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Effect Of Coupling Agent Content On Electrical Properties Of Filled Conductive Polymers
Apr 05, 2018

Because the coupling agent can better connect the inorganic filler and the organic binder resin, it forms an active organic monomolecular layer between the inorganic and organic interfaces, one end is bonded with the surface of the inorganic material, and one end is chemically or physically with the organic material. Tangles, thus forming an organically integrated whole. Therefore, the use of a coupling agent can promote uniform dispersion of the conductive filler and improve the leveling and wetting of the slurry. The content of the coupling agent in the conductive polymer should have an optimum value.

When the coupling agent content is about 4.0%, the volume resistivity of the conductive polymer is the smallest. When the coupling agent content is less than 4%, the coupling agent is not completely coated with the conductive filler, so that the silver powder is unevenly distributed in the resin, resulting in a larger volume resistivity of the coating film; when the content is more than 4%, the silver particles are uniformly dispersed. However, the coupling agent has a thicker coating on the surface of the silver particles, and the distance between the conductive particles is larger than the critical value of the electron emission and tunneling effect, so that the volume resistivity becomes larger; when the coupling agent content is about 4% At this time, not only the silver powder particles are uniformly dispersed, but also the coupling agent coating thickness is appropriate. At this time, the volume resistivity of the coating film is minimum.

[Conductive silver paste] refers to a silver paste printed on a conductive substrate so that it has a conduction current and eliminates the accumulation of static charge, and is generally printed on a non-conductive substrate such as plastic, glass, ceramic or cardboard. The printing method is very wide, such as screen printing, letterpress printing, flexographic printing, gravure printing and lithography. Diffearent printing methods can be selected according to the film thickness requirements. The resistance, solder-resistance, and friction resistance are also different depending on the film thickness. This kind of silver paste has two kinds of thick film paste and resin type. The former is a high-temperature firing molding using a glass frit as a binder, and the latter is a low-temperature dry or radiation (UV, EB) curable screen silver paste using a synthetic resin as a binder. Conductive silver paste consists of conductive fillers, adhesives, solvents, and additives. Conductive fillers use the most conductive silver and copper powders, sometimes gold powder, graphite, carbon black (now known as conductive carbon black), carbon fiber, nickel powder, and the like. Synthetic resins used as binders include epoxy resins, alkyd resins, acrylic resins, polyurethane resins, melamine formaldehyde resins, phenolic resins, and vinyl chloride-vinyl acetate copolymer resins. The volume is a medium-boiling (120-230°C) solvent used for screen silver pastes that dissolve these resins. In addition, additives such as a dispersant, a slip agent, and a coupling agent are added as required. Conductive silver paste required characteristics: electrical conductivity (antistatic), adhesion, printability and solvent resistance.

Thick film pastes are used in ICs (integrated circuits), capacitors, electrodes, etc. Resinized pastes are used in printed circuits, membrane switches, and antistatic packaging.