Selection and use of coupling agents - applicable filler types

The main effect of coupling agents is achieved through surface modification of fillers, so when choosing coupling agents, we first select corresponding coupling agents for different fillers. The functional groups at both ends of the coupling agent interact with the dispersed phase of the filler and the matrix polymer, respectively. Due to different fillers, the coupling effect varies greatly.

The most widely used coupling agents currently are silane coupling agents, titanate coupling agents, aluminate coupling agents, and other types of coupling agents.

1. Suitable fillers for silane coupling agents

Silane coupling agents have significant effects on silicon dioxide, aluminum trioxide, glass fiber, clay, silicate, silicon carbide, etc., but slightly worse effects on talc powder, clay, aluminum hydroxide, wollastonite, iron powder, aluminum oxide, etc. They have little effect on asbestos, titanium dioxide, iron oxide, etc., and have little effect on calcium carbonate, graphite, carbon black, barium sulfate, calcium sulfate, etc. The coupling effect of silane coupling agent is greater for fillers with silanol groups on the surface, while for carbonates, sulfates, sulfites, etc. of calcium, magnesium, and barium, the coupling effect of silane coupling agent is not very obvious. If the surface of filler particles without silanol groups is treated with silica sol and then silane coupling agent is used, a good coupling effect will be achieved. This treatment method is called double coating method.

2. Suitable fillers for titanium ester coupling agents

Both titanium ester coupling agents and aluminum ester coupling agents can treat the surface of fillers, but the treatment effects are somewhat targeted. Fillers with good treatment effects of titanium ester coupling agents include calcium carbonate, barium sulfate, calcium sulfate, calcium sulfite, aluminum hydroxide, magnesium hydroxide, calcium silicate, aluminum silicate, titanium dioxide, asbestos, aluminum oxide, iron oxide, lead oxide, ferrite, etc; Fillers with slightly inferior processing effects include mica, silica, magnesium oxide, calcium oxide, etc; Fillers with poor processing effects include talc powder, carbon black, and wood powder;