Preparation and properties of polyimide/silver foams using a direct ion exchange method

Abstract

A novel polyimide/silver (PI/Ag) foam was prepared by isocyanate foaming and direct ion exchange between Ag⁺ ions from silver nitrate and the H⁺ ions in the carboxyl (–COOH) groups of the polyamide molecular chain. The microstructures, chemical and phase composition of the PI/Ag foams were tested by SEM, FT-IR and XRD. The properties were tested by TG, DSC and UV spectrophotometer. The effects of different Ag contents on the microstructures and properties were analysized. SEM results showed that the PI/Ag foams had present the opened-cells type. With the increase in the Ag⁺ ions contents, both the amount of silver particles and the UV reflectivity of the PI/Ag foams increased, as the size of silver particles decreased. FT-IR test results show that the introduction of the silver nano-particles have no significant effect on the chemical structure of the PI foams. XRD results indicate that the silver nano-particles are face-centered cubic structure and have good crystalline properties. Thermal tests results show that the PI/Ag foams maintain the excellent thermal stability. Based on the above experimental results, the reaction mechanism during the foaming and curing process were also analysized.