| With the rapid development of the electronic industry, electromagnetic interference (EMI) is becoming an increasing problem. The electromagnetic interference shielding is increasingly required. Among all the shielding methods, the conductive coating is one of the most important materials to shield EMI occupying the 75% of the shielding market. Studies on the development of the the EMI shielding coating is particularly important. In this thesis, we prepared Ni/acrylic resin, Ni/Carbon/acrylic resin, Ni/acrylic resin/ chlorinate polypropylene electromagnetic shielding coating by the optimized composing techniques based on studies on the factors depending the electromagnetic interference shielding effect of the resultant coating. Mechanism of the well-dispersed preparation process and the behavior of the additives in the property-improving effect is studied systematically. Properties of electromagnetic shielding coating made of Ni/acrylic resin, Ni/Carbon/acrylic resin, Ni/acrylic resin/ chlorinate polypropylene and their relationship with the structure is also investigated.Among those conductive fillers, nickel particle is one of the best option for shielding EMI because of its good stability. And the polymer matrix acrylic resin has good physical properties in comparison with other commodity resin. Consequently, Ni/Acrylic resin was selected as the shielding materials in our research. The conductive framework was build with the resin and the filler when the content of the filler is 60wt%. It was also found that adopting the mixture solvent system (for example, ethanol: butyl alcohol =16:4 by volume) will avoid the coating defects in comparison with other solvent systems. Coupling agent (WD-70) and organophilic bentonite (801-D) were used as additives in the coating to improve the dispersion and conductivity of the resultant coating.When the additive amount of coupling agent (WD-70) is lwt% compared to the content of the filler and coupling reaction time is 3h, the electric resistivity of the resultant coating is the lowest. Effects of highly exfoliated organophilic bentonite on the storage properties of the resultant coating were studied. By varying the content of the polar additives, the organophilic bentonite pretreatment technology is optimized. The 50wt% polar additives compared to the amount of the organophilic bentonite is approciate for the organophilic bentonite activitation and the amount of organophilic bentonite is 5wt% compared to the content of the filler, the electric resistivity of the resultant coating is the lowest. The effect of inclusion of carbon black as additional pigment is studied. The dispersion of the composites showed significant enhancement and the conductivity of the composites changed little when the nickel and carbon black mix ratio is 4:1.The resultant coating showed extra-fine adhesion on pp (grade 2 after the grid test) when theacrylic resin and chlorinate polypropylene mix ratio is 8:1. It can be used in many kinds of engineering applications (SE>30dB that is 99.19%of the electromagnetic wave was shielding). |
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