Abstract: The invention relates to a novel process for the manufacture of very low molecular weight polyphenylene ether resin, typically within the intrinsic viscosity range of about 0.08 dl/g to about 0.16 dl/g as measured in chloroform at 25° C. The method preferably comprises 2,6-dimethylphenol as a monovalent phenol species. The invention also relates to the polyphenylene ether resin made by the process as well as blends and articles containing the polyphenylene ether resin made by the process.

Abstract: The invention relates to a novel process for the manufacture of very low molecular weight polyphenylene ether resin, typically within the intrinsic viscosity range of about 0.08 dl/g to about 0.16 dl/g as measured in chloroform at 25° C. The method preferably comprises 2,6-dimethylphenol as a monovalent phenol species. The invention also relates to the polyphenylene ether resin made by the process as well as blends and articles containing the polyphenylene ether resin made by the process.

Abstract: In the method of producing a hollow foamed plastic body from polyethylene or polypropylene by means of an extrusion blow-molding process using a single-screw extruder and a blow-molding tool, the plastic material is foamed by means of a chemical blowing agent, and a pre-molded tube blank formed from the foamed plastic material is blow-molded in the blow-molding tool. The blow-molding tool has a tool surface temperature of at least 35.degree. C. over at least one portion of the surface. A blowing agent that decomposes endothermically and provides a nucleation effect is included in a blowing-agent master batch based on high density polyethylene. The master batch has an average grain size of about 1 mm and the pre-molded tube blank is blow molded at a pressure of from 0.5 to 2.0 bar, or the pre-molded tube blank is blow-molded in an interval blow-molding process with a blow-molding pressure of from 3 to 10 bar, preferably 8 to 10 bar, in a first time slot and a blow-molding pressure of from 0.5 to 1.

Abstract: An extruded composite structural artificial lumber product is manufactured from wood fiber and polyethylene, including recycled polyethylene, by reducing the wood fiber and polyethylene each to a finely divided particles, mechanically mixing the wood fiber and polyethylene particles together with a measured amount of a powdered endothermic foaming agent, mechanically mixing the mixture, without pre-pelletization, in a twin-screw extruder where it is compressed and heated until it becomes plastic and homogenous, and then extruding the plastic mixture, using vacuum to remove vaporized moisture and other excess volatiles, through a molding die which forms structural profile of the desired product.

Abstract: Methods and compositions are described that provide three-dimensional fibrillar matrices useful as, among other things, structural prosthetics and scaffolds for cells. The porous fibrillar matrices of the present invention have desirable mechanical properties suitable to a variety of applications, including platforms for in vitro cell cultivation, implants for tissue and organ engineering, implants as tendon and facia prosthetics, and product packaging.

Abstract: A method of producing an extruded plastics foam of enhanced physical strength includes intimately mixing a blowing agent incorporation CO.sub.2, the major portion of which is a natural gas, in a plastics resin melt to form a homogenous resin mix, and extruding the resin mix through an exit die into a region of lower pressure. At the point of extrusion out of the exit die, the temperature of the resin mix is adjusted so that it is below the critical temperature.

Abstract: In one embodiment, the present invention relates to a process for preparing foam board or sheet including the steps of (A) forming a foamable mixture of (1) a major amount of a styrenic polymer having a high melt index, (2) a minor amount of a low melt index styrenic polymer, and (3) a blowing agent containing a major amount of carbon dioxide under a pressure sufficient to prevent prefoaming of the mixture, and (B) foaming the mixture into a region of reduced pressure to form a foam product.

Abstract: A conductive quasi-solution useful for making a homogeneously conductive single-phase polyurethane, comprising a transition metal salt, a carrier solution, and a dispersing agent, wherein said conductive quasi-solution has a transition metal salt concentration between 10 and 30% by weight, and methods of making thermoset and thermoplastic polyurethane polymers therewith.

Abstract: Polymer foam articles having a substantially smooth surface prepared by melt-mixing a polymer composition and a plurality of microspheres, at least one of which is an expandable polymeric microsphere, under process conditions, including temperature and shear rate, selected to form an expandable extrudable composition; and extruding the composition through a die.

Abstract: New cross-linked polymeric foam compositions, and methods for making the same, are provided. The new compositions utilize novel cross-linked polyolefin copolymers and show improvements in strength, toughness, flexibility, heat resistance and heat-sealing temperature ranges as compared to conventional low density polyethylene compositions. The new compositions also show processing improvements over linear low density polyethylene. The novel polyolefins, which are essentially linear, comprise ethylene polymerized with at least one alpha-unsaturated C3 to C20 olefinic comonomer, and optionally at least one C3 to C20 polyene, and exhibit, in an uncross-linked sense, a resin density in the range of about 0.86 g/cm.sup.3 to about 0.96 g/cm.sup.3, a melt index in the range of about 0.5 dg/min to about 100 dg/min, a molecular weight distribution in the range of from about 1.5 to about 3.5, and a composition distribution breadth index greater than about 45 percent.

Abstract: A capsule is formed from a pre-expanded foam core in a compressed condition with a thermoplastic outer covering completely enveloping the foam core to maintain it in the compressed condition. The outer covering is made of a material capable of softening sufficiently when heated to permit the foam core to expand toward its original expanded uncompressed condition. Preferably, the outer covering adheres to the foam and then is carried by the expanding foam into intimate contact with the inner surface of a hollow structural member so as to form a seal for the hollow structural member.

Abstract: Heat-curing, expanding mouldings based on solid polybutadiene rubber and vulcanization systems free from elemental sulfur are distinguished by the following advantageous properties: in the uncured state in which they are supplied, they have minimal rubber-elastic resilience and are readily formable. During the curing process, no unpleasant odors are given off and, after curing, a soft and elastic foam with a continuous outer skin is formed.

Abstract: Molded polyolefin articles of improved dimensional stability at elevated temperatures and improved stiffness and consist of mixtures of modified propylene polymers, which are synthesized by free radical coupling reactions or polymer-like reactions of functionalized polypropenes, and of unmodified propylene polymers, crystalline copolymers of propylene and .alpha.-olefins, elastic copolymers of ethylene and .alpha.-olefins, largely amorphous polypropylenes, non-isotactic propylene homopolymers, and auxiliary materials.The molded polyolefin articles, produced by blow molding or injection molding are suitable for use in the packaging industry, for use in the domestic appliances industry, to meet the requirements of laboratories and hospitals, for gardening and agricultural implements, for transporting containers for components in the automobile industry, and for components of machines and of electric and electronic equipment.

Abstract: There is provided a biodegradable filter tow or filter material from renewable raw materials for the use as a tobacco smoke filter element of cigarettes, cigars or pipes as well as a method for preparing it, wherein fibers, films or foams prepared in an extrusion method from biopolymers based on thermoplastic starch or its polymer compositions are processed to the filter tow or filter material according to the present invention.The advantages of this invention reside in the use of mainly renewable raw materials, a fast and complete biodegradability of the natural biopolymer filter material, a pollutant-reducing flavor-increasing filtering effect and an economically favorable preparation method.

Abstract: By employing a unique manufacturing process, unique manufacturing equipment, or a unique combination of materials, a fully integrated, multilayer foamed thermoplastic or elastomeric member or profile having a core member peripherally surrounded by an outer protective layer is attained which is virtually incapable of being removed from said core member. By effectively melting the adjacent surfaces of the foamed layers being interengaged, a core member having any desired cross-sectional shape is produced and is peripherally surrounded with an outer layer integrally bonded thereto. In one aspect of the present invention, metallocene catalyzed plastic material is employed in forming the core member to impart desirable physical attributes thereto.

Abstract: A foamed polyester resin article is made by a method which includes forming a molten resin mixture containing poly (ethylene terephthalate) having an intrinsic viscosity greater than 0.7 and a moisture content of not greater than 0.03%, a melt viscosity modifier which comprises a multi-stage emulsion graft copolymer of methyl methacrylate and a lower alkyl acrylate monomer, and a heat activatable decomposition-type foaming agent. The mixture is heated in the barrel of an extruder and extruded through the die of the extruder. The method can be used to produce extruded poly (ethylene terephthalate) sheet having a foamed structure suitable for subsequent thermoforming into packaging articles and food containers such as those used in dualovenable food trays used for reheating foods in microwave or conventional ovens. The articles produced by the method have a density which may be 35-40% less than that of similar articles made from conventional non-foamed poly (ethylene terephthalate).

Abstract: An extruded polyolefin foam in thicknesses of at least about 12 mm and greater of improved compressive strength, extensional viscosity, and reduced aging time and a process for making the foam are disclosed. The foam is prepared using a propane blowing agent. The beneficial properties imparted to thicker grade and plank foams by a propane blowing agent can be achieved with up to as much as 75% by volume of either normal butane or isobutane or both in the blowing agent, depending on the polyolefin selected.

Abstract: An apparatus and process for producing polymeric foam, wherein reactive foam components and a low-boiling point frothing agent are brought together, sufficient pressure is applied to maintain the frothing agent in a liquid state and the mixture is passed through a permeable discharge head through which the mixture is discharged and wherein the pressure is reduced and froth is formed. The discharge head comprises one or more diffuser elements (80) having a structure such as to require division, divergence and convergence of flow paths in three dimensions within the axial thickness of the diffuser element, considered in the direction of flow therethrough. The diffuser element (80) is made of bonded, or sintered or sintered composite material, such as sintered wire.

Abstract: The present invention generally relates to polymeric compositions capable of providing enhanced crosslinking efficiency, to single and multilayer films having the subject composition contained within at least one layer of said film, to a method of treating said film to provide enhanced crosslink within said at least one layer of the film and to the resultant cross-linked film product as well as articles made from said cross-linked film product.

Abstract: A multilayer article such as a door trim board is fabricated by the steps of extruding melted resin layers (13m), (12m) and (11m) respectively forming a soft skin material (13), a foamed soft intermediate layer (12) and a base member (11) in the form of a multilayer resin sheet from a die-head (40) of an extruding machine, supply the extruded multilayer resin sheet to a molding machine in such a manner that the resin layer for the skin material is placed on a lower molding die of the molding machine and molding the resin layers in the form of the multilayer article. The resin layer for the skin material consists of thermoplastic elastomer, the resin layer for the intermediate layer consists of ethylenic copolymer copolymerized with ethylene and at least radical copolymerizable acid anhydride, and the resin layer for the base member consists of olefinic resin.

Abstract: A thermoplastic polyester resin is fed into a twin extruder, wherein a resin is heated for melting, thereby removing moisture in the resin by evacuating and sucking from a vent port thereof, injecting a foaming agent into the resin to which is pushed out as a foaming sheet and, after that, forming the foaming sheet which is divided into a forming body and a trimming loss, whereby the trimming loss is crushed to obtain crushed materials which are provided so as to put the materials into the twin extruder as collection materials and recycle them.

Abstract: A microporous film can be made by adding a foaming agent to the components of a film material to create bubbles in the film. The microporous film can also be made by adding filaments to the components of the film material and dissolving the filaments to create the pores. In either process, the size of the pores can be controlled to be no greater than 0.027 .mu.m.

Abstract: The invention relates to a process for the manufacture of new shaped parts, preferably made from chipboards, wherein a mass formed from at least a binder and a small-particled material brought into contact with this binder is subjected to extrusion at elevated temperature and pressure. In the process according to the invention, a mass possessing a total moisture content of 6 to 25 wt. % or adjusted to the stated moisture content and made up of at least one biopolymeric preferably starch-containing binder, which converts into a melt and/or gel at extrusion temperatures and pressures, and further made up of the small-particled material, is subjected to extrusion and immediately thereafter undergoes decompression and spontaneous expansion.

Abstract: The present invention relates to the polymer composite possesses excellent mechanical properties such as restorable ability or shock resistance, coating property, and adhesiveness. It is preferred that the disperse phase is distributed homogeneously.The polymer composite of the present invention is obtained by polymerizing a vinyl monomer selected from the group consisting of a styrenic monomer, acrylonitrile, methacrylonitrile, an ethylenically unsaturated carboxylic acid, anhydride of said carboxylic acid, and ester of said carboxylic acid in the presence of a rubber-like copolymer and a thermoplastic resin selected from the group consisting of a polyolefin, a polyamide, a polyimide, a polyarylene ether, a polyacetal and a polyester without a substantial amount of a solvent. The polymer composite is preferable that a part of vinyl monomer is grafted to the rubber-like copolymer and the polyolefin, and the thermoplastic resin forms a matrix phase.

Abstract: A slatwall section having a groove formed above and behind the upper most slat for providing additional structural integrity. The formed groove enables a slatwall to be manufactured having uniform thickness. A mating engagement between upper and lower slatwall sections provides a connection point that is concealed within a formed slat, and thereby eliminates the use of exteriorly disposed sink holes or fasteners.

Abstract: A conductive quasi-solution useful for making a homogeneously conductive single-phase polyurethane, comprising a transition metal salt, a carrier solution, and a dispersing agent, wherein said conductive quasi-solution has a transition metal salt concentration between 10 and 30% by weight, and methods of making thermoset and thermoplastic polyurethane polymers therewith.

Abstract: Method and apparatus of making a reinforced composite structure wherein a reusable mold closure is mated to a mold to close off a mold cavity in which a reinforcement is positioned. The mold closure or mold includes a plurality of collapsible resin supply ports through which resin is pumped into the mold cavity from a source of resin to infuse or impregnate the reinforcement with resin. After the resin is introduced into the mold cavity, the resin residing in the resin supply ports is selectively cured to form respective cured resin plugs on which the resin supply ports collapse to seal them in air-tight manner. The resin residing in the mold and infused in the reinforcement is not cured at that time.

Abstract: New cross-linked polymeric foam compositions, and methods for making the same, are provided. The new compositions utilize novel cross-linked polyolefin copolymers and show improvements in strength, toughness, flexibility, heat resistance and heat-sealing temperature ranges as compared to conventional low density polyethylene compositions. The new compositions also show processing improvements over linear low density polyethylene. The novel polyolefins, which are essentially linear, comprise ethylene polymerized with at least one alpha-unsaturated C3 to C20 olefinic comonomer, and optionally at least one C3 to C20 polyene, and exhibit, in an uncross-linked sense, a resin density in the range of about 0.86 g/cm3 to about 0.96 g/cm3, a melt index in the range of about 0.5 dg/min to about 100 dg/min, a molecular weight distribution in the range of from about 1.5 to about 3.5, and a composition distribution breadth index greater than about 45 percent.

Abstract: New cross-linked polymeric foam compositions, and methods for making the same, are provided. The new compositions utilize novel cross-linked polyolefin copolymers and show improvements in strength, toughness, flexibility, heat resistance and heat-sealing temperature ranges as compared to conventional low density polyethylene compositions. The new compositions also show processing improvements over linear low density polyethylene. The novel polyolefins, which are essentially linear, comprise ethylene polymerized with at least one alpha-unsaturated C3 to C20 olefinic comonomer, and optionally at least one C3 to C20 polyene, and exhibit, in an uncross-linked sense, a resin density in the range of about 0.86 g/cm.sup.3 to about 0.96 g/cm.sup.3, a melt index in the range of about 0.5 dg/min to about 100 dg/min, a molecular weight distribution in the range of from about 1.5 to about 3.5, and a composition distribution breadth index greater than about 45 percent.

Abstract: A method and device are described for the production of foams from two-component reactive mixtures using carbon dioxide as expanding agent, by mixing at least one of the reactive components with carbon dioxide under pressure. That mixture is then mixed with the other reactive component(s) to form a foamable reactive mixture, which is expanded and cured to form the final product. The foamable reactive mixture is expanded to ambient pressure through at least one fine-meshed screen (21a, 21b, 21c).

Abstract: The invention pertains to a composite panel comprising a foamed thermoplastic core layer which is joined on both sides without adhesive to thermoplastic outer layers reinforced by fiberglass mats. The composite panel is used to make molded parts for motor vehicles.

Abstract: The invention resides in mixing low-pressure gas in a viscous material. The flow of the gas can be easily controlled so that the dispersion of the mixing ratio of the viscous material to the gas may be confined within a small tolerance and fine bubbles may be uniformly distributed in the interior of the viscous material.The gas is mixed in the viscous material by means of a first pump 42, from which a mixture of the gas and the viscous material is delivered. Pressure is applied to the mixture by means of a second pump 51. The gas is distributed in the interior of the viscous material by allowing the mixture under pressure to pass through a conduit assembly 61. The viscous material is foamed when the mixture is discharged from a nozzle 73 through a discharge pipe 71.

Abstract: A method for making continuous fiber-reinforced plastic composites is disclosed. It involves the steps of (a) using an extruder to continuously extrude a first plastic resin through an extruder die to form a first plastic resin layer; (b) continuously pulling a plurality of prepreg strips along with the first plastic resin layer; and (c) combining the plurality of prepreg strips with the first plastic resin layer to form a sandwiched composite containing at least two prepreg layers separated by the first plastic resin. The prepreg strip contains reinforcing fibers impregnated with a second plastic resin. The fiber-reinforced and sandwich-structured plastic composites exhibit greatly improved flexural strength and flexural modulus approaching those of real wood, and can be drilled, nailed, chiseled, saw, etc, similar to natural wood.

Abstract: Open cell foamed articles including silane-grafted single-site inititiated polyolefin resins are described. The single-site initiated olefin polymer resin can be a polyethylene, a copolymer of ethylene, a C3-C20 alpha-olefin, or a copolymer of ethylene, a C3-C20 alpha-olefin and a C4-C20 diene. The open cell foamed articles have good cushioning properties and can be non-allergenic.

Abstract: The present invention pertains to a polymeric sealing/spring strip and method of producing same. The polymeric sealing/spring strip of the present invention has several various embodiments which are based upon the incorporation of silicone rubber. Some of the embodiments are based on the formation of a resilient silicone rubber surface to provide a sealing/spring contact with an opposing surface period. Other embodiments of the invention incorporate the silicone rubber in such way as to utilize its resilient properties to produce a sealing/spring strip which has improved mechanical resilience properties. The method of the present invention allows the production of a sealing/spring strip in accordance with the present invention by using extrusion techniques.

Abstract: A sheet of expanded plastics material with absorbent properties towards aqueous liquids has a structure with intercommunicating cells and comprises at least one surfactant and at least one lubricating agent. The invention also relates to a tray (1) of plastics material for foods which may release liquids, comprising a base (2) and side walls (3), wherein the base (2) has holes (4) of 0.1-1.5 mm diameter in the surface (4) which is intended to contact the food, and is produced from a sheet as described above. Methods of producing the sheet and the tray are also described.

Abstract: A composition containing thermoplastic elastomer and elastic fine particles is extruded into a sheet-like shape from an extruder. Then, by expanding this sheet-like shape member, a covering sheet having minute unevenness attributable to the elastic fine particles formed on the surface is produced. The covering sheet may have an adhesive layer, a substrate layer, a foamed resin layer, etc., on the opposite side to the surface having a matt feeling. Such covering sheet can be produced with good productivity without creating environmental problems such as a problem related to solvent, etc. By molding using the covering sheet, a molding having matt feeling can be obtained.

Abstract: A co-extrusion method for making a blown-film textured liner having a textured surface to provide improved soil gripping properties and smooth untextured edges for improving the integrity of the joint between adjacent liner sheets.

Abstract: An amphiphilic block copolymer including a hydrophilic internal segment and polymeric articles made therefrom.

Abstract: In a process for extruding a low density foam, a foamable thermoplastic elastomer such as a thermoplastic rubber is selected. The selected thermoplastic elastomer is then fed into a heated extruder barrel where it is compressed and melted by the action of a screw. A blowing agent consisting of water is introduced into the melted thermoplastic elastomer. The melted thermoplastic elastomer and the water are thoroughly mixed and then cooled to a uniform, predetermined temperature. The mixture is then forced through a die to form an extruded foam profile.

Abstract: A method and device are described for the production of foams from two-component reactive mixtures using carbon dioxide as expanding agent, by mixing at least one of the reactive components with carbon dioxide under pressure. That mixture is then mixed with the other reactive component(s) to form a foamable reactive mixture, which is expanded and cured to form the final product. The foamable reactive mixture is expanded to ambient pressure through at least one fine-meshed screen (21a, 21b, 21c).

Abstract: A method of producing a microporous polyolefin membrane having a relatively large pore size and a high permeability, the membrane being suitable for use in water treatment, microfiltration, etc. The method comprises dissolving a polyolefin composition in a solvent to prepare a solution, extruding the solution through a die lip into a form of gel-like sheet, rapidly cooling the gel-like sheet, removing a residual solvent in the cooled sheet by a washing solvent, and drying the resultant sheet to remove the washing solvent. The polyolefin composition is a mixture of (A) an ultra high molecular weight polyolefin having a weight average molecular weight of 5.times.10.sup.5 or more and (B) a polyolefin having a weight average molecular weight less than 5.times.10.sup.5, and a weight ratio of (B)/(A) is 0.2 to 20.

Abstract: The present invention is a method of producing an extruded composite comprising the general steps of: (a) extruding a longitudinally oriented composite precursor coextrusion comprising: (1) at least one thermoplastic polymeric material and (2) a core mixture of at least one thermosetting resin and at least one filler material; whereby the thermoplastic polymeric material(s) is extruded so as to substantially enclose a space, and whereby the core mixture is pumped into the space; and (b) maintaining the composite precursor under conditions whereby the at least one thermoplastic polymeric material becomes cooled and the at least one thermosetting resin becomes cured so as to form the extruded composite of the present invention.

Abstract: Porous pipe formed by extruding a mixture of particles of vulcanized rubber dispersed in a binder resin such as linear low density polyethylene preferably having a Melt Index below 1.0 and a broad distribution of molecular weights, through a pipe die to form porous pipe and then cooling the pipe in a cooling trough. The pipe is stabilized to reduce degradation by ultraviolet light by dispersing in the binder resin an effective amount of an ultraviolet stabilizer such as 0.1 to 10% by weight of carbon black.

Abstract: A polymer bonded sheet product suitable for use as an electrode in a non-aqueous battery system. A porous electrode sheet is impregnated with a solid polymer electrolyte, so as to diffuse into the pores of the electrode. The composite is allowed to cool, and the electrolyte is entrapped in the porous electrode. The sheet products composed have the solid polymer electrolyte composition diffused into the active electrode material by melt-application of the solid polymer electrolyte composition into the porous electrode material sheet. The solid polymer electrolyte is maintained at a temperature that allows for rapid diffusion into the pores of the electrode. The composite electrolyte-electrode sheets are formed on current collectors and can be coated with solid polymer electrolyte prior to battery assembly. The interface between the solid polymer electrolyte composite electrodes and the solid polymer electrolyte coating has low resistance.

Abstract: A composite camel structure includes an elongate hollow, rigid cylindrical core, opposite ends of the core having respective caps sealingly connected thereto, a buoyant material of cured urethane foam substantially filling the core and being sealingly enclosed therein. A cushion is thermally bonded to and sealingly surrounds the core, the cushion having a substantially unbroken outside surface, being formed of a polymeric component consisting of polyethylene being at least 80 percent low-density polyethylene, and a process additive component including an effective amount of an ultraviolet inhibitor. A pair of parallel-spaced, transversely oriented guides extend between opposite sides of the cushion in axially spaced relation to the core, each guide defining a guide opening through the cushion for receiving hawser chains whereby the camel structure rides up and down with the tide.

Abstract: A lactide polymer composition combining compositional and purity limitations and catalyst optimization or addition of stabilizing agents resulting in a melt-stable polymer is disclosed. The melt-stable lactide polymer comprises a plurality of polylactide polymer chains, residual lactide in concentration of less than 2 percent and water in concentration of less than 1000 parts-per-million. A stabilizing agent in an amount sufficient to reduce depolymerization of the lactide polymer during melt-processing or alternatively, control of catalyst level at a molar ratio of monomer to catalyst greater than 3000:1 is also included in the melt-stable composition. A process for manufacture of a melt-stable lactide polymer composition includes polymerizing a lactide mixture and adding stabilizing agents sufficient to reduce depolymerization of the polylactide during melt-processing, followed by devolatilizing the polylactide to remove monomer and water.

Abstract: A method of forming a two-layer plastic pipe (4;8) to be laid in the ground for conducting material therethrough forms a core pipe (2) consisting essentially of a first plastic material and forms a detachable outer hose (3;7) of a second plastic material around said core pipe (2) by a suitable coating method, including in said second plastic material an amount of additives effective to protect said core pipe with said outer hose from stresses and loads of laying said core pipe and outer hose and usage thereof in ground.

Abstract: A conductive roll including a conductive shaft, a conductive rubber foam layer formed on an outer circumferential surface of the conductive shaft, and a semi-conductive solid rubber layer formed on an outer circumferential surface of the conductive rubber foam layer. The conductive roll is produced by forming a cylindrical laminar body which gives the conductive rubber foam layer and semi-conductive solid rubber layer, and simultaneously vulcanizing and foaming the laminar body in a mold in which the conductive shaft is placed in position.

Abstract: A method of producing an extruded plastics foam of enhanced physical strength includes intimately mixing a blowing agent incorporation CO.sub.2, the major portion of which is a natural gas, in a plastics resin melt to form a homogenous resin mix, and extruding the resin mix through an exit die into a region of lower pressure. At the point of extrusion out of the exit die, the temperature of the resin mix is adjusted so that it is below the critical temperature.