Fabrication Of Highly Reflective And Conductive Silvered Polyimide Composite Films And Study On Their Forming Mechanism

Flexible silvered polyimide (PI) composite films has been an active area of interest due to their light weight, highly reflectivity and conductivity, excellent thermal stability, wear resistivity, long-term stability and superior mechanical properties. Their uses include electronics, microelectronics, military, aviation and space applications.Reflective and surface conductive flexible silvered polyimide films have been prepared by the in situ self-metallization method. Depending on curing environment, PI structures with flexible chains and groups, and suitable silver concentration, the silvered PI films can be fabricated with high reflectivity, high surface conductivity and outstanding metal-polymer adhesion. By using BTDA-ODA type polyimide, the silvered Films with reflectivity > 90% and surface electrical resistivity less than 0.2Ω/sq were obtained. Mechanical properties of the obtained silvered PI films have retained those of their parent polyimide.A surface modification and in situ self-metallizing procedure have been developed in this study to fabricate silvered PI films with highly reflectivity and conductivity at both sides. The silvered polyimide films have been prepared by potassium hydroxide hydroxylation of polyimide film surface and incorporation of silver ions through subsequent ion exchange. Thermal curing has not only recycloimidized the poly(amic acid) into polyimide, but also reduced silver ions into silver atoms and near-atomic silver clusters, which diffuses and aggregates to give reflective and conductive surfaces without need of the addition of reducing agents. The thickness of silvered layer and the reflectivity and conductivity of the silvered films can be controlled by using suitable kinds of PIs, modification time and temperatures, concentration of aqueous silver nitrate solution and ion exchanging time. By this method, the double-side silvered polyimide films with double side excellent reflective (reflectivity > 97%), conductive surfaces (surface resistivity:0.02 Ω /sq) and outstanding electromagnetic shielding properties (100 dB between10-10000kMHz) can be easily fabricated. Furthermore, their essential mechanical properties can be maintained. This approach demonstrated many advantages, such as lower cost, double-sided reflective and conductive surfaces, excellent mechanical properties, controllable thickness of...