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.
Calcium carbonate plastics (resin) generally do not enhance, and calcium carbonate particles can often be infiltrated by the resin, so the normal effect of calcium carbonate addition is to increase the rigidity of the resin, and the elastic modulus and hardness also increase. As the amount of addition increases, both the tensile strength and the extreme elongation decrease.
Different calcium carbonates have different hardnesses and different hardnesses.
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 can reduce the shrinkage, linear expansion coefficient and creep properties of plastic products, creating 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 calcium-plastic paper, 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.
The addition of calcium carbonate to the cable material has a certain insulating effect, 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. Calcium carbonate is used as a filler or extender.
At this stage, the main goal is to add calcium carbonate to reduce the cost of plastics. As the surface properties of calcium carbonate improve and the shape and particle size are controllable, 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, and its purpose of use is mostly to increase the PVC products to achieve the purpose of reducing production costs.
At present, there are mainly two kinds of calcium carbonate used in the production and processing of PVC products. One is that natural limestone is pulverized into different fineness of calcium carbonate by mechanical pulverization method, such as by Raymond mill. This 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 to select limestone with high grade to be calcined, decompose it into calcium oxide, and react with water to form calcium hydroxide, then pass carbon dioxide, and precipitate to form calcium carbonate. This calcium carbonate is called light calcium carbonate. A small amount of light calcium carbonate can increase the tensile strength of PVC products. The quality of light calcium carbonate is determined by the grade of natural calcium carbonate, and the chemical reaction conditions such as calcination and the fineness of classification are also 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, the addition of calcium carbonate will reduce the quality of the product, but if the inferior calcium carbonate is added, the quality of the product will be greatly reduced. Adding the same amount of calcium carbonate, high quality calcium carbonate and inferior calcium carbonate will make the performance of PVC products completely different. Usually, some manufacturers or distributors will mix light calcium carbonate with heavy calcium carbonate at a price of light calcium carbonate, which can occur in various fineness of light carbonic acid.
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