Scope of application of calcium carbonate
Data ：2015-10-15 03:07View ：
The detailed explanation is as follows:
Calcium carbonate is widely used in filled polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), acrylic butadiene-styrene copolymer (ABS) and other resins. The addition of calcium carbonate has a certain effect on improving and improving certain properties of plastic products to expand their scope of application. In plastic processing, they can reduce resin shrinkage, improve rheology, and control viscosity. It can also play the following roles:
(1), improve the stability of the size of plastic products
The addition of calcium carbonate plays a role as a skeleton in plastic products, and it has a great effect on the stability of plastic products.
(2) Improve the hardness and rigidity of plastic products
In plastics, especially in soft PVC, the hardness gradually increases with the amount of calcium carbonate added, and the elongation decreases as the hardness increases. Calcium carbonate with fine particles and large oil absorption value has a large growth rate of hardness. On the contrary, the particles have a small crude oil absorption value of calcium carbonate, and the plastic hardness growth rate is small. In soft PVC, the hardness growth rate of heavy calcium carbonate is small, and precipitated calcium carbonate (light weight) is the second.
Calcium carbonate plastics (resins) generally cannot 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 rigidity of the resin and increase the elastic modulus and hardness. As the added amount increases, the tensile strength and the extreme elongation both decrease.
Different calcium carbonate, the amount of addition, the hardness will be different.
(3), improve 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 plastic processing.
The addition of calcium carbonate, especially after the addition of surface-treated calcium carbonate, can not only increase 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 rate, linear expansion coefficient and creep performance of plastic products, creating conditions for processing and forming.
(4), improve the heat resistance of plastic products
Adding calcium carbonate to general plastic products has improved heat resistance. For example, adding about 40% calcium carbonate to polypropylene improves heat resistance by about 200C. When the filling ratio is ≤20%, the heat resistance temperature is increased by 8 to 130C.
(5), improve the astigmatism of plastics
Among plastic products, some products require whitening and opacity, and some hope to extinction. The addition of calcium carbonate can play a role in this regard.
Calcium carbonate with whiteness above 90 has obvious whitening effect in plastic products. Combined with titanium **** and lithopone, the matting properties of plastic products have been 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.
Calcium carbonate with better whiteness can also replace expensive white pigments.
(6) The products can have some special properties.
The addition of calcium carbonate in the cable material has a certain insulating effect. The addition of calcium carbonate can improve the electroplating performance and printing performance of certain products.
Fine or ultra-fine calcium carbonate added to polyvinyl chloride (PVC) has a certain flame retardant effect.
(7), reduce the cost of plastic products
The prices of ordinary light calcium carbonate and heavy calcium carbonate are much lower than the price of plastics. The addition of calcium carbonate will reduce the cost of plastic products. In foreign countries, calcium carbonate is called Filler or Extender.
At this stage, adding calcium carbonate to reduce the cost of plastics is the main goal. With the improvement of the surface properties of calcium carbonate and the controllable shape and particle size, calcium carbonate will gradually become a functional filler for the purpose of reinforcing or imparting functionality.
Calcium carbonate is a commonly used filler in the production and processing of PVC products, and its use purpose is mostly to increase the volume of PVC products in order to achieve the purpose of reducing production costs.
At present, there are two main types of calcium carbonate used in the production and processing of PVC products. The first one is natural limestone that is crushed into calcium carbonate of different fineness by mechanical crushing method, such as by Raymond mill. The quality of calcium is determined by the grade and fineness of natural limestone. Reasonable use of heavy carbonic acid? The heat resistance, rigidity, dimensional stability and processability of VC products made by bottle merchants. The second is to select high-grade limestone which is calcined to decompose it into calcium oxide, react with water to form calcium hydroxide, and then pass into carbon dioxide to form 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. In addition to the quality of natural calcium carbonate, the quality of light calcium carbonate is determined by its calcination and other chemical reaction conditions and classification fineness. 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 a large amount of calcium carbonate will reduce the quality of the product, but if poor quality 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 performance of PVC products very different. Usually, some manufacturers or distributors will mix light calcium carbonate with heavy calcium carbonate and sell it at the price of light calcium carbonate. This phenomenon can occur in light calcium carbonate of various fineness. In addition, some small factories have no strict requirements on the source of raw materials and production processes, resulting in poor quality. Generally, the price of poor quality calcium carbonate is low, and some manufacturers will purchase such calcium carbonate in order to obtain lower production costs, but this is often counterproductive, because its added amount is relatively lower than high-quality calcium carbonate, otherwise Will greatly reduce the quality of products.