Montmorillonite Nanoparticles Research Articles

Hybrid Films Based on a Bridged Silsesquioxane Doped with Goethite and Montmorillonite Nanoparticles as Sorbents of Wastewater Contaminants

The synthesis and characterization of silsesquioxane (SSO) films with pendant dodecyl groups and doped with goethite (Gt) or montmorillonite (MMT) nanoparticles were carried out and the new materials tested as sorbents of diverse contaminants. The synthetic method used yielded SSO films with the inorganic substrates homogeneously distributed within the polymeric matrices. The new materials were characterized by SEM, FTIR, XRD, and DSC and tested to evaluate their capability for adsorbing metallic cations, organic dyes, and phosphate, frequent contaminants of industrial effluents. All films were found suitable for removing metallic cations. Results also showed that the SSO films undoped and doped with Gt are primarily apt for anionic compounds removal. Although the SSO films doped with MMT are capable of removing cationic contaminants from aqueous samples, the stiffness of the SSO matrix hinders MMT properties as an adsorbent. The possibility of dispersing nanoparticulate systems in the stable and chemically inert SSO matrices simplifies their application for contaminant removal, particularly because it makes the separation process of the absorbed pollutant from the treated medium easier.

Kinetics of the thermal degradation of poly(lactic acid) obtained by reactive extrusion: Influence of the addition of montmorillonite nanoparticles

A reactive extrusion-calendering process was used in order to manufacture sheets with a nominal thickness of 1 mm of poly(lactic acid) and its nanocomposite with 2.5% of an organo-modified montmorillonite. During processing, the properties of the melt were stabilized and enhanced by the addition of 0.5% of a styrene-acrylic multi-functional-epoxide oligomeric reactive agent. The general analytical equation has been used in order to evaluate the kinetic parameters of the thermal degradation of poly(lactic acid) obtained by reactive extrusion and its nanocomposite. Various empirical and theoretical solid-state mechanisms have been tested to elucidate the best kinetic model. In order to reach this goal, master plots have been constructed by means of standardized conversion functions. Given that it is not always easy to visualize the best accordance between experimental and theoretical values of standardized conversion functions, a new index has been developed to quantitatively discern the best mechanism. By doing that, it has been possible to determine the right activation energy of the thermal degradation. It has been demonstrated that the best theoretical mechanism was the random scission of macromolecular chains within the polymer matrix. This was also in accordance with an empirical kinetic model based on an autocatalytic kinetic model. The presence of montmorillonite nanoparticles has been beneficial and has enhanced the thermal stability of poly(lactic acid).

Study on crosslinked gelatin–montmorillonite nanoparticles for controlled drug delivery applications

Gelatin, because of its biodegradability and ecofriendly nature, has been the best choice for controlled release applications. Montmorillonite (MMT) clay shows a very important role in controlling drug delivery. Hence, an attempt was made in this work to prepare gelatin–MMT nanoparticles by desolvation method using acetone as precipitating agent, glutaraldehyde (GA) as crosslinking agent, and water as reaction media for controlled delivery of isoniazid, a drug for tuberculosis. Characterization of the MMT and isoniazid-loaded gelatin–MMT nanoparticles was carried out using Fourier transform infrared spectroscopy, X-ray diffraction study, scanning electron microscopy study, and transmission electron microscopy study. The effect of MMT on gelatin nanoparticles was evaluated in terms of water uptake studies, and subsequently to the release of isoniazid drug in buffer solution at pH 1.2 (gastric pH) and pH 7.4 (intestinal pH). Swelling experiment indicated that the gelatin nanoparticles were very sensitive to the pH environment. The release profile of drug was studied by a UV–Visible spectrophotometer. Cytotoxicity study revealed that MMT-containing nanoparticles showed less cytotoxicity than MMT-free nanoparticles.

Hybrid collagen-based hydrogels with embedded montmorillonite nanoparticles.

Montmorillonite nanoparticles have been physically incorporated within a crosslinked collagen/poly(N-isopropyl acrylamide) network in order to adjust the properties of the stimuli-responsive hybrid systems. The research underlines both the influence of hydrogel composition and nanoparticle type on hybrid hydrogel properties. The dispersion of the montmorillonite nanoparticles in polymeric matrix have been visualized by SEM, TEM and AFM techniques and quantitatively and qualitatively estimated using near infrared chemical imaging. The electrical charge of the nanoparticles influenced the polymeric chain arrangement and the pore size. The morphologies of the nanoparticulated layers are partially exfoliated or intercalated and uniformly dispersed through the polymeric semi-interpenetrated network based on collagen and poly(N-isopropyl acrylamide). The hybrid hydrogels exhibit pseudoplastic behavior and the addition of nanoparticles has resulted in the increase of the complex viscosity. The adhesion capacity was affected mainly by the presence of organically modified montmorillonites.

The impact of ultra-low amounts of amino-modified MMT on dynamics and properties of densely cross-linked cyanate ester resins.

Thermostable nanocomposites based on densely cross-linked cyanate ester resins (CER), derived from bisphenol E and doped by 0.01 to 5 wt. % amino-functionalized 2D montmorillonite (MMT) nanoparticles, were synthesized and characterized using Fourier transform infrared (FTIR), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), far-infrared (Far-IR), and creep rate spectroscopy (CRS) techniques. It was revealed that ultra-low additives, e.g., 0.025 to 0.1 wt. %, of amino-MMT nanolayers covalently embedded into СER network exerted an anomalously large impact on its dynamics and properties resulting, in particular, in some suppression of dynamics, increasing the onset of glass transition temperature by 30° to 40° and twofold rise of modulus in temperature range from 20°C to 200°C. Contrarily, the effects became negligibly small or even negative at increased amino-MMT contents, especially at 2 and 5 wt. %. That could be explained by TEM/EDXS data displaying predominance of individual amino-MMT nanolayers and their thin (2 to 3 nanolayers) stacks over more thick tactoids (5 to 10 nanolayers) and the large amino-MMT aggregates (100 to 500 nm in thickness) reversing the composite structure produced with increasing of amino-MMT content within CER matrix. The revealed effect of ultra-low amino-MMT content testifies in favor of the idea about the extraordinarily enhanced long-range action of the ‘constrained dynamics’ effect in the case of densely cross-linked polymer networks.PACS82.35.Np Nanoparticles in polymers; 81.05.Qk Reinforced polymers and polymer-based composites; 81.07.Pr Organic-inorganic hybrid nanostructures

Dodecenylsuccinic Anhydride Pickering Emulsion Stabilized by Montmorillonite Nanoparticles Modified with Sodium Fluoride

Processing convenience and paper-sizing flexibility frequently require the delivery of alkenylsuccinic anhydride oil as emulsion. The shelf life of the oil is achieved kinetically, in most cases via the addition of surfactants such as cationic starch or a synthetic polymer, which are the subject of increasing scrutiny with regard to their environmental impact. The modification of montmorillonite nanoparticle with sodium fluoride was found to decrease the interfacial tension between dodecenylsuccinic anhydride (DDSA) and aqueous dispersion and to change the wettability of montmorillonite, which benefits the preparation of DDSA-in-water emulsions with enhanced stability, small droplet size, and improved hydrolysis resistance. Adjusting the pH and particle concentration of aqueous solution effectively improved the stability of DDSA emulsion. Catastrophic phase inversion from w/o (water-in-oil) to o/w (oil-in-water) was investigated by monitoring the variation of emulsion conductivity with increasing oil volume fraction. Evidence of the transition from loose particle-film to compact particle shell upon introduction of salt was found, as predicted theoretically for charged particles adsorbed on interfaces. Particulate interfacial films built by SFMMT nanoparticles protected DDSA droplets from aggregation and formed a honeycomb structure. Salt in the DDSA emulsification process restrained the hydrolytic action of DDSA effectively and sustained the sizing performance of DDSA even 5 h after the emulsion preparation.

Biodegradable packaging and edible coating for fresh-cut fruits and vegetables

This work focuses on biodegradable packaging and edible coatings applied to fresh-cut fruits and vegetables and their effects on the product quality. Practical applications are mainly limited to the use of biodegradable materials that, however, do not allow full control of the product moisture loss. Better results can be achieved by the combined use of biodegradable packagings with edible coatings and recent research has shown that enrichment with silver montmorillonite nanoparticles may be a promising technique. However, the actual utilization of these materials is still limited, due to the high costs of the raw materials and the limited production.

Stimuli Responsive Matrices for Medical Applications

Different types of stimuli responsive polymers that respond with a property change to a variation in the environmental conditions are an attractive class of materials for advanced applications in biomedical or pharmaceutical fields. Three types of responsive biocompatible and biodegradable polymer matrices are presented as potential biomaterials for medical application as carriers for various drugs and tissue engineering substitutes. Hybrid hydrogels based on collagen/ N-isopropyl acrylamide containing montmorillonite nanoparticles are promising materials for tissue engineering and also as carriers for norfloxacin, a chemotherapeutic antibacterial agent. Semi-interpenetrated hydrogels based either on substituted anhydride modified collagen and 2-hydroxyethyl methacrylate or on alginate and poly (N-isopropylacrylamide) were tested as matrices for the controlled delivery of bisoprolol fumarate, an antihypertensive drug and respectively of ketoprofen, a non-steroidal anti-inflammatory drug.

Thermodynamic study of water sorption and water barrier properties of nanocomposite films based on brea gum

Water transport in edible films based on hydrophilic polymers is a complex phenomenon due to the strong interactions of sorbed water molecules with the polymeric structure. The effect of montmorillonite (Mt) nanoparticle incorporation into brea gum (BG) based films was studied through thermodynamic and phenomenological analyses. Moisture adsorption isotherms at three different temperatures of BG based films and BG/Mt nanocomposite films were obtained. Thermodynamic parameters showed an exothermic process that results less favourable when Mt is incorporated into the BG matrix, reducing the water uptake. Entropy change and net isosteric heat of adsorption showed a peak at monolayer water content, which is greater in composite films, indicating a more stable and ordered structure when Mt was added. Gibb's energy was indicative of process spontaneity and of the lower affinity to water composite films. Water vapour permeability depends on the tortuosity of the pathway formed by Mt nanoparticles and solubility of water molecules into the BG film matrix. Mt incorporation reduces the hydrophilic character of BG based films and thus their water vapour permeability.

Organically modified montmorillonite polymer nanocomposites for stereolithography building process

Novel photopolymerizable nanocomposite formulations, able to photopolymerize with a dual curing mechanism (cationic and radical), were developed, characterized and used in the stereolithography (SL) process for the construction of 3D objects with a very simple geometry. The influence of the presence of organically modified montmorillonite (OM) nanoparticles on the reactivity of the photopolymerizable liquid mixtures was firstly analyzed, as function of the amount of nanofiller, by photocalorimetric analysis (p‐DSC). The basal distance of OM before and after mixing with the photocurable formulation was characterized by X‐ray diffraction. Composites with higher content of OM show an intercalated structure. An exfoliated structure was instead observed in the composites with the lowest OM content, after photocuring in the SL apparatus. These results were also confirmed by the morphological analysis performed by SEM. The glass transition temperature of nanocomposites, photocured by stereolithography, was finally measured by TMA and DSC techniques, confirming that the photocurable formulation loaded with the lowest amount of OM presents improved properties than the unloaded formulation. Copyright © 2014 John Wiley & Sons, Ltd.

Radionuclide desorption kinetics on synthetic Zn/Ni-labeled montmorillonite nanoparticles

Sorption/desorption kinetics for selected radionuclides (99Tc(VII), 232Th(IV), 233U(VI), 237Np(V), 242Pu and 243Am(III)) under Grimsel (Switzerland) ground water conditions (pH 9.7 and ionic strength of ∼1mM) in the presence of synthetic Zn or Ni containing montmorillonite nanoparticles and granodiorite fracture filling material (FFM) from Grimsel were examined in batch studies. The structurally bound Zn or Ni in the octahedral sheet of the synthetic colloids rendered them suitable as colloid markers. Only a weak interaction of the montmorillonite colloids with the fracture filling material occurs over the experimental duration of 10,000h (∼13months). The tri- and tetravalent radionuclides are initially strongly associated with nanoparticles in contrast to 99Tc(VII), 233U(VI) and 237Np(V) which showed no sorption to the montmorillonite colloids. Radionuclide desorption of the nanoparticles followed by sorption to the fracture filling material is observed for 232Th(IV), 242Pu and 243Am(III). Based on the conceptual model that the driving force for the kinetically controlled radionuclide desorption from nanoparticles and subsequent association to the FFM is the excess in surface area offered by the FFM, the observed desorption kinetics are related to the colloid/FFM surface area ratio. The observed decrease in concentration of the redox sensitive elements 99Tc(VII), 233U(VI) and 237Np(V) may be explained by reduction to lower oxidation states in line with Eh-pH conditions prevailing in the experiments and thermodynamic considerations leading to (i) precipitation of a sparingly soluble phase, (ii) sorption to the fracture filling material, (iii) possible formation of eigencolloids and/or (iv) sorption to the montmorillonite colloids. Subsequent to the sorption/desorption kinetics study, an additional experiment was conducted investigating the potential remobilization of radionuclides/colloids attached to the FFM used in the sorption/desorption kinetic experiments by contacting this FFM with pure Grimsel groundwater for 7days. A positive correlation of 242Pu, 232Th(IV) and 237Np was observed with the Zn and Ni concentrations in the desorption experiments indicating a remobilization of sorbed montmorillonite colloids. The results of the study in hand highlight (i) the novel use of structural labeled colloids to decrease the uncertainties in the determination of nanoparticle attachment providing more confidence in the derived radionuclide desorption rates. Moreover, the data illustrate (ii) the importance of radionuclide colloid desorption to be considered in the analysis and application of colloid facilitated transport both in laboratory or in-situ experiments and numerical model simulations and (iii) a possible remobilization of sorbed colloids and associated radionuclides by desorption from the matrix material (FFM) under non-equilibrium conditions.

Preparation and characterization of nanocomposite of maleated poly(butylene adipate-co-terephthalate) with organoclay.

Nanocomposites of poly(butylene adipate-co-terephthalate) (PBAT) with montmorillonite (MMT) nanoparticles were prepared via melt blending. Natural MMT was modified by either octadecylamine (ODA) or dihexylamine (DHA). Neat PBAT was grafted with maleic anhydride via melt grafting process. Intercalation of the organoclay in the PBAT matrix was studied by X-ray diffraction (XRD). From the results of transmission electron microscope (TEM), the dispersion of ODA-modified MMT in the PBAT matrix was more homogeneous than that of neat MMT. The addition of organoclay can increase the cooling crystallization temperature of PBAT, as observed by differential scanning calorimetry (DSC). Furthermore, the results of thermogravimetric analyzer (TGA) showed that the addition of ODA-modified MMT can improve the thermal stability of PBAT nanocomposites. The tensile strength was little affected, while the Young's modulus was increased with the addition of nanoclays. The grafting of PBAT with MA resulted in improved interaction between polymer matrix and the silicate layer due to the formation of chemical/physical bonds, thus the dispersion of organoclays was enhanced. By grafting PBAT with MA, the enzymatic biodegradation of the nanocomposite was increased, while the photodegradation of PBAT was little affected. Furthermore, the transmission of water vapor was reduced by the addition of organically modified MMT.

Experimental and Mathematical Assessment of Migration from Multilayer Food Packaging Containing a Novel Clay/Polymer Nanocomposite

A novel clay/polymer composite film was prepared by applying a modified clay polymer suspension containing montmorillonite nanoparticles onto bi-axially oriented polypropylene films to form three-layer barrier film via lamination. The suitability of the film to be used as a food contact material was assessed with a focus on two-side migration into specified food simulants (water, 3 % acetic acid, 15 % ethanol, olive oil, grapeseed oil and coconut oil) under three different temperatures. It was found that migration levels increased with increasing contact time and temperature. Among the aqueous food simulants tested, the 3 % acetic acid solution demonstrated the highest migration levels, while the water was the least efficient migrating medium. Migration into fatty simulants was observed to be greater than those into aqueous solutions, but independent of their fatty acid composition. The results provided adequate guarantees for the developed film to be applied for food packaging materials. A numerical model based on Fick’s diffusion theory was developed to predict the extent of migration from the multilayer film at any time of exposure in aqueous simulants. Measurements of migration were combined with computer simulations to yield reliable estimates of the diffusion and partition coefficients in the system, which showed an Arrhenius behaviour. The model was solved using a finite element method, and the predicted results and experimental data agreed very well, indicating the rate-controlling steps of diffusion within the polymer in the migration process.

Spectral and photochemical properties of tetraphenylporphyrin tetrasulfonate supported on modified montmorillonite nanoparticles

A photocatalyst that effectively sensitizes the oxidation of 9,10-diphenylanthracene in toluene under irradiation with visible light has been prepared by the treatment of cationic surfactant-modified montmorillonite nanoparticles with a solution of meso-tetrakis(4-sulfonatophenyl)porphyrin. Reaction quantum yields and singlet oxygen generation probability have been determined. The shifts and intensity changes observed for the absorption bands of meso-tetrakis(4-sulfonatophenyl)porphyrin in the catalyst as compared with aqueous solutions are associated with solvation effects. The meso-tetrakis(4-sulfonatophenyl)porphyrin triplet state has been detected using the laser photolysis technique, and the rate constant of its quenching by oxygen on the surface of nanoparticles has been measured.

Gas transport properties in waterborne polymer nanocomposite coatings containing organomodified clays

Nanostructured composite coatings, consisting of phylosilicates embedded within polymer matrices, were prepared and characterized. Waterborne acrylic and polyurethane resins were employed as matrix, and hydrophilic or organically modified nanoparticles of montmorillonite as reinforcement. Emphasis in this article is put on the preparation of the coating. An overview of the major steps involved is presented. The choice of a suitable solvent for the preparation stage is based on the values of the solubility parameters of the constituents. The characterization techniques that are used include X-ray diffraction analysis, gas permeation measurements, and IR spectroscopy. The results highlight the significance of the selection of appropriate ingredients and the knowledge of the interactions between the clay particles, the organic matrix, and the solvents used for the preparation of the coating.

Novel microencapsulated liquid fire extinguishers with a nanomodified microcapsule shell

A new process has been developed for the microencapsulation of ecologically safe and highly effective fire extinguishers, including the perfluoroketone Novec 1230 (whose Russian analog is Khladon PFK-49), which has enhanced stability for use as a basic functional component in fire-extinguishing polymer materials. When Freons are microencapsulated via common methods, an intense loss of the liquid core of the microcapsule in the course of drying and storage via diffusion through the shell occurs. The stabilization effect was attained through modification of the microcapsule shell material via addition (at the stage of shell formation) of nanoparticles of the mineral layered filler montmorillonite. The processes of thermal degradation of the resulting microcapsules have been studied and a substantial improvement in stability (reduced permeability of the shell) and, hence, the possibility of their application has been shown. Laboratory fire tests of materials were performed, and the high effectiveness of fire extinguishment by microencapsulated perfluoroketone and the fire-extinguishing polymer material has been demonstrated.

Evaluating the stability of colloidal gas aphrons in the presence of montmorillonite nanoparticles

To block rock pores in aphron drilling operation, colloidal gas aphrons (CGAs) stability is a key factor to minimize formation damage. Although the synergistic stabilization of aqueous foam by solid particles and surfactants has been extensively studied, there are few references for synergistic stabilization of CGAs. In this experimental study, stability of CGAs has been investigated in the presence of nanoparticles. CGAs dispersion were generated by stirring at 7000rpm for 4min in the presence of the nanoclay (Na-Montmorillonite). An anionic surfactant, sodium dodecyl sulfate (SDS), and also a non-ionic surfactant, nonyl phenol ethoxylate (NPE20) were used. The experimental macroscopic findings from the drainage curve observations were correlated to the microscopic behavior of CGAs. A novel analysis of drainage curve was introduced to examine synergistic effect of nanoclay on the CGA dispersion stability. This work concludes that nanoparticles influence the stability of CGAs dispersion and also nanoclays reduce the critical micelle concentration (CMC) in a surfactant solution.

Anti-graffiti nanocomposite materials for surface protection of a very porous stone

The preservation of stone substrates from defacement induced by graffiti represents a very challenging task, which can be faced by applying suitable protective agents on the surface. Although different anti-graffiti materials have been developed, it is often found that their effectiveness is unsatisfactory, most of all when applied on very porous stones, e.g. Lecce stone. The aim of this work was to study the anti-graffiti behaviour of new nanocomposite materials obtained by dispersing montmorillonite nanoparticles (layered aluminosilicates with a high-aspect ratio) into a fluorinated polymer matrix (a fluorinated polyurethane based on perfluoropolyether blocks). Polymeric structure was modified by inducing a cross-linking process, in order to produce a durable anti-graffiti coating with enhanced barrier properties. Several composites were prepared using a naturally occurring and an organically modified montmorillonite clay (1, 3, and 5 % w/w concentrations). Materials were applied on Lecce stone specimens, and then their treated surfaces were soiled by a black ink permanent marker or by a black acrylic spray paint. Several repeated staining/cleaning cycles were performed in order to evaluate anti-graffiti effectiveness. Colorimetric measurements were selected to assess the anti-graffiti performance. It was found that the presence of 3 % w/w organically modified montmorillonite in the polymer coating is enough to induce a durable anti-graffiti effect when the stone surface is stained by acrylic paint. Less promising results are obtained when staining by permanent marker is considered as all the investigated treatments afford a reasonable protection from ink only for the first staining/cleaning cycle.

Adsorption and molecular dynamics of low-molecular substances on modified montmorillonite nanoparticles

The effect of the structure of stable nitroxyl radicals on their adsorption from organic solvents on montmorillonite modified with cationic surfactants is examined. The influence of the nature and content of the modifier and solvent, as well as additional modification with cationic dyes, on the adsorption is considered. The kinetic parameters of the adsorption of decane, toluene, and ethanol from the gas phase are determined. The spin probe method is used to determine the phase state and distribution of adsorbed additives, as well as the influence of an additional adsorption of hydrocarbons on the molecular dynamics at the surface of nanoparticles of montmorillonite and nanopigments based on cationic dyes.

Ultraviolet paints based on nanopigments for printing on textile materials

The effect of the modifier structure and content, as well as the dye structure, on the absorption on montmorillonite nanoparticles has been studied. The discovered dependencies have been used for obtaining nanopigments with high content of the coloring component based on cationic, direct, acid, active or disperse dyes. The effect of the coloring component on photopolymerization of the oligomer/monomer binder is estimated and the optimum compositions of ultraviolet (UV) paints with nanopigments are determined. It has been shown that developed UV paints possess higher light sensitivity compared with conventional organic pigments, and allow a dyed material with increased resistance to rubbing and tensile strength to be obtaining.