Calcium carbonate particles

Fig. 104.—Tension r at O = 1.5 for GR-S synthetic rubber containing various proportions of calcium carbonate (particle diameter 3900 mju), but vulcanized under otherwise identical conditions. The solid curve has been calculated according to Ed. (52) the broken curve by neglecting the third term in this equation. (Cohan. s)...

A combination of graded calcium carbonate particle sizes, a nonionic polysaccharide of the scleroglucan type, and a modified starch, has been claimed for use as a fluid loss formulations [915]. It is important that the calcium carbonate particles are distributed across a wide size range to prevent filtration... 

Scleroglucan, starch, modified calcium carbonate particles [915]... 

The monomer type and ratio change the adsorption properties of the polymer on the calcium carbonate particles. The type of end group (which depends on the polymerisation process) can also influence adsorption characteristics. 

Ageing is better for the coarser PCC grade. The observation that the finer the calcium carbonate particle size, the higher the tendency to gel is likely due to fine particles having greater surface area, thus having inadequate dispersant to cover the surface and provide particle stability. 

By using partially neutralised polymers, we increase the adsorption of the polymer on the calcium carbonate particle surface. More polymer being adsor-... 

With the paper industry requiring more and more sophisticated products from mineral producers and particularly finer and finer calcium carbonate particle size slurries, the need to improve dispersants is becoming a reality. The work described in this paper is the beginning of research on improved dispersants for preparation of PCC and GCC slurries and also other minerals. 

Understanding the adsorption mechanism of the polymer on calcium carbonate particles is also something important which should help the design of an improved dispersant. Increasing the level of adsorption of the polymer on particles will greatly enhance the dispersing efficiency. 

Christel, P. Li, S. M. Vert, M. Patat, J.L. (1993) Mataial for bone prosthesis containing calcium carbonate particles dispersed in a bioabsorbable polymaic matrix. Eur. Pat. Appl. EP 564,369, 6 Oct to INOTEB. Chem. Abstr., 1993, 119, 256592z. 

More recently, Lin and Masuda [47] measured the viscoelastic properties of polypropylene melts filled with small (0.15 pm) and larger (4.0 pm) calcium carbonate particles. The dynamic modulus and viscosity were found to rise with filler loading especially at low frequencies. With highly filled compositions (at... 

Hardikar, V.V., and Matijevic, E. "Influence of ionic and nonionic dextrans on the formation of calcium hydroxide and calcium carbonate particles". Colloids Surf. A 186(1-2), 23-31 (2001). 

Tensile properties of PVC filled with precipitated calcium carbonate particles having two different mean sizes were studied. The particles were porous agglomerates of spherical primary particles. 10-50 parts of the particles were mixed with 100 parts PVC and 3 parts lead stearate using a mixing roll. Tensile tests were carried out using dumbbell test specimens. 20 refs. 

Limestone (calcium carbonate) particles are stored in 50-L bags. The void fraction of the particulate matter is 0.30 (liter of void space per liter of total volume) and the specific gravity of solid calcium carbonate is 2.93. 

A suspension of calcium carbonate particles in water flows through a pipe. Your assignment is to determine both the flow rate and the composition of this slurry. You proceed to collect the stream in a graduated cylinder for 1.00 min you then weigh the cylinder, evaporate the collected water, and reweigh the cylinder. The following results are obtained ... 

A complete summary of the work done on the perplexing problem of the origin of particulate material in the sea can be found in Riley s review (69). His review of the work on the bubbling makes it clear that mechanisms other than bubbling can produce particulate material. For example, particles appear to develop more or less spontaneously by aggregation of smaller entities (70) and by the adsorption of dissolved organic material onto calcium carbonate particles (71). 

Turbidity removal by dolomite coagulation proceeded in a manner different from that of colour removal. Figure 4 relates the removal efficiency to the dosage of coagulant B. Thus, during coagulation of solution 1 which had an initial turbidity T = 0, the samples became turbid. This should be attributed to the precipitation of fine-crystalline calcium carbonate particles. When the dosage... 

Goodman AL, Underwood GM, Grassian VH (2000) A laboratory study of the heterogeneous reaction of nitric acid on calcium carbonate particles. J Geophys Res 105 29053-29064 Gorbimov BZ, Kakutkina NA (1982) Ice crystal formation on aerosol particles with a non-uniform surface. J Aerosol Sci 13 21-28... 

The final examples, taken from a range of possibilities, illustrate first the use of nanoparticles (in Fig. 29, dendrimers of two generations) on the morphology of calcium carbonate particles prepared in their presence. The larger dendrimer has a greater effect on the product whose particles size is much smaller than that prepared with the lower generation dendrimer. 

Huang, Y.C. ct al.. Adsorption of calcium ions from calcium chloride solutions onto calcium carbonate particles, Langmuir, 7, 1742, 1991. 

The dendritic structure portrayed in Figure 1 is not valid for the structure of paper coatings. The more regular packing of clay platelets, or calcium carbonate particles probably leads to a structure consisting of larger voids joined by smaller interstices. Equation (9) predicts that ink cannot penetrate by... 

Lodge et al. 1968) that the greater sulfate content of precipitation water in an arid environment is due to mineral dust particles and to the effect of evaporation below the cloud base. Soils in these areas contain calcium carbonate and calcium sulfate in significant proportions. Calcium carbonate particles in the air are transformed into calcium sulfate by reacting with sulfur dioxide. The process is an interesting interaction of natural and man-made trace constituents. 

It is the length of a particle divided by its diameter. For spherical or cubical particles, the aspect ratio equals to one. For calcium carbonate particles, the aspect ratio is typically 1-3. For talc, the aspect ratio is typically in the range of 5-20. For milled glass fiber, it is between 3 and 25. For mica, it is 10-70. For wollastonite, it is between 4 and 70. For chopped glass fiber, it is between 250 and 800. For natural fibers, such as cellulose, the aspect ratio can be from 20-80 to thousands. Low aspect ratio is below 10. However, the above figures are given for fillers not processed in a compounder and/or an extruder. Upon processing, aspect ratio can decrease from dozens and hundreds to as low as 3-10. 

Observations of the affected materials under the light microscope has shown that it is a microbial contamination, and the black spots are located on calcium carbonate particles (fillers) and rice hulls fibers. In some cases, the black substance covered calcium carbonate or rice hulls particles completely. 

Fig. 17.15 shows how the friction factor increased with time in a "sample" finned tube heat exchanger exposed to an air flowing through laden with calcium carbonate particles the apparatus shown in Fig. 17.14. It may be regarded as a typical curve obtained in the laboratory apparatus. During the experiments water at temperature in the range 10 - 90°C was passed through the tubes. The equipment allowed thermal performance and pressure drop to be measured. From Fig. 17.15 it can be seen that the friction factor rises asymptotically to a level 50%...

More recently, Kotek at al. studied the effects of untreated (denoted as Cl) and stearate-treated calcium carbonate particles (denoted as C2) of 1.3 p.m on the tensile properties of P-PP. Moreover, stearate-coated calcium carbonate particles of 0.075 p,m (denoted as C3) are also used (44). The p-nucleating agent employed is based on an amide of dicarboxylic acid. The critical concentration of p-nucleator needed to achieve 61% P-PP is 0.03 wt% on the basis of the XRD analysis. With further increase in the p-nucleator content to 0.1 wt% (supercritical), the p-PP content increases, but very slightly, to 65%. Furthermore, the K value also depends... 

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