Calcium carbonate white powder looks very ordinary, but it accounts for more than 70%of the usage amount of inorganic powder each year. It is a large amount of pink filler in the plastic industry -calcium carbonate, at a low price, excellent ones, excellent ones Many advantages such as processing performance have become materials for the plastic processing industry. In addition to plastic fields, calcium carbonate is also used in more and more in silicone gum.
A small amount of nano -active calcium -active calcium carbonate is usually added when preparing silicone glue to strengthen and reduce costs. In addition, the colloid also maintains a good appearance. But the following issues need to be paid to the following issues during the application process:
Moisture Content Causes Powder Eeunion
If calcium carbonate is high, the number of hydroxyl (-oH) on the surface of the particles increases, and its cluster presents a tendency to condense each other. Three-dimensional networks are formed under the action of hydraulic polyxane to increase the viscosity of the rubber and increase A 1 to 3mm particles are formed in the middle, causing the hybrid time to prolong. Therefore, the calcium carbonate powder must be dried before use, and the control moisture content is below 0.8%.
Second -time Reunion Causes a Large Particle Size
Second-time reunion is generally prone to nano-carbonate products with small particle size. As the particle size of nano-carbonate is reduced to 40-60nm, the particle area is increased (22-34m2/g). It is easy to form a close -combined hard group, that is, a porous secondary particle. During the process of silicone glue, it is difficult to disperse and evenly, and when the number of particles is large, the surface of the product is prone to particles, or even the phenomenon of “hemp surface” or “fog surface”. Therefore, it is necessary to scattered through or multiple times, or extend the pinning time.
Excessive pH value Vatalytic Solidification
Excessive pH value will reduce the storage stability of silicone gum. The higher the pH, the faster the silicone gum curing. Storage storage storage is a very important quality indicator of silicone gum products. Theoretically, the pH value of calcium carbonate is weakly alkaline. It can use weak organic acid or organic acid to cover it on the surface. Certain neutral effects control its pH value below 9.5.
Insufficient or Excess Surface Treatment
When the surface treatment is insufficient, the surface of calcium carbonate particles is a polarity part, which is difficult to compatible with non -polar organic objects in silicone glue, causing dispersal difficulty. Due to the lack of calcium carbonate surface lack of enough organic surface active agent covering, the probability of contact with polar calcium carbonate interface is significantly increased, and there are more hydroxyl groups on the surface of calcium carbonate. The Si-O key in the chain forms a hydrogen bond (physical adsorption), which will produce two different functions: on the one hand, it will improve the physical and physical performance of vulcanized gum, and on the other hand, it will also generate structured phenomena inside the system. The storage stability of the rubber decreases.
