Why choose calcium carbonate for masterbatch? 7 major advantages, it's hard to refuse!
Calcium carbonate is widely used as a filler in resins such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and acrylonitrile butadiene styrene copolymer (ABS). The addition of calcium carbonate can play a role in improving certain properties of plastic products to expand their application range. In plastic processing, it can reduce resin shrinkage, improve rheological behavior, control viscosity, and also serve the following functions:
1. Improve the dimensional stability of plastic products
The addition of calcium carbonate serves as a skeleton in plastic products, playing a significant role in maintaining the dimensional stability of these products.
2. Improve the hardness and rigidity of plastic products
In plastics, especially in soft polyvinyl chloride (PVC), the hardness increases gradually with the increasing amount of calcium carbonate added, while the elongation decreases as the hardness increases. Calcium carbonate with fine particles and high oil absorption has a large increase in hardness. Conversely, calcium carbonate with coarse particles and low oil absorption has a small increase in plastic hardness. Among soft PVC, the increase in hardness is the smallest for heavy calcium carbonate, followed by precipitated calcium carbonate (light).
Calcium carbonate generally does not serve as a reinforcing agent in plastics (resins). The particles of calcium carbonate can often be wetted by the resin, so the normal effect of adding calcium carbonate is to increase the rigidity of the resin, as well as its elastic modulus and hardness. However, as the addition amount increases, both the tensile strength and the ultimate elongation decrease.
Different calcium carbonates, with varying amounts added, will result in different hardness.
3. Improve plastic processing performance
The addition of calcium carbonate can alter the rheological properties of plastics. When adding calcium carbonate powder, the quantity is often substantial, which facilitates its mixing with other components and aids in the processing and shaping of plastics.
The addition of calcium carbonate, especially after surface treatment, can not only enhance the hardness of the product, but also improve its surface gloss and flatness.
The addition of calcium carbonate can reduce the shrinkage rate, linear expansion coefficient, and creep properties of plastic products, thereby facilitating processing and forming.
4. Improve the heat resistance of plastic products
Adding calcium carbonate to general plastic products can improve their heat resistance. For example, adding about 40% calcium carbonate to polypropylene can increase its heat resistance by about 20°C. When the filling ratio is ≤20%, the heat resistance temperature can be increased by 8 to 13°C.
5. Improve the light diffusion of plastics
In plastic products, some require whitening without transparency, while others desire a matte finish. The addition of calcium carbonate can play a certain role in this regard.
Calcium carbonate with a whiteness of over 90 has a significant whitening effect in plastic products. When combined with titanium dioxide and lithopone, the matting effect of plastic products is greatly improved.
In calcium-plastic paper, the addition of calcium carbonate to both low-density polyethylene (LDPE) and high-density polyethylene (HDPE) films can achieve the effects of light diffusion and extinction, making it suitable for writing and printing.
Calcium carbonate with good whiteness can also replace expensive white pigments.
6. It can impart certain special properties to the product
The addition of calcium carbonate to cable materials serves a certain insulating function, and the inclusion of calcium carbonate can enhance the electroplating and printing performance of certain products.
The addition of micro-fine or ultra-fine calcium carbonate 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 both far lower than that of plastic. The addition of calcium carbonate can reduce the cost of plastic products. Therefore, calcium carbonate is called filler or extender abroad.
At the current stage, the primary objective of adding calcium carbonate is to reduce the cost of plastics. With the improvement of the surface properties and controllability of shape and particle size of calcium carbonate, it will gradually become a functional filler aimed at reinforcement or imparting functionality.
Calcium carbonate is the most commonly used filler in the production and processing of PVC products. Its primary purpose is to increase the volume of PVC products, thereby reducing production costs.
The rational use of heavy calcium carbonate can enhance the heat resistance, rigidity, dimensional stability, and processability of PVC products. The second approach involves selecting high-grade limestone, calcining it to decompose it into calcium oxide, reacting it with water to form calcium hydroxide, and then introducing carbon dioxide to precipitate calcium carbonate. This type of calcium carbonate is referred to as light calcium carbonate. The use of a small amount of light calcium carbonate can improve the tensile strength of PVC products. The quality of light calcium carbonate is determined not only by the grade of natural calcium carbonate, but also by chemical reaction conditions such as calcination and classification fineness. The price of light calcium carbonate should be more than double that of heavy calcium carbonate of the same fineness.
