Organoclay Research Articles

Nanocomposites based on natural rubber, organoclay and nano-calcium carbonate: Study on the structure, cure behavior, static and dynamic-mechanical properties

In this work, natural rubber (NR) based nanocomposites, using different amounts (0, 5, 10 and 15 parts per hundred rubber, phr) of nano-calcium carbonate (nano-CaCO3) with and without organoclay (OC) are prepared by melt mixing process. The prepared samples are characterized, performing X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM), dynamic-mechanical thermal analysis (DMTA), swelling resistance in chemicals and tensile test. The tensile test results show that by the simultaneous using of 5phr OC and 10phr nano-CaCo3 the tensile strength is improved about 350%. The other tests such as XRD, FE-SEM, DMTA and swelling resistance tests as well as the theoretical investigation and calculating some thermodynamic parameters such as filler activity, activation enthalpy and Gibbs free energy reveal a considerable improvement of properties for the NR with OC and nano-CaCO3 in comparison to corresponding nanocomposites containing either one. The optimized sample in spite of having high elasticity exhibits high loss modulus which is very important in rubber product application.

Organoclay-reinforced dynamically vulcanized thermoplastic elastomers of polyamide-6/polyepichlorohydrin-co-ethylene oxide

Dynamically vulcanized thermoplastic elastomers (TPVs) based on polyamide-6 (PA-6) and poly (epichlorohydrin-co-ethylene oxide) (ECO) and their nanocomposites were prepared via melt-blending process. The unfilled and organoclay (OC)-filled TPVs were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry, thermal gravimetric analysis (TGA), and mechanical tests. XRD and TEM results showed that the OC particles were well exfoliated into the samples with high rubber content while both intercalated and exfoliated structures were found in the samples with low rubber content. The mechanical properties showed that ECO improved the elongation at break and the presence of OC increased the Young's modulus. Also, wide angle XRD analysis showed an increase in α-crystals of PA-6 with addition of ECO rubber. Moreover, it was found that by increasing OC content, crystallization temperature increased but the degree of crystallinity decreased. TGA showed that increasing ECO content decreased thermal stability of the samples, while the presence of OC did not have any considerable effect on the thermal stability. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Impact of salinity and dispersed oil on adsorption of dissolved aromatic hydrocarbons by activated carbon and organoclay

Adsorption capacity of phenol and naphthalene by powdered activated carbon (PAC), a commercial organoclay (OC) and a lab synthesized organoclay (BTMA) was studied using batch adsorption experiments under variable feed water quality conditions including single- and multi- solute conditions, fresh water, saline water and oily-and-saline water. Increasing salinity levels was found to reduce adsorption capacity of OC, likely due to destabilization, aggregation and subsequent removal of organoclay from the water column, but did not negatively impact adsorption capacity of PAC or BTMA. Increased dispersed oil concentrations were found to reduce the surface area of all adsorbents. This decreased the adsorption capacity of PAC for both phenol and naphthalene, and reduced BTMA adsorption of phenol, but did not negatively affect naphthalene removals by either organoclay. The presence of naphthalene as a co-solute significantly reduced phenol adsorption by PAC, but had no impact on organoclay adsorption. These results indicated that adsorption by PAC occurred via a surface adsorption mechanism, while organoclay adsorption occurred by hydrophobic or pi electron interactions. In general, PAC was more sensitive to changes in water quality than either of the organoclays evaluated in this study. However, PAC exhibited a higher adsorption capacity for phenol and naphthalene compared to both organoclays even in adverse water quality conditions.

A comparison between the effects of gamma radiation and sulfur cure system on the microstructure and crosslink network of (styrene butadiene rubber/ethylene propylene diene monomer) blends in presence of nanoclay

Abstract Rubber blends based on (styrene–butadiene rubber (SBR)/ethylene–propylene-diene monomer (EPDM)) with and without organoclay (OC) were prepared through a melt mixing process. The concentration ratio of the rubber phases (EPDM/SBR; 50/50 wt%) and the amount of the OC were kept constant. The samples were then vulcanized by means of gamma radiation using a Co-60 gamma source as well as sulfur cure system. The effect of absorbed dose on the formation of the crosslinks was confirmed by the Fourier transform infrared spectroscopy (FTIR). The effects of absorbed dose, sulfur cure system and OC on the gel content, and crosslink density were evaluated by the chemical tests. Applying the Charlesby–Pinner equation to estimate the radiation chemical yield, revealed that the use of OC in the blend caused 20% reduction in the degradation/crosslinking ratio. Employing the swelling test data, some thermodynamic parameters were determined. Using field emission scanning electron microscopy (FE-SEM) to investigate microstructure of the samples revealed a more homogeneous structure and also an increase in compatibility of the blend components in the sample cured by the irradiation in comparison to that cured by the sulfur curing system.

Organo-Clays As Sorbents of Hydrophobic Organic Contaminants: Sorptive Characteristics and Approaches to Enhancing Sorption Capacity

AbstractWhen clay minerals, notably smectites, intercalate organic cations, their interlayer surfaces change from hydrophilic to hydrophobic. The resultant intercalates, known as organo-clays (OCs), have a large affinity for hydrophobic organic contaminants (HOCs). Organo-clays are used as sorbents of HOCs in wastewater treatment and as sorptive barriers in landfill liners. The structural and sorptive characteristics of OCs with respect to HOCs have been studied extensively, and a large volume of literature has accumulated over the past few decades. The interactions of OCs with HOCs and the various approaches to improving the sorption capacity of OCs are reviewed here, with particular reference to the application of novel analytical techniques, such as molecular modeling, to characterizing the OC—HOC interaction.

Morphology and rheology of (styrene-butadiene rubber/acrylonitrile-butadiene rubber) blends filled with organoclay: The effect of nanoparticle localization

In this study, immiscible acrylonitrile butadiene rubber/styrene butadiene rubber (NBR/SBR) blends and their nanocomposites with cloisite 15A (C15A) and cloisite 30B (C30B) nanoparticles were prepared via a melt mixing method. The structure and morphology of the prepared samples were investigated by theoretical methods and by using equipment including X-Ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The experimental results proved that the C30B, the more hydrophilic organoclay (OC) tended to confine in the NBR, the more polar rubber phase, and in the interface whereas C15A, the less hydrophilic one was located at the SBR and interface. This was in agreement with the results obtained by the calculation of the wetting parameter. The EDS results showed that the average area of the NBR droplets in the SBR/NBR (80/20) blend decreased from 1.13 to 0.8 and 0.76μm2 in the presence of C30B and C15A, respectively. The use of epoxidized natural rubber (ENR) in conjunction with the OC caused more reduction of the NBR droplet size. Rheo-mechanical spectroscopy displayed the significant effect of OC localization on viscoelastic properties of the blends. Meanwhile, the rheological behavior of the blends was quantitatively similar to that predicted by Palierne's model extended to filled immiscible blends. This model was applied to obtain morphological and interfacial information for the SBR/NBR nanocomposite.

Time-dependent performance of soil mix technology stabilized/solidified contaminated site soils

This paper presents the strength and leaching performance of stabilized/solidified organic and inorganic contaminated site soil as a function of time and the effectiveness of modified clays applied in this project. Field trials of deep soil mixing application of stabilization/solidification (S/S) were performed at a site in Castleford in 2011. A number of binders and addictives were applied in this project including Portland cement (PC), ground granulated blastfurnace slag (GGBS), pulverised fuel ash (PFA), MgO and modified clays. Field trial samples were subjected to unconfined compressive strength (UCS), BS CN 12457 batch leaching test and the extraction of total organics at 28 days and 1.5 years after treatment. The results of UCS test show that the average strength values of mixes increased from 0–3250kPa at 28 days to 250–4250kPa at 1.5 years curing time. The BS EN 12457 leachate concentrations of all metals were well below their drinking water standard, except Ni in some mixes exceed its drinking water standard at 0.02mg/l, suggesting that due to varied nature of binders, not all of them have the same efficiency in treating contaminated soil. The average leachate concentrations of total organics were in the range of 20–160mg/l at 28 days after treatment and reduced to 18–140mg/l at 1.5 years. In addition, organo clay (OC)/inorgano–organo clay (IOC) slurries used in this field trial were found to have a negative effect on the strength development, but were very effective in immobilizing heavy metals. The study also illustrates that the surfactants used to modify bentonite in this field trail were not suitable for the major organic pollutants exist in the site soil in this project.

Impact of various amendments on immobilization and phytoavailability of nickel and zinc in a contaminated floodplain soil

The immobilization of toxic metals in soils using amendments is a cost-effective remediation technique for contaminated soils. Therefore, this study aimed to assess the efficiency of various amendments to immobilize nickel (Ni) and zinc (Zn) in soil and reduce their phytoavailability. A greenhouse pot experiment was established with a contaminated agricultural floodplain soil. The soil was treated with activated carbon (AC), bentonite (BE), biochar (BI), cement bypass kiln dust (CBD), chitosan (CH), coal fly ash (FA), limestone (LS), nano-hydroxyapatite (HA), organo-clay (OC), sugar beet factory lime (SBFL), and zeolite (Z) with an application rate of 1 % (0.2 % for HA) and cultivated by rapeseed (Brassica napus). After plant harvesting, the soil was analyzed for water-soluble and geochemical fractions of Ni and Zn. Additionally, both metals were analyzed in the aboveground biomass. Application of the amendments increased significantly the biomass production of rapeseed compared to the control (except for OC, HA, and FA). Water-soluble Ni and Zn decreased significantly after adding the amendments (except OC, Z, and CH). The SBFL, CBD, LS, BE, AC, and BI were most effective, resulting in a 58–99 and 56–96 % decrease in water-soluble Ni and Zn, respectively. The addition of SBFL, CBD, and LS leads to the highest decreasing rate of concentrations of Ni in plants (56–68 %) and Zn (40–49 %). The results demonstrate the high potential of CBD, SBFL, LS, BE, AC, and BI for the immobilization of Ni and Zn in contaminated floodplain soils.

有机粘土/聚醚砜/环氧树脂杂化纳米复合材料的制备和性能*

分别用溶剂法和熔融法成功制备了有机粘土/聚醚砜/环氧树脂杂化纳米复合材料,对其拉伸性能、断裂韧性、热性能和微观结构进行了研究。结果表明:两种杂化纳米复合材料的拉伸强度可达75 MPa以上,模量可达3.0 GPa以上,断裂韧性可达1.1 MPam1/2以上。观察到了聚醚砜和有机粘土对环氧树脂的协同增韧现象。聚醚砜/环氧树脂基体具有半互穿网络结构,有机粘土片层呈有序剥离形态。用溶剂法制备的杂化纳米复合材料样本的玻璃化转变温度(Tg)在170℃以上,用熔融法制备的样本的Tg在180℃以上。

Effect of organo-clay on properties and mechanical behavior of Fluorosilicone rubber

High performance Fluorosilicone rubber (FS)/organoclay (OC) nanocomposites have been prepared by a melt compounding process. The results of mechanical investigation revealed that Young’s modulus and hardness of FS rubber are improved with introduction of OCs while an inverse trend was observed for elongation at break and tensile strength. Eight constitutive models, Yeoh, Arruda-Boyce, Mooney-Rivilen, Neo-Hookean, Marlow, polynomial, Van der Waals, and Odgen were studied to investigate the stress-strain behavior of FS/OC nanocomposites. It was concluded that the ability of these models to predict the true behavior of the FS/OC samples directly depends on the amount of OC. Two modified Halpin-Tsai and inverse rule of mixtures theories were applied to evaluate the dependence of Young modulus of nanocomposites on volume fraction of OCs. The experimental data were employed for determining modified models parameters as well as for validating models. It was shown that, OCs can also play a fundamental role in controlling volume shrinkage of FS after cure. FS was proved that still retain its specific properties as well as the fuel and thermal resistance after introduction of OCs. Combination of these results verifies that incorporation of OCs can provide tailored mechanical properties without sacrificing fuel and thermal resistance of FS elastomers.

Modification in physical properties of organo clay filled polyurethane nanocomposites

Polyurethane (PU) have been prepared by using polyether polyol (jagropol oil) and 1,6-hexamethylene diisocyanate (HMDI) as a cross-linker. The organically modified montmorillonite clay (o-MMT) is well dispersed into urethane matrix by in-situ polymerization method. A series of PU/o-MMT nanocomposites have been prepared by varying amounts viz., 1, 3, 5 and 6 wt % of nanoclay. The mechanical properties such as tensile strength, percentage elongation at break and tensile modulus of the composites were experimentally determined. The swelling behavior of the composites has been studied in different organic solvents. It was noticed that the swelling data of the composites significantly depends on the solubility parameters of the solvents. Microcrystalline parameters such as, lattice strain (g in %), average number of unit cells (〈N〉) in direction perpendicular to Bragg plane, surface weighted crystal size (Ds) and interplanar distance (dhkl), were calculated from X-ray patterns. These parameters were computed using Exponential asymmetric column length distribution functions. Morphological features of cryofractured PU/o-MMT composites were also analyzed using scanning electron microscopy (SEM).

Pressure drop reduction of stable water-in-oil emulsions using organoclays

In this study, the influence of organoclays (OC) on the pressure drop of surfactant-stabilized water-in-oil (W/O) emulsions was studied. OC were tested as pressure loss reducing agents for stable W/O emulsions with 0.7 (concentrated) and 0.3 (diluted) water volume fractions. Pressure drop measurements were conducted in horizontal pipes with inside diameters (ID) of 0.0254-m and 0.0127-m. The results showed a significant reduction in the emulsion viscosity with the addition of OC and this effect was enhanced as the concentration increased. In addition, for the case of concentrated W/O emulsions, the addition of OC resulted in 25% reduction in the emulsion pressure drop in both test sections. For diluted W/O emulsion with only 0.3 water fraction, while no pressure drop reduction was observed in the laminar region, it was detected in the turbulent region and such effect was pronounced at high Reynolds numbers and high OC concentration. The observed results were explained in terms of emulsion dispersed phase droplet size. In the laminar regime, the friction factor for stable W/O emulsions was in a good agreement with single phase predictions. However, in the turbulent regime the friction factor for the multiphase system was below the predictions of single phase flow. OC proved to have a good potential as drag reducing agents by producing smaller and stable emulsion droplets hence suppressing the Reynolds' stresses.

Modification of bentonites with nonionic surfactants for use in organic-based drilling fluids

The use of organophilic bentonites as additives in organic-based drilling fluids has long been a subject of study, but few studies have focused on the modification of these clays with nonionic surfactants. The advantage of nonionic surfactants over ionic ones is that they improve the thermal and chemical properties of organoclays (OC), and are also more readily biodegradable. The work described here involves a study of bentonites modified by nonionic surfactants, aiming at their use as dispersants in the composition of organic-based drilling fluids. The organophilization process was analyzed by X-ray diffraction and thermogravimetry, and the interaction of organoclays with the solvent medium was assessed based on the swell index and the determination of the apparent viscosity of clay-containing dispersions. The results indicate an effective intercalation of the nonionic surfactants in organoclays, and the content of incorporated surfactants was also quantified. The swelling results demonstrate chemical compatibility between diesel and kerosene organic media and the organoclays produced. From the rheological standpoint, some of the organophilic clay samples present a potential for use as raw materials for additives in organic-based drilling fluids, despite being considered of poor quality when analyzed for water-based drilling fluids.

Flame retardancy and thermal stability of organic–inorganic hybrid resins based on polyhedral oligomeric silsesquioxanes and montmorillonite clay

Organic–inorganic hybrids were prepared by incorporation of two polyhedral oligomeric silsesquioxanes, trisilanolisobutyl POSS (TSP) and isobutylAluminum POMS (AlP), and an organoclay (OC), in an epoxy–amine system.Differential scanning calorimetry revealed the great catalytic power of AlP. OC also showed catalytic power, but to a lesser extent. The storage modulus increased with lower POSS contents, due to the nanoreinforcing effect of POSS core. At higher concentration, the modulus strongly decreases due to POSS aggregation. The glass transition temperature was barely affected by the POSS, whereas OC addition decreased it. POSS and OC supplied greater thermal stability in high temperature regions, and the char residue increased with filler concentration because silicon species are formed. POSS addition improved the flame retardancy because of a multilayered carbonaceous silicate structure formation. The presence of metal atoms in AlP composites might contribute to stabilization through secondary chemical reactions.

Synthesis of organoclays: A critical review and some unresolved issues

The synthesis of organoclays (OC) by intercalation of quaternary ammonium cation (QAC) into expanding clay minerals, notably montmorillonite (Mt), has attracted a great deal of attention during the past two decades. The OC have also found applications in the manufacture of clay polymer nanocomposites (CPN) and environmental remediation. Despite the wealth of information that exists on the formation and properties of OC, some problems remain to be resolved. The present contribution is an attempt at clarifying two outstanding issues, based on the literature and experimental data obtained by the authors over the past years. The first issue concerns the relationship between the cation exchange capacity (CEC) of the Mt and the basal spacing of the OC which, in turn, is dependent on the concentration and the nature of the added QAC. At a concentration less than 1 CEC, organo-Mt (OMt) formed using the QAC with a short alkyl chain length with nc<16 (e.g., dodecyl trimethylammonium) gives basal spacings of 1.4–1.6nm that are essentially independent of the CEC. However, for long-chain QAC with nc≥16 (e.g., hexadecyl trimethylammonium), the basal spacing varies with the QAC concentration. For Mt with a CEC of 80–90meq/100g, the basal spacing of the OC increases gradually with the CEC and shows a sudden (stepwise) increase to 3.2–3.8nm at a QAC concentration of 1.5 CEC and to 3.5–4.0nm at a concentration of 2.0 CEC. The second issue pertains to the “locking” effect in QAC- and silane-modified pillared interlayered clays (PILC) and Mt. For silylated Mt, the “locking” effect results from the covalent bonding of silane to two adjacent layers within a single clay mineral particle. The same mechanism can operate in silane-grafted PILC but in this case, the “locking” effect may primarily be ascribed to the pillaring of adjacent basal surfaces by metal hydr(oxides).

Critical Effect of Segmental Dynamics in Polybutadiene/Clay Nanocomposites Characterized by Solid State 1H NMR Spectroscopy

The segmental dynamics of rigid, intermediate, and mobile molecular components in carboxyl terminated polybutadiene (CTPB)/organo–clay (C18–clay) systems was characterized by fully refocused 1H NMR FID. In addition, 1H DQ NMR experiments allowed semiquantitative monitoring of changes in segmental dynamics near the interface. Both methods suggest a critical concentration of 60 wt % CTPB, indicating a saturation effect for the surface-adsorbed polymer. While the critical concentration value of a polymer/clay system can be measured in several ways, this is its first direct evidence at the molecular scale. The polymer–clay interaction is found to profoundly change with the removal of the CTPB end group or the organic modifier on the clay surface thus impacting the polymer segmental dynamics near the clay surface. In C18–clay by itself, with increasing temperature, the dynamic behavior of surface modifier changes from homogeneous to heterogeneous, on the basis of which the nonreversible exfoliation process of CTPB/clay nanocomposites could be explained at the molecular level. Based on the 1H NMR results, a tentative model was proposed to illustrate the evolution of the structure and segmental dynamics in CTPB/organo–clay nanocomposites.

Structure and properties research on montmorillonite modified by flame-retardant dendrimer

A novel approach to highly branched polymer chains for making advanced flame-retardant organoclays (OC) was presented. In this effort, a series of dendrimer based montmorillonite (Mt) were synthesized by tetrahydroxymethyl phosphonium chloride (THPC), N, N-dihydroxyl-3-aminomethyl propionate, and boric acid.Mt was first modified by THPC, and organic Mt (OMt) was obtained. Three generations of dendrimer modified organic clay minerals, DOMt-1, DOMt-2, and DOMt-3, were successfully prepared by OMt and the monomer prepared. Their chemical structures were characterized by FTIR, 1H NMR, elemental analysis, XRD, and TGA. These DOMts had expanded interlayer space and possessed good thermal stabilities. With an increase of generations, the thermal stability was not further enhanced for highly branched polymers due to the increasing content of CH bonds. These DOMts were terminated by boric acid, and a flame-retardant and dendrimer modified OMt (FR-DOMt) was successfully prepared. Experiments demonstrated that this FR-DOMt had better thermal stability and larger d-value due to steric hindering and thermal stability of the surfactant. The chemical structure and properties of FR-DOMt were valuable for its further applications.

Reinforcement and curing characteristics of organoclay filled natural rubber nanocomposites

Natural rubber (NR) - organoclay nanocomposites (NROCN) and NR-clay (un-modified montmorillonite clay) composites (NRCC) were prepared using different loading of OC/unmodified clay by melt compounding process using a laboratory scale internal mixer in view of investigating the organoclay (OC) effect on curing characteristics and reinforcing behaviour in NR compound formulations. X-ray diffraction analysis of NROCN’s revealed predominantly exfoliated OC structures within the NR nanocomposite materials, especially with a lower loading of OC where as NRCC’s showed MMT clay aggregates with larger clay stacks leading to conventional NR composite materials. Vulcanization characteristics of the clay filled NR compounds, especially processing safety, curing time and delta torque, have been interpreted with respect to the organic modifier in the OC and OC clay loading. NROCN vulcanizates have shown a significant enhancement in solid-state mechanical properties compared to those of NR gum and NRCC vulcanizates. Mechanical property data have been explained in terms of compatibility, degree of exfoliation and clay loading.

Bench-scale investigation of an integrated adsorption–coagulation–dissolved air flotation process for produced water treatment

In oil and gas extraction operations, water from the hydrocarbon reservoir is brought to the surface along with the oil or gas. This “produced water” contains organics which may be free, dispersed, or dissolved in the water. While certain dissolved compounds may contribute to environmental risk from produced water, current North American discharge regulations only address the dispersed fraction of oil and grease (29mg/L in the US, 30mg/L in Canada). The purpose of this research was to investigate, at bench scale, chemical coagulation with ferric chloride (FeCl3) and adsorption with organoclay (OC) in a completely stirred tank reactor (CSTR) configuration as pre-treatment for dissolved air flotation (DAF) for the removal of dissolved and dispersed oils from produced water. The integrated process was evaluated and compared to the individual processes of coagulation-DAF, adsorption-DAF and DAF without pre-treatment for the removal of dispersed oil, naphthalene and phenol from synthetic produced water. Concentrations of dispersed oil in clarified water were reduced, from an initial concentration of 100mg/L, to concentrations as low as 10±1.6mg/L after coagulation with FeCl3 (FeCl3-DAF), 15±1.2mg/L after adsorption with OC (OC-DAF), and 7±1.4mg/L after the integrated process (OC-FeCl3-DAF). From an initial naphthalene concentration of 1mg/L, both the adsorption (OC-DAF) and integrated process (OC-FeCl3) achieved clarified naphthalene concentrations of 0.11±0.01mg/L, representing a significant improvement over the 0.53±0.03mg/L achieved by coagulation treatment (FeCl3-DAF). However, none of the processes evaluated in this study were found to be effective for phenol removal.

Removal of Basic Dye from Aqueous Solutions Using a Novel Nanocomposite Hydrogel: N-Vinyl 2-Pyrrolidone/Itaconic Acid/Organo Clay

In this work, N-vinyl-2-pyrrolidone/itaconic acid/organo clay nanocomposite hydrogels were synthesized by free radical polymerization technique using different amounts of organo clay. Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy techniques were used for characterization of nanocomposite hydrogels and swelling, and mechanical properties of these hydrogels were investigated. Safranine-T adsorption capacities of nanocomposite hydrogels were investigated at different conditions such as pH, contact time, adsorbent dose and initial concentration of dye. The optimum pH value was found to be pH 6. According to the organo clay content, there are no significant differences in dye adsorption capacities of nanocomposite hydrogels until the clay content reaches 5 % wt. While the organo clay amount of nanocomposite hydrogels increases up to 10 % wt, dye adsorption capacities of these hydrogels significantly decrease. Adsorption processes of dye onto the nanocomposite hydrogels follow pseudo-second-order type adsorption kinetic. The equilibrium adsorption data have been evaluated using Freundlich and Langmuir Isotherm models. The results illustrated that the adsorption follows Langmuir isotherm.