Abstract: A protective, impact resistant material and method which includes a fabric of thermoplastic polymeric fibers having a strength of at least 0.5 GPa and an elastic modulus of at least 25 GPa and a matrix of polymeric material disposed in the interstices between the fibers having an elastic modulus of 0.2 to 3.times.10.sup.6 psi. The polymeric fibers can be gel spun, polyethylene, polypropylene, nylon, polyvinyl alcohol and polyethylene terephthalate. In a second embodiment, the matrix is derived from the fabric.

Abstract: The present invention provides a method enabling segregation of the various ingredients making up the polymer based products into component product streams and collection of these component streams so as to form individual product streams. Thus, according to this invention there is provided a process for purposefully segregating polymer-polymer and polymer-additive mixtures. The process for segregating the various combinations of components may be advantageously used on the one hand for the production of separate product streams from a mixture of polymers or polymer-additives in, for example, recycling of waste plastic based products, or on the other hand, in the production of polymer-polymer or polymer-additive layered structures exhibiting preselected spatial segregation of the various components. In its simplest form, the polymer segregation part of the process consists of a tube added to an extruder. During segregation, polymer layers containing different blend compositions are formed.

Abstract: An apparatus for cooling tires at the end of their vulcanization which includes:a frame having a base intended to be mounted on the ground, defining a horizontal orientation;two shafts mounted for rotation on said frame, substantially parallel to each other and substantially parallel to the horizontal, at a distance from each other less than the outside diameter of the tires to be handled;a drive for rotating at least one of the two shafts;so that, when a tire is placed on said shafts with the axis of rotation of said tire arranged substantially parallel to the axes of said shafts, said drive for placing in rotation being activated, said tire is subjected to a gyroscopic force and remains in equilibrium.

Abstract: A chassis is formed of a one-piece thermoplastic or thermosetting resin body. A bottom member extends in a bottom plane, and has at least three side members extending in respective planes. Junction portions join the bottom member and the side members. Ribs are intermittently molded as one piece to bottom member and to side member and extend from the bottom plane from the bottom member through the junction portion to the side plane of the side member. An opening portion helps to prevent angular deformation of the resin body between the bottom member and the side member from a desired angle between the bottom plane and the side plane when the one-piece body is molded by minimizing differences in the cooling rate at different parts adjacent to the junction portion in the one-piece body. The opening portion is located between the ribs at least adjacent to and along the junction portion. The opening portion has a length along the junction portion that is at least five/ten the length of the junction portion.

Abstract: A method and apparatus is provided for controlling the reconfiguration of a moulded boat hull structure as it is cooled from its moulding temperature to ambient temperature. A dynamic cooling fixture is utilized having movable panels that support substantially the entire inner and outer hull surfaces during the entire cooling process. This results in the cooling of the hull in a manner which will be devoid of wrinkles, depressions, or other disadvantageous discontinuities.

Abstract: An EMI shield for personal computers, cellular telephones, and other electronic devices is constructed from thermoformable polymeric material which is then metallized on all surfaces by vacuum metallization techniques to provide an inexpensive, lightweight, yet effective EMI shield.

Abstract: A distinctive technique for making a microporous film includes a stretching of a layer composed of a polymer material and at least about 5 wt % of a particulate filler material. The particulate filler material has been distinctively treated with an operative amount of surface-active material having a HLB value of not less than about 6. Desirably, the stretching includes a biaxial stretching of the polymer layer.

Abstract: A treating method for improving the strength of molded products. Molded products of a thermosetting resin containing a phenol resin as a main component are taken out of a mold of an injection molding machine, and then immediately immersed in water or exposed to blown air. With this treatment, the breaking strength, particularly the toughness of the molded products is increased. This method provides molded products having a large strength at room temperature as well as at temperatures around 120.degree. C.

Abstract: A molded article of a syndiotactic polypropylene having excellent transparency in which a melting point attributed to the polypropylene having the syndiotactic structure measured at a heating rate of 10.degree. C./minute by differential scanning thermal analysis is represented by a substantially single peak, the aforesaid molded article being prepared by heating, melting and then hot-molding a homopolymer of propylene or a copolymer of propylene and a small amount of another olefin, which have a substantially syndiotactic structure, or a mixture of the homopolymer or the copolymer and a small amount of a polypropylene having a substantially isotactic structure, followed by quenching, or, after these steps, additionally subjecting the above molded article to a heat treatment at a temperature of less than its melting point. A method for preparing the above molded article is also disclosed here.

Abstract: A method of producing reformed crosslinked polymer articles provides reformed crosslinked articles free of visible and objectionable folds, seams, and interfaces on reformed surfaces thereof. In a preferred embodiment, a method includes the steps of extruding a silane-grafted polyethylene tube, heating an end of the tube, reforming the end of the tube to produce a radially enlarged sealing surface thereon, cooling the reformed tube, and curing the reformed tube to produce an increase in the degree of crosslinking of the polyethylene material.

Abstract: A process for eliminating post-molding fabric curl and distortion in molded fabrics and fabrics produced thereby. The molded fabrics are laminates including a non-woven fabric face and a binder layer and/or sheet backing. Post-molding curling and distortion can be eliminated by maintaining heat on the face fabric until the backing has been cooled enough to be rigid.

Abstract: A spa having a one-piece, rotationally molded shell defining a reservoir for containing water including at least three sidewalls connected by an interior footwell, at least three exterior sidewalls, a coping interconnecting the reservoir sidewalls and the exterior sidewalls, and a floor beneath the reservoir footwell and interconnecting the exterior sidewalls. Water is circulated within the reservoir by a plumbing system which is disposed within an interior space defined between the reservoir sidewalls, the exterior sidewalls, the coping, and the floor; the plumbing system including a plurality of jets extending through the reservoir sidewalls; a plumbing harness; and a pump for circulating the water from the reservoir into the jets. It is also contemplated that a filter system and heating element may be provided and enclosed within the interior space of the spa.

Abstract: By poststretching, at a temperature between about 135.degree. and 160.degree. C., a polyethylene fiber, which has already been oriented by drawing at a temperature within 5.degree. C. of its melting point, an ultra high modulus, very low creep, low shrink, high tenacity polyolefin fiber having good strength retention at high temperatures is obtained. The poststretching can be in multiple stages and/or with previous annealing. The poststretching should be done at a draw rate of less than 1 second.sup.-1. Tensile modulus values over 2,000 g/d for multifilament yarn are consistently obtained for ultrahigh molecular weight polyethylene, with tensile strength values above 30 g/d while at the same time dramatically improving creep (at 160.degree. F. (71.1.degree. C.) and 39,150 psi load) by values at least 25% lower than fiber which has not been poststretched. Shrinkage is improved to values less than 2.5% of the original length when heated from room temperature to 135.degree. C.

Abstract: An improved plastic knuckle pin for a coupler on a railway car and a method of making the improved plastic knuckle pin whereby the improved plastic knuckle pin has a substantially uniform material matrix and the method of making the pin increases uniformity in the material by increasing the surface cooling area which decreases air and moisture pockets in the material during the molding process.

Abstract: Method and apparatus for cooling porous materials whereby first gases are passed through a porous material, such as polyurethane foam, in a first zone at a predetermined flow rate to cool the porous material and to remove volatiles therefrom in a first gas mixture which exits the porous material at a predetermined temperature. The first gas mixture is combined with second gases having a temperature which is lower than that of the first gas mixture to form a second gas mixture having a temperature which is sufficiently low to condense or sublime one or more of the volatiles. Thereafter, the second gas mixture is passed through the porous material to filter the condensed or sublimed volatiles thereon and to further cool the porous material. The flow rate of the heated gases is controlled to provide a controlled uniform cooling of the porous material, and additional filters may be utilized to remove particulate matter from either of the heated gases or the cold gases, or both.

Abstract: The present invention provides a method for the semi-continuous production of microcellular foam articles. In a preferred embodiment, a roll of polymer sheet is provided with a gas channelling means interleaved between the layers of polymer. The roll is exposed to a non-reacting gas at elevated pressure for a period of time sufficient to achieve a desired concentration of gas within the polymer. The saturated polymer sheet is then separated from the gas channelling means and bubble nucleation and growth is initiated by heating the polymer sheet. After foaming, bubble nucleation and growth is quenched by cooling the foamed polymer sheet.

Abstract: A composite material is formed by combining a liquid crystal polymer with a porous or nonporous support membrane to provide either a thin, multiaxially oriented liquid crystal film on the support membrane formed by laminating the liquid crystal polymer onto a porous or nonporous support membrane, followed by multiaxial orientation; or to provide a thin, multiaxially oriented liquid crystal polymer region within a porous support membrane formed by impregnating the liquid crystal polymer into a porous support membrane, followed by multiaxial orientation.

Abstract: In an apparatus and process for manufacturing a thermoplastic sheet or film having superior optical characteristics such as improved transparency, gloss and surface smoothness, a thermoplastic sheet is extruded, passed between a cast drum and an endless metallic belt while being compressed and subjected to a primary cooling by the belt and drum. The sheet or film is secondarily cooled in a water bath, after which it is dewatered and subjected to a thermal treatment at a temperature in the range of 40.degree. C. below, to 15.degree. C. above the thermal deformation temperature of the resin sheet to produce the improved sheet of the invention. In addition to producing a film or sheet with improved characteristics, the apparatus of the invention allows production of sheets or films at a rate up to about 10 m/min.

Abstract: A system for curing composite structures. A hollow bladder having opposing open ends is secured within a metal pressure vessel so as to define an annular space within the vessel surrounding the bladder. The open ends of the bladder are sealably attached to opposing entrances formed in the pressure vessel so that the bladder is sealed from communication with the vessel and is accessible through the opposing openings. An uncured composite part can be inserted into the bladder. Preheated and pressurized fluid is circulated through the annular space and thus around the bladder in order to cure the composite part. The composite part may also be encapsulated within a forming bladder member which is then removably inserted into the pressure bladder.

Abstract: A method is provided for creating a plastic component constructed, at least in part, from polychlorotrifluoroethylene, having improved properties. The method creates a component from a composition that has polychlorotrifluoroethylene, heats the component to a temperature that is greater than the melting point of the composition, and rapidly quenches the component in a cold medium.

Abstract: Method for making laminated glass, whereby a film (2) of polyvinyl butyral is applied between the glass layers (1) whose surface has obtained a roughness at a temperature above 120.degree. C.

Abstract: Substrates (D) for optical recording disks are supported substantially vertically while moving through a shroud (32) through which cooling gas is drawn or pumped. The substrates may be supported by spaced, toothed rings (18, 20, 24) on a carousel or by suitable conveyors (126-132; 136-142; 144-146).

Abstract: A process for producing a cylindrical product of a fiber reinforcement-thermoplastic resin composite, which involves disposing a mandrel on a flexible guide sheet which can be formed in the shape of the letter U around the mandrel, heating a fiber reinforcement-thermoplastic resin composite sheet to a temperature not lower than the distortion temperature of the resin and lower than the thermal degradation temperature of the resin of the composite, disposing an end of the heated composite sheet at a line of contact of the mandrel with the flexible guide sheet, then rolling the mandrel on the guide sheet while moving the guide sheet, the guide sheet forming a shape of the letter U around the mandrel being drawn into the concave portion of the letter U, and the composite sheet disposed between the mandrel and the guide sheet being in intimate contact with the mandrel and the guide sheet, to thereby wind the composite sheet on the mandrel, and then recovering a cylindrical product made from the wound composite sh

Abstract: A molded article is formed of a thermoplastic or thermosetting resin and has two planes joining each other in a junction portion; at least one of the two planes has an opening portion or a thin wall portion in the vicinity of the junction portion in order to decrease warpage of the molded article.

Abstract: A method of manufacturing an etched extrusion, the method comprising the steps of extruding a thermoplastic material to produce a hot extrusion, and contacting the extrusion, while the extrusion is still hot, with a mixture of at least two fluids having different thermal conductivities so that the extrusion develops an uneven outer surface due to different rates of shrinkage caused by the different thermal conductivities.

Abstract: The present invention is directed to polymeric bone fixation devices and processes for making the devices. In making the bone fixation devices, a polymeric material having a crystalline portion is deformed by a compressive force along a particular direction which causes molecular chains contained within the polymer to orient. The resulting polymer has increased mechanical properties including increased tensile strength and modulus. The polymeric material used to make the bone fixation device can be a bioabsorbable polymer which, once implanted, is broken down and absorbed by the patient's body, eliminating the need for removal.

Abstract: In a method of forming a hollow product in a molding apparatus having an upstream and a downsteam end a parison of thermoplastic material is extruded in a molten state from a heated extruder at the upstream end and moved through a product shaping region towards the downstream end of the apparatus. The material is cooled by passing a cooling medium internally of the product from the downstream end towards the upstream end of the apparatus.

Abstract: The method includes disposing a liquid monomer or a monomer mixture and a photosensitive initiator into a mold cavity defined by mold members and directing ultraviolet light to act on the lens forming material in the cavity to produce a lens therefrom. The mold members are cooled by air.

Abstract: Rapid cooling of molded workpieces such as PET parisons formed in an injection molding machine is provided by a receiver receiving molded workpieces upon ejection from the molding machine, the receiver being transported out of the molding machine to an adjacent position where a cooling head coupled to a source of cooling fluid such as liquid nitrogen directs the fluid toward the surfaces of each workpiece. The cooling head engages and is sealed to the receiver to inhibit the escape of cooling fluid into the atmosphere thereby reducing cost, environmental impact, etc. A cooling program control coupled to the cooling fluid source supplies a discontinuous flow cooling fluid from said source to contact the workpieces only when the cooling head is engaged with and sealed to the receiver. A vacuum unit withdraws cooling fluid from the receiver subsequent to contact between the workpieces and the cooling fluid. The cooling fluid can then recooled and recycled for reuse.

Abstract: Disclosed is a method of producing a barrier fabric having stretch and recovery properties. The method includes the steps of heating at least one nonwoven web containing meltblown non-elastic thermoplastic polymer fibers to a temperature at which the peak total energy absorbed by the nonwoven web of meltblown fibers is at least about 250 percent greater than the amount absorbed by the nonwoven web of meltblown fibers at room temperature; applying a tensioning force to neck the heated nonwoven web; and cooling the necked nonwoven web so that the nonwoven web has at least the same hydrostatic head and/or particulate barrier properties as the nonwoven web before necking. Also disclosed is a stretchable barrier fabric composed of a nonwoven web of meltblown non-elastomeric thermoplastic polymer fibers, the nonwoven web being heat treated so that it is adapted to stretch at least about 10 percent more than an identical untreated nonwoven web of meltblown non-elastomeric thermoplastic polymer fibers.

Abstract: This invention relates to a low heat release, low density, fiber-reinforced composite comprising a matrix comprising a thermoplastic polymer selected from the group consisting of polyarylsulfone, polyethersulfone, polyetheretherketone, polyetherketoneketone, a copolycarbonate of 4,4'-thiodiphenol and at least one member of the group consisting of bisphenol A, 9,9-bis(4-hydroxyphenyl) fluorene, and 1,1-bis-(4-hydroxyphenyl)-1-phenyl ethane, a copolycarbonate of bisphenol A and 9,9-bis(4-hydroxyphenyl) fluorene, 1,1-bis(4-hydroxyphenyl)-1-phenyl ethane polycarbonate, bisphenol A polycarbonate, and polyetherimide, and from about 10 to about 70 percent by weight of the composite of randomly oriented reinforcing fibers, less than 0.5 inch in length, distributed throughout the matrix. The matrix has a void volume of from about 20 to about 90 percent by volume. The composite has a thermoplastic skin layer on each of the major surfaces thereof. A process for making the composite is also disclosed.

Abstract: A polyolefin-based matte film or sheet can be prepared from a polymeric blend of the preset invention comprising a propylene polymer or copolymer as component (A), a specific ethylene-.alpha.-olefin copolymer (E.alpha.O, so-called "super low-density polyethylene") as component (B), and a high-pressure radical polymerization process ethylene polymer or copolymer and/or a modified polyolefin-based resin as component (C). The above blend of the present invention may further comprise an inorganic filler as component (D) and a flame retardant as component (E). The matte films or sheets prepared from these polymeric blends are excellent in tensile modulus, flexibility, impact resistance, thermal resistance, laminating properties, flame resistance, chalking resistance, covering power, scratch resistance, and widely used for fabricating adhesive tapes, covers or cases for stationery, fashion bags, sheets for interior finish work in construction and automobile industries, and sheets for dressing steel plates.

Abstract: The invention concerns a process for manufacturing a strip of ski-coating material made of polyethylene of ultra high molecular weight, wherein a ski-coating strip material 4 manufactured to a thickness of 0.5 to 1.5 mm by a screw extruder, a ram extruder or press sintering with subsequent peeling is made to pass continuously first through a heating zone 1 in which it is heated to temperature above 140.degree. C. and then through a cooling zone consisting of two sizing plates 2, 2' in which it is cooled to a temperature equal to or lower than ambient. This process produces a ski coating of which the crystalline proportion can be adjusted within a range of 25 and 60%, as a result of which improved gliding by the ski coating on snow and improved wax acceptance is assured in comparison with the known methods.

Abstract: A process for upgrading low-quality wood including a softening stage, wherein one or more sections of low-quality wood are heated, in the presence of an aqueous medium and at a pressure which is at least the equilibrium pressure of the medium at the operating temperature, to a temperature in the range of from about 120.degree. C. to about 160.degree. C. and maintaining the temperature until the temperature difference between the center and the outer parts of the sections is less than about 20.degree. C., a dewatering stage and a curing stage.

Abstract: An apparatus for producing an optical recording medium in a sheet form, having a resin melt-extruding device that forms a resin sheet, a first heated roller having a predetermined unevenness pattern, and a second heated roller disposed opposite thereto. Further, the apparatus has a conveying device that conveys the resin sheet, in a substantially melted state, between the first and second rollers, which transfer an unevenness pattern to a surface of the resin sheet. The apparatus also has a temperature control device to gradually cool the resin sheet.

Abstract: The invention proposes an improved process and a device for cooling the internal surface of the wall of a pipe made of plastic during its manufacture by extrusion. The cooling agent is dispersed on the internal surface of the pipe by successive atomization at given time intervals. The cooling agent is advantageously dispersed by means of an injection which is displaced axially inside the pipe in a reciprocating movement. The injector may be advantageously equipped with means providing a rotating cone of dispersed droplets.

Abstract: A bending process including both preliminary and following steps takes place in one apparatus. A plastic pipe (6) is heated to a temperature in which it can be plastically deformed. The heated pipe is thereafter shoved into a pipe-shaped bending channel (27) of a bending tool, with the bending tool comprising two dies (9,10), each respectively defining a groove (14,13) which together form the bending channel. Finally, a cooling agent is allowed to flow through the bent pipe which is still in the bending tool. The thusly cooled pipe is removed from the bending tool after the dies are separated from one another. The apparatus to bend the plastic pipe comprises heating, bending, and cooling stations (1,2,3). The heating station comprises two heating fixtures, and the cooling station comprises a supply line (21,22) with a coupling joint (20) which can be coupled to an end of the pipe.

Abstract: Method and apparatus for cooling porous materials whereby first gases are passed through a porous material, such as polyurethane foam, in a first zone at a predetermined flow rate to cool the porous material and to remove volatiles therefrom in a first gas mixture which exits the porous material at a predetermined temperature. The first gas mixture is combined with second gases having a temperature which is lower than that of the first gas mixture to form a second gas mixture having a temperature which is sufficiently low to condense or sublime one or more of the volatiles. Thereafter, the second gas mixture is passed through the porous material to filter the condensed or sublimed volatiles thereon and to further cool the porous material. The flow rate of the heated gases is controlled to provide a controlled uniform cooling of the porous material, and additional filters may be utilized to remove particulate matter from either of the heated gases or the cold gases, or both.

Abstract: An improved two membered substantially crack-free water jet mixing tube of an abrasive water jet cutting device and a method of its preparation. The method comprises chemically vapor depositing diamond layer on a funnel shaped support member to form an inner member of the mixing tube, separating the inner member from the support member, depositing and then cooling an outer member on the outer side of the inner member to produce a compressive stress on the inner member that substantially prevents formation cracks on the inner member. The inner side of the inner member has a smooth bore having a microcrystalline structure and the outer member has a higher coefficient of thermal expansion than diamond. The invention is also directed to a water jet cutting device that incorporates the aforementioned improved substantially crack-free water jet mixing tube.

Abstract: The present invention relates to hydraulically bonded cement compositions and methods of manufacture. Hydraulically bonded cement compositions and methods of manufacture include materials prepared by manipulating under pressure powdered hydraulic cement compositions using known or novel powder packing, casting, or expanding techniques, such that air within the powdered hydraulic cement is successfully removed while the cement is formed into a self-supporting near net final position. Thereafter, the formed hydraulic cement article is hydrated without mechanical mixing of the cement and water.

Abstract: Incorporation of solid removable aggregates into powdered cement which later completely dissolve, evaporate, volatilize, or melt leaving voids in the cement composition is discussed. Cementitious articles are prepared by manipulating powdered hydraulic cement or cement paste compositions into mechanically self-supporting structures of a predetermined configuration and thereafter hydrating the hydraulic cement compositions without mechanical mixing of the cement and water.

Abstract: A method producing deformed pipe liners from continuously extruded thermoplastic material by collapsing and bending deformable portions of the tube toward a back-up portion thereof and without elongation to maintain diameter and wall thickness, and apparatus to carry out said method and characterized by at least one back-up roller and at least one shaping roller folding the deformable portion along a line of symmetry and juxtaposing a fold of the tube to the back-up portion, all at raised temperature followed by reduced temperature on a rail conforming to the deformed tube configuration.

Abstract: A process and an installation for producing a drip irrigation conduit having discrete internally located emitter units bonded at axially spaced apart locations of an internal surface thereof, wherein the irrigation conduit is continuously extruded from an extrusion cross head at a first outer diameter and a first linear velocity and is drawn off through a calibrator unit to a second and lesser outer diameter at a second and greater linear velocity greater than the first linear velocity, the emitter units being continuously supplied on a carrier member which extends from within the extruder cross-head to the region of an inlet of the calibrator unit.

Abstract: Process to cool and pelletize molten strands, which issue from nozzles and are first stretched in the region following the nozzles and then are cooled for the pelletizing operation. The strands are gently cooled up to a kneadable state while stretching and compacting along a tempering region, which is designed as a fluidized bed driven with gas, in particular air, and subsequently conveyed into an intensive cooling region, where the strands are chilled with cooling water and are substantially hardened, while feeding so as to cause stretching, for the subsequently pelletizing operation.

Abstract: Disclosed are a material for extrusion molding comprising a styrene-based polymer having a high degree of syndiotactic configuration, a melt viscosity of 10.sup.3 to less than 10.sup.6 poise measured at 300.degree. C. and a shearing rate of 10/sec, and a crystallinity of 15% or more, a process for preparation of the said material and a process for preparation of a molding product therefrom.The molding product prepared according to the present invention has excellent properties such as heat resistance and chemical resistance.

Abstract: A process for dimensionally stabilizing an article molded from a synthetic resin material, such as PVC. The molded article is subjected to a first cooling treatment to cool the article at a temperature lower than the glass transition temperature Tg of the synthetic resin followed by a heating treatment at a temperature higher than the glass transition temperature Tg and then is subjected to a second cooling treatment again at a temperature lower than the glass transition temperature Tg. Following such treatment steps, the molded article, such as side molding for automobiles, have less variation in dimensions and less shrinkage after molding in use.

Abstract: A method of fabricating micron-range holes in elastic barrier materials which involves securing an elastic barrier material to a restraining ring and removing a limited portion of the elastic barrier material so as to form a hole having a diameter of less than 0.5 to 10 .mu.m. The portion of the elastic barrier material which is removed may be removed by a drilling, punching or clipping process.

Abstract: A film molding apparatus and molding method wherein a gel state film is immersed in a vessel of a film supply unit. The film contains at least 50 weight % swelling agent relative to a polymer constituting the film. The vessel is filled with soaking liquid which acts so as not to destroy a swelling condition of the film caused by the swelling agent. Specifically, the molding method includes the steps of providing the above-noted film, heating a mold press die used for molding the film, press-molding the film in the press die and substantially drying the film by evaporating the swelling agent.

Abstract: Processes for producing oriented films of semicrystalline thermoplastic polymers, such as polyimides, and films produced thereby are disclosed. One process includes partial crystallization or imidization, orientation and further crystallization or imidization. Another process includes rendering a film of semicrystalline thermoplastic polymer amorphous, orienting the film and introducing crystallinity.

Abstract: A process for preparing thermoinsulating and structural formal articles in which(a) a thermoplastic polymer sheet is heated at a temperature above its softening point;(b) the heated thermoplastic polymer sheet is thermoformed on a thermoinsulating foamed preform made of substantially the same polymeric material; and in which(c) prior to the thermoforming in step (b), the thermoinsulating foamed preform is cooled to prevent excessive collapse of the surface of the thermoinsulating foamed preform resulting from contact with the heated sheet.