Abstract: A method of manufacturing a randomly patterned floor covering having contrastingly-colored zones from a preform of rubber in which the preform is cut in pieces, each of which are molded into a blank having projections extending from a top side of the blank in relief-like fashion, solidified by vulcanization and then machined by cutting only in the region of the projections. The rubber forming the contrastingly-colored zones is mixed with contrastingly-colored particles in an amount of at least ten percent by weight. These particles are substantially free of flat surfaces and are in, at least, an advanced state of vulcanization. The particles located in the projections extending from the top side of the blank are exposed during the cutting step.

Abstract: A method for forming carbon-carbon composites consists of impregnating structures with carbon-forming precursor compounds comprising multi-functional benzoxazine compounds. The impregnated structures are pyrolyzed to form carbonaceous char which serves to fill the interstices in the structure, thus densifying the composites. The process of impregnation and pyrolysis is repeated as many times as required to obtain the composite density desired. Unusually high char yields are produced by multi-functional benzoxazine compounds in which benzoxazine are joined to each other through a bridge characterized by having conjugated unsaturation associated therewith. A number of preferred compounds providing unexpectedly high yields of char are shown, enabling the desired densification to be achieved with a minimum number of impregnation and pyrolysis cycles, thereby reducing the costs of forming the composites.

Abstract: A family of composite materials consisting of a mineral filler and a synthetic polymer are provided which are characterized by properties similar to natural ivory. The ivory-like composite material contains about 25 to about 75 percent by weight of the mineral filler, preferably a calcium phosphate. In addition, the composite material contains about 75 to about 25 percent by weight of the polyamino acid, preferably an .alpha.-amino acid such as poly(gamma-methyl L-glutamate). The composite material is formed using in situ polymerization techniques, thereby ensuring intimate and homogeneous blending of the mineral and polymer phases as well as facile preparation at ambient temperatures. In addition, the ivory-like composite material is molded using an isostatic compression molding technique. The composite material may be molded to form virtually any desired shape for decorative or practical purposes, or for subsequent carving.

Abstract: A railroad brake shoe friction composition is prepared in the absence of a volatile solvent by first preparing a fluid paste bonding matrix containing an uncured rubber compound, a blend of highly polymerized cashew nut shell liquid resin with a reactive diluent and high surface area inorganic fillers, and thereafter adding other fillers and reinforcing fibers.

Abstract: A process for making polyimide sheet molding compounds which involves the preparation of a polyimide precursor solution of adjusted viscosity that includes a mixture of high and low boiling alcohols, and which also includes monomeric reactants including a diester of an aromatic dianhydride, an aromatic diamine, a monoester of norbornene dianhydride, the reactants being present in a relative molar ratio selected to yield a polyimide having a desired molecular weight. The solution, which further contains particular amounts of staple reinforcing fibers is deposited as a sheet between two carrier film layers and is partially dried to remove the low boiling alcohols.

Abstract: The invention relates to a process for the processing of a thermoplastic polycondensation polymer by supplying the polymer in finely distributed form to a first vented extruder in which the polymer is devolatilized at a temperature below its melting temperature. The polymer is then placed in a second extruder where the polymer is transported below the melting temperature of the polymer over a first length of the screw from the inlet of the extruder, with constant evacuation of volatile components by means of a vacuum exhausting device at a vacuum of less than 10 mbar and the polymer is compressed and melted over a second length of the screw and then leaves the extruder as an end product of a semimanufacture.

Abstract: The present invention provides a method for forming a cured-resin layer having a surface with antistatic properties. An ultraviolet-curable resin having antistatic properties is laminated on an ultraviolet-curable resin for forming an electrostatic cured surface by curing and the two layers then being simultaneously cured by ultraviolet irradiation thereon. A cured-resin layer is thereby obtained where the surface layer of the cured resin is provided with antistatic properties, and is strongly held by chemical bonding.

Abstract: Direct adhesion between a body of a thermoplastic material and a rubber mass by covulcanization is achieved by bringing a rubber body constituted of the components:100 parts by weight of an EP(D)M rubber functionalized with carboxyl groups;100-300 parts by weight filler(s);1-10 parts by weight peroxide-type vulcanizing agent;0-4 parts by weight vulcanization activators; and optionally plasticizers, in contact with a body of a thermoplastic material constituted of 30-100 wt. % of a reaction product of a thermoplastic polyester and a polyisocyanate;1-50 wt. % of a reinforcing material; and0-20 wt. % of additives.

Abstract: A process and device for producing a rubber tube having a smooth outside surface in which a molten synthetic resin is heated from the inner circumferential side immediately before it flows from a die along the periphery of a rubber material layer and the rubber mentioned is cooled within the die.

Abstract: A method for continuously vulcanizing a self-molding hose by external heating including the steps of first forming continuous strip of self-molding material which includes a heat-shrinkable woven fabric, a first vulcanized elastomer topping layer provided on a top surface of the heat-shrinkable woven fabric, a second vulcanized elastomer topping layer provided on an undersurface of the fabric with the second vulcanized elastomer topping layer being thinner than the first vulcanized elastomer topping layer and an unvulcanized elastomer topping layer provided on the undersurface of the second vulcanized elastomer topping layer. Then the continuous strip is overlappingly wound on a former to create a circular hose and the circular hose is continuously introduced into a gap between rotary drums of vulcanization apparatus at the same rate as the rate of the circular hose formation so that the circular hose is pressed flat, heated and vulcanized and converted into a flat hose.

Abstract: A twisted FRP structure having sufficient strength and flexibility is produced by providing a rod member disposed centrally and twist a plurality of side strands twisted around the rod member in the same direction at a predetermined pitch. At least the side strand includes a composite strand having an FRP element from by impregnating fibers with an uncured thermosetting resin and a thermoplastic coating on such FRP element, the thermosetting resin being cured after the side strands are twisted around the rod member. The twisting pitch is not less than 25 times the outside diameter of the FRP element in the side strand.

Abstract: Polypropylene articles are provided. The polypropylene articles include non-crystalline mesomorphous polypropylene having olefinic unsaturation-containing monomers graft-polymerized thereon by ionizing radiation in a dosage sufficient to degrade crystalline polypropylene. The irradiated polypropylene articles retain useful tensile properties after storage periods of as long as at least about four months.

Abstract: An improved stereolithography system and method for curing a stereolithographically-produced part, including at least some material that is no more than partially transformed, by exposing the part to off-peak-absorptive wavelengths of synergistic stimulation to achieve a more uniform cure.

Abstract: Polymeric material is plastified in an extruder and is then divided into a major part and a minor part. Either the major part or (more often) the minor part is modified by a chemical reaction, such as grafting (any necessary ingredients being added, if not already present). The major and minor parts are then recombined in an extrusion head so that the modified and unmodified materials form distinct parts of the product. In this way, a single extruder can be used to make, for instance, a product with surface characteristics modified by grafting, wire-covering with only a surface layer crosslinked, or heat-sealable crosslinked packaging film.

Abstract: Forming process, during vulcanization on a mandrel, of the end portions of rubber tubes, using a tool having a radially deformable skirt in the form of a corolla, made of vulcanized rubber which encloses the end portions of rubber tubes using solely the action of the circumferential elasticity of its corolla. The disengagement of the part after vulcanization is accomplished by a simple axial thrust on the corolla. An upturned position of the radially deformable skirt makes possible the installation of the rubber tubes and other preparation operations.

Abstract: An extruded web of synthetic resin having a scratch resistant coating thereon is made by depositing a material adapted to form a scratch resistant coating onto the return run of at least one of the endless belts of a dual belt continuous casting machine, the coating being transferred to the surface of the web as the extruded web is polished and cooled in the casting machine.

Abstract: A method for curing fiber-reinforced resin matrix composite materials (22) includes the steps of providing a form (14) and positioning uncured composite material (22) on the form (14) substantially into a desired shape. The composite material (22) is then cured by providing a fluid bath (10) heated to a predetermined temperature, and heating the composite material (22) by immersing the positioned composite material (22) on the form (14) into the fluid bath (10) for a predetermined time. The predetermined time is sufficient to allow the composite material (22) to become cured and to heat the composite material (22) at a rate sufficient to provide resin flow prior to hardening. Compressive pressure is provided on the composite material (22) while it is immersed in the fluid bath (10).

Abstract: Alkyldiamine, 1,3,5-trihydroxybenzene or 1,3-dihydroxybenzene is added as a copolymerization component to a polyfunctional aromatic amine component in the amount of 1-20% by weight with respect to the polyfunctional aromatic amine in producing a composite semipermeable membrane by laminating on a microporous substrate a polyamide formed by interfacial polycondensation between a polyfunctional aromatic amine and a polyfunctional acid halide. The composite semipermeable membrane has improved oxidation resistance while retaining excellent separation selectivity and high permeability of the crosslinked polyamide-based composite semipermeable membrane. The composite semipermeable membrane is used for desalination of brackish and sea water.

Abstract: A photosensitive composition wherein setting is retarded in the presence of air is subjected to partial setting by directing radiating light through the side in contact with air, thus setting the opposite side which is not in contact with air, with setting then completed by directing radiating light to the unset part of the composition in the absence of air. The composition is extended on a metal surface, with the surface in contact with the metal being subjected to setting, thus providing excellent smoothness. After the unset part of the composition is stuck by pressure to another unset composition or another film, the films can be adhered with radiating light. When metal rolls are utilized for the metal surfaces, continuous manufacturing can be easily achieved.

Abstract: The invention is a process for the production of solid aromatic polyamic acid and polyimide fibers from a wet gel or coagulation bath wet get using N,N-dimethylacetamide (DMAc) solutions of the polyamic acid derived from aromatic dianhydrides such as 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and aromatic diamines such as 4,4'-oxydianiline (4,4'-ODA). By utilizing the interrelationship between coagulation medium and concentration, resin inherent viscosity, resin % solids, filament diameter, and fiber void content, it is possible to make improved polyamic acid fibers. Solid polyimide fibers, obtained by the thermal cyclization of the polyamic acid precursor, have increased tensile properties compared to fibers containing macropores from the same resin system.

Abstract: A polymeric article having high temperature performance and intermediate electrical conductivity is disclosed. The article has a matrix of polyimide and a filler of conductive particulate material. The degree of conductivity is controlled by an extraction step in the manufacturing process.

Abstract: A method is shown for forming a wiper blade in which a continuous length of elastomer is extruded through a die having a die opening shaped to produce a pair of wiper blades joined in edge-to-edge relation. The elastomer is preformed to produce a weakened mid- section and then cured. The cured elastomer is then separated into two separate lengths of wiper blade by pulling the length of continuous elastomer along the weakened mid-section.

Abstract: A device fabrication method is disclosed in which a precursor polymeric or oligomeric material, capable of undergoing a curing reaction involving crosslinking and/or imidization, is at least partially cured and incorporated into the device being fabricated. Significantly, the at least partial curing is achieved by heating the material at generally increasing (although not necessarily continuously increasing) temperatures. In addition, the heat is supplied at a rate so that the temperature of the material is always maintained at or below the corresponding glass transition temperature of the material, which increases during the heating process.

Abstract: A process for preparing aromatic polyamide film wherein an aromatic diamine and an aromatic diacidchloride are dissolved in an amide polymerization solvent containing an inorganic salt, a partial polymerization is effected at a low temperature to form an optically anisotropic liquid crystalline prepolymer dope, continuously extruding through a film die under a draw ratio or subjecting to a shear and contacting the prepolymer with a second solvent which is a polymerization accelerating-precipitation solvent to obtain an aromatic polyamide film free of crystal defect layer perpendicular to the film axis and having high strength and a high degree of molecular orientation.

Abstract: Thin-walled catheters are provided which have an elongated fuseless polymeric tube that is made from a single tube of extruded polymer. The elongated fuseless polymeric tube includes a body portion that had been subjected to a high temperature zone in order to solid state polymerize and enhance the mechanical stability, burst strength and kink resistance of the body portion. Also included is a tip portion of the elongated fuseless polymeric tube which was subjected to a low temperature zone to retain the initial properties of extruded polymer.

Abstract: A process for the production of polyester polyurethane elastomeric fibers having improved humid aging resistance which comprises the steps of reacting a polyester diol with an excess molar amount of an organic diisocyanate to prepare a urethane prepolymer having terminal isocyanate group at both ends thereof; extending the chain of the prepolymer with a bifunctional active hydrogen compound and 0.5 to 10.0 mole % of a diaminosilyl compound based on the total amount of the bifunctional active hydrogen compound during or after preparation of the prepolymer to obtain a polyurethane; spinning the polyurethane into fiber; and crosslinking the polyurethane during or after spinning.

Abstract: Focusing radiation on a patterned area of a substrate upon which flowable radiation curable material is being deposited causes a dam of cured material to form which restricts the flow of the material into areas which are to remain free of material.

Abstract: Large fittings or other structures are made by rotationally moulding a first component 18 of polyethylene and joining cylindrical pups 20, 22, 24 of polyethylene to the component by butt fusion joints 26, 28, 30. The structure within the boundary 50 is irradiated with gamma radiation followed by post-heating to remove free radicals. The extremities of the pups are shielded to prevent irradiation. Their capability to be joined to polyethylene pipes 12, 14, 16 by butt-fusion joints 32, 34, 36 is unimpaired. The irradiation introduces cross-linking to give improved properties such as impact resistance and stress crack resistance and to bring the fitting within the specification for polyethylene pipe for natural gas distribution. The joints 26, 28, 30 are made using differential heating of the ends to be joined to compensate for differences in melt flow index. Alternatively, the component 18 is slightly irradiated to lower its MFI before the pups are joined to it.

Abstract: A process is disclosed for producing a composite hose constructed with a core tube, a reinforcement layer and a cover laminated one on another, the core being made up of a resin inner wall and a rubber outer wall. Gas impermeability and flexibility are enhanced by formation of the inner wall on a mandrel of selected synthetic material and specified bending strength.

Abstract: A mechanically stable, conformable collagen wound dressing sheet material is fabricated by lyophilizing (freeze-drying) a collagen composition and compressing the porous pad thus produced at a pressure between about 15,000-30,000 p.s.i. The sheet material thus produced may also be treated with optional dehydrothermal crosslinking known in the art. In addition to mechanical stability and conformability, the sheet material demonstrates high absorptivity, i.e., about 15-20 times its weight in isotonic saline, making it highly useful as a medical or surgical dressing or as a carrier for other medicaments such as antibiotics. The sheet material may be impregnated with thrombin.

Abstract: A stereolithographic method which employs an ultraviolet-curable liquid composition adapted to cure rapidly to a lightly cross-linked solvent-swellable three-dimensional complexly-shaped polymeric thin-walled element constituted by heat-softenable solid polymer upon exposure to ultraviolet dosage in the range of about 0.1 to about 10 Joules per square centimeter and which possesses reduced distortion comprises, from 20 to 80 weight percent, of a resinous polyacrylate or polymethacrylate dissolved in a combination of 10 to 45 weight percent of a liquid polyacrylate or polymethacrylate, which is preferably trifunctional, and 10 to 45 weight percent of liquid N-vinyl monomer, preferably N-vinyl pyrrolidone. Thus, the weight ratio of polyacrylate: polymethacrylate: N-vinyl monomer is about 1:2:2 to about 8:1:1. One of the foregoing polyacrylates or polymethacrylates is a polyacrylate and the other is a polymethacrylate so that good cure speed is accompanied by good distortion resistance.

Abstract: Disclosed is a process for the preparation of a composite including a room temperature vulcanizing silicone rubber and a chemically resistant polyester film which may be polyethylene terephthalate. The composite has particular utility as a part of medical equipment, for example as a component in an ultrasonic transducer. The susceptibility of the composite bond so formed to chemical challenge in the user environment is reduced or eliminated.

Abstract: A scratch resistant coating is applied to one or both surfaces of an extruded thermoplastic synthetic resin web by passing the web through a polishing roll stack wherein at least one of the rolls has thereon a film of a material forming such a scratch resistant coating, the coating being in this way transferred from the roll to the surface of the web.

Abstract: Process for producing polyester fibers of high tenacity and high modulus, by melt-spinning a polyester having an intrinsic viscosity of not lower than 0.3, to obtain extruded filaments of low orientation having a birefringence not higher than 10.0.times.10.sup.-3, post-polymerizing the filaments in a heating medium, and subjecting the filaments to multi-stage drawing in at least two stages.

Abstract: A process by which polyester resin having extremely high molecular weight can be prepared utilizing a very rapid solid state polymerization process comprises: (1) dissolving a polyester prepolymer in a suitable organic solvent; (2) recovering the polyester prepolymer from the organic solvent to produce a porous, fibrous mass of the polyester prepolymer; and (3) solid state polymerizing the porous, fibrous mass at an elevated temperature to produce the ultra-high molecular weight polyester resin.

Abstract: A plurality of abrasive sleeves (3) surround a wire rope (2) and are spaced at predetermined intervals longitudinally of the wire rope. An elastic material (4) of rubber such as natural rubber is formed between the abrasive sleeves in such a manner as to surround the wire rope. A rubber/metal bonding agent (7) such as chlorinated rubber type bonding agent is used to effect vulcanization bonding between the opposite end surfaces of each abrasive sleeve and the elastic material and between the wire rope and the elastic material. The ends (19) of the wire rope are connected together by a combination of end connecting members (5, 6a) provided with male threads (17, 17a) and fixed to the ends of the wire rope and on internally threaded connecting sleeve (30), whereby a closed loop is formed.

Abstract: A method is shown for forming a wiper blade in which a continuous length of elastomer is extruded through a die having a die opening shaped to produce a pair of wiper blades joined in edge-to-edge relation. The elastomer is scored in the mid-section thereof to produce a score line and then cured. The scored and cured elastomer is then separated into two separate lengths of wiper blade by dividing the length of continuous elastomer along the score line.

Abstract: If ultra-high-molecular-weight polyethylene having an intrinsic viscosity (.beta.) of at least 5 dl/g is grafted with a silane compound in the presence of a radical initiator and extrusion-molded and the extrudate is impregnated with a silanol condensation catalyst after or during drawing and is then exposed to water to effect crosslinking, there is obtained a novel molecularly oriented molded article in which increase of the melting temperature, which is not observed in conventional drawmolded or crosslinked molded articles of polyethylene, can be attained, and even if this molecularly oriented molded article is exposed to a temperature of 180.degree. C. for 10 minutes, the molded article is not fused but the shape is retained and even after this heat history, a high strength retention ratio can be maintained.

Abstract: A method of preparing a glass fiber-reinforced, crosslinked polymer structure which comprises saturating an uncoated, unsized woven glass fabric with a polymerizable liquid comprised of dicyclopentadiene and, optionally, one or more other metathesis polymerizable strained ring polycyclic cycloolefins, subjecting said saturated fabric to polymerization conditions, and, thereafter, post-curing the resultant structure at a temperature greater than about 225.degree. C., and a glass fiber-reinforced, crosslinked polymer prepared by that process, are disclosed. Post-curing at temperatures greater than 225.degree. C. enhances the physical properties of the woven fiber-reinforced, crosslinked polymer.

Abstract: Polyvinyl butyral (PVB) resin lightly cross-linked through stable intermolecular linkages developed, for example, through use of a dialdehyde or trialdehyde, to selectively increase PVB molecular weight and the modulus of a plasticized sheet formed therefrom intended for use in laminated safety glass assemblies.

Abstract: A method of vulcanizing a tubular article by extruding a sheath of unoriented polyethylene terephthalate about the article followed by quenching the sheath to an amorphous state. The sheathed article is then subjected to vulcanizing conditions in order to convert the sheath from the low density amorphous state to the higher density crystalline state, thus compressing the article to effect a smooth finish.

Abstract: A method for producing an optical disk base to store, record, and retrieve sounds, images, and information. An improved method for producing an optical disk base includes the steps of injecting a photo-curable resin into a cavity, curing the photo-curable resin by irradiation with light, and demolding, where the photo-curable resin is injected from an injection nozzle having an outside diameter which is substantially equal to the diameter of the center hole of the optical disk base and also having a horn-shaped opening at the forward end. The injection nozzle is arranged at the center of the optical disk base. The forward end of the nozzle is closed after injection and the photo-curable resin is irradiated with light, with the injection nozzle projected into the cavity. A liquid resin is injected in the form of uniform flow without entrapped bubbles, so that the anamolous molecular orientation is avoided and the contamination with insufficiently cured or uncured resin is also avoided.

Abstract: An inflatable packer construction where the inflatable elastomer element is; (1) constructed from the same type of rubber compound from end-to-end the rubber is cured differentially from end-to-end so that inflation is from one end to the other end; (2) is constructed of rubber having different characteristics from end-to-end so that the cured rubber will inflate from one end to the other end; (3) is constructed of rubber having a release agent between one end of the rubber and a mandrel so as to release one end of the rubber first from the mandrel upon inflation; (4) is constructed of rubber having different thicknesses from end-to-end so that one end inflates sooner than the other end; or (5) is constructed of rubber with a segment of the length of the element having a releasably confining element.

Abstract: A continuous process method of molding composites. The method includes substantially filling a pressure chamber with a solid flowable polymer. The pressure chamber has a series of subchambers separated by a series of spaced apart baffles, but connected through baffle openings. A tube connects at least two subchambers, a transferring subchamber and a receiving subchamber. The polymer is displaced through the tube producing a polymer flow in the chamber through the baffle openings from the receiving subchamber to the transferring subchamber causing the receiving subchamber to have a higher pressure than the transferring subchamber. A composite precursor is passed through the pressure chamber by entering the precursor through the low pressure transferring subchamber wherein the composite precursor is exposed to pressure caused by the solid flowable polymer in order to cure the composite.

Abstract: A fiber/resin composite whose resin phase is formed by at least initial actinic radiation curing of a resin composition comprising an actinic radiation curable first resin component and a second resin component which is non-cured under curing conditions effective for the first resin component. The actinic radiation exposure of the fiber/resin composition effects curing of the first resin component to immobilize the composite and impart structural integrity thereto, whereby the composite may be handled, packaged, or further processed. Filament wound, braided, and pultruded articles are described, together with associated methods for forming such articles by filament winding, braiding and pultrusion. As a specific embodiment, a solid fuel rocket motor is disclosed comprising a solid fuel body in a filament wound fiber-resin composite casing formed by filament winding of the solid fuel body with resin-impregnated filament or rovings thereof.

Abstract: A crosslinked and oriented polyethylene film superior in clarity as well as moistureproofness and having an improved stretchability is produced by a process for producing a crosslinked and oriented polyethylene film such that the degree of crosslinking inwardly decreases across the thickness of the film, comprising using a polyethylene having a density of at least 0.935 g/cm.sup.3, a melt index of 0.5 to 20 g/10 min and a high-load melt index to melt index ratio of 40 to 200.

Abstract: A method of producing a reinforced rubber hose, including the steps of continuously extruding a long plastic mandrel from a plastic material and feeding the extruded plastic mandrel, extruding an unvulcanized inner rubber tube on the long plastic mandrel, forming a tubular reinforcing layer on the unvulcanized inner rubber tube, extruding an unvulcanized outer rubber tube on the tubular reinforcing layer, vulcanizing the unvulcanized rubber tubes, thereby preparing a long rubber hose formed on the long plastic mandrel, cutting the long rubber hose into short rubber hoses having a predetermined length, while concurrently cutting the long plastic mandrel into short plastic mandrels, removing the short plastic mandrels from the short rubber hoses, and crushing the short plastic mandrels into a starting form of the plastic material, and returning the starting form of the plastic material to an extruder for continuously extruding the long plastic mandrel.

Abstract: The invention provides a method of molding a plastics material comprising the steps of placing the material with a quantity of an appropriate catalyst in granular (including powdered) form into a hollow mold shell; suspending the mold in a mounting system enabling rotation in a plurality of directions whereby the powdered material, together with the catalyst, is able to flow over all the interior surfaces; containing the mold and mounting system within an oven and heating the mold therein while rotating the same; cooling the mold and subsequently withdrawing the molded article therefrom.

Abstract: A process for extruding a hydrolyzable particulate thermolastic copolymer coated with an organic peroxide, which, under extrusion conditions, will provide essentially no crosslinking per se, but will decompose to provide a silanol condensation catalyst, including passing the coated copolymer through an extruder having a die at about its downstream end with the proviso that the extruder is operated under such conditions that (i) the temperature of the extruder before the die is maintained at a level sufficient to extrude the copolymer, but below the decomposition temperature of the organic peroxide; (ii) the temperature of the extruder at or after the die is maintained at or above the decomposition temperature of the peroxide; and (iii) there is sufficient moisture in the environment to crosslink the copolymer in the presence of a silanol condensation catalyst.

Abstract: A shaped and drawn aromatic imide polymer article, for example, a film or filament, is produced by shaping an aromatic polyamic acid solution containing an imidizing agent in a polar organic solvent while simultaneously imidizing a portion of the aromatic polyamic acid to an extent such that the resultant self-supporting precursory article contains 20% to 87% by weight of a volatile substance and has a tensile strength of at least 1.5 kg/mm.sup.2 and an ultimate elongation of at least 30%, by drawing the precursory article at a draw ratio of 1.3 or more and by heat-treating the drawn article at a temperature of 150.degree. C. or more.