1. General requirements (1) The surface of the reinforc […]
1. General requirements
(1) The surface of the reinforcing filler particles should have strong chemical activity, can form a good combination with rubber, and can improve the vulcanized rubber.
Mechanical properties, aging resistance and adhesion properties. The surface of the non-reinforcing filler particles is chemically inert, and does not chemically bond with the rubber, and does not affect the mechanical properties and weather resistance, acid and alkali resistance and water resistance of the vulcanizate.
(2) It has high chemical purity, uniformity of fineness and good wettability and dispersibility to rubber.
(3) It is non-volatile, odorless, tasteless, non-toxic and has good storage stability.
(4) Fillers for white, light-colored and colored rubber products are also required to be free from contamination and discoloration.
(5) It is cheap and easy to get.
2. Performance requirements
(1) Fineness: Generally speaking, the finer the reinforcing filler particles, the larger the specific surface area, and the larger the contact area with the rubber, the better the reinforcing effect. The finer the non-reinforcing filler particles, the better the mixing effect after adding the rubber. However, it must be evenly dispersed, such as uneven dispersion, even if the particles are very fine, the mixing effect is not good.
(2) Particle shape and crystal form: The shape of the filler particles is preferably spherical, and the sheet-shaped or needle-shaped filler is liable to cause alignment when the vulcanized rubber is stretched, resulting in an increase in permanent deformation and a decrease in tear resistance. The carbon black and white carbon black in the reinforcing filler are amorphous, and other fillers are also crystalline. For example, although the silicon micropowder and the silica are chemically composed of silica, the former is crystalline and the latter is amorphous. The crystalline filler is further divided into an isotropic crystal and an equiaxed crystal. The coaxial crystals x, y, and z are similar in three axes and are isotropic. There are significant differences in the x-axis of the x-axis, y, and z-axis. The anisotropy is commonly used in non-metallic mineral fillers. Clay, graphite, and diatomite are heterogeneous crystal systems. Calcium carbonate is an equiaxed crystal system. For rubber products that require good wear resistance and tear resistance, it is not advisable to use isoaxial crystalline materials as reinforcing fillers.
(3) Surface properties: The powder filler is mixed into the rubber, and the particles are surrounded by the rubber molecules, and the degree of the surface of the particles being wetted by the rubber has a great influence on the reinforcing efficiency. Non-wet particles, which are not easily dispersed in rubber, tend to agglomerate and reduce their reinforcing efficiency. This condition can be improved by adding certain substances that help to increase the wetting. For example, calcium carbonate with little reinforcing effect, after adding fatty acid, reduces surface tension, increases the degree of moisturization, and improves the reinforcing effect.