Highly exfoliated PE/Na+MMT nanocomposite produced via in situ polymerization by a catalyst supported on a novel modified Na+MMT

A suitable Ziegler–Natta catalyst was prepared by supporting TiCl₄ on sodium montmorillonite (Na⁺MMT) modified by butyl octyl magnesium (BOM). This catalyst was applied for the polymerization of ethylene toward a polyethylene (PE)/Na⁺MMT nanocomposite. Catalyst behavior and nanocomposite properties were studied. It was found that catalyst activity was acceptably high. In addition, it had a smooth rate during ethylene polymerization. Transmission electron microscopy image and X-ray diffraction pattern evidenced an excellent exfoliation of the Na⁺MMT layers in the polymer matrix.     

Harmless hydrogels based on PVA/Na+‐MMT nanocomposites for biomedical applications: Fabrication and characterization

A series of nanocomposite hydrogels were prepared by a freeze‐thaw process, using polyvinyl alcohol (PVA) as polymer matrix and 0–10 wt% of hydrophilic natural Na‐montmorillonite (Na⁺‐MMT), free from any modification, as composite aggregates. The effect of nanoclay content and the sonication process on the nanocomposite microstructure and morphology as well as its properties (physical, mechanical, and thermal) were investigated. The microstructure and morphology were investigated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and X‐ray diffraction technique. The thermal stability and mechanical properties of nanocomposite hydrogels were examined using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis; moreover hardness and water vapor transmission rate measurements. It was concluded that the microstructure, morphology, physical (thermal) and mechanical properties of nanocomposite hydrogels have been modified followed by addition of nanoclay aggregates. The results showed that Na⁺‐MMT may act as a co‐crosslinker. Based on the results obtained, the nanocomposite hydrogel PVA/Na⁺‐MMT synthesized by a freeze‐thaw process, appeared to be a good candidate for biomedical applications. POLYM. COMPOS., 38:1135–1143, 2017. © 2015 Society of Plastics Engineers     

Chitosan/clay nanocomposite film preparation and characterization

Nanocomposites of chitosan and nanoclays (MMT‐Na⁺ and Cloisite 30B) were prepared by solvent casting. The structural properties, thermal behaviors, and mechanical properties were characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine. XRD and TEM results indicated that an exfoliated structure was formed with addition of small amounts of MMT‐Na⁺ to the chitosan matrix. Intercalation along with some exfoliation occurred with up to 5 wt % MMT‐Na⁺. Micro‐scale composite (tactoids) formed when Cloisite 30B was added to the chitosan matrix. Surface roughness increased with addition of a small amount of clay. Tensile strength of a chitosan film was enhanced and elongation‐at‐break decreased with addition of clay into the chitosan matrix. Melt behavior and thermal stability did not change significantly with addition of clays. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1684–1691, 2006     

Novel polyether polyurethane/clay nanocomposites synthesized with organicly modified montmorillonite as chain extenders

A kind of novel polyether polyurethane (PU)/clay nanocomposite was synthesized using poly(tetramethylene glycol), 4,4′‐diphenylmethane diisocyanate (MDI), 1,6‐hexamethylenediamine, and modified Na⁺‐montmorillonite (MMT). Here, organicly modified MMT (O‐MMT) was formed by applying 1,6‐hexamethylenediamine as a swelling agent to treat the Na⁺‐MMT. The X‐ray analysis showed that exfoliation occurred for the higher O‐MMT content (40 wt %) in the polymer matrix. The mechanical analysis indicated that, when the O‐MMT was used as a chain extender to replace a part of the 1,2‐diaminopropane to form PU/clay nanocomposites, the strength and strain at break of the polymer was enhanced when increasing the content of O‐MMT in the matrix. When the O‐MMT content reached about 5%, the tensile strength and elongation at break were over 2 times that of the pure PU. The thermal stability and the glass transition of the O‐MMT/PU nanocomposites also increased with increasing O‐MMT content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 6–13, 2006     

Ethylene propylene diene terpolymer/ethylene vinyl acetate/layered silicate ternary nanocomposite by solution method

A new ternary nanocomposite has been developed using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate (16 Me‐MMT) from sodium montmorillonite (Na⁺‐MMT). Wide angle X‐ray diffraction and transmission electron microscopic analysis confirmed the intercalation of the polymer chains in between the organosilicate layers and the nanoscale distribution of 16 Me‐MMT in polymer matrix, respectively. The measurement of mechanical properties for 2–8 wt% of 16 Me‐MMT loadings showed a significant increase in tensile strength, elongation at break, and modulus at different elongations. Such an improvement in mechanical properties has been correlated based on the fracture behavior of nanocomposite by SEM analysis. Thermal stability of EPDM/EVA/layered silicate ternary nanocomposites also showed substantial improvements compared with the neat EPDM/EVA blend, confirming thereby the formation of a high performance nanocomposite. POLYM. ENG. SCI., 46:437–843, 2006. © 2006 Society of Plastics Engineers     

Synthesis of Na+‐montmorillonite/amphiphilic polyurethane nanocomposite via bulk and coalescence emulsion polymerization

Polyurethane/clay nanocomposites have been synthesized using Na⁺‐montmorillonite (Na⁺‐MMT)/amphiphilic urethane precursor (APU) chains that have hydrophilic polyethylene oxide (PEO) chains and hydrophobic segments at the same molecules. Nanocomposites were synthesized through two different crosslinking polymerization methods. One is UV curing of melt mixed APU/Na⁺‐MMT mixtures; the other is coalescence polymerization of APU/Na⁺‐MMT emulsions. These two kinds of composites had intercalated silicate layers of Na⁺‐montmorillonite by insertion of PEO chains in APU chains, which was confirmed by X‐ray diffraction measurement and transmission electron microscopy. These composite films also showed improved mechanical properties compared to pristine APU films. Although the two kinds of nanocomposites exhibited the same degree of intercalation and were synthesized based on the same precursor chains, these nanocomposite films had the different mechanical properties. Nanocomposites synthesized using APU/Na⁺‐MMT emulsions, having microphase‐separated structure, had greater tensile strength than those prepared with melt‐mixed APU/Na⁺‐MMT mixtures. Location of intercalated Na⁺‐MMT by PEO chains at the oil–water interface also could be confirmed by rheological behavior of the APU/Na⁺‐MMT/water mixture. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3130–3136, 2003     

Preparation and characterization of transparent poly(methyl methacrylate)/Na+‐MMT nanocomposite films by solution casting

Films of poly(methyl methacrylate) (PMMA)/sodium montmorillonite (Na⁺‐MMT) nanocomposites have been successfully prepared utilizing Na⁺‐MMT by N,N‐dimethylformamide solution casting. The nanocomposite films show high transparency, enhanced thermal resistance, and mechanical properties in comparison with the neat polymer film. The transparency of the films was investigated by UV‐vis spectra. The exfoliated dispersion of Na⁺‐MMT platelets in nanocomposites were investigated by X‐ray diffraction and transmission electron microscopy. The enhanced thermal resistance and mechanical properties of PMMA were studied by thermal gravimetric analysis and dynamic mechanical analysis, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and antimicrobial activity of the Schiff base from polyoxyalkylene‐montmorillonite nanocomposites and aldehydes

Vanillin (4‐hydroxy‐3‐methoxy benzaldehyde) and 5‐formylamino salicylic acid microbicides were reacted with polyoxyalkylene‐montmorillonite (D_230–2000‐MMT) nanocomposites. The microstructure of these Schiff base nanocomposites was characterized by TEM and XRD. D_230–2000‐MMT nanocomposites were prepared by an ion exchange process of sodium montmorillonite (Na‐MMT) and NH₃ ⁺ groups in polyoxyalkylene amine hydrochloride with three different molecular masses of D₂₃₀, D₄₀₀, and D₂₀₀₀. Wide‐angle X‐ray diffraction confirms the intercalation of the polymer between the silicate layers. Electrostatic interaction between the positively charged NH₃ ⁺ groups and the negatively charged surface of MMT was observed. The nanocomposites were tested for antimicrobial activity against the Gram‐negative bacteria (Escherichia coli NCIM 2065), Gram‐positive bacteria (Bacillus subtillus ATCC), and fungi (Candida albicans SC5314 and Cryptococcus neoformans). The D₂₀₀₀‐MMT/vanillin Schiff base nanocomposite strongly inhibited the growth of all microorganisms that can be used in different applications. The amount of loaded polymer and the structure of the nanocomposite play an important role in inhibiting the bacterial and fungal strains. It is found that the Schiff base nanocomposite affect the morphology, oxygen consumption, and the release of cytoplasmic constituents such as potassium (K⁺), sodium (Na⁺), and calcium (Ca²⁺) ions leading to death of the cells. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Synthesis and evaluation of high‐performance ethylene–propylene–diene terpolymer/organoclay nanoscale composites

The main objective of this study was to synthesize and characterize the properties of ethylene–propylene–diene terpolymer (EPDM)/clay nanocomposites. Pristine clay, sodium montmorillonite (Na⁺–MMT), was intercalated with hexadecyl ammonium ion to form modified organoclay (16Me–MMT) and the effect of intercalation toward the change in interlayer spacing of the silicate layers was studied by X‐ray diffraction, which showed that the increase in interlayer spacing in Na⁺–MMT by 0.61 nm is attributed to the intercalation of hexadecyl ammonium ion within the clay layers. In the case of EPDM/16Me–MMT nanocomposites, the basal reflection peak was shifted toward a higher angle. However, gallery height remained more or less the same for different EPDM nanocomposites with organoclay content up to 8 wt %. The nanostructure of EPDM/clay composites was characterized by transmission electron microscopy, which established the coexistence of intercalated and exfoliated clay layers with an average layer thickness in the nanometer range within the EPDM matrix. The significant improvement in thermal stability and mechanical properties reflects the high‐performance nanocomposite formation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2429–2436, 2004     

Soy protein isolate nanocomposite film enriched with eugenol,an antimicrobial agent: Interactions and properties

Nanocomposites films were designed from soy protein isolates (SPI), clays (Na⁺‐MMT), and eugenol an antimicrobial agent. Interactions between Na⁺‐MMT and eugenol were evidenced by a shift of the d‐spacing by X‐ray diffraction analysis. The addition of Na⁺‐MMT (5 and 7.5% w/w) in SPI solution increased its shear thinning behavior and its consistency. Accordingly, a good exfoliation of clays in SPI films was observed. The glass transition temperature of SPI films was impacted by the clays addition but not the water vapor permeability. In contrast, the addition of eugenol in SPI solution did not affected the consistency but induced a decrease of the SPI film T_g and an increase of the water vapor permeability. The presence of eugenol counterbalanced the effect of clays on consistency of film‐forming solution. The clay intercalation process was facilitated and the water vapor permeability and active agent release were modified. The presence of clay did not affect the antibacterial effect of eugenol/SPI films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45941.     

Poly(vinyl alcohol) nanocomposites with different clays: Pristine clays and organoclays

Poly(vinyl alcohol) (PVA)/clay nanocomposites were synthesized using the solution intercalation method. Na ion‐exchanged clays [Na⁺–saponite (SPT) and Na⁺–montmorillonite (MMT)] and alkyl ammonium ion‐exchanged clays (C₁₂–MMT and C₁₂OOH–MMT) were used for the PVA nanocomposites. From the morphological studies, the Na ion‐exchanged clay is more easily dispersed in a PVA matrix than is the alkyl ammonium ion‐exchanged clay. Attempts were also made to improve both the thermal stabilities and the tensile properties of PVA/clay nanocomposite films, and it was found that the addition of only a small amount of clay was sufficient for that purpose. Both the ultimate tensile strength and the initial modulus for the nanocomposites increased gradually with clay loading up to 8 wt %. In C₁₂OOH–MMT, the maximum enhancement of the ultimate tensile strength and the initial modulus for the nanocomposites was observed for blends containing 6 wt % organoclay. Na ion‐exchanged clays have higher tensile strengths than those of organic alkyl‐exchanged clays in PVA nanocomposites films. On the other hand, organic alkyl‐exchanged clays have initial moduli that are better than those of Na ion‐exchanged clays. Overall, the content of clay particles in the polymer matrix affect both the thermal stability and the tensile properties of the polymer/clay nanocomposites. However, a change in thermal stability with clay was not significant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3208–3214, 2003     

Properties of water‐soluble acrylic copolymer/montmorillonite nanocomposites for warp sizing

Acrylic copolymer/montmorillonite (MMT) nanocomposites for warp sizing were prepared in the presence of Na⁺‐MMT by the in situ intercalative polymerization of acrylic acid, acrylamide, and methyl acrylate in water solution. The properties of the solution and cast film were tested according to an application in sizing process of the nanocomposite size with various MMT contents. The results indicate that, for an exfoliated structure corresponding to the MMT content increasing to 7 wt %, the performance parameters of solution viscosity, glass‐transition temperature, and tensile strength of the film increased and the moisture sorption, abrasion loss, and elongation at break of the film decreased. When the intercalated structure of MMT was 9 wt %, the gathered MMT layers acted as a common inorganic filler in the copolymer matrix, with limited contribution to the properties of the composite. The adhesion work of the nanocomposite solution was calculated by use of the Young–Dupre relation, which showed maximum values at an MMT content of 3 wt % on the surfaces of both the polyester and cellulose films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A novel method to prepare chitosan/montmorillonite nanocomposites

We are proposing a novel method to prepare chitosan/montmorillonite nanocomposites. The montmorillonite (MMT) clay was excavated from the mountainside of eastern Taiwan. After being purified, it was incorporated with potassium persulfate (KPS) through the intercalation process. As the KPS‐incorporated MMT was dispersed in the acidified aqueous solution of chitosan, the KPS instantly reacted with the chitosan, resulting in the cleavage of polymer chains and exfoliation of MMT as well. After removing the unexfoliated MMT, solutions were cast to form a film of chitosan/MMT nanocomposite. Interestingly, the exfoliated MMT layers were found to flatten out in parallel with the surface, which not only increased the tensile strength of the chitosan film but also hindered degradation in the vitro test. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2042–2047, 2005     

Electrical conductivity behavior of epoxy matrix nanocomposites with simultaneous dispersion of carbon nanotubes and clays

In this work, nanocomposites with simultaneous dispersion of multiwalled carbon nanotubes (MWCNT) and montmorillonite clays in an epoxy matrix were prepared by in situ polymerization. A high energy sonication was employed as the dispersion method, without the aid of solvents in the process. The simultaneous dispersion of clays with carbon nanotubes (CNT) in different polymeric matrices has shown a synergic potential of increasing mechanical properties and electrical conductivity. Two different montmorillonite clays were used: a natural (MMT‐Na⁺) and an organoclay (MMT‐30B). The nanocomposites had their electrical conductivity (σ) and dielectric constant (ε_r) measured by impedance spectroscopy. The sharp increase in electrical conductivity was found between 0.10 and 0.25 wt% of the MWCNTs. Transmission electron microscopy (TEM) of the samples showed a lower tendency of MWCNT segregation on the MMT‐30B clay surface, which is connected to intercalation/exfoliation in the matrix, that generates less free volume available for MWCNTs in the epoxy matrix. Data from electrical measurement showed that simultaneously adding organoclay reduces the electrical conduction in the nanocomposite. Moreover, conductivity and permittivity dispersion in low frequency suggest agglomeration of nanotubes surrounding the natural clay (MMT‐Na⁺) particles, which is confirmed by TEM. POLYM. COMPOS., 37:1603–1611, 2016. © 2014 Society of Plastics Engineers     

Colorless polyimide nanocomposite films with pristine clay: Thermal behavior,mechanical property,morphology, and optical transparency

Polyimide (PI)/clay hybrids were synthesized using the in situ solution intercalation method via poly(amic acid). The Na ion‐exchanged clays Na⁺‐saponite (SPT), Na⁺‐mica (Mica), and Na⁺‐montmorillonite (MMT) were used for the intercalation of PI polymer chains. Our dispersion results show that pristine SPT is more easily dispersed in a PI matrix than MMT or Mica. PI nanocomposites were prepared with various SPT contents to examine the variations with SPT content in the range 0–1 wt% of the thermomechanical properties, morphology, and optical transparency of the nanocomposites. The PI films have excellent optical transparencies, and are almost colorless. However, the optical transparency of the PI hybrid films decreases slightly with increases in the clay content. We also examined the relationship between the properties and clay content of the PI hybrid films using wide‐angle X‐ray diffraction (XRD) measurements, electronic microscopy (SEM and TEM), and universal tensile machine (UTM). The color intensities of the PI films were evaluated with a spectrophotometer. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Synthesis and characterization of partially hydrolyzed polyacrylamide nanocomposite weak gels with high molecular weights

High‐molecular‐weight partially hydrolyzed polyacrylamide nanocomposite (HPAMNC) weak gels were synthesized and evaluated for their flooding behaviors in oil‐recovery applications. The structure, morphology, and properties of the obtained HPAMNC samples and their weak gels were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). XRD patterns clearly proved the exfoliation of the montmorillonite (MMT) layers in the polymer matrix; this was consistent with TEM analysis. The morphology of the HPAMNC was proven to be in a cross‐wire aggregated form by SEM analysis. The viscosity‐average molecular mass of the obtained HPAMNC was approximately 8.51 × 10⁶ under the optimized MMT load at 1.0 wt %. The flooding experiments showed that the oil‐recovery rates in sand pack tubes with low and high permeability were enhanced by approximately 35.1 and 46.2%, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42626.     

Preparation and characterization of thermoplastic starch–kaolinite nanocomposite films

In this work, the thermoplastic starch–kaolinite (KAO) nanocomposite films were first prepared via solution‐casting method using chitosan‐modified KAO (CKAO) and Na⁺–KAO (NKAO). The structure was investigated by X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy techniques. The results showed that the well‐dispersed KAO layers were delaminated in the starch matrix attesting to anexfoliated nanocomposite and formed strong interaction with starch molecules. According to thermogravimetric analysis, differential scanning calorimetric study, and water absorption testing, the starch–CKAO–urea nanocomposites have the greatest enhancements compared with those of starch–urea film and starch–NKAO–urea nanocomposites. These results provide the important information with using CKAO to obtain the exfoliated starch nanocomposites with high performance. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Synergism Effect of Montmorillonite and Cellulose Whiskers on the Mechanical and Barrier Properties of Natural Rubber Composites

A series of nanocomposite films based on natural rubber (NR), Na⁺‐montmorillonite (MMT), and cellulose whiskers (W) was prepared, keeping a total filler content equal to 5 wt.‐%. In the binary NR/MMT system, small stacks of intercalated montmorillonites were homogeneously dispersed within the polymer matrix whereas they were clearly lying in the vicinity of cellulose whiskers in the ternary NR/MMT/W blends. The effects of MMT and W on mechanical and gas barrier properties of the nanocomposite films were investigated. A significant increase of the rubbery modulus was obtained upon filler addition. The reinforcing effect was particularly important for the nanocomposite film reinforced with 1 wt.‐% MMT and 4 wt.‐% W. The improvement of the gas barrier properties observed upon filler addition was explained by a tortuosity effect. The calculated tortuosity values indicated that the simultaneous use of MMT and W could greatly slow down the gas diffusion rate in NR. Formation of MMT‐W subassembly should be responsible for this synergism effect.

     

Effect of polymer matrix/montmorillonite compatibility on morphology and melt rheology of polypropylene nanocomposites

In this study, Ca²⁺‐montmorillonite (Ca²⁺‐MMT) and organo‐montmorillonite (OMMT) were modified by three compatibilizers with different degrees of polarity [poly(ethylene glycol) (PEG), alkyl‐PEG, and polypropylene (PP)‐g‐PEG]. PP/MMT nanocomposites were prepared by melt blending and characterized using X‐ray diffraction and transmission electron microscopy. The results showed the degree of dispersion of OMMT in the PP/PP‐g‐PEG/OMMT (PMOM) nanocomposite was considerably higher than those in the PP/PEG/OMMT and PP/alkyl‐PEG/OMMT nanocomposites, which indicated that the dispersion was relative to the compatibility between modified OMMT and PP matrix. Linear viscoelasticity of PP/MMT nanocomposites in melt states was investigated by small amplitude dynamic rheology measurements. With the addition of the modified MMT, the shear viscosities and storage modulus of all the PP/MMT nanocomposites decreased. It can be attributed to the plasticization effect of PEG segments in the three modifiers. This rheological behavior was different from most surfactant modified MMT nanocomposites which typically showed an increase in dynamic modulus and viscosity relative to the polymer matrix. The unusual rheological observations were explained in terms of the compatibility between the polymer matrix and MMT. In addition, the mechanical properties of PP/MMT nanocomposites were improved. A simultaneous increase in the tensile strength and toughness was observed in PP/PMOM nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Development of nanocomposites based on organically modified montmorillonite and plasticized PVC with improved barrier properties

Montmorillonite (MMT) was organically modified with tributyl citrate (TBC). Organoclays (OMMTs) were processed with diisononyl phthalate (DINP)‐plasticized polyvinyl chloride (PVC) to form polymer nanocomposites. The produced composite materials showed a contradictory change in properties to that expected of a layered silicate nanocomposite, with a decreased E‐modulus and increased gas permeability compared with a material without OMMT. It was experimentally shown that the TBC modifier was extracted from the OMMT and was dispersed in the PVC/DINP matrix, whereupon the OMMT collapsed and formed micrometer‐sized agglomerates. Further investigation revealed that TBC has a significant effect on the gas permeability and the E‐modulus, even at low additions to a DINP‐plasticized PVC. A PVC nanocomposite with the TBC acting as both the OM for MMT and as the primary plasticizer was produced. This material showed a significantly increased E‐modulus as well as a decrease in gas permeability, confirming that it is possible to develop a nanocomposite based on plasticized PVC, if both the organo‐modification of the MMT and the formulation of the matrix are carefully selected. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42876.