Source lei little knowledge | calcium carbonate so much, how to choose?
Application of 1. Calcium Carbonate in Plastics
Light calcium carbonate is widely filled in polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), acrylonitrile-butadiene-styrene copolymer (ABS) and other resins. The addition of calcium carbonate plays a certain role in improving some properties of plastic products to expand their application range. Calcium carbonate can reduce resin shrinkage, improve flow property and control viscosity in plastic processing.
The addition of calcium carbonate plays a skeleton role in plastic products, which plays a great role in the stability of the size of plastic products. It can increase the volume of plastic, reduce product cost, improve the dimensional stability of plastic, improve the hardness and rigidity of plastic, improve the processing performance of plastic, improve the heat resistance of plastic, improve the astigmatism of plastic and so on. The strength of the engineering plastics produced by it exceeds that of steel in some aspects, and the hardness is close to jade. It has the characteristics of wear resistance, high temperature resistance and aging resistance. It can be widely used in electronics, aerospace, precision machinery, instruments, automobile industry and other fields.
Characteristics of 2. calcium carbonate
Calcium carbonate is widely used in plastics, and it is not accidental that the plastics industry attaches great importance to it. Compared with other non-metallic mineral powder materials, calcium carbonate has obvious advantages:
1) The price is cheap
Whether it is heavy calcium or light calcium in a variety of non-mineral powder materials is the lowest price, that is to say, any non-mineral powder materials only try to replace calcium carbonate as a plastic filler, rather than highlighting the characteristics of the powder material itself, it is meaningless.
2) good color, easy coloring
And can do light color plastic products. The disadvantage is that the color of the colored plastic products is not bright enough and is acceptable in most cases.
3) Low hardness
Its Mohs hardness is 3, which is far lower than the hardness of steel used in manufacturing and processing machinery and molds (such as nitrided steel, high-speed steel), so the plastic is filled with the contact equipment parts (screw, screw barrel, etc.) and the mold.
4) Good thermal and chemical stability
When the thermal decomposition temperature of calcium carbonate is above 800 ℃, thermal decomposition will not occur at all plastic processing temperatures (below 300 ℃). Calcium carbonate is a strong alkali weak acid salt, in addition to the acid medium, its chemical stability is good.
5) Easy to dry, no crystal water, adsorbed water is easy to remove by heating.
6) Non-toxic, non-irritating, tasteless
In particular, my country's calcite, marble, and limestone resources are rich, and there is a large choice. Most of the resources are of good quality, especially the content of heavy metals is extremely low, which meets the national health level requirements.
3. how to choose good calcium carbonate?
After understanding the characteristics of calcium carbonate itself and the influence of calcium carbonate on the performance of filled plastics, it is relatively simple to put forward the basic requirements of calcium carbonate for plastics.
1. The content of calcium carbonate should be high, and the compounds of silicon, iron and other elements should be as low as possible,
2, the content of harmful heavy metal elements should be more strict requirements.
3, whiteness should be as high as possible
Whether heavy calcium or light calcium, its whiteness mainly depends on resources. For plastic materials, the degree of whiteness does not affect the mechanical properties and processing properties of the material, but the high degree of whiteness gives people a good feeling, and the same performance has a competitive advantage.
5. The lower the oil absorption value, the better
The maximum amount of butylene phthalate (DBP) that can be absorbed by 100g of powder material is referred to as the oil absorption value of the material.
For some plastic products, such as soft polyvinyl chloride, artificial leather, cable materials, etc., need to use plasticizers, calcium carbonate oil absorption value is higher, the more easy to plasticizer adsorption into the filler, so that it loses the role of plasticized resin, so as to achieve a certain degree of softness need to increase the amount of plasticizer, resulting in rising costs. The oil absorption value can be reduced by surface treatment of calcium carbonate to coat the surface of calcium carbonate particles. For example, the oil absorption value of light calcium carbonate treated with coupling agent can be reduced from 92.91g/100g to 49.33g/100g.
6. The fineness should be appropriate, not the finer the better, and the particle size distribution should also be determined according to needs.
How, calcium carbonate, plastic, material, plastic products, can, function, process, fill, improve
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Kaolin is a non-metallic mineral, which is a kind of clay and clay rock mainly composed of kaolinite clay minerals. Because it is white and delicate, also known as white earth. It is named after Gaoling Village, Jingdezhen, Jiangxi Province.