Abstract: The present invention provides a process for producing molded articles of a polyimide precursor by a use of a usual extrusion technique, and physical properties of polyimide products prepared by the heat treatment of the molded articles of the polyimide precursor at 400.degree. C. are excellent. This process is characterized by drying a solid obtained by pouring a dilute solution of a polyimide precursor including an aromatic tetracarboxylic acid component and an aromatic diamine component 1 into a liquid in which the precursor is only poorly soluble to obtain a dry solid having a polyimide precursor concentration of 50-70% by weight, and then extruding this dry solid at 80.degree.-130.degree. C.

Abstract: A vibration damper of a high polymer resin sheet which contains epizoelectric ceramic powder and a cloth layer placed therein including carbon fibers, which provides excellent as well as consistent and reliable damping effects in a relatively wide temperature range and also a method for producing the vibration damper.

Abstract: Synthetic pulp having a peculiar structure is prepared by making a composition consisting of 50 to 90 parts by weight of polypropylene having a melt flow rate of 30 to 150 and 50 to 10 parts by weight of low density polyethylene having a melt index of 0.5 to 10 into a film having a thickness of 70 .mu. or less, uniaxially stretching the film, cutting the stretched film to a predetermined length of 5 mm or less, and fibrillating the cut film by a crumpling and disintergrating action mainly by blows and air whirling stream. A suitable apparatus for such fibrillation is presented. Synthetic pulp thus prepared provides a paper-like material having superior properties by blending it with e.g. wood pulp.