Talc Content Research Articles

Crystallization behavior of polypropylene filled with surface-modified talc

Talc-filled polypropylene (PP) composites were prepared by extrusion in a wide composition range (0–40 wt %). To improve the affinity relation between talc and the PP matrix, we modified the talc surface with silane coupling agents. Differential scanning calorimetry investigations on test samples, prepared by injection moulding, revealed that the talc content and its surface modification had a pronounced effect on the crystallization behavior of the filled PP composites. The experimental results indicate that a talc concentration of 2 wt % strongly affects the nonisothermal crystallization process of the PP, especially when talc is silane treated Isothermal crystallization experiments on samples with minimum amounts of talc (2 wt %) revealed an improved nucleation activity with silane-treated talc. © 1996 John Wiley & Sons, Inc.

The relationship between perineal cosmetic talc usage and ovarian talc particle burden

OBJECTIVE: Epidemiologic studies support the hypothesis of a dose-related risk of epithelial ovarian cancer with perineal talc exposure. Frequency and duration of talc usage has not been previously correlated with ovarian talc content. STUDY DESIGN: Ovaries were studied from 24 women undergoing incidental oophorectomy who were interviewed regarding talc usage. Twelve subjects reported frequent perineal talc applications; the twelve controls reported no use. Ovarian tissue blocks were digested and analyzed by polarized light microscopy and analytic electron microscopy to identify and quantify talc. RESULTS: Talc was identified in all 24 cases by either light or electron microscopy. Talc particle counts were completely unrelated to reported levels of perineal talc exposure. CONCLUSIONS: The detection of talc in all ovaries demonstrates that it can reach the upper genital tract. Widespread exposure to talc during diapering may contribute to the ubiquitous presence of talc in ovarian tissue. (A M J O BSTET G YNECOL 1996;174:1507-10.)

Quantitative characterization of surface deformation in polymer composites using digital image analysis

AbstractThe stress whitening of polymers and polymer composites during surface deformation (scratching) can represent a severe technological problem in certain applications. For example, scratch resistance is particularly important for poly(propylene) automobile interior components. Unfortunately, the addition of reinforcing agents such as talc or mica for improved dimensional stability and rigidity often results in an increased sensitivity to scratching. The ability to design new materials with reduced visible surface deformation requires more sophisticated information about the deformation mechanisms of polymers and polymer composites near surfaces and their relationship to the scattering of incident light. We have developed a technique to quantify the light scattered from polymer composite surfaces due to surface deformation. We first deform the material in a controlled manner using a scratch testing apparatus. We then analyze the region near the scratch with reflected polarized light in an optical microscope coupled to a digital image analysis system. By measuring the light scattering from the sample as a function of incident light polarization and sample orientation, it is possible to obtain information about the nature and extent of deformation at the sample surface. In this report, we describe our technique and demonstrate how it can be used to quantify the surface deformation of poly(propylene)‐talc composites. By examining a series of materials as a function of talc content, we have been able to obtain information that can be related to specific micromechanisms of deformation near the scratch, such as the orientation of the polymer and the voiding near the talc particles. The technique should assist in the improved development of similar materials for applications in which surface appearance is a primary concern.

Effect of Talc on Properties of Corn Starch Extrudates

AbstractCommercially available 0, 25, 50 and 70% amylose corn starches were extruded with up to 5% talc {(OH)2Mg3(Si2O5)2} in a single screw Brabender laboratory extruder at 18% moisture content, 140°C barrel temperature, and 140rpm screw speed. Expansion ratio, unit density, percentages of closed and open pores, porosity and molecular degradation of extruded starches were measured.Addition of talc resulted in decreases in expansion ratio, unit density and percentage of open pores, and in increases in percentage of closed pores and porosity of extrudates. The extrudates became smaller with a greater number of round and uniformly sized cells with added talc. Gel permeation chromatographic fractionation of extrudates showed extensive degradation of fraction I with increasing talc concentrations. The talc appeared to have provided nucleation sites for water vaporization as the material exited the die of the extruder.

Beneficiation of talc from the Valmalenco mine, Italy

The objective of this research was to investigate the possible application of integrated circuits to the concentration of talc from the Valmalenco mine, located in northern Italy. The investigation was aimed at producing a high-grade product (low in impurities such as iron and carbonate) that would be suitable for industrial applications. Because of the presence of accessory minerals, the talc concentrate from this ore is not, at the present time, suitable for industrial applications.

Stability relations and Al content of tremolite and talc in CMASH assemblages with kyanite + zoisite + quartz + H2O

Stability relations and Al content of tremolite and talc in CMASH assemblages with kyanite + zoisite + quartz + H2O

Mechanical properties of talc‐filled polypropylene. Influence of filler content, filler particle size and quality of dispersion

AbstractMechanical properties of polypropylene‐talc composites are measured as a function of talc concentration up to 40 wt.‐%, Young's modulus of filled polypropylene shows linear increase with talc concentration up to double the value of unfilled polymer. Yield stress and Charpy notch toughness decrease with increasing talc content below matrix level at the highest filler content. Composite ultimate tensile elongation and tensile impact strength decrease sharply beginning at the lowest filler concentration. The influence of the talc particle size on the mechanical properties, especially composite toughness, mentioned above, is investigated. Four type of talc were used. Notch toughness decreases according to a linear dependence with mean size of talc particles. Evaluating impact strength possible content of agglomerates of filler and other additions is necessary to be included: tensile impact strength gives slow linear dependence with increasing content of filler particles and/or agglomerates above about 10 μm. The influence of talc particle size on the toughness of filled polypropylene becomes strong if the rubber particles are present.

Abdominal wall thickness as a means of assessing peritoneal fibrosis in mice

Herein we describe a method for the quantitative assessment of connective tissue deposition within the peritoneal cavity. Female C57BL/6 mice (8–10 weeks) were given a single intraperitoneal injection of varying concentrations of talc (100 mg, 50 mg, 30 mg, 20 mg) in 1 ml of PBS or PBS alone. After 14 days, animals were killed. Adhesion formation was measured by the standard method of Myllârniemi et al. (1966), namely a gross visual inspection of the peritoneal cavity. This analysis gave a crude assessment of connective tissue deposition in the abdonimal cavity but did not allow one to distinguish more subtle differences between intermediate dosage groups. In addition, a histological evaluation was performed. For the latter method, portions of the abdominal wall of mice were fixed and processed for histological analysis using Masson's Trichrome stain which allows for differentiation of connective tissue components. The thickness of connective tissue between the parietal peritoneum and the underlying abdominal wall muscle was measured. A dose-dependent increase in connective tissue deposition was observed in talc-treated animals compared to saline control animals. A differential cell count of the peritoneal exudate cells (PEC) showed that there was no change in cell populations in talc treated animals (compared to control animals). Given the above results, the measurement of connective tissue thickness was found to give the most accurate assessment of peritoneal fibrosis than other previously used methods.

Time-resolved Light Scattering Studies of Crystallization in Mixtures of Poly (ethylene telephthalate) and Talc

We investigated the crystallization behavior in mixtures of poly (ethylene terephthalate) (PET) and talc using the time-resolved light scattering. The time variation of the orientation fluctuation was measured using on Hv optical geometry, and the induction time, overall crystallization rate, and linear growth rate (G), were estimated by an invariant method. G was analyzed on the basis of the Hoffman-Lauritzen theory. As the crystallization temperature Tc increased, a regime transition from III to II was found to occur in the PET/talc mixture and the neat PET. For the PET/talc system, the overall crystallization rate increased with increasing talc content. G however was independent of talc content, i. e., talc acted as a nucleating agent. The mixture also shows high crystallinity at low mold temperatures in the injection molding process.

Dynamic melt rheology. II: Re‐examining the relationship of g′ in oscillatory rheometry to the melt elasticity

AbstractIn oscillatory rheometry, since the dynamic storage modulus (G′) represents the elastic component of the viscoelastic melt, it has been a rather common practice to associate it with the melt elasticity. Although this assumption might be valid in many instances, there can be exceptions as well. In the present study, we have chosen polypropylene/talc system to demonstrate an exception. For example, the melt elasticity decreases with increasing talc content as revealed by extrudate die swell, entrance pressure drop, and elastic compliance measurements; the opposite trend being reflected by G′. We can envision similar exceptions when stiffening agents are added to a polymer melt, e.g., rigid rod molecules. We are suggesting that G′ represents the elastic modulus or stiffness of the melt, which in certain situations might not reflect elasticity, i.e., the ability of a melt to recover from a deformation. The implication of the present manuscript is that caution be exercised when relating G′ to the melt elasticity of a polymer.

Identification of Elucamide as an Organic Compound which Affects Mechanical Properties of Poly (vinyl chloride)–Inorganic Filler Binary Composite System

Abstract The mechanical properties (yield strength) were measured for poly (vinyl chloride)–inorganic compound binary composite systems. Among them, only the PVC-talc system did not show the decreasing yield strength with increasing talc content. Elucamide was isolated from talc and identified as an organic compound which can provide inhibitory action of such a decreasing yield strength.

Effect of mineral fillers in low concentration on the mechanical properties of polymeric materials. Part 2: Fatigue of polypropylene, kinetic aspects

Injection moulded polypropylene samples containing low concentrations of talc, mica or wollastonite filler were fatigue tested in the flexural mode, at constant strain amplitude and 10 Hz frequency, and the induced stress, dissipation modulus, dissipated energy per cycle and surface temperature were recorded. Scanning electron microscope observations were made on fractured surfaces. Fatigue is characterized by self-heating until an equilibrium temperature close to 120°C for the highest strain amplitude. The onset of cracking can be easily detected by an abrupt decrease of the stress or dissipated energy. The cracks propagate over a few hundred micrometres from their initiation site (in the subcutaneous region), and then stop when 20 to 50% of the whole volume is damaged. The samples remain in this state for more than 95% of their lifetime and then undergo sudden rupture. The mineral fillers increase the energy dissipation (in the undamaged state) and accelerate sample failure. This latter involves two distinct kinetic regimes. Local (stress concentration effects, particle/matrix debonding) as well as macroscopic effects (narrowing effect of fillers on the processing-induced sample skin) can explain the disfavourable role of mineral fillers in fatigue.

Effect of mineral fillers in low concentration on the mechanical properties of polymeric materials. Part 1: Static and fatigue fracture of polypropylene, qualitative aspects

Injection moulded polypropylene samples containing low concentrations of talc, mica or wollastonite fillers were studied by differential scanning calorimetry, scanning electron microscopy (SEM), and static and dynamic (fatigue) flexural testing. All the fillers under study displayed a nucleating effect on crystallization. This effect is probably responsible for a decrease of the macromolecular orientation, especially in the ‘shear zone’. The most noticeable change in static flexural properties was an increase (50%) of the ultimate stress, presumably due to a change of fracture mechanism induced by the presence of mineral particles. The mineral particles also induced a decrease of the flexural fatigue lifetime. This effect can be attributed directly to the initiating effect of mineral particles on cracking, but also indirectly to a change of skin-core structure as a result of filler nucleating effects during processing. Three crack propagation modes were observed by SEM: matrix/filler debonding, partial debonding with crack reinitiation at the particle edge, and linear propagation with particle rupture. However, the mode of crack propagation seemed to have little influence on the fatigue lifetime, which was essentially controlled by the number of particles per unit volume.

Studies on polypropylene composites filled with talc particles

Tensile and impact properties of talc-filled isotactic polypropylene composites are investigated at 0–60 wt% filler contents. Tensile modulus registered an increase whereas tensile yield strength and strain-at-break decreased with increasing filler content. Mechanical restraint imposed by the talc particles on the molecular mobility or deformability of polypropylene explained the increase in modulus and decrease in strain-at-break while decrease in tensile yield strength was attributed to decreased crystallinity and formation of stress concentration points around the filler particles. Izod impact strength decreased with increased talc content. Surface modification of talc with a titanate coupling agent LICA 38 enhanced the filler-polymer interaction, further modifying the composite properties consequent upon significant decrease in the stress concentration. Scanning electron microscopic studies revealed better dispersion of surface-modified filler particles in the polymer matrix.

Hydrothermal alteration haloes and enlarged soil anomalies over concealed talc bodies, southwestern Montana

Anomalous concentrations of talc have been found in residual soil associated with buried and blind talc bodies in southwestern Montana. In order to better understand the intensity and distribution of the residual talc, rock samples obtained by means of drilling have been studied. In general, except for massive talc, the rock is calcitic or dolomitic marble. In the weathering environment, the carbonate is leached away leaving the insoluble material as residual soil. This being the case, the minerals of primary interest are in the acid insoluble portion of the drilling samples. X-ray diffraction analysis shows talc to comprise 50% or more of the acid insoluble residue obtained from the marble. Talc and chlorite occur in some parts of the zone in sufficient quantities to be visually identified in the hand samples. In addition to talc and chlorite, minor amounts of chlorite/smectite and corrensite-type mixed-layer minerals occur randomly. The outer zone shows talc averaging less than 20% of the insoluble. Generally an amount of smectite±vermiculite equal to that of talc is present. Talc and other layer-silicate minerals cannot be identified in hand sample. The alteration zonation appears to be compatible with origin by hydrothermal fluids having decreasing temperature away from the talc zone. In deposits studied, the size of the alteration zones appears to be directly related to the size of the talc body. Because the insoluble minerals end up in the residual soil as a result of weathering and because the analytical procedures for Montana soils involve nonfractionated bulk samples, a large zone of talc-rich residual soil will be found to overlie and surround most buried or blind bodies suggesting a much larger body than actually present. However, such soil zones also offer sizeable targets for exploration.

The use of soil anomalies to locate concealed talc bodies

Residual carbonate-rich collected from a site thought to overlie a talc body were analyzed by X-ray diffraction to determine which of five methods of pre-treatment or calculation is most efficient in showing the positive talc anomaly. A talc distribution map was plotted for each method with the following results: (1) the map of percent talc acid-treated samples showed one large anomaly. (2) The map of percent talc for non-acid-treated samples showed two smaller positive anomalies similar in area of coverage to that obtained for acid treated samples. (3) Intensities corrected for the amount of carbonate, yield a map with anomalies similar to acid treatment. (4 and 5) Data obtained for carbonate-containing samples analyzed for absolute talc intensity (uncorrected for carbonate) or from heat-treated (carbonate corrected) samples were of less value in finding areas of talc concentrations. Consequently, maps obtained by calculating percentage values for talc yield the best results. Acid-treated samples provide the greatest accuracy but take the longest time to prepare; whereas, non-acid-treated samples provide good results at a substantial saving of time.

Effect of talc surface treatment on the mechanical properties of composites based on PP/LDPE blend matrices

AbstractA study has been made of property optimization of a composite based on low density polyethylene and polypropylene (PP) blend matrices with talc modified by a titanate coupling agent. Analysis shows that the flexural properties improve with increasing content of both talc and polypropylene. However, the tensile moduli show a different behavior. Tensile strength is hardly affected by the filler content at PP percentages in the matrix above 50 percent. The surface modified talc gives rise to higher mechanical properties than the unmodified talc. This improvement is more noticeable as talc and PP percentages in the composite is increased. Scanning electron microscopy has shown the effect of the coupling agent at the filler/polymer matrix interphase and the greater affinity between talc and polypropylene.

Talc deposition and effects after 20 days of repeated inhalation exposure of rats and mice to talc

The relationship between the inhalation exposure concentration of talc and the resulting lung burdens and histologic lesions was studied using groups of 20 F344/Crl rats and 20 B6C3F mice (10 male and 10 female) exposed to one of three concentrations of asbestos-free talc for 6 hr/day, 5 days/week for 4 weeks. Controls were exposed to filtered air using the same schedule. The pulmonary retention of talc and the development of pulmonary pathology were evaluated. The mass median aerodynamic diameter (MMAD) of the talc aerosol was 3.0 microns with a geometric standard deviation (sigma g) of 1.9. The mean exposure concentrations for rats were 0, 2.3, 4.3, and 17 mg talc/m3. Lung burdens in rats averaged 0, 0.07, 0.17, and 0.72 mg talc/g lung after the 20-day inhalation exposure; thus, the amount retained in the lung per unit of exposure concentration increased with increasing concentration. Mean exposure concentrations for the mice were 0, 2.2, 5.7, and 20.4 mg of talc/m3, which resulted in lung burdens of 0, 0.10, 0.29, and 1.0 mg talc/g lung; thus, the relationship between exposure concentration and the amount retained in the lung was approximately constant. Lung burdens from this study were used to project lung burdens that would result from longer exposures of rodents and man. No clinical signs were observed in the rats or mice prior to sacrifice 24 hr after the last exposure day. Histologic alterations in lung tissue consisted of only a modest, diffuse increase of talc-containing, free macrophages within alveolar spaces in both rat and mouse groups exposed to the highest level of talc for 20 days. A model simulating chronic talc inhalation exposure of rats and mice predicted lung burdens of 2-3 mg talc/g lung (wet wt) if animals were exposed to 17 mg talc/m3 for 2 years, and deposition and clearance of talc were unchanged by continued exposure. A potential limitation in this modeling is that if clearance of talc is delayed by continued exposure, the accumulated talc lung burdens would be higher than those projected by the simulation model. Humans exposed to aerosols of respirable talc are projected to accumulate much higher lung burdens than would occur in rodents exposed to the same aerosol, because humans have a higher estimated deposition fraction and slower estimated clearance of the deposited talc dust. Equilibrium lung burdens of greater than or equal to 2 mg talc/g lung were predicted for human exposures at or near the TLV for talc.

Dissolution Rate and Bioavailability of Spironolactone Tablets: Effect of Various Technological Factors

AbstractThe effects of the magnesium stearate, talc and gelatin contents of spironolactone tablets on dissolution rate and bioavailability of the drug have been evaluated. The dissolution test results for eight formulations corresponding to a 2×2×2 factorial design showed dissolution rates to be chiefly dependent on gelatin content. Testing the bioavailability of the eight formulations using a balanced incomplete block design revealed no evidence of bioinequivalence, but in view of the possibility that the absence of significant differences had been due to the large number of formulations (and consequent lack of sensitivity on the part of experimental design) three representative formulations were re-tested using a 3×3 Latin square design. The results confirmed those of the balanced incomplete block study. Use of the balanced incomplete block design is advocated for bioavailability studies in which a large number of formulations are to be compared.

Nepheline syenite-talc low temperature vitrified bodies

Compositions in the system, talc-nepheline syenite-quartz-china clay (Kaolinite) were studied. The content of nepheline syenite was kept constant, 25%, while talc was added in the range of 5–15% at the expense of quartz. This study extended the range of fusible talc/nepheline mixes from 15 to 28%. The content of talc dissolved in the glassy phase is limited to 3–4%. Addition of talc to the compositions caused the dissolution of mullite and increased the glassy phase. The addition of nepheline syenite counteracts the effect of talc on the thermal expansion coefficient of the bodies.