Radiation-crosslinked polyolefin compositions

A process for producing a radiation-crosslinked article comprised of a polymer composition, wherein the process comprises the following steps:

• (a) forming a blend comprising a polyethylene and a polypropylene, wherein the polyethylene is selected from the group consisting of high density polyethylene, medium density polyethylene and linear medium density polyethylene and the polypropylene is selected from the group consisting of polypropylene homopolymer and polypropylene copolymers, wherein the polyethylene comprises at least 60 percent by weight of the blend;
• (b) blending the polyethylene and the polypropylene with an ethylene-propylene elastomer in an amount of up to about 40 percent by weight of the composition;
• (c) melt processing the polyethylene, the polypropylene and the ethylene-propylene elastomer to produce a melt-processed article having a first set of dimensions;
• and
• (d) crosslinking the melt-processed article by exposure to radiation to thereby produce said radiation-crosslinked article, wherein a dosage of said radiation is sufficient to impart thermoset characteristics to the article such that, when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid.

A radiation-crosslinked article comprised of a polymer composition, the polymer composition comprising:

• (a) at least 60 percent by weight of a polyethylene selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE);
• (b) from about 5 percent by weight to less than 40 percent by weight of a polypropylene selected from the group consisting of polypropylene homopolymer and polypropylene copolymers;
• (c) from 0 to 20 percent by weight of an ethylene-propylene elastomer;
• wherein the article is crosslinked by exposure to radiation and possesses a sufficient degree of crosslinking such that when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid;
• and
• (d) a compatibilizer comprising one or more members of the group consisting of:
• high density polyethylene (HDPE);
• medium density polyethylene (MDPE);
• linear medium density polyethylene (LMDPE);
• low density polyethylene (LDPE);
• polypropylene homopolymer and polypropylene copolymers optionally modified with reactive functional groups selected from the group consisting of silanes, acrylic acids, methacrylic acids, acrylates, methacrylates, glycidyl methacrylates and anhydrides;
• ethylene-propylene copolymers;
• ethylene-propylene diene elastomers;
• crystalline propylene-ethylene elastomers;
• thermoplastic polyolefin elastomers;
• metallocene polyolefins;
• cyclic olefin copolymers;
• polyoctenamers;
• copolymers of ethylene with vinyl acetate, vinyl alcohol, and/or alkyl acrylates;
• polybutenes;
• hydrogenated and non-hydrogenated polybutadienes;
• butyl rubber;
• polyolefins modified with reactive functional groups selected from the group consisting of silanes, alcohols, amines, acrylic acids, methacrylic acids, acrylates, methacrylates, glycidyl methacrylates, and anhydrides;
• polyolefin ionomers;
• polyolefin nanocomposites;
• and block copolymers selected from the group consisting of styrene-butadiene, styrene-butadiene-styrene, styrene-ethylene/propylene and styrene-ethylene/butylene-styrene;
• wherein the compatibilizer comprises from about 5 to about 10 percent of the composition.

A process for producing a radiation-crosslinked article, comprising:

• (a) forming a blend comprising at least 60 percent by weight of a polyethylene selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE), from about 5 percent by weight to less than 40 percent by weight of a polypropylene selected from the group consisting of polypropylene homopolymer and polypropylene copolymers, and from 0 to 20 percent by weight of an ethylene-propylene elastomer;
• (b) melt processing the blend to produce a melt-processed article having a first set of dimensions;
• and
• (c) crosslinking the melt-processed article by exposure to radiation to thereby produce said radiation-crosslinked article, wherein a dosage of said radiation is sufficient to impart thermoset characteristics to the article, such that, when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid.

A process for producing a radiation-crosslinked article, comprising:

• (a) forming a blend comprising at least 60 percent by weight of a polyethylene selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE), and from about 5 percent by weight to less than 50 percent by weight of a polypropylene selected from the group consisting of polypropylene homopolymer and polypropylene copolymers;
• (b) melt processing the blend to produce a melt-processed article having a first set of dimensions;
• and
• (c) crosslinking the melt-processed article by exposure to radiation to thereby produce said radiation-crosslinked article, wherein a dosage of said radiation is sufficient to impart thermoset characteristics to the article, such that, when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid;
• wherein the blend contains 0 percent by weight of an ethylene-propylene elastomer.

A radiation-crosslinked article comprised of a polymer composition, the polymer composition comprising:

• (a) at least 50 percent by weight of a polyethylene selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE);
• and
• (b) from about 5 percent by weight to less than 50 percent by weight of a polypropylene selected from the group consisting of polypropylene homopolymer and polypropylene copolymers;
• wherein the article is crosslinked by exposure to radiation and possesses a sufficient degree of crosslinking such that when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid;
• wherein the composition contains 0 percent by weight of an ethylene-propylene elastomer.

A process for producing a radiation-crosslinked article, comprising:

• (a) forming a blend comprising at least 50 percent by weight of a polyethylene selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE), and from about 5 percent by weight to less than 50 percent by weight of a polypropylene selected from the group consisting of polypropylene homopolymer and polypropylene copolymers;
• (b) melt processing the blend to produce a melt-processed article having a first set of dimensions;
• and
• (c) crosslinking the melt-processed article by exposure to radiation to thereby produce said radiation-crosslinked article, wherein a dosage of said radiation is sufficient to impart thermoset characteristics to the article, such that, when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid;
• wherein the blend contains 0 percent by weight of an ethylene-propylene elastomer.

A radiation-crosslinked article comprised of a polymer composition, the polymer composition comprising:

• (a) above 60 percent by weight of a polyethylene selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE);
• (b) from about 5 percent by weight to less than 40 percent by weight of a polypropylene selected from the group consisting of polypropylene homopolymer and polypropylene copolymers;
• and
• (c) from 0 to 9 percent by weight of an ethylene-propylene elastomer;
• wherein the article is crosslinked by exposure to radiation and possesses a sufficient degree of crosslinking such that when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid.