Calcium Carbonate Performance Parameters Have Such A Big Impact on The Filler Masterbatch!

Calcium Carbonate Performance Parameters Have Such A Big Impact on The Filler Masterbatch!

In the field of plastics processing and modification, calcium carbonate, as a common inorganic filler material, has a decisive impact on the quality and performance of filled masterbatch in terms of its performance parameters. From calcium content, whiteness and color, to moisture and volatile matter content, particle size distribution, particle shape, and other components content, every detail may become a key factor affecting the final performance of plastic products.

1.Calcium content

Calcium content is an important quality and technical index of calcium carbonate. Modified masterbatch requires high calcium content of calcium carbonate, which is generally above 98%. The higher the calcium content, the more stable the processing performance of calcium carbonate. When the calcium content is low, it will increase the content of heavy metals and other non-metals and other impurities, which not only affects the use of calcium carbonate, but also affects the processing technology, affects the quality of the product or causes harm to the processing equipment.

2. Whiteness and color

The whiteness of calcium carbonate directly affects the whiteness and coloring of modified masterbatch, and the whiteness of modified masterbatch is very strict.

At present, the whiteness of calcium carbonate for 400 mesh should be more than 95%, and the whiteness of calcium carbonate processed by some ores can reach about 97%. Some modified masterbatch manufacturers in order to make the product whiteness increase, often add fluorescent whitening agent, to achieve the effect of increasing whiteness.

However, because the chemical components of fluorescent whitening agent is easy to decompose and react under high temperature and high shear, if the species of fluorescent whitening agent is not properly selected or added in excess, it will not only make the product decompose and yellow, but also appear non-dispersible or cohesive agglomeration phenomenon.

Fluorescent whitening agent for health and safety, contact with the human body of plastic products, will produce a certain degree of irritation, should not be used.

Hue is also a very important technical indicator of calcium carbonate, and the determinants of temperature and hue are the structure and origin of the ore. These factors will directly affect the colorability of plastic products, affecting the color and gloss of plastic products. Therefore, the whiteness and hue of calcium carbonate is an important technical index that cannot be ignored.

3. Moisture and volatile matter content

The raw materials of calcium carbonate - natural marble, calcite, etc., generally do not contain structural water. After processing into ultrafine powder, it is easy to be damp and absorb moisture during processing, storage and transportation. Calcium carbonate sometimes contains traces of volatile substances, which can affect the modified masterbatch and plastic products if the content is too high.

Moisture and volatile content in calcium carbonate should be controlled at about 0.3%, the actual application, the product moisture content ≥ 0.3%, it is easy to affect product quality, so that the product surface roughness, bubbles, burning, decomposition and other phenomena. So it is very important to control the moisture content on the quality of the modified masterbatch, and the commonly used method is to use high-speed mixer heating and drying process to eliminate moisture.

In the production of calcium carbonate high content filler modified masterbatch, conditions try to avoid the use of water tanks infiltration pull strip cutting and water ring granulation process, the use of crawler drive mesh dry granulation process and grinding surface hot cutting granulation process, can be under the premise of improving the production output, to minimize the modified masterbatch moisture and volatile content, to ensure the quality of the modified masterbatch products.

4. Particle size distribution

Particle size distribution of calcium carbonate is an important quality control index of modified masterbatch. Inorganic mineral powder particle size analysis is commonly used in a relatively simple sieving method, sieving method commonly used in the specifications with "mesh". The so-called mesh is the number of holes per inch of the sieve. However, the more accurate and scientific method of particle size analysis is to use the actual size of the measured particles, expressed in microns (μm).

Sieving method is one of the most traditional particle size analysis method, that is, the dispersibility of good ultra-fine powder with a certain number of mesh sieve sieve, sieve through the sieve and sieve the weight of the powder ratio that is the sieve rate. Commonly used standard sieve finest 500 mesh (equivalent to 25μm or so), the new electrodeposition screen can be screened as small as 5μm (2500 mesh) of the powder, but the screening time is long, easy to clogging. For ultrafine powders smaller than 10μm (1250 mesh), using the sieving method, it is difficult to use for particle size analysis and detection.

In practice, the particle size distribution range of calcium carbonate and other granular materials have large fluctuations, the narrower the particle size distribution range, the more stable the performance of the material, the wider the particle size distribution range, the poorer the performance of the material. For example, 1250 purposes of calcium carbonate, the particle size should be about 10 μm, if the particle size distribution in 5 ~ 38 μm, although the theoretical calculation of the average particle size can be close to 10 μm, but because of the small particle size, specific surface area, easy to cohesion into a group; and the particle size of the large products caused by the surface roughness of the surface and other phenomena, so its processing performance, mechanical properties and so on will be affected.

5. Particle shape

Calcium carbonate particle shape according to the different mineral structure, is divided into polygonal body, flat body, prismatic body, rectangular body, long rod body, other irregular body and other particle shapes.

The particle shape of calcium carbonate has a great influence on the processing technology, product quality, melt fluidity and mechanical properties of modified masterbatch. Polygonal, polygonal, rectangular shape of calcium carbonate in the modified masterbatch processing melt fluidity is good, easy and coupling agent coating crosslinking, processing equipment wear and tear is relatively small, the disadvantage is that modified masterbatch applied to plastic products, easy to affect the mechanical properties of plastic products (such as tensile strength, bending modulus, etc.).

Flat and long rod-shaped calcium carbonate particles have a relatively large surface area, in the modified masterbatch coupling agent, plasticizer and other additives need to be increased appropriately. Otherwise, it is easy to cause uneven coating, poor melt fluidity, host power increases, head resistance increases, but also produce overheating decomposition and other phenomena. However, this kind of shape of the material is beneficial to the physical properties of plastic products, can improve tensile strength, bending strength, reduce the shrinkage of plastic products.

6. Content of other components

Calcium carbonate in the chemical components and metal impurities and other components of the content of calcium carbonate also has a certain impact on the quality of calcium carbonate, in the plastic modification of the masterbatch and plastic products in the application will have a certain impact. Calcium carbonate generally contains a small amount of magnesium oxide (MgO), silicon dioxide (SiO2), iron oxide (Fe2O3), alumina and trace heavy metals (aluminum, arsenic, mercury, etc.). With the origin and different ores, the other components of the content is also different.

Calcium carbonate in the MgO hardness is small, whiteness is slightly lower than calcium carbonate, chemical stability, processing performance is similar to calcium carbonate, calcium carbonate will not generally have a greater impact on calcium carbonate.

SiO2 belongs to the natural quartzite, its specific surface area is small, good mobility. However, SiO2's high hardness (Mohs hardness 7), serious wear and tear on equipment, especially in the uneven coating or plasticizer dosage, especially prominent. Filled modified masterbatch if used in the production and processing of polypropylene flat wire, the high-speed slitting tool is easy to produce collision and often damage the knife edge, affecting the production and processing.

Fe2O3 in calcium carbonate content is very small, but iron and chemical additives are easy to chemical changes when mixing and processing, Fe2O3 is easy to decompose and turn yellow when heated, affecting the whiteness and appearance of the modified masterbatch.

The lower the content of SiO2 and Fe2O3 in calcium carbonate, the smaller the impact on the quality of the modified masterbatch, generally 5% hydrochloric acid can be used to dilute the solution in a glass dish to add calcium carbonate for chemical analysis, and observe the amount of precipitates in the solution to determine the content of SiO2; the color of the solution slightly yellow, indicating that the content of Fe2O3 is more.

Calcium carbonate as a kind of economic and efficient inorganic filler, the application in flame retardant not only helps to reduce the cost, but also improves the flame retardant property of the material. Through reasonable proportioning, calcium carbonate can enhance the thermal stability of plastics and slow down the burning rate, thus maximizing the cost-effectiveness without sacrificing safety. However, the amount of calcium carbonate added is not arbitrary and is limited by technical capabilities. Excessive amounts of calcium carbonate may affect the processing flow of the material and the mechanical properties of the final product. Therefore, precisely controlling the amount of calcium carbonate added requires an in-depth understanding of materials science and process technology to ensure that the overall performance of the material is maintained while the flame retardant effect is enhanced. Exploring this balance is important for the sustainable development of the plastics industry.