What are the effects of adding coupling agents to coatings

In the coating system, the application of coupling agents significantly affects the dispersibility and wetting of fillers. Copper based composite conductive coatings have poor conductivity stability due to the easy oxidation of copper powder, and adding coupling agents is one of the effective methods for preventing copper powder oxidation.

The rational application of appropriate coupling agents will directly determine the performance of copper based composite conductive coatings. Coupling agents improve the dispersibility and wetting of fillers in the base material by coupling and binding them to the surface of inorganic fillers through chemical reactions. It is necessary to choose the appropriate coupling agent and its treatment method based on different base material filler systems and the functions to be achieved.

Without the presence of coupling agents, copper powder, as an inorganic substance, is difficult to tightly bond with the resin. When coupling agents are added to the composite system, the dispersion of copper powder particles is good, and the coupling agent can significantly improve the compatibility and chemical reactivity between copper powder and epoxy resin, endowing the copper powder with good interfacial adhesion to the substrate. When the coupling thickness is appropriate, the resistance of the coating is the lowest. Due to the tight bonding of copper powder resin coupling agents, it can be foreseen that the system has good oxidation resistance.

The coating resistance obtained by pre-treatment method is the highest, followed by post-treatment method, and the coating resistance obtained by direct addition method is the lowest. According to the conductive mechanism of composite conductive coatings, only when a moderately thick protective film is formed on the surface of conductive particles, can the coupling agent play a dispersing and protective role while also improving conductivity. When the mass fraction of coupling agent is constant, the pretreatment method has the best coating effect due to avoiding the influence of solvents and epoxy resin, but it affects the conductivity of the coating. The direct addition method has the best effect. In this case, a coupling layer with appropriate thickness can be formed, while also playing a good dispersing role.