Yuan Lei's Little Knowledge | Application and Index Requirements of Nano Calcium Carbonate in Plastics
Nano calcium carbonate refers to the functional inorganic filler with a particle size of 1-100nm, which is widely used in rubber, plastic, paper, ink, coating, sealant and adhesive, medicine, toothpaste, food and other fields. However, different applications have different requirements for the particle size, crystal form, oil absorption value and dispersion of nano-calcium carbonate.
The plastic industry is currently the most used industry in the world. It can act as a regulator and enhancer for plastics, and the demand is very large. Due to the good dispersion of nano calcium carbonate, it can well remove the voids and bubbles in the plastic, so that the plastic can shrink more evenly, and improve the mechanical properties and thermal stability of the plastic.
The technical requirements of the plastic industry for nano calcium carbonate are:
Oil absorption value:The oil absorption value of nano calcium carbonate in the plastics industry is generally very low, because the particle size of nano calcium carbonate is small and the specific surface area is large. If the oil absorption value is large, the plasticizer consumed during mixing will be more, which will increase the viscosity of the system, which will not only affect the processing performance, but also increase the production cost.
Crystal Form:The morphology of nano calcium carbonate is divided into: cubic, nearly spherical, spindle, rod, chain, needle and so on. Cubes with lower oil absorption value, or the cube part is chain-shaped and spherical is appropriate.
Particle size:The particle size of nano calcium carbonate used in plastics is generally controlled at about 80-120nm. Too large particle size cannot reflect the effect of nano calcium carbonate and affect the smooth surface of the product. Too small particle size will lead to an increase in surface energy, serious particle agglomeration, and difficult to completely disperse during processing, resulting in particles on the surface of the product.
Dispersion:High dispersion of nano calcium carbonate should be selected. If nano calcium carbonate is seriously agglomerated, the secondary particle size will be much larger than the primary particle size, while the shear force of plastic processing and mixing is not too strong, and some nano calcium carbonate with serious agglomeration is not easy to break up, which will cause local defects in application, resulting in product quality problems.
Moisture:Moisture control should not be higher than 0.5%, if the moisture is too high, will make the plastic surface bubbles or empty drum and other phenomena.
pH:The pH value of nano calcium carbonate should be controlled below 10. If the pH value is too high, it will affect the whiteness and surface gloss of the products and make the appearance worse. At the same time, the high pH will increase the viscosity of the system and affect the processing process.
Hydrochloric acid insoluble matter:It mainly refers to the impurity particles such as black spots and yellow spots in the product, which need to be strictly controlled. Otherwise, when there are more particles, it is easy to cause frequent blockage of the extruder filter screen during processing, affecting the production efficiency, and sometimes forming obvious black spots on the surface of the product, affecting the appearance quality of the product. Iron-containing fine particles may increase the yellowness and decrease the whiteness of the product. Special attention should be paid to nano calcium carbonate used for light-colored products.
Among all kinds of non-metallic mineral powder materials used in the plastics industry, the amount of calcium carbonate is the largest, accounting for about 60 ~ 70% of the total amount of plastic additives, but there are still many problems in the research of high-performance application, especially how to solve the agglomeration of nano-calcium carbonate, how to improve the dispersion effect of nano-calcium carbonate, how to improve the bonding strength of composite materials and so on.
Requirements, calcium carbonate, nano, plastic, particle size, products, surface, industry, impact, particles
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