Abstract: A polyethylene composition is provided that has a density of about 0.945 to about 0.960 g/cm3 and a melt flow index of about 0.1 to about 0.4. The composition is a melt blend of a linear low density polyethylene resin and/or a linear medium low density polyethylene resin, and a high density polyethylene resin. A feature of the composition is that the resins can independently be virgin, recycled, scrap and/or wide specification resins, and mixtures of these. Methods of producing the compositions and extruded, molded and formed plastic articles manufactured from the compositions are presented.

Abstract: A composition and method for a single or dual wall extruded and thermoformed pipe corrugated HDPE pipe composed of a thermoplastic HDPE that is subsequently cross-linked by introducing moisture. The typical thermoplastic HDPE utilized for blow molding to fabricate the corrugated pipe is cross-linked to enhance dimensional stability, stress crack resistance, impact, creep resistance, and stiffness. The method also may comprise obtaining the enhanced properties by cross-linking the already fabricated linear HDPE corrugated pipe. The cross-linked HDPE is produced using a silane processing method. A composition may comprise a high density polyethylene compound composed with about 1 to 15 percent of finely ground isotropic cross-linked polyethylene recycle.

Abstract: A polyethylene composition is provided that has a density of about 0.945 to about 0.960 g/cm3 and a melt flow index of about 0.1 to about 0.4. The composition is a melt blend of a linear low density polyethylene resin and/or a linear medium low density polyethylene resin, and a high density polyethylene resin. A feature of the composition is that the resins can independently be virgin, recycled, scrap and/or wide specification resins, and mixtures of these. Methods of producing the compositions and extruded, molded and formed plastic articles manufactured from the compositions are presented.

Abstract: Melt blended HDPE compositions for single and dual wall corrugated HDPE pipe and associated fabricated and molded fittings and accessories with enhanced physical properties and processing and environmental stress crack resistance (ESCR) characteristics and associated blend methods are disclosed in which virgin or recycled homopolymer and/or copolymer HDPE resin components are blended. The invention discloses methods for 1) selecting and determining the relative weight fractions of the HDPE blending components that provide specific physical properties and processability of HDPE blended compositions associated with density and melt index respectively and specific values of environmental stress crack resistance (ESCR) associated with specific molecular parameters and 2) for determining from molecular parameters, the ESCR of linear polyethylene resins and blended compositions within a class having similar densities.

Abstract: Melt blended HDPE compositions for single and dual wall corrugated HDPE pipe and associated fabricated and molded fittings and accessories with enhanced physical properties and processing and environmental stress crack resistance (ESCR) characteristics and associated blend methods are disclosed in which virgin or recycled homopolymer and/or copolymer HDPE resin components are blended. The invention discloses methods for 1) selecting and determining the relative weight fractions of the HDPE blending components that provide specific physical properties and processability of HDPE blended compositions associated with density and melt index respectively and specific values of environmental stress crack resistance (ESCR) associated with specific molecular parameters and 2) for determining from molecular parameters, the ESCR of linear polyethylene resins and blended compositions within a class having similar densities.

Abstract: Extrusion dies for forming dual wall corrugated plastic pipe and dual wall plastic pipe having a foam annular core that provides homogenous melt flow to each axially displaced orifice by means of an individual concentric spiral mandrel are disclosed. Spiral mandrels transport the melt from the extruders initially in spiral paths and then to spiral paths having diminishing depths so that the melt from adjacent spiral paths mix axially resulting in an annular path of homogenous melt. Extrusion dies for real time, continuous and remote control of the openings of the axially displaced orifices by moving the die lip closest and furthest from the extruder in a precise manner are also disclosed. A means for controlling separation of the die lips for both the inner and outer wall walls of the pipe gives the pipe manufacturer the benefit of better controlling quality in real time and changing grades on the fly by controlling wall thickness.

Abstract: A corrugator and mold management apparatus and methods for continuously forming transverse corrugations and other shapes in a tubular polymer melt parison formed by an extrusion die employs a plurality of molds that interlock when mated. Each mold has common outside dimensions and a pair of open linear bearings that provide the mold axis and maintain alignment of the molds parallel to and in the same horizontal plane as the axis of the extrusion die. The molds are moved axially along supported rails by bi-directional linear actuating modules and between the pairs of supported rails by lateral transport units. Inner supported rails define the mold tunnel and outer supported rails provide an outer path to move molds upstream back toward the extrusion die. The lateral transport units include extensible rails that facilitate the transfer of molds to and from the mold tunnel and the outer return paths. Delivery units remove from and introduce molds from a plurality of parking stations.

Abstract: Rigid corrugated plastic pipe sections are provided with a flange radially extending from at least one end of the pipe length, which allows structural and water tight joints between connecting flanged pipes and fittings to be formed in an assembly including a peripheral clamp and gasket, and a system, method and kit for effecting structural and water tight joints in corrugated plastic pipe pipes.

Abstract: Corrugated plastic pipe sections having a flanged end formed by a circumferential portion of an end corrugation or section of the pipe liner and a method and kit for joining flanged end corrugated plastic pipe sections are described in a system in which a portion of the end currugation or pipe liner forms a flange and a peripheral flange clamp straddles flanges and draws the flanges together to provide a structurally sound joint. A gasket may be interposed between flanges or the flange periphery and the clamp. The invention achieves a cost effective tight joint, allows field cuts of the corrugated plastic pipe and the fabrication of fittings from corrugated pipe sections and provides a selectable pipe size reducer coupling for corrugated plastic pipe.

Abstract: Mold blocks and methods for thermoforning corrugated plastic pipe that provide a uniform vacuum on the internal lateral surface and optimize forced convective cooling on exterior surface is disclosed. Mating mold blocks have an interior surface with transverse corrugations and an exterior lateral surface having transverse channels containing radial slots that intersect circular slits formed in the interior mold surface. The channels are fitted with a dual cover arrangement that serves to provide (1) a low-resistance vacuum path to the slits located on the interior surface and (2) a forced convective heat transfer path to cool the mold blocks. The cover arrangement is removable, providing a convenient means of inspecting, maintaining and modifying the mold blocks.

Abstract: Melt blended HDPE for pipe and fitting material having a density in the range of 0.945 to 0.955 grams per cubic centimeter, values of melt flow index according to ASTM D1238 less than 0.4 with enhanced physical properties and process characteristics and blend methods are described in which virgin, reprocessed, wide specification, flake or regrind HMW homopolymer and copolymer HDPE (5 to <50%) are included as a minor component and HMW HDPE (>50 to 95%) is the major component. The method of selecting and blending the HMW HDPE copolymer, LMW HDPE homopolymer and LMW HDPE copolymer provides the corrugated HDPE pipe manufacturer with enhanced HDPE compositions and the means to independently design physical properties and enhance processability while exceeding AASHTO's standard for ESCR.

Abstract: Rigid corrugated plastic pipe sections are provided with a flange radially extending from at least one end of the pipe length, which allows structural and water tight joints between connecting flanged pipes and fittings to be formed in an assembly including a peripheral clamp and gasket, and a system, method and kit for effecting structural and water tight joints in corrugated plastic pipe pipes.

Abstract: Extrusion dies and methods for forming dual wall corrugated plastic pipe and dual wall plastic pipe having a foam annular core that provides homogenous melt flow to each axially displaced orifice by means of an individual concentric spiral mandrel are disclosed. Spiral mandrels transport the melt from the extruders initially in spiral paths and then to spiral paths having diminishing depths so that the melt from adjacent spiral paths mix axially resulting in an annular path of homogenous melt. Extrusion die and methods for real time, continuous and remote control of the openings of the axially displaced orifices by moving the die lip closest and furthest from the extruder in a precise manner are also disclosed. A means for controlling separation of the die lips for both the inner and outer wall walls of the pipe gives the pipe manufacturer the benefit of better controlling quality in real time and changing grades on the fly by controlling wall thickness.

Abstract: Mold blocks and methods for thermoforming corrugated plastic pipe that provide a uniform vacuum on the internal lateral surface and optimize forced convective cooling on exterior surface is disclosed. Mating mold blocks have an interior surface with transverse corrugations and an exterior lateral surface having transverse channels containing radial slots that intersect circular slits formed in the interior mold surface. The channels are fitted with a dual cover arrangement that serves to provide (1) a low-resistance vacuum path to the slits located on the interior surface and (2) a forced convective heat transfer path to cool the mold blocks. The cover arrangement is removable, providing a convenient means of inspecting, maintaining and modifying the mold blocks.

Abstract: Melt blended HDPE compositions for single and dual wall corrugated HDPE pipe and associated fabricated and molded fittings and accessories with enhanced physical properties and processing and environmental stress crack resistance (ESCR) characteristics and associated blend methods are disclosed in which virgin or recycled homopolymer and/or copolymer HDPE resin components are blended. The invention discloses methods for 1) selecting and determining the relative weight fractions of the HDPE blending components that provide specific physical properties and processability of HDPE blended compositions associated with density and melt index respectively and specific values of environmental stress crack resistance (ESCR) associated with specific molecular parameters and 2) for determining from molecular parameters, the ESCR of linear polyethylene resins and blended compositions within a class having similar densities.

Abstract: Melt blended HDPE compositions for single and dual wall corrugated HDPE pipe and associated fabricated and molded fittings and accessories having a density in the range of 0.951 to 0.954 grams per cubic centimeter, values of melt flow index according to ASTM D1238 in the range of about 0.15 to 0.35 with enhanced physical properties, process and environmental stress crack resistance (ESCR) characteristics and associated blend methods are disclosed in which virgin or recycled homopolymer and/or copolymer HDPE resin components are blended. The invention discloses a method selecting and determining the relative weight fractions of the HDPE blending components that provides specific physical properties and processability of HDPE blended compositions associated with density and melt index respectively and specific values of environmental stress crack resistance (ESCR) associated with specific molecular parameters.

Abstract: A polyethylene composition is provided that has a density of about 0.945 to about 0.960 g/cm3 and a melt flow index of about 0.1 to about 0.4. The composition is a melt blend of a linear low density polyethylene resin and/or a linear medium low density polyethylene resin, and a high density polyethylene resin. A feature of the composition is that the resins can independently be virgin, recycled, scrap and/or wide specification resins, and mixtures of these. Methods of producing the compositions and extruded, molded and formed plastic articles manufactured from the compositions are presented.

Abstract: Melt blended HDPE for pipe and fitting material having a density in the range of 0.945 to 0.955 grams per cubic centimeter, values of melt flow index according to ASTM D1238 less than 0.4 with enhanced physical properties and process characteristics and blend methods are described in which virgin, reprocessed, wide specification, flake or regrind HMW homopolymer and copolymer HDPE (5 to <50%) are included as a minor component and HMW HDPE (>50 to 95%) is the major component. The method of selecting and blending the HMW HDPE copolymer, LMW HDPE homopolymer and LMW HDPE copolymer provides the corrugated HDPE pipe manufacturer with enhanced HDPE compositions and the means to independently design physical properties and enhance processability while exceeding AASHTO's standard for ESCR.

Abstract: A corrugator and mold management apparatus and methods for continuously forming transverse corrugations and other shapes in a tubular polymer melt parison formed by an extrusion die employs a plurality of molds that interlock when mated. Each mold has common outside dimensions and a pair of open linear bearings that provide the mold axis and maintain alignment of the molds parallel to and in the same horizontal plane as the axis of the extrusion die. The molds are moved axially along supported rails by bi-directional linear actuating modules and between the pairs of supported rails by lateral transport units. Inner supported rails define the mold tunnel and outer supported rails provide an outer path to move molds upstream back toward the extrusion die. The lateral transport units include extensible rails that facilitate the transfer of molds to and from the mold tunnel and the outer return paths. Delivery units remove from and introduce molds from a plurality of parking stations.

Abstract: Corrugated plastic pipe sections having a flanged end formed by a circumferential portion of an end corrugation or section of the pipe liner and a method and kit for joining flanged end corrugated plastic pipe sections are described in a system in which a portion of the end corrugation or pipe liner forms a flange and a peripheral flange clamp straddles flanges and draws the flanges together to provide a structurally sound joint. A gasket may be interposed between flanges or the flange periphery and the clamp. The invention achieves a cost effective tight joint, allows field cuts of the corrugated plastic pipe and the fabrication of fittings from corrugated pipe sections and provides a selectable pipe size reducer coupling for corrugated plastic pipe.