There are several types of common calcium carbonate powders: heavy calcium carbonate (heavy calcium), active calcium carbonate (active calcium), light calcium carbonate (light calcium), and nano calcium carbonate (nano-calcium). Heavy calcium carbonate, also known as ground calcium carbonate (GCC for short), is obtained by mechanically pulverizing natural calcium carbonate ore (such as calcite, marble, etc.). Light calcium carbonate, also known as precipitated calcium carbonate (PCC), is produced by chemical processing. The sedimentation volume (1.1-1.9 mL/g/g) of the calcium carbonate powder which is mechanically pulverized by natural ore is smaller than the sedimentation volume (2.4-2.8 mL/g) of the light calcium carbonate produced by the chemical method, so it is called Heavy calcium carbonate. The meaning of active calcium carbonate: Activated calcium carbonate is obtained by modifying on the basis of ordinary calcium carbonate, so as to achieve the dual purpose of filling and modification in composite products. These modifications include modifications to the crystal morphology, particle size, particle size distribution, and surface properties of the calcium carbonate. To improve its overall performance. The preparation process of nanometer calcium carbonate is similar to that of light calcium, and is also produced by chemical method. The main difference is that the nanometer calcium crystal grains are finer and the crystal form is different from ordinary light calcium.
Second, the role of calcium carbonate powder in the plastic products industry
1. Improve the stability of plastic products
The addition of calcium carbonate plays a skeleton role in plastic products and has a great effect on the dimensional stability of plastic products.
2, improve the hardness and rigidity of plastic products
In plastics, especially soft polyvinyl chloride, the hardness increases with the amount of calcium carbonate, and the elongation decreases with increasing hardness. Calcium carbonate with fine particles and large oil absorption has a large growth rate of hardness. On the contrary, calcium carbonate with a small crude oil absorption value has a small hardness growth rate of plastic. In soft polyvinyl chloride, the hardness growth rate of heavy calcium carbonate is the smallest, and precipitated calcium carbonate (light) is the second. The plastic (resin) to which calcium carbonate is added generally does not have a reinforcing effect, and the particles of calcium carbonate are often infiltrated by the resin, so the normal action of the addition of calcium carbonate is to increase the rigidity of the resin and increase the modulus of elasticity and hardness. As the amount of addition increases, both the tensile strength and the extreme elongation decrease.
3, improve plastic processing performance
The addition of calcium carbonate can change the rheological properties of the plastic. Calcium carbonate powder is often added in a large amount, which helps it mix with other components and contributes to the processing of plastics. The addition of calcium carbonate, especially after the addition of the surface-treated calcium carbonate, can not only improve the hardness of the product, but also improve the surface gloss and surface flatness of the product. The addition of calcium carbonate powder can also reduce the shrinkage rate, linear expansion coefficient and creep property of plastic products, and create conditions for processing.
4, improve the heat resistance of plastic products
Adding calcium carbonate to a general plastic product improves heat resistance. For example, in polypropylene, about 40% of calcium carbonate is added, and heat resistance is improved by about 200C. When the filling ratio is ≤ 20%, the heat resistant temperature is increased by 8 to 130C.
5, improve the astigmatism of plastics
In plastic products, some products require whitening and opacity, and some hope to extinction. The addition of calcium carbonate can play a certain role in this aspect. Calcium carbonate with a whiteness of more than 90 has a significant whitening effect in plastic products. In combination with titanium dioxide and lithopone, the matte finish of plastic products is greatly improved. In low-density polyethylene (LDPE) and high-density polyethylene (HDPE) films, the addition of calcium carbonate can achieve astigmatism and matting, making it suitable for writing and printing. Calcium carbonate with better whiteness can also replace expensive white pigments.
6, the product can have some special properties
For example, calcium carbonate has a certain insulating effect added to the cable material, and the addition of calcium carbonate can improve the plating performance and printing performance of certain products. Fine or ultrafine calcium carbonate is added to polyvinyl chloride (PVC) and has a certain flame retardant effect.
7, reduce the cost of plastic products
The price of ordinary light calcium carbonate and heavy calcium carbonate is far lower than the price of plastic, and the addition of calcium carbonate will lower the cost of plastic products. The filling amount of calcium carbonate powder in common plastic products can be referred to the following table:
Third, the role of calcium carbonate powder in rubber products
1. Increase the volume and reduce the cost. Heavy calcium does not reinforce the rubber and even reduces the mechanical properties of the vulcanizate. However, it can improve the stiffness of the rubber, improve the electrical insulation, and reduce the shrinkage of the rubber. Its low cost is often used as a non-reinforcing filler to reduce the cost of production.
2, improve the performance of vulcanized rubber, to strengthen and semi-reinforcing. Active calcium carbonate has a spatial three-dimensional structure in rubber and good dispersibility. The ultra-fine active calcium carbonate forms a bond with the long chain of rubber in rubber mixing, which not only has good dispersibility, but also greatly enhances the reinforcing effect.
3. Calcium carbonate powder can also play some special effects in rubber processing, such as: adjusting hardness and processing performance.
Filling table for heavy calcium powder in common rubber products
The demand of the plastics and rubber industry has always been a stable source of market demand for the calcium carbonate powder processing industry. With the advancement of society, higher requirements have been placed on the traditional materials industry. The competition in the plastic rubber products market is also becoming more intense, and the demand for product performance improvement is very urgent. Calcium carbonate powder enterprises should comply with market requirements and increase investment in the research and development of new calcium carbonate powder products. The ultra-fine (nitrification) and surface modification technology of calcium carbonate powder is the current mainstream technology trend. Paying attention to technological progress, the traditional industry of calcium carbonate powder is still promising.
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