Mina Ishida

Effects of precursor structure and imidization process on thermal expansion coefficient of polymide (BPDA/PDA)

Effects of the drying condition on thermo-mechanical properties and morphology of PI(BPDA/PDA) were investigated. Polyamic acid and polyamic acid esters were used as precursors of the polyimide. Thermal expansion coefficients (TECs) of the polyimide films are strongly affected by precursor structures. The esters give larger TECs than the polyamide acid does. TEC of polyimide film from polyamide acid depends on imidization conditions. The lowest TEC is obtained when the film is dried at 100°C and the value increases with the drying temperature. The TECs of the polyimide films formed from polyamide acid esters do not depend on the drying temperature. In summary, interactions between the precursors and solvent (NMP) lead to large differences in higher order structures of the polyimides, which in turn affects the TECs.

Ultrafiltered Perfluoropolyether lubricant under molecular weight distribution control

There are many problems to be overcome when storage devices are used at high-speed rotation and very small spacing between the head and disk. One of them is lubricant spin-off. Lubricant spin-off and lubricity have a close relation to the molecular weight distribution. The commercial Perfluoropolyether (PFPE), which is widely used as a lubricant for magnetic disks, has a wide molecular weight distribution from several hundred to over ten thousand. In order to improve performance regarding spin-off and lubricity, it is necessary to control the molecular weight distribution. This paper discusses the relation between molecular weight of lubricants and spin-off, and stiction. The molecular weight at which spin off occurs easily is found to cause a high stiction. Furthermore, molecular weight distribution control by ultrafiltering is investigated. Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000