1, improve the stability of plastic products size The addition of calcium carbonate plays a skeleton role in plastic products and plays a significant role in the dimensional stability of plastic products.
2. Improve the hardness and rigidity of plastic products
In plastics, especially in soft PVC, the hardness increases with the amount of calcium carbonate added, and the elongation decreases with increasing hardness. Fine particles, calcium carbonate with large oil absorption value, the growth rate of hardness. On the other hand, calcium carbonate with small crude oil absorption values ​​has a small increase in hardness. In soft polyvinyl chloride, the hardness growth rate of heavy calcium carbonate is the smallest, and precipitated calcium carbonate (light weight) is the second.
Calcium carbonate plastics (resins) generally can not play a reinforcing role, calcium carbonate particles can often be infiltrated by the resin, so the normal role of calcium carbonate addition is to increase the stiffness of the resin, elastic modulus and hardness also increased. As the added amount increases, both the tensile strength and the extreme elongation decrease.
Different calcium carbonate, the amount of different, the hardness will be different.
3, improve the plastic processing performance
The addition of calcium carbonate can change the rheological properties of plastics. Calcium carbonate powder is often added in a large amount, which helps to mix it with other components, and also helps plastics processing.
The addition of calcium carbonate, especially after the surface-treated calcium carbonate is added, can not only improve the hardness of the product, but also improve the surface gloss and surface smoothness of the product.
The addition of calcium carbonate can reduce the shrinkage, linear expansion coefficient, and creep performance of plastic products, creating conditions for processing and forming.
4, improve the heat resistance of plastic products
In the general plastic products, calcium carbonate is added, and the heat resistance is improved. For example, in polypropylene, about 40% of calcium carbonate is added, and the heat resistance is increased by about 200C. When the filling ratio is ≤ 20%, the heat-resistant temperature is increased by 8 to 130C.
5, improve the plastic astigmatism
In plastic products, some products require whitening and opacity, and some hope to eliminate light. The addition of calcium carbonate can play a role in this regard.
The calcium carbonate with a whiteness of over 90 has a clear whitening effect in plastic products. With the combination of titanium dioxide and lithopone, the extinction of plastic products is greatly improved.
In calcium plastic paper, in the low density polyethylene (LDPE) and high density polyethylene (HDPE) films, the addition of calcium carbonate can achieve the effect of astigmatism and extinction, making it suitable for writing and printing.
The better whiteness of calcium carbonate can also replace expensive white pigments.
6, can make products have some special properties.
Calcium carbonate added in the cable material has a certain degree of insulation. The addition of calcium carbonate can improve the plating performance and printing performance of certain products.
Fine or ultra-fine calcium carbonate added in polyvinyl chloride (PVC), a certain degree of 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. The addition of calcium carbonate will reduce the cost of plastic products. Solid foreign claims that calcium carbonate is Filler or Extender.
At this stage, the main objective is to add calcium carbonate to reduce the cost of plastics. With the improvement of the surface properties of calcium carbonate and the control of the shape and particle size, calcium carbonate will gradually become a functional filler for reinforcing or imparting functionality.
Calcium carbonate is the most commonly used filler in the production and processing of PVC products. The purpose of its use is mostly to increase the number of PVC products in order to reduce the production cost.
At present, there are two kinds of calcium carbonate used in the production and processing of PVC products. One is the natural limestone that is crushed into different fineness calcium carbonates by mechanical grinding methods such as Raymond Mill. This kind of calcium carbonate is called heavy carbonic acid. Calcium, its quality is determined by the grade of natural limestone and its fineness. Reasonable use of heavy calcium carbonate can improve the heat resistance, rigidity, dimensional stability and processability of PVC products. The second is the selection of high-grade limestone calcined to decompose it into calcium oxide and react with water to form calcium hydroxide, which then passes through carbon dioxide and forms calcium carbonate after precipitation. This calcium carbonate is called light calcium carbonate. A small amount of light calcium carbonate can improve the tensile strength of PVC products. The quality of light calcium carbonate is determined by the grade of natural calcium carbonate, and the calcination and other chemical reaction conditions and classification fineness are also very important factors. The price of light calcium carbonate should be more than double that of heavy calcium carbonate of the same fineness.
In the processing of PVC products, adding a large amount of calcium carbonate will reduce the product quality, but if inferior calcium carbonate is added, the quality of its products will be greatly reduced. Adding the same amount of calcium carbonate, high quality calcium carbonate and inferior calcium carbonate will make the properties of PVC products very different.
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