Polyimide track membranes for ultrafiltration and microfiltration

A new process was developed for preparing track membranes of a heat- and radiation-resistant polymer, polyimide. Every step of pore formation was investigated: (1) The action of high-energy (> 0.3 MeV/nucleon) ions on polyimide was studied, and ion bombardment was shown to cause the imide rings to cleave to form imide groups and intermolecular cross-links. (2) Pore etching and pore structures were investigated. A new, readily available and ecologically safe etching agent (concentrated hydrogen peroxide) was suggested. This etching agent showed high selectivity and its rate of track etching in polyimide was as good as that of well-known reagents. Membranes for ultrafiltration (pore diameters of 0.05 μm and smaller) and microfiltration (pores 0.05-2.0 μm in diameter) were prepared