SYNTHESIS AND CHARACTERIZATION OF ORGANOMONTMORILLONITE AND POLYAMIDE 66/MONTMORILLONITE NANOCOMPOSITES

The montmorillonites (MMTs), layered, smectite-type silicates, were premodified by two different methods priorto the polymer melt intercalation. In one case MMTs were modified with cetyltrimethylammonium bromide (CTAB), andtermed as organomontmorillonites (OMMTs); in the other case MMTs were modified by nylon, and the products were calledmodified montmorillonites (MMMTs). The effects of CTAB and nylon on the MMTs were investigated by using TG andWAXD. The results show that interlayer spacings of CTAN and nylon modified MMTs are larger than that of sodium MMTs.Then, polyamide 66 (PA 66)/MMT nanocomposites were obtained through the method of melt intercalation of polymers. Thenanocomposites were characterized by WAXD, TEM and Molau experiments. The results indicate that the MMTs dispersehomogeneously in the PA 66 matrix. The mechanical properties of nanocomposites, such as tensile properties and flexuralproperties, were also measured and show a tendency to increase with increase of MMT content and reach the maximumvalues at 5phr MMT content. The heat distortion temperature (HDT) of the nanocomposites (7 phr) is about 32 K higher thanthat of pure PA 66.     

Preparation and characterization of anion‐exchange membranes derived from poly(vinylbenzyl chloride‐co‐styrene) and intercalated montmorillonite

In this paper, three organic intercalating agents containing cations [hexadecyl trimethyl ammonium bromide (CTAB), poly(acrylamide‐co‐diallyldimethylammonium chloride), and quaternized polyethyleneimine] are used to prepare intercalated montmorillonites (MMT) by ion‐exchange method. Then the modified MMTs are doped with vinylbenzyl chloride and styrene copolymer [poly(vinylbenzyl chloride‐co‐styrene)] for fabricating composite anion‐exchange membranes (AEM). Fourier transform infrared, X‐raydiffraction, thermogravimetric analysis, scanning electron microscopy, and Mastersizer laser particle size analyzer are employed to characterize the structure and morphology of MMTs and AEMs. The successful intercalation of MMTs is approved, and the MMT intercalated by CTAB shows an interlayer distance of 2.31 nm. The properties of the composite membranes including water uptake, mechanical property, and ionic conductivity are investigated. Among all the AEMs, the composite membrane containing MMT sheets with CTAB demonstrates better compositive performances. It presents an ionic conductivity of 2.09 × 10^?2 S cm^?1 at 80°C and good alkaline solution stability. Copyright © 2016 John Wiley & Sons, Ltd.     

Characterization and thermal degradation studies on polyaniline‐intercalated montmorillonite nanocomposites prepared by a solvent‐free mechanochemical route

Polyaniline (PANI)‐montmorillonite (MMT) nanocomposites were prepared by direct intercalation of aniline molecules into MMT galleries, followed by in situ polymerization within the nano‐interlamellar spaces under solvent‐free conditions. The basal spacing of aniline‐intercalated MMT increased gradually up to 1.5 nm with increasing amounts of aniline loaded. This result suggests that aniline molecules were adsorbed by MMT clay and that intercalated aniline likely located perpendicular to the silicate sheets. After polymerization, X‐ray diffraction and Fourier transform infrared analyses confirmed the successful synthesis of PANI chains between the MMT nano‐interlayers. The scanning electron microscopy images indicated that the surface morphologies of PANI–MMTs were strongly different depending on the PANI content. The electrical conductivities of PANI nanocomposite particles in pressed pellets ranged in the order of between 10^?3 and 10^?2 S/cm. UV–vis spectroscopy and doping level measurement were further used to discuss the conductivities of nanocomposites. The thermal stabilities of PANI–MMT nanocomposites were examined by using thermogravimetric‐differential thermal analysis and derivative thermogravimetric analysis, and both analyses consequently demonstrated the improved thermal stabilities of the PANI chains in the nanocomposites as compared to pure PANI. The thermal stabilities of resulting nanocomposites were strongly related to the PANI content, which increased as the PANI content decreased in the nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2705–2714, 2005     

Dispersibility of clay and crystallization kinetics for in situ polymerized PET/pristine and modified montmorillonite nanocomposites

Nanocomposite materials composed of poly (ethylene terephthalate) (PET) and montmorillonite (MMT) clays were prepared by in situ polymerization. Samples consisted of PET blended with various quantities of either pristine (Na⁺‐MMT) or organically modified MMT (A10‐MMT). The morphology and thermal and mechanical properties were evaluated for each sample. TEM micrographs, acquired at a 20 nm resolution, provide direct evidence of exfoliation of the clay particles into the PET matrix and show the effect of the alkyl‐modifier on clay dispersibility. The dispersion of PET/A10‐MMT was greater than that observed for the PET/Na⁺‐MMT nanocomposites. The greatest degree of exfoliation occurred for PET/A10‐MMT 0.5 wt %. However, PET/Na⁺‐MMT exhibited higher crystallization temperatures and rates suggesting that Na⁺‐MMT is a more efficient nucleating agent. Both mechanically and thermally, PET/A10‐MMT nanocomposites exhibited superior properties over pure PET. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1022–1035, 2008     

Preparation of poly(ethylene terephthalate)/organoclay nanocomposites using a polyester ionomer as a compatibilizer

In this work, poly(ethylene terephthalate)/organically modified montmorillonite (PET/o‐MMT) nanocomposites were prepared via direct melt compounding in a twin‐screw extruder. The main objective was to study the effects of using a polyester ionomer (PETi) as a compatibilizer to promote the intercalation and/or exfoliation of the o‐MMT in the PET. The o‐MMT content was 0, 1, 3, or 5 wt % and the PETi/o‐MMT mass ratio was 0/1, 1/1, or 3/1. The PETi was efficient to promote the intercalation/exfoliation of the o‐MMT in the PET matrix, as revealed by wide angle X‐ray scattering and transmission electron microscopy. Rheological characterization showed that the PET/o‐MMT nanocomposites exhibited a higher complex viscosity at low frequencies than PET, which is characteristic of materials presenting yield strength. Moreover, the higher the content and/or the degree of intercalation/exfoliation of the o‐MMT, the more the nanocomposite behaved like a solid because of a percolated structure formed by the o‐MMT layers, and the more the storage and loss modulus, G′ and G″, became independent of the frequency at low frequencies. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3084–3091, 2007     

Isotactic Poly(propylene)/Monoalkylimidazolium‐Modified Montmorillonite Nanocomposites: Preparation by Intercalative Polymerization and Thermal Stability Study

Summary: Poly(propylene)/monoalkylimidazolium‐modified montmorillonite (PP/IMMT) nanocomposites were prepared by in situ intercalative polymerization of propylene with TiCl₄/MgCl₂/MMT catalyst. The PP synthesized possessed high isotacticity and molecular weight. Both wide‐angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the nanocomposite formation with exfoliated MMT homogeneously distributed in the PP matrix. A thermal stability study revealed that the nanocomposites possess good thermal stability.

X‐ray diffraction patterns of PP/IMMT (MMT = 2.2 wt.‐%) nanocomposite before and after processing.     

The influence of multiple modified MMT on the thermal and fire behavior of poly (lactic acid) nanocomposites

This work reported the preparation and physical properties of biodegradable nanocomposites fabricated using polylactic acid (PLA) and multiple organic modified montmorillonite (MMT). In order to improve the chemical compatibility between PLA and Na‐MMT, the surface of Na‐MMT was first organically modified by cetyl trimethyl ammonium bromide (CTAB) and resorcinol bis(diphenyl phosphate) (RDP) using ion‐exchange and adsorption technique. Both Fourier transform infrared and X‐ray diffraction (XRD) results indicated that CTAB and RDP molecules were intercalated into the galleries of MMT sheets to enlarge the interlayer spacing. Then, the PLA/MMT nanocomposites were prepared by a simple melt‐blending method. The XRD and TEM results of the nanocomposites indicated that the PLA polymer chains inserted into the galleries of co‐modified MMT (C‐MMT) and contained disorderedly intercalated layered silicate layers within a PLA matrix. The C‐MMT nanolayers were homogenously dispersed in PLA matrix, resulting in various property enhancement. The fabricated PLA/C‐MMT nanocomposites with 5.0 wt% addition showed significant enhancements (176%) in the storage modulus compared to that of neat PLA. The thermal stability and fire resistance were also remarkably improved. These improvements are probably because of both the physical barrier effect of the MMT nanosheets and charring effect of the C‐MMT. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation and properties of organo‐modifier free PET/MMT nanocomposites via monomer intercalation and in situ polymerization

In order to prevent the properties, especially transparency, color and health security, of PET/clay nanocomposites from being deteriorated due to the thermal degradation of clay organo‐modifer, we had directly modified sodium montmorillonite (Na⁺‐MMT) with PET's monomer, bis (hydroxyethyl) terephthalate (BHET) which had a degradation temperature higher than 400°C, and successfully prepared the hybrids via in situ polymerization. Nanodispersion of clay and the intercalated morphology were determined, and compared with PET/Na⁺‐MMT hybirds in which Na⁺‐MMT was directly added without any treatment. Improved mechanical properties and T_g were observed for the prepared PET/ BHET‐modified clay composites. More importantly, the film produced from the composites had the same transparency as that of pure PET even when 2 wt% of clay was added. Non‐isothermal and isothermal crystallization experiments showed a very good neculation capability of the nano‐dispersed clay, particularly at higher crystallization temperatures. Copyright © 2009 John Wiley & Sons, Ltd.     

Multiple melting and crystallization of nylon‐66/montmorillonite nanocomposites

Nylon‐66 nanocomposites were prepared by melt‐compounding nylon‐66 with organically modified montmorillonite (MMT). The organic MMT layers were exfoliated in a nylon‐66 matrix as confirmed by wide‐angle X‐ray diffraction (WAXD) and transmission electron microscopy. The presence of MMT layers increased the crystallization temperature of nylon‐66 because of the heterogeneous nucleation of MMT. Multiple melting behavior was observed in the nylon‐66/MMT nanocomposites, and the MMT layers induced the formation of form II spherulites of nylon‐66. The crystallite sizes L₁₀₀ and L₀₁₀ of nylon‐66, determined by WAXD, decreased with an increasing MMT content. High‐temperature WAXD was performed to determine the Brill transition in the nylon‐66/MMT nanocomposites. Polarized optical microscopy demonstrated that the dimension of nylon‐66 spherulites decreased because of the effect of the MMT layers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2861–2869, 2003     

Heterogeneous copper‐catalyzed oxidative coupling of oxime acetates with sodium sulfinates: An efficient and practical synthesis of β‐keto sulfones

An efficient and practical route to β‐keto sulfones has been developed through heterogeneous oxidative coupling of oxime acetates with sodium sulfinates by using an MCM‐41‐supported Schiff base‐pyridine bidentate copper (II) complex [MCM‐41‐Sb,Py‐Cu (OAc)₂] as the catalyst and oxime acetates as an internal oxidant, followed by hydrolysis. The reaction generates a variety of β‐keto sulfones in good to excellent yields. This new heterogeneous copper (II) catalyst can be easily prepared via a simple procedure from readily available and inexpensive reagents and exhibits the same catalytic activity as Cu (OAc)₂. MCM‐41‐Sb,Py‐Cu (OAc)₂ is also easy to recover and is recyclable up to eight times with almost consistent activity.     

Thermogravimetric study of <Emphasis Type="Italic">n</Emphasis>-alkylammonium-intercalated montmorillonites of different cation exchange capacity

Three n-alkylammonium salts of varying alkyl chain length were ion exchanged with montmorillonites (MMT) of different cation exchange capacity (CEC). The intercalated MMTs were characterized by thermogravimetry (TG), XRD, FTIR to acquire an insight into the intergallery structural arrangement of the organic alkylammonium cations (AAC). The increment in the intergallery spacing from XRD pattern was correlated with chain length and interlayer arrangement of AAC. Multiple organic mass-loss stages in thermogravimetric analysis indicate two types of anchorage of AAC in intercalated clay. CEC of MMT was found to influence the intergallery confinement and excess adsorption of AAC.     

Structure and properties of poly(ethylene terephthalate)/Na+‐montmorillonite nanocomposites prepared by solid state shear milling (S3M) method

This article reported a novel technology, solid state shear milling (S³M), to prepare poly(ethylene terephthalate)/Na⁺‐montmorillonite nanocomposites using the pristine Na⁺‐MMT without organic modification so as to avoid the problem that the organic modifiers, used for MMT treatment will decompose at high processing temperature of PET, and the structure and properties of the obtained samples were investigated. XRD and TEM analyses showed that Na⁺‐MMT layers were partially delaminated and intercalated, and uniformly dispersed in the PET matrix when suffering from the strong three dimensional shearing forces of pan‐milling. DSC analysis showed that Na⁺‐MMT serves as a nucleating agent, increasing the crystallization rate as well as the crystallization temperature of PET. The properties such as thermal stability and tensile strength of the PET/Na⁺‐MMT nanocomposites prepared by S³M got remarkably improved. Solid state shear milling (S³M) method was a simple and efficient method to get polymer/Na⁺‐MMT nanocomposites with pretty good performances without organic modification of pristine Na⁺‐MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 807–817, 2008     

In situ intercalative polymerization of conducting polypyrrole/montmorillonite nanocomposites

Conducting polypyrrole (PPy)‐montmorillonite (MMT) clay nanocomposites have been synthesized by the in situ intercalative polymerization method. The PPy‐MMT nanocomposites are characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. XRD patterns show that after polymerization by the in situ intercalative method with ammonium persulfate and 1 M HCl, an increase in the basal spacing from 1.2 to 1.9 nm was observed, signifying that PPy is synthesized between the interlayer spaces of MMT. TEM and SEM micrographs suggest that the coexistence of intercalated MMT layers with the PPy macromolecules. FTIR reveals that there might be possible interfacial interactions present between the MMT clay and PPy matrix. The study also shows that the introduction of MMT clay results in thermal stability improvement of the PPy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2279–2285, 2008     

Electrical conductivity of poly(ethylene terephthalate)/expanded graphite nanocomposites prepared by in situ polymerization

Nanocomposites based on poly(ethylene terephthalate) (PET) and expanded graphite (EG) have been prepared by in situ polymerization. Morphology of the nanocomposites has been examined by electronic microscopy. The relationship between the preparation method, morphology, and electrical conductivity was studied. Electronic microscopy images reveal that the nanocomposites exhibit well dispersed graphene platelets. The incorporation of EG to the PET results in a sharp insulator‐to‐conductor transition with a percolation threshold (?_c) as low as 0.05 wt %. An electrical conductivity of 10^?3 S/cm was achieved for 0.4 wt % of EG. The low percolation threshold and relatively high electrical conductivity are attributed to the high aspect ratio, large surface area, and uniform dispersion of the EG sheets in PET matrix. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Preparation,morphology and electrical conductivity of polyaniline/polyoxyalkylene–montmorillonite exfoliated nanocomposites

Polyaniline (PANI)/organoclay exfoliated nanocomposites containing different organoclay contents (14–50 wt%) were prepared. PANI emeraldine base (EB) and oligomeric PANI (o‐PANI) were intercalated into montmorillonite (MMT) modified by four types of polyoxyalkylene diamine or triamine (organoclay) using N‐methyl pyrolidinone (NMP) as a solvent in the presence of 0.1 M HCl. o‐PANI and EB have been synthesized by oxidative polymerization of aniline using ammonium peroxydisulfate (APS). Infrared absorption spectra (IR) confirm the electrostatic interaction between negatively charged surface of MMT and positively charged sites in PANI. X‐ray diffraction (XRD) studies disclosed that the d₀₀₁ spacing between interlamellar surface disappeared at low content of the organoclay. The morphology of these materials was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrical conductivities of the PANI‐organoclay and o‐PANI‐organoclay nanocomposites were 1.5 × 10^?3–2 × 10^?4 and 9.5 × 10^?7–1.8 × 10^?9 S/cm, respectively depending on the ratio of PANI. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and characterization of rigid poly (vinyl chloride)/MMT nanocomposites

In this article, a Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on the characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. It is observed that the fusion time and temperature of the rigid PVC/Na⁺‐MMT nanocomposites are decreased with increasing the amount of Na⁺‐MMT. On the contrast, the fusion time and temperature of the rigid PVC/O‐MMT nanocomposites are increased with increasing the amount of O‐MMT. Results of X‐ray diffraction (XRD) and transmission electron microscope (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT (including PVC/Na⁺‐MMT and PVC/O‐MMT) nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to those of pristine PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1465–1474, 2005     

Preparation of functionalized montmorillonites and their application in supported zirconocene catalysts for ethylene polymerization

Ethylene polymerization was carried out with zirconocene catalysts supported on montmorillonite (or functionalized montmorillonite). The functionalized montmorillonite was from simple ion exchange of [CH₃O₂CCH₂NH₃]⁺ (MeGlyH⁺) ions with interlamellar cations of layered montmorillonites. The functionalized montmorillonites [high‐purity montmorillonite (MMT)‐MeGlyH⁺] had larger interlayer spacing (12.69 Å) than montmorillonites without treatment (9.65 Å). The zirconocene catalyst system [Cp₂ZrCl₂/methylaluminoxane (MAO)/MMT‐MeGlyH⁺] had much higher Zr loading and higher activities than those of other zirconocene catalyst systems (Cp₂ZrCl₂/MMT, Cp₂ZrCl₂/MMT‐MeGlyH⁺, Cp₂ZrCl₂/MAO/MMT, [Cp₂ZrCl]⁺[BF₄]/MMT, [Cp₂ZrCl]⁺[BF₄]^?/MMT‐MeGlyH⁺, [Cp₂ZrCl]⁺[BF₄]^?/MAO/MMT‐MeGlyH⁺, and [Cp₂ZrCl]⁺[BF₄]^?/MAO/MMT). The polyethylenes with good bulk density were obtained from the catalyst systems, particularly (Cp₂ZrCl₂/MAO/MMT‐MeGlyH⁺). MeGlyH⁺ and MAO seemed to play important roles for preparation of the supported zirconocenes and polymerization of ethylene. The difference in Zr loading and catalytic activity among the supported zirconocene catalysts is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1892–1898, 2002     

Thermal characterization of montmorillonite clays saturated with various cations

Emanation thermal analysis (ETA), thermogravimetry and high temperature XRD were used to characterize the thermal behavior during dehydration of natural Na montmorillonite (Upton Wyoming, USA) and homoionic montmorillonite (MMT) samples saturated with different cations, i.e. Li⁺, Cs⁺, NH₄⁺, Mg²⁺ and Al³⁺. ETA results characterized radon mobility and microstructure changes that accompanied the mass loss of the samples due to dehydration on heating in air. A collapse of interlayer space between the silicate sheets after water release from the MMT samples was characterized by a decrease of the radon release rate, ΔE. Decreases in c-axis basal spacing (d ₀₀₁) values determined from XRD patterns for the different montmorillonite samples follow the sequence:

Exploitation of introducing of catalytic centers into layer galleries of layered silicates and related epoxy nanocomposites. I. Epoxy nanocomposites derived from montmorillonite modified with catalytic surfactant‐bearing carboxyl groups

Montmorillonite (MMT) was modified with the acidified cocamidopropyl betaine (CAB) and the resulting organo‐montmorillonite (O‐MMT) was dispersed in an epoxy/methyl tetrahydrophthalic anhydride system to form epoxy nanocomposites. The intercalation and exfoliation behavior of the epoxy nanocomposites were examined by X‐ray diffraction and transmission electron microscopy. The curing behavior and thermal property were investigated by in situ Fourier transform infrared spectroscopy and DSC, respectively. The results showed that MMT could be highly intercalated by acidified CAB, and O‐MMT could be easily dispersed in epoxy resin to form intercalated/exfoliated epoxy nanocomposites. When the O‐MMT loading was lower than 8 phr (relative to 100 phr resin), exfoliated nanocomposites were achieved. The glass‐transition temperatures (T_g's) of the exfoliated nanocomposite were 20 °C higher than that of the neat resin. At higher O‐MMT loading, partial exfoliation was achieved, and those samples possessed moderately higher T_g's as compared with the neat resin. O‐MMT showed an obviously catalytic nature toward the curing of epoxy resin. The curing rate of the epoxy compound increased with O‐MMT loading. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1192–1198, 2004     

Extruder‐made TPO nanocomposites. I. Effect of maleated polypropylene and organoclay ratio on the morphology and mechanical properties

PP/PP‐g‐MA/MMT/EOR blend nanocomposites were prepared in a twin‐screw extruder at fixed 30 wt % elastomer and 0 to 7 wt % MMT content. Elastomer particle size and shape in the presence of MMT were evaluated at various PP‐g‐MA/organoclay masterbatch ratios of 0, 0.5, 1.0, and 1.5. The organoclay dispersion facilitated by maleated polypropylene serves to reduce the size of the elastomer dispersed phase particles and facilitates toughening of these blend nanocomposites. The rheological data analysis using modified Carreau‐Yasuda model showed maximum yield stress in extruder‐made nanocomposites compared with nanocomposites of reactor‐made TPO. Increasing either MMT content or the PP‐g‐MA/organoclay ratio can drive the elastomer particle size below the critical particle size below which toughness is dramatically increased. The ductile‐brittle transition shift toward lower MMT content as the PP‐g‐MA/organoclay ratio is increased. The D‐B transition temperature also decreased with increased MMT content and masterbatch ratio. Elastomer particle sizes below ～1.0 μm did not lead to further decrease in the D‐B transition temperature. The tensile modulus, yield strength, and elongation at yield improved with increasing MMT content and masterbatch ratio while elongation at break was reduced. The modified Mori‐Tanaka model showed better fit to experimental modulus when the effect of MMT and elastomer are considered individually. Overall, extruder‐made nanocomposites showed balanced properties of PP/PP‐g‐MA/MMT/EOR blend nanocomposites compared with nanocomposites of reactor‐made TPO. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012