Calcium carbonate not only reduces the raw material cost of plastic products, but also has the effect of improving certain properties of plastic materials. Research results show that different types of calcium carbonate, when used appropriately, can significantly enhance the performance of the base plastic. However, the specific distinction between lightweight calcium carbonate and heavy calcium carbonate has always been a problem for many users. Below, we will introduce the differences between these two types from various perspectives.
Production method
Heavy calcium carbonate is mainly a powder material obtained by mechanical grinding processing of natural minerals such as calcite, marble, limestone, chalk, and white marble.
Lightweight calcium carbonate is mainly obtained from limestone through processes such as calcination, digestion, carbonation, dehydration, drying, and classification. It is a powder material.
2. Bulk Density
The difference in product bulk density is the most obvious distinction between heavy calcium carbonate and light calcium carbonate.
The bulk density of heavy calcium carbonate products is relatively high, typically ranging from 0.8 to 1.3 g/cm³.
The bulk density of lightweight calcium carbonate products is relatively low, typically ranging from 0.5 to 0.7 g/cm³. Some nano calcium carbonate products have a bulk density as low as around 0.28 g/cm³.
3. Oil absorption value
Heavy calcium carbonate, due to its large particles, smooth surface and small specific surface area, has a relatively low oil absorption value, typically ranging from 15 to 35 mL/100g.
The lightweight calcium carbonate particles are fine in size and have a rough surface. They have a large specific surface area, thus having a high oil absorption value. Generally, it ranges from 60 to 90 mL/100g.
4. Whiteness
Heavy calcium carbonate has a relatively high content of impurities, so the whiteness of the product is generally between 89% and 93%. Only a very few products can reach 95%.
The lightweight calcium carbonate products have a high purity, so their whiteness is generally 92% to 95%, and some products can reach 96% to 97%.
5. Moisture Content
The moisture content of heavy calcium carbonate products is generally 0.2% to 0.3%. The moisture content is relatively low and stable. Some high-end products even have a moisture content of around 0.1%.
The moisture content of ordinary lightweight calcium carbonate products ranges from 0.3% to 0.8%, and it may sometimes fluctuate slightly, which is not very stable.
6. Particle shape
The powder characteristics of heavy calcium carbonate are as follows: the particle shapes are irregular, and the particles have certain sharp edges and rough surfaces; the particle sizes vary greatly, with a wide particle size distribution and larger particle diameters. Fragmentation and refinement will not change the crystal form of heavy calcium carbonate. Generally, calcite heavy calcium carbonate is of hexagonal crystal form, while marble heavy calcium carbonate is of cubic crystal form, mainly related to the origin.
The powder characteristics of lightweight calcium carbonate are as follows: the particles have a regular shape and can be regarded as monodisperse particles; the particle size distribution is narrow. According to the different shapes of the crystal grains, lightweight calcium carbonate can be classified into spindle-shaped, cubic, needle-like, chain-like, spherical, plate-like and rhombic, etc.
7. Taste
The lightweight calcium carbonate, due to incomplete calcium oxide reaction, retains a lime-like taste. When used to fill cookies, it will have an unpleasant smell. However, the heavy calcium carbonate does not have this issue.
8. Particle size
The particle size of heavy calcium carbonate products ranges from 0.5 to 45 μm. According to their original average particle size (d), they are classified as follows: coarse-ground calcium carbonate (> 3 μm), fine-ground calcium carbonate (1 - 3 μm), and ultra-fine calcium carbonate (currently the finest is approximately 1 μm).
Lightweight calcium carbonate is classified according to its original average particle size (d) as follows: ordinary light calcium and lightweight nano calcium. Ordinary light calcium (3-5 μm), and the original particle size of nano calcium carbonate (80-120 μm).
9. Specific Surface Area
Nowadays, for the finer heavy calcium carbonate products, such as those with a content of 60% at a particle size of 2 micrometers, the specific surface area can reach over 5 square meters per gram. Currently, the finest product can reach 12 square meters per gram.
The specific surface area of common lightweight calcium carbonate is generally around 5 m2/g, while that of lightweight fine calcium carbonate ranges from 27 to 87 m2/g.
10. Liquidity
From the perspective of fluidity, the microscopic structure of lightweight calcium carbonate is spindle-shaped. Moreover, its own oil absorption value is relatively high, allowing it to absorb components that promote fluidity in the formula, such as lubricants, plasticizers, coupling agents, and dispersants. Therefore, its fluidity is not as good as that of heavy calcium carbonate. Generally, if the addition amount exceeds 25 parts, it will seriously affect the fluidity.
Heavy calcium carbonate is in a granular form and can enhance fluidity (excessive addition will affect fluidity; the amount should be determined according to the formula). In the PVC pipe formula, if calcium carbonate is added in excess (more than 25 parts), for the sake of fluidity, it is best to use heavy calcium carbonate.
11. Price
The processing of heavy calcium carbonate is mainly achieved through mechanical crushing and grinding methods.
The production of lightweight calcium carbonate is achieved through chemical reaction precipitation. The latter process is much more complex and requires much stricter conditions. Therefore, for the same particle size, heavy calcium carbonate is generally more cost-effective than lightweight calcium carbonate. If the performance permits, heavy calcium carbonate can be chosen as it is more economical and cheaper.
12. Modification Function
The plastic processed with heavy calcium has better fluidity, and the plastic filled with smaller particle size of heavy calcium also performs better.
Lightweight calcium carbonate has better impact strength and rigidity. Generally, the surface of plastics made with light calcium is smoother, and the density is lower.
13. Controllability of Light Color
Hue refers to the main color tone of a color, while chroma refers to the secondary color. The key factor influencing hue is the difference in some trace impurities contained, and crystal form also has an impact.
14. pH value
The pH value of heavy calcium carbonate is 8 to 9.
The pH value of lightweight calcium carbonate is 9 to 10.
15. Comparison of Mineral Economics
The cost of powder production: The basic cost is similar and falls within the same competitive range. However, if additional environmental control costs and resource waste rates are taken into account, the cost of light calcium carbonate expansion is higher than that of heavy calcium carbonate.
Environmental balance degree: The production of heavy calcium carbonate does not generate noise and has no "three types of waste" emissions, making the environment easy to coordinate and control; the production of light calcium carbonate emits "three types of waste", especially with combustion exhaust gas, resulting in a lower overall environmental balance degree.
Resource utilization rate: Heavy calcium carbonate is conducive to the comprehensive utilization of mineral resources, while light calcium carbonate, due to its chemical processing capabilities, is not easy to control the rational utilization rate of mineral resources.
16. Application Performance
Heavy calcium carbonate products: Primarily used in industries such as papermaking, rubber and plastics, with a relatively large filling volume. They are mainly used as volume fillers to reduce the manufacturing costs of the products.
Lightweight calcium carbonate products: They have a relatively wide range of application fields, mainly including plastics, rubber, coatings, adhesives, cigarette paper, ink, etc. They are mainly used for volume filling. While nano calcium carbonate products are often used as functional fillers for modification or reinforcement during application, and are also used in high-filling application industries.
