Structure and properties of nitrile rubber (NBR)–clay nanocomposites by co‐coagulating NBR latex and clay aqueous suspension

Nitrile rubber (NBR)–clay nanocomposites were prepared by co‐coagulating the NBR latex and clay aqueous suspension. Transmission electron microscopy showed that the silicate layers of clay were dispersed in the NBR matrix at the nano level and had a planar orientation. X‐ray diffraction indicated that there were some nonexfoliated silicate layers in the NBR–clay nanocomposites. Stress–strain curves showed that the silicate layers generated evident reinforcement, modulus, and tensile strength of the NBR–clay nanocomposites, which were significantly improved with an increase in the amount of clay, and strain‐at‐break was higher than that of the gum NBR vulcanizate when the amount of clay was more than 5 phr. The NBR–clay nanocomposites exhibited an excellent gas barrier property; the reduction in gas permeability in the NBR–clay nanocomposites can be described by Nielsen's model. Compared with gum NBR vulcanizate, the oxygen index of the NBR–clay nanocomposites increased slightly. The feasibility of controlling rubber flammability via the nanocomposite approach needs to be evaluated further. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3855–3858, 2003     

Mechanical properties and structures of dicyanate–clay nanocomposites

Dicyanate–clay nanocomposites comprising a dicyanate resin and a type of organically modified clay were prepared and characterized, and their thermomechanical properties were investigated. The organically modified clay had silicate layers of nanometer size intercalated with an organic modifier, which improved the compatibility between the clay and organic materials, such as dicyanate resins. Dynamic mechanical analysis was performed to investigate the thermomechanical properties of the dicyanate–clay nanocomposites containing various amounts of the clay. The storage modulus of the nanocomposites below their glass‐transition temperatures slightly increased with increasing clay content. The glass‐transition temperature of the dicyanate–clay nanocomposites increased with increasing clay content. The nanostructures of the dicyanate–clay nanocomposites were characterized by transmission electron microscopy and X‐ray diffraction analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2629–2633, 2003     

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     

Effect of solution concentration on the properties of nanocomposites

Though a large number of nanocomposites prepared by solution process has been reported in the literature, effect of solution concentration on properties of the nanocomposites has not been studied. In the present work, new fluorocarbon–clay nanocomposites were prepared by a solution mixing process. Characterization of the nanocomposites was done with X‐ray diffraction technique and atomic force microscopy. Effects of different rubber‐solution concentrations (5, 10, 15, 20, and 25 wt %) on the mechanical and dynamic mechanical properties of the resultant nanocomposites were investigated. Optimum properties were achieved at 20 wt % solution. The data could be explained with the help of structure of the nanocomposites and dispersion of the clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2407–2411, 2006     

Morphology and properties of PVC/clay nanocomposites via in situ emulsion polymerization

PVC/Na⁺–montmorillonite (MMT) nanocomposites were prepared via a simple technique of emulsion polymerization at several different MMT clay concentrations. X‐ray diffraction and transmission electron microscopy studies revealed the formation of a mixture of intercalated and exfoliated nanostructure. Tensile testing results showed that the tensile modulus of the nanocomposites increased with the addition of clay, while the tensile strength decreased little. The notched impact strength of the nanocomposites was also improved. For systems containing clay in the range of 2.1 to 3.5 wt %, the impact strength was almost two times as large as that of pure PVC. However, those mechanical properties began to decrease with the continuously increasing amount of clay. The fracture surface of pure PVC and the nanocomposites was observed by scanning electron microscope. Thermal properties of the nanocomposites were found to increase as a result of clay incorporation. The glass transition temperatures of the PVC/clay nanocomposites were nearly identical to that of pure PVC. The Vicat softening points exhibited a progressively increasing trend with the clay content added. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 277–286, 2004     

Use of acrylic based surfmers for the preparation of exfoliated polystyrene–clay nanocomposites

Two polymerizable cationic surfactants, (11-acryloyloxyundecyl)dimethyl(2-hydroxyethyl)ammonium bromide (hydroxyethyl surfmer) and (11-acryloyloxyundecyl)dimethylethylammonium bromide (ethyl surfmer), were used for the modification of montmorillonite (MMT) clay. The modification of MMT dispersions was carried out by ion exchange of the sodium ions in Na⁺-MMT by surfactants in aqueous media. Modified MMT clays were then dispersed in styrene and subsequently polymerized in bulk by a free-radical polymerization reaction to yield polystyrene–clay nanocomposites. An exfoliated structure was obtained using the ethyl surfmer-modified clay, whereas a mixed exfoliated/intercalated structure was obtained using the hydroxyethyl surfmer-modified clay. Nanocomposite structures were confirmed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The nanocomposites exhibited enhanced thermal stability and an increase in glass transition temperature, relative to neat polystyrene. The nanocomposites also exhibited enhanced mechanical properties, which were dependent on the clay loading. Intercalated polystyrene–clay nanocomposites were obtained using the non-polymerizable surfactant-modified clay (cetyltrimethylammonium bromide). Nanocomposites made from mixtures of surfmer-modified and CTAB-modified clays were also prepared, showing intermediate properties. However, when the nanocomposites were prepared in solution only intercalated morphologies were obtained. This was attributed to the competition between the solvent molecules and monomer in penetrating into clay galleries. These nanocomposites also exhibited enhanced thermal stability relative to the virgin polystyrene prepared by the same method. Similar temperatures of degradation (at 50% decomposition) were found for these nanocomposites relative to those prepared by bulk polymerization.     

Preparation and characterization of polystyrene–clay nanocomposites by free‐radical polymerization

The polymerizable cationic surfactant, vinylbenzyldimethylethanolammouium chloride (VBDEAC), was synthesized to functionalize montmorillonite (MMT) clay and used to prepare exfoliated polystyrene–clay nanocomposites. The organophilic MMT was prepared by Na⁺ exchanged montmorillonite and ammonium cations of the VBDEAC in an aqueous medium. Polystyrene–clay nanocomposites were prepared by free‐radical polymerization of the styrene containing intercalated organophilic MMT. Dispersion of the intercalated montmorillonite in the polystyrene matrix determined by X‐ray diffraction reveals that the basal spacing is higher than 17.6 nm. These nanocomposites were characterized by differential scanning calorimetry (DSC), transmission electron micrograph (TEM), thermal gravimetric analysis (TGA), and mechanical properties. The exfoliated nanocomposites have higher thermal stability and better mechanical properties than the pure polystyrene. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1370–1377, 2002     

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     

Study of the exfoliation process of epoxy–clay nanocomposites by different curing agents

Epoxy–clay nanocomposites were synthesized using two organoclays cured with different chemicals at different temperatures. Interlayer distance of the clay layers and curing process were investigated by X‐ray diffraction and infrared spectra. The clay treated with facilitated curing agent, 2,4,6‐tris[(dimethylamino)methyl]phenol, can exfoliate at all curing conditions, but for the other clay treated with low‐speed curing agent, p,p′‐diaminodiphenylmethane, exfoliation of the clay layers does not occur. It was found that the relative curing speed between the interlayer and extralayer was the most important factor determining clay exfoliation. Exfoliated epoxy–clay nanocomposites can be prepared if the curing speed of the interlayer is higher than that of the extralayer, irrespective of the curing agent and temperature used. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 511–517, 2003     

Synthesis and properties of polystyrene–clay nanocomposites via in situ intercalative polymerization

Organophilic montmorillonite (MMT) was prepared by ion exchange between Na⁺ ions in the clay and twin benzyldimethyloctadecylammonium bromine cations in an aqueous medium. The organophilic MMT particles were easily dispersed and swollen in styrene monomer. Polystyrene–MMT nanocomposites were prepared by the free‐radical polymerization of styrene containing dispersed clay. The intercalation spacing in the nanocomposites and the degree of dispersion of these composites were investigated with X‐ray diffraction and transmission electron microscopy, respectively. The nanocomposites had higher weight‐average molecular weights, lower glass‐transition temperatures, and better thermal stability (the decomposition temperature was improved by ca. 70°C) than the virgin polystyrene. The rheological behavior of the polystyrene–MMT nanocomposites was also studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 201–207, 2005     

Simultaneous modification of hydrotalcite–silicate nanolayers as reinforcement of a new polyamide: thermal properties and flammability study

New polyamide/clay–layered double hydroxide nanocomposites (PACLN) were prepared from a synthesized aliphatic–aromatic polyamide (AAPA) and organically modified layered double hydroxide–clay (MLC) nanohybrid. MLC was obtained by simultaneous modification of montmorillonite and hydrotalcite nanolayers with cationic–anionic polyethyleneimine/poly(acrylic acid)-co-poly(2-acrylamido-2-methylpropanesulfonic acid) in an ion-exchange reaction. The analysis results indicated that the modification successfully occurred in MLC with increasing interlayer spacing. PACLN were prepared from AAPA and MLC using the solvent-casting technique. The thermal and combustion properties, morphology and structure of the resulting nanocomposites were studied using thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), scanning and transmission electron microscopies, Fourier transform infrared spectroscopy and X-ray diffraction. The results indicated that the silicate and hydrotalcite nanosheets were dispersed in the AAPA matrix. In other words, the silicate and hydrotalcite nanosheets were placed in the AAPA matrix as a new two-dimensional rearranged structure by self-assembly. The TGA results of nanocomposites in N₂ environment showed that PACLN is more heat resistant than AAPA. The 5% mass degradation temperature of PACLN containing 5 mass% of MLC was obtained as almost 60 °C more than that of AAPA. According to MCC results, the peaks of heat release rate were reduced from 156 to 91 W g⁻¹ for AAPA containing 5 mass% of MLC. © 2022 Society of Industrial Chemistry.     

Flammability and thermal stability studies of ABS/Montmorillonite nanocomposite

Acrylonitrile–butadiene–styrene (ABS)/montmorillonite nanocomposites have been prepared using a direct melt intercalation technique by blending ABS and organophilic clay of two different particle sizes: OMTa (5 µm) and OMTb (38 µm). Their structure and flammability properties were characterized by X‐ray diffraction, high resolution electronic microscopy (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results of HREM showed that ABS/5 wt% OMTa nanocomposite was a kind of intercalated–delaminated structure, while ABS/5 wt% OMTb nanocomposite was mainly an intercalated structure. The nanocomposites showed a lower heat release rate peak and higher thermal stability than the original ABS by TGA and cone calorimeter experiments. Also, the intercalated nanocomposite was more effective than an exfoliated–intercalated nanocomposite in fire retardancy. Copyright © 2003 Society of Chemical Industry     

Morphology and rheological properties of nanocomposites based on nitrile rubber and organophilic layered silicates

Organo‐montmorillonite/nitrile rubber (NBR) nanocomposites were prepared by a melt intercalation process. The characteristics of NBR nanocomposites were determined by an oscillating disk rheometer and transmission electron microscopy. The cure characteristics were investigated according to the change in clay content and clay types. This study confirmed that organo‐montmorillonite/NBR nanocomposites have various cure characteristics, namely minimum torque, maximum torque, scorch time and curing time, according to the change in clay content and clay types. In particular, as the chain length of the modifier used for the treatment of Na⁺‐MMT following vulcanization increases, scorch time and optimum curing time are reduced. This is because, as the chain length of the modifier increases, organo‐MMT is distributed more equally during the formation of the nanocomposites. As swelling increases, the chain length of the clay modifier expands and then constitutes a better barrier. Copyright © 2003 Society of Chemical Industry     

Liquid‐crystalline copolyester/clay nanocomposites

A series of novel polymer–clay nanocomposites, that is, liquid‐crystalline copolyester/montmorillonite (MMT) nanocomposites, were synthesized by the intercalation polycondensation of terephthalic acid, p‐acetoxy benzoic acid, and 1,2‐diacetoxy benzene in the presence of different organically modified montmorillonites (OMt's). The OMt's were prepared by the ion exchange of MMT with octadecylamine hydrochloride, p‐aminobenzoic acid hydrochloride, or lysine hydrochloride. X‐ray diffraction and transmission electron microscopy studies indicated that the inorganic cations in the MMT interlayers were already exchanged by organic onium ions and that the OMt intercalated with p‐aminobenzoic acid or lysine was good for obtaining more delaminated clay nanocomposites. The glass‐transition temperature and modulus of the nanocomposites increased compared with those of the pure polymer, whereas the isotropic temperature decreased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3155–3159, 2003     

Rubber–clay nanocomposite by solution blending

Ethylene vinyl acetate rubber (45% vinyl acetate content, EVA‐45) and organomodified clay (12Me‐MMT) composites were prepared by solution blending of the rubber and the clay. A combination of X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy studies showed that the composites obtained are on the nanometer scale. The measurements of the dynamic mechanical properties for different compositions over a temperature range (?100 to +100°C) showed that the storage moduli of these rubber–clay nanocomposites are higher above the glass to rubber transition temperature compared to the neat rubber. The tensile strength of the nanocomposites is about 1.6 times higher than that of the EVA‐45. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2216–2220, 2003     

Polymorphism in intercalated poly(vinylidene fluoride)/clay nanocomposites

Polymorphism in poly(vinylidene fluoride) (PVDF)/clay nanocomposites was studied. Poly(vinylidene fluoride)/clay nanocomposites were prepared with melt intercalation. The samples were characterized with X‐ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy. The nanocomposite exhibited the β form. Thermal annealing performed at 125 and 185°C showed that the β form of PVDF was stable. The stability of the β form of PVDF was ascertained from these studies. The β form of PVDF in the nanocomposites could be due to crystallization in the constrained phase. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2036–2040, 2003     

Synthesis and characterization of hybrid clay/poly (N,N‐dimethylaminoethyl methacrylate) nanocomposites

Four quaternary ammonium salt monomers (2a–d) were synthesized from N,N‐dimethylaminoethyl methacrylate and subsequently polymerized to afford cationic polymers (3a–d). The synthesized monomers and polymers were characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopy. Molecular weights of the synthesized polymers were determined using gel permeation chromatography. Polymer/clay nanocomposites (4a–d) were prepared using solution‐intercalation method and characterized by FTIR, X‐ray diffraction, high‐resolution transmission electron microscopy, energy dispersive X‐ray, and thermogravimetric analysis. Data analysis showed that polymer/clay nanocomposites have intercalated structure. The dielectric properties of the polymer/clay nanocomposites were studied as a function of both temperature and frequency. POLYM. COMPOS., 37:2950–2959, 2016. © 2015 Society of Plastics Engineers     

Antimicrobial resistance of clay polymer nanocomposites

Antimicrobial-resistant polymeric Na⁺–bentonite nanocomposites were prepared by treating Na⁺–bentonite (Na⁺–Bent) with polymeric ultra-thin films of poly(diallyldimethyl ammonium chloride) (PDADMAC), poly(methylmethacrylate) (PMMA) and poly(vinylidene chloride) (PVDC) by admicellar polymerization technique. The clay polymer nanocomposites (CPNs) were characterized by several techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), BET surface analysis, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). In additional, the antimicrobial resistance was studied by measuring the diameter of inhibition zone of growths of Escherichia coli and Salmonella typhimurium. The results showed an inhibitory effect of these CPN against microbial growth in inoculated samples. The CPN exhibited efficacy in the inhibition of bacterial growth.     

Characterization and AC conductivity of polyaniline–montmorillonite nanocomposites synthesized by mechanical/chemical reaction

Polyaniline–clay nanocomposites were prepared by solid state polymerization of aniline chloride in the interlayer of montmorillonite through the use of persulfate of ammonium as oxidant. The proportion of aniline to clay and the molar ratio of oxidant to aniline are being varied. The analyse of UV visible and FTIR spectroscopy demonstrated that aniline has been polymerized to polyaniline (PANI) in its conducting emeraldine form. The conformation adopted by PANI chains in the clay interlayer depended on the molar ratio of aniline to montmorillonite. Thermogravimetric analysis of the nanocomposites suggested that polyaniline chains are more thermally stable than those of free polyaniline prepared by solid–solid reaction. The AC conductivity data of different synthesized nanocomposites were analyzed as a function of frequency. Low frequency conductivities of polyaniline/montmorillonite nanocomposites materials ranges from 0.18 to 5.6 × 10^?3 S/cm. All characterization data were compared to those of free polyaniline that was synthesized using a solid–solid reaction.     

Preparation and characteristics of nitrile rubber (NBR) nanocomposites based on organophilic layered clay

The effect of clay modification on organo‐montmorillonite/NBR nanocomposites has been studied. Organo‐montmorillonite/NBR nanocomposites were prepared through a melt intercalation process. NBR nanocomposites were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA) and a universal testing machine (UTM). XRD showed that the basal spacing in the clay increased, which means that the NBR matrix was intercalated in the clay layer galleries. On TEM images, organo‐montmorillonite (MMT) particles were clearly observed, having been exfoliated into nanoscale layers of about 10–20 nm thickness from their original 40 µm particle size. These layers were uniformly dispersed in the NBR matrix. The DMTA test showed that for these nanocomposites the plateau modulus and glass transition temperature (T_g) increased with respect to the corresponding values of pure NBR (without clay). UTM test showed that the nanocomposites had superior mechanical properties, ie strength and modulus. These improved properties are due to the nanoscale effects and strong interactions between the NBR matrix and the clay interface. Copyright © 2003 Society of Chemical Industry