Room temperature vulcanized silicone rubber has been widely used as adhesives, sealants, potting and molding materials, and has its uses in various industries. Among them, the reinforcing filler has a very important influence on the rheological properties and mechanical properties of RTV silicone rubber. The nano calcium carbonate has the characteristics of low price, excellent performance, large filling amount, non-toxic and tasteless, etc., and can be widely used as a reinforcing filler for RTV silicone rubber.

There are two shortcomings of nano calcium carbonate directly used in silicone rubber: one is that the specific surface area of nano calcium carbonate is large, the intermolecular force, electrostatic interaction, hydrogen bonding, etc. cause the agglomeration of calcium carbonate powder, and the nano calcium carbonate is used as a pro Water-based inorganic compounds have poor affinity with organopolysiloxane, and easily form powder aggregates, resulting in uneven dispersion of nanometer calcium carbonate in the system. Second, the nano-calcium carbonate has a high oil absorption value, has a significant thickening effect on the silicone rubber system, and has poor thixotropy, which affects the construction performance of the silicone rubber. Therefore, the surface modification of nano calcium carbonate must be performed according to the characteristics and requirements of RTV silicone rubber, which can solve the defects of easy flow, poor extrusion, and low strength caused by ordinary nano calcium carbonate.
Modification technology of nano calcium carbonate

The modification of nanometer calcium carbonate mainly adopts wet modification. Specifically, dispersing agent and surfactant are added to the nanometer calcium carbonate slurry. The nanometer calcium carbonate particle size and surface activation rate are controlled by the process. Finally, dehydration, drying, crushing and After classification, modified nano calcium carbonate is obtained.

At present, the most commonly used and most effective surfactants are mainly fatty acid organic compounds. One end of this type of compound molecule is a carboxyl group, an ether group, and other polar groups, which can undergo physical-chemical adsorption or chemical reaction with the surface of calcium carbonate particles to form a stable bridge structure. The other end of the molecule is a long-chain alkyl structure Similar to polymer molecules, so it has good compatibility with organic polymers. After surface modification of nanometer calcium carbonate, the interface binding force between nanometer calcium carbonate particles and organic polymers can be greatly enhanced, and the oil absorption value of nanometer calcium carbonate can be effectively reduced, and the viscosity of the nanometer calcium carbonate / organic polymer system can be reduced. Improve dispersibility and increase the amount of additives.