How does silica improve the fluidity of the main base material ?
Generally, silica particles must be able to adhere to the surface of the main matrix particles, thus affecting the physical properties of the main matrix particles. The degree of adhesion can be from covering the whole surface of particles to covering part of the surface of particles little by little. However, there is an affinity between silica particles and main matrix particles, which will form an ordered mixture. Today, I'd like to take you to understand the mechanism of the anti caking effect of silica. I hope it can help you.
(1) Provide physical barrier. When the surface of the main base material particles is completely covered by silica particles, due to the small force between silica particles, the formed silica layer naturally becomes a physical barrier to block the interaction between the main matrix particles. This kind of physical barrier will lead to several results. One is that silica blocks the hydrophilic substances on the surface of the main base material, which forms the liquid bridge between particles due to moisture absorption or free water remaining during preparation; the other is that after silica is adsorbed on the surface of the main base material, it makes it smoother, thus reducing the friction between particles and increasing the fluidity of particles. This effect is often referred to as Lubrication. Due to the different properties of silica, they provide different lubrication.
(2) The moisture absorption and caking tendency of the main base material can be improved by competing with the main base material particles for moisture absorption. Generally speaking, silica itself has great hygroscopicity, which can reduce the caking tendency of the main binder due to its hygroscopicity.
(3) The main surface charge of the material is eliminated by the static force on the surface of the material. Microcapsule powder particles generally have the same charge, so they will repel each other to prevent agglomeration. However, the electrostatic charge on these products often interacts with the friction and static electricity of production equipment or packaging materials, which brings a lot of trouble. When silica is added, silica will neutralize the charge on the surface of the main matrix particles, thus improving the fluidity of the main matrix powder. This effect is often used to explain why the fluidity of silica can be improved when the affinity between silica and main matrix particles is not very large and silica is only scattered on the surface of the main matrix particles.
(4) By changing the crystal lattice of the main base material, a brittle crystal structure is formed. When silica exists in the aqueous solution of crystalline substances in the main matrix or on the surface of crystallized particles, it can not only inhibit the crystal growth, but also change its crystal structure, thus producing a very fragile crystal under external force. It can reduce the agglomeration of the main base material which is easy to form hard agglomerates, and improve its fluidity