Polyamide- and polycarbonate-based nanocomposites prepared from thermally stable imidazolium organoclay

This paper explores the possible advantages of the more thermally stable imidazolium-based organoclay over a more conventional ammonium-based organoclay for facilitating exfoliation and minimizing polymer matrix degradation in melt blended polyamide 6 (PA-6) and polycarbonate (PC) nanocomposites. The thermal stability of the two organoclays was evaluated by TGA analyses. The extent of clay exfoliation was judged by analysis of the morphology and tensile modulus of these nanocomposites formed using a DSM Microcompounder, while the extent of color formation and molecular weight change were used to evaluate polymer matrix degradation. For PA-6 and PC nanocomposites, the use of the imidazolium organoclay only produced slight differences in both exfoliation and molecular weight change, although the imidazolium organoclay is remarkably more thermally stable than the ammonium organoclay.     

Effect of organoclay structure on nylon 6 nanocomposite morphology and properties

A carefully selected series of organic amine salts were ion exchanged with sodium montmorillonite to form organoclays varying in amine structure or exchange level relative to the clay. Each organoclay was melt-mixed with a high molecular grade of nylon 6 (HMW) using a twin screw extruder; some organoclays were also mixed with a low molecular grade of nylon 6 (LMW). Wide angle X-ray scattering, transmission electron microscopy, and stress-strain behavior were used to evaluate the effect of amine structure on nanocomposite morphology and physical properties. Three surfactant structural issues were found to significantly affect nanocomposite morphology and properties in the case of the HMW nylon 6: decreasing the number of long alkyl tails from two to one tallows, use of methyl rather than hydroxy-ethyl groups, and use of an equivalent amount of surfactant with the montmorillonite, as opposed to adding excess, lead to greater extents of silicate platelet exfoliation, increased moduli, higher yield strengths, and lower elongation at break. LMW nanocomposites exhibited similar surfactant structure-nanocomposite behavior. Overall, nanocomposites based on HMW nylon 6 exhibited higher extents of platelet exfoliation and better mechanical properties than nanocomposites formed from the LMW polyamide, regardless of the organoclay used. This trend is attributed to the higher melt viscosity and consequently the higher shear stresses generated during melt processing.     

Effect of organoclay purity and degradation on nanocomposite performance, Part 2: Morphology and properties of nanocomposites

Part 1 of this series showed that the purification level and surfactant loadings of organoclays significantly affect their thermal stability; the higher rate of degradation of as-received commercial organoclay is primarily a result of excess surfactant that is intentionally or unintentionally part of the commercial organoclay. Polypropylene nanocomposites and nylon 6 nanocomposites were formed through melt processing to assess the practical consequences, in terms of nanocomposite formation and performance, of using a purified version of the organoclay with no excess surfactant and a lower rate of thermal degradation versus using the as-received organoclay. The properties and morphology of polymer-clay nanocomposites based on both as-received and purified organoclays were evaluated by TEM, WAXS, and mechanical testing. The results from the different techniques were generally consistent with each other suggesting that the differences in thermal stability of organoclays do not appear to have a significant effect on the morphology and properties of the nanocomposites formed from them.     

Polycarbonate nanocomposites: Part 2. Degradation and color formation

Polycarbonate nanocomposites were prepared using two different twin screw extruders from a series of organoclays based on sodium montmorillonite, with somewhat high iron content, exchanged with various amine surfactants. It seems that a longer residence time and/or broader residence time distribution are more effective for dispersing the organoclay. The effects of organoclay structure on color formation during melt processing were quantified using colorimeter and UV-Vis spectroscopy techniques. Color formation in the PC nanocomposites depends on the type of organoclay and the type of pristine clay employed. Double bonds in the hydrocarbon tail of the surfactants lead to more darkly colored materials than saturated surfactants. The most severe color was observed when using a surfactant containing hydroxy-ethyl groups and a hydrocarbon tail derived from tallow. Molecular weight degradation of the PC matrix during melt processing produces phenolic end groups which were tracked by UV-Vis spectroscopy. Greater dispersion of the clay generally led to higher reduction in molecular weight due to the increased surface area of clay exposed; however, for color, the situation is far more complex. Hydroxy-ethyl groups and tallow unit on the surfactant lead to more degradation. A selected series of organoclays based on synthetic clay Laponite^® and calcium montmorillonite from Texas (TX-MMT) were also prepared to explore the effects of the clay structure. Laponite^® and TX-MMT produce less color formation in PC nanocomposites than montmorillonite probably due to lower content of iron. Dynamic rheological properties support the trends of molecular weight degradation and dispersion of clay.     

Organoclay degradation in melt processed polyethylene nanocomposites

Melt processed nanocomposites were formed from low-density polyethylene, LDPE, and organoclays over a wide range of processing temperatures. These composites show limited exfoliation, and hence, their X-ray analysis reveals a distinct peak corresponding to the interplatelet distances in the unexfoliated clay galleries. The degradation of the quaternary ammonium surfactant of the organoclay in these systems was characterized by examining the change in the position of these peaks as a function of the melt processing temperature. Upon degradation, the mass of the surfactant within the clay galleries decreases, which causes the platelets to collapse and shifts the WAXS peak to lower d-spacings. The results of the WAXS analysis suggest that a significant portion of the surfactant is lost from the organoclays when the melt processing temperature is increased from 180 to 200 °C or higher. The extent of surfactant degradation in these composites was determined to be independent of the organoclay content. Organoclay degradation appears to limit the extent of exfoliation or dispersion in LDPE as revealed by stress-strain analyses of nanocomposites processed at different temperatures. The amount of surfactant lost during thermogravimetric analysis of various organoclays indicates that surfactants with multiple alkyl tails have greater thermal stability than those with a single alkyl tail. A comparison of the mass of surfactant lost during melt processing of nanocomposites and during thermogravimetric analysis of organoclays (in the absence of polymer) indicated that at a given time, a larger surfactant loss from the clay galleries occurs during extrusion than during the TGA experiment. This is attributed to the greater ease with which the degradation products (predominantly α-olefins) are solubilized in polyethylene for the composites as opposed to evaporated from the organoclay during TGA.     

Effect of organoclay structure on morphology and properties of nanocomposites based on an amorphous polyamide

An amorphous polyamide (a-PA) and three organoclays, M₃(HT)₁, M₂(HT)₂ and (HE)₂M₁T₁, were melt processed to explore the effect of the organoclay structure on the extent of exfoliation and properties of these nanocomposites. Wide angle X-ray scattering, transmission electron microscopy, and stress-strain behavior were used to determine the degree of exfoliation of the nanocomposites. For quantitative assessment of the structure of the nanocomposites, a detailed particle analysis was made to provide various averages of the clay dimensions and aspect ratio. The results evaluated from different methods were generally consistent with each other. Nanocomposites based on the organoclays with one alkyl tail and hydroxyl ethyl groups gave well-exfoliated structures and high matrix reinforcement while nanocomposites from two-tailed organoclay contain a considerable concentration of intercalated stacks. Nanocomposites from the organoclays with one alkyl tail showed slightly better exfoliation and matrix reinforcement than those from the organoclays with hydroxyl ethyl groups. The organoclay structure trends for a-PA are analogous to what has been observed for nylon 6; this suggests that a-PA, like nylon 6, has good affinity for the pristine silicate surface of the clay leading to better exfoliation and enhanced mechanical properties with one-tailed organoclay than multiple-tailed organoclay. Furthermore, heat distortion temperatures were predicted from the dynamic mechanical properties of nanocomposites.     

Nanocomposites from poly(ethylene-co-methacrylic acid) ionomers: effect of surfactant structure on morphology and properties

A detailed study of the structure-property relationships for nanocomposites prepared using melt processing techniques from a sodium ionomer of poly(ethylene-co-methacrylic acid) and a series of organoclays is reported. Transmission electron microscopy, X-ray scattering, stress-strain behavior, and Izod impact analysis were used to evaluate the nanocomposite morphology and physical properties. Four distinct surfactant structural effects lead to improved levels of exfoliation and higher stiffness for these nanocomposites: higher number of alkyl tails on the amine rather than one, longer alkyl tails instead of shorter ones, use of 2-hydroxy-ethyl groups as opposed to methyl groups on the ammonium ion, and an excess amount of the amine surfactant on the clay instead of an equivalent amount. These trends are opposite of what has been seen in nylon 6 based nanocomposites but are similar to those observed in nanocomposites formed from LDPE and LLDPE. Although some organoclays were exfoliated better than others, none of the ionomer-based nanocomposites exhibited exfoliation levels as great as those seen in nylon 6 nanocomposites; nevertheless, these nanocomposites offer promising improvements in performance and may be particularly interesting for barrier applications.     

Nylon 6 nanocomposites prepared by a melt mixing masterbatch process

A melt mixing masterbatch process for preparing nylon 6 nanocomposites that provides good exfoliation and low melt viscosities has been investigated. It is known that high molecular weight (HMW) grades of nylon 6 lead to higher levels of exfoliation of organoclays than do low molecular weight (LMW) grades of nylon 6. However, LMW grades of nylon 6 have lower melt viscosities, which are favorable for certain commercial applications like injection molding. To resolve this, a two-step process to prepare nanocomposites based on nylon 6 is explored here. In the first step, a masterbatch of organoclay in HMW nylon 6 is prepared by melt processing to give exfoliation. In the second step, the masterbatch is diluted with LMW nylon 6 to the desired montmorillonite (MMT) content to reduce melt viscosity. Wide angle X-ray scattering, transmission electron microscopy, and stress-strain analysis were used to evaluate the effect of the clay content in the masterbatch on the morphology and physical properties of the final nanocomposite. The melt viscosity was characterized by Brabender Torque Rheometry. The physical properties of the nanocomposites prepared by the masterbatch approach lie between those of the corresponding composites prepared directly from HMW nylon 6 and LMW nylon 6. A clear trade-off was observed between the modulus and melt processability. Masterbatches that have lower MMT content offer a significant decrease in melt viscosity and a small reduction in modulus compared to nanocomposites prepared directly from HMW nylon 6. Higher MMT concentrations in the masterbatch lead to a less favorable trade-off.     

Crystallization behavior of nylon 6 nanocomposites

The crystallization behavior of nylon 6 nanocomposites formed by melt processing was investigated. Nanocomposites were produced by extruding mixtures of organically modified montmorillonite and molten nylon 6 using a twin screw extruder. Isothermal and non-isothermal crystallization studies involving differential scanning calorimetry (DSC) were conducted on samples to understand how organoclay concentration and degree of clay platelet exfoliation influence the kinetics of polyamide crystallization. Very low levels of clay result in dramatic increases in crystallization kinetics relative to extruded pure polyamide. However, increasing the concentration of clay beyond these levels retards the rate of crystallization. For the pure nylon 6, the rate of crystallization decreases with increasing the molecular weight as expected; however, the largest enhancement in crystallization rate was observed for nanocomposites based on high molecular weight polyamides; this is believed to stem from a higher degree of platelet exfoliation in these nanocomposites. Wide angle X-ray diffraction (WAXD) and DSC were further used to characterize the polymer crystalline morphology of injection molded nanocomposites. The outer or skin layer of molded specimens was found to contain only γ-crystals; whereas, the central or core region contains both the α and γ-forms. The presence of clay enhanced the γ-structure in the skin; however, the clay has little effect on crystal structure in the core. Interestingly, higher levels of crystallinity were observed in the skin than in the core for the nanocomposites, while the opposite was true for the pure polyamides. In general, increasing the polymer matrix molecular weight resulted in a lower degree of crystallinity in molded samples as might be expected.     

Effect of sodium montmorillonite source on nylon 6/clay nanocomposites

The effect of sodium montmorillonite source on the morphology and properties of nylon 6 nanocomposites was examined using equivalent experimental conditions. Sodium montmorillonite samples acquired from two well-known mines, Yamagata, Japan, and Wyoming, USA, were ion exchanged with the same alkyl ammonium chloride compound. The resulting organoclays were extruded with a high molecular weight grade of nylon 6 under the same processing conditions. Quantitative analysis of TEM photomicrographs of the two nanocomposites reveal a slightly larger average particle length and a slightly higher degree of platelet exfoliation for the Yamagata based nanocomposite than the Wyoming version, thus, translating into a higher particle aspect ratio. The stress-strain behavior of the nanocomposites appears to reflect the nanocomposite morphology, in that higher stiffness and strengths are attainable with the increased particle aspect ratio. Moreover, the trends in stiffness behavior between the two types of nanocomposites may be explained by conventional composite theory.     

Influence of organoclay and preparation technique on the morphology of polyamide6/polystyrene/organoclay nanocomposites

To have an improved insight about the compatibilization effect of organoclay on immiscible polymers, two different organoclays and preparation techniques were chosen to prepare polyamide6 (PA6)/polystyrene (PS)/organoclay ternary nanocomposites. The morphology analysis based on the results of X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy demonstrated that the type of organoclay and preparation technique had a significant influence on the dispersion and distribution of organoclay in the polymer. It was concluded that blending PS/organoclay nanocomposite synthesized previously via in situ bulk polymerization, with PA6 can realize the full exfoliation of organoclay in the final ternarynanocomposite, while an intercalated structure was achieved by directly blending the three components. The distribution of organoclay could be controlled by tuning the surface property of clay, and hence the interfacial interaction between clay and the polymer matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Intercalation and viscoelasticity of poly(ether-block-amide) copolymer/montmorillonite nanocomposites: Effect of surfactant

A poly(ether-block-amide) copolymer (PEBA) was successfully hybridized with montmorillonites using melt processing techniques to form nanocomposites. The organoclays used in preparation of the nanocomposites were modified with ammonium surfactants of different molecular structures to study the effect of the surfactant on the intercalation and exfoliation of the polymer by X-ray diffraction (XRD) and dynamic linear viscoelastic analysis. The polymer was found to be capable of forming intercalated composite with unmodified montmorillonite and the best intercalation and exfoliation was found in the hybrids using surfactants that possess hydroxyl group. Organoclays modified with a single tallow tail ammonium prevailed over those modified with a double tallow tail ammonium in intercalation and exfoliation of silicate layers. Higher capacity of ion exchange also led to a better intercalation for hybrids using single tail surfactants, but the hybrids with swallow tail surfactant behaved oppositely. XRD data showed that the diffraction peaks in the hybrids were narrower than those of the organoclay implying a higher order and more number of layers in the stacks of clays. The intercalation of nanocomposites was found dominated by the energetic factor and entropic factor played no role in the outcome of intercalation. Results of linear viscoelastic measurements paralleled those of XRD showing that melts of those nanocomposites with a superior intercalation or exfoliation also exhibited higher storage modulus and thus the linear viscoelasticity could be an indicator for intercalation. The composites showed an abnormal terminal behavior suggesting the existence of a network structure.     

Polycarbonate nanocomposites. Part 1. Effect of organoclay structure on morphology and properties

Polycarbonate nanocomposites were prepared by melt processing from a series of organoclays based on sodium montmorillonite exchanged with various amine surfactants. To explore the effects of matrix molecular weight on dispersion, an organoclay was melt-mixed with a medium molecular weight polycarbonate (MMW-PC) and a high molecular weight polycarbonate (HMW-PC) using a twin screw extruder. The effects of surfactant chemical structure on the morphology and physical properties were explored for nanocomposites formed from HMW-PC. Wide angle X-ray scattering, transmission electron microscopy, and stress-strain behavior were employed to investigate the nanocomposite morphology and physical properties. The modulus enhancement is greater for nanocomposites formed from HMW-PC than MMW-PC. This trend is attributed to the higher shear stress generated during melt processing. A surfactant having both polyoxyethylene and octadecyl tails shows the most significant improvement in modulus with some of the clay platelets fully exfoliated. However, the nanocomposites formed from a range of other organoclays contained both intercalated tactoids and collapsed clay particles with few, if any, exfoliated platelets.     

Morphology and properties of nanocomposites formed from ethylene-vinyl acetate copolymers and organoclays

A series of ethylene-vinyl acetate copolymers, EVA, containing 0-40% VA and three organoclays, M₂(HT)₂, M₃(HT)₁ and (HE)₂M₁T_1, were melt processed to explore the relationship between the polarity of the polymer matrix and the organoclay structure on the extent of exfoliation and properties of the resulting nanocomposites. The degree of exfoliation of the nanocomposites was evaluated by TEM, WAXS, and mechanical testing. Quantitative particle analyses of TEM images were made to give various averages of the clay dimensions and aspect ratio. The results from different techniques were generally consistent with each other. These EVA copolymer nanocomposites show dramatically improved exfoliation of the organoclay as the VA content is increased. Nanocomposites based on the organoclay with two alkyl tails always gave better exfoliation than those based on the organoclays with a single tail at all VA levels; however, the relative advantage of the two tails versus one tail seems to diminish with increased VA level. The predictions of tensile modulus using a simple composite model based on Halpin-Tsai equations show rather good agreement with the experimental data.     

Structure,thermal stability,and mechanical properties of nanocomposites based on an amorphous polyamide

Polymer nanocomposites based on an amorphous polyamide (aPA) modified with three organoclays were obtained in the melt state. The observed T_g decreases indicated that some organic modifier of the OMMT (surfactant) migrated to the matrix during mixing. The decrease in the thermal stability of the aPA in nitrogen atmosphere on organoclay addition was attributed to the instability of the organoclays. The smaller decrease in the thermal stability of the nanocomposites in air atmosphere was attributed to a barrier effect. The largest dispersion (an average of only 1.2 layers per particle) occurred using the octadecylamine‐modified organoclay (I30) that has the maximum uncovered surface; this indicates the basic importance of this parameter on exfoliation. Despite the bulky nature of the aPA that hinders the matrix/inorganic surface interactions, this dispersion level is comparable to that of semicrystalline polyamides with similar polarity. This indicates that the relation between high polarity of the matrix and high dispersion level also works in bulky aPAs, as that of this study. The significant modulus increases (56% for the nanocomposite with 5% I30) are consistent with the measured high dispersion level. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

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.     

Morphology and properties of thermoplastic polyurethane nanocomposites: Effect of organoclay structure

A series of alkyl ammonium/MMT organoclays were carefully selected to explore structure-property relationships for thermoplastic polyurethane (TPU) nanocomposites prepared by melt processing. Each organoclay was melt-blended with a medium-hardness, ester-based TPU, while a more limited number of organoclays was blended with a high-hardness, ether-based TPU. Wide-angle X-ray scattering, transmission electron microscopy, particle analysis, and stress-strain behavior were used to examine the effects of organoclay structure and TPU chemical structure on morphology and mechanical properties. Specifically, the following were observed: (a) one long alkyl tail on the ammonium ion rather than two, (b) hydroxy ethyl groups on the amine rather than methyl groups, and (c) a longer alkyl tail as opposed to a shorter one leads to higher clay dispersion and stiffness for medium-hardness TPU nanocomposites. Overall, the organoclay containing hydroxy ethyl functional groups produces the best dispersion of organoclay particles and the highest matrix reinforcement, while the one containing two alkyl tails produces the poorest. The two TPU's exhibit similar trends with regard to the effect of organoclay structure. The high-hardness TPU nanocomposites showed a slightly higher number of particles and clay dispersion. The organoclay structure trends are analogous to what has been observed for nylon 6-based nanocomposites; this suggests that polar polymers like polyamides, and apparently polyurethanes, have a relatively good affinity for the polar clay surface; and in the case of polyurethanes, the high affinity of the matrix for the hydroxy ethyl functional groups in the organoclay aids clay dispersion and exfoliation.     

Characterization of nanoclay orientation in polymer nanocomposite film by small-angle X-ray scattering

The orientation distribution of layer-shaped nanoclays (e.g. organoclays and pristine clays) dispersed in a polymer matrix is an important parameter to control the properties of polymer nanocomposites. In this study, we demonstrate that the use of multi-directional 2-D small-angle X-ray scattering (SAXS) can quantitatively describe the orientation distribution of organoclays (e.g. Cloisite C20A) in melt-pressed nanocomposite films, containing ethylene-vinyl acetate (EVA) copolymers as polymer matrices. Different weight fractions of organoclays were used to alter the orientation profile of nanocomposite films, in which the dispersion and morphology of organoclays were also characterized by complementary 2-D and 3-D transmission electron microscopy (TEM). All nanocomposites exhibited mixed intercalation/exfoliation clay morphology, where the intercalated structure possessed partial orientation parallel to the in-plane direction of the film. The higher content of the clay loading showed a higher clay orientation. A simple analytical scheme for SAXS data analysis to determine the orientation parameter (P₂) was demonstrated, the results of which are in agreement with the gas permeation properties of the nanocomposite films.     

Rheological and mechanical comparative study of in situ polymerized and melt-blended nylon 6 nanocomposites

The rheological and mechanical properties of commercial neat nylon 6 and nylon 6 nanocomposites containing organically-modified montmorillonite (organoclays) produced by either in situ polymerization or melt-blending were investigated. The dynamic and steady shear, capillary and extensional viscosity of the neat nylon 6 and nylon 6 nanocomposite melts were studied, as well as the tensile properties of the solid material. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the organoclays were largely very well exfoliated, although the lateral size scale of the platelets was different for each material. The in situ polymerized nanocomposite exhibited higher melt viscosity and higher tensile ductility than the melt-blended nanocomposite which was related to improved dispersion and polymer-silicate interactions for this material. Scanning electron microscopy confirmed that the nanocomposite failure surfaces showed more evidence of brittle behavior than the failure surfaces of neat nylon 6, and also that agglomerates of organoclay could be seen easily in the fracture surface of the melt-blended nanocomposite, but not to the same degree as in the in situ polymerized nanocomposite. This is in addition to very fine, individually-dispersed silicate laminates that form in each case.     

Diffusion behavior of water and sulfuric acid in epoxy/organoclay nanocomposites

The research on polymer‐layered silicate nanocomposites is currently an expanding field of study because they often exhibit a wide range of improved properties over their unmodified starting polymers. Epoxy/organoclay nanocomposites have been prepared by intercalating epoxy into the organoclay montmorillonite. The intercalation and/or exfoliation of the clay within the nanocomposite were monitored using X‐ray diffraction and transmission electron microscopy. Diffusion was studied through epoxy samples containing up to 10 phr of organically treated montmorillonite following the gravity method. The water and sulfuric acid diffusion within the epoxy‐based nanocomposites were evaluated in terms of diffusivity, weight change and penetration depth of the sulfuric acid element S as function of immersion time and immersion temperature. An investigation of the resistance of epoxy nanocomposite to a corrosive environment by immersion into sulfuric acid at elevated temperature was performed. The effect of the degree of exfoliation of the clay on moisture barrier effect and corrosion resistance is specifically studied. The data has been compared to those obtained from the neat epoxy resin to evaluate the diffusion properties of the nanocomposites. It was found that the diffusion of water and that of acid do not obey Fick's law, and that the higher the organoclay content the higher weight change was obtained. The presence of the organoclay enhanced the diffusivity and delayed the penetration of the sulfuric acid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009