Types Of Organoclays Research Articles

Preparation and characterization of tapioca starch–poly(lactic acid) nanocomposite foams by melt intercalation based on clay type

Abstract Tapioca starch (TS), poly(lactic acid) (PLA), and four different organoclays (Cloisite 10A, Cloisite 25A, Cloisite 93A and Cloisite 15A) were used to produce nanocomposite foams by melt-intercalation. Structural, thermal, physical and mechanical properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and an Instron universal testing machine, respectively. The first XRD peaks for all four nanocomposite foams, were observed to shift to lower angles, indicating that intercalation occurred. The extent of intercalation depended on the type of organoclay and was exhibited in the sequence of Cloisite 10A > 25A > 93A > 15A. Glass transition temperatures ( T g ), melting temperatures ( T m ) and transition enthalpies (Δ H ) of the foams were investigated by DSC. Radial expansion ratio (RER), unit density, bulk spring index (BSI), bulk compressibility, Young's modulus ( E ), water absorption index (WAI) and water solubility index (WSI) were influenced ( p

Vapor Adsorption of Volatile Organic Compounds Using Organically Modified Clay

Organically modified clay was used to adsorb volatile organic compounds from a gaseous phase. The organoclay was prepared by adsorbing hexadecyltrimethylammonium (HDTMA) on the surface of montmorillonite particles. Two volatile organic compounds (VOCs), chlorobenzene and trichloroethylene, were adsorbed to the organoclay using a fixed adsorption bed. The adsorption was carried out at various inlet concentrations of gaseous VOCs in a carrier gas (nitrogen). The adsorption behavior of VOCs was investigated using natural clay and two types of organoclays, which had different HDTMA loadings. Adsorption breakthrough curves were obtained, and the adsorption data were modeled with two adsorption isotherms. Desorption of VOCs was also conducted using pure nitrogen, and the desorption profiles were fitted with two different theoretical models. It was found that the organoclay possesses significant adsorption capacity towards VOCs and the uptake depends on the degree of HDTMA loading on clay surface.

Preparation and Chracterization of Nanocomposites of Polyamide 6/Brazilian Clay with Different Organic Modifiers

Nanocomposites of PA6 / organoclay at different concentration were prepared via melt intercalation method using a corotating twin screw extruder. The composites were prepared with Brazilian clay that was treated with different modifiers based on quaternary ammonium salts to obtain three types of organoclays. After extrusion the mixtures were injection molded into specimens that were tested to obtain the properties of tensile strength, notched izod impact and heat deflection temperature. The structure and morphology of the nanocomposites were characterized by x-rays diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the modifier “dodigen” which promoted the intermediate expansion of the bentonite clay within the three salts used for the modification of the clay affects more significantly the mechanical properties, HDT and morphology of the polyamide 6 due to the higher level of exfoliation observed in these systems compared to the others modifiers. The improvement of the properties was correlated to the level of exfoliation/intercalation obtained which depends on the process technique used, surface treatment of the Brazilian clays with organic salts and interaction between polymer and clay.

Impact modified polyamide‐6/organoclay nanocomposites: Processing and characterization

AbstractThe effects of melt state compounding of ethylene‐butyl acrylate‐maleic anhydride (E‐BA‐MAH) terpolymer and/or three types of organoclays (Cloisite® 15A, 25A, and 30B) on thermal and mechanical properties and morphology of polyamide‐6 are investigated. E‐BA‐MAH formed spherical domains in the materials to which it is added, and increased the impact strength, whereas the organoclays decreased the impact strength. In general, the organoclays increased the tensile strength (except for Cloisite 15A), Young's modulus and elongation at break, but the addition of E‐BA‐MAH had the opposite effect. XRD patterns showed that the interlayer spacing for the organoclays Cloisite 25A and Cloisite 30B increased in both polyamide‐6/organoclay binary nanocomposites and in polyamide‐6/organoclay/impact modifier ternary systems. TEM analysis showed that exfoliated‐intercalated nanocomposites were formed. The crystallinities of polyamide‐6/organoclay nanocomposites were in general lower than that of polyamide‐6 (except for Cloisite 15A). In ternary nanocomposites, crystallinities generally were lower than those of polyamide‐6/organoclay nanocomposites. Cloisite 15A containing ternary nanocomposites had higher tensile and impact strengths and Young's modulus than the ternary nanocomposites prepared with Cloisite 25A and Cloisite 30B, owing to its surface hydrophobicity and compatibility with the impact modifier. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers

On polyamide 6-montmorillonite nanocomposites obtained by in-situ polymerization

AbstractNanocomposites based on polyamide 6 (PA6) and montmorillonite-type (MMT) commercial clays, either unmodified or organically modified, were prepared by in-situ polymerization of ε-caprolactam (CL). The above materials were characterized in detail by a number of experimental techniques, including transmission electron microscopy (TEM), wide angle X-ray diffraction (WAXD), infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The formation of nanostructured systems was checked not only for the commonly used ω-aminoacid-modified clay, but also for other types of organoclays. In general, a correlation was found between nanoscopic swelling of the clay in molten CL, measured by X-ray diffraction, and level of clay dispersion in PA6. Specifically, with the most swellable clays, completely exfoliated nanocomposites were obtained. However, also layered silicates modified by compatibilizers having carboxy groups, because of the active role of latter in CL polymerization, formed delaminated nanocomposites despite their low degree of swelling in CL monomer. Both molecular mass and crystallinity of the polyamide matrix were found to be strongly influenced by the presence of specific layered silicates. In particular, some characterization techniques (WAXD, FTIR) have evidenced a close relationship between the MMT used and PA6 crystal structure. Namely, PA6 γ-form is promoted by clay with compatibilizer bearing the carboxy group, which is able to induce the polymer to be tethered on the silicate layers, thus provoking conditions of restricted mobility to occur.

Interfacial interaction in EVA‐carbon nanotube and EVA‐clay nanocomposites

AbstractProper filler‐matrix compatibility is a key factor in view of obtaining nanocomposites with well‐dispersed nanofillers displaying enhanced properties. In this respect, polymer‐filler interaction can be improved by a proper combination of matrix and nanofiller polarities. This is explored for matrices ranging from nonpolar high density poly(ethylene) to ethylene‐vinyl acetate (EVA) copolymers with varying vinyl acetate contents, in combination with several types of organoclay or carbon nanotubes. A novel in situ characterization methodology using modulated temperature differential scanning calorimetry is presented to evaluate the matrix‐filler interaction. During quasi‐isothermal crystallization of the matrix, an “excess” contribution is observed in the recorded heat capacity signal because of reversible melting and crystallization. Its magnitude considerably decreases upon addition of nanofiller in case of strong interfacial interaction, whereas the influence is moderate in case of a less interacting matrix‐filler combination. It is suggested that the “excess heat capacity” can be used to quantify the segmental mobility of polymer chains in the vicinity of the nanofiller. Hence it provides valuable information on the strength of interaction, governed by the physical and chemical nature of matrix and filler. Heating experiments subsequent to quasi‐isothermal crystallization point at a certain degree of molecular ordering, responsible for crystal nucleation in EVA copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1291–1302, 2007

Thermal degradation of commercially available organoclays studied by TGA–FTIR

Thermogravimetry coupled to Fourier transform infrared spectroscopy (TGA/FTIR) has been used to study the thermal decomposition products evolved during the degradation of several commercially available organoclays (Cloisites™ Na +, 10A, 15A, 20A, 25A, 93A and 30B). It was found that the decomposition pattern of the organoclays was different for each sample: Cloisite™ 10A shows three well-defined degradation stages, Cloisite™ 30B only two stages and the Cloisite™ 93A only one weight loss; Cloisites™ 15A, 20A and 25A exhibited a more complex behavior showing one main stage and a shoulder. It was also observed that the onset of the decomposition was different for each type of organoclay, being Cloisite™ 10A the lowest (160 °C) and Cloisite™ 93A the highest (212 °C). FTIR analysis of the evolved products from their non-oxidative thermal degradation showed the release of water, aldehydes, carboxylic acids, aliphatic compounds and, in some cases, aromatic compounds and CO 2. It is suggested that the degradation of both tallow residue and unexchanged surfactant explain the presence of some products evolved during degradation of organoclays.

Morphology/behaviour relationship of nanocomposites based on natural rubber/epoxidized natural rubber blends

In order to analyze the effect of an epoxidized natural rubber (ENR) and filler treatment on the morphology and behavior of natural rubber (NR) nanocomposites, blends of these polymers have been prepared. The nature and extent of the clay dispersions in the filled samples were evaluated by X-ray diffraction. In the presence of ENR, an exfoliated structure was obtained which suggests that enough rubbery polymer was incorporated into the interlayer spacing. The effect of clay in rubber compounds was analyzed through rheological, mechanical and swelling characterization. A sensible improvement in the nanocomposite properties was observed by the addition of organoclay. It has been deduced that the properties of the compounds strongly depend on the extent of the silicate nanolayers dispersion into the rubber matrices as well as on the organoclay type and elastomer compatibility.

Barrier and Mechanical Properties of Poly(caprolactone)/organoclay Nanocomposites

AbstractIn this study, biodegradable poly(caprolactone) (PCL) hybrids with two types of organoclays: Cloisite 30B (30B) and Cloisite 93A (93A) have been prepared by melt mixing and their barrier performance to air permeation and mechanical properties were investigated. The hybrids of PCL/30B were found to be nanocomposites resulted from the strong interaction between organic modifier of 30B and PCL and those of PCL/93A were microcomposites. The barrier performance of PCL/30B nanocomposite film to air permeation was much more improved than pure PCL and PCL/93A microcomposites at low organoclay concentration. With the increase of organoclay content the permeability coefficient was also increased that could attributed to the extra tortuous pathway for gas permeation caused by organoclay exfoliation. The barrier behaviour of PCL/30B nanocomposites could be approximately described by a theoretical model developed for composites. The mechanical properties measurements showed that the reinforcement of organoclay 30B in nanocomposites is more significant than 93A in microcomposites. Both tensile modulus and tensile strength were increased in PCL/30B nanocomposites even at at low amount of organoclay without much loss of strain at break as compared to pure PCL. The significant improvements in both barrier and mechanical properties in PCL nanocomposites could be attributed to the fine dispersion state of organoclay 30B platelets in PCL matrix and the strong interaction between organic modifier of 30B and matrix molecules.

Thermal and combustion behaviour of layered silicate–epoxy nanocomposites

The present research looks at the thermal properties of epoxy–clay nanocomposites synthesised by in situ polymerisation of a prepolymer (diglycidyl ether of bisphenol-A) crosslinked with methyl tetrahydrophthalic anhydride. The inorganic phase was montmorillonite, exchanged with alkylammonium ions in order to give organophilic properties to the phyllosilicate. The morphology of epoxy–montmorillonite nanocomposites examined by X-ray diffraction and transmission electron microscopy shows that mixed delamination or intercalation or microdispersion can occur depending on type of organoclay. Thermogravimetric analysis shows that in nanocomposites the epoxy matrix is sheltered from the action of oxygen. Cone calorimeter tests show that the rate of heat release in the nanocomposite combustion is strongly reduced.

Controlling the Deintercalation in Hydrogenated Nitrile Rubber (HNBR)/Organo‐Montmorillonite Nanocomposites by Curing with Peroxide

AbstractSummary: The effect of peroxide vulcanization on organoclay dispersion in hydrogenated nitrile rubber (HNBR)/organo‐montmorillonite (organo‐MMT) nanocomposites was investigated. Three types of organoclays were tested, one containing a primary amine and two bearing quaternary intercalants. In contrast to sulfur vulcanization, which in combination with primary amine intercalants produced a confined/deintercalated clay structure, the peroxide curing yielded well‐ordered intercalated nanocomposites. The tensile mechanical performance and oxygen permeability of the HNBR nanocomposites were determined.Oxygen permeability coefficient ratio for the different HNBR films tested at 0 and 60% relative humidity (i.e., dry and wet conditions, respectively).magnified imageOxygen permeability coefficient ratio for the different HNBR films tested at 0 and 60% relative humidity (i.e., dry and wet conditions, respectively).

Melt‐Intercalated Starch Acetate Nanocomposite Foams as Affected by Type of Organoclay

ABSTRACTStarch acetate nanocomposite foams with four organoclays (Cloisite 30B, 10A, 25A, and 20A) were prepared by melt‐intercalation methods. The structural properties, thermal behaviors, and mechanical properties were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry analyses (TGA), and Instron universal testing machine. XRD results indicated that the intercalation of starch acetate into the nanoclay layers occurred for all four clays. The extent of intercalation depended on the type of organoclay and was exhibited in the sequence of Cloisite 30B >10A >25A >20A. SEM results indicated a decrease in cell size in the starch acetate foam matrix with the addition of nanoclay. Glass transition temperature (Tg) and onset temperatures of thermal degradation increased with the addition of organoclay into the starch acetate matrix. The incorporation of organoclays decreased significantly the compressibilities of starch acetate nanocomposites and did not substantially affect their spring indices.

Epoxy-organoclay nanocomposites: morphology, moisture absorption behavior and thermo-mechanical properties

The morphology and moisture barrier characteristics are studied of epoxy-based nanocomposites reinforced with layered silicates. Two different types of organoclay, including the quaternary alkylamine modified montmorillonite (KH-MT) and the octadecylamine modified montmorillonite (I30P), were studied. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate that the I30P system exhibited a large increase in interlayer d -spacing from 3.39 mm to over 8 nm during the curing process, whereas the KH-MT system showed negligible changes in reflection angle and d -spacing, with the final interlayer distance of 3.39 nm after cure. The moisture absorption behaviour was different for different organoclays: the moisture absorption rate was similar for the neat polymer and the KH-MT system, which could be fitted to Fick's second law. The moisture absorption rate of the I30P system was much lower than the two systems, which was predicted using a non-Fickian model based on the ID Langmuirian solution. The deviation from the Fickian diffusion for the latter system is associated with exfoliated morphology and more uniform dispersion of clay particles, which altered the diffusion path of water molecules in the nanocomposite. The moisture diffusivity of nanocomposites in general decreased with increasing clay content, the reduction being more pronounced for the I30P system. The normalized permeability also showed a systematic degradation with increasing clay content, which agrees well with the prediction based on the tortuous path model.

Moisture barrier characteristics of organoclay–epoxy nanocomposites

The moisture diffusion and barrier characteristics of epoxy-based nanocomposites containing organoclay are investigated. The effects of different types of organoclay modified with different compatibilizers, including a quaternary alkylamine-modified montmorillonite (KH-MT), a quaternary ammonium-modified montmorillonite (Cloisite 20A) and an octadecylamine-modified montmorillonite (I30P), on moisture barrier and thermomechanical properties are specifically studied. The moisture absorption and diffusion behaviours were different depending on the type of organoclay: the moisture absorption rates of the Cloisite and I30P systems were much lower with associated lower diffusivity than the KH-MT system or the neat epoxy, due to the higher interlayer distance and more uniform distribution of organoclays, which in turn allowed a longer diffusion path of water molecules in the nanocomposite. The moisture diffusivity of nanocomposites decreased with increasing clay content for all organoclays. The corresponding moisture permeability was lower in the order of nanocomposites containing I30P, Cloisite and KH-MT organoclays. The moisture permeability showed a systematic decrease with increasing clay content, which agrees well with the prediction based on the simple tortuous path model. Increase in effective penetration path due to the very large aspect ratio of the silicate layers was responsible for the reduced moisture permeability. The glass transition temperature was much higher for the I30P nanocomposite than the neat epoxy resin, whether dry or wet condition. It decreased linearly with increasing moisture content. The CTE decreased with increasing clay content for all conditions studied.

Nanocomposites formed from linear low density polyethylene and organoclays

Polyethylene-clay nanocomposites were prepared by melt compounding various combinations of a maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA), a linear low density polyethylene (LLDPE), and two organoclays. The two types of organoclay were selected to show the effect of the number of alkyl groups attached to the nitrogen of the organic modifier on exfoliation and improvement of mechanical properties. Nanocomposites derived from the organoclay having two alkyl tails, M2(HT)2, exhibited better dispersion and improvement of mechanical properties than nanocomposites based on the organoclay having one alkyl tail M3(HT)1. This result is the opposite of what is observed for nylon-6 nanocomposites. In addition, the rheological properties and gas permeability of the nanocomposites derived from the organoclay having two alkyl tails, M2(HT)2 were investigated. Both melt viscosity and melt tension (melt strength) increased with increased content of clay (MMT) and LLDPE-g-MA. Gas permeability was decreased by the addition of MMT.

Sorption and detoxification of toxic compounds by a bifunctional organoclay.

Organoclays are excellent sorbents for nonionic contaminants and therefore may have many environmental applications. A major limitation on the use of organoclays is that the contaminant merely changes its location from one environmental compartment to another while still remaining intact. In this study, a new type of organoclay, termed a bifunctional organoclay, has been prepared. It is able not only to sorb organophosphate pesticides, but also to catalyze their hydrolysis, and thereby detoxify them. The bifunctional organoclay prepared in this study is based on sodium montmorillonite, in which the inorganic counter ions are replaced by N-decyl-N,N-dimethyl-N-(2-aminoethyl) ammonium (DDMAEA). The detoxifying capacity of this organoclay for two organophosphate pesticides, methyl parathion [O,O-dimethyl O-(p-nitrophenyl) thionophosphate] and tetrachlorvinphos [2-chloro-1-(2,4,5-trichlorophenyl)ethenyl dimethyl phosphate], was demonstrated. It was shown that although the sorption of these pesticides on the bifunctional organoclay is very similar to that on N-decyl-N,N,N-trimethyl ammonium (DTMA) organoclay (the corresponding nonbifunctional organoclay), the hydrolysis of these pesticides is substantially enhanced only by the bifunctional organoclay. The half-life for the hydrolysis of the investigated pesticides in the presence of the bifunctional organoclay is about 12 times less than for their spontaneous hydrolysis, and the enhancement is even more pronounced relative to the hydrolysis of these pesticides in the presence of the DTMA organoclay (which actually inhibits their hydrolysis). Based on kinetic measurements, the pK(a) of the ethylamino group of the bifunctional organoclay was estimated to be around 9.0. It is postulated that the catalytic effect of the bifunctional organoclay can be attributed to a nucleophilic attack of the unprotonated ethylamino group of the organoclay on the organophosphate ester.

Sorption and biodegradation of 2,4-dichlorophenol in the presence of organoclays

The influence of sorption on the biodegradation of 2,4-dichlorophenol (DCP) by Ralstonia eutropha was investigated using organoclays. The aim was to examine the suitability of organoclays combined with biodegradation in remediation techniques. Two types of organoclays were used: a dodecyltrimethylammonium montmorillonite, where 89% of the former sodium ions were exchanged by the cationic surfactant (C 12-MM), and a dioctadecyldimethylammonium montmorillonite complex (35% exchange of the sodium-ions) (2C 18-MM). The organoclays showed high sorption affinity to DCP resulting in the intercalation of DCP into the interlayers of the organoclay. The sorption processes were reversible and completed within minutes. Neither organoclay was inhibitory to R. eutropha degrading fructose. This was different with DCP as sole energy and carbon source. In the presence of DCP C 12-MM led to a decrease in cell numbers caused by a coupled effect of DCP and small amounts of free C 12 in solution. This was not observed with 2C 18-MM, as the concentration of 2C 18 in solution was lower because of the lesser degree of exchange (35% compared to 89%). The addition of 2C 18-MM enabled complete biodegradation of DCP in initially toxic DCP concentration ranges. Adsorption lowered the DCP concentration to a non-toxic level. Because the sorption process was reversible, DCP was desorbed when R. eutropha reduced the DCP concentration in the liquid phase by biodegradation. The whole amount of DCP—dissolved and initially adsorbed—was degraded as confirmed by oxygen consumption and cell concentration measurements. Organoclays can be very helpful tools in remediation when the exchanged amount of surfactant remains low. They even allow bioremediation under toxic circumstances, as was shown with 2C 18-MM.

Preparation and characterization of PBT nanocomposites compounded with different montmorillonites

AbstractBecause of their superior mechanical and thermal properties, light weight, and favorable cost/performance ratio, nanocomposite materials appear to be suitable replacements for metals and alloys in many industrial applications in fields such as automotive, structural plastics, electronics, packaging, and so on (1). The technological relevance of this large‐scale market for polymers is evidenced by the numerous patents issued over the last few years, even though only few applications have entered the market. Polymer‐clay nanocomposite systems were successfully prepared by melt compounding using several thermoplastic matrices (polyamides, polyolefins, etc.), but few data are reported in the scientific literature on polyester‐based nanocomposites (2). Because of the high commercial relevance of polyesters, we have investigated the effect of organoclay inclusion on the structure and properties of these hybrid systems. In particular, we have studied the relationships between processing conditions, hybrid composition (organoclay type and content), nanoscale morphology and properties of poly(butylene terephthalate) (PBT) nanocomposites based upon several commercial organo‐modified montmorillonites at different weight percentages. The melt compounding was performed using a twin‐screw extruder, at extrusion rates of 90 or 150 rpm. Polym. Eng. Sci. 44:1012–1018, 2004. © 2004 Society of Plastics Engineers.

Preparation and properties of polyimides having highly flexible linkages and their nanocomposites with organoclays

A highly flexible polyimide (PI) was synthesized successfully from ethylene glycol bis(anhydrotrimellitate) (TMEG) and 1,3-bis(4-aminophenoxy)benzene (TPER) for its application in electronics. To enhance the thermal stability and mechanical properties of this novel PI, we prepared PI nanocomposite films using nanoparticles of clays that had been treated with organic intercalating agents (organoclays). We used two types of organoclays: montmorillonite (MMT) treated with hexadecylamine (C16) and MMT treated with dimethyl dihydrogenated tallow quaternary ammonium (15A). PI/organoclay hybrid films were obtained by first preparing poly(amic acid) (PAA)/organoclay films and then converting the PAA to polyimide by thermal conversion. PAA was characterized by FT-IR and1HNMR spectroscopy and the conversion of PAA to PI was confirmed by FT-IR spectroscopy. We analyzed the dispersion of the organoclays in the PI film by X-ray diffraction. The thermal stability and mechanical properties of the hybrid films were also investigated.

Effect of heat treatment on the microstructural change of syndiotactic polystyrene/poly(styrene- co-vinyloxazolin)/clay nanocomposite

The fabrication of a syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process using poly(styrene- co-vinyloxazolin) (OPS), i.e. melt intercalation of OPS into organoclay followed by blending with sPS. The effects of several parameters, including type of organoclay and mixing temperature on the microstructure of the nanocomposite were investigated through X-ray diffraction patterns and rheological properties. The microstructure of the nanocomposite mainly depended on the arrangement type of the organic modifiers in the clay gallery. Using organoclays having lateral a bilayer arrangement exfoliated structure was obtained, whereas intercalated structure were obtained when organoclay with a paraffinic monolayer arrangement was employed in our sPS/OPS/organoclay system. In this work, a simple heat treatment on a previously prepared OPS/organoclay nanocomposite induced microstructural evolution with a favorable direction from intercalation to exfoliation. This phenomenon is attributed to a strong interaction between OPS and the clay surfaces, which is revealed by plateau behavior of the storage modulus in rheological properties. When heat is applied to the OPS/organoclay, the OPS chains and clay layers move together by promoted thermal motion of OPS chains, which results in disordering of stacked clay layers and exfoliation.