In recent years, with the rapid development of calcium carbonate processing technology and calcium carbonate surface treatment technology, it can not only reduce the cost of products, but also improve many properties of products, and some properties are unique.
What are the functions of calcium carbonate in modification? Positive modification effects of calcium carbonate
What are the effects of calcium carbonate in modification? 01 Environmental protection effects of calcium carbonate
(1) Saving petroleum resources
Based on the calculation of 30% calcium carbonate content in PE, the annual output of plastic packaging bags is 3 million tons , which can save 900,000 tons of petroleum-based resin and reduce the use of 2.7 million tons of oil.
(2) Endow environmental protection performance
Adding calcium carbonate to incinerated plastic garbage bags can increase the burning speed and greatly shorten the incineration time. The specific reason is that the calcium carbonate in the plastic film expands when burned and produces countless tiny pores, which increases the combustible area in contact with oxygen and accelerates the burning speed. For example, the burning time of polyethylene plastic film containing 30% calcium carbonate is reduced from 12 seconds for pure plastic film to 4 seconds.
Plastic films filled with calcium carbonate can promote more complete incineration and reduce the amount of black smoke released due to the wick effect of calcium carbonate. The alkalinity of calcium carbonate in the film can also be used to absorb a large amount of dispersed acid gases, reduce the amount of toxic smoke released, and greatly reduce the chance of acid rain.
What are the functions of calcium carbonate in modification? 02 Common modification effects of calcium carbonate and tetrahydrofuran
(1) Improve the rigidity of composite materials
Calcium carbonate can improve the flexural strength, flexural modulus, and hardness of composite materials , wear resistance and other properties. For plastic films, the improvement in the rigidity of composite materials can significantly increase the stiffness of the film, which is beneficial to the smooth curling of the film.
(2) Improve the dimensional stability of composite materials
The improvement of dimensional stability is reflected in reducing shrinkage, reducing warpage, reducing linear expansion coefficient, reducing creep, and is beneficial to Isotropy, etc., calcium carbonate filling can significantly improve dimensional stability.
(3) Improve the heat resistance of composite materials
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 composites is significantly higher than that of pure PBAT. For another example, especially adding light calcium carbonate to PVC products can absorb the hydrogen chloride produced by decomposition and greatly improve the processing thermal stability of PVC.
(4) Improve the tear resistance of the film
General plastic films have the shortcomings of high longitudinal strength and low transverse strength, especially PBS, PLA, and PHA aliphatic films. Mylar is more obvious. After adding calcium carbonate, the isotropy of the composite material can be increased and the tear resistance can be significantly improved.
What are the functions of calcium carbonate in modification? 03 Special modified properties of calcium carbonate
(1) Effect on tensile and impact properties
Not all calcium carbonates can improve the tensile strength of plastic films. The tensile strength and impact strength are affected by the calcium carbonate particle size and surface treatment.
Influence of particle size: Different particle sizes of calcium carbonate have different modification effects on plastics, as shown in Table 1. Generally, the particle size is below 1000 mesh, which is mainly used for incremental modification; the particle size is between 1000 and 3000 mesh, and the addition amount is below 10%, which has a certain modification effect; the particle size is above 5000 mesh, which is functional calcium carbonate and has Obvious modification effect can improve tensile strength and impact strength. Although nanoscale calcium carbonate has finer particle size, it is currently difficult to disperse and can only achieve the same modification effect as 8000 mesh calcium carbonate.
Table 1 | Effect of heavy calcium carbonate of different particle sizes on the performance of PP composite materials
Image source | Professor Wang Wenguang’s plastic formulation and modification consultation
As can be seen from Table 1, as the calcium carbonate particle size becomes finer, the impact strength, tensile strength, and elongation at break increase, and the flexural strength and The flexural modulus remains essentially the same, but the fluidity decreases.
The impact of surface treatment: Calcium carbonate with appropriate particle size can improve the tensile strength and impact strength of composite materials if the surface is well treated. In recent years, with the continuous development of organic/inorganic composite theory, CaCO3 has changed from a simple filler to a new functional filler material. For example, the notched impact strength of homopolymer PP/CaCO3 composite materials made of calcium carbonate can be more than doubled compared to the base plastic.
(2) Smoke suppression effect during combustion
CaCO3 has excellent smoke suppression effect. The principle is that it can react with (capture) the hydrogen halide in the smoke to generate Stable CaCl2. Therefore, CaCO3 can be used as a smoke suppressant for polymers that produce hydrogen halide when burning, such as vinyl chloride, chlorosulfonated polyethylene, chloroprene rubber, etc. Since the combustion reaction is a solid-gas heterogeneous reaction and can only occur on the surface of solid particles, the particle size of CaCO3 particles becomes an important factor in the smoke suppression effect. Only tiny particles have a much larger specific surface area. The finer the particle size of calcium carbonate, the better the smoke suppression effect.
(3) Anti-adhesive agent
The blown cylindrical film containing calcium carbonate has good opening and will not cause adhesion when curled. Calcium carbonate acts as an opening agent.
(4) Increase the thermal conductivity
The addition of calcium carbonate increases the thermal conductivity of the film, thereby cooling the film bubble of the blown film faster, improving production efficiency and improving��, the performance is basically not degraded. For example, the 50% lightweight calcium carbonate composite material we produce can reach a minimum density of 0.7 when used to produce films, which is a full 45% reduction.
(3) Weight reduction by hollow filling
Using the simple and low-cost inorganic powder hollowing technology, calcium carbonate can be easily made into hollow products, greatly reducing the cost. Its density, the lowest density of calcium carbonate hollow core products can be reduced to about 0.7g/cm3.
What are the functions of calcium carbonate in modification? 02 Reduce the gloss of composite materials
The impact on the surface gloss of composite products is related to the processing method and variety of calcium carbonate. The order of glossiness of specific composite materials is wet process > dry process French process (light calcium carbonate>large calcite calcium carbonate>marble calcium carbonate>small calcite calcium carbonate>dolomite calcium carbonate).
What are the functions of calcium carbonate in modification? 03 Reduce the transparency of composite materials
The refractive index of calcium carbonate is very different from that of commonly used resins such as polyethylene and polypropylene, so regular size calcium carbonate filling will affect the transparency of the film, only Nano-calcium carbonate with a size below 200 nanometers does not affect the transparency of composite products because light waves can bypass it.
What are the functions of calcium carbonate in modification? 04 Reduce the elongation at break of composite materials
The high rigidity of calcium carbonate will reduce the original ductility of composite materials and reduce the movement ability of macromolecular chains, resulting in the elongation at break of products. Growth rate decreases.
What are the functions of calcium carbonate in modification? 05 In most cases, the tensile strength and impact strength of composite materials are reduced
If the particles of calcium carbonate are too large or the surface treatment of calcium carbonate is not good, the tensile strength and impact strength of composite materials will be reduced. The strength decreases, especially the tensile strength decreases most obviously.
What are the functions of calcium carbonate in modification? 06 Increase the stress whitening phenomenon
The resin is filled with a large amount of calcium carbonate. Because the product is stretched, a large number of voids and silver streaks will be produced, which will affect the inherent stress whitening phenomenon of the resin. further strengthened.
What are the functions of calcium carbonate in modification? 07 Accelerate the aging of products
All inorganic powder materials will accelerate the aging of composite materials, and calcium carbonate is no exception.
What are the functions of calcium carbonate in modification? 08 Reduce the connection strength between materials
For films, reduce the heat sealing strength of films, and for pipes, reduce the welding strength of pipes.
Article source: Calcium Carbonate Research Institute
