Factors affecting the material properties of filled plastics
The particles are in the form in which the filler is present. The shape of the particles is not very regular, but there are significant differences in the geometry of different kinds of fillers. For flake fillers, the concept of diameter-thickness ratio is often used, that is, the ratio of the average diameter to the thickness of flake particles; for fibrous fillers
The geometry, particle size distribution, physical and chemical properties of the filler particles will directly affect the material properties of the filled plastic.
① Geometric characteristics of filler
The particles are in the form in which the filler is present. The shape of the particles is not very regular, but there are significant differences in the geometry of different kinds of fillers. For flake fillers, the concept of diameter-thickness ratio is often used, that is, the ratio of the average diameter to the thickness of flake particles; for fibrous fillers, the concept of aspect ratio is often used, that is, the ratio of the length to the average diameter of fibrous particles.
② Particle size
The requirements for the thickness and size of the filler particles used in plastic modification are based on the situation. Generally speaking, the smaller the particle size of the filler, if it can be dispersed evenly, the better the mechanical properties of the filler material, but at the same time, the smaller the particle size, the more difficult it is to achieve uniform dispersion, and more additives and better processing equipment are needed, and the finer the particles, the higher the processing cost, so the filler with the appropriate particle size should be selected according to the use needs.
Usually, the particle size of the filler can be expressed by its actual size (m), or by the number of meshes that can pass through the sieve.
③ Physical properties
Density The density of the filler should be consistent with the mineral from which it is derived, and it is its true density that affects the density of the filler material when the filler particles are uniformly dispersed in the matrix resin. Because there are gaps between the particles of the filler when they are stacked, the particle size and distribution of different shapes are different. When the quality is the same, the volume of the pile is different, and sometimes the difference is very large.
Oil absorption value in many occasions filler and plasticizer, if the plasticizer is adsorbed by the filler, it will greatly reduce the plasticizing effect of the resin, and the filler itself in the same amount of filling due to their different oil absorption value, the impact on the system is very obvious.
Hardness The hardness of filler particles is of great importance to the wear of plastic processing equipment, and people do not want the benefits of using fillers to be offset by the wear of processing equipment. In addition, the high hardness of the filler can improve the wear resistance of the filled plastic products and is valued by people. Mohs hardness is the relative comparison of nicking ability between materials: the Mohs hardness of fingernail nicks is 2, which can be carved on talc, but there is nothing to be done on calcite.