Yuan Lei's Little Knowledge |What kind of calcium carbonate does the plastic industry need?

Release time:

2024-05-15 14:41

Yuan Lei's Little Knowledge |What kind of calcium carbonate does the plastic industry need?

Compared with other non-metallic mineral powder materials, calcium carbonate has significant advantages:
(1) Cheap prices;
(2) Good color and easy coloring;
(3) The hardness is low, with a Mohs hardness of 3, so the filling plastic has less wear on the equipment components and molds it comes into contact with;
(4) Good thermal and chemical stability;
(5) Easy to dry, without crystalline water, adsorbed moisture can be easily removed by heating;
(6) Non toxic, non irritating, and tasteless.

What is the effect of adding calcium carbonate on the properties of filling plastics?

(1) The impact on density
     There is no significant difference in true density between heavy calcium and light calcium, with the main difference being apparent density. The same amount of filler, heavy calcium or light calcium, and even different thicknesses of heavy calcium can cause differences in the length, area, or number of plastic products.
(2) Impact on mechanical properties
     The addition of calcium carbonate can lead to a decrease in the mechanical properties of plastic materials, but if surface treatment or interface modification techniques are used beforehand, the adverse effects of calcium carbonate on the mechanical properties of filling plastics can be reduced, and some properties can even be better than pure matrix plastics.
(3) The impact on combustion performance
     In fact, the presence of calcium carbonate does indeed reduce the amount of combustible matrix plastics, and even when the amount of calcium carbonate filling is large, the filling plastics become "low calorific value" materials. However, the more unfavorable aspect is that the presence of a large number of calcium carbonate particles is equivalent to dividing polyethylene and other matrix plastics, which is more conducive to the full combustion of the matrix plastics.
(4) Impact on thermal performance
     Due to the fact that the thermal conductivity of calcium carbonate is more than ten times larger than that of the matrix plastic, and the volume specific heat capacity of the two is not significantly different, the thermal conductivity of filled plastics is improved compared to pure matrix plastics due to the presence of calcium carbonate, which is beneficial for shortening the molding process cycle and improving work efficiency.

What are the requirements for calcium carbonate used for filling plastics?

  (1) The purity of calcium carbonate should be high, the compounds of elements such as silicon and iron should be as low as possible, and the content of harmful heavy metal elements should be strictly required.
   (2) The whiteness should be as high as possible.
  (3) The lower the oil absorption value, the better. By surface treatment of calcium carbonate and coating the surface of calcium carbonate particles, its oil absorption value can be reduced.
  (4) The fineness should be appropriate, not the finer the better, and the particle size distribution should be determined as needed. For the filled plastic, the smaller the particle size of the filler used, the better the mechanical properties of the filled plastic material under the same filling ratio, provided that the powder particles are uniformly dispersed in the plastic matrix.

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