Fabrication and characterization of new semiconducting nanomaterials composed of natural layered silicates (Na-MMT), natural rubber (NR), and polypyrrole (PPy)

An electrolytic admicellar polymerization was chosen for synthesizing new semiconducting nanomaterials composed of sodium montmorillonite (Na⁺-MMT), polypyrrole (PPy), and natural rubber (NR). The contents of the pyrrole monomer and the Na⁺-MMT were varied from 100 to 800 mM and 1-7 parts per hundred of rubber (phr), respectively. Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) were used to confirm the success of the synthesis. The morphological studies carried out by X-ray diffraction (XRD) and TEM pointed out the different states of dispersion of the layered silicates, whereas the study done by scanning electron microscopy (SEM) showed a great dependence of the nanocomposite morphology on the inclusion of the layered silicates. Thermal stability studies demonstrated the thermo-protecting and thermo-oxidative behaviors imparted by the layered silicates. The mechanical and DC electrical conductivity properties were significantly improved with the inclusion of the layered silicates, especially at a 7 phr loading.     

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 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     

Effect of organoclay on the properties of maleic‐anhydride grafted polypropylene and poly(methyl methacrylate) blend

Poly(methyl methacrylate)/polypropylene (PMMA/PP) and PMMA/maleic‐anhydride grafted PP (MAPP) blends and their blend nanocomposites containing 2 wt% organoclay (Cloisite 15A, denoted C15A), prepared by a melt mixer were studied. Both X‐ray diffraction (XRD) and transmission electron microscopy (TEM) revealed exfoliated polymer blend nanocomposites. Scanning electron microscopy (SEM) studies indicated a droplet dispersion morphology for all the blends while addition of C15A into PMMA/MAPP blend resulted to a co‐continuous morphology. In fact, rheological data and thermal properties indicated that the PMMA/MAPP/C15A nanocomposite showed a better homogeneous dispersion of silicate layers than PMMA/PP/C15A nanocomposite. A Cole–Cole plot and relaxation modulus indicated a solid‐like character for PMMA/MAPP and PMMA/MAPP/C15A, while a liquid‐like behavior was noticed for PMMA/PP and PMMA/PP/C15A. The effect of an organoclay on the dynamic mechanical properties of samples was investigated using dynamic mechanical analysis (DMA) which showed a significant enhancement on the storage modulus of the PMMA/MAPP/C15A as compared to PMMA/PP/C15A . POLYM. COMPOS., 38:431–440, 2017. © 2015 Society of Plastics Engineers     

Physical properties of polyester-acrylate/clay nanocomposite films with different organoclays

Three different organoclays (VDA-MMT, SDA-MMT, and 20A-MMT) originated from the same pristine clay (Na⁺-MMT) were used to prepare polyester-acrylate/clay nanocomposite films by in-situ ultraviolet (UV)-polymerization. Except for the commercial organoclay (20A-MMT), VDA-MMT and SDA-MMT were synthesized in this study by ion exchange method. The effects of different organoclays on the thermal stability, mechanical, and optical properties of the nanocomposite films were investigated. The physical properties of the nanocomposites were considerably different from each other because of the different characteristics of the organoclays. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Synthesis and antifungal activities of polymer/montmorillonite–terbinafine hydrochloride nanocomposite films

The poly(dimethylsiloxane) (PDMS)/montmorillonite–terbinafine hydrochloride (PDMS/OMMT) nanocomposite films were obtained by solution intercalation. Organo-montmorillonite (OMMT) with antifungal activity was prepared from Na⁺-montmorillonite (Na⁺-MMT) and terbinafine hydrochloride (Ter-HCl) by ion exchange. The microstructure of these nanocomposite films were characterized by TEM and XRD. The effect of OMMT on the mechanical properties and thermal stability of the nanocomposites was investigated. When the OMMT content was < 1 mass %, the nanocomposites showed excellent mechanical properties. The polymers were tested for antifungal activity against Candida albicans. The PDMS/OMMT nanocomposite films strongly inhibited the C. albicans.     

Synthesis and antimicrobial activities of polymer/montmorillonite–chlorhexidine acetate nanocomposite films

The PDMS/montmorillonite–chlorhexidine acetate (PDMS/OMMT) nanocomposite films were successfully obtained by intercalation from solution. Organo-montmorillonite (OMMT) with antibacterial activity was prepared from Na⁺-montmorillonite (Na⁺-MMT) and chlorhexidine acetate (CA) by ion exchange. The microstructure of these nanocomposite films were characterized by TEM and XRD. The effect of OMMT on mechanical properties and thermal stability of the nanocomposites was investigated. When the OMMT content was lower than 0.5 mass %, the nanocomposites showed excellent mechanical properties. The polymers were tested for antimicrobial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The PDMS/OMMT nanocomposite films strongly inhibited the growth of a wide variety of microorganisms, including Gram-positive bacteria, Gram-negative bacteria.     

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     

Styrene butadiene rubber/clay nanocomposites for tire tread application

Homogeneous and stable dispersion of layered silicates in their rubber nanocomposite is a matter of interest as it can significantly affect the material properties. Herein we propose a facile and easily industrialised approach for preparing highly dispersed montmorillonite (MMT)/rubber nanocomposites by the latex compounding method. Furthermore, an efficient way of enhancing the interlayer spaces of organically modified MMT (f-MMT) with alkyl-ammonium chains while mixing the styrene butadiene rubber (SBR) is reported. The f-MMT embedded SBR matrix shows a remarkable improvement of the modulus and tensile strength even in the low loading rate, which is ascribed to the well dispersion of the f-MMT enhancing interfacial interaction with the rubber matrix. Furthermore, we manufactured the practical pneumatic tire using f-MMT/SBR nanocomposite with outstanding wear resistance, grip performance and low-rolling resistance for the green tire application, opening up enormous opportunities to prepare high-performance rubber composites for future engineering applications.     

Rigid PVC/(layered silicate) nanocomposites produced through a novel melt‐blending approach

On the basis of the fusion behavior of poly(vinyl chloride) (PVC), the influence of compounding route on the properties of PVC/(layered silicate) nanocomposites was studied. Four different compounding addition sequences were examined during the melt compounding of PVC with montmorillonite (MMT) clay, including (a) a direct dry mixing of PVC and nanoclay, (b) an addition of nanoclay at compaction, (c) an addition of nanoclay at the onset of fusion, and (d) an addition of nanoclay at equilibrium torque. Both unmodified sodium montmorillonite (Na⁺‐MMT) and organically modified montmorillonite (Org.‐MMT) clays were used, and the effect of the addition sequence of the clay during compounding on its dispersion in the matrix was evaluated by X‐ray diffraction and transmission electron miscroscopy. The surface color change, dynamic mechanical analysis, and flexural and tensile properties of PVC/clay nanocomposites were also studied. The experimental results indicated that both the extent of property improvement and the dispersion of nanoparticles in PVC/(layered silicate) nanocomposites are strongly influenced by the degree of gelation achieved in PVC compounds during processing. The addition of nanoclay to PVC must be accomplished at the onset of fusion, when PVC particles are reduced in size, in order to produce nanocomposites with better nanodispersion and enhanced mechanical properties. Overall, rigid PVC nanocomposites with unmodified clay (Na⁺‐MMT) were more thermally stable and exhibited better mechanical properties than their counterparts with organically modified clay (Org.‐MMT). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

A Model for Molecular Weight Prediction in Acrylonitrile Polymerization

Poly ethylene terephthalate (PET)-based nanocomposites containing three differently modified clays were prepared by melt compounding. The influence of type of modified clay on surface properties of the resultant nanocomposite was investigated by various analytic techniques, namely, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurement (CAM), scanning electron microscopy (SEM) and reflectance spectroscopy (RS). Any possible interaction between each nanoclay and PET at the surface was elucidated by Fourier transform infrared spectroscopy. Atomic force microscopy studies of the resultant nanocomposites showed increased in surface roughness compared to pure PET. Contact angle measurements on the resultant PET composites demonstrated that the wettability of such composites depends on hydrophilicity of the nanoclay particles. Scanning electron microscopy images illustrated poor interfacial interaction between PET and Na⁺ clay particles causing fracture type non-uniformity of PET/Na⁺ clay nanocomposite.     

Preparation and characterization of polypropylene/layered silicate nanocomposites using an antioxidant

Polypropylene (PP)/layered silicate nanocomposites were prepared via simple melt mixing of three components, PP, layered silicates modified with octadecylamine (C18-MMT) and antioxidant, to investigate the role of antioxidant. TEM and X-ray scattering results confirmed the intercalated state of silicates in PP/layered silicate nanocomposites with antioxidant. In rheological and mechanical study, the nanocomposites with antioxidant showed higher properties than those of the unfilled PP. The nanocomposite with 5 wt% C18-MMT and 0.5 phr antioxidant exhibited about 1.4 times higher tensile modulus and 1.3 times higher storage modulus than the unfilled PP. However, PP/C18-MMT without antioxidant showed lower rheological values owing to the thermal decomposition of PP and the poor compatibility between PP and C18-MMT. It could be concluded that antioxidants played an important role in enhancing the compatibility between PP and C18-MMT. According to the real time X-ray diffraction, the nanocomposite showed the weak ordering of PP crystals than the unfilled PP in the load-extension plateau region of elongation.     

Structure and conductive properties of poly(ethylene oxide)/layered double hydroxide nanocomposite polymer electrolytes

The oligo(ethylene oxide) modified layered double hydroxide (LDH) prepared by template method was added as a nanoscale nucleating agent into poly(ethylene oxide) (PEO) to form PEO/OLDH nanocomposite electrolytes. The effects of OLDH addition on morphology and conductivities of nanocomposite electrolytes were studied using wide-angle X-ray diffractometer, polarized optical microscopy, differential scanning calorimetry and ionic conductivity measurement. The results show that the exfoliated morphology of nanocomposites is formed due to the surface modification of LDH layers with PEO matrix compatible oligo(ethylene oxide)s. The nanoscale dispersed OLDH layers inhibit the crystal growth of PEO crystallites and result in a plenty amount of intercrystalline grain boundary within PEO/OLDH nanocomposites. The ionic conductivities of nanocomposite electrolytes are enhanced by three orders of magnitude compared to the pure PEO polymer electrolytes at ambient temperature. It can be attributed to the ease transport of Li⁺ along intercrystalline amorphous phase. This novel nanocomposite electrolytes system with high conductivities will be benefited to fabricate the thin-film type of Li-polymer secondary battery.     

Effect of clay modifier and matrix molar mass on the structure and properties of poly(ethylene oxide)/Cloisite nanocomposites via melt-compounding

The present study is concerned with the preparation and characterisation of PEO/clay nanocomposites via melt-extrusion. Two different matrix molar masses of PEO were investigated as well as various types of the Cloisite clay range. PEO/Cloisite Na⁺ nanocomposites give rise to intercalated structures displaying only a moderate improvement of the mechanical properties at higher clay concentrations, regardless of the matrix molar mass. The chemical nature of the organic modifier was proven to be detrimental for the final nanocomposite structure and resulting mechanical properties. PEO nanocomposites based on the Cloisite 30B clay, incorporating a polar modifier, give rise to exfoliated structures. They display a strongly increased storage modulus, regardless of the matrix molar mass. The structural organisation of the nanocomposites based on Cloisite 20A, containing an apolar modifier, is very dependent on the matrix molar mass. An exfoliated structure can only be achieved upon melt mixing with a high molar mass PEO. In general, the mechanical properties of the nanocomposites based on the high molar mass PEO matrix are slightly superior. The thermal properties are also distinctly influenced by the addition of clay, although the actual structural organisation of the nanocomposite is proven to be less important. The melt temperature, as well as the crystallinity, decreases upon the addition of clay, especially for the low molar mass PEO matrix. The decomposition temperature shows a slight increase upon the addition of clay, especially for the Cloisite 30B nanocomposites.     

Improving the physical properties of PEA/PMMA blends by the uniform dispersion of clay platelets

Poly(ethyl acrylate) (PEA)/poly(methyl methacrylate) (PMMA) emulsion blends that were combined with unmodified montmorillionite (MMT) to improve the physical properties via nanocomposite formation. We prepared a cationic PEA/PMMA latex and used a heterocoagulation process to create a homogeneous dispersion of the clay platelets in the matrix. The cationic PEA/PMMA emulsion blends were prepared using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous slurry of MMT. The PEA/PMMA-MMT nanocomposites could be processed at low temperatures. Low temperature processing prevented the commonly observed discoloration associated with many thermoplastic nanocomposites. DSC, SAXS, TEM and AFM were used to study the dispersion of MMT and morphology of PEA/PMMA-MMT nanocomposites. Tensile stress, elongation at break and Young's modulus demonstrated a significant reinforcing effect of clay.     

Crystallinity,ion conductivity,and thermal and mechanical properties of poly(ethylene oxide)–illite nanocomposites with exfoliated illite as a filler

Illite particles were exfoliated by the intercalation and subsequent deintercalation of dimethyl sulfoxide (DMSO) in the interlayer of illite, and the exfoliated illite particles were used to prepare a novel poly(ethylene oxide) (PEO)–illite nanocomposite. The resulting exfoliated illite and PEO–illite nanocomposites were characterized by X‐ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry, ion conductivity testing, thermogravimetry analysis, and mechanical testing. The XRD results showed that the acid treatment of illite to exchange K⁺ in the interlayer of illite with H⁺ was a necessary condition for the DMSO intercalation. SEM micrographs confirmed the exfoliation of the illite particles in the process of DMSO deintercalation from the interlayer of the illite–DMSO intercalation complex. A good dispersion of exfoliated illite in the PEO matrix was also confirmed. A gradual decrease in the PEO crystallinity in the PEO–illite nanocomposites was observed with increasing exfoliated illite concentration. The ion conductivity of the nanocomposites gradually increased with the filler content and reached 3.21 × 10⁻⁵ S/cm at an illite concentration of 20 wt %. The formation of an amorphous region around the exfoliated illite was beneficial for Li⁺‐ion conduction. The ion conductivity significantly increased when the amorphous regions were connected to each other to form a conducting path for Li⁺ ions with a high filler concentration of greater than 10 wt %. Meanwhile, the thermooxidative stability and mechanical properties of the PEO–illite nanocomposites were also enhanced when exfoliated illite was introduced into the polymer matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44226.     

Effects of amorphous silica nanoparticles and polymer blend compositions on the structural,thermal and dielectric properties of PEO–PMMA blend based polymer nanocomposites

The polymer nanocomposite (PNC) films consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrices dispersed with nanoparticles of amorphous silica (SiO₂) have been prepared by solution-cast method followed by melt-press technique. Effects of SiO₂ concentration (x?=?0, 1, 3 and 5 wt%) and PEO–PMMA blend compositional ratios (PEO:PMMA?=?75:25, 50:50, and 25:75 wt%) on the surface morphology, crystalline phase, polymer-polymer and polymer-nanoparticle interactions, melting phase transition temperature, dielectric permittivity, electrical conductivity, electric modulus and the impedance properties of the PNC films have been investigated. The crystalline phase of the PNC films decreases with the increase of PMMA contents which also vary anomalously with the increase of SiO₂ concentration in the films. The melting phase transition temperature and polymer-nanoparticle interactions significantly change with the variation in the compositional ratio of the blend polymers in the PNC films. It is observed that the effect of SiO₂ on the dielectric and electrical properties of these PNCs vary greatly with change in the compositional ratio of PEO and PMMA in the blends. The dielectric relaxation process of these films confirm that the polymers cooperative chain segmental dynamics becomes significantly slow when merely 1 wt% SiO₂ nanoparticles are dispersed in the polymer blend matrix.     

Nanocomposites based on layered silicate and miscible PVDF/PMMA blends: melt preparation, nanophase morphology and rheological behaviour

Polyvinylidene fluoride (PVDF)–organoclay nanocomposites were prepared by melt-extrusion using polymethylmethacrylate (PMMA) as an interfacial agent. These nanocomposite materials were analysed with respect to their morphological and rheological properties. The nanophase morphology development and nanophase dispersion were studied using TEM. A fine dispersion of partially to nearly fully exfoliated silicate layers in miscible PVDF/PMMA blend matrices was observed when organophilic montmorillonite was used. Increasing the amount of PMMA in the PVDF/PMMA blend leads to high degree of exfoliation.

The rheological behaviour of intercalated/exfoliated PVDF/PMMA nanocomposites containing various concentrations of organophilic silicate was also investigated. At low frequencies, the storage modulus is increasing with increasing PMMA content and the frequency dependence of the storage modulus gradually changes from liquid-like to solid-like for nanocomposites when 10 wt% of PMMA is added, indicating formation of a network structure.

Dynamic mechanical investigations show a dramatic increase of the storage modulus in the rubbery plateau compared to conventional mineral fillers, as a result of the network structure. Due to the ‘nano’-sized dispersion, property efficiency is already realized at low loading levels (3–5 wt%).     

Use of a new natural clay to produce poly(methyl methacrylate)‐based nanocomposites

Nanocomposites of poly(methyl methacrylate) (PMMA) filled with 3 wt% of modified natural Algerian clay (AC; montmorillonite type) were prepared by either in situ polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile or a melt‐mixing process with preformed PMMA via twin‐screw extrusion. The organo‐modification of the AC montmorillonite was achieved by ion exchange of Na⁺ with octadecyldimethylhydroxyethylammonium bromide. Up to now, this AC montmorillonite has found applications only in the petroleum industry as a rheological additive for drilling muds and in water purification processes; its use as reinforcement in polymer matrices has not been reported yet. The modified clay was characterized using X‐ray diffraction (XRD), which showed an important shift of the interlayer spacing after organo‐modification. The degree of dispersion of the clay in the polymer matrix and the resulting morphology of nanocomposites were evaluated using XRD and transmission electron microscopy. The resulting intercalated PMMA nanocomposites were analysed using thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the nanocomposites was not significantly influenced by the presence of the modified clay while the thermal stability was considerably improved compared to unfilled PMMA. This Algerian natural montmorillonite can serve as reinforcing nanofiller for polymer matrices and is of real interest for the fabrication of nanocomposite materials with improved properties. Copyright © 2009 Society of Chemical Industry     

Synthesis,Characterization, and Microbial Activity of Nanocomposites of Chitosan-Graft-Poly(4-vinyl pyridine) Copolymer/Organophilic Montmorillonite

Organophilic montmorillonite was synthesized by cationic exchange between Na⁺-MMT and N-octyl-N-vinyl-2-pyrrolidonium bromide. Nanocomposites of chitosan grafted with 4-vinyl pyridine and organophilic montmorillonite were prepared in acetic acid using ammonium persulfate as initiator. The molecular structure of the grafted copolymer was confirmed by FTIR. The degree of dispersion and the intercalation spacing of these nanocomposites were investigated using X-ray diffraction. The enhanced thermal stability of nanocomposites was verified by differential scanning calorimetry and thermogravimetric analysis. Preliminary results of the antibacterial and antifungal activities of the prepared nanocomposites have demonstrated significant antimicrobial activity of the nanocomposites compared with pure and grafted chitosan.