Abstract: Fibers coated with thin polymeric films are disclosed and claimed. In a preferred embodiment, microporous fibers are coated with a pre-cast polymeric film having a thickness of about 200 to about 2000 Angstroms.

Abstract: A process for improving the gas separation efficiency of a bundle or module of hollow gas separation fibers by selectively sealing defective fibers without sealing good fibers through which a gas A passes significantly more readily than a gas B. At the beginning of this process the same atmosphere containing A and B is in the interior and at exterior surfaces of said fibers. A curable sealant is applied to a first open end of the fibers, the opposite end of the fibers is blocked, and the partial pressure of A at the exterior fiber surfaces is increased. The resulting pressure build-up inside the non-defective fibers prevents them from being penetrated significantly by the sealant. When the tip of the fibers is cut cleanly away, the good fibers are open but the defective fibers are plugged with sealant.

Abstract: A process for rapidly removing the binder from a greenbody composed of a sinterable powder dispersed within a polyacetal binder is achieved by contacting the molded ceramic greenbody with an acid which depolymerizes the polyacetal binder.