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How To Distinguish GCC and PCC? Real Stuff

Posted: 2018-10-15

  •  At present, the main industrial calcium carbonate products on the market are light calcium carbonate (PCC) and heavy calcium carbonate (GCC), which not only have certain similarities in mineralogical characteristics, but also overlap in their application fields, for example. The 5-0.1 μm ultrafine heavy calcium carbonate and the light calcium carbonate can be substituted for each other at about 90%.

    PCC light calcium carbonate powder.jpg

    PCC Light Calcium Carbonate Powder

    GCC heavy calcium carbonate powder.jpg

    GCC Heavy Calcium Carbonate Powder

    Therefore, the problem of distinguishing between light calcium carbonate and heavy calcium carbonate has been plaguing most users. Today, we introduce the difference in 12 aspects, such as production mode, oil absorption value, particle shape and application performance.

    1. Production methods

    ♦ Heavy calcium carbonate is mainly a powder material obtained by mechanical grinding of natural minerals such as calcite, marble, limestone, white peony and white marble;

    ♦ Light calcium carbonate is mainly a powder material obtained by calcining, digesting, carbonizing, dehydrating, drying and grading.

     Calcium carbonate powder making machines:


    2. Bulk density
    The difference in product bulk density is the most obvious difference between heavy calcium carbonate and light calcium carbonate.

    ♦ Heavy calcium carbonate products have a high bulk density, generally 0.8-1.3g/cm3;

    ♦ Lightweight calcium carbonate products have a low bulk density of 0.5-0.7 g/cm3, and some nano-calcium carbonate products can even have a bulk density of about 0.28 g/cm3.

    3. Settling volume
    The sedimentation volume is the volume that the unit mass of calcium carbonate oscillates in 100 mL of water and is allowed to stand for 3 h. The larger the sedimentation volume, the smaller the particle size of the product, the lighter the density, and the higher the product grade.

    ♦ The sedimentation volume of heavy calcium carbonate is 1.1-1.4mL/g;

    ♦ The sedimentation volume of light calcium carbonate is 2.4-2.8 mL/g, and the sedimentation volume of nano-light calcium carbonate is 3.0-4.0 mL/g.

    4. Specific surface area
    The average particle size of calcium carbonate is intrinsically linked to its specific surface area, and the average particle size can be accurately determined by the specific surface area.

    ♦ The specific surface area of ​​ordinary heavy calcium carbonate is generally about 1 m2 / g, and the specific surface area of ​​heavy fine calcium carbonate is 1.45 ~ 2.1 m2 / g;

    ♦ The ordinary light calcium carbonate has a specific surface area of ​​about 5 m 2 /g, and the light fine calcium carbonate has a specific surface area of ​​27 to 87 m 2 /g.

    5. Oil absorption value
    In practical applications, most of the fillers use the oil absorption value to roughly predict the resin's demand for the resin, that is, the oil absorption value has important guiding significance for the selection of the filler.

    ♦ Heavy calcium carbonate has a low oil absorption value due to its large particle size, smooth surface and small specific surface area, generally 40-60mL/100g;

    ♦ Light calcium carbonate particles are fine, rough surface and large specific surface area, so the oil absorption value is high, generally about 60-90mL/100g.

    6. Whiteness

    ♦ Heavy calcium carbonate is generally 89% to 93% white due to relatively high levels of impurities, and very few products can reach 95%;

    ♦ Light calcium carbonate products have high purity, so the whiteness is generally 92% to 95%, and some products can reach 96% to 97%.

    7. Moisture content

    ♦ The weight of heavy calcium carbonate products is generally 0.2% to 0.3%, the moisture content is relatively low, and it is also relatively stable. Some high-grade products can even reach about 0.1% moisture;

    ♦ Ordinary light calcium carbonate products have a moisture content of 0.3% to 0.8%, sometimes with some fluctuations and are not stable.

    8. Particle size

    ♦ The content of heavy calcium carbonate products is 0.5~45μm. According to its original average particle size (d), it is divided into: coarsely ground calcium carbonate (>3μm), finely ground calcium carbonate (1-3μm), ultrafine carbonic acid. Calcium (0.5-1 μm). The smaller the particle size of the product, the higher the price. At present, there is no industrially produced nano-scale heavy calcium carbonate, except that some fine calcium products contain a very small amount of particles having a particle size of about 100 nm.

    ♦ The size of ordinary light calcium carbonate products is generally 0.5~15μm, and the size of nanometer calcium carbonate is generally 20~200nm. Light calcium carbonate can be divided into: granular calcium carbonate (>5μm), fine powder calcium carbonate (1-5μm), fine calcium carbonate (0.1-1μm), ultrafine calcium carbonate (0.02- according to its original average particle size (d). 0.1 μm), ultrafine calcium carbonate (<0.02 μm).

    9. Particle shape

    ♦ The powder characteristics of heavy calcium carbonate are: the shape of the particles is irregular, and the particles have a certain angular and rough surface; the particle size is different, the particle size distribution is wider, and the particle size is larger. Fragmentation and refinement do not change the crystal form of heavy calcium carbonate. Generally, calcite heavy calcium carbonate is hexagonal crystal type, and marble heavy calcium carbonate is cubic crystal type, which is mainly related to the origin.

    ♦ The powder of light calcium carbonate is characterized by regular particle shape, which can be regarded as a monodisperse powder; the particle size distribution is narrow. Light calcium carbonate can be classified into a spindle shape, a cuboid shape, a needle shape, a chain shape, a spherical shape, a sheet shape, and a rhombus shape depending on the shape of the crystal grains. Spindle-shaped calcium carbonate is the most common crystal form of light calcium carbonate, with an average major axis diameter of 5-12 μm and an average minor axis particle size of 1-3 μm; the average diameter of acicular calcium carbonate is 0.01-0.1 μm. The average aspect ratio is 5-100; the average particle size of the chain calcium carbonate is 0.01-0.1 μm, and the average aspect ratio is 10-50; the average particle diameter of the spherical calcium carbonate is 0.03-0.05 μm; the average particle size of the cubic calcium carbonate It is 0.02-0.1 μm; the average particle diameter of flaky calcium carbonate is 1-3 μm.

    10. Taste
    For food grade calcium carbonate, product taste is also an important indicator. Light calcium carbonate has a lime-like taste due to incomplete calcium oxide reaction. For example, filling biscuits has a horrible taste, while heavy calcium carbonate does not.

    11. Comparison of mineral economics
    Powder preparation cost: the conventional cost is equivalent, at the same level of competition, but if additional environmental control costs and resource waste rate, the expansion cost of light calcium carbonate is higher than that of heavy calcium carbonate;
    Environmental balance: In addition to noise, heavy calcium carbonate production has no “three wastes” emissions, and the environment is easy to coordinate and control; light calcium carbonate production emits “three wastes”, especially combustion exhaust gas, and the total environmental balance is low.
    Resource utilization rate: Heavy calcium carbonate is easy to comprehensively utilize mineral resources. Light calcium carbonate is difficult to control the rational utilization rate of mineral resources by virtue of its chemical processing capability.

    12. Application performance
    In the application process, heavy calcium carbonate products are mainly used in the papermaking, rubber and plastic industries, and the filling amount is generally large, mainly as a volume filler, which reduces the manufacturing cost of the applied products.
    Light calcium carbonate products are widely used in a wide range of applications. The main application areas are plastics, rubber, paints, adhesives, cigarette papers, inks, etc., which are mainly volume-filled, while nano-calcium carbonate products are often used as a modification in the application process. For functional fillers such as sex or reinforcement, the filling amount is generally small. Light calcium carbonate products

    (1) Papermaking: After the promotion of neutral sizing in papermaking, the demand for calcium carbonate has increased sharply, but the light calcium carbonate has a high oil absorption value and a large amount of glue, which is detrimental to the sizing effect; in addition, the water retention of light calcium carbonate Strong, added to the paper, the paper strength is poor compared to heavy calcium carbonate.
    However, for the production of cigarette paper, light calcium carbonate is superior to heavy calcium carbonate. Calcium carbonate for cigarette paper at home and abroad is mainly composed of light calcium carbonate, especially spindle-shaped light calcium carbonate. Because of its crystal shape, it determines the accumulation and crossover of particles, which will create a bridge effect, which is looser and more paper-forming. It is advantageous for air permeability, opacity and whiteness, and is the best choice for calcium carbonate for high-grade cigarette paper.

    (2) Plastics: Ordinary light calcium carbonate is too light in some plastics due to its high oil absorption value. It is difficult to mix, and it is difficult to increase the amount of addition. It can only be used as a general extender. Therefore, heavy calcium carbonate is commonly used in woven products, pipes, injection molding or hollow articles.

    (3) Rubber: Light calcium carbonate can increase the rubber volume, improve the vulcanization performance of the rubber, and play a semi-reinforcing or reinforcing effect due to the small particle size and large sedimentation volume.

    (4) Others: In the aspects of architectural coatings, putty, felt packaging, feed, etc., because of the coarser particle size, the demand is high. Therefore, heavy calcium carbonate is mainly used.

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