Abstract: A process for producing polypropylene having increased melt strength, the process comprising (i) homopolymerising polypropylene or copolymerising propylene with one or more comonomers selected from ethylene and C4 to C101-olefins to produce a polypropylene homopolymer or copolymer respectively having a double bond concentration of at least 0.1 per 10,000 carbon atoms, (11) irradiating the polypropylene with an electron beam having an energy of at least 5 MeV and at radiation dose of at least 5 kGray, and (iii) melting and mechanically processing the melt of polypropylene to form long chain branches on the polypropylene molecules.

Abstract: A photosensitive composition for forming a dielectric of the present invention comprising inorganic particles, an alkali developable resin and additives, wherein the additives comprise a compound having a quinonediazido group (C1), a compound containing at least two alkyletherified amino groups in the molecule (C2) and a thermal acid generator (C3), or wherein the inorganic particles comprise inorganic superfine particles (A-I) having a mean particle diameter of less than 0.05 ?m and inorganic fine particles (A-II) having a mean particle diameter of not less than 0.05 ?m. The composition can be calcined at low temperatures to form a dielectric layer with high dimensional precision, said layer having a high dielectric constant and a low dielectric loss. Also provided are a dielectric and an electronic part prepared from the composition.

Abstract: Provided are radiation-cured, laminated materials, radiation-curable adhesive compositions suitable for use in forming the laminated materials, and methods of making laminated materials.

Abstract: A resin composition of the present invention is obtainable by adding a photo-polymerization initiator (d) to a resin solution (a) containing a modified product of a thermoplastic resin (A). The modified product is prepared by conducting radical polymerization of the thermoplastic resin (A) with a (co)polymer (B) of a copolymerizable monomer (C) comprising a monomer having an ?,?-mono-ethynically unsaturated group, or the monomer and other copolymerizable monomers in a weight ratio (A)1(B) of 1/9 to 9/1, in an organic solvent, or by conducting polymerization of a copolymerizable monomer (C) comprising a monomer having an ?,?-mono-ethylenically unsaturated group, or the monomer and other copolymerizable monomers in a weight ratio (A)/(C) of 1/9 to 9/1, in an organic solvent in the presence of the thermoplastic resin (A), and then conducting radical polymerization thereof. A paint including the resin composition and a process for forming a coating film are also disclosed.

Abstract: A prosthetic medical device exhibiting improved wear resistance is fabricated by irradiating at least one polyolefinic material in the presence of an inert atmosphere to yield a cross-linked irradiated polyolefinic material; blending at least one non-irradiated polyolefinic material with the at least one irradiated polyolefinic material, and forming the prosthetic medical device from the blended material. Selectively cross-linked polymeric compositions may be created by blending a specific amount of cross-linked resins with a specific amount of uncross-linked resins then cured into a polymeric matrix whereby the desired degree or percentage of overall cross-linking is obtained. The polymeric material may then be formed directly into a finished article by injection molding the polymeric material.

Abstract: This invention is a process for making UV curable adhesives, sealants, coatings, ink, flexible printing plates, laminating adhesives, fibers, gaskets, and related compositions, films, and thin parts, wherein an epoxidized monohydroxylated polydiene polymer comprised of at least two different diene monomers wherein at least one is a diene monomer which yields unsaturation suitable for epoxidation is used as the binder for the composition. The preferred epoxidized monohydroxylated polymers are block copolymers of isoprene and butadiene wherein a hydroxyl group is attached at one end of the polymer molecule. These polymers may be hydrogenated or unhydrogenated. The process involves mixing the above polymer or the polymer with one or more other formulating ingredients together with and insoluble photoinitiator which is preferably selected from the group consisting of triaryl sulfonium salts.

Abstract: A latent material having various controlled shrinkage tensions and patterns and a method of making the same. The materials include polymer materials that are capable of absorbing microwave energy. Different degrees of shrinkage of the material may be controlled to create different tensions in the material. Additionally, various stereo and three-dimensional patterns may be generated on the material. These materials may be used in the formation of personal care articles. The materials are made by incorporating a polymer material onto the film, wherein the polymer material is capable of turning microwave energy into heat. Upon exposure to microwave radiation, the heat will cause the latent material to shrink. The use of different types and amounts of polymer materials will result in a latent material having different tensions and patterns.

Abstract: Certain essentially phenol antioxidant-free stabilizer systems that comprise either a binary hindered amine/hydroxylamine or nitrone or amine oxide or benzofuranone system or a ternary hindered amine/hydroxylamine or nitrone or amine oxide or benzofuranone/organic phosphite or phosphonite system are especially effective towards protecting polyolefins against the deleterious effects of gamma irradiation. Polyolefin articles such as medical packaging, hospital garments, draperies, woven and non-woven fiber products, surgery utensils, blow-molded I.V. bottles, hypodermic syringes, needle shields, laboratory ware such as trays, funnels, Petri dishes and filters, and hygiene related articles may be sterilized with gamma irradiation and are stabilized according to the present invention.

Abstract: Irradiated, oxidized olefin polymer coupling agents for use in the manufacture of non-halogenated flame retardant-containing and filler-containing olefin polymer compositions and coupling agent-containing olefin polymer concentrates.

Abstract: The invention includes an optical fiber coating that exhibits the characteristics of a pressure sensitive adhesive. A viscoelastic window for the coating will include at least one set of coordinates that is within Quadrants 2, 3, or 4 or the Transition Flow Region of the Chang viscoelastic of the rheological master curves or will not include at least one set of coordinates that is not within Quadrant 1 of the Chang viscoelastic of the rheological master curves.

Abstract: The invention provides a process for quenching free radicals present in irradiated ultrahigh molecular weight polyethylene comprising the steps of (a) providing a mass of irradiated ultrahigh molecular weight polyethylene, wherein the mass comprises free radicals, (b) immersing at least a portion of the mass of irradiated ultrahigh molecular weight polyethylene in a non-polar solvent having a temperature for a time and under conditions sufficient to quench a substantial portion of the free radicals contained therein, wherein the temperature of the non-polar solvent is maintained below the melting point of the ultrahigh molecular weight polyethylene, (c) removing the mass of irradiated ultrahigh molecular weight polyethylene from the non-polar solvent, and (d) removing any non-polar solvent from the mass of irradiated ultrahigh molecular weight polyethylene.

Abstract: A method of modifying a polymeric material which comprises the steps of activation-treatment and a hydrophilic polymer-treatment, or comprises the steps of activation-treatment, a hydrophilic polymer-treatment, and monomer grafting in this order, or comprises the step of a solvent-treatment followed by these steps. Thus, the polymeric material, e.g., polyolefin, is improved in hydrophilicity, adhesion, etc. without lowering the practical strength thereof. The polymeric material thus improved in adhesion and other properties can be used in many applications where water absorption and adhesion are required, such as an absorption material, e.g., a wiping/cleansing material, a water retention material, a material for microorganism culture media, a separator for batteries (or cells), a synthetic paper, a filter medium, a textile product for clothing, a medical/sanitary/cosmetic supply, and reinforcing fibers for composite materials.

Abstract: The object of the invention is to provide a rubber composition or its crosslinked product used for a rubber stopper for a medicament or a rubber article for a medical treatment, suitable for radiation treatments to be carried out for the purpose of sterilizing. Accordingly, the present invention provides a rubber composition or its crosslinked product used for a rubber stopper for a medicament or a rubber article for a medical treatment, comprising an isobutylene copolymer, as a predominant component, with a density of at most 0.95, capable of being readily subjected to a radiation treatment.

Abstract: A process for manufacture of a photochromic polymeric article comprising: providing a fluid polymerisable composition; subjecting the fluid polymerisable composition to a first curing step to provide a solid article of intermediate hardness; contacting the solid article of intermediate hardness with a photochromic substance; and subjecting the solid article of intermediate hardness to a further curing step to increase the hardness and provide a polymeric article imbibed with the photochromic substance.

Abstract: The present invention relates to a method for making a heat-resistant elastic article and a heat-resistant elastic article. The invention especially relates to a method of making elastic fibers and polymeric elastic fibers wherein the elastic fibers are capable of withstanding dyeing and heat-setting processes that typically are conducted at elevated temperatures (such as 110-230° C. and especially at greater than or equal to 130° C. for minutes). The inventive method comprises radiation crosslinking an article (or plurality of articles) under an inert or oxygen limited atmosphere (for example, in N2, argon, helium, carbon dioxide, xenon and/or a vacuum) wherein the article (or articles) comprises at least one amine stabilizer and preferably another optional stabilizer additive. More preferably, the radiation crosslinking is performed at a low temperature (−50 to 40° C.).

Abstract: The present invention discloses methods for enhancing the wear-resistance of polymers, the resulting polymers, and in vivo implants made from such polymers. One aspect of this invention presents a method whereby a polymer is irradiated, preferably with gamma radiation, then thermally treated, such as by remelting of annealing. The resulting polymeric composition preferably has its most oxidized surface layer removed. Another aspect of the invention presents a general method for optimizing the wear resistance and desirable physical and/or chemical properties of a polymer by crosslinking and thermally treating it. The resulting polymeric compositions is wear-resistant and may be fabricated into an in vivo implant.

Abstract: The invention relates to a method in connection with processing polymer or elastomer material, wherein additive is added to the polymer or elastomer material, and the additive is subjected to the desired chemical reaction. To minimize energy consumption, infrared radiation is led to the polymer or elastomer material, the wavelength of the radiation being so chosen that the radiation penetrates optimally the polymer or elastomer material, but absorbs in the additive, producing the desired reaction in the additive.

Abstract: The present invention relates to a tough, wear resistant Ultra High Molecular Weight Polyethylene (UHMWPE) prepared by the cross linking of a UHMWPE shaped article with irradiation doses higher than 4 Mrads, preferably higher than 5 Mrads, and most preferably less than 10 Mrads. The invention particularly provides total joint replacement devices and methods of making them for the hip, knee, elbow and shoulder.

Abstract: A process for producing scratch-resistant coatings, encompassing the following steps: applying at least one UV-curable coating composition to at least one surface of an article to be coated, said coating composition comprising at least one polymer and/or oligomer P1 containing on average at least one ethylenically unsaturated double bond per molecule, and curing the coating composition by exposure to UV radiation, which comprises conducting the curing of the coating composition under an oxygen-containing protective gas which has an oxygen partial pressure in the range from 0.2 to 18 kPa.

Abstract: The invention is directed to methods for fabricating devices from polymer precursors, along with devices so fabricated. The methods of the invention include the steps of plasma treating a polymer based resin, paste, preform billet, or extrudate, and employing the treated polymer in the fabricated device. According to one embodiment, the fabricated device can include implantable prosthetics such as heart valves, sutures, vascular access devices, vascular grafts, shunts, catheters, single layered membranes, double layered membranes, and the like. Devices fabricated according to one embodiment of the invention include regions having selected porosity, permeability and/or chemistry characteristics.

Abstract: A process for producing a propylene copolymer having increased melt strength, the process comprising irradiating a copolymer of propylene and ethylene which has been polymerised using a Ziegler-Natta catalyst with an electron beam having an energy of at least 5 MeV and a radiation dose of at least 10 kGray and melting and mechanically processing the melt of the irradiated ethylene propylene copolymer to form long chain branches on the ethylene propylene copolymer molecules.

Abstract: Disclosed herein are radiation-curable polymers, a method of preparing radiation-curable polymers and compositions containing radiation-curable polymers. Radiation-curable polymers and compositions containing radiation-curable polymers are useful as coatings and adhesives.

Abstract: Membranes made from amphiphilic copolymers are disclosed. The amphiphilic copolymers can be ABA copolymers, where one of A and B is hydrophilic and the other is hydrophobic. The copolymers may be crosslinked to form more stable structures. Crosslinking can be accomplished using a variety of methods, including end to end polymerization of copolymers having terminal unsaturated groups. Molecules such as membrane proteins can be incorporated into the membrane to allow the transport there through of selected components.

Abstract: The present invention relates to a method for reforming the surface of polymer, especially to a method for providing hydrophilicity or increasing hydrophobicity by reforming the surface of polymer or polymer membrane. The present invention is a method for reforming the surface of polymer membrane by irradiating it with energized ionic particles under the vacuum condition. The method including the steps of: a) manufacturing polymer membrane, including a surface activated, by inserting polymer membrane into a vacuum chamber, and by irradiating energized ionic particles on the surface of polymer membrane with an ion beam under a high vacuum; and b) manufacturing polymer membrane treated with a reactive gas on the surface of membrane, including the activated surface of step a), by infusing the reactive gas into a vacuum chamber after energized ionic particles of step a) have been irradiated.

Abstract: The objective of the present invention is to provide a production method by which a polymer of a functional group-terminated vinyl monomer can be easily and practically produced. Further, it is another object of the present invention to provide a functional group-terminated vinyl polymer which is useful as a material for the production of various functional products. The first aspect of the present invention is concerned with a production method of a functional group-terminated vinyl polymer comprising a step of synthesizing a halogen atom-terminated vinyl polymer by the radical polymerization reaction of a vinyl monomer in the presence of a halogen compound and a step of introducing a functional group to a terminus by substituting a functional group-containing group for the terminal halogen atom of said vinyl polymer.

Abstract: A method for producing a battery separator is disclosed. The method comprises applying a coating of an ethylenically unsaturated monomer to the fibers of a non-woven sheet and polymerizing the monomer in situ on the fiber surfaces. The non-woven sheet is from 50 to 3000 microns thick, and is composed of polyolefin fibers having an average fiber diameter from 0.5 to 5 microns and a surface area from 0.2 to 30 square meters per gram.

Abstract: Photoinitiators of formula (Ia) or (Ib) having chain transfer groups, wherein n is 1 or 2; PI is for example a group of formula (IIa); PI′ inter alia is a group of formula (IIIa); Ar is for example phenyl; Ar2 is inter alia phenylene; R1 and R2 are for example C1-C8alkyl, or R1 and R2 together C2-C9alkylene; M1 inter alia is —NR3R4 or —OH; M1′ is for example a group (c); R3′ is a direct bond, C1-C12alkylene, or phenylene; R3 is for example hydrogen, or C1-C12alkyl; R4 is e.g. C1-C12alkyl; A1 and A2 are for example a direct bond; CT is a chain transfer group; are useful for the preparation of macrophotoinitiators which can be employed for preparing block copolymers.

Abstract: The present invention relates to elastic articles comprising a crosslinked or crosslinkable ethylene polymer and a method for making the same. In particular, the invention relates to a shaped article (e.g. film or fiber) characterized by improved elasticity at elevated temperatures and comprising a substantially cured, irradiated, or crosslinked (or curable, irradiated or crosslinkable) homogeneously branched ethylene polymer. The improved elastic article of the present invention is particularly suitable for use in applications where good elasticity must be maintained at elevated temperatures such as, for example, personal hygiene items and disposable infection-control garments at body temperatures of about 100° F. (38° C.).

Abstract: This invention relates to polymeric compositions that are processible and may be photochemically cured to produce crosslinked compositions useful in coating, sealants and adhesive applications. The crosslinkable composition comprises a first component having a plurality of pendent, free-radically polymerizable functional groups; a polymeric photoinitiator, and a residual content of less than 2%. The composition is melt processable at temperatures of less than or equal to 100° C.

Abstract: Certain essentially phenol antioxidant-free stabilizer systems that comprise either a binary hindered amine/hydroxylamine or nitrone or amine oxide or benzofuranone system or a ternary hindered amine/hydroxylamine or nitrone or amine oxide or benzofuranone/organic phosphite or phosphonite system are especially effective towards protecting polyolefins against the deleterious effects of gamma irradiation. Polyolefin articles such as medical packaging, hospital garments, draperies, woven and non-woven fiber products, surgery utensils, blow-molded I.V. bottles, hypodermic syringes, needle shields, laboratory ware such as trays, funnels, Petri dishes and filters, and hygiene related articles may be sterilized with gamma irradiation and are stabilized according to the present invention.

Abstract: Dental material containing a polymerizable component and a component applied superficially to the polymerizable component, which can be removed after the curing of the polymerizable material with accompanying formation of a rough surface.

Abstract: A process for producing polypropylene having increased melt strength, the process comprising irradiating polypropylene with an electron beam having an energy of at least 5 MeV and with a radiation dose of from 5 to 100 kGray in the presence of a grafting agent for forming long chain branches on the polypropylene molecules.

Abstract: The present invention relates to a sulfonated polymer membrane and to a process for the preparation thereof. According to the process, a polymer film is irradiated, and the irradiated polymer film is sulfonated in order to link sulfonic acid groups thereto. According to the invention, the sulfonation is continued until the total concentration of sulfonic acid groups in the membrane is 0.4-3.0 meq/g and they are homogeneously distributed in the membrane material in such a manner that their concentration in the middle of the membrane is at minimum 0.2 meq/g. With the help of the invention, it is possible by a rapid and simple process to prepare membranes the chemical and mechanical properties of which can be regulated by means of the selection of the initial film, by irradiation and by the sulfonation process.

Abstract: The present invention relates to shape deformable materials, which are capable of (1) being deformed, (2) storing an amount of shape deformation, and (3) recovering at least a portion of the shape deformation when exposed to a humid environment. The shape deformable materials can advantageously be in the form of films, fibers, filaments, strands, nonwovens, and pre-molded elements. The shape deformable materials of the present invention may be used to form products, which are both disposable and reusable. More specifically, the shape deformable materials of the present invention may be used to produce products such as disposable diapers, training pants, incontinence products, and feminine care products.

Abstract: The invention is directed to methods for fabricating devices from polymer precursors, along with devices so fabricated. The methods of the invention include the steps of plasma treating a polymer based resin, paste, preform billet, or extrudate, and employing the treated polymer in the fabricated device. According to one embodiment, the fabricated device can include implantable prosthetics such as heart valves, sutures, vascular access devices, vascular grafts, shunts, catheters, single layered membranes, double layered membranes, and the like. Devices fabricated according to one embodiment of the invention include regions having selected porosity, permeability and/or chemistry characteristics.

Abstract: The invention is directed to methods for fabricating devices from polymer precursors, along with devices so fabricated. The methods of the invention include the steps of plasma treating a polymer based resin, paste, preform billet, or extrudate, and employing the treated polymer in the fabricated device. According to one embodiment, the fabricated device can include implantable prosthetics such as heart valves, sutures, vascular access devices, vascular grafts, shunts, catheters, single layered membranes, double layered membranes, and the like. Devices fabricated according to one embodiment of the invention include regions having selected porosity, permeability and/or chemistry characteristics.

Abstract: Graft copolymers are prepared, in a non-oxidizing atmosphere, by (1) irradiating a particulate olefin polymer material with high energy ionizing radiation, (2) treating the irradiated olefin polymer material with at least one grafting monomer that is capable of forming side chains on the olefin polymer material, in the presence of at least one additive to control the molecular weight of the side chains of the polymerized grafting monomer selected from (a) at least one hydroxylamine derivative polymerization inhibitor, and (b) at least one thio-, nitro-, or halogen-substituted aliphatic or aromatic compound or an aliphatic or aromatic phosphine derivative, and (3) deactivating the residual free radicals in the resulting grafted olefin polymer material and removing any unreacted vinyl monomer from the material. Graft copolymers with low molecular weight side chains are produced that are easier to process and have improved internal and surface morphology.

Abstract: In one aspect the invention provides an energy efficient polymerization method comprising irradiating a polymerizable composition and a photoinitiator with a source of essentially monochromatic radiation where the photoinitiator and the wavelength of the radiation source are selected such that the extinction coefficient of the photoinitiator at the peak wavelength of the source is greater than about 1000 M−1 cm−1 and such that the photoinitiator absorbs at least two percent of the actinic radiation incident on the coating. In another aspect the invention provides energy efficient methods of polymerizing polymerizable compositions and crosslinking crosslinkable compositions by irradiating the respective compositions with a low power source of essentially monochromatic radiation. The low power energy sources have an input power of less than about 10 W/cm.

Abstract: A monolayer polyolefin-based printable article includes 0.1 to 5% by weight of at least one polyaminoalkylene, and is characterized in that it has been treated by means of an oxidative surface treatment, such as a corona treatment. A process for the manufacture of a polyolefin-based printable article, according to which at least one surface region of the article, including at least one polyolefin and from 0.1 to 5% by weight of at least one polyaminoalkylene, involves subjecting the region to an oxidative surface treatment. A printing process, according to which a polyolefin-based article, including from 0.1 to 5% by weight of at least one polyaminoalkylene and treated by means of an oxidative surface treatment, utilizes an electrophotography technique to print on the article.

Abstract: An Offset Lithographic Printing Process employing low VOC lithographic printing ink formulations containing monomeric diluents, curable by cationic polymerization in the presence of fountain solution and resin rheology modifiers compatible with cationic catalysts.

Abstract: This invention relates to polymeric compositions that are processible and may be photochemically cured to produce crosslinked compositions useful in coating, sealants and adhesive applications. The crosslinkable composition comprises a first component having a plurality of pendent, free-radically polymerizable functional groups; a polymeric photoinitiator, and a residual content of less than 2%. The composition is melt processable at temperatures of less than or equal to 100° C.

Abstract: Graft copolymers with low molecular weight side chains are prepared by (1) irradiating a propylene polymer material in the absence of oxygen, (2) adding a controlled amount of oxygen to the irradiated polymer material so that the polymer is exposed to an amount of oxygen greater than 0.004% but less than 15% by volume at a temperature of 40° C. to 140° C., to produce an oxidized propylene polymer material containing greater than 1 mmol total peroxide per kilogram of propylene polymer material, (3) optionally, heating the oxidized propylene polymer material in a non-oxidizing atmosphere to a temperature of at least 80° C.

Abstract: The present invention relates to a method for making a heat-resistant elastic article and a heat-resistant elastic article. The invention especially relates to a method of making elastic fibers and polymeric elastic fibers wherein the elastic fibers are capable of withstanding dyeing and heat-setting processes that typically are conducted at elevated temperatures (such as 110-230° C. and especially at greater than or equal to 130° C. for minutes). The inventive method comprises radiation crosslinking an article (or plurality of articles) under an inert or oxygen limited atmosphere (for example, in N2, argon, helium, carbon dioxide, xenon and/or a vacuum) wherein the article (or articles) comprises at least one amine stabilizer and preferably another optional stabilizer additive. More preferably, the radiation crosslinking is performed at a low temperature (−50 to 40° C.).

Abstract: The present invention provides a fully vulcanized powdery rubber having a particle size of from 20 to 2000 nm, its preparation and use. The vulcanized powdery rubber is obtained by irradiating a rubber latex having a particle size of from 20 to 2000 nm with a high-energy irradiation. The vulcanized powdery rubber is very easily to be dispersed into various plastics, and thus can be mixed with various plastics to prepare toughened plastics and fully valcanized thermoplastic elastomers.

Abstract: A method of preparing a conjugated polymer which includes: determining a first intermolecular repeat distance and a first tilt angle relative to the translation axis for a guest molecule having a first atom and a second atom; selecting a host molecule having a second intermolecular repeat distance and a second tilt angle relative to the translation axis; synthesizing the host molecule and the guest molecule to form a co-crystal, wherein the first and the second repeat distances and the first and the second tilt angles are about equal so that when said host molecule and said guest molecule are synthesized the first atom and the second atom of adjacent guest molecules are in near van der Waals contact; and polymerizing the co-crystals to form the conjugated polymer. In a preferred embodiment, the guest molecule is a polytriacetylene and the host molecule has an intermolecular repeat distance of from about 6.0 Å to about 8.

Abstract: A process and resulting product is provided in which a vulcanized solid particulate, such as vulcanized crumb rubber, has select chemical bonds altered by biotreatment with thermophillic microorganisms selected from natural isolates from hot sulfur springs. Following the biotreatment, microwave radiation is used to further treat the surface and to treat the bulk interior of the crumb rubber. The resulting combined treatments render the treated crumb rubber more suitable for use in new rubber formulations. As a result, larger loading levels and sizes of the treated crumb rubber can be used in new rubber mixtures and good properties obtained from the new recycled products.

Abstract: This invention relates to rubber polymers based on polymerizable monomers and having an elevated gel content together with an elevated degree of swelling, to the production of the stated rubber polymers and to the use thereof for the production of moldings of all kinds.

Abstract: A process for reducing or quenching free radical concentration in irradiated ultra high molecular weight polyethylene (UHMWPE) using electromagnetic or mechanical wave energy.

Abstract: A medical implant made of polymeric material having an increased oxidation resistance is formed by a method including the steps of placing a resin powder in a sealed container. A substantial portion of the oxygen is removed from the sealed container by either a vacuum, an oxygen absorbent or by flushing with inert gas. The container is then repressurized with a gas such as nitrogen, argon, helium or neon so that long term storage may be possible. On use, the resin is transferred to a forming device which both melts and forms the resin in an oxygen reduced atmosphere to produce a polymeric raw material such as a rod or bar stock. The medical implant is then formed from this raw material annealed and sealed in an airtight package in an oxygen reduced atmosphere. The implant is then radiation sterilized and thereafter annealed in the package for a predetermined time and temperature sufficient to form cross-links between any free radicals in neighboring polymeric chains.

Abstract: The invention relates to a process for producing foamed polyolefin-based plastics blocks by first crosslinking a matrix comprising a) from 51 to 97% by weight of one or more polyolefins, selected from the group consisting of polyethylene and ethylene copolymer, b) from 3 to 20% by weight of a foaming agent, using &bgr;-radiation of energy >6 MeV. The thickness of the matrix is from 25 to 45 mm. The radiation dose is from 20 to 150 kJ/kg. During the irradiation, atmospheric oxygen is at least substantially prevented from reaching the surface of the matrix. After crosslinking, the crosslinked matrix is foamed by heating to a temperature >160° C. and decomposing the blowing agent.