Abstract: A multilayer composite is disclosed comprising a heat shrinkable polymer layer and a nanofiber layer. Methods of forming the composite and uses thereof are also described.

Abstract: A functionalized ethylene-based polymer dissolved in an appropriate solvent and applied to a nonpolar surface can change the surface polarity/characteristics of the nonpolar surface. This change to the surface polarity/characteristics of the nonpolar surface allows adhesion of materials, such as paint, to surfaces such as polypropylene, polyethylene and polyolefin elastomers.

Abstract: A temporary adhesive band provides a releasable sealing structure and a tearing structure in a plastic bag. The band can be coextruded with one or more panels of the bag and can be made from a polymer blend. It can have a relatively thick tear section that defines a tear line at a zone of weakness in the bag so that a closed end of the bag can be easily removed. The band also can have a releasable sealing section that remains attached to the bag after the closed end of the bag has been removed by tearing the bag along the tear line so that the bag can be resealed once it has been opened. The releasable sealing section of the temporary adhesive band is preferably made from a coextruded material with tacky properties so that no additional adhesive is required for resealing the bag.

Abstract: A bulk of polyester polymer particles comprising polyester polymer comprising greater than 75% virgin polyester polymer, the particles having: A) an It.V. of at least 0.72 dl/g, and B) 10 ppm or less of residual acetaldehyde; and C) at least two melting peaks, wherein one of said at least two melting peaks is a low peak melting point within a range of 140° C. to 220° C. and having a melting endotherm area of at least the absolute value of 1 J/g. The particles may also have a degree of crystallinity within a range of 20% and a maximum degree of crystallinity Tcmax defined by the equation: Tcmax=50%?CA?OH where CA is the total mole % of all carboxylic acid residues other than terephthalic acid residues, based on 100 mole % of carboxylic acid residues, and OH is the total mole % of all hydroxyl functional compound residues other than ethylene glycol residues, based on 100 mole % of hydroxyl functional compounds residues.

Abstract: Disclosed is a multilayer film structure, comprising, in order, a puncture resistant layer comprising at least one cyclic olefin copolymer (COC) and at least one ionomer or polyolefin, a tie layer and a sealant layer. The structure can be coextruded and can be prepared using a triple bubble process.

Abstract: A multilayer balloon catheter is formed to have an inner layer and an outer layer, where the outer layer is adapted to resist shredding and premature rupture. The outer layer is formed of a material having a glass transition temperature that is lower than the transition or melting temperature of the inner layer. By forming the balloon on a mold at a temperature between the glass transition temperature of the outer layer and the glass transition or melting temperature of the inner layer, the outer layer will undergo a thermal relaxation that will alleviate some of the axial orientation of the polymer chains that develop during the formation of the multilayer balloon. This relaxation leads to a resistance to shredding when the balloon is expanded during operation.

Abstract: A hollow fibre containing one or more layers having a mean pore size in one or more of said layers of less than 100?m. The invention also extends to a method for preparing porous hollow fibres and to the apparatus for preparing said fibres.

Abstract: The present invention relates to a medical device and method of forming the medical device. In particular, the present invention relates to a medical device having a tubular membrane structure over a radially expandable structural frame, and to a method of forming the tubular membrane on the radially expandable structural frame. In one aspect, a structural frame is placed over a spinning mandrel and a fiber is electro-statically spun over at least a portion of the structural frame forming a membrane. A transfer sheath may be used between the mandrel and structural frame to prevent the electro-statically spun fiber from adhering to the mandrel. In another aspect, a first membrane is spun over the mandrel before the structural frame is placed over the mandrel. In this aspect, at least a portion of the structural frame is sandwiched between the membranes. The membrane or membranes and structural frame form a fiber spun frame assembly. The fiber spun frame assembly may be coated with an elastic polymer.

Abstract: A process that is faster than conventional processes for manufacturing a film tube from a polymer and/or metal film material includes moving the film tube in relation to the joining tools during the joining process. Before the joining process of the film tube, the metal film material exists in the form of at least one film web. The edges of this film web are joined to one another in a joining process forming at least one longitudinal joint seam. During the joining process the film tube is moved in relation to the joining tools.

Abstract: The preparation and use of medical devices having radiopaque and echogenic materials including coated tungsten and/or tungsten carbide particles are disclosed herein.

Abstract: A polymer-based sausage casing suitable for use with uncooked meats such as chorizo is disclosed. A polymer resin is blended with a silicon-based barrier control agent, preferably a polyhedral oligomeric silsesquioxane, to increase the permeability of the sausage casing. The resultant blend can be biaxially stretch-oriented to produce a single-layered polymer-based sausage casing suitable for use with uncooked sausage meats such as chorizo, and specifically suitable for the gas and moisture permeability needed during the curing process for uncooked sausage meats. Such polymer-based casings can also be employed for cooked sausages by choosing a silicon-based barrier control agent that increases gas and moisture barrier, thereby increasing shelf-life for unpeeled sausages. A method for improving the peelability of cooked sausage casings by injecting a thin coating of a releasing agent, without the addition of a surfactant, into the sausage casing during the shirring process is also disclosed.

Abstract: There are provided a vehicle interior finishing laminate sheet in which a polypropylene resin foam board of high foaming extent having interconnected cells is used as a core member, a vehicle interior trim material, a method for manufacturing the vehicle interior finishing laminate sheet, and an apparatus therefor. The present invention relates to a vehicle interior finishing laminate sheet 1 provided with a core member consisting of a polypropylene resin foam board 2. The polypropylene resin foam board 2 is extrusion molded into a plate shape, and has an interconnected cell ratio of 50% or higher and a foaming extent of 10- to 50-fold. A plurality of polypropylene resin foam boards 2, 2 are joined to each other by the hot plate welding method or the laser transmission welding method, whereby a large-size core member of vehicle interior finishing laminate sheet 1, which is used for a roof lining or the like, can be formed.

Abstract: Industrial polyolefin piping system with improved stiffness, impact strength for use at high service temperature, comprising single or multilayer pipes, fitting, chambers, valves and vessels, consisting of ?-nucleated propylene homopolymers with an IR??0.98 having a tensile modulus ?1500 MPa, a Charpy impact strength, notched, at +23° C.?30 kJ/m2 and a Vicat B temperature >90° C. and a Heat Distortion Temperature >100° C. The industrial polyolefin piping system is suitable for chemical plant constructions comprising single or multilayer pipes, fittings, chambers, valves and vessels with improved stiffness, impact strength and high service temperature, preferred for conveyance of natural gas, dangerous liquids and/or toxic liquids.

Abstract: A method for supplying molten polymer and expanding agent flows to a mixing area, by dispersing the expanding agent in a polymer melt by a rapid dividing mixing in a first static mixer, holding and intensively dividingly mixing the thus obtained mixture in a second static mixer, cooling the mixture, during mixing, in a third static mixer to an intermediate temperature, cooling the mixture to a granulation temperature, extruding polymer threads and subsequently quenching and granulating them. During processing, a weight ratio between the polymer melt flow Gp and the expanding agent flow GBA ranges from 13.0 to 19.0, a temperature in the first static mixer for rapid dividing mixing is calculated according to formula (I), in the second and third static mixed according to formulas (II) and (III), respectively, wherein GBA max. is the quantity of a maximum possible expanding agent flow, GBBct.

Abstract: A method for manufacturing a non stick medical tube is provided. The method includes providing a first plastic resin to a tubing extrusion device and providing a second plastic resin to a tubing extrusion device, the second plastic resin comprising a medical grade amide compound. The method further includes mixing the first plastic resin with the second plastic resin and extruding the resin mixture such that said medical grade amide compound is present on an inner surface of said medical tube after extrusion to promote release of contacting surfaces of said inner surface of the medical tubing after contact.

Abstract: A method for extruding transparent and/or translucent article is provided. In one embodiment, the method comprises providing a propylene-based polymer comprising propylene derived units and one or more dienes, the propylene-based polymer having a triad tacticity of from 50% to 99% and a heat of fusion of less than 80 J/g, extruding the propylene-based polymer in the absence of processing oil into an article; and then crosslinking the extruded article.

Abstract: A method for manufacturing a non stick medical tube is provided. The method includes providing a first plastic resin to a tubing extrusion device and providing a second plastic resin to a tubing extrusion device, the second plastic resin comprising a medical grade amide compound. The method further includes mixing the first plastic resin with the second plastic resin and extruding the resin mixture such that said medical grade amide compound is present on an inner surface of said medical tube after extrusion to promote release of contacting surfaces of said inner surface of the medical tubing after contact.

Abstract: Disclosed are implantable or insertable medical devices that provide resistance to microbial growth on and in the environment of the device and resistance to microbial adhesion and biofilm formation on the device. In particular, the invention discloses implantable or insertable medical devices that comprise at least one biocompatible matrix polymer region, an antimicrobial agent for providing resistance to microbial growth and a microbial adhesion/biofilm synthesis inhibitor for inhibiting the attachment of microbes and the synthesis and accumulation of biofilm on the surface of the medical device. Also disclosed are methods of manufacturing such devices under conditions that substantially prevent preferential partitioning of any of said bioactive agents to a surface of the biocompatible matrix polymer and substantially prevent chemical modification of said bioactive agents.

Abstract: Medical devices and methods of making the devices are described. In some embodiments, the methods include a method of manufacturing a device including a first layer and a second layer, the method including the steps of selecting a material for the second layer, the material having a viscosity value at a shear rate of about 1 s?1 or less and at a selected temperature; selecting a nanocomposite material for the first layer that has a viscosity within about 20% to about 125% of the viscosity value of the material for the second layer; and co-extruding the first and second layers.

Abstract: The present invention relates to a composite hollow fibre capillary membrane in particular for exploiting the value of dialysate and a method for the production thereof as well as its use in particular in haemo and peritoneal dialysis.

Abstract: The present invention relates to a multilayer structure based on polyamides and graft copolymers having polyamide blocks, comprising, in this order: a) a first layer (1) formed from a polyamide (A) or else a polyamide (A)/polyolefin (B) blend having a polyamide matrix; b) optionally, a tie layer (2a); c) a layer (2) based on a graft copolymer having polyamide blocks, formed from a polyolefin backbone and from at least one polyamide graft in which: the grafts are attached to the backbone by the residues of an unsaturated monomer (X) having a functional group capable of reacting with a polyamide having an amine end group; the residues of the unsaturated monomer (X) are attached to the backbone by grafting or copolymerization via its double bond; the layers (1), (2a) and (2) being successive and adhering to one another in their respective contact region. One particularly useful application relates to tubes for cooling circuits of internal combustion engines, such as the engines of cars or lorries.

Abstract: As a first aspect, the present invention is directed to a process for making a heat-shrinkable annular film, comprising: (A) extruding an annular extrudate downward from an annular die; (B) quenching the annular extrudate by applying a quenching liquid to the annular extrudate; (C) reheating the extrudate to an orientation temperature of from 130° F. to 210° F., resulting in a reheated annular extrudate; and (D) orienting the reheated annular extrudate while the reheated annular extrudate is in the solid state, the orientation being carried out with a total orientation factor of at least 2, so that the resulting oriented, heat-shrinkable film has a total free shrink at 185° F. of at least 10 percent. The extrudate comprises at least one semi-crystalline polyamide selected from the group consisting of: (i) polyamide 6, (ii) polyamide 66, (iii) polyamide 6/66, and (iv) polyamide 6/12. The semi-crystalline polyamide makes up at least 5 volume percent of the annular extrudate.

Abstract: A multilayer balloon catheter is formed to have an inner layer and an outer layer, where the outer layer is adapted to resist shredding and premature rupture. The outer layer is formed of a material having a glass transition temperature that is lower than the transition or melting temperature of the inner layer. By forming the balloon on a mold at a temperature between the glass transition temperature of the outer layer and the glass transition or melting temperature of the inner layer, the outer layer will undergo a thermal relaxation that will alleviate some of the axial orientation of the polymer chains that develop during the formation of the multilayer balloon. This relaxation leads to a resistance to shredding when the balloon is expanded during operation.

Abstract: A medico-technical flexible polymer tube of thermoplastic or of thermoplastics, a method of manufacturing a medico-technical flexible polymer tube of thermoplastic or of thermoplastics as well as an endoscope comprising a medico-technical flexible polymer tube of thermoplastic or of thermoplastics is provided.

Abstract: A guide catheter shaft is formed from an inner tube structure and a multilayer sheath around the inner tube structure. The multilayer sheath includes an intermediate sheath and a shrink tube layer. The intermediate sheath is disposed around the inner tube and realized from a melt-processible first polyether-block amide material. The shrink tube layer is disposed around the intermediate sheath and realized from a different second polyether-block amide (e.g. a cross-linked polyether-block amide material) having a shrink temperature range greater than a melt temperature range of the first polyether-block amide material. The resulting structure is heated at a temperature within the shrink temperature range such that the outer shrink tube layer shrinks and the intermediate layer melts to thereby bond the multilayer sheath to the inner tube.

Abstract: The present invention provides compositions useful as a barrier layer in, for example, packaging products. The compositions generally comprise a blend of (i) a polyester resin, preferably an aromatic polyester resin such as polyethylene terephthalate (PET) and (ii) a polyamide material (e.g., MXD6). The blend optionally may further comprise (iii) an oxygen scavenging material. The present invention also provides containers (e.g., containers formed by expansion of preforms) having a multilayered body-forming portion including: a core layer comprising the aforementioned blend; and inner and outer layers of a formable polymer composition. The present invention also provides methods of making such containers.

Abstract: A hollow fibre containing one or more layers having a mean pore size in one or more of said layers of less than 100 ?m. The invention also extends to a method for preparing porous hollow fibres and to the apparatus for preparing said fibres.

Abstract: A medical device (10) includes a catheter shaft (11) including inner and outer catheter shafts (12 and 14), and an expandable balloon (18) carried by the catheter shaft (11). The balloon (18) is made from an irradiation cross-linked mixture of a polyamide elastomer and at least one additional cross-linking reactant. The polyamide elastomer can be a polyester amide, a polyether ester amide or a polyether amide, and is preferably a nylon block copolymer. The cross-linking reactant can be: (a) a difunctional material, (b) a trifunctional material, (c) a tetrafunctional material, or (d) an aromatic molecule containing at least two ring substituents, each of the ring substituents having labile hydrogens at a benzylic site therein. The cross-linking reactant can also be diallyl phthalate or meta-phenylene dimaleimide. Irradiation is carried out by exposure to an electron beam or to ultraviolet, X- or gamma radiation, preferably at a total fluence of about 0.5 to about 20 megarads.

Abstract: The invention relates to a multilayer tube comprising (from the inside to the outside of the tube): an optional layer (C1) consisting of at least one fluorinated polymer; a layer (C2) consisting of at least one radiation-grafted fluorinated polymer which is optionally mixed with at least one fluorinated polymer; an optional layer (C3) of adhesive binder; a layer (C4) consisting of at least one polyolefin or a mixture of at least one polyolefin with at least one functionalised polyolefin; a barrier layer (C5) consisting of a metal shield or comprising EVOH or a mixture based on EVOH, a PVDF or a PGA; and an optional layer (C6) consisting of at least one polyolefin.

Abstract: Tubular polymeric member for articles such as tubing and hoses. The member is formed of composition of a nylon alloy.

Abstract: A method for the production of a plastics pipe (9) comprising an inner core and an outer removable skin bonded thereto, which method comprises co-extruding molten polymeric materials forming the inner core and the outer removable skin layer from one or more extruder dies, bringing the polymeric materials together and allowing them to solidify, and conditioning the solidified polymeric materials at a temperature and for a time sufficient to influence the adhesion of the outer skin layer to the inner core, such that on cooling the adhesion of the outer skin layer to the inner core is sufficient to prevent substantial undesired relative movement between the skin layer and the core during installation of the pipe (9), but insufficient to prevent the outer skin layer from being clearly removed by peeling, at least at the ends of the pipe (9), and insufficient to cause a substantial reduction in the impact strength of the inner core.

Abstract: A fuel hose for a resin fuel tank has a triple layer structure including a barrier layer made of an alloy material consisting primarily of EVOH and modified HDPE, and a pair of welding layers made of HDPE and formed on an inner peripheral surface and an outer peripheral surface of the barrier layer, respectively. An opening portion of the fuel hose at one end is configured in the form of an increased diameter portion and also in the form of a thick-walled portion. The increased diameter portion (or the thick-walled portion) is formed by reducing the speed of movement of dies when a hose base body is extruded into an increased diameter portion of a die surface of the dies during extrusion.

Abstract: A hose for use in bio-pharmaceutical applications includes an innermost tubular layer made from a fluoropolymer material. The tubular layer has an inner, relatively smooth and pure surface that defines an opening for transfer of various media. A layer of silicone is disposed next to an outer surface of the innermost tubular layer through use of, for example, an extrusion method. The outer surface of the tubular layer may first be modified by various treatments or chemicals to facilitate the adhesion of the silicone layer thereto. The silicone material may be solid or foamed. A reinforcement layer may be disposed adjacent to an outer surface of the silicone layer. The reinforcement layer may be formed of a wire braid having gaps. An outer jacket of silicone may be attached to the reinforcement layer and to the inner silicone layer through the gaps in the reinforcement layer.

Abstract: A method for manufacturing a compound construction element, in an extrusion process wherein a composite material is pressed through an extrusion die, which composite material includes a matrix of thermoplastic synthetic material including wood particles or other, cellulose containing particles in a content on the order of 50% by weight or more, wherein also one or more elongated additional elements are passed through the extrusion die, which additional elements are brought into tight engagement with the composite material, after which the compound element is shaped and preferably cooled in a die.

Abstract: A prosthetic medical device exhibiting improved wear resistance is fabricated by sealing at least one polyolefinic material in an airtight container and providing an inert atmosphere within the airtight container. The polyolefinic material is exposed to an irradiation source to yield a cross-linked irradiated polyolefinic material. At least one non-irradiated polyolefinic material is blended with the irradiated polyolefinic material, and the prosthetic medical device is formed 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: The present invention is to provide a method of producing multilayer laminates comprising a polyamide and a fluorine-containing ethylenic polymer laminated together and being excellent in interlayer adhesion strength by multilayer coextrusion in an easy and simple manner without need of any additional step or without being limited to some or other particular adhesive material. The present invention is a production method of a multilayer laminate which comprises laminating at least a polyamide (A) and a fluorine-containing ethylenic polymer (B) by simultaneous multilayer coextrusion using a coextrusion apparatus to obtain the laminate comprising said polyamide (A) and said fluorine-containing ethylenic polymer (B), said coextrusion apparatus comprising a die and a plurality of extruders for feeding resins to said die, and the temperature of said die being set within the range exceeding 260° C. but not higher than 310° C.

Abstract: A multi-layer, thermoplastic film bi-axially oriented at a stretching ratio ? to about 3.0:1 in the machine direction and at a stretching ratio ? about 6.0:1 in the transverse direction, which film comprises a layer a) comprising at least 50 wt. % of a crystalline or partially crystalline co-polyamide characterized by a Tg?100° C. and at least one outer heat-sealing layer b) comprising a polyolefin, said film being further characterized in that it has a % free shrink at 100° C.?3 in each direction.

Abstract: An inflatable medical balloon comprises a polymer matrix material and a plurality of fibers distributed in the matrix material. The plurality of fibers operatively adhere to the matrix material and provide reinforcement thereof. The fibers may be parallel or angularly oriented relative to the longitudinal balloon axis, and may be helically disposed thereabout. The fibers may be composed of material which has a greater tensile strength than the matrix material. The fibers may be microfibers formed by phase separation of a melt blend material during extrusion or polymer cores coextruded with the matrix material and surrounded thereby. The balloon may be formed of alternating layers of fiber-free polymer and layers of fiber-containing polymer.

Abstract: Methods of making multilayer structures useful for packaging bone-in meat or other like products are provided. More specifically, the multilayer structures made by the methods provided have sufficient rigidity and strength to contain bone-in meat or other like products, while also maintaining good oxygen barrier properties. In addition, the multilayer structures made by the methods provided can easily seal to themselves or to other structures to provide the packages for the products. Moreover, the multilayer structures made by the methods provided may be biaxially oriented and heat-shrinkable.

Abstract: A nonwoven fabric comprises a first layer formed of staple fibers having a smooth outer surface, a second layer formed of staple fibers having an outer surface with a roughened texture and a third, spunbond layer sandwiched between the first and second layers. A binder material is applied to the second layer which substantially covers its textured surface and is effective to resist deformation under the application of pressure even in the presence of liquid.

Abstract: A flexible, vapor permeable, liquid impermeable composite fabric comprising a ultraviolet light stabilized and thermally stabilized microporous-formable polyolefin barrier layer extrusion laminated to an ultra-violet light stabilized and thermally stabilized polyolefin nonwoven fabric, the composite of which has been incrementally stretched to induce sufficient moisture vapor transmission characteristics while maintaining adequate resistance to water penetration, and methods of making the composite. This composite may be further laminated to one or more layers of either woven or nonwoven materials offering strength and environmental resistance characteristics sufficient for various outdoor applications including covers and building construction products. Embodiments of the above mentioned components have been shown to offer improved liquid resistance, environmental stability, and abrasion resistance as compared to existing commercially available materials.

Abstract: A multilayer sealant film for use in the medical field at least comprises as its innermost layer a first layer comprising at least one resin selected from the group consisting of linear low-density polyethylene, low-density polyethylene, polypropylene and polybutene-1, and a third layer comprising an ethylene-vinyl alcohol copolymer and laminated to the outer side of the first layer with a second layer serving as an adhesive layer and comprising a resin containing, as a main component, at least one of an amorphous polyolefin, adherent polyolefin and ethylene-vinyl acetate copolymer. The ethylene-vinyl alcohol copolymer forming the third layer functions as a barrier for preventing contaminants from migrating from outside of the third layer toward the first layer (innermost layer). Further, it is possible to improve the formability of the multilayer film since the difference in density between the resin for forming the first layer and the resin for forming the second layer is set to be 0.02 g/cm3 or less.

Abstract: The invention relates to a transparent, UV-stabilized, single or multi-layered thermoformable film which contains, as a principal constituent, a crystallizable thermoplastic, preferably polyethylene terephthalate, and at least one UV-stabilizer. The inventive films are characterized by having a good stretchability, thermoformability and good optical and mechanical properties. Said films are suitable for outdoor uses just like shaped bodies made of the same.

Abstract: A multilayer plastic pipe comprising at least three layers, which in turn comprise at least two different polymers, which are a polymer A (barrier layer polymer), which is a particularly good barrier against permeation of the medium to be carried through the pipes embedded in a polymer B (sheathing polymer) in the form of at least one layer which is interrupted at least once by a fillet of polymer B.

Abstract: A process for orienting and drawing multiple-layer thermoplastic materials, in particular of a tubular type, wherein a tube exiting from a heating tunnel is brought up to an orienting temperature of a first material having the highest orienting temperature, while the material of the remaining layers is still in a plastic state. The first material is subjected to a first partial drawing process, while the remaining layers plastically deform to follow its expansion. The temperature of the tube is dropped to the orienting temperature of a second layer and a second layer is drawn, while at the same time continuing to draw the previous layer. Steps of dropping the temperature and drawing the second layer are repeated for the subsequent layers, until the maximum allowable degree of drawing is achieved for each layer.

Abstract: High density polyethylene (HDPE) comprising narrow rheological breadth and narrow molecular weight distribution, and methods for producing such HDPE polymer are disclosed. HDPE blown resins and films produced from the HDPE of the invention, and methods of producing such resins and films are also disclosed. The novel HDPE-derived resins of the invention possess exceptional clarity and gloss in comparison to conventional HDPE-derived resin.

Abstract: Tubular, biaxially stretched, heat shrinkable multilayer film food casings comprising inner and outer polyamide layers on either side of a core layer of EVOH surrounded by an inner and outer adhesive layer, and a coextrusion process for making the film.

Abstract: The present invention provides continuously crimped propylene polymer nonwoven fabrics as well as processes for forming crimped multicomponent propylene polymer fibers by melt-attenuating extruded multicomponent fibers with heated or unheated air wherein the fibers spontaneously crimp without the need for additional heating and/or stretching steps.

Abstract: This invention concerns a multilayer film useful as release sheet for sheet molding compounds, comprising a first skin layer, a second skin layer, a barrier layer for monomeric resins wherein the barrier layer is between the first and second skin layers and the first and second skin layers comprise a mixture of polyolefin and adhesive resin. This invention also pertains to the multilayer films method of production, as well as an SMC sheet employing the multilayer film.

Abstract: At least two techniques can be used separately or together to achieve higher clarity in multilayer blown coextruded films. In a first technique, the core layer is extruded at a higher temperature than the skin layer or layers. In the second technique, the core layer has a higher density than the skin layer or layers. Combinations of these techniques are also contemplated. Either one or both techniques may be used to a sufficient degree to improve clarity (generally lower haze).