Intercalation Of Nanoclay Research Articles

Rheological Behaviour of Styrene-Free Unsaturated Polyester-Clay Nanocomposites

The rheological behaviour of styrene-free unsaturated polyester resin-organoclay (Cloisite 15A) nanocomposites at various clay contents, prepared by melt mixing, was investigated. Styrene-free resin was used to achieve high-shear mixing and to avoid viscosity changes due to solvent evaporation. In order to compare the effects of shear- and diffusion-induced phenomena on the intercalation of nanoclay; samples were prepared at two different temperatures of 40 °C (cold-mixed) and 150 °C (hot-mixed) and tested in the range of 40-120 °C using dynamic rheometry. Complex viscosity-temperature curves for cold-mixed samples showed a decrease in viscosity with increasing temperature followed by the formation of a plateau at a particular temperature, depending on the clay content. This behaviour is characteristic of systems with a network structure. The results of small angle X-ray diffraction and TEM analysis confirmed the intercalation of the nanoclay particles as well as a reduction in their thickness. TEM images revealed that the size reduction happened through bending fracture followed by shear delamination of the fractured clay layers. On this basis, a structure of the physical network was proposed to be formed by sticking several nanoclay stacks inside a polymer chain and more involvement of polymer chains with the delaminated layers' ends. A dispersion model was used to quantify and interpret the dispersion status of nanoclay particles in the resin system.

Effect of Nanoclay on the Impact Properties of Glass Fiber-Reinforced Polymer Composites

This paper presents the influence of nanoclay and E-glass fibre reinforcement on impact response in polymer composite laminates under low velocity impact loading conditions. Glass fibre reinforced epoxy/nanoclay composites were prepared by hand lay-up techniques. Morphological studies using SEM and XRD revealed that fully intercalation of nanoclay in epoxy system. The result showed that the energy absorption became more efficient and also increased by 21% for CSM fibre composites at the velocity of 4.42 m/s, when 3% nanoclay was added. The fracture surface of the nanocomposites was analyzed using the Scanning electron microscopy (SEM) to characterize the damage progression.

Effect of polar interactions on the structure and rheology of EVA/Montmorillonite nanocomposites

In this study we utilized X-ray diffraction, transmission electron microscopy (TEM) and various types of simple shear flow experiments to investigate the effect of the polar-polar interaction between ethylene-vinyl acetate co-polymers (EVA) and organo-silicates on the nanoscale structures and rheological properties of their melt blends. The WAXS intensities and TEM micrographs demonstrate that the exfoliation and the intercalation of nanoclays respectively prevail in EVA/Cloisite 30B nanocomposites and EVA/Cloisite 15A nanocomposites, respectively. The master curves obtained from transient shear flow tests and their Arrhenius plot demonstrate the formation of side-tethered structure in the melt blends of EVA/ Cloisite 30B nanoclay. Finally, by means of performing a series of large-strain relaxation tests and regression techniques, the single integral Wagner model, that is expected to appropriately describe the rheometric experiment data of melt blends, was established, and then a comparison of the calculated and measured viscosity and first normal stress is presented.

Development of EPDM nanocomposites in presence of compatibiliser

The most significant factor, which prescribes the enhancement of properties in rubber by the incorporation of nanoclay, is its distribution in the rubber matrix. The study deals with the utilisation of epoxidised natural rubber (ENR) as a polar compatibiliser to achieve better dispersion of nanoclay in non‐polar polymer matrix. Epoxidised natural rubber–nanoclay composites (EC) were prepared by solution mixing. The obtained nanocomposites were incorporated in ethylene propylene diene terpolymer (EPDM) with sulphur as a curing agent. The morphological studies proved the intercalation of nanoclay in ENR, and further incorporation of EC in EPDM matrix leads to exfoliation of nanoclay. Curing study demonstrated faster scorch time, cure time and increase in maximum torque for the nanoclay loaded EPDM compounds compared to pure one. Dynamic mechanical thermal analysis showed increase in storage modulus and lesser damping characteristics for the compounds containing nanoclay loading in EPDM matrix followed by substantial improvement in the overall mechanical properties.

Starch esters with improved mechanical properties through melt compounding with nanoclays

AbstractBiobased nanocomposites were manufactured through the melt intercalation of nanoclays and starch esters synthesized at the Fraunhofer Institute for Applied Polymer Research (IAP) from high amylose starch. Starch acetates (SAs) and starch propionates (SPs) were tested in combination with glycerol triacetate (triacetin) as a plasticizer for concentrations up to 30 and 20 wt %, respectively, with different types of organomodified and unmodified montmorillonites (MMTs). The mechanical properties of injection‐molded test bars were determined by a tensile experiment giving the strength, modulus, and elongation of the composites. X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) were used to study clay dispersion and intercalation/exfoliation. Dynamic mechanical analysis was used to track the temperature dependence of the storage modulus and tan δ behavior of the starch/clay hybrid. Because they were the best performing compositions, SP with 5 wt % plasticizer and SA with 20 wt % plasticizer were filled with 5 wt % nanoclay. For SP, a certain increase in modulus was observed for all clays. However, the strength was practically unchanged, and the elongation decreased in most cases. One exception was found for the 2.5 wt % organomodified clay composition, where the elongation increased. For SA, the addition of 5 wt % nanoclay always increased the strength and modulus, in one case up to 60 and 75%, respectively. In the particular case with 5 wt % unmodified clay, the strength, modulus, and elongation increased by 30, 40, and 1000%, respectively. This was a dramatic improvement in the ductility of the material without losses in the strength and stiffness. XRD and TEM revealed the existence of exfoliated modified clay throughout the starch matrix, whereas for the unmodified case (with the exceptional increase in the elongation), no intercalation was observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Fouling release nanostructured coatings based on PDMS-polyurea segmented copolymers

The bulk and surface characteristics of a series of coatings based on PDMS-polyurea segmented copolymers were correlated to their fouling release performance. Incorporation of polyurea segments to PDMS backbone gives rise to phase separation with the extensively hydrogen bonded hard domains creating an interconnected network that imparts mechanical rigidity. Increasing the compositional complexity of the system by including fluorinated or POSS-functionalized chain extenders or through nanoclay intercalation, confers further thermomechanical improvements. In analogy to the bulk morphology, the surface topography also reflects the compositional complexity of the materials, displaying a wide range of motifs. Investigations on settlement and subsequent removal of Ulva sporelings on those nanostructured surfaces indicate that the work required to remove the microorganisms is significantly lower compared to coatings based on standard PDMS homopolymer. All in all, the series of materials considered in this study demonstrate advanced fouling release properties, while exhibiting superior mechanical properties and, thus, long term durability.

Mass transport studies of different additives in polyamide and exfoliated nanocomposite polyamide films for food industry

AbstractThe development of new food packaging films through the incorporation of nanoparticles, and the effect of the nanoparticles on the process of migration of the substances used in manufacturing the new films is expected to lead to an improvement in the shelf life of food and thus, consumer safety and health. In recent years, attention has focused on nanocomposites because these compounds often exhibit unexpected hybrid properties derived from synergistic reactions between nanoparticles and the polymeric matrix. The exfoliation of nanoclays in polyamide film provides a film with better barrier properties than that obtained through the intercalation of nanoclays. Migration of chemicals from food packaging into food may produce potential adverse health effects because of exposure to toxic compounds. The present study addressed the migration of caprolactam, 5‐Chloro‐2‐(2,4‐dichlorophenoxy)phenol (triclosan) and trans,trans‐1,4‐diphenyl‐1,3‐butadiene (DPBD) from polyamide and polyamide‐nanoclays to different types of food simulants. The values for limit of detection (LOD) obtained for caprolactam, triclosan and DPBD was 0.5 mg/L, 0.02 mg/L and 0.01 mg/L, respectively. Furthermore, instrumental precision was evaluated through repeatability injections, resulting in relative standard deviations lower than 3.08%. Diffusion coefficients were calculated according to a mathematical model based on Fick's Second Law, and the results were discussed in terms of the parameters that may have the greatest effect on migration. The presence of polymer nanoparticles was found to slow down the rate of migration of substances from the matrix polymer into the food up to six times. Copyright © 2009 John Wiley & Sons, Ltd.

Bio‐Based Nanocomposites of Cellulose Acetate and Nano‐Clay with Superior Mechanical Properties

AbstractSummary: Bio‐based nanocomposites were manufactured by melt intercalation of nanoclays and cellulose acetate (CA) with and without plasticizer. Glycerol triacetate (triacetin) as plasticizer up to 30 mass%, and different types of organo‐modified and unmodified montmorillonites (MMTs) as filler were used. X‐ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), were used to study clay dispersion, intercalation/exfoliation, and structure of the composites. XRD and TEM revealed very good dispersion and exfoliation of modified clay throughout the CA matrix. While for unmodified clay agglomeration and poor dispersion but an intercalated structure was observed. The mechanical properties of injection moulded test bars were determined by a tensile experiment giving tensile strength, Young's modulus and elongation at break. Adding plasticizer facilitated the processing and up to 20 mass%, increased the tensile strength, Young's modulus and elongation at break as well. Higher amount of plasticizer diminished the tensile properties except elongation showing a slight increase. In all plasticized composites, organo‐modified clay improved the tensile strength and at the same time, young's modulus and elongation almost remained constant. On the other hand, plasticized CA compounded with unmodified clay revealed lower properties. In a particular case, compounding of unplasticized CA with unmodified clay resulted in superior mechanical properties with a novel structure. So that, in optimum percentage –5 mass%‐ of unmodified clay, tensile strength and young's modulus increased significantly by 335% and 100%, to 178 MPa and 8.4 GPa, respectively. This is a dramatic improvement in strength and stiffness of CA. Adding organo‐modified clay resulted in a little improvement in tensile properties. SEM pictures of the optimum composite showed a core/shell structure with high orientation in the shell part. It is supposed that this behaviour is caused by the interaction between CA hydroxyl groups and free cations existing in the galleries of unmodified clay.

Development of nitrile butadiene rubber–nanoclay composites with epoxidized natural rubber as compatibilizer

The most important factor, which indicates the improvement of properties in rubber by nanoclay, is the distribution in the rubber matrix. The simple mixing of rubber and nanoclay will not exfoliate the filler in the rubbery matrix. Hence, some sort of compatibilizer like epoxidized natural rubber (ENR) can be utilized safely in exfoliating the nanoclay in the matrix polymer. Epoxidized natural rubber and organically modified nanoclay composites (EC) were prepared by solution mixing. The nanoclay employed in this study was Cloisite 20A. The obtained nanocomposites were incorporated in nitrile butadiene rubber (NBR) with sulphur as a curing agent. The morphological study showed the intercalation of nanoclay in ENR and further incorporation of EC in NBR matrix leads to exfoliation of nanoclay. Curing study demonstrated faster scorch time, cure time and increase in maximum torque for the EC incorporated NBR compounds compared to pure NBR. Dynamic mechanical thermal analysis showed increase in storage modulus and lesser damping characteristics for the compounds containing EC loading in NBR matrix. In addition, these particular compounds showed enhancement in overall mechanical properties, higher swelling resistance in oil and solvent and decrease in compression set due to higher reinforcing efficiency of nanoclay in the NBR matrix.

Filtration and Breakdown of Clay Clusters during Resin Transfer Molding of Nanoclay/Glass/Epoxy Composites

Dispersion of nanoclay clusters during resin transfer molding of nanoclay/glass/epoxy disks is investigated. In addition to a center-gated disk containing only 14% glass fibers, three nanocomposite disks are fabricated with the addition of 2, 5 or 10 wt% Cloisite® 25A nanoclay. The spatial distribution of nanoclay clusters along the radial axis of the nanocomposite disks are characterized at two length scales. Clusters larger than 1.5 μm are characterized by performing image analysis on the SEM micrographs whereas smaller nanoclay clusters are identified by wavelength dispersive spectrometry. Results obtained from image analysis indicate that nanoclay clusters are filtered out by as much as 50% in the flow direction by the glass fiber preforms. In addition, increasing nanoclay content led to higher filtration, suggesting that cluster formation is more prominent at higher nanoclay loadings. Cluster size distribution analyses revealed that the outer edges of the disks, on average, contain finer nanoclay particles. For instance, the outer edge of the nanocomposite with 2% clay contains 22% more small nanoclay clusters compared to center of the disk. Glass transition temperature, Tg, of four specimens obtained from each molded disks is characterized under oscillatory shear. Glass transition temperature of the samples are shown to increase with the nanoclay content, yielding a 40% higher Tg at 10% nanoclay loading compared to glass/epoxy composite without clay. Increasing glass transition temperature with increasing nanoclay content may be an indication of intercalation of nanoclay within the epoxy matrix.

Development of a polyamide nanocomposite for food industry: Morphological structure, processing, and properties

AbstractIn the last few years, nanocomposites have been a focus of attention for researchers because they frequently exhibit unexpected hybrid properties derived from synergistic reactions between nanoparticles and the polymeric matrix. However, few studies about the dispersion of inorganic clay minerals in polyamide films have been carried out to explain the process of exfoliation. The exfoliation of nanoclays in the polyamide film provides a film with better barrier properties than the intercalation of nanoclays. The present study addresses the analysis of experimental variables (pressure, temperature, processing time, feed position, etc.) involved in the production of a polyamide film with nanoparticles, in order to obtain a film with good exfoliation, barrier and mechanical properties. SEM, TEM and XRD were also evaluated as tools to determine the degree of exfoliation of nanoparticles. The technique used in production of the film, the screw employed and the mixing time were found to be of great importance in obtaining an intercalated or exfoliated final product. The variables involved in obtaining an exfoliated Cloisite 30B/polyamide film by a double screw extruder were optimized, and a film with reduced permeability to oxygen (1,000 times lower than the control film) wasobtained. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Nanoclay reinforced HDPE as a matrix for wood-plastic composites

This study was aimed at identifying the best approach of incorporating nanoclay into wood-plastic composites (WPCs) to enhance their mechanical properties. Two different methods of introducing nanoclays into HDPE-based WPCs were examined. The first method involved the reinforcement of HDPE matrix with nanoclay, which was then used as a matrix in the manufacture of the wood-plastic composites (melt blending process). The second method consisted of a direct addition of nanoclay into HDPE/wood-flour composites during conventional dry compounding (direct dry blending process). The mechanical properties of injection molded WPCs were characterized using flexural, tensile, and dynamic mechanical analysis tests. In addition, the effect of five different types of nanoclays on the mechanical properties of HDPE was examined to identify the most effective nanoclay type for wood-plastic composites. The degree of nanoclay intercalation in HDPE-based nanocomposites was characterized by means of X-ray diffraction method and transmission electron microscopy. The melt blending process, in which nanoclay/HDPE nanocomposite was used as matrix, appeared to be the best approach of incorporating nanoclay in WPCs. The experimental results indicated that the mechanical properties of HDPE/wood-flour composites could be significantly improved with an appropriate combination of the coupling agent content and nanoclay type in the composites.

A novel strategy for nanoclay exfoliation in thermoset polyimide nanocomposite systems

A novel method of nanoclay exfoliation in the synthesis of nanocomposites of PMR type thermoset resins was investigated. The method involves nanoclay intercalation by lower molecular weight PMR monomer prior to dispersion in primary, higher molecular weight PMR resin and resin curing to obtain the final composites. The resultant mechanical and thermal properties were evaluated as functions of clay type, degree of clay exfoliation, and clay intercalation strategies. It was found that sonication of clay at the time of intercalation by lower molecular weight PMR resin helps to achieve higher degree of exfoliation. In addition, clays obtained from ion exchange with a 50:50 mixture of N-[4(4-aminobenzyl)phenyl]-5-norborene-2,3-dicarboximide (APND), and dodecylamine (C12) showed better exfoliation than Cloisite ® 30B clay. The resultant nanocomposites show higher thermal stability and higher tensile modulus.

Effects of Processing Conditions on Nanoclay Dispersion in Starch‐Clay Nanocomposites

ABSTRACTWheat starch samples containing Cloisite Na+ and 30B nanoclays were extruded from a twin‐screw extruder. Moisture content, temperature, and screw speed were varied to determine their effect on nanoclay dispersion. X‐ray diffraction and transmission electron microscopy (TEM) were used to examine nanoclay intercalation and exfoliation. Moisture content had the largest effect on Cloisite Na+ dispersion, with the highest moisture sample containing exfoliated nanoclays. Meanwhile, temperature and screw speed had little effect on Cloisite Na+ dispersion. For Cloisite 30B samples, only an increase in temperature produced slight intercalation of nanoclays. This was due to the incompatibility of starch with the more hydrophobic Cloisite 30B. Also, Cloisite Na+ and 30B intercalation did not depend on specific mechanical energy. In addition, water absorbance tests indicated the Cloisite Na+ sample containing the most well‐dispersed nanoclays had the lowest water uptake.

Enhancement of Energy Absorption in Syntactic Foams by Nanoclay Incorporation for Sandwich Core Applications

Syntactic foams are closed pore foams fabricated by the mechanical mixing of hollow glass particles in a matrix resin. The present study deals with change in compressive properties of syntactic foams due to the incorporation of nano-sized clay (nanoclay) particles. A surface modified clay, Nanomer I.30E, has been used in the fabrication of specimens. Six different types of syntactic foams are fabricated and tested for compressive properties. Three types of hollow particles (microballoons) of glass having different densities are used for fabrication. Each type of microballoon is combined with 0.02 and 0.05 volume fraction of nanoclay, respectively. The combined volume fraction of microballoons and nanocparticles is 0.65 in all kinds of foams. Compressive properties of these samples are compared with those of syntactic foams without nanoclay particles. It is observed that partial intercalation of nanoclay has taken place in the specimens and remaining nanoclay particles are present in small clusters. Such microstructure leads to nearly the same strength with considerable enhancement in fracture strain. Hence, the toughness of the material, measured as the area under stress–strain curve, is found to increase by 80–200% for various kinds of foams tested in the study. Fracture features of syntactic foams with and without nanoclay are compared.