Jinuk Kwon

Heat dissipation properties of polyimide nanocomposite films

In development of modern electric fields, the growth of kinds of electronic devices has made the supply and research on heat dissipating films become important. To synthesize heat dissipation films with high thermal resistance for possible use in electronics applications, carbon black is doped into polyimide to increase the dissipating rate of films, at loadings of 50, 100, and 150 wt%. The resulting films display excellent thermal properties; the thermal conductivity of the film with 150 wt% carbon black is 5.59W∙m−1K−1, a value that is 35 times higher than that of pure polyimide (0.16W∙m−1K−1). To theoretically confirm the increased dissipating ability of composite films, the Nielsen equation is used for verification. The experimental results show an excellent fit with the theoretical values calculated by the Nielsen equation. The great thermal stability of polyimide composite film with carbon black is verified by using TGA and DSC, the temperature for 1% thermal decomposition of the 150wt% film is 541°C, and the glass transition temperature is 315 °C. The heat conduction results also show high heat dissipation data, which make the carbon black composite polyimide films an excellent candidate for use in electric devices to deplete the heat generated.

Water sorption behavior in polyimide thin films controlled by inorganic additives

AbstractWe investigated the decreased water diffusivity depending on the content and size of carbon black (CB) added to polyimide (PI) in order to synthesize composite films (PI-CB). CBs with different diameters were used: N110 (CB1, 11–19 nm), N326 (CB2, 26–30 nm) and N660 (CB3, 49–60 nm). The water diffusion coefficient of PI-CB decreased with increasing CB content from 2.67·10−9 for pure PI films to 0.22·10−9 cm2/s for PI-CB films containing 40 wt% CB1. Moreover, the decrease in water diffusivity with increasing CB content exhibited a linear relationship. The water diffusivity of PI-CB increased with the increasing size of CB at the same CB content. The water uptake of PI-CB had a linear relationship depending on the CB content, similar to water diffusivity; the water uptake of composite films decreased by 73% (from 3.67% to 0.98%) for PI-CB1 (40 wt%) films as compared to PI films. In addition, the water uptake varied not only with the CB content, but also by the size of the CB surface area.