Talc Particles Research Articles

Phase evolution and properties of porous cordierite ceramics prepared by cordierite precursor pastes based on supportless stereolithography

Porous cordierite ceramics with high flexural strength, low thermal expansion coefficient and custom structure were in-situ prepared using talc, alumina and silica particles by supportless stereolithgraphy (SSL) firstly in this study. To restrain the formation of defects, dibutyl phthalate (DBP) as low temperature pore-forming agent and a heating rate as low as 0.2 ℃/min were allowed to control the pyrolysis in the multistage debinding process based on thermal gravimetric analysis (TG). The effect of sintering temperature on phase evolution, microstructure and properties was investigated in details. The results showed that the generation of α-cordierite started at 1250 ℃ through the reaction between spinel and cristobalite, which generated volume expansion to offset sintering shrinkage. A porous cordierite ceramic with single phase was obtained at 1400 ℃. In addition, the coefficient of thermal expansion was as low as 1.65 × 10−6 /℃ and the flexural strength was 26.16 MPa with the apparent porosity of 48.62 %. The effects of configuration on the apparent porosity, shrinkage, mechanical and thermal properties were investigated by analyzing the phase composition and microstructure. Finally, the porous cordierite ceramic with custom structure was prepared successfully.

Effect of Talc Particle Size in Detergents for Fruits and Vegetables on the Ability to Remove Pesticide Residues.

Detergents containing abrasive talc particles for washing fruits and vegetables were designed and investigated. Detergent prototypes were developed with the following composition: 40% talc particles, 1.5% surfactants, 5% ethyl alcohol, 1% sodium citrate, 1% sodium carbonate, 1.5% glycerin, and 0.5% preservative. Xanthan gum (0.5% concentration) was used as a viscosity modifier to stabilize the dispersion of talc particles. Three types of detergent prototypes were prepared, differing in the size of the talc particles. The following fractions were used: 50–125, 250–500, and 710–1000 μm. The particle size effect on the effectiveness of the removal of surface pesticide residues was investigated. A specially developed methodology was used. Three types of pesticides (boscalid, acetamiprid, and pyraclostrobin) were applied to a cherry tomato, tangerine, and cucumber, and then a model washing process was performed using the developed detergents. The changes in the pesticide content on the surface of fruit and vegetables were assessed by liquid chromatography–tandem mass spectrometry. Detergents with talc particles of sizes 50–125 and 250–500 μm were more efficient in the removal of pesticide residues from the surface of fruit and vegetables compared to detergents with 710–1000 μm talc particles.

Structural, Mechanical and Flammability Characterization of Crosslinked Talc Composites with Different Particle Sizes

The influence of filler particle size on selected physicochemical and functional properties of polymer composites was analyzed. The following test was carried out for the system: the bisphenol A glycerolate (1 glycerol/phenol) di-methacrylate (BPA.DM) was subjected to UV-polymerization in bulk with N-vinyl-2-pyrrolidone (NVP) as a polymer matrix and talc with particle sizes ranging from ≤8 to 710 µm as a non-toxic and cheap mineral filler. An effective method of preparing cross-linked polymeric composites with talc was developed. The obtained samples were subjected to structural analysis and the thermal, mechanical and flammability properties were assessed. It has been empirically confirmed that the talc particles are incorporated into the composite structure. However, with increasing particle size, the composite heterogeneity increases. In the case of the developed method of sample production, homogeneous systems were obtained for particles in the ≤8–250 µm range. The surface roughness of the samples correlates directly with the size of talc particles. The value of Young’s modulus during the axial stretching of samples decreases with the increasing size of talc particles. For the composites containing ≤15 and ≤35 µm talc particles, the highest values were obtained under bending conditions. There was no equivocal effect of particle size on the composites’ swelling in water. The addition of talc reduces the flame height and intensity slightly. The biggest difference was obtained for the composites containing relatively large talc particles. It was proved that the selected properties of polymer composites can be controlled depending on the size of the talc particles.

Experimental Study on Factors Influencing Throughput Rate and Process of Polymer-Mineral Filler Mixing in a Twin Screw Extruder

Abstract The experimental study of mixing polymer (polypropylene, PP) with mineral filler (Talc) by both simultaneous and separate feed system in a twin screw extruder was described. In this study, melt flow rate (MFR) of PP, talc particle size and talc mixing ratio to PP were selected as parameters of interest. It was found that these parameters had influences on the maximum throughput rate of mixture. In the cases of constant talc particle size and mixing ratio while MFR of PP was varied from 1.8 to 33, it was observed that throughput rates of all mixtures with different MFR values increased as a function of screw speeds. Throughput rates of the mixture of lower MFR PP (MFR = 1.8) were slightly lower than those of the higher MFR mixture (MFR = 10, 33) for both simultaneous and separate feed systems. With regard to effects of talc particle size, compounds having fixed talc mixing ratio showed lower throughput rates when talc particle size was smaller. In the case where talc mixing ratio was varied, compounds with fixed MFR of PP and talc particle size showed lower throughput rates when talc mixing ratio was larger. The mixing state in the mixing zone was also observed. Based on the overall findings, the mechanisms of filler mixing were clearly understood. The observed mixing patterns were similar for both simultaneous and separate feed systems. It was found that the elimination of the air accompanying the filler when the filled polymer mixture passed down the extruder is important for mixing. Through the experimental observations, the schematic diagram, the model and the flow chart of the proper filler mixing process were proposed.

Pulsating high-gradient magnetic separation of chalcopyrite and talc

The selective flotation of chalcopyrite from talc in practice is currently difficult and consumes a large amount of depressors, resulting in high production and environmental costs. The pulsating high-gradient magnetic separation (PHGMS) method has a strong potential for the effective separation of chalcopyrite and talc, based on their difference in magnetic susceptibility. In this work, the effects of magnetic induction, pulsating frequency and feed velocity of a pliot-scale PHGMS separator on the separation performance for pure chalcopyrite and talc minerals were investigated. The results indicate that the PHGMS achieves a selective separation of chalcopyrite from talc; and under the optimized conditions, a chalcopyrite concentrate of 30.22% Cu grade with 75.79% chalcopyrite recovery at talc content as low as 5.77% was produced from a chalcopyrite-talc mixture assaying 10.69% Cu and 66.67% talc. It was found that the chalcopyrite recovery for the ultra-fine particles fraction below 30 µm is lower than those of coarser fractions, as a result of the increased hydrodynamic drag over the magnetic force acting upon the ultra-fine particle. Entrainment may also occur between ultra-fine talc and chalcopyrite particles, which reduces the Cu grade for such ultra-fine particles in the copper concentrate. The PHGMS method may provide an environment-friendly and low-cost technology for the separation of chalcopyrite and talc.

Effects of Residual Xanthate on Flotation Efficiency of a Cu-Zn Sulfide Ore

Reuse of process water in the flotation of sulfide ores has crucial importance for environmental sustainability and improved process economy. However, the chemistry of process water may be a critical subject for the flotation efficiency as the dissolved ion concentration increases with water reuse. In this study, the effects of water reuse on the flotation efficiency of a Cu-Zn sulfide ore were investigated. The flotation flowsheet consists of a pre-flotation section to remove the naturally floatable talc particles, and sequential copper and zinc flotation sections. Calcium, sulfate, thiosulfate, and xanthate were found as major contaminating ionic species in the process water discharged from flotation circuits. The flotation tests with recirculated water from the zinc rougher tailing revealed that the presence of residual xanthate caused unintentional activation of copper minerals in the pre-float section. Copper recovery increased in the pre-flotation section and resulted in the loss of copper to the pre-float concentrate, which is considered as a tailing stream in the current flowsheet. Various types of activated carbon samples were tested to remove the residual xanthate from the tailing water. The carbon samples could be regenerated by heat treatment and reused for water treatment. Performance of the activated carbon samples was directly related to the pore size and surface area. Carbon-treated tailing water could be re-used in flotation without affecting the flotation performance.

Experimental Investigation of Polypropylene Composite Drawn Fibers with Talc, Wollastonite, Attapulgite and Single-Wall Carbon Nanotubes.

Isotactic polypropylene (PP) composite drawn fibers were prepared using melt extrusion and high-temperature solid-state drawing at a draw ratio of 7. Five different fillers were used as reinforcement agents (microtalc, ultrafine talc, wollastonite, attapulgite and single-wall carbon nanotubes). In all the prepared samples, antioxidant was added, while all samples were prepared with and without using PP grafted with maleic anhydride as compatibilizer. Material characterization was performed by tensile tests, differential scanning calorimetry, thermogravimetric analysis and Fourier transform infrared spectroscopy. Attapulgite composite fibers exhibited poor results in terms of tensile strength and thermal stability. The use of ultrafine talc particles yields better results, in terms of thermal stability and tensile strength, compared to microtalc. Better results were observed using needle-like fillers, such as wollastonite and single-wall carbon nanotubes, since, as was previously observed, high aspect ratio particles tend to align during the drawing process and, thus, contribute to a more symmetrical distribution of stresses. Competitive and synergistic effects were recognized to occur among the additives and fillers, such as the antioxidant effect being enhanced by the addition of the compatibilizer, while the antioxidant itself acts as a compatibilizing agent.

Investigation of detergent compositions on the effectiveness of alumina and aluminium titanium carbide cleaning

Particle contamination on a surface is a critical issue for the electronics manufacturing processes. Detergents that are composed of surfactants and appropriate additives can decrease the natural attraction forces between particles and surface, leading to effective particle removal. This work aims to investigate the influences of detergent pH and additives on the effectiveness in removing inorganic particles from Al2O3 and AlTiC substrates, which are commonly used materials in the electronics industry. In this study, we chose a model detergent comprised of an anionic surfactant, sodium dodecylbenzene sulfonate, and two additives, namely sodium acid pyrophosphate and ethanolamine. Talc particles were employed as a model inorganic contaminant. The effects of pH and ethanolamine concentration on the cleaning effectiveness of the model detergent were examined using optical microscopy and X-ray photoelectron spectroscopy (XPS). The stability of talc suspension in detergent solution, which is related to the possibility of particle recontamination, was determined by zeta potential. Our results indicate that the pH of the detergent directly affects its cleaning efficiency, likely by increasing the electrostatic repulsion between the surface and the talc particles. Similarly, the increasing ethanolamine concentration elevates the pH of the detergent, leading to better cleaning performances on both Al2O3 and AlTiC substrates.

Laser sintering of coated polyamide 12: a new way to improve flammability

In this study coatings of kaolin and talc particles were successfully applied on the surface of polyamide 12 powder intended for laser sintering (LS). Microscopic observations revealed that using carboxymethyl cellulose (CMC) as surface modifier for fillers led to a better coverage of polymer grains with a surface coverage between 6 and 16% as a function of filler type and content. Differential scanning calorimetry measurements showed that the addition of talc and kaolin led to an increase in the crystallization temperature of PA12, but at the expense of processability. Process parameters were optimized in order to manufacture LS samples with the different coated powders. Fire behavior assessed by cone calorimetry showed that the use of CMC resulted in a significant decrease in the peak of heat release rate depending on the filler type and content. This behavior can be partially explained by an interaction between CMC, fillers and polymer, with the formation of amide linkage between carboxyl part of CMC and amine end groups of polyamide, resulting in an increase in the complex viscosity of materials.

Heterogeneous Nucleation Effects of Talc Particles on Polymorphic Crystallization of Cocoa Butter

Polymorphic crystallization of cocoa butter (CB) in a bulk system was examined for the influence of adding talc particles at different concentrations (0.1–5%). While the system was cooled from the melt and subsequently heated, changes in the heat flow and crystal structure of CB were analyzed using differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (SR-XRD). Synchrotron radiation microbeam X-ray diffraction (SR-μ-XRD) was employed to determine lamellar-plane directions of CB crystals occurring with talc addition. At any cooling rates (0.1–15 °C/min) applied, talc promoted CB crystallization to elevate the onset crystallization temperature logarithmically with the increasing concentration of talc; this effect became more prominent at higher cooling rates. Talc also acted as a polymorphic stabilizer so that CB crystallized in more stable forms even when cooled at highest rate of 15 °C/min. Moreover, a highly ordered lamellar-plane direction was extensively observed for CB crystals occurring with 0.1% talc addition, which was disturbed by 0.5% talc addition probably due to the spatial dispersion of densely populated talc particles in their randomized orientation. These heterogeneous nucleation effects indicate the potential of talc particles to be used for the quality and productivity control of CB-based products.

Decoupling the effects of alteration on the mineralogy and flotation performance of Great Dyke PGE ores

Ores from a single deposit may exhibit extensive variability in their mineralogy and texture. The ability to quantify this variability and link it to mineral processing performance is one of the primary goals of process mineralogy. This study focuses on the effect of alteration in three platinum group element ore samples from the Great Dyke in Zimbabwe - two of which were more pristine compared to the third, which was locally classified as 'oxidized' ore. These ores are known to be characterized by varying degrees of alteration, resulting in numerous challenges in flotation and affecting both grade and recovery. Alteration, by near-surface oxidation, of the valuable base metal sulphides and platinum group minerals resulted in lower flotation recoveries of Cu, Ni, Pt, and Pd. Evidence of incipient oxidation was more readily observed in the base metal sulphide assemblage than the platinum group mineral assemblage, even though the loss in recovery (because of oxidation) was most significant for Pd. Alteration through hydration resulted in a significant increase in mass pull and dilution of concentrate grade through the inadvertent recovery of naturally floating gangue comprising composite orthopyroxene and talc particles. In this study, the amount of naturally floating gangue was more strongly correlated with the talc grain size distribution than the grade of talc in the flotation feed. The oxidation and hydration alteration reactions are not necessarily mutually exclusive, although one may be more dominant than the other, giving rise to ore variability.

Large improvement in DC electrical properties of EPDM with 2D platelet nanoclay

Space charge, electrical conductivity and breakdown strength of polymeric insulations are considered to be the most important characteristics for designing DC cable insulation. In this paper, we report the DC electrical properties of ethylene propylene diene polymethylene (EPDM) polymer with two different 2D inorganic clays, one of which shows large improvement of space charge distribution, controlled electrical conductivity and breakdown voltage. The results revealed that compared with the pure EPDM, the space charge accumulation for EPDM filled with Talc was suppressed significantly, especially at 50 °C with thermal gradient. The maximum local electric field enhancement in the volume decreased from 60% for the pure EPDM to 4% for the Talc-filled EPDM under 20 kV mm−1 at 25 °C, while the corresponding value dropped dramatically from 83% to 8% at 50 °C with thermal gradient. Compared with the EPDM, the Talc-filled EPDM showed higher conductivity but with less dependence to electric field and temperature. Microstructure studies suggest the platelet Talc particles distribute in the EPDM matrix homogeneously and make a uniform morphology. This condition consequently causes a desired trap distribution with high density of shallow traps due to the presence of high interfacial area between polymer chains and clay particles which prevents the charge accumulation during the charge carrier transport under DC electric field. Results of the thermally stimulated depolarization current spectra of the samples are in good agreement with the predicted trap distribution based on the experimental results and morphological study.

Influence of Fillers on the Viscosity Properties of One-Pack Polyurethane Sealants

The paper investigates the effect of fillers on the viscosity properties of one-pack polyurethane sealants. It is noted that with the introduction of such mineral fillers as Mikarb, Midol, MTD2 chalk and aluminum hydroxide, the dynamic viscosity of the composition increases uniformly, while when filled with chemically precipitated Calofort SV chalk and MT-GShM talc, an abnormally sharp increase in viscosity is observed. Such an increase in viscosity for Calofort SV is explained by a highly developed surface, in contrast to other fillers. Talc is characterized by a plate-like shape of particles, which leads to a complex orientation of talc particles in the composition and shear difficulties.It was found that a sealant filled with chemically precipitated chalk has more than 100 pts. wt.(parts by weight), per 100 pts. wt. of the prepolymer under the influence of shear forces (at a constant shear rate) during the first 10 minutes of exposure, a sharp decrease in viscosity is observed, which is characteristic of thixotropic compositions, reaching a constant value after 5-10 minutes. After 10 minutes, the thixotropy of the sealant is restored. Talc does not impart thixotropic properties to the sealant composition.

How does the SDS addition in talc grinding affect its floatability?

Talc processing starts with grinding followed by flotation. The flotation feed preparation significantly affects the concentrate quality. In this study, the preparation of talc flotation feed by grinding was investigated in the absence and presence of sodium dodecyl sulfonate (SDS), one of the well-known flotation reagents. The natural floatability of talc was compared to its floatability after adding the SDS in either grinding or flotation. The results proved a significant effect of grinding conditions on its natural floatability. The higher flotation recovery is achieved by grinding at the alkaline medium compared to the acidic medium at 30% solids. More interestingly, adding the SDS in flotation produced a higher talc recovery than that the achieved recovery by its flotation after adding SDS in grinding although it has more chance for mixing the reagent with particles and adsorption of SDS to talc particles. Thus, the tested variables in grinding tests negatively affect the SDS effectiveness as a flotation reagent for talc.

Improved heat resistance in poly (lactic acid)/ethylene butyl methacrylate glycidyl methacrylate terpolymer blends by controlling highly filled talc particles

Improved heat resistance in poly (lactic acid)/ethylene butyl methacrylate glycidyl methacrylate terpolymer blends by controlling highly filled talc particles

Anisotropic robustness of talc particles after surface modifications probed by atomic force microscopy force spectroscopy

As a versatile mineral, the crystalline hydrated magnesium silicate talcum, or talc, has been widely used in numerous industries from pharmaceutical formulations to composite material designs. Its efficient application as filler/additives incorporates the improvement in concomitant properties within materials, e.g., strength, which involves interactions between talc particles and aqueous/nonaqueous matrices. Successful property enhancement imposes ideal mixing and homogenous adhesion within a talc particle, but they are limited by the coexistence of face and edge surfaces of talc, which exhibit different level of hydrophobicity. Here, using atomic force microscopy force spectroscopy, we showed that although hydrophilic talc particles obtained from acid treatment or aminosilanization better adhered with materials representing a matrix, the anisotropic characters of the two surface types persisted. Conversely, the degree of talc’s surface anisotropy reduced with the surface hydrophobization by aliphatic methylsilanization, but followed by the decrease in adhesion. With ten-fold difference in Hamaker constants of the probe/talc surface interacting pairs, we showed that the adhesions resulted from van der Waals interactions that suggested the influence of surface polarity. The insight from this work would provide grounds for strategies to modulate talc’s adhesion, hydrophobicity and surface uniformity.

Thermal degradation kinetics of Opuntia Ficus Indica flour and talc-filled poly (lactic acid) hybrid biocomposites by TGA analysis

This paper reports the effect of lignocellulosic flour and talc powder on the thermal degradation behavior of poly (lactic acid) (PLA) by thermogravimetric analysis (TGA). Lignocellulosic flour was obtained by grinding Opuntia Ficus Indica cladodes. PLA/talc/ Opuntia Ficus Indica flour (OFI-F) biocomposites were prepared by melt processing and characterized using Wide-angle X-ray scattering (WAXS) and Scanning Electron Microscope (SEM). The thermal degradation of neat PLA and its biocomposites can be identified quantitatively by solid-state kinetics models. Thermal degradation results on biocomposites compared to neat PLA show that talc particles at 10 wt % into the PLA matrix have a minor impact on the thermal stability of biocomposites. Loading OFI-F and Talc/OFI-F mixture into the PLA matrix results in a decrease in the maximum degradation temperature, which means that the biocomposites have lower thermal stability. The activation energies (Ea) calculated by the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) model-free approaches and by model-fitting (Kissinger method and Coats-Redfern method) are in good agreement with one another. In addition, in this work, the degradation mechanism of biocomposites is proposed using Coats-Redfern and Criado methods.

Development the Mechanical Properties of the Acrylic Resin (PMMA) by Added Different Types of Nanoparticles, Used for Medical Applications

This research is studying the effect of reinforcement the acrylic resin (PMMA) by two types of nanoparticles, which included: Walnut shell (WSP) and Talc particles (TP) that practical sizes are (40.8 and 29.2 nm) in individually form, and utilize at three various concentrations (0.1, 0.2 and 0.3wt.%), to improve in the mechanical properties of composite materials. The results showed that the Tensile and Hardness shore D properties became better with increasing the concentration of nanoparticles. The highest value of (tensile strength, modulus of elasticity and elongation at break) was (28 MPa. 1.28 GPa and 2.35%) for (PMMA: 0.3% WSP) composite specimens. And the highest value of hardness shore D was (77) for (PMMA: 0.3% WSP) composite specimen.

Transcriptomic and epigenomic effects of insoluble particles on J774 macrophages

ABSTRACT Here we report epigenomic and transcriptomic changes in a prototypical J774 macrophage after engulfing talc or titanium dioxide particles in presence of estrogen. Macrophages are the first immune cells to engage and clear particles of various nature. A novel paradigm is emerging, that exposure to so-called ‘inert’ particulates that are considered innocuous is not really free of consequences. We hypothesized that especially the insoluble, non-digestible particles that do not release a known hazardous chemical can be underappreciated agents acting to affect the regulation inside macrophages upon phagocytosis. We performed gene chip microarray profiling and found that talc alone, and especially with oestrogen, has induced a substantially more prominent gene expression change than titanium dioxide; the affected genes were involved in pathways of cell proliferation, immune response and regulation, and, unexpectedly, enzymes and proteins of epigenetic regulation. We therefore tested the DNA methylation profiles of these cells via epigenome-wide bisulphite sequencing and found vast epigenetic changes in hundreds of loci, remarkably after a very short exposure to particles; ELISA assay for methylcytosine levels determined the particles induced an overall decrease in DNA methylation. We found a few loci where both the transcriptional changes and epigenetic changes occurred in the pathways involving immune and inflammatory signalling. Some transcriptomic and epigenomic changes were shared between talc and titanium dioxide, however, it is especially interesting that each of the two particles of similar size and insoluble nature has also induced a specific pattern of gene expression and DNA methylation changes which we report here.

Platy Talc, Asbestos, and Talc Fibers in the Female Genital Tract in Patients with Ovarian Cancer

Abstract Introduction/Objective Recent analyses on human tissue help inform the discussion regarding talc and ovarian cancer, by showing that, in some patients, considerable talc can migrate to multiple organ sites in the pelvic region from perineal application. Recently, we showed that birefringent particles were seen by polarized light microscopy and shown to be talc by scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDS) and/or Raman spectroscopy in surgically resected tissues from patients with ovarian carcinoma and perineal talc exposure. These sites included ovary, cervix, fallopian tube, uterine serosa, and regional lymph nodes. Fibrous talc, with greater carcinogenic potential as determined by the International Agency for Research on Cancer, may be observed in pelvic tissues. Besides ascension through the reproductive tract, particles and fibers may gain entry to pelvic organs by accessing small submucosal lymphatics in the lower part of the tract. Both platy and fibrous talc have an Mg-Si elemental signature, weight % Mg/Si ratio within 5% of the theoretical value of 0.649, and thus are distinguishable from other exogenous substances including the various subtypes of asbestos. Methods Tissue-based analytic methods (including in situ SEM, where a paraffin block is examined directly under variable pressure) are critical in the detection of talc and asbestos, particularly since they preserve architecture, and demonstrate talc and/or fibrous particles within their histologic environment; this may help inform exposure origin and pathophysiologic significance. Results We reviewed the analytic outcomes of our consultative experience to date. This showed that 180 of 196 patients with a history of perineal talc exposure had birefringent particles seen by light microscopy in surgically resected pelvic tissues, and 82 of 91 had talc confirmed by SEM/EDS. Carcinogenic fibers were found in 28/82 (34%) of these patients, with talc fibers only (19/82 patients, 23%), asbestos (7/82, 9%) or both (2/82, 2%) confirmed by SEM/EDS. Conclusion Our study confirms that talc and toxic fibers may be found in human pelvic tissues of talc-exposed patients. Because the SEM/EDS method samples only a small amount of tissue relative to what is in the paraffin block, the finding of exogenous particles by this method typically translates to a high overall particle burden, when scaled mathematically to bulk tissue.