The traditional concept has always believed that the role of light calcium carbonate is two reductions and one modification: one is to reduce product costs, the other is to reduce product performance; and the other is to increase the density of composite materials. Reducing product costs is a great advantage of calcium carbonate, because the price of light calcium carbonate is very low among all fillers, and the price of plastic products composited with calcium carbonate is definitely very low.
In recent years, with the rapid development of light calcium carbonate processing technology and the rapid development of calcium carbonate surface treatment technology, light calcium carbonate can not only reduce product costs, but also improve many product properties, and some properties are unique. With the increasing maturity of micro-foaming technology and the successful development of hollow calcium carbonate technology, the weight reduction technology of light calcium carbonate composite materials will be put into industrial production.
Therefore, we have reason to predict that in the future, plastic calcium carbonate composite materials can turn the traditional "two reductions and one modification" old hat into a new hat, that is, reduce the cost of composite products, reduce the density of composite products, and improve the performance of composite products. Calcium carbonate has changed from a traditional filler to a new modifier.
Traditional plastic calcium carbonate composite materials do not reduce all the properties of composite materials, but can also improve many modifications of composite materials, but it will also cause many performance degradations. Next, let's take a closer look at the general modification effect of calcium carbonate to guide us to learn from each other's strengths and weaknesses and find the direction of research and development; the direction of calcium carbonate modification.
1. Improve the stiffness of composite materials
Light calcium carbonate can improve flexural strength, flexural modulus, hardness, wear resistance, and other properties of composite materials. For plastic films, improving the stiffness of composite materials can significantly increase the stiffness of films, which is beneficial to the flatness and curling of films.
2. Improve the dimensional stability of composite materials
The improvement in dimensional stability is reflected in the reduction of shrinkage, warping, linear expansion coefficient, creep, and isotropy. Calcium carbonate filling can significantly improve dimensional stability.
3. Improve the heat resistance of composite materials
Light calcium carbonate can improve the thermal stability of composite materials because calcium carbonate can absorb substances that promote decomposition. For example, the thermal stability of PBAT/calcium carbonate composite materials is significantly higher than that of pure PBAT. For example, especially in PVC products, adding light calcium carbonate can absorb Hydrogen chloride produced by decomposition, greatly improving the processing thermal stability of PVC.
4. Improve the tear resistance of the film
General plastic films have the disadvantages of high longitudinal strength and low transverse strength, especially PBS, PLA, and PHA aliphatic polyester films. After adding calcium carbonate, the isotropy of the composite material is improved and the tear resistance is significantly improved.
The following are the methods to effectively improve the whiteness of calcium carbonate:
(1) Strengthen management and improve equipment level. Heavy calcium carbonate production equipment is sold at every penny. At the same time, timely repair and maintenance of equipment is also very important.
(2) The selection of raw ore should be cautious. It can analyze whether the iron in the ore exceeds the standard. In general, Fe2O3≤ 0.1% needs to be added. When it exceeds 0.2%, the product will turn yellow or even red, resulting in a decrease in whiteness. At this time, it needs to be treated with chemical reagents. If the iron pollution is caused by the equipment, it can also be treated in the same way. If the iron does not exceed the standard, this method cannot be used, otherwise the whiteness will be reduced.