Modified Montmorillonite Nanocomposites Research Articles

Polycyanurate–Organically Modified Montmorillonite Nanocomposites: Structure–Dynamics–Properties Relationships

Polycyanurate‐modified montmorrilonite (PCN‐MMT) nanocomposites were synthesized by polymerization of dicyanate ester of bisphenol A in the presence of MMT dispersed by ultrasound. Techniques of IR spectroscopy, WAXD, and TEM were applied to study polymerization kinetics and structure of the nanocomposites prepared, whereas their dynamics and thermal/mechanical properties over the −30 to 420°C range were studied by using DSC, laser‐interferometric creep rate spectroscopy (CRS), and dielectric relaxation spectroscopy (DRS) techniques. It was shown that a small amount of MMT additive acts as a catalyst of polymerization and results in the formation of complicated intercalated/exfoliated structures, as well as strongly modifies the dynamics in the PCN network. Pronounced dynamic heterogeneity was observed for PCN/MMT nanocomposites. Along with the main PCN glass transition, two new glass transitions, at much higher and much lower temperatures, were revealed as a consequence of constrained dynamics in matrix interfacial nanolayers and due to incomplete local cross‐linking in the PCN matrix, respectively. In addition, increased sub‐T g mobility was observed in these nanocomposites. A two‐fold rise of modulus of elasticity as well as increasing thermal stability and arising microplasticity at low temperatures, promoting, obviously, improved crack resistance in a brittle PCN network, were found for the PCN‐MMT nanocomposites.

Polypropylene/montmorillonite Nanocomposites for Food Packaging

AbstractPolypropylene / organically modified montmorillonite nanocomposites were prepared using polypropylene-graft-maleic anhydride as compatibilizer by the melt blending method. The structural, mechanical and gas barrier properties of the prepared nanocomposites containing various amounts of organoclay (i.e. 0, 2, 5, 7 and 10 wt%) were investigated to evaluate their potential as food packaging materials. The X-ray diffraction (XRD) profiles of the nanocomposites and the transmission electron microscopy (TEM) micrograph showed that polypropylene chains have intercalated between silicate layers of organoclay. The mechanical properties tests showed that the tensile modulus and strength of the nanocomposites increased on increasing the clay loading, while the strain at the break decreased. The gas permeability tests demonstrated that adding organoclay into polypropylene matrix enhances the barrier property of the matrix against O2 , CO2 and water vapour.

In vitro adsorption of zearalenone by cetyltrimethyl ammonium bromide-modified montmorillonite nanocomposites

In vitro adsorption of zearalenone (ZEA) by cetyltrimethyl ammonium bromide (CTAB)-modified montmorillonite nanocomposites (CMN) was investigated. The particle size of CMN was below 38.06 nm determined with atomic force microscopes. The maximum adsorption of ZEA by CMN at 37 °C and pH 7.0 was 8.83 and 5.07 mg/g calculated with Langmuir and Freundlich adsorption isotherms, respectively, whereas the maximum adsorption by MN was 0.60 and 0.19 mg/g, respectively. The effect of pH, temperature, ZEA concentration, and adsorbent concentration on ZEA adsorption were also studied and they all had certain influence on ZEA adsorption, especially the pH. The coexistence of Ca 2+, Fe 3+, Fe 2+, vitamin E and/or lysine showed no significant influence on ZEA adsorption by CMN, suggesting that the nanograde particle size and hydrophobic property of CMN are responsible for the specific adsorption. These results suggest that CMN has the potential as a novel and promising nanograde adsorbent to bind the mycotoxin effectively in the animal gastrointestinal tract to reduce its absorption.

Synthesis of exfoliated polyamide 6,6/organically modified montmorillonite nanocomposites by in situ interfacial polymerization

AbstractPolyamide 6,6 (PA 6,6)/organically modified montmorillonite (OMMT) nanocomposites were prepared by a novel method, using direct interfacial polymerization of an aqueous hexamethylene diamine and a nonaqueous adipoyl chloride in dichloromethane solution containing different amounts of OMMT dispersed nanoparticles. The state of dispersion of OMMT in the PA 6,6 matrix was investigated by means of X‐ray diffraction, as well as transmission electronic microscopy. The results indicated that the OMMT nanoparticles were dispersed homogeneously and nearly exfoliated in the PA 6,6 matrix. The random arrangement of clay platelets in the PA 6,6 matrix, exfoliation, and intercalation of clays between the PA 6,6 matrix were distinguished. The amount of the incorporated OMMT in the PA 6,6 matrix was determined by means of TGA technique. Furthermore it was found that addition of a small amount of OMMT dramatically improved the thermal stability of PA 6,6. The TGA thermograms of all the synthesized nanocomposite samples showed an interesting unexpected lag in the weight loss at high temperatures, which could be another evidence for formation of fully exfoliated nanocomposites structures, with improved thermal stability. Nucleating effect of the OMMT nanoparticles and their influence on crystallization behavior of PA 6,6 was confirmed by DSC. Finally it is concluded that the in situ interfacial polycondensation is a suitable method for synthesis of nanocomposites with well dispersed structures and enhanced properties. POLYM. COMPOS., 28:733–738, 2007. © 2007 Society of Plastics Engineers

Study on Preparation and Properties of Acrylonitrile‐Butadiene‐Styrene/Montmorillonite Nanocomposites

Acrylonitrile‐butadiene‐styrene (ABS)/organically modified montmorillonite nanocomposites were prepared by melt blending in an internal mixer, and their morphology, rheological behaviors and mechanical properties were characterized using X‐ray diffraction (XRD), capillary rheometer and tensile, flexural and impact tests. X‐ray diffraction studies revealed the presence of intercalated structure for the prepared nanocomposites and good dispersion of clay layers at low levels of its loading. From the rheological investigations it was observed that the prepared nanocomposites and their pristine counterpart have shear‐thinning behavior, obeying the power law equation. At low shear rates, the steady shear viscosity and shear stress of the nanocomposites increase with increasing of nanoclay content. However, at high shear rates they behave similar to pure ABS. It was shown that the flow activation energy (E) values increase with increasing of nanoclay content. Mechanical tests showed that the flexural moduli of the nanocomposites increase with increase of nanoclay loading, but the flexural strength and the tensile and impact properties decrease with increase of nanoclay content.

Recycled PET nanocomposites improved by silanization of organoclays

AbstractRecycled PET/organo‐modified montmorillonite nanocomposites were prepared via melt compounding as a promising possibility of the used beverage bottles recovery. According to our previous work, the three suitable commercial organoclays Cloisite 25A, 10A, and 30B were additionally modified with [3‐(glycidyloxy)propyl]trimethoxysilane, hexadecyltrimethoxysilane and (3‐aminopropyl)trimethoxysilane. The selected organoclays were compounded in the concentration 5 wt % and their degree of intercalation/delamination was determined by wide‐angle X‐ray scattering and transmission electron microscopy. Modification of Cloisite 25A with [3‐(glycidyloxy)propyl]trimethoxysilane increased homogeneity of silicate layers in recycled PET. Additional modification of Cloisite 10A and Cloisite 30B led to lower level of delamination concomitant with melt viscosity reduction. However, flow characteristics of all studied organoclay nanocomposites showed solid‐like behavior at low frequencies. Silanization of commercial organoclays had remarkable impact on crystallinity and melt temperature decrease accompanied by faster formation of crystalline nuclei during injection molding. Thermogravimetric analysis showed enhancement of thermal stability of modified organoclays. The tensile tests confirmed significant increase of PET‐R stiffness with organoclays loading and the system containing Cloisite 25A treated with [3‐(glycidyloxy)propyl]trimethoxysilane revealed combination of high stiffness and extensibility, which could be utilized for production of high‐performance materials by spinning, extrusion, and blow molding technologies. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Effect of silane grafting on the microstructure of high-density polyethylene/organically modified montmorillonite nanocomposites

Organically modified montmorillonite (org-MMT) and high-density polyethylene (HDPE) grafted with silane groups (HDPE-g-silane) were melt compounded to give HDPE-g-silane-blend-org-MMT nanocomposites. X-ray diffractometry was performed to investigate the intercalation effect. Transmission electron microscopy was applied to observe the dispersion of org-MMT layers in HDPE matrices. The results indicate that an intercalated structure can be easily obtained in HDPE-g-silane-blend-org-MMT nanocomposites. Furthermore, positron annihilation lifetime spectroscopy was used to characterize the microstructure of the composites. It is found that the ortho-positron (o-Ps) intensity for HDPE-g-silane is decreased by approximately 10% with a narrower lifetime distribution than that for HDPE. With increasing org-MMT concentration, the o-Ps intensity I3 increases for HDPE-g-silane-blend-org-MMT nanocomposites; however, for HDPE-blend-org-MMT composites I3 decreases. It is found that HDPE composites with good dispersion can be obtained following appropriate modification of the HDPE. And silane grafting has an effect on the free volume of the HDPE nanocomposites. Copyright © 2007 Society of Chemical Industry

Structure and properties of nanocomposites based on poly(butylene succinate) and organically modified montmorillonite

AbstractPoly(butylene succinate) and organically modified montmorillonite nanocomposites with there different compositions were prepared via melt blending in a twin‐screw extruder. The structure of the nanocomposites was studied with X‐ray diffraction and transmission electron microscopy, which revealed the formation of intercalated nanocomposites, regardless of the silicate loading. Dynamic mechanical analysis revealed a substantial increase in the storage modulus of the nanocomposites over the entire temperature range investigated. The tensile property measurements showed a relative increase in the stiffness with a simultaneous decrease in the yield strength in comparison with that of neat poly(butylene succinate). The oxygen gas barrier property of neat poly(butylene succinate) improved after nanocomposite preparation with organically modified montmorillonite. The effect of the layered‐silicate loading on the melt‐state linear viscoelastic behavior of the intercalated nanocomposites was also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 777–785, 2006

Yield behaviour of a melt‐compounded polyethylene–intercalated montmorillonite nanocomposite

AbstractThe yield behaviour of a series of melt‐mixed polyethylene–modified montmorillonite nanocomposites has been studied as a function of temperature and strain rate and compared to the behaviour of the base polymer. The processing conditions used gave an intercalated structure as assessed by X‐ray diffraction. Although there was a modest improvement in stiffness with clay content, the yield behaviour was insensitive to the addition of the clay. Both the base polymer and the nanocomposites showed double yield points. These were analysed as activated rate processes, with the activation energies consistent with the low strain yield point being associated with the α2 molecular relaxation and the higher strain yield point with ‘c’ axis slip. Copyright © 2003 Society of Chemical Industry

Multiple melting and crystallization of nylon‐66/montmorillonite nanocomposites

AbstractNylon‐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

Structure and Properties of Natural Rubber and Modified Montmorillonite Nanocomposites

Abstract Montmorillonite clay was organically modified by primary and quaternary ammonium salts (having C12-C18). The modified clay was added to a solution of natural rubber in toluene at various contents. Characterization of the structure of the nanocomposites was performed by using x-ray diffraction and transmission electron microscope. The results showed that the silicate layers of the clay were expanded so that the exfoliated nanocomposites were obtained at clay content below 10 phr; above that the nanocomposites became partially exfoliated. Moreover, long primary amine showed more improved mechanical properties than the quaternary one (at the same carbon numbers). The longer organic modifying agents resulted in better expansion of silicate layer distance indicating more intercalation of natural rubber molecules in between clay galleries. The curing properties were also improved. It was found that a small loading of 7 phr is enough to bring good mechanical properties in comparison to those of high structure silica filled and carbon black filled natural rubber vulcanizates.