Dispersion Of Sepiolite Research Articles

Impact of Increased Sonication-Induced Dispersion of Sepiolite on Its Interaction with Biological Macromolecules and Toxicity/Proliferation in Human Cells.

Sepiolite is a natural clay silicate that is widely used, including biomedical applications; notably sepiolite shows promising features for the transfer of biological macromolecules into mammalian cells. However, before its use, such an approach should address the efficiency of binding to biological macromolecules and cell toxicity. Because sepiolite spontaneously forms aggregates, its disaggregation can represent an important challenge for improving the suspension performance and the assembly with biological species. However, this can also influence the toxicity of sepiolite in mammalian cells. Here, a very pure commercial sepiolite (Pangel S9), which is present as a partially defibrillated clay mineral, is used to study the consequences of additional deagglomeration/dispersion through sonication. We analyzed the impact of extra sonication on the dispersion of sepiolite aggregates. Factors such as sonication time, sonicator power, and temperature are taken into account. With increasing sonication time, a decrease in aggregation is observed, as well as a decrease in the length of the nanofibers monitored by atomic force microscopy. Changes in the temperature and pH of the solution are also observed during the sonication process. Moreover, although the adsorption capacity of bovine serum albumin (BSA) protein on sepiolite is increased with sonication time, the DNA adsorption efficiency remains unaffected. Finally, sonication of sepiolite decreases the hemolytic activity in blood cells and the toxicity in two different human cell lines. These data show that extra sonication of deagglomerated sepiolite can further favor its interaction with some biomacromolecules (e.g., BSA), and, in parallel, decrease sepiolite toxicity in mammalian cells. Therefore, sonication represents an alluring procedure for future biomedical applications of sepiolite, even when using commercial defibrillated particles.

Poly(lactic acid)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer/sepiolite nanocomposites: Investigation of thermo‐mechanical and morphological properties

In this study, sepiolite nanoclay is used as reinforcing agent for poly(lactic acid) (PLA)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer (SEBS‐g‐MA) 90/10 (w/w) blend. Effects of sepiolite on thermal behavior, morphology, and thermomechanical properties of PLA/SEBS‐g‐MA blend were investigated. Differential scanning calorimetry results showed 7% improvement in crystallinity at 0.5 wt% of sepiolite. The nanocomposite exhibited approximately 36% increase in the tensile modulus and 17% increase in toughness as compared with the blend matrix at 0.5 and 2.5 wt% of sepiolite respectively. Field emission scanning electron microscopy and transmission electron microscopy images exhibited sepiolite‐induced morphological changes and dispersion of sepiolite in both PLA and SEBS‐g‐MA phases. Dynamic mechanical analysis and wide angle X‐ray diffraction present evidences in support of the reinforcing nature of sepiolite and phase interaction between the filler and the matrix. This study confirms that sepiolite can improve tensile modulus and toughness of PLA/SEBS‐g‐MA blend.

Steady-shear and viscoelastic properties of cellulose nanofibril\u2013nanoclay dispersions

We have investigated the steady-shear and viscoelastic properties of composite dispersions of cellulose nanofibrils (CNFs) with medium or high charge density and two different nanoclays, viz. rod-like sepiolite or plate-like bentonite. Aqueous dispersions of CNFs with medium charge density displayed significantly lower steady-state viscosity and storage modulus but higher gelation threshold compared with CNFs with high charge density. Dynamic light scattering (DLS) results showed that the apparent hydrodynamic radius of bentonite particles increased when CNFs were added, implying that CNFs adsorbed onto the amphoteric edges of the plate-like bentonite particles. The sepiolite network in CNF–sepiolite dispersions was relatively unaffected by addition of small amounts of CNFs, and DLS showed that the hydrodynamic radius of sepiolite did not change when CNFs were added. Addition of CNFs at concentrations above the gelation threshold resulted in drastic decrease of the steady-shear viscosity of the sepiolite dispersion, suggesting that the sepiolite network disintegrates and the rod-like clay particles are aligned also at low shear rate. The relative change in the rheological properties of the clay-based dispersions was always greater on addition of CNFs with high compared with medium charge density. This study provides insight into how the rheology of CNF–nanoclay dispersions depends on both the nanoclay morphology and the interactions between the nanoclay and nanocellulose particles, being of relevance to processing of nanocellulose–clay composites.

Morphological studies and thermo‐mechanical behavior of polypropylene/sepiolite nanocomposites

This article describes the effect of natural Sepiolite nanofibers on the properties of polypropylene (PP) in the absence/presence of compatibilizer (maleic anhydride grafted‐polypropylene (PP‐g‐MA)). For this purpose, PP/Sepiolite and PP/PP‐g‐MA/Sepiolite nanocomposites were prepared by melt blending using twin‐screw extruder. The morphology and dispersion of Sepiolite in PP composites characterized using scanning electron microscope (SEM) and transmission electron microscope (TEM) revealed that the dispersion of Sepiolite in PP matrix was better in the presence of PP‐g‐MA. Thermogravimetric analysis (TGA) was used to study the effect of Sepiolite on the thermal stability of PP in absence/presence of PP‐g‐MA. X‐ray diffraction (XRD) and differential scanning calorimetric (DSC) techniques were employed to assess the effect of Sepiolite on the crystallinity of PP matrix. Dynamic mechanical analysis (DMA) was used to evaluate the viscoelastic properties of PP/Sepiolite nanocomposites in solid state. Mechanical properties evaluated as per ASTM methods showed ∼65% increase in flexural modulus, 60%–70% increase in tensile modulus and 10%–20% increase in impact strength on addition of 10% Sepiolite in PP. Addition of compatibilizer has further improved the flexural modulus close to 85% when compared to neat PP without compromising other properties like impact strength and tensile strength. POLYM. COMPOS., 38:E285–E294, 2017. © 2015 Society of Plastics Engineers

In Situ Preparation of Resol/Sepiolite Nanocomposites

In this study, in situ modified phenol formaldehyde resins were prepared from clay (sepiolite) in the presence of base catalyst. Different clay contents (3 wt%, 5wt%, 8 wt%, 10 wt%, 15wt%, 20wt%, 30wt% and 50 wt%) were used to produce sepiolite modified resol nanocomposite resins (SEP-PFNCRs). SEP-PFNCRs were partially cured by heat and the effects of the curing process and the clay content in the resol resin were determined on the spectroscopic, thermal, and microscopic properties of the final products. The structures of the specimens were characterized by means of Fourier Transform Infrared (FTIR-ATR) spectroscopy. Thermal properties of the samples were determined with Thermogravimetric Analyzer (TGA). The dispersion of sepiolite in the resol nanocomposites were examined by X-ray Diffraction (XRD). The obtained samples were also characterized morphologically by Scanning Electron Microscope (SEM).

Effects of humic acid release from sepiolite on the interfacial and rheological properties of alkaline dispersions

Humic acid (HA) is a major extractable and soluble component of soil organic matter that can play an important role in the stability of environmental colloidal dispersions. This study suggests that HA content of sepiolite is one of the essential reasons for non-Newtonian behaviour of sepiolite dispersions in alkaline media. Releases of HA from sepiolite matrix dramatically changed their rheological properties (thixotropy, apparent viscosity and yield stress), and interestingly, the level of sepiolite surface hydrophobicity. Alkaline environments also increased the release of Mg2+ ions from the sepiolite matrix and, thus, caused to a stable complex formation with HA macromolecules. This colloidal solid phase was directly observed and imaged by atomic force microscopy (AFM) which revealed a spherical shape of complexes between Mg2+ ions and HA in the size range of 18–63±8nm at pH11.5.Alkaline environments also led to significant changes in the surface properties of sepiolite; after HA release, acid/base components of the surface free energy of sepiolite were determined as γS−/γS+=1.49 and defined as having a highly hydrophobic character like natural hydrophobic minerals, e.g. talc. The major soil organic matter component, HA, was also found to be responsible for the changes in the sepiolite surface hydrophilicity.

Mechanical, thermal and flammability properties of ethylene-vinyl acetate (EVA)/sepiolite nanocomposites

Ethylene-vinyl acetate (EVA)/sepiolite nanocomposites were prepared by melt blending in a twin screw extruder. The structural, morphological, thermal, flammability and mechanical properties of the EVA/sepiolite nanocomposites were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), thermal analysis, tensile properties and limiting oxygen index (LOI) measurements. X-ray diffraction analysis and FESEM revealed good dispersion of sepiolite in EVA matrix. The tensile strength of EVA/sepiolite increased by 21% and Young's modulus increased by 47% at 5 wt% and 7 wt% sepiolite content, respectively. The thermal stability and fire retardancy of the nanocomposites improved with sepiolite incorporation.

The regulation of sepiolite surface free energy and its impact on the thermal insulation property of coating.

Surface modification is used to regulate surface free energy of sepiolite with 3-glycidoxypropyltrimethoxysilanes (3-GPTMS), 3-methacryloxypropyltrimethoxysilanes (3-MAPTMS) and 3-mercaptopropyltrimethoxysilane (3-MPTMS). Through characterization by Fourier transform infrared spectroscopy, surface free energy, zeta potential and sedimentation measurements and infrared emissivity, it is found that the surface free energy of 3-MPTMS modified sepiolite decreases to 31.72 mJ/m2 and the percentage of polar component increases to 89.75%, thus leading to that the infrared emissivity of 3-MPTMS modified sepiolite increase to be higher than 0.8 and the dispersion of sepiolite has been improved. The excellent thermal insulation property of coating is prepared with 10% additive amount of 3-MPTMS modified sepiolite and the temperature difference between upper and lower box of modified sepiolite coatings is 10 degrees C which is higher than the untreated sepiolite.

Novel Sepiolite-based Poly(Amide-imide) Nanocomposites: Preparation and Properties

Novel sepiolite-based poly(amide-imide) nanocomposites were prepared by in-situ polymerization via polycondensation of a diamine containing amide groups with hexafluoropropane dianhydride. The process involved dispersion of sepiolite in poly(amic acid) solution followed by thermal imidization to get ultimate nanocomposites. The morphology, thermal and mechanical performances of nanocomposites with various sepiolite contents were studied. Nanoparticles were homogenously dispersed throughout the matrix with 50–65 nm size range. Due to such dispersion, poly(amide-imide)-sepiolite nanocomposite films exhibited improvements on the thermal-mechanical properties. The best results arose from favorable miscibility between polymer and sepiolite in the nanocomposites when 3 wt.% nanoparticles were introduced into poly(amide-imide) matrix.

Surface modification of sepiolite particles with polyurethane and polyvinyl alcohol

Sepiolite is a clay mineral that has many industrial applications due to its advantageous properties such as white color, low specific gravity, high absorption capacity, chemical composition and low thermal conductivity. In this study, the effect of the addition of polymers, polyvinyl-alcohol and polyurethane, on the rheological properties of the sepiolite dispersions have been investigated. The rheological parameters of clay suspensions can be used to examine particle–particle interactions. The polymers that have been added to the clay suspensions interact with clay particles, depending on their ionic or non-ionic character. Firstly, the sepiolite dispersions were characterized by the rheological properties, mineral structure and content. Then the effect of the polymers on the flow, structural, and surface properties of sepiolite dispersions was investigated by rheological, electrokinetical, and scanning electron microscopy (SEM) measurements. The measurements showed that polymer molecules bind on the surface of sepiolite particles and changed the flow properties of the dispersions as stable dispersions at some certain concentrations. It is also determined that PU polymer covered the surface of the sepiolite faster than PVA, but the coverage of the PVA was much more smoothly. The thermal properties of the sepiolite improved with PVA more than PU, as a result of the homogenous surface coverage.

Organomodification of sepiolite clay using bio-sourced surfactants: Compatibilization and dispersion into epoxy thermosets for properties enhancement

Abstract A new ammonium-based surfactant (PkH + ), synthesized from a 3-alkyl phenol glycidyl ether issued from renewable cashew nutshell liquid (CNSL), has been used to modify the surface of sepiolite clay. This surfactant is especially designed to enhance the compatibility of the needle-like clays with epoxy networks (e.g. DGEBA): ionic PkH + –sepiolite interactions are provided by the ammonium groups, and covalent grafting of DGEBA onto the surfactant is enabled by NH and OH reactive groups. MALDI-ToF-MS was used with success to evidence the grafting of DGEBA units onto the modified clay. Morphological analyses by SEM highlighted the promoted compatibilization and dispersion of sepiolite in DGEBA networks. The properties of the filled networks were characterized by DSC, DMA and evidenced a strong shift of 20 °C of the Tg of the network to higher temperatures and an enhancement of the storage modulus below the Tg. Interestingly, the thermal stability of the network was not affected by the modification of sepiolite by the ammonium. In conclusion, the intercalation of PkH + onto sepiolite subserves its compatibilization into epoxy networks with a remarkable thermal and thermomechanical properties improvement.

Influence of organic modifier characteristic on the mechanical properties of polyamide 6/organosepiolite nanocomposites

Polyamide 6 nanocomposites based on sepiolite needle-like clay were prepared via melt extrusion. The organic modifier nature effect (chemical structure and size) and the amount of nanofiller on the mechanical properties of the PA6/organo-sepiolite nanocomposites have been studied. Sepiolites were organo-modified with three different modifiers: dimethyl benzyl hydrogenated tallow quaternary ammonium (B2MTH), trimethyl hydrogenated tallow quaternary ammonium (3MTH) and N-Hydrogenated tallow-1,3-diaminopropane (DIAMIN T). The presence of organomodified sepiolite on the polymer matrix favoured the γ-phase of PA6. The best dispersion of sepiolite in the PA6 matrix was attained by using the smaller organomodifier. At higher nanofiller contents, the interaction between sepiolite and polymer matrix was favoured by the most linear organomodifier and the presence of amine groups (–NH2). In this case, thermomechanical properties of the nanocomposite leads to better properties when compared with the polymer matrix, i.e., increases in Elastic modulus and Head Deflection Temperature of 180% and 190% respectively were attained.

Thermal Stability and Degradation Kinetics of Poly(Methyl Methacrylate)/Sepiolite Nanocomposites by Direct Melt Compounding

Poly(methyl methacrylate) (PMMA) nanocomposites based on sepiolite modified with trimethyl hydrogenated tallow amine by an adsorption process were prepared by melt compounding using a corotating twin screw extruder. The morphology and dispersion of sepiolite in the PMMA were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and the activation energies were investigated by thermogravimetric analysis/differential thermogravimetric (TGA/DTG). The XRD and TEM results show that the sepiolite was dispersed homogeneously in the PMMA matrix at a nanometer scale. The TGA analysis revealed that the addition of sepiolite improved the thermal stability of PMMA. The apparent activation energies were calculated by the method of Flynn–Wall–Ozawa in nitrogen at four different heating rates, showing that sepiolite increased the apparent activation energies by about 20 kJ/mol within the degree of conversion (α) of 0.35–0.9, as compared with the reference PMMA sample.

Effect of dispersion of sepiolite in sepiolite-NBR composite on the tensile strength

The effect of dispersion of sepiolite in a sepiolite-NBR composite on the tensile strength of the composite was examined. Fibrous sepiolite was ultrasonically treated in distilled water with various types of dispersant. The ultrasonicated sepiolite was mixed with NBR latex to form a sepiolite-NBR complex. The tensile strength of the complex was examined to evaluate the degree of dispersion of sepiolite. The tensile strength results for the composites confirmed that a lower ultrasonication frequency produced a high strength in the composite. The tensile strength actually increased from 3 to 8MPa as a result of ultrasonication at 28kHz. To improve and stabilize the dispersion state, five kinds of dispersant were used. The addition of two dispersants in particular, ammonium polycarboxylate and amino alcohol polyphosphate, resulted in an increase of the strength from 8 to 15–16MPa. When the composites were heated at 450°C, the strengths of the composites produced with and without the dispersant were approximately 1.4–1.7 and 0.85MPa, respectively. Thus, the dispersant still affected the strength of the heated samples.

Adsorption and dielectric properties of poly(1-vinylimidazole) on sepiolite

The adsorption of poly(1-vinylimidazole) (PVI) onto sepiolite from aqueous solutions was investigated as a function of some parameters such as pH, ionic strength, and temperature. The adsorption of PVI was increased with increasing pH and with decreasing ionic strength and temperature. The Langmuir isotherm model fitted the isotherm data better than the Freundlich model. The electrophorotic mobility of sepiolite dispersions was measured at different PVI concentrations and pH. The thermodynamic parameters Gibbs free energy, enthalpy, and entropy were evaluated. The dimensionless separation factor (RL) revealed that sepiolite can be used for adsorption of PVI from aqueous solutions. The second-order kinetics equation best fitted the experimental data. Dielectric properties of sepiolite coated with PVI have been also investigated. The sample with adsorbed PVI at 25°C has the maximum the AC conductivity and the charge carriers can move easily in comparison with other samples. The real permittivities of the PVI-adsorbed samples are quite high in comparison with those of the pure polymer as a result of interface interactions.

Characterization and Some Properties of Poly(vinyl chloride)/Sepiolite Nanocomposites

AbstractPoly(vinyl chloride) (PVC)/sepiolite nanocomposites were prepared using PVC and natural, organo‐modified, acid–activated, and calcined sepiolite samples through the solution intercalation method. Thermogravimetric (TG) analysis, UV–vis spectrophotometry, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to determine the thermal stability, optical behavior, interactions, and morphology of samples, respectively. The dispersion of sepiolite in the PVC matrix was examined by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocomposites exhibited higher thermal stability than that of pure PVC. XRD and TEM results showed that sepiolite particles were dispersed in the nanoscaled PVC matrix. The UV–vis spectra showed that the transmission of nanocomposites increased with the sepiolite content and wavelength. The thermal degradation behavior of PVC was investigated by using TG analysis under nonisothermal conditions at different heating rates under a nitrogen atmosphere. The apparent activation energy of samples was determined by using the Kissinger method. The nanocomposite showed higher activation energy than that of pure PVC. The results showed that the thermal degradation of PVC was shifted toward higher temperatures with an increase in the amount of sepiolite. © 2011 Wiley Periodicals, Inc. Adv Polym Techn 32: E65–E82, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20271

Sepiolite-based epoxy nanocomposites: Relation between processing, rheology, and morphology

Rheology of sepiolite-based epoxy suspensions as well as morphology and dynamic mechanical properties of the corresponding nanocomposites are discussed in this paper. The influence of the type of sepiolite used, i.e. non-modified, aminosilane and glycidylsilane surface modified, and of the process developed to prepare the epoxy suspensions were investigated. Except for low amount of filler, a shear thinning behavior was observed in the others sepiolite-based epoxy suspensions. The interactions developed between the sepiolite and the epoxy matrix are responsible for the magnitude of the shear thinning effect and are related to the morphology of the nanocomposites. The best dispersion of sepiolite was achieved using either an emulsion process or a glycidyl functionalized sepiolite.

Preparation of polypropylene/sepiolite nanocomposites using supercritical CO 2 assisted mixing

Well dispersed polypropylene (PP)/sepiolite clay nanocomposites were prepared successfully using supercritical carbon dioxide (scCO 2) assisted mixing with and without the presence of maleic anhydride grafted polypropylene (PP-g-MA) as compatibilizer. The resulting morphology and polymorphism of nanocomposites were established using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations. The mechanical properties of the nanocomposites were investigated and compared with those obtained by a traditional melt compounding method. Our results showed that by using scCO 2 in the process, we were able to obtain better sepiolite dispersions and reduce breakage of sepiolite fibres. Consequently, a significant improvement in the yield stress was observed for the nanocomposites processed in scCO 2 compared to those processed by the traditional melt compounding. XRD data also indicated that the resulting nanocomposites had only α-phase crystallites of PP while the presence of sepiolite could also induce preferred orientation of these α-phase crystallites.

Characterization and properties of sepiolite/polyurethane nanocomposites

In situ polymerization method is employed to prepare sepiolite/polyurethane nanocomposite. The morphology and the dispersion of sepiolite in polyurethane have been characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and Fourier transform infrared spectroscopy. The results show the sepiolite is dispersed homogeneously in the polyurethane matrix at a nanometer scale. The tensile test shows that the tensile strength and elongation at break for the nanocomposites increase with the addition of sepiolite as compared to those of the pure polyurethane. The TGA analysis reveals that the addition of nanofillers results in the higher thermal stability.

Pharmaceutical grade phyllosilicate dispersions: the influence of shear history on floc structure

The effect of mixing conditions on the flow curves of some clay–water dispersions was studied. Two Spanish fibrous phyllosilicates (sepiolite from Vicálvaro and palygorskite from Turón) and a commercial bentonite (Bentopharm ©, UK) were selected as model clays. The disperse systems were made up using a rotor-stator mixer working at two different mixing rates (1000 and 8000 rpm), for periods of 1 and 10 min. Rheological measurements were taken and the corresponding flow curves obtained immediately after interposition and then after a period of 24 h under low shear caused by a roller apparatus. Aqueous sepiolite dispersions showed the highest viscosity and were easily interposed, whereas palygorskite dispersions were more difficult to obtain, resulting in low to medium viscosity gels. Bentonite dispersions provided medium viscosity systems, which greatly increased their viscosity after the low shear treatment (as a result of swelling), whereas the viscosity of the fibrous clays stayed at approximately the same values or even decreased. A linear relation was found between mixing energy and apparent viscosity in the bentonite systems, while apparent viscosity in the sepiolite samples was related to mixing power, with minor influence of mixing times. All the systems studied had thixotropic behaviour, changing from clearly positive to even negative thixotropy in some palygorskite systems. Finally, we studied the effect of drastic pH changes on the system structure. Results showed that rheological properties were highly sensitive to pH in the fibrous dispersions, but less sensitive behaviour was found in the laminar clay systems.