Talc Particles Research Articles

Infrared spectroscopic study of the synthetic Mg–Ni talc series

Five talc samples [(Mg,Ni)3Si4O10(OH)2] covering the entire Mg–Ni solid solution were synthesized following a recently developed and patented process (Dumas et al., Process for preparing a composition comprising synthetic mineral particles and composition, 2013a; Procede de preparation d’une composition comprenant des particules minerales synthetiques et composition, 2013b), which produces sub-micron talc particles replying to industrial needs. Near- and mid-infrared spectra were collected and compared to infrared spectra modeled from first-principles calculations based on density functional theory. The good agreement between experimental and theoretical spectra allowed assigning unambiguously all absorption bands. We focused in particular on the four main OH stretching bands, which represent good probes of their local physical and chemical environment. The description of the vibrational modes at the origin of these absorption bands and the theoretical determination of absorption coefficients provide a firm basis for quantifying the talc chemical composition from infrared spectroscopy and for discussing the distribution of divalent cations in the octahedral sheet. Results confirm that these synthetic talc samples have a similar structure as natural talc, with a random distribution of Mg and Ni atoms. They only differ from natural talc by their hydrophilic character, which is due to their large proportion of reactive sites on sheet edges due to sub-micronic size of the particles. Therefore, the contribution on infrared spectra of hydroxyls adsorbed on edge sites has also been investigated by computing the infrared signature of hydroxyls of surface models.

Effect of content and particle size of talc on nonisothermal melt crystallization behavior of poly(l-lactide)

This work examined the effect of content and particle size of nucleating agent on nonisothermal melt crystallization behavior of poly(l-lactide) (PLLA). Two different particle sizes of talc were used as the nucleating agents of PLLA. Scanning electron microscopy observation revealed that both big and small particles of talc were homogeneously dispersed in the PLLA matrix. Talc significantly accelerated the nonisothermal melt crystallization rate of PLLA. The effect of smaller particle talc on crystallization was obviously better than that of the bigger one. The activation energy based on Friedman equation was evaluated. Lower activation energy was obtained for nucleated PLLA. Finally, addition of talc did not modify the crystal structure.

Particle Size Analysis of Nano-sized Talc Prepared by Mechanical Milling Using High-energy Ball Mill

Talc, hydrous magnesium phyllosilicate, is one of the most popular industrial minerals due to their chemical stability and adsorptivity. While micro-sized talc has long been used as a filler and coating, nano-sized talc recently is attracting attention as additives for improving the stability of nanocomposites. In this study, we produced the nano-sized talc powder by mechanical method using high energy ball mill and investigated the changes in particle size and crystallinity with increasing milling time up to 720 minutes. X-ray diffraction results show that the peak width of talc gradually as the milling proceeded, and after 720 minutes of pulverization, the talc showed an amorphous-like X-ray diffraction pattern. Lase diffraction particle size analysis presents that particle size of talc which was ~12 μm decreased to ~0.45 μm as the milling progressed, but no significant reduction of particle size was observed even after grinding for 120 minutes or more. BET specific surface area, however, steadily increases up to the milling time of 720 minutes, indicating that the particle size and morphology change steadily as the milling progressed. Scanning electron microscope and transmission electron microscope images shows that layered particles of about 100 to 300 nm was aggregated as micro-sized particles after pulverization for 720 minutes. As the grinding time increases, the particle size and morphology of talc continuously change, but the nano-sized talc particles form micro sized agglomerates. These results suggest that there is a critical size along the a, b axes in which the size of plates is reduced even though the grinding proceeds, and the reduction of plate thickness along the c axis leads the increase in specific surface area with further grinding. This study could enhance the understanding of the mechanism of the formation of nano-sized talc by mechanical grinding.

Description of Particle Size, Distribution, and Behavior of Talc Preparations Commercially Available Within the United States.

Widespread use of talc pleurodesis remains controversial for many providers concerned by adverse events such as respiratory failure, which are sometimes fatal. Particle talc size has been implicated in these adverse effects, mainly on the basis of animal studies utilizing large amounts of talc or in observational studies performed on different continents with different talc preparations and doses. Our aim was to determine the particle size and distribution of only the commercially available US-talc preparations and whether the fluid content can affect this distribution. Commercially available US talc was evaluated under scanning electron microscopy and dynamic light scattering (DLS). Distribution of talc particle size was obtained in saline and various protein-based solutions. Talc particle size by DLS was performed with commercially available Sterile Talc Powder and Sclerosol Intrapleural Aerosol. Sterile Talc Powder demonstrated a median diameter of 26.57 μm with a range of particle sizes from 0.399 μm to 100.237 μm. Sclerosol demonstrated a median diameter of 24.49 μm with a range of particle sizes from 0.224 μm to 100.237 μm. The exposure of talc to a protein rich environment (bovine serum albumin and human pleural fluid) led to the development of measureable, new, larger aggregated particle (>100 μm). Currently available US talc seems to have size characteristics similar to previous described "graded" talc preparations. The exposure of talc to a protein rich environment seems to modify the overall distribution of talc particle size when examined by DLS.

Mechanical performance and long-term indoor stability of polyhydroxyalkanoate (PHA)-based wood plastic composites (WPCs) modified by non-reactive additives

This study aims to understand the material properties and long-term indoor stability of a biocomposite based on pine wood flour and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) modified by a nucleating agent, boron nitride (BN), and an inorganic filler, talc, and to develop knowledge of the linkage between the microscale-structure and mechanical properties. Both BN, at a loading of 1 wt% and talc, at 5 wt%, had a nucleating effect on polymer crystallisation, with BN being more effective as evidenced by Avrami kinetic analysis. The addition of 5 and 10 wt% of talc enhanced the tensile strength of the PHBV/wood flour (50/50 wt%) composite from 22.3 ± 1.3 MPa (mean ± 95% confidence interval) to 24.3 ± 0.6 MPa and 24.7 ± 0.9 MPa respectively. The tensile modulus was also improved from 5.6 ± 0.6 GPa to 6.9 ± 0.4 GPa and 8.1 ± 0.7 GPa respectively. The micron-sized talc may fill voids within the composite matrix and/or act as an alternate filler, altering the deformation mechanism. However, the level of improvement in modulus was reduced after 1 year of conditioned ageing under a controlled environment (20 °C, 50% humidity). It is proposed that the combined effects of the swelling of wood through moisture uptake, the shrinkage of PHBV through secondary crystallisation, and the localised stress around talc particles led to weakened talc-PHBV interfaces.

Influence of parallel nozzle electroencapsulation parameters on microcapsule properties – A case study using the Taguchi robust design method

The production of microcapsules by electrospraying two immiscible liquids from oppositely charged parallel nozzles and the subsequent microcapsule collection constitute an electroencapsulation process influenced by numerous parameters. The electroencapsulation parameters include the liquid properties, e.g. bulk liquid conductivity K, viscosity η, density ρ, and surface tension γ; the electric field, gravity field, and the electrospraying and collection geometries; and the atmospheric properties. In the present work, NaI-doped glycerol was used as core liquid, with an optional payload of dispersed thermally carbonized porous silicon nanoparticles (PSi). Chloroform with dissolved Eudragit E 100 cationic copolymer and dispersed talc particles as an anti-tacking agent was used as shell liquid. The influence of varying ten electrospraying parameters (liquid flow rates Qi, electrospraying voltages |Ui| and polarity, solid concentrations, and temperature T) within the cone-jet mode regime on the structure and yield of microcapsules produced by parallel nozzle electroencapsulation was investigated simultaneously using the Taguchi robust design method. Of the investigated parameters, the most important were found to be NaI concentration and T, both influencing the core liquid conductivity; and the liquid flow rates. The Taguchi experiment and additional results suggest that optimally, the parameters affecting liquid conductivities should be set for a coarse atomization current balance when using a maximal shell liquid flow rate. Then, the core liquid flow rate can be adjusted for best process efficiency.

Hydrophobic agglomeration of talc fines in aqueous suspensions

In this work, hydrophobic agglomeration of fine talc particles in aqueous solutions under mechanical conditioning and without any addition of surfactants has been experimentally studied. A method of in-situ measurement of turbidity of flocs suspension in the settlement process has been applied, and the turbidity as a function of settling time has been attempted to fit a certain function so as to assess the hydrophobic agglomeration behaviors. Effects of kerosene dosages, stirring rate, and wettability of talc particles on the hydrophobic agglomeration behaviors have been investigated. The results show that the addition of kerosene can greatly enhance the aggregation of colloidal talc in aqueous suspensions. Besides, the stirring strength and duration make an enormous influence on the aggregation through providing the kinetic energy for overcoming the energy barrier between the approaching particles. It is also found that the wettability of talc is closely related to the aggregation degree. More hydrophobic talc particles show a much stronger aggregation behaviors.

Corona Treatment of Filled Dual-polymer Dispersion Coatings: Surface Properties and Grease Resistance

Dispersion coating layers consisting of hydroxypropylated starch, 0–30 pph of barrier-grade talc and 0–10 pph of styrene-butadiene latex were subjected to both positive and negative direct-current corona treatments utilizing a specially developed dynamic treatment unit. The effects of the surface composition (barrier coating) on the response to the direct current corona treatment were evaluated by measuring contact angles and determining the surface energy. The effects of corona treatment on the properties of the barrier coating were further determined by measuring the contact angle of rapeseed oil and the grease resistance. It was found that the grease resistance of the corona-treated barrier coatings was substantially lower than that of untreated samples, which was ascribed to holes caused by corona discharge strike-through and to chemical changes on the treated surfaces. The corona treatment lowered the surface energy of the coatings, as indicated by an increase in the contact angles of water and rapeseed oil. Changes in the dispersion part of the surface energy were recorded, particularly after positive treatment voltage, whereas a negative discharge led to greater changes in the polar part of the surface energy. X-ray photoelectron spectroscopy (XPS) tests revealed an increase in the proportion of talc at the surface after corona treatment, which indicates a migration caused by the applied electric field. The peak force tapping mode of an atomic force microscope revealed moderate topographical changes in the coatings and a decrease in surface elasticity, supporting the migration of talc particles. In addition, significant changes in the physicochemical properties of the untreated reverse side were observed.

Talc and serpentine particles morphology effect upon their distribution in flotation products (through the example of the Pechenga copper-nickel ores)

Talc and serpentine particles morphology effect upon their distribution in flotation products (through the example of the Pechenga copper-nickel ores)

Effect of annealing on gas permeability and mechanical properties of polylactic acid/talc composite films

In this study, composite films based on polylactic acid and talc were prepared by extrusion film blowing to determine the effect of annealing temperature, annealing time, and talc content on the morphology and gas permeability, as well as thermal and mechanical properties. The results showed that annealing temperature, annealing time, and talc content have a direct effect on polylactic acid crystallinity leading to changes in gas permeability and gas diffusion coefficient, while gas solubility was constant. This effect is related to the talc particles and polylactic acid crystals producing higher tortuosity in the films. Finally, a direct relation between crystallinity level, mechanical properties and gas permeability was observed for all the conditions tested.

Passive acoustic emission monitoring to detect bubble coalescence in the presence of solid particles

Passive acoustic emission monitoring was used to study the role of solid particles on bubble coalescence. The effect of 1–10% w/w talc (hydrophobic) or silica (hydrophilic) particles on air bubble formation and coalescence at a capillary in the presence of MIBC or sodium chloride was determined. Both solids slightly inhibited bubble coalescence while silica created a larger region of partial coalescence compared to talc. At 10% w/w the silica particles appeared to promote coalescence at high MIBC concentration.

Synergistic effects of shear flow and nucleating agents on the crystallization mechanisms of Poly (Lactic Acid)

This paper presents a study of the effects of microscopic particles of talc on the crystallization kinetics of PLA. Our study covers the quiescent conditions and the case where a shear flow is applied “short term shearing”. The incorporation of talc increases the crystallization rate; it enhances the nucleation mechanism through additional heterogeneous nuclei. The microstructure is highly affected by the addition of talc due to the increase of the number of nuclei (i.e. reduced crystalline size). The application of a shear flow increases the ability of PLA to crystallize even in the presence of talc particles. The impact of shear rate becomes dramatically important just after a critical shear rate of 0.1 s−1. It turns out that the shear rate enhances more the crystallization of PLA with talc than the pure PLA under quiescent conditions. Consequently, a supplementary contribution “synergistic effects” is responsible of the relative enhancement of the crystallization of PLA in the presence of shear flow and talc. With combining different experimental analysis techniques and modeling of the crystallization kinetics, the synergistically effects were quantified in terms of the nucleation density induced by the mutual interaction between shear flow and particles.

Dynamic image analysis of differently milled talc particles and comparison by various methods

ABSTRACTIn this study, particle shapes of talc mineral ground by various types of mills were determined using automated dynamic image analyzer by counting averagely 19,000 particles for each mill product. The results were expressed in terms of circularity (C) and bounding rectangle aspect ratio (BRAR). It was concluded that particles created by rod mill had the highest BRAR and the lowest C, while the particles having the highest C and the lowest BRAR were obtained by autogenous milling. The statistical significance of mean shape values of different milled particles was also tested by using one way analysis of variance (ANOVA) and post hoc Tukey test. The ANOVA results showed that there are significant differences among C and BRAR mean values of particles produced by autogenous, ball, and rod mill at 99% level of confidence. The results were in good agreement with the results obtained by other techniques employed previously. Thus, the result of dynamic image analysis (DIA) can be used for quality control of the products of talc mineral as the morphology decides whether specific talc is appropriate for a specific application or not.

Particle-based production of antibiotic rebeccamycin with Lechevalieria aerocolonigenes

Abstract Rebeccamycin is a promising antibiotic synthesized by the filamentous bacterium Lechevalieria aerocolonigenes. To date, the main investigations were focused on the biological effect or the structure elucidation of rebeccamycin. The aim of this study was to develop an efficient cultivation process based on shake flask experiments. The relationship between morphology and productivity and the positive effects of micro- and macroparticle enhanced cultivation on rebeccamycin production with this strain in the pellet-like morphology was investigated. The addition of talc microparticles increased the rebeccamycin concentration to 120 mg L−1 and 3-fold compared to the control without microparticles. An up to 9-fold increase in rebeccamycin concentration was achieved using surface modified talc particles. Through the addition of glass beads as macroparticles, the highest rebeccamycin concentration of approximately 120 mg L−1 was achieved by the induction of mechanical stress. Cultivation with glass beads enhanced the rebeccamycin concentration 22-fold compared to the control without macroparticles. By further increasing the diameter of the glass beads and increasing mechanical stress, the morphology was driven toward mycelial growth and the productivity was decreased. An adjusted mechanical stress, through the addition of macro-shaped glass bead particles, led to the desired increase in productivity.

Thermomechanical and cyclic behavior of biocomposites based on renewable thermoplastics from dimer fatty acids

ABSTRACTMicrobiocomposites based on renewable thermoplastic matrices such as thermoplastic polyurethane (TPU) and polyamide (DAPA), synthesized from dimer fatty acids, and high aspect ratio talc were prepared. TPU/DAPA blends and their corresponding biocomposites exhibited mechanical behavior, which is linked to those of the matrices and their relative contents, i.e., going from a typical semicrystalline behavior (DAPA) to an elastomeric one (TPU). The understanding of the thermomechanical and cyclic behavior of these advanced materials, particularly for TPU/DAPA with high TPU content, is detailed. Addition of particles of high aspect ratio natural talc (HAR) improved the storage modulus over the whole temperature range (almost five times with 5 wt % HAR). Under cyclic manipulation, the biocomposites displayed a stress softening related to the Mullins' effect. An increase of the hysteresis and the residual deformation with the HAR content has been shown. The hyperelastic models of Mooney–Rivlin and Ogden–Dorfmann, used to predict the loading and unloading behavior, fitted with experimental data. The present work also reports the experimental characterization of the deformation mechanisms of these renewable biocomposites through different microscopic techniques at different scales, such as atomic force, scanning electron and transmission electron microscopies. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44610.

Multichannel 65 zF rms Resolution CMOS Monolithic Capacitive Sensor for Counting Single Micrometer-Sized Airborne Particles on Chip

The first integrated CMOS monolithic sensor system for on-chip capacitive detection of micrometric airborne particulate matter (PM) is presented. The chip is based on a 32 channel lock-in architecture allowing a dust collection area of 1.15 mm2 where interdigitated differential microelectrodes, fabricated with the top metal and directly exposed to air, allow single particle sensitivity. The preamplifier input capacitance is significantly minimized thanks to the electrode–amplifier proximity and proper partitioning of the sensing area, in order to reduce the noise. Each channel comprises a charge preamplifier with adjustable high-pass filtering for flicker noise shaping, square-wave mixer, $g_{m}$ -C tunable low-pass filter (40–750 Hz), and a 6 bit digital network for automatic compensation of electrodes mismatching with a granularity of 150 aF. Thanks to the capacitive noise of only 65 zF rms with 25 ms temporal resolution, deposition events of single mineral talc particles were recorded down to 1 $\mu \text{m}$ diameter with a signal-to-noise ratio of $\approx 18$ dB. This chip paves the way to pervasive mapping of both indoor and outdoor PM in the 1–30 $\mu \text{m}$ range.

Surface Modification of Talc Particles with Phthalimide: Study of Composite Structure and Consequences on Physical, Mechanical, and Optical Properties of Deinked Pulp

Commercial talc was modified with phthalimide to produce a composite filler, which was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray fluorescence spectroscopy (XRF), and scanning electron microscope (SEM). It was used as a papermaking filler, and its efficiency was compared with that of plain commercial talc and when mixed with additives (i.e., cationic polyacrylamide and alum-rosin size). The results showed that phthalimide could be linked appropriately to the surface of talc particles through forming ester bonds with the surface hydroxyl groups. The brightness of the composite filler was more than that of the commercial filler due to a reduction in the impurities and removal of the metal compounds. Unlike other treatments, the brightness of the papers filled with modified talc (MT) was enhanced with increases in filler loading. In spite of reducing the paper strength in all treatments, the reduction was significantly less in the MT treatment, which implies the enhancement in particle tendency to develop hydrogen bonds in the fiber network.

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.

Melt-spun talc-filled polypropylene fibers and yarns with higher thermal shock resistance

An increase in the application areas of textiles has resulted in the need for improved and additional properties and functions, which should be provided by polymers with different functionalities or the addition of particles to the fibers. In the framework of this study, microsized talc particle-filled polypropylene (PP) fibers and yarns were produced and the mechanical, physical and thermal properties of the fibers and yarns were analyzed with respect to production parameters. The main motivation of the selection of talc as the filler material is to improve the thermal shock resistance and decrease the shrinkage of PP fibers and yarns. As a result of experimentation, it was observed that an increase of talc ratio decreases the tensile strength of fibers and yarns. However, this reduction does not seem to be an obstacle to produce fabrics. Furthermore, the addition of microsized talc particles in PP yarns dramatically improved thermal shock resistance and helped to decrease the shrinkage of these yarns.

Structure and properties of highly filled poly (vinyl alcohol)/talc composites prepared through thermal processing: effects of talc size

Poly (vinyl alcohol) (PVA), a multi-hydroxyl polymer with excellent comprehensive properties, is an expected candidate to prepare high-performance polymer-based composites without using any coupling agents or compatibilisers. However, the poor thermal processability of PVA is its biggest obstacle. In this paper, by adopting polyol as a plasticiser, highly filled PVA/talc composites with good mechanical properties were successfully obtained through melt extrusion and injection, and the effects of talc size on structure and properties of the composites were studied. The results showed that talc highly filled PVA composites had satisfying melt processability, and the decrease of talc particle size increased the –OH groups on the edges of the talc layers, thus improving the compatibility between talc and PVA, and making talc particles dispersed more uniformly in PVA matrix. As a result, the composites with smaller talc particles had the higher threshold filler concentration to form the filler networks and the better flow behaviour. The smaller talc flakes also exhibited higher orientation in PVA matrix and induced more PVA molecular chains to orient along the melt flow direction, leading to the enhancement of the mechanical properties of the composites.