PREPARATION OF MAGNETIC FLUID HAVING ACTIVE-GAS RESISTANCE AND ULTRA-LOW VAPOR-PRESSURE FOR MAGNETIC FLUID VACUUM SEALS

The magnetic fluid, having an ultra-low vapor pressure property of 7.0 x 10(-10) Pa at 293 K, was prepared. Hexafluoropropylene oxide polyme r oil having high molecular weight was used as base oil. Magnetic part icles were dispersed by using two types of new designed and synthesize d hexafluoropropylene oxide acid derivative surfactants. The obtained magnetic fluid had a saturation magnetization of 35.0 mT, its magnetit e particles were dispersed stably and showed a superior resistance to active gasses. It was ascertained that the magnetic fluid vacuum seal using the prepared fluid had the ultra high vacuum performance. (C) 19 98 Elsevier Science Ltd.