Is light calcium or heavy calcium chosen as filler in the plastic industry?

Calcium carbonate holds an unshakable position in plastic filling and modification materials. Calcium carbonate is further divided into light calcium carbonate and heavy calcium carbonate. So, in plastic products, should we choose light calcium or heavy calcium? The editor will discuss this issue with everyone.

Conceptual differences

Heavy calcium is formed by mechanical crushing and sorting of ores, while light calcium is formed by calcination, digestion, and re-carbonation of ores. The true density of heavy calcium is 2.6-2.9g/cm3, while that of light calcium is 2.4-2.6g/cm3.

The use of heavy and light calcium in plastic products is similar to that of rubber products. Some manufacturers have reported that using 400 mesh heavy calcium instead of light calcium under the same conditions has a clear advantage for products sold by weight, but if products are sold by length, area, or quantity, heavy calcium does not have an advantage over light calcium.

For example, for pipes of the same weight, if the filling amount is the same, the resulting product length is different. Filling with heavy calcium is a few thousandths shorter than filling with light calcium, which accumulates to be quite large. For artificial leather or synthetic leather measured by area, the difference in area can also be felt, so plastic product processing factories do not easily give up using light calcium.

Differences in application effects

The use of heavy and light calcium in plastic products is similar to that of rubber products. Some manufacturers have reported that using 400 mesh heavy calcium instead of light calcium under the same conditions has a clear advantage for products sold by weight, but if products are sold by length, area, or quantity, heavy calcium does not have an advantage over light calcium.

The use of heavy and light calcium in plastic products is similar to that of rubber products. Some manufacturers have reported that using 400 mesh heavy calcium instead of light calcium under the same conditions has a clear advantage for products sold by weight, but if products are sold by length, area, or quantity, heavy calcium does not have an advantage over light calcium.

Do you use heavy calcium or light calcium? It cannot be generalized

From an academic perspective, there are many differences between heavy calcium and light calcium, mainly manifested in different crystals, surface areas, and oil absorption values. The form in which heavy or light calcium exists in the plastic matrix, as well as the interface state between these particles and resin macromolecules, directly affects the mechanical function of the material.

The use of heavy calcium or light calcium in plastic products cannot be generalized. When choosing, one should fully leverage their respective advantages and consider both technical and economic factors comprehensively.

For example, the production of polyvinyl chloride artificial leather can be divided into scraping coating method, rolling method, and extrusion method according to the manufacturing process. However, the scraping coating method uses polyvinyl chloride paste resin and requires the addition of a large amount of plasticizer. The oil absorption value of light calcium is 4-5 times higher than that of heavy calcium, so using light calcium requires more plasticizers to achieve the same flexibility. If the amount of plasticizer used can be reduced, using heavy calcium may be more cost-effective economically.

For example, in unidirectional stretched products such as polypropylene woven bags, woven fabrics, and packaging belts, there was no significant difference in length when using heavy calcium and light calcium as fillers. After research, it was found that the filler particles were mostly located in the gaps between the stretched macromolecules. After several times of stretching and rapid cooling, the morphology of the macromolecules was quickly frozen, while the true density of light calcium and heavy calcium was almost the same, so the impact on the final length of the product was not significant. On the other hand, heavy calcium has better processing fluidity and a much lower price compared to light calcium, so it occupies a dominant position in this unidirectional stretching product.

In addition, the molding and processing technology of plastic door and window profiles in China was introduced from abroad. Along with the introduction of production lines, the product formula was also introduced, with a filler of light calcium and a dosage of 8-10 Phr. It should be pointed out that the formula provided by foreign countries is scientific, and the purpose of adding calcium carbonate is to improve the overall performance of the profile material, rather than using cheap raw materials to reduce costs. Replacing light calcium with heavy calcium inevitably faces several problems:

① What particle size range of heavy calcium is used to replace the light calcium being used?

② Can the material properties of the profile not change significantly after equal substitution? Is there any impact on the appearance of the product?

③ Should the processing equipment, head molds, and process conditions be adjusted accordingly after equal substitution?

④ After equal substitution, can the material flow resistance (reflected in the variation of screw torque) be reduced due to the good processing performance of heavy calcium, thereby saving energy consumption or increasing production speed?

⑤ Is it cost-effective to compare gains and losses?

The production of plastic profiles is gradually moving towards large-scale and mass production. The substitution and replacement of raw materials are related to the quality and stability of a large number of products, so plastic product processing plants will not easily replace a certain component in the formula.

How can calcium carbonate be better applied to the plastic industry?

Calcium carbonate has become one of the indispensable and important raw materials in the plastic industry. The rapid development of the calcium carbonate industry provides material conditions for the plastic industry to choose and explore. Its good application in plastic materials has also guided the development of the calcium carbonate industry.

Here, we hope that powerful enterprises in the calcium carbonate industry not only need to make good calcium carbonate products but also further develop new plastic materials and products using calcium carbonate as the main raw material, rather than simply producing a certain product, which must be used by the plastic industry.

In addition, it should be said that there are experts and technical talents in the plastic industry in the field of filling modification. However, for many plastic enterprises, there are still many who do not have specific knowledge of using fillers and filling modification. If we in the calcium carbonate industry understand how to use our products in plastic processing products and develop deep-processed products with calcium carbonate as the main raw material, we can sell calcium carbonate while exporting the application technology of calcium carbonate, China’s calcium carbonate products will have broader application prospects.