Nanocomposites of poly(trimethylene terephthalate) with organoclay

Two different kinds of clay were organomodified with cetylpyridinium chloride (CPC) as an intercalation agent. Poly(trimethylene terephthalate) (PTT)/organoclay nanocomposites were prepared by the solution intercalation method. Wide‐angle X‐ray diffraction (WAXD) indicated that the layers of clay were intercalated by CPC and the interlayer spacing was a function of the cationic exchange capacity (CEC) of the clay: the higher the CEC, the larger the interlayer spacing is. The WAXD studies showed that the interlayer spacing of organoclay in the nanocomposites depends on the amount of organoclay. From the results of differential scanning calorimetry analysis it was found that clay behaves as a nucleating agent and enhances the crystallization rate of PTT. The maximum enhancement of the crystallization rate for the nanocomposites was observed in nanocomposites containing about 5 wt % organoclay with a range of 1–15 wt %. The thermal stability of the nanocomposites was enhanced by the addition of 1–10 wt % organoclay as found from thermogravimetric analysis. The thermal stability of the PTT/organoclay nanocomposites was related to the organoclay content and the dispersion in the PTT matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3315–3322, 2003     

Synthesis and characterization of poly(ethylene terephthalate)/attapulgite nanocomposites

A kind of clay with fibrous morphology, attapulgite (AT), was used to prepare poly (ethylene terephthalate) (PET)/AT nanocomposites via in situ polymerization. Attapulgite was modified with Hexadecyltriphenylphosphonium bromide and silane coupling agent (3‐glycidoxypropltrimethoxysilane) to increase the dispersion of clay particles in polymer matrix and the interaction between clay particles and polymer matrix. FTIR and TGA test of the organic‐AT particles investigated the thermal stability and the loading quantity of organic reagents. XRD patterns and SEM micrographs showed that the organic modification was processed on the surface of rod‐like crystals and did not shift the crystal structure of silicate. For PET/AT nanocomposites, it was revealed in TEM that the fibrous clay can be well dispersed in polymer matrix with the rod‐like crystals in the range of nanometer scale. The diameter of rod‐like crystal is about 20 nm and the length is near to 500 nm. The addition of the clay particles can enhance the thermal stability and crystallization rate of PET. With the addition of AT in PET matrix, the flexural modulus of those composites was also increased markedly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1279–1286, 2007     

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     

Synthesis and characterization of sulfonated poly(ethylene terephthalate)/montmorillonite nanocomposites

Sulfonated poly(ethylene terephthalate) (SPET)/montmorillonite nanocomposites were prepared by in situ intercalative polymerization. The microstructure, morphology, and properties of the nanocomposites were studied with wide‐angle X‐ray diffraction, transmission electron microscopy, atomic force microscopy, differential scanning calorimetry, and thermogravimetric analysis. The results indicated that an increase in the ? SO₃Na content improved the dispersion of organically modified montmorillonite in the SPET ionomer matrix, and the dispersed layered silicates in the SPET matrix acted as nucleating agents in SPET crystallization processes and improved the thermal stability of SPET. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1150–1156, 2005     

Crystalline morphology and isothermal crystallization kinetics of poly(ethylene terephthalate)/clay nanocomposites

A poly(ethylene terephthalate) (PET)/montmorillonite clay nanocomposite was synthesized via in situ polymerization. Microscopic studies revealed that in an isothermal crystallization process, some crystallites in the nanocomposite initially were rod‐shaped and later exhibited three‐dimensional growth. The crystallites in the nanocomposite were irregularly shaped, rather than spherulitic, being interlocked together without clear boundaries, and they were much smaller than those of neat PET. With Avrami analysis, the isothermal crystallization kinetic parameters (the Avrami exponent and constant) were obtained. The rate constants for the nanocomposite demonstrated that clay could greatly increase the crystallization rate of PET. The results for the Avrami exponent were consistent with the observation of the rodlike crystallites in the PET/clay nanocomposite during the initial stage. Wide‐angle X‐ray scattering and Fourier transform infrared studies showed that, in comparison with neat PET, the crystal lattice parameters and crystallinity of the nanocomposite did not change significantly, whereas more defects may have been present in the crystalline regions of the nanocomposite because of the presence of the clay. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1381–1388, 2004     

Morphology and mechanical properties of polypropylene/organoclay nanocomposites

Polypropylene (PP) nanocomposites were prepared by melt intercalation in an intermeshing corotating twin‐screw extruder. The effect of molecular weight of PP‐MA (maleic anhydride‐ modified polypropylene) on clay dispersion and mechanical properties of nanocomposites was investigated. After injection molding, the tensile properties and impact strength were measured. The best overall mechanical properties were found for composites containing PP‐MA having the highest molecular weight. The basal spacing of clay in the composites was measured by X‐ray diffraction (XRD). Nanoscale morphology of the samples was observed by transmission electron microscopy (TEM). The crystallization kinetics was measured by differential scanning calorimetry (DSC) and optical microscopy at a fixed crystallization temperature. Increasing the clay content in PP‐ MA330k/clay, a well‐dispersed two‐component system, caused the impact strength to decrease while the crystallization kinetics and the spherulite size remained almost the same. On the other hand, PP/PP‐MA330k/clay, an intercalated three‐component system containing some dispersed clay as well as the clay tactoids, showed a much smaller size of spherulites and a slight increase in impact strength with increasing the clay content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1562–1570, 2002     

Preparation and properties of poly(ethylene terephthalate)/ATO nanocomposites

Antimony doped tin oxide (ATO) nanoparticles modified poly(ethylene terephthalate) (PET) composites used for manufacturing antistatic PET fiber were synthesized by in situ polymerization. The crystallization and multiple melting behavior of the nanocomposites were systemically investigated by means of Differential Scanning Calorimeter (DSC), Fourier Transform Infrared (FTIR), X‐ray Diffraction (XRD) techniques. The degree of crystallinity in nanocomposites increased with increasing ATO content. Smaller and more incomplete crystals are presented in the crystalline regions of the nanocomposites with increasing the content of ATO, which could be attributed to heterogeneous nucleation effects of ATO nanoparticles. Dynamic Mechanical Analysis (DMA) measurements showed that the storage moduli of the nanocomposites increased with increasing the content of ATO, due to formation of immobilized layer between polymer and filler. The interactions between ATO and PET molecules result in high tan δ for the PET/ATO nanocomposites. Percolation threshold of PET/ATO hybrid fibers prepared by the nanocomposites at room temperature was as low as 1.05 wt %, much lower than that of the composites filled with conventional conductive particles. Adding ATO nanoparticles obviously improves the conductivity of PET. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and characterization of poly(hydroxybutyrate‐co‐hydroxyvalerate)–organoclay nanocomposites

This study describes the microstructure and thermal and mechanical properties of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHB/HV)–organoclay nanocomposites prepared by melt intercalation using Cloisite 30B, a monotallow bis‐hydroxyethyl ammonium‐modified montmorillonite clay. X‐ray diffractometry and transmission electron microscopy analyses clearly confirm that an intercalated microstructure is formed and finely distributed in the PHB/HV copolymer matrix because PHB/HV has a strong hydrogen bond interaction with the hydroxyl group in the organic modifier of Cloisite 30B. The nanodispersed organoclay also acts a nucleating agent, increasing the temperature and rate of crystallization of PHB/HV; therefore, the thermal stability and tensile properties of the organoclay‐based nanocomposites are enhanced. These results confirm that the organoclay nanocomposite greatly improves the material properties of PHB/HV. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 525–529, 2003     

Impact,thermal, and morphological properties of functionalized rubber toughened‐poly(ethylene terephthalate) nanocomposites

In this study, poly(ethylene terephthalate)/organo‐montmorillonite (PET/OMMT) nanocomposites were melt‐compounded using twin screw extruder followed by injection molding. Maleic anhydride grafted styrene‐ethylene/butylene‐styrene (SEBS‐g‐MAH) was used to improve the impact properties of the PET/OMMT nanocomposites. The notched and un‐notched impact strength of PET/OMMT nanocomposites increased at about 2.5 times and 5.5 times by the addition of 5 wt % of SEBS‐g‐MAH. Atomic force microscopy (AFM) scans were taken from the polished surface of both PET/OMMT and SEBS‐g‐MAH toughened PET/OMMT nanocomposites. The addition of SEBS‐g‐MAH altered the phase structure and clay dispersion in PET matrix. It was found that some of the OMMT silicate layers were encapsulated by SEBS‐g‐MAH. Further, the addition of SEBS‐g‐MAH decreased the degree of crystallinity of the PET/OMMT nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Crystallization behavior of poly(L‐lactic acid)/montmorillonite nanocomposites

In this study, we modified montmorillonite (MMT) with dilauryl dimethyl ammonium bromide (DDAB) and then exfoliated the structures in a poly(L ‐lactic acid) (PLLA) matrix. We used polar optical microscopy and X‐ray diffraction (XRD) to examine the morphologies of the resulting composites, differential scanning calorimetry to study the melting and crystallization behavior, and Fourier transform infrared (FTIR) and Raman spectroscopy to measure the influence of the intermolecular interactions between PLLA and MMT on the isothermal crystallization temperature. We found that the DDAB‐modified MMT was distributed uniformly in the PLLA matrix. At temperatures ranging from 130 to 140°C, the crystalline morphology resembled smaller Maltese cross‐patterned crystallites; at temperatures from 150 to 170°C, however, the number of crystallites decreased, their sizes increased, and they possessed ringed spherulite structures. In the XRD spectra, the intensity of the diffraction peaks of the 200/110 and 203 facets of the PLLA/MMT nanocomposites decreased as the crystallization temperature increased. In the FTIR spectra, the absorption peak of the C?O groups split into two signals at 1748 and 1755 cm^?1 when the isothermal crystallization temperature was higher than 140°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Decomposition of poly(ethylene glycol) in nanocomposites

Poly(ethylene glycol) (PEG) has been widely used in studies of polymer–clay nanocomposites because it readily intercalates in smectite clays. Nanocomposites were formed from PEG with molecular weights (M_w) ranging from 300 to 20,000, as evidenced by expansion of the basal planar spacing of the clay (d₀₀₁) in X‐ray diffraction. However PEG with high molecular weight (≥ 10,000) readily underwent degradation during preparation of composites when heated at low temperature (60°C) due to oxidative attack. Molecular weight distribution determined by gel permeation chromatography showed that this degradation always happened with or without the presence of clay and it became more serious when the molecular weight was higher. The reduction in pH of aqueous PEG solutions after degradation increased with molecular weight. Since d₀₀₁ was independent of molecular weight over a wide range, such degradation cannot be detected by this method. Precautions against oxidative attack are therefore recommended to avoid decomposition when preparing PEG–clay nanocomposites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 548–552, 2004     

Interface structure of poly(ethylene terephthalate)/silica nanocomposites

The interface structure of the poly(ethylene terephthalate) (PET)/silica nanocomposites was characterized by Fourier transform infrared and solid-state nuclear magnetic resonance. Our study reveals that PET chains are grafted onto the surface of silica nanoparticles, and they form branched and lightly crosslinking structures during the polycondensation. Gel permeation chromatography measurements indicate that the grafted PET chains have a lower molecular weight and broader distribution. Furthermore, a model has been developed to elucidate the interaction of an entanglement network between silica and PET chains that lead to enhancements of G′, G″ and η* values of PET/2 wt% silica nanocomposites.     

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     

Electrical conductivity of poly(ethylene terephthalate) modified by titanium plasma

Ion‐implantation‐induced electrical conductivity in a polymer surface is known to have a different mechanism from that of metals and semiconductors. We used a technique called plasma immersion ion implantation and deposition and combined it with a titanium cathodic vacuum arc to modify the surface electrical conductivity of poly(ethylene terephthalate) (PET). The conductivity curve as a function of temperature well fitted the Mott hopping model, which has been proposed for many disordered systems. In addition, we also observed conductivity degradation when modified PET was kept at room temperature. The degradation showed a quasi‐exponential decay as a function of time, that is, an aging effect, which has been seldom reported in the literature to the best of our knowledge. This could have resulted from the unusual structure of PET's surface after ion implantation. A new formula for electrical conductivity in modified PET is proposed that considers both temperature and aging effects. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Antinucleating action of polystyrene on the isothermal cold crystallization of poly(ethylene terephthalate)

The effect of polystyrene (PS) on the kinetics of the cold crystallization of poly(ethylene terephthalate) (PET) was thoroughly investigated. The PET/PS blends were essentially immiscible, as observed by dynamic mechanical thermal analysis, which showed two distinct glass‐transition temperatures, and by scanning electron microscopy. The neat PET and its blends were isothermally cold‐crystallized at various temperatures, and the kinetic parameters were determined with the Avrami approach. PET and its blends presented values of the Avrami exponent close to 2, and the kinetic constant increased with the crystallization temperature increasing. For all the crystallization temperatures studied, the presence of only 1 wt % PS significantly reduced the rate of cold crystallization of PET. A further increase in the PS concentration did not show any significant influence. The blends presented higher values of the activation energy for cold crystallization, which was estimated from Arrhenius plots. The equilibrium melting temperature of neat PET was determined on the basis of the linear Hoffman–Weeks extrapolative method to be ～ 255°C. This value decreased in the presence of PS, and this suggested limited solubility between PET and PS. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter was obtained, and it was shown to be higher for the neat PET than for the blends. Moreover, a transition of regimes (I → II) was observed in both PET and its blends. From the investigations conducted here, it is clear that PS in small amounts causes a reduction in the rate of PET crystallization, acting as an antinucleating agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of poly(butylene succinate)/epoxy group functionalized organoclay

Poly(butylene succinate) (PBS)/clay nanocomposites were prepared by condensation polymerization of 1,4‐butanediol and succinic acid in the presence of an organoclay containing epoxy groups (TFC) and titanium(IV) butoxide as a catalyst. The intercalation and exfoliation of the clay layers in the resulting composite were examined using X‐ray scattering and transmission electron microscopy. The role of the epoxy groups of TFC was investigated for the improvement of the morphology of the composites. The silicate layers in the composite were exfoliated to a greater extent as the epoxy content of TFC was increased from 0.245 to 0.359 mmol g^?1, while only intercalated morphology was obtained when no epoxy was present. The improved morphologies were attributed to the enhanced interfacial interactions between PBS and TFC through a chemical reaction of the epoxy groups with the end groups of the PBS. The nonisothermal crystallization process of the composites as well as that of neat PBS is well represented by the Avrami equation as modified by Jeziorny [Jeziorny A, Polymer 19 :1142 (1978)]. The crystallization of the composite took place faster as the epoxy content of the clay increased, due to the more effective nucleation of the well‐dispersed TFC layers. Copyright © 2007 Society of Chemical Industry     

Synthesis and characterization of polyaniline–organoclay nanocomposites

Polyaniline (PANI)–organoclay nanocomposites were prepared. Intercalation of aniline monomer into montmorillonite (MMT) modified by polyoxyalkylene was followed by subsequent oxidative polymerization of the aniline in the interlayer spacing. The organoclay was prepared by cation exchange process between sodium cation in MMT and onium ion in four different types of polyoxyalkylene diamine and triamine with different molecular weight. Infrared spectra confirm the electrostatic interaction between the positively charged onium group (NH₃⁺) and the negatively charged surface of MMT. X‐ray diffraction analysis provides a structural information. The absence of d₀₀₁ diffraction band in the nanocomposites was observed at certain types and contents of organoclay. Scanning electron microscopy and transmission electron microscopy were employed to determine the dispersion of the clay into PANI. The thermal degradation behavior of PANI in the nanocomposites has been investigated by thermogravimetric analysis. The weight loss suggests that the PANI chains in the nanocomposites are more thermally stable than pristine PANI. This improvement is attributed to the presence of nanolayers with high aspect ratio acting as barriers, thus shielding the diffusion of degraded PANI from the nanocomposites. The electrical conductivity of the nanocomposites was increased 30 times more than that of pure MMT at a certain concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and crystallization of poly(ethylene terephthalate)/SiO2 nanocomposites by in‐situ polymerization

Poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were prepared by in situ polymerization. The dispersion and crystallization behaviors of PET/SiO₂ nanocomposites were characterized by means of transmission electron microscope (TEM), differential scanning calorimeter (DSC), and polarizing light microscope (PLM). TEM measurements show that SiO₂ nanoparticles were well dispersed in the PET matrix at a size of 10–20 nm. The results of DSC and PLM, such as melt‐crystalline temperature, half‐time of crystallization and crystallization kinetic constant, suggest that SiO₂ nanoparticles exhibited strong nucleating effects. It was found that SiO₂ nanoparticles could effectively promote the nucleation and crystallization of PET, which may be due to reducing the specific surface free energy for nuclei formation during crystallization and consequently increase the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 655–662, 2006