Effect of blending sequence on the microstructure and properties of PBT/EVA‐g‐MAH/organoclay ternary nanocomposites

Ternary nanocomposites based on poly(butylene terephthalate) (PBT), maleic anhydride grafted poly(ethylene‐co‐vinyl acetate) (EVA‐g‐MAH), and organically modified montmorllonite (organoclays) were prepared through four different blending sequences in a Haake rheocord mixer: (1) To blend PBT, EVA‐g‐MAH and organoclays in one step; (2) First to prepare EVA‐g‐MAH/organoclay nanocomposite, then mix it with PBT to get the final nanocomposite; (3) To mix PBT with organoclays first, then the PBT/organoclay nanocomposite with EVA‐g‐MAH. (4) To mix organoclays with the PBT/EVA‐g‐MAH blend. The microstructure of the PBT/EVA‐g‐MAH/organoclay ternary hybrids was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the blending sequence significantly influences the microstructure of PBT/EVA‐g‐MAH/organoclay ternary hybrids and the dispersion behavior of the organoclays in the polymer matrix. Tensile and impact properties of the hybrids were also studied. The results showed that the mixing sequence (2) gives the best tensile and impact strength due to its fine “sea‐island” morphology of PBT/EVA‐g‐MAH blend and good dispersion of the organoclays in the continuous PBT matrix.     

Effect of clay on immiscible morphology of poly(butylene terephthalate)/polyethylene blend nanocomposites

Polymer blend nanocomposites containing poly(butylene terephthalate) (PBT), polyethylene (PE), and organoclay were prepared by direct melt compounding. Their immiscible morphologies weree investigated using electronmicroscopy, X‐ray diffraction, and parallel plate rheometry. The PE domain sizes were reduced when the polar PBT phase was continuous (PBT/PE = 60/40) because the clay tactoids effectively prevented the coalescence of the dispersed PE domains. However, when the PBT component presented domains dispersed in the rich PE matrix (PBT/PE = 40/60), the addition of clay (>2 wt %) changed the phase morphology into a novel cocontinuous one, which was further confirmed by rheological measurements. The existence of clay tactoids led to a sharp enhancement in the viscosity of the PBT phase, changing the viscosity ratio between the PBT and PE phases remarkably, which may have promoted the phase inversion. As a result, clay had significant effects on the morphology of the polymer blend. © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 3628–3633, 2006     

Poly(butylene terephthalate)/organoclay nanocomposites prepared by in situ interlayer polymerization and its fiber (II)

Intercalated nanocomposites with poly(butylene terephthalate) (PBT) incorporated between the montmorillonite layers were synthesized from dimethyl terephthalate and 1,4-butane diol by using an in situ interlayer polymerization. The PBT nanocomposites were melt-spun at different organoclay contents to produce monofilaments. The samples were characterized by using wide angle X-ray diffraction, electron microscopy, thermal analysis, and tensile testing. The extent of the clay layer in the PBT was confirmed by using X-ray diffraction and electron microscopy, and the clay layer was found to be highly dispersed on a nanometer scale. The addition of only a small amount of organoclay was enough to improve the thermo-mechanical properties of the PBT hybrid fibers. The hybrids were extruded with various draw ratios (DRs) to examine the tensile mechanical property of the fibers. At DR=1, the ultimate tensile strength of the hybrid fibers increased with the addition of clay up to a critical content and then decreased. However, the initial modulus monotonically increased with increasing amount of organoclay in the PBT matrix. When the DR was increased from 1 to 6, for example, the strength and the initial modulus values of the hybrids containing 3 wt% organoclay decreased linearly.     

Synthesis of Poly(butylene terephthalate) Nanocomposite by <Emphasis Type="Italic">In-situ</Emphasis> Interlayer Polymerization and Characterization of Its Fiber (I)

Summary The nanocomposites with poly(butylene terephthalate)(PBT) incorporated between the montmorillonite (MMT) layers were synthesized from dimethyl terephthalate (DMT) and butane diol (BD) by using an in-situ interlayer polymerization approach. The PBT nanocomposites were melt spun at different organoclay contents to produce monofilaments. The existence of clay layers in the PBT was confirmed by using X-ray diffraction and transmission electron microscopy, and those layers were found to be disperse on a nanometer scale. The thermal properties of the layered structures of the hybrids were found to be more stable than those of pure PBT. These improved thermal properties of the nanocomposites might arise from an extensive and strongly bonded interface between the organic and the inorganic components. Moreover, the addition of only a small amount of organoclay was enough to improve the mechanical properties of the PBT hybrid fibers.     

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     

Poly(butylene terephthalate)–clay nanocomposites prepared by melt intercalation: morphology and thermomechanical properties

Nanocomposites based on poly(butylene terephthalate) (PBT) and an organoclay (Cloisite 30B) were prepared by melt blending using a twin‐screw extruder. Two kinds of PBTs, ie PBT‐A and PBT‐B, with different inherent viscosities (η_inh), were used for this study (η_inh of PBT‐A and PBT‐B were 0.74 and 1.48, respectively). Dispersion of the clay layers in the PBT nanocomposites was characterized by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile and dynamic mechanical properties and non‐isothermal crystallization temperatures of the nanocomposites were also examined. Nanocomposites based on the higher‐viscosity PBT (PBT‐B) showed a higher degree of exfoliation of the clay and a higher reinforcing effect when compared to the composites based on the lower‐viscosity PBT (PBT‐A). The clay nanolayers dispersed in PBT matrices lead to increases in the non‐isothermal crystallization temperatures of the PBTs, with such increases being more significant for the PBT‐B nanocomposites than for the PBT‐A nanoocomposites. Copyright © 2004 Society of Chemical Industry     

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     

Particulate reinforced PC/PBT composites. II. Effect of nano‐clay particles on dimensional stability and structure–property relationships

The effect of organoclay loading and surface treatment on the dimensional stability, structure–property relationships, and rheological behavior of nanocomposites consisting of polycarbonate (PC), poly[butylene terephyhalate] (PBT), and nano‐clay was investigated at various clay loadings and with various surface modifiers for the nano‐clay particles. It was found that by using an organoclay formed with a polar amine compound that contained two hydroxyl end groups as opposed to nano‐talc, the flexural strength and tensile toughness of the nanocomposites increased by 12 and 27%, respectively, at a particle loading of 1 wt%, while maintaining the flexural modulus of the nanofilled PC/PBT blends. The flexural and tensile modulus of the nanocomposites increased with an increase in particle loading even though the viscosity was reduced due to a loss of molecular weight of the PC/PBT and/or an increase in the compability of the interface between the PC and PBT phase, which varied with organoclay structure. Possible loss of the molecular weight of the PC/PBT matrix was supported by a significant reduction in the storage modulus and complex viscosity at high frequencies of the composites generated with nano‐clay relative to that of the unfilled matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.     

Comparison of Thermomechanical Properties and Morphologies of Polyester Nanocomposite Fibers: PBT,PET, and PTT

Nanocomposites of three different polyesters with dodecyltriphenyl-phosphonium-montmorillonite (C₁₂PPh-MMT) organoclay are compared with respect to their thermal properties, mechanical properties, and morphologies. Poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and poly(trimethylene terephthalate) (PTT) were used as matrix polymers in the fabrication of polyester nanocomposite fibers. The variations in their properties with respect to both the organoclay content in the polymer matrix and the draw ratio (DR) are discussed. Transmission electron microscopy (TEM) micrographs show that some of the clay layers are dispersed homogeneously within the polymer matrix on the nanoscale, although some clay particles are agglomerated. The results additionally show that the addition of only a small amount of organoclay is enough to improve the thermal stabilities and mechanical properties of the polyester nanocomposite fibers.     

Synthesis and properties of poly(butylene terephthalate)/multiwalled carbon nanotube nanocomposites prepared by in situ polymerization and in situ compatibilization

A novel cyclic initiator was synthesized from dibutyl tin(IV) oxide and hydroxyl‐functionalized multiwalled carbon nanotubes (MWNTs) and was used to initiate the ring‐opening polymerization of cyclic butylene terephthalate oligomers to prepare poly(butylene terephthalate) (PBT)/MWNT nanocomposites. The results of Fourier transform infrared and NMR spectroscopy confirmed that a graft structure of PBT on the MWNTs was formed during the in situ polymerization; this structure acted as an in situ compatibilizer in the nanocomposites. The PBT covalently attached to the MWNT surface enhanced the interface adhesion between the MWNTs and PBT matrix and, thus, improved the compatibility. The morphologies of the nanocomposites were observed by field emission scanning electron microscopy and transmission electron microscopy, which showed that the nanotubes were homogeneously dispersed in the PBT matrix when the MWNT content was lower than 0.75 wt %. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermal properties of the nanocomposites. The results indicate that the MWNTs acted as nucleation sites in the matrix, and the efficiency of nucleation was closely related to the dispersion of the MWNTs in the matrix. Additionally, the thermal stability of PBT was improved by the addition of the MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The role of nanoclay partitioning and fibril formation on dyeability of blend nanocomposite fibres

The aim of the present work was to study the effect of microstructure and microfibril formation on dyeability of polypropylene/poly(butylene terephthalate)/organoclay blend nanocomposite fibres. The blend nanocomposite samples with the same blend ratio but varying in organoclay content were prepared via melt compounding by using a co‐rotating twin screw extruder. The microfibrillar morphology and nanoclay partitioning were studied using scanning electron microscopy and transmission electron microscopy together with rheological results. The presence of nanoclay in the form of tactoids in the polypropylene matrix accelerated the dye sorption but much greater ultimate dye uptake could be achieved for the sample in which the major part of the platelets were preferentially located inside the poly(butylene terephthalate) fibrils. Although increasing the organoclay concentration increased the ultimate dye uptake, it limited the fibril formation at higher organoclay concentration. The utilisation of a compatibiliser was found to have an enhancing effect on ultimate dye uptake. This could be explained in terms of the interfacial role of the compatibiliser in improving microfibril formation as well as partitioning a fraction of nanoclay platelets inside the polypropylene matrix.     

Enhanced dyeability of poly(ethylene terephthalate)/organoclay nanocomposite filaments

This study deals with the generation of poly(ethylene terephthalate)/organoclay nanocomposite filaments by the melt‐spinning method and with the investigation of their morphological and dyeing properties. Different montmorillonite types of clay (Resadiye and Rockwood) were modified using different intercalating agents, and poly(ethylene terephthalate) nanocomposite filaments containing 0.5 and 1 wt% organoclays were prepared. Afterwards, the filaments were dyed with two disperse dyes (Setapers Red P2G and Setapers Blue TFBL‐NEW) at different temperatures (100, 110, and 120 °C) in the absence/presence of a carrier. Organoclays and poly(ethylene terephthalate)/organoclay nanocomposites showed an increased d‐spacing between clay layers. Irrespective of clay and surfactant type, poly(ethylene terephthalate)/organoclay nanocomposite filaments dyed at 120 °C in the presence of only a very small amount of carrier showed appreciable dyeability in comparison with neat poly(ethylene terephthalate). The dyeability of the organoclay‐containing poly(ethylene terephthalate) samples was found to be better in spite of having increased degrees of crystallinity. Moreover, the colour fastness properties of the clay‐containing samples were not affected adversely.     

Effect of steady shear on the microstructural evolution of melt‐intercalated polymer/clay nanocomposites

A sheet sample composed of poly(butylene terephthalate) and clay prepared by solid‐state compression was melt‐annealed in a rheometer under steady shear flow to investigate the whole hybridization process. The results of the offline morphology and thermogravimetric analysis as well as Fourier transform infrared characterization show that shear flow can reduce the dynamic process of hybridization, facilitating the formation of an intercalated nanoscale structure. With an increase in the shear intensity, the detachment level of clay increases more remarkably than the swollen degree. However, an increase in the shear intensity does not induce an exfoliated structure but can decrease the average thickness of the clay tactoids, leading to a remarkable enhancement in the thermal stability due to the increase in the effective filling volume of the clay. Furthermore, those intercalated nanocomposites annealed at a high shear rate still present a distinct hierarchical structure, which suggests that steady shear is not as good as dynamic or complex shear for promoting hybridization effectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Properties of poly(butylene terephthalate) chain‐extended by epoxycyclohexyl polyhedral oligomeric silsesquioxane

Epoxycyclohexyl polyhedral oligomeric silsesquioxane (epoxy–POSS) was used to prepare a chain‐extended poly(butylene terephthalate) (PBT) with a twin‐screw extruder. The effect of epoxy–POSS on the melt flow index, mechanical properties, rheological behavior, and thermal properties of chain‐extended PBT was investigated. PBT had an intrinsic viscosity of 1.1 dL/g and a carboxy1 content of 21.6 equiv/10⁶ g, but the PBT chain‐extended with 2 wt % epoxy–POSS had an intrinsic viscosity of 1.7 dL/g and a carboxy1 content lower than 7 equiv/10⁶ g. After the addition of epoxy–POSS, the melt flow index of PBT dramatically decreased, the elongation at break increased greatly, the tensile strength increased slightly, and the thermal stability was also improved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and friction properties of PBT/MMT composites

Poly(butylene terephthalate)/clay composites were prepared by direct melt compounding. Two structures were formed as confirmed by XRD and transmission electron microscopy. The presence of MMT layers does not change the crystal structure and the degree of crystallinity of PBT matrix. The tribological behaviors of neat PBT and PBT/clay composites were studied by the means of a pin‐on‐disk apparatus. It was found that the intercalation of organoclay could help reduce the friction coefficient and the specific wear rate of PBT, while the addition of natural clay was harmful to the friction coefficient and wear resistance of the polymer matrix. The different tribological behaviors of the composites are due to their different morphologies and the difference in the interfacial adhesion between the matrix and the clay platelets. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

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     

Compatibilization of a poly(butylene terephthalate)/poly(ethylene octene) copolymer blends with different amounts of an epoxy resin

New toughened poly(butylene terephthalate) (PBT) materials were obtained by melt blending with 20 wt % poly(ethylene octene) (PEO) copolymer and different levels of a difunctional epoxy resin in a twin‐screw extruder followed by injection‐molding. The presence of neither PEO or epoxy influenced either the phase nature of the two amorphous phases of the blends or the crystallization process of PBT, despite the slight reaction of epoxy with PBT as stated by the observed torque increases. The addition of epoxy led to a decrease in the particle size that stopped due to the concomitant viscosity increase. Supertough PBT‐based blends with an impact strength more than 18‐fold that of PBT were obtained without previous chemical modification of any of the blend components at 1.0 wt % epoxy contents. The interparticle distance was the parameter that controlled notched toughness in these PBT/PEO blends. The adhesion at the interphase was the parameter on which the critical interparticle distance appeared to depend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 260–269, 2004     

Studies on morphology and interphase of poly(butylene terephthalate)/carbon nanotubes nanocomposites

The microstructure of poly(butylene terephthalate) (PBT) nanocomposites was investigated by simultaneous small angle X‐ray scattering/wide angle X‐ray scattering (SAXS/WAXS) measurements at room temperature. The PBT was observed to crystallize in the α‐phase. The dispersion of single‐wall carbon nanotubes (SWCNTs) in PBT, using in situ polymerization, materials with higher degree of crystallinity than neat PBT were produced. SAXS results indicated that the SWCNT may be preferentially distributed in the amorphous phase of PBT, although WAXS results suggested a nucleation ability of SWCNT, which was supported by the DSC results. Much more complex changes were induced by the dispersion of multiwall carbon nanotubes (MWCNTs) in the PBT matrix. Evidence for the formation of an interphase with restricted chain mobility were found by dynamical mechanical thermal analysis (DMTA). Differential scanning calorimetry (DSC) and WAXS showed an increase of the crystallinity of the nanocomposites in comparison to neat PBT. POLYM. ENG. SCI., 50:1571–1576, 2010. © 2010 Society of Plastics Engineers     

Effects of organoclay modification on microstructure and properties of polypropylene–organoclay nanocomposites

We prepared polypropylene nanocomposites based on a modified organoclay with isobutyl trimethoxysilane to investigate the effects of such modifications of organoclay on the microstructure and properties of the nanocomposite. The organoclay was preliminarily intercalated with distearyldimethylammonium bromide via an ion exchange before being grafted with silane. The morphology of the polypropylene–organoclay nanocomposites was characterized by wide‐angle X‐ray diffraction analyses and transmission electron microscopy. The modification of the edges of clay platelets with organic silane resulted in a more uniform dispersion of nonagglomerated tactoids, which consisted of several intercalated clay platelets. However, the unmodified organoclay led to a mixed morphology with both agglomerated and nonagglomerated tactoids. The grafting of the clay edges with organic silane also affected the linear viscoelastic properties of the nanocomposites in the melt state, which was shown to be sensitive to the interaction between the edges of clay platelets as well as to the interaction of the polymer with the platelet edges. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1752–1759, 2006     

Effect of order of mixing on morphology and thermal properties of the compatibilized PBT and ABS alloys/OMT nanocomposites

Poly(butylene terephthalate) (PBT) and acrylonitrile–butadiene–styrene terpolymers (ABS) alloys/organically modified montmorillonite (OMT) nanocomposites using terpolymers of random ethylene, methyl acrylate, and glycidyl methacrylate as the reactive compatibilizer were prepared by different melt‐mixing sequences. The microstructures were characterized by scanning electron microscopy, X‐ray diffraction, transmission electron microscopy, and high‐resolution electron microscopy. It was found that order of mixing affects the dispersion state of OMT in the alloy matrix. The crystallization behavior of PBT in the compatibilized PBT and ABS alloys/OMT nanocomposites was studied by wide angle X‐ray diffraction. It revealed that order of mixing has influence on the preferential crystal growing direction of PBT owing to the antagonistic effect of ABS and OMT. Thermogravimetric analyses and differential scanning calorimetry also showed order of mixing changes the thermal property of the compatibilized PBT and ABS alloys/OMT nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2130–2139, 2007