Calcium carbonate is widely filled in resins such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), acrylonitrile-butadiene-styrene copolymer (ABS), and the addition of calcium carbonate can improve the Some properties of plastic products play a certain role in expanding its application range. In the processing of plastics, calcium carbonate can reduce resin shrinkage, improve rheology, and control viscosity.
1. The application of calcium carbonate in plastics
Calcium carbonate is widely filled in resins such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), acrylonitrile-butadiene-styrene copolymer (ABS), and the addition of calcium carbonate can improve the Some properties of plastic products play a role in expanding its application range. In plastic processing, calcium carbonate can reduce resin shrinkage, improve rheology, and control viscosity.
The addition of calcium carbonate plays a skeleton role in plastic products, and has a great effect on the stability of the size of plastic products. It can increase the volume of plastics, reduce product costs, improve the dimensional stability of plastics, increase the hardness and rigidity of plastics, improve the processing performance of plastics, improve the heat resistance of plastics, and improve the astigmatism of plastics. The engineering plastics produced by it are stronger than steel in some aspects, and the hardness is close to that of 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 industries and other fields.
The plastic industry is an important application field of calcium carbonate. Whether it is from the international or domestic situation, calcium carbonate is the most widely used filler in the plastic industry. Since the 21st century, the world’s plastic products have consumed about 1,500 inorganic non-metallic fillers. 10,000 tons, and calcium carbonate, due to its incomparable advantages over other fillers, accounts for about 70% of the various non-metallic fillers consumed, that is, more than 10 million tons.
2. Characteristics of Calcium Carbonate
Calcium carbonate is widely used in plastics, and it is not accidental that it is highly valued by the plastics industry. Compared with other non-metallic mineral powder materials, calcium carbonate has obvious advantages:
cheap price
Whether it is heavy calcium or light calcium, the price of various non-mineral powder materials is the lowest, that is to say, any non-mineral powder material is only trying to replace calcium carbonate as a plastic filler, rather than highlighting this powder material. By itself, it is meaningless.
Good color, easy to color
And can do light-colored plastic products. The downside is that the color of colored plastic products is not bright enough, which is acceptable in most cases.
low hardness
Its Mohs hardness is 3, which is far lower than the hardness of steel (such as nitrided steel, high-speed steel) used in manufacturing processing machinery and molds. Less wear and tear.
Good thermal and chemical stability
The thermal decomposition temperature of calcium carbonate is above 800°C, and thermal decomposition will not occur at all plastic processing temperatures (below 300°C). Calcium carbonate is a strong base and weak salt, and its chemical stability is good except in acidic medium.
Easy to dry, no crystal water, the adsorbed moisture can be easily removed by heating.
Non-toxic, non-irritating, tasteless
How to choose a 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 for 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 strictly required.
3. The whiteness should be as high as possible
Regardless of heavy calcium or light calcium, its whiteness mainly depends on resources. For plastic materials, the level of whiteness does not affect the mechanical properties and processing properties of the material, but high whiteness gives people a better feeling, and the same performance with high whiteness has more competitive advantages.
4. The lower the oil absorption value, the better
The maximum amount of butanediol phthalate (DBP) that 100g of powder material can absorb is called the oil absorption value of the material.
For some plastic products, such as soft polyvinyl chloride, artificial leather, cable materials, etc., it is necessary to use plasticizers. The higher the oil absorption value of calcium carbonate, the easier it is for plasticizers to be absorbed into the filler, so that it loses the plasticizing resin. Therefore, in order to achieve a certain softness, it is necessary to increase the amount of plasticizer, resulting in an increase in cost. By treating the surface of calcium carbonate and coating the surface of calcium carbonate particles, its oil absorption value can be reduced. 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.
5. The fineness should be appropriate, not the finer the better, and the particle size distribution should also be determined according to the needs
7. The activation or inactivation should be determined according to the needs of downstream users.