentrations of GMA and dicumyl peroxide on the degree of grafting was studied. A total of 1.9% of GMA can be grafted on HIPS. HIPS-g-GMA was used to prepare binary blends with poly(buthylene terephthalate) (PBT), and the evidence of reactions between the grafting copolymer and PBT in the blends was confirmed by scanning electron microscopy (SEM), dynamic mechanical analysis, and its mechanical properties. The SEM result showed that the domain size in PBT/HIPS-g-GMA blends was reduced significantly compared with that in PBT/HIPS blends; moreover, the improved strength was measured in PBT/HIPS-g-GMA blends and results from good interfacial adhesion. The reaction between ester groups of PBT and epoxy groups of HIPS-g-GMA can depress crystallinity and the crystal perfection of PBT.