Talc Nanoparticles Research Articles

Investigation of calcite flotation by green natural hydrophobic talc nanoparticles as collectors, and the adverse influence of nanoparticle aggregates

Hydrophobic talc nanoparticles (T-NPs) were used as natural solid collectors to study calcite flotation in a modified Hallimond flotation tube to optimize process conditions. The results demonstrated that the calcite surface hydrophobicity and resulting floatability significantly changed with variations in the concentration of T-NPs. It was found that by increasing T-NPs amount in the range of 0.4–1.2 kg/ton, calcite flotation recovery increased. Experiments results also revealed that by increasing T-NPs concentration over 1.2 kg/ton, flotation recovery drastically decreased, which was an indication of the formation of suspended T-NPs aggregates, because of their great tendency to aggregate due to agitation. Owing to greater hydrophobicity and floatation kinetic rate of suspended aggregates than calcite surface that covered by T-NPs, they attaching to bubbles quickly and easily, thereby they will have an adverse influence on calcite floatability. Therefore, 1.2 kg/ton of T-NPs was the optimum concentration of nano collector for process recovery. The results of this study clearly showed the promising potential of natural nano particles as an environment friendly collector in froth flotation.

Exploration of Talc nanoparticles to enhance the performance of Lithium grease

The maiden effort to explore the potential of nanoparticles (NPs) of Talc to improve the tribo-performance of Li-based grease is reported. A series of greases, including NPs of Talc in various amounts (1, 2, 3, and 4 wt%), was developed. It was evaluated for the rheological, thermal and tribological viz. antiwear (AW), anti-friction (AF) and extreme-pressure (EP) characteristics. The highest tribological performance improvement was obtained at an optimum dosage of 2 wt% with an enhancement in AW and EP performance by 47% and 79%, respectively. The wear mechanisms are discussed based on various surface characterization techniques. Talc nano-grease proved more efficient than its micro-counterpart at 2 wt% on comparison of AW and EP by 43% and 17% respectively.

Novel application of graphite-talc hybrid nanoparticle enriched cutting fluid in turning operation

In this study, the influence of hybrid nanocutting fluid (both graphite and talc nanoparticles dispersed in a base fluid) in turning of Titanium alloy grade 5. The hybrid nanocutting fluid was developed by the blending of graphite and talc nanoparticles in a constant volumetric proportion (50:50) in pure coconut oil as a base fluid. The prepared hybrid nanocutting fluid has been investigated for its tribological behaviour using a pin-on-disc machine. The Gray relational analysis (GRA) is applied as a conservative approach in the optimization of process variables of Titanium alloy with multiple performance characteristics. The turning performance of the hybrid nanocutting fluid is compared with that of pure coconut oil in terms of cutting force and surface roughness. From the Gray relational grade analysis, it is obtained that the feed rate has a larger influence on responses as compared to cutting speed and nanoparticle concentration as well. By the application of hybrid nanocutting fluid, it is obtained a significant reduction in cutting force and surface roughness compared to pure coconut oil by 21.19 % and 18.9 %, respectively.

Improved self-healing performance of polymeric nanocomposites reinforced with talc nanoparticles (TNPs) and urea-formaldehyde microcapsules (UFMCs)

The present work reports the self-healing performance of the epoxy based polymeric nanocomposite coatings containing different concentrations (1 and 3 wt%) of talc nanoparticles (TNPs) modified with sodium nitrate (NaNO3), and a fixed amount (5 wt%) of urea-formaldehyde microcapsules (UFMCs) encapsulated with linseed oil (LO). The polymeric nanocomposites were developed, coated on polished steel substrates, and their structural, thermal, and self-healing characteristics were investigated using various techniques. The successful loading (~wt 10%) of NaNO3 into TNPs, which can be ascribed to the involvement of physio-chemical adsorption mechanism, is validated and proceeds without altering the TNPs parent lamellae structure. The performed tests elucidated that the self-release of the corrosion inhibitor (NaNO3) from TNPs is sensitive to the pH of the solution and immersion time. In addition, the release of the linseed oil (self-healing agent) from UFMCs in response to the external damage was found to be a time-dependent process. The superior self-healing and corrosion inhibition performance of the protective polymeric nanocomposites coatings containing 3 wt% TNPs and UFMCs/LO are proven using the electrochemical impedance spectroscopy (EIS) studies. A careful selection of smart carriers, inhibitor, and self-healing agent compatible with polymeric matrix has enabled to attain decent self-healing and convincing corrosion inhibition efficiency of 99.9% and 99.5%, respectively, for polymeric nanocomposites coatings containing 3 and 1 wt% TNPs, making them attractive for many industrial applications.

Flotation Behavior of Malachite Using Hydrophobic Talc Nanoparticles as Collectors

In this study, the flotation behavior of malachite was investigated using hydrophobic talc nanoparticles (TNs) as collectors. To improve the floatability of TN-deposited malachite, various experimental parameters were systematically investigated. We found that the floatability sharply increased as the size of the TNs decreased. The floatability of malachite was enhanced in the presence of smaller TNs, since higher amounts of smaller TNs were deposited on the surface of the malachite, thus rendering the surface more hydrophobic. Moreover, the floatability of the TN-deposited malachite increased as the pH decreased, likely due to the more favorable interaction between TNs and malachite by means of electrostatic attraction. Furthermore, the floatability became more enhanced as the TN concentration increased, likely associated with increases in the amount of TNs deposited on the surface of the malachite, thus enhancing the floatability by altering the hydrophobicity of the surface. Our findings suggest that the application of natural hydrophobic TNs as collectors in malachite flotation should be introduced as a new concept.

Crystalline morphology of thermoplastic starch/talc nanocomposites induced by thermal processing

A structural study about the changes induced by plasticization of native corn starch was carried out in this work. The influence of talc nanoparticles presence during starch thermal processing was also evaluated. Macroscopic observation of the granules appearance evolution during melt-mixing and thermo-compression was supported by a theoretical description related to these processing methods. Melt-mixing induced a polymorphic transformation from A- to Vh-type and a reduction in the degree of crystallinity. Homogenous appearance of the plasticized starch was in accordance to the disruption of granules integrity, evidenced by SEM. This observation agreed to the distinctive XRD pattern of plasticized starch from unprocessed granules. Talc incorporation did not require the adjustment of processing parameters in order to obtain a homogenous thermoplastic material, with an adequate particles distribution within the matrix. Regardless talc presence, plasticized starch presented a Vh-type crystalline structure. Thermo-compression led to particles alignment promoted by talc laminar morphology.

Pro-Degradant Effect of Talc Nanoparticles on Polypropylene Films

Fil: Linares, Paula Belen. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Bahia Blanca. Planta Piloto de Ingenieria Quimica. Universidad Nacional del Sur. Planta Piloto de Ingenieria Quimica; Argentina

Lemon essential oil desorption from polypropylene/talc nanocomposite films

A phenomenological analysis on desorption mechanism of lemon essential oil in semicrystalline polymer nanocomposites is performed. Films were made of polypropylene and talc nanoparticles obtained by blown extrusion were used as a case study due to the high complexity of sorption phenomena in such systems containing a semicrystalline polymer and nucleating particles. In this sense, a systematic analysis combining both morphological effects and intrinsic properties of each component was considered. Talc characteristics, e.g., morphology, surface chemistry, oil absorption properties, mean particle size and its distribution, and impurity presence, were considered in desorption analysis. Regarding semicrystalline matrix, morphological and crystalline changes induced by talc nanoparticles and processing were included in this study. Desorption of lemon essential oil from nanocomposite films with different talc concentrations (0, 1, and 5 wt%) which have distinctive and well characterized morphologies was evaluated through gravimetric and thermogravimetric analysis. Results show that polypropylene film has a desorption rate higher than nanocomposites containing 5 wt%, but lower than those with 1 wt% talc. This behavior is a consequence of the global crystallinity configuration changes produced by nanoparticle concentration and film obtaining process. It is revealed that simplified and conventional approaches that consider tortuosity as unique effect of particle presence in nanocomposite mass transport do not allow to comprehend the desorption mechanism involved in a complex system such as the semicrystalline polymer nanocomposites. The present study gives additional insight into the complex mechanism involved in desorption of strongly swelling oil in nanocomposite films based on semicrystalline polymers and mineral nucleating particles.

Blown nanocomposite films from polypropylene and talc. Influence of talc nanoparticles on biaxial properties

Blown films based on polypropylene (PP) and talc nanoparticles (0, 1, 3 and 5wt%) were obtained at pilot scale. Good nanoparticles dispersion and distribution was achieved without thermooxidative degradation. Nanocomposite films presented a higher crystalline degree than PP ones due to the contribution of both talc particles, acting as PP nucleating agents, and process crystallization induction. Mechanical properties were determined along machine and transverse direction (MD and TD, respectively) revealing that all films were elastic, tough, ductile and capable to form neck, but they presented higher elongation at break in MD than in TD. Results were interpreted in terms of changes in biaxial crystallization induced either by particles or by process, following a systematic experimental analysis. The issues were closely related to the development of blown nanocomposites films as materials to be employed in the packaging market, being the obtained results directly applicable to the industry.

Processing–properties–applications relationship of nanocomposites based on thermoplastic corn starch and talc

Films based on thermoplastic corn starch (TPS) and talc nanoparticles were developed by melt mixing and thermo‐compression. Films structure, optical and barrier properties, as well as thermal stability and water sorption behavior were studied. TPS structure resulted homogeneous and smooth. Talc laminar morphology and thermo‐compression induced particle preferential orientation within the matrix. Good particle distribution and talc‐TPS adhesion were evidenced. Nanometric thickness of mineral particles allowed obtaining translucent composite films, without significant color variation of TPS films. Talc addition at concentrations higher than 3% w/w led to an improvement on TPS barrier properties against water vapor and oxygen. It was also demonstrated that talc decreased water uptake of TPS films exposed to ambient conditions with relative humidity higher than 40%. In conclusion, films based on TPS and talc nanoparticles could be an alternative to develop biodegradable packages for food products with suitable final properties. POLYM. COMPOS., 39:1331–1338, 2018. © 2016 Society of Plastics Engineers

Novel application of talc nanoparticles as collector in flotation

The objective of this work is to study the application of natural hydrophobic talc nanoparticle as a new class of solid flotation collector.

Thermoplastic starch/talc bionanocomposites. Influence of particle morphology on final properties

This work analyzed the effect of talc morphology on structural characteristics and final properties of thermoplastic corn starch (TPS). In this sense, composite films based on TPS containing talc nanoparticles were obtained by melt-mixing and thermo-compression. Talc samples with different morphological characteristics (platy-microcrystalline and blocky-macrocrystalline), derived from their formation process, were used. Platy and blocky morphology was distinguished by Scanning Electron Microscopy performed on composites films. Microcrystalline morphology induced smaller TPS crystallites than macrocrystalline one, indirectly evidenced by X-Ray Diffraction and Differential Scanning Calorimetry. Crystalline character of talc particles also affected visible and UV barrier capacity of TPS films. Blocky morphology of mineral filler led to the highest reduction of TPS water vapor permeation. Both talc samples acted as matrix reinforcement agents. However, macrocrystalline particles induced the major changes on elastic modulus and tensile strength, without affecting films ductility.

Comparative study of the structural and rheological properties of PA6 and PA12 based synthetic talc nanocomposites

The structural and rheological properties of synthetic talc/polyamide (ST/PA) composites, elaborated by simultaneous melt mixing of a PA6 or PA12 matrix and a hydrogel filled with talc, were studied, focusing on the difference between PA6 and PA12 based nanocomposites. The structure of ST/PA composites is shown to be largely composed of nanometric particles. However, the presence of few micrometric aggregates is shown at moderate solid volume fractions, for both PA6 and PA12. The results also show that PA6 matrix is more efficient than PA12 matrix to disperse synthetic talc nanoparticles; the difference in matrix effect is discussed in terms of matrix polarity, PA chain radius of gyration and role played by water brought by the hydrogel. Finally, the results of the present study suggest that the structural and rheological properties of ST/PA are close to those of organically modified montmorillonite/PA nanocomposites, especially when PA6 is the matrix.

Talc Nanoparticles Influence on Thermoplastic Corn Starch Film Properties

Composite films of TPS with talc nanoparticles were obtained by thermo-compression in order to study the effect of this filler on structure, optical, and thermal properties. TPS-talc films showed good appearance and homogeneous thickness. Talc addition increased the amount of rigid phase in nanocomposite films, thus their cross-sections resulted more irregular than those of TPS ones. Talc preferential orientation within matrix and good compatibility between particles and TPS were evidenced. TEM observation showed scattered randomly dispersed individual talc platelets. Matrix crystallinity degree was not significantly affected by particles presence. Nanocomposite films were optically transparent due to the laminar morphology and nanosized particles. Materials microstructure presented glycerol- and starch-rich domains. Talc incorporation higher than 3% w/w increased softening resistance of nanocomposites as stated by DMA assays. TPS relaxation temperature of glycerol-rich phase was shifted to higher values since talc nanoparticles reduce starch chains mobility.

Food packaging bags based on thermoplastic corn starch reinforced with talc nanoparticles

Packaging bags from thermo-compressed films of thermoplastic corn starch containing talc nanoparticles (0, 1, 3 and 5% w/w) were developed. Mechanical properties of films were studied by two different techniques (tensile tests and quasi-static assays) revealing starch films reinforcement by talc addition. Strength improvement of thermoplastic starch films with talc concentration higher than 3% w/w was reflected in an increase in both Young's modulus and yield stress. Talc particles modified failure mode of thermo-seal of thermoplastic starch films giving another bags opening possibility. Usually, bags based on starch films could be only opened by tearing while those of starch-talc bionanocomposites could be torn or peeled off. Finally, in order to evaluate packaging bags tightness, films barrier properties were determined. Water vapor and oxygen permeability were reduced 54 and 26%, respectively, by talc addition (3% w/w) to thermoplastic starch.

Thermoplastic starch films reinforced with talc nanoparticles

Nanocomposite films of thermoplastic corn starch (TPS) with talc particles were obtained by thermo-compression in order to study the effect of filler on structure, optical, and thermal properties. Talc increased the films rigid phase, thus their cross-sections resulted more irregular. Talc preferential orientation within matrix and good compatibility between particles and TPS was observed by SEM. Slight crystalline structure changes in TPS matrix were measured by XRD and DSC, due to talc nucleating effect. Randomly dispersed talc nanoagglomerates and individual platelets were assessed by TEM. Laminar morphology and nano-sized particles allowed that nanocomposite films were optically transparent. TPS–talc films resulted heterogeneous materials, presenting domains rich in glycerol and others rich in starch. Talc incorporation higher than 3%, w/w increased softening resistance of the nanocomposites as stated by DMA. Relaxation temperatures of glycerol-rich phase shifted to higher values since talc reduces the mobility of starch chains.

The primary role of iron-mediated lipid peroxidation in the differential cytotoxicity caused by two varieties of talc nanoparticles on A549 cells and lipid peroxidation inhibitory effect exerted by ascorbic acid

Talc particles, the basic ingredient in different kinds of talc-based cosmetic and pharmaceutical products, pose a health risk to pulmonary and ovarian systems due to domestic and occupational exposures. Two types of talc nanoparticles depending on the source of geographical origin – indigenous- and commercial talc nanoparticles were assessed for their potential in vitro toxicity on A549 cells; along with indigenous conventionally used microtalc particles. Cell viability, determined through live/dead staining and 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, decreased as a function of concentration, origin and size of particles. Both varieties of talc nanoparticles differentially induced lipid peroxidation (LPO), which was correlated with the pattern of lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) generation, and glutathione (GSH) depletion. Relatively higher cytotoxicity of indigenous nanotalc could be attributed to its higher content of iron as compared to commercial nanotalc. The known scavenger of ROS, l-ascorbic acid significantly inhibited LPO induction due to talc particles. Data suggest that nanotalc toxicity on A549 cells was mediated through oxidative stress, wherein role of iron-mediated LPO was much pronounced in differential cytotoxicity.