Biodeterioration of plasticized PVC/montmorillonite nanocomposites in aerobic soil environment

The aim of this study was to assess the effect of montmorillonite nanofillers, Cloisite Na⁺ and Cloisite 30B, on the biodeterioration of PVC-based nanocomposites plasticized by means of dioctyl adipate (DOA), dioctyl phthalate (DOP) and modified poly(propylene adipate) (PPA), in the aerobic environment of soil (soil burial test, time of exposure: 198 days). Tests were carried out at 25 ± 1 °C, under moisture-controlled (55 %) and aerobic conditions. The extent of the biodeterioration process was evaluated on the basis of changes in weight, tensile strength and elongation-at-break values. Finally, analysing chemical structures using FTIR and visual observation, both macroscopic and microscopic via scanning electron microscopy assisted in the evaluation process. The results of this study suggested that plasticized PVC/montmorillonite nanocomposites have an increased susceptibility for undergoing biological deterioration in comparison with plasticized PVC. In each instance, adding Cloisite 30B resulted in reducing the resistance of PVC/montmorillonite nanocomposites to the actions of microorganisms. In the case of Cloisite Na⁺ as the filler, results cannot be clearly quantified, although a negative influence prevailed, particularly a change in colour, whose change intensity was also dependent on the type of plasticizer, increasing in the following sequence: PVC/DOA/Cloisite Na⁺ > PVC/DOP/Cloisite Na⁺ > PVC/PPA/Cloisite Na⁺. However, each sample containing Cloisite Na⁺ achieved a lower rate of degradation (by normalised weight loss and FTIR) compared with nanocomposites containing Cloisite 30B. This can be attributed to the migration and accumulation of Cloisite Na⁺ on the surface of the nanocomposites particles where the former phenomenon producing a surface barrier which caused a reduction in the permeability of the material toward water and microorganisms, during the test.     

Dispersion characteristics and rheology of organoclay nanocomposites based on a segmented main-chain liquid-crystalline polymer having side-chain azopyridine with flexible spacer

The dispersion characteristics and rheology of organoclay nanocomposites based on a main-chain liquid-crystalline polymer having side-chain azopyridine with flexible spacer (PABP) were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and oscillatory shear rheometry. In the preparation of nanocomposites via solution blending under vigorous stirring, two commercial organoclays (Southern Clay Products) were employed: one (Cloisite 30B) treated with a surfactant (MT2EtOH) having hydroxyl groups, and the other (Cloisite 20A) treated with a nonpolar surfactant (2M2HT) having hydrogenated tallow. Also prepared, for comparison, were nanocomposites prepared by mixing PABP with natural clay (montmorillonite, MMT). The following observations were made. (i) PABP/Cloisite 30B nanocomposite has featureless XRD patterns and a very high degree of dispersion of Cloisite 30B aggregates as determined from TEM. (ii) PABP/Cloisite 20A nanocomposite has shown a conspicuous XRD reflection peak and intercalation of Cloisite 20A aggregates as determined from TEM. (iii) PABP/MMT nanocomposite has shown XRD patterns, which are virtually the same as the XRD patterns of neat PABP with a slightly increased gallery distance, and it has very poor dispersion of MMT aggregates in the matrix of PABP. The observed high degree of dispersion of Cloisite 30B aggregates in PABP/Cloisite 30B nanocomposite is attributable to the formation of hydrogen bonds between the pyridyl group of side-chain azopyridine and the hydroxyl groups in the surfactant MT2EtOH residing at the surface of Cloisite 30B. The presence of hydrogen bonds in the PABP/Cloisite 30B nanocomposite was confirmed by in situ Fourier transform infrared (FTIR) spectroscopy. It was observed via polarized optical microscopy that the liquid crystallinity of PABP in the PABP/Cloisite 30B nanocomposites was more or less intact with a very high degree of dispersion of Cloisite 30B aggregates. Oscillatory shear flow measurements of the organoclay nanocomposites prepared support the conclusions drawn from XRD, TEM, and FTIR spectroscopy.     

Preparation and characterization of high performance exfoliated montmorillonite/silicone rubber nanocomposites with enhanced mechanical properties

Highly exfoliated and intercalated silicone rubber (SR) nanocomposites based on natural montmorillonite (Cloisite Na⁺) and organically modified montmorillonite (Cloisite 30B and Cloisite 20A) were successfully prepared by melt‐mixing technique. Dispersion of the nanoclays in the rubber nanocomposites was subsequently investigated. As indicated by the X‐ray diffraction (XRD) analysis, intercalation, and exfoliation of the clay particles in the nanocomposites was achieved at less than 8 parts per hundred (phr) rubber by weight, irrespective of the initial interlayer spacing of the nanoclay particles. Both Cloisite Na⁺ and Cloisite 30B were spontaneously transformed into exfoliated microstructures during the vulcanisation stage. Overall, the use of the nanoclays in silicone rubber improved the Young's modulus, tensile strength, and elongation at break by more than 50% as compared with the control rubber. In addition, this work provided a fresh insight into the way intercalated and exfoliated morphologies affect mechanical properties of silicone rubber nanocomposites. It was shown that the exfoliated Cloisite Na⁺ yielded outstanding mechanical properties with low hysteresis at the same loading of the exfoliated Cloisite 30B and intercalated Cloisite 20A organoclays. As expected, the formation of crosslinks affected the mechanical properties of the rubber vulcanizate significantly. POLYM. ENG. SCI., 53:2603–2614, 2013. © 2013 Society of Plastics Engineers     

Synthesis and characterization of epoxy based nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of the content and type of different clays on the structure and mechanical properties of the nanocomposites. Diglycidyl ether of bisphenol‐A (epoxy) was reinforced by 0.5–11 wt % natural (Cloisite Na⁺) and organically modified (Cloisite 30B) types of montmorillonite. SEM results showed that as the clay content increased, larger agglomerates of clay were present. Nanocomposites with Cloisite 30B exhibited better dispersion and a lower degree of agglomeration than nanocomposites with Cloisite Na⁺. X‐ray results indicated that in nanocomposites with 3 wt % Cloisite 30B, d‐spacing expanded from 18.4 Å (the initial value of the pure clay) to 38.2 Å. The glass transition temperature increased from 73°C, in the unfilled epoxy resin, to 83.5°C in the nanocomposite with 9 wt % Cloisite 30B. The tensile strength exhibited a maximum at 1 wt % modified clay loading. Addition of 0.5 wt % organically modified clay improved the impact strength of the epoxy resin by 137%; in contrast, addition of 0.5 wt % unmodified clay improved the impact strength by 72%. Tensile modulus increased with increasing clay loading in both types of nanocomposites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1081–1086, 2005     

Improving heat ageing and thermal properties of silicone rubber using montmorillonite clay

Heat ageing and thermal stability of a silicone rubber (SR) filled with montmorillonite clay (MMT) was investigated. Three types of rubber nanocomposites were prepared with highly exfoliated Cloisite 30B (SR/C30B), intercalated/exfoliated Cloisite Na⁺ (SR/Na⁺MMT), and highly intercalated Cloisite 20A (SR/C20A). This study showed that the SR/C30B nanocomposite exhibited excellent heat resistance in comparison to the other two nanocomposites and neat SR as revealed by higher retention strength. The thermal stability of the rubber in air was strongly dependent on the clay morphology and increased in the following order: highly intercalated/exfoliated SR/Na⁺MMT < highly intercalated SR/C20A < highly exfoliated SR/C30B. The thermogravimetric analyses of the SR/C30B nanocomposite showed a substantial increase in the final residue in comparison with the neat SR. This indicated a major improvement in the thermal stability of the rubber containing the exfoliated clay, which was also supported by the higher activation energy of decomposition measured for the nanocomposite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41061.     

Melt-compounded salt-containing poly(ethylene oxide)/clay nanocomposites for polymer electrolyte membranes

The present study demonstrates the use of a simple and versatile melt-compounding route to prepare NaClO₄-containing poly(ethylene oxide) PEO/clay nanocomposites combining excellent mechanical properties with a competitive level of the ionic conductivity. The nanostructure and the resulting thermal, mechanical and conductive properties of the salt-containing PEO/clay nanocomposites were found to be highly sensitive to the clay type, i.e. aspect ratio of the clay, to the presence of an organic modifier in the intergallery spacing, and to the salt concentration. The highest increase of the shear storage modulus is obtained in the presence of single silicate layers, thus an exfoliated nanostructure, having a high aspect ratio. These structures are only obtained with an (polar) organically modified clay (Cloisite 30B), regardless of the presence of salt. The use of non-organically modified clays (Cloisite Na⁺ and Laponite) resulted in intercalated nanocomposites, with only a minor improvement in stiffness. A strong interaction between the Na⁺ from NaClO₄ and the Cloisite 30B silicate layers might be responsible for an increased PEO crystallinity and resultant additional increase in stiffness. A mechanism is proposed whereby the Na⁺ ions are drawn away from the PEO phase, to be complexed by the silicate layers, or even ion-exchanged with modifier cations. The addition of clay did not greatly affect the ion conductivity below the melt temperature of PEO. At higher temperatures, the nanocomposites displayed only slightly lower conductivities compared to the PEO/NaClO₄ complex, due to the presence of the clay platelets.     

Supercritical CO2 dispersion of nano-clays and clay/polymer nanocomposites

Dispersed polymer/clay nanocomposites are of great interest because they can significantly improve the properties of existing polymeric materials. However, achieving a high level of clay dispersion has been a key challenge in the production of polymer/clay nanocomposites. In this paper, we explore a novel supercritical carbon dioxide (scCO₂) processing method that utilizes scCO₂ to disperse nano-clays. The structure and properties of the clays and the resultant nanocomposites are characterized using a combination of wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and rheology. Significant dispersion was achieved with dry Cloisite 93A clay, whereas relatively poor dispersion was achieved with dry Cloisite Na⁺ (natural clay). The extent of clay dispersion appears to be dependent on the ‘CO₂-philicity’, which in turn appears to depend on the surface modifications and inter-gallery spacing. The presence of an acidic hydrogen on the surfactant in Cloisite 93A appears to play a strong role in its ‘CO₂-philicity’. The ability to delaminate dry clays is significant because it will likely increase the ability to produce dispersed clay/polymer nanocomposites via melt processing. In addition to delaminating dry clays, we demonstrate that CO₂-phobic Cloisite Na⁺ (natural clay) can be partially dispersed with scCO₂, using a CO₂-philic polymer, polydimethylsiloxane (PDMS). The dispersed clay/PDMS nanocomposite shows an order of magnitude increase in the dynamic storage modulus at low frequencies, accompanied by the emergence of a ‘solid-like’ plateau, characteristic of dispersed nanocomposites with enhanced clay/polymer interactions.     

Studies of particle dispersion in plasticized poly(vinyl chloride)/montmorillonite nanocomposites

Poly(vinyl chloride)(PVC) and dioctyl phthalate (DOP) were mixed with 5 and 10 wt % of Cloisite Na⁺, Cloisite 30B or Cloisite 93A. The obtained nanocomposites were characterized by thermal analysis using a thermogravimetric analyzer which showed that addition of 5 wt % of nanoclay to PVC increased its thermal stability in the sequence: Cloisite Na⁺< Cloisite 93A< Cloisite 30B. The electrical conductivity of these composites was studied as a function of temperatures and showed that the conductivity of PVC was enhanced upon using 5 wt % of nanoclay in the sequence: Cloisite Na⁺< Cloisite 30B < Cloisite 93A. The activation energy of interaction of PVC with nanoclay was found to be lowest for the composite containing 5 wt % of nanoclay in the same sequence. The tensile strength, elongation (%), and Young's modulus were considerably enhanced upon increasing the clay content to 5 wt % in the sequence: Cloisite Na⁺< Cloisite 93A < Cloisite 30B. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study these nanocomposite structures, and it was found that the organoclay layers are homogeneously dispersed in the PVC matrix when 5 wt % of Cloisite 30B or Cloisite 93A was used. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Nanostructure and dynamic mechanical properties of silane-functionalized montmorillonite/epoxy nanocomposites

In this work sodium montmorillonite (Na-MMT) was functionalized with N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane and the corresponding silylated clay was used to modify epoxy matrix cured with triethylenetetramine. The grafting/intercalation of the aminosilane inside the clay galleries were followed by infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and ²⁹Si cross-polarization magic-angle-spinning nuclear magnetic-resonance (CP/MAS NMR) spectroscopy. Epoxy-based nanocomposites were prepared with different amounts of silylated clay or commercial organoclay, Cloisite 30B, whose intercalating agent consists of a methyl, tallow, bis-2-hydroxyethyl quaternary ammonium salt. The degree of intercalation/exfoliation was estimated by X-ray diffraction experiments and confirmed by small angle X-ray scattering. Nanocomposites prepared with silylated clay displayed no peak in both XRD and SAXS curves whereas those prepared with Cloisite 30B exhibited a clear interference peak corresponding to an interlayer spacing d₀₀₁ of 4.1 nm. The former also presented a better dispersion, with a high proportion of tactoids smaller than 2 nm, as estimated by SAXS. From the results of dynamic mechanical analysis it was observed that most of the nanocomposites display higher storage modulus mainly at temperatures above the glass transition temperature. The glass transition temperature is similar or higher than the neat epoxy network for nanocomposites containing 1 wt.% of silylated clay or higher.     

Morphology and Thermal Stability of Novolac Phenolic Resin/Clay Nanocomposites Prepared via Solution High‐Shear Mixing

Phenolic resin/clay composites were prepared by high‐shear mixing of clay suspended in CH₃OH solutions of Novolac resin and curing agent. Pure clay Cloisite Na⁺ and pillared clays Cloisite 10A, 30B, and Na⁺Cloisite that was pillared by 3‐hexadecyl‐1‐methylimidazolium bromide were studied. After CH₃OH evaporation, Novolac was cured at low temperatures. XRD showed that clay gallery d‐spacings decreased upon solvent evaporation and partial curing. Slight d‐spacing increases were sometimes observed from a partially cured stage to a further cured composite. Na⁺Cloisite gave the highest nanodispersion, Cloisites 10A and 30B the lowest. TGA revealed that Na⁺ clay or organoclay incorporation in partially cured and cured composites did not improve the thermal stability of Novolac.

     

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     

Ion-dipole interactions in the dispersion of organoclay nanocomposites based on polystyrene-block-poly(2-vinylpyridine) copolymer

The dispersion characteristics of organoclay nanocomposites based on polystyrene-block-poly(2-vinylpyridine) (S2VP diblock) copolymer were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), and solid-state nuclear magnetic resonance (NMR) spectroscopy. For the investigation, S2VP diblock copolymers having three different compositions were synthesized via sequential anionic polymerization. Each S2VP diblock copolymer was used to prepare nanocomposites by solution blending with natural clay (montmorillonite, MMT) or commercial organoclays (Cloisite 30B, Cloisite 10A, Cloisite 15A, and Cloisite 25A from Southern Clay Products). All four organoclays employed were treated with a surfactant having quaternary ammonium salt with N⁺ ion. It was found, via TEM and XRD, that the nanocomposites with MMT show very poor dispersion characteristics regardless of block copolymer composition. However, the block copolymer composition was found to have a profound influence on the dispersion characteristics of the nanocomposites with an organoclay. Specifically, the nanocomposites based on S2VP-5 having 5 wt% poly(2-vinylpyridine) (P2VP) block gave rise to a very high degree of dispersion, irrespective of the chemical structure of the surfactant residing at the surface of the organoclay employed, whereas the dispersion characteristics of the nanocomposites became progressively poorer as the amount of P2VP block in an S2VP diblock copolymer increased from 5 to 25 wt% and to 56 wt%. The observed dispersion characteristics were explained by hypothesizing the presence of ion-dipole interactions between the positively charged N⁺ ions in the surfactant residing at the surface of the organoclay nanoparticles and the dipoles in the P2VP block of S2VP diblock copolymers. The validity of this hypothesis was confirmed using solid-state NMR spectroscopy, by determining the dependence of the composition of S2VP diblock copolymer on the extent of ion-dipole interactions and thus on the dispersion characteristics of the nanocomposites prepared.     

Preparation and Properties of Biodegradable Thermoplastic Starch/Clay Hybrids

Biodegradable thermoplastic starch (TPS)/clay hybrids were prepared by melt intercalation. Three organically modified montmorillonite (MMT) with different ammonium cations and one unmodified Na⁺ MMT (Cloisite Na⁺) were used. Cloisite Na⁺ showed the best dispersion in the TPS matrix. It was observed that the TPS/Cloisite Na⁺ hybrid showed an intercalation of TPS in the silicate layer due to the matching of the surface polarity and interactions of the Cloisite Na⁺ and the TPS, which gives higher tensile strength and better barrier properties to water vapor as compared to the other TPS/organoclay hybrids as well as the pristine TPS. It was found that the dynamic mechanical properties of the TPS/clay hybrids were also affected by the polar interactions.     

Formation of polymer nanocomposites with various organoclays

The role of the type of organic modifier used with montmorillonite (MMT) on the formation of polymer/clay nanocomposites in the melt compounding process was investigated. Various organoclays including primary [12‐aminolauric acid (12ALA)], secondary [dioctylamine (DOA)], tertiary [trioctylamine (TOA)], and two commercial quaternary (Cloisite 30B and 20A) MMTs were melt compounded with carefully selected polymers including polypropylene, polystyrene, styrene–acrylonitrile copolymer, poly(methyl methacrylate), poly(vinylidene fluoride), and acrylonitrile–butadiene copolymer (NBR). X‐ray diffraction and transmission electron microscopy characterizations confirmed that the two quaternary ammonium organoclay (Cloisite 30B and 20A) have superior compatibility compared to the primary (12ALA), secondary (DOA), and tertiary (TOA) ammonium organoclay. DOA and TOA can form polymer/clay nanocomposites only with the most polar polymer (NBR). Cloisite Na⁺ and 12ALA can not form nanocomposite with any polymers. The large organic surface area of the quaternary ammonium organoclay could be the reason of the best compatibility with polar polymers. It is estimated that long alkyl ammonium chains of organic modifier can spread over the clay surface more effectively than short alkyl chains. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1888–1896, 2005     

Preparation and UV weathering of polyethylene nanocomposites

Polyethylene / montmorillonite (PE/MMT) nanocomposites films were prepared by blending in the molten state: Low-density polyethylene (LDPE), montmorillonite clay, and polyethylene grafted maleic anhydride (LDPE-g-MA) or zinc neutralized carboxylate ionomer (Surlyn B) as compatibilizers. A chemically modified clay Cloisite 20A has been used. Nanocomposites were prepared by melt blending in a twin-screw extruder by using two-step mixing. Characterization of the nanocomposites was performed by mechanical properties, X-ray diffraction, light transmittance, infrared spectroscopy (FTIR) and transmission electronic microscope (TEM) techniques. Changes in UV irradiated nanocomposites film samples were characterized by FTIR. The results were analyzed in terms of the effect of the compatibilizing agent in the clay dispersion, and UV degradation of the nanocomposite.     

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.     

Intercalated PS/Na+‐MMT Nanocomposites Prepared by Ultrasonically Initiated In Situ Emulsion Polymerization

Summary: A new technique, ultrasonically initiated in situ emulsion polymerization, was employed to prepare intercalated polystyrene/Na⁺‐MMT nanocomposites. FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily intercalate into the galleries of hydrophilic montmorillonite via ultrasonically initiated in situ emulsion polymerization, taking advantages of the multi‐effects of ultrasonic irradiation, such as dispersion, pulverization, activation, and initiation. Properly reducing SDS concentration is beneficial to widen the d‐spacing between clay layers. However, the Na⁺‐MMT amount has little effect on the d‐spacing of nanocomposites. The glass transition temperature of nanocomposites increased as the percentage of clay increased, although the average molecular weight of PS decreased, and the decomposition temperature of the 1obtained nanocomposites moves to higher temperature.

TEM of PS/Na⁺‐MMT nanocomposite prepared by ultrasonically initiated in situ emulsion polymerization.     

Water uptake behavior of layered silicate/starch–polycaprolactone blend nanocomposites

The water uptake behavior of biodegradable layered silicate/starch–polycaprolactone blend nanocomposites was evaluated. Three different commercial layered silicates (Cloisite Na⁺, Cloisite 30B and Cloisite 10A) were used as reinforcement nanofillers. Tests were carried out in two different environments: 60 and 90% relative humidity using glycerol solutions. The clay/starch–polycaprolactone blend nanocomposites were obtained by melt intercalation and characterized by gravimetric measurements and tensile tests. The intercalated structure (determined by wide‐angle X‐ray diffraction) showed a decrease in water absorption as a function of clay content probably due to the decrease of the mean free path of water molecules. The diffusion coefficient decreased with clay incorporation but a further increase in the clay content did not show an important effect on this parameter. Elongation at break increased with exposure showing matrix plasticization. Mechanical properties of the nanocomposites deteriorated after exposure whereas they remained almost constant in the case of the neat matrix. Copyright © 2007 Society of Chemical Industry     

Synthesis of exfoliated polyaniline–clay nanocomposite in supercritical CO2

This paper presents the works done to synthesize fully exfoliated polyaniline–clay nanocomposites (PCNs) with high purity via in situ polymerization of aniline in Cloisite 30B nano-clay suspension in supercritical CO₂ (ScCO₂) medium. The Cloisite 30B was first delaminated with ScCO₂ treatment in the presence of aniline monomers. Ammonium peroxydisulfate (APS) solution was added rapidly into the mixture of delaminated Cloisite 30B and aniline monomers to produce PCNs. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy and XRD analysis have been used to characterize the morphology and structure of the as-synthesized product. SEM results reveal that nano-clays are fully exfoliated in the final nanocomposite which is synthesized in ScCO₂. FTIR and UV–vis analysis showed that the resulted polyaniline (PANI) had been in highly conductive emeraldine salt state and ScCO₂ does not have any effect on chemical structures of the PANI.