Formation of a one-piece polyethylene article

Abstract

To provide a PE material that can be reliably formed without undesirable properties. [Solution] A method for forming a PE article, the method including the steps of: optionally providing a first support; assembling a plurality of polyethylene substrates on the first support, wherein the plurality of polyethylene substrates define a PE structure; applying a second support to the PE structure to position the PE structure between the first support and the second support; positioning the first support, the PE structure, and the second support near a housing; and applying force to the first support, the second support, and the PE structure, thereby causing the first support, the second support, and the PE structure to expand to fit the housing, wherein the housing restricts the first support, the second support, and the PE structure from extending beyond the housing, thereby forming a PE article as the PE structure expands.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Provisional Application No. 63 / 433,132, filed December 16, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] FIELD OF THE DISCLOSURE This disclosure relates generally to apparatus, systems, and methods for processing polyethylene. More particularly, this disclosure relates to apparatus, systems, and methods for processing polyethylene that can be used in medical devices. [Background technology]

[0003] The choice of material is important in providing a functional article. For example, implantable medical devices are often made from specific materials that are both biocompatible and provide a specific function, such as cell adhesion.

[0004] It is not just the choice of material that is important, but the method used to process the material can impart certain qualities, structures, or functions to the processed material that facilitate the function of the article formed from that material. Certain qualities imparted during processing may be necessary for the processed material to be suitable for a particular function. The selection of processing methods is important in a variety of industries, including, but not limited to, the medical device industry, and more specifically, implantable medical devices. However, processed materials may be used in a variety of industries, and properties desired in one industry may be important in other industries as well.

[0005] Many materials are formed into sheets that are then bonded and processed to form specific structures, but these bond points or seams are often weak points in the manufactured article and can cause other undesirable properties, such as particle accumulation. Summary of the Invention [Problem to be solved by the invention]

[0006] There is a need for materials that can be reliably formed without these undesirable properties. [Means for solving the problem]

[0007] The present disclosure relates to methods for forming one-piece expanded polyethylene (ePE) articles from polyethylene (PE) structures, as well as articles and devices produced by the methods. For example, the articles and devices produced by the methods include applying a force to a PE structure to form a PE article. The PE articles can be formed to be one-piece and seamless. The PE articles can also exhibit a desirable set of properties, such as durability, abrasion resistance, a smaller profile, high strength, and anti-thrombogenicity.

[0008] According to one example ("Example 1"), a method of forming a polyethylene (PE) article includes the steps of: optionally providing a first support; assembling a plurality of polyethylene substrates on the first support, wherein the plurality of polyethylene substrates define a PE structure; applying a second support to the PE structure to position the PE structure between the first support and the second support; positioning the first support, the PE structure, and the second support adjacent to a housing; and applying a force to the first support, the second support, and the PE structure, thereby causing the first support, the second support, and the PE structure to expand to fit into the housing, wherein the housing restricts the first support, the second support, and the PE structure from extending beyond the housing, thereby forming a PE article as the PE structure expands.

[0009] According to yet another example ("Example 2") in addition to Example 1, a unitary PE article is obtained by applying a force to the PE structure.

[0010] According to yet another example ("Example 3") in addition to Example 1, the one-piece PE article is seamless.

[0011] According to yet another example ("Example 4") in addition to Example 1, the method further includes disposing the first support, the second support, and the PE structure around a mandrel.

[0012] According to yet another example ("Example 5") in addition to Example 3, the mandrel is porous or perforated.

[0013] According to yet another example ("Example 6") in addition to Example 1, the first support and the second support are formed of silicone.

[0014] According to yet another example ("Example 7") in addition to Example 1, the step of assembling the plurality of polyethylene members further includes a step of assembling other members formed of a material other than PE, including at least one of expanded polyethylene (ePE), polytetrafluoroethylene (PTFE), or expanded polytetrafluoroethylene (ePTFE).

[0015] According to yet another example ("Example 8") in addition to Example 1, the method further comprises the step of heating the PE structure.

[0016] According to yet another example ("Example 9") in addition to Example 1, the step of applying force to the first support, the second support, and the PE structure includes heating a liquid disposed within the mandrel to approximately 130°C, causing the liquid phase to transition to a gas, and applying the force using the gas.

[0017] In addition to Example 8, another example ("Example 10") shows that heating a liquid to gas results in an expansion ratio of the liquid to the gas of approximately 1:1600.

[0018] According to yet another example ("Example 11") in addition to Example 1, applying a force to the first support, the second support, and the PE structure includes releasing a compressed gas.

[0019] According to one example ("Example 12"), a method of forming a monolithic polyethylene (PE) article includes the steps of: positioning a PE structure such that a first portion of the PE structure overlaps a second portion of the PE structure; applying heat to the PE structure; and expanding the PE structure while applying heat to the PE structure.

[0020] According to yet another example ("Example 13") in addition to Example 12, the step of disposing the PE structure includes disposing the PE structure between a first silicone support and a second silicone support.

[0021] According to yet another example ("Example 14") in addition to Example 13, expanding the PE structure includes applying a force to one of the first silicone support and the second silicone support, causing the first silicone support, the PE structure, and the second silicone support to expand together.

[0022] According to yet another example ("Example 15") in addition to Example 14, expanding the PE structure includes applying a force by pressure.

[0023] According to yet another example ("Example 16") in addition to Example 15, pressure is provided by a heated liquid transitioning to a gas.

[0024] According to yet another example ("Example 17") in addition to Example 15, the pressure is provided by compressed gas.

[0025] In addition to Example 14, according to yet another example ("Example 18"), a seamless, one-piece PE article is formed by applying heat and simultaneously expanding the PE structure.

[0026] According to one example ("Example 19"), a method of forming a polyethylene (PE) article includes assembling a PE structure on a first molded support; positioning a punch adjacent to the PE structure; applying a force to the PE structure with the punch such that the punch contacts and presses the PE structure into the first molded support, wherein the PE structure conforms to the shape of the first molded support; applying heat to the PE structure; and releasing the punch from the PE structure to form a PE article, wherein the PE article retains the shape of the first molded support.

[0027] According to yet another example ("Example 20") in addition to Example 19, applying heat to the PE structure includes applying heat at about 130°C.

[0028] According to yet another example ("Example 21") in addition to Example 19, the PE article is densified by a process of applying heat to the PE structure, and the density has a gradient throughout the PE article.

[0029] According to yet another example ("Example 22") in addition to Example 19, the steps of applying force to the punch and applying heat to the PE structure are performed simultaneously.

[0030] According to yet another example ("Example 23") in addition to Example 19, the step of applying heat to the PE structure is carried out while the PE structure is within the first molded support.

[0031] The foregoing examples are merely examples and should not be construed as limiting or otherwise narrowing the scope of any of the inventive concepts provided by the present disclosure. While multiple examples are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. [Brief explanation of the drawings]

[0032] The accompanying drawings are included to provide a further understanding of the disclosure, are incorporated in and constitute a part of this specification, illustrate embodiments, and together with the description, serve to explain the principles of the disclosure.

[0033] [Figure 1] FIG. 1 is a block diagram of a method of forming a polyethylene (PE) article from multiple polyethylene substrates, according to some embodiments.

[0034] [Figure 2] 1 is an illustration of an embodiment of forming a PE article from a PE structure, according to some embodiments.

[0035] [Figure 3] FIG. 3 is a side view of the embodiment of FIG. 2, according to some embodiments.

[0036] [Figure 4] FIG. 1 is a block diagram of a method of forming a unitary PE article, according to some embodiments.

[0037] [Figure 5] 1 is an illustration of an embodiment of forming a unitary PE article, according to some embodiments.

[0038] [Figure 6] FIG. 1 is a block diagram of a method of forming a PE article using a molded support, according to some embodiments.

[0039] [Figure 7] FIG. 1 is a side view of an embodiment of forming a polyethylene PE article using a molded support, according to some embodiments.

[0040] [Figure 8A] FIG. 1 shows the microstructure of the PE article of Example 1 processed above the melt temperature. [Figure 8B] FIG. 1 shows the microstructure of the PE article of Example 1 processed above the melt temperature.

[0041] [Figure 9] FIG. 1 shows thickness data for PE articles of Examples 1 and 2.

[0042] [Figure 10] FIG. 1 shows bubble point data for PE articles of Examples 1 and 2.

[0043] [Figure 11] FIG. 1 shows air leak data for the PE articles of Examples 1 and 2.

[0044] [Figure 12] FIG. 1 shows peel data for the PE article of Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0045] Definitions and Terminology The present disclosure is not intended to be construed in a limiting sense, for example, the terms used in this application should be interpreted broadly in the context of the meaning that one of ordinary skill in the art would give those terms.

[0046] With respect to terms involving imprecision, the terms "about" and "approximately" may be used interchangeably to refer to measurements that include the stated measurement as well as measurements that are reasonably close to the stated measurement. A measurement that is reasonably close to the stated measurement deviates reasonably slightly from the stated measurement to an extent that is understood and easily identified by one of ordinary skill in the art. Such deviations may result from, for example, measurement error, differences in calibration of measuring and / or manufacturing equipment, human error in reading and / or setting measurements, minor adjustments made to optimize performance and / or structural parameters to account for differences in measurements associated with other components, specific implementation scenarios, imprecise adjustment and / or manipulation of objects by humans or machines, etc. If it is determined that a person of ordinary skill in the art would not be able to easily identify such a reasonably small difference, the terms "about" and "approximately" may be understood to mean ±10% of the stated value.

[0047] As used herein, the term "laminate" refers to multiple layers of films, composites, or other materials, such as, but not limited to, polymers, such as, but not limited to, elastomers, elastomeric or non-elastomeric materials, and combinations thereof.

[0048] As used herein, the term "film" generally refers to one or more of a membrane, a composite, or a laminate.

[0049] As used herein, the term "biocompatible material" generally refers to any material that has biocompatible properties, including synthetic materials, such as, but not limited to, biocompatible polymers, or biological materials, such as, but not limited to, bovine pericardium. Biocompatible materials can include the first and second films described herein for various embodiments.

[0050] As used herein, the term "polyethylene" (PE) includes all types of polyethylene, including but not limited to oriented polyethylene (ePE). Description of Various Embodiments

[0051] Those skilled in the art will readily appreciate that the various aspects of the present disclosure may be implemented by any number of methods and apparatus configured to perform the intended functions. It should also be noted that the accompanying drawings referred to herein are not necessarily drawn to scale and may be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the drawings should not be construed as limiting.

[0052] The present disclosure relates to one-piece articles and devices, as well as methods for forming such articles and devices. One-piece articles and devices can be formed from starting materials that include multiple layers, with each layer being processed to form a one-piece, single article in which the multiple layers are indistinguishable from one another. One-piece articles and devices can include articles and devices in which the layers of starting materials are integrated (e.g., intertwined) with one another. In some embodiments, one-piece articles can be formed such that the one-piece articles are seamless and do not include seams created when the layers of starting materials are placed (e.g., rolled) together. One-piece articles and devices can be desirable because they can be formed by methods that reduce undesirable characteristics, such as voids, particle accumulation, or poor layer adhesion. Undesirable characteristics can lead to device defects. Reducing such undesirable characteristics can extend the life of devices and articles.

[0053] One-piece articles can be formed from a polyethylene (PE) substrate. For example, a PE substrate or PE structure can be molded into a one-piece PE article by practicing the methods described herein. For example, one-piece articles and devices can be manufactured by a method including assembling a PE substrate on a first support and a second support; positioning the first support, PE substrate, and second support adjacent to a housing; and applying a force to the first support, PE structure, and second support to form a PE article. PE articles can be one-piece and seamless. PE articles can also exhibit a desirable set of properties, such as durability, abrasion resistance, a smaller profile, high strength, and anti-thrombogenicity.

[0054] The method illustrated in FIG. 1 is provided as an example of various features of the present invention, and although combinations of the illustrated features are clearly within the scope of the present invention, the example and its illustration do not imply that the inventive concepts provided herein are limited to one or more features illustrated in FIG. 1 and do not include fewer, additional, or alternative features.

[0055] Referring more specifically to the method features shown in FIG. 1 , a method 100 for forming a polyethylene (PE) article from a plurality of polyethylene (PE) substrates is provided according to some embodiments. Method 100 can be implemented in a variety of contexts, including, but not limited to, the preparation and manufacture of medical devices, which may include implantable medical devices. Various forms of PE can be implemented in the method, including, but not limited to, membranes, films, tapes, tubes, and the like. It is further understood that PE can have a variety of properties, including thickness, fibril and node structure, porosity, density, and the like. Thus, the embodiments discussed herein are not limited to any particular initial condition or morphology, but are understood to broadly encompass any PE starting material suitable for the described method.

[0056] In some embodiments, as shown in FIG. 1, a method 100 of forming a PE article from a plurality of PE substrates can include step 110 of optionally providing a first support; step 120 of assembling the plurality of PE substrates on the first support, wherein the plurality of PE substrates define a PE structure; step 130 of applying a second support to the PE structure; step 140 of positioning the first support, the PE structure, and the second support adjacent to a housing; and step 150 of applying a force to the first support, the PE structure, and the second support to form a PE article.

[0057] Further to Figure 1, in optional step 110 of providing a first support, the first support may be formed of silicone. In some embodiments, the first support may be similar to first support 210 shown in Figure 2. In some embodiments, the first support is provided as a silicone tube (see first support 210 in Figure 2). However, the first support may be provided in any shape or size suitable for the application.

[0058] Further to FIG. 1 , in step 120, a plurality of PE substrates are assembled on a first support, where the plurality of PE substrates define a PE structure. The plurality of PE substrates may include, but are not limited to, individual sheets, tapes, films, extruded members, or laminates of PE. The plurality of PE substrates may be provided in any size or thickness suitable for the application. Each PE substrate of the plurality of PE substrates may be provided in the same size or thickness, or in various sizes and thicknesses. The plurality of PE substrates may also be provided in any shape suitable for the application. The PE substrates may be assembled on the first support in an environment suitable for the application or materials used. The environment may include, but is not limited to, a cooled (e.g., refrigerated) environment, a room temperature environment, or a heated environment.

[0059] Furthermore, step 120 of assembling a plurality of PE substrates on a first support, where the plurality of PE substrates define a PE structure, can further include assembling other substrates formed of materials other than PE. It is understood that instead of starting with a PE substrate, substrates formed of other materials, such as expanded polyethylene (ePE), polytetrafluoroethylene (PTFE), and expanded polytetrafluoroethylene (ePTFE), are also possible. The use of other absorbable or resorbable materials is also contemplated. For example, a composite material can be formed as described by the methods described herein. The composite material can include multiple layers, such as a base layer and an outer layer. The multiple layers can include one type of material or multiple types of materials. The base layer and outer layer can include a biostable material (e.g., PTFE or PE) suitable for direct exposure to blood or biological tissue.

[0060] Further to FIG. 1 , in step 130 of applying a second support to the PE structure, the PE structure can be disposed between a first support and a second support. In some embodiments, the second support can also be formed of silicone. The second support can be similar to second support 230 shown in FIG. 2. In some embodiments, the second support is a silicone tube (see second support 230 in FIG. 2 ). However, the second support can be provided in any shape or size suitable for the application. In some embodiments, the first support, PE structure, and second support can be cylindrical or tubular. This can be done by wrapping the PE structure around the first support and wrapping the second support around the PE structure constructed in a layered structure (see, for example, FIGS. 2 and 3 ). A cylindrical configuration can be one in which the first support is the inner support of the PE structure and the second support is the outer support of the PE structure. In other configurations, the first substrate, PE structure, and second substrate may be flat and the layers applied in a stacked configuration, although other configurations and shapes (e.g., spherical) are also contemplated.

[0061] Further to FIG. 1 , in step 140 of disposing the first support, the PE structure, and the second support near a housing, the housing can be provided in any size or shape suitable for the application. The housing can be similar to housing 240 of FIGS. 2 and 3. In some embodiments, the second support is disposed between the PE structure and the housing such that the second support acts as a cushion for the PE structure. Step 140 of disposing the first support, the PE structure, and the second support near the housing can further include providing a mandrel around which the first support, the second support, and the PE structure are disposed. The mandrel can be similar to mandrel 220 shown in FIG. 2. In some embodiments, the mandrel can be provided within the housing.

[0062] 1 , the method further includes step 150 of applying a force to the first support, the PE structure, and the second support to form a PE article. The application of the force may cause the first support (e.g., first support 210 of FIG. 2 ), the second support (e.g., second support 230 of FIG. 2 ), and the PE structure (e.g., PE structure 200 of FIG. 2 ) to expand or widen to fit into a housing (e.g., housing 240 of FIG. 2 ). In some embodiments, the housing may restrict the first support, the second support, and the PE structure from expanding beyond the housing, thereby forming a PE article (e.g., PE article 260 of FIG. 2 ) as the PE structure expands. In some embodiments, as the PE structure expands, it conforms to the shape of the housing, such that the PE article takes on the shape of the housing. In some embodiments, the first silicone support and the second silicone support may be corrugated or textured on their surfaces, such that the corrugations or texture are transferred to the PE structure upon application of the force. In some embodiments, a one-piece PE article is formed by applying force to the first support, the PE structure, and the second support to form a PE article in step 150. In some embodiments, the one-piece PE article can be defined such that the layers of the PE structure are integrated (e.g., intertwined) with one another. The one-piece PE article can be formed such that the one-piece PE article is seamless and the layers of the PE structure are indistinguishable from one another. Details regarding the changes in structure and material properties are discussed in connection with Examples 1 and 2.

[0063] In some embodiments, the one-piece PE article can be formed such that the layers of the PE structure are integrated (e.g., intertwined) with one another. In some embodiments, the one-piece PE article is formed without adhesive bonding. In some embodiments, the one-piece PE article is seamless, such that the layers of the PE structure are indistinguishable. In some embodiments, the one-piece PE article is dense or non-porous. In some embodiments, the one-piece PE article is textured from the textured or corrugated surfaces of the first and second supports.

[0064] In some embodiments, when the starting material is an ePE structure, a one-piece ePE article is formed. The ePE structure can be processed by the methods described above with respect to Figure 1. In some embodiments, the one-piece ePE article is processed to a partially densified state. In other embodiments, the one-piece ePE article is processed to a fully densified state.

[0065] In some embodiments, PE articles (e.g., PE article 260 of FIG. 2) can be formed by the methods described herein, and the material processing methods can impart properties such as improved durability, abrasion resistance, smaller profile, high strength, and thrombogenicity. This can be due to better integration of the layers of the PE structure (e.g., by applying force instead of adhesives), which can reduce voids between layers, delamination, loosening, or fraying. Eliminating these properties reduces potential defect points in the PE article. Forming a seamless PE article can also reduce defect propagation points and defects between layers, which can extend the life of the PE article. Additionally, forming a seamless PE article can improve thrombogenicity by reducing areas that can develop thrombus. PE articles formed by method 100 can have thin-walled profiles. In some embodiments, the thin-walled profile of the PE article can range from about 0.001 inches to about 0.040 inches in thickness. In some embodiments, the thickness may be in the range of about 0.001 inch to about 0.004 inch, about 0.004 inch to about 0.008 inch, about 0.008 inch to about 0.012 inch, about 0.012 inch to about 0.016 inch, about 0.016 inch to about 0.020 inch, about 0.020 inch to about 0.024 inch, about 0.024 inch to about 0.028 inch, about 0.028 inch to about 0.032 inch, about 0.032 inch to about 0.036 inch, and about 0.036 inch to about 0.040 inch. The thickness may be measured around the periphery of the PE article after the layers of the PE structure have been consolidated or intertwined.

[0066] In some embodiments, the PE article can be molded into or provided as a medical device or medical device component. Medical devices can include implantable medical devices. The PE article can be molded into a tubular structure and implemented, for example, as a graft. The PE article can be molded into a flattened structure and implemented, for example, as a hernia patch, cardiovascular patch, nerve membrane, etc.

[0067] In some embodiments, applying force to the first support, the PE structure, and the second support to form the PE article 150 can further include heating a liquid to transition from a liquid phase to a gas. In some embodiments, the liquid can be heated to about 130°C. In other embodiments, the liquid can be heated to a temperature of about 110-130°C, about 130-150°C, or about 150-180°C. In some embodiments, the liquid is liquid water, and heating the liquid water can transition the liquid water phase to a vapor. When the liquid undergoes a phase change, the gas expands, creating pressure, which applies a force to the first support, the PE structure, and the second support. In some embodiments, heating the liquid can be performed while the liquid is disposed within a mandrel around which the first support, the PE structure, and the second support are disposed. In some embodiments, the mandrel is porous or perforated, allowing gas to escape through the mandrel. In some embodiments, the mandrel is hollow, allowing water to enter the interior of the mandrel. In some embodiments, the liquid is heated to a gas, resulting in an expansion ratio of the liquid to the gas of about 1:1600.

[0068] In other embodiments, step 150 of applying force to the first support, the PE structure, and the second support to form a PE article can further include releasing a compressed gas. In some embodiments, the released compressed gas can apply force by exposing the first support (e.g., first support 210 in FIG. 2), the PE structure (e.g., PE structure 200 in FIG. 2), and the second support (e.g., second support 230 in FIG. 2) to the compressed gas upon release of the compressed gas. The release of the compressed gas can apply force to the first support, the PE structure, and the second support depending on the rate at which the compressed gas is released or the pressure gradient between the inner side (e.g., the side in contact with the gas) and the outer side of the first support, the PE structure, and the second support. In some embodiments, the compressed gas can be inert. In some embodiments, the compressed gas can be stored in a mandrel (e.g., mandrel 220 in FIG. 2) and released therefrom to apply force. In other embodiments, the housing can be connected to an external source of compressed gas, which applies the compressed gas to the first support, the PE structure, and the second support, thereby exerting the force.

[0069] In some embodiments, the method 100 for forming a PE article from multiple PE substrates can further include heating the PE structure. The PE structure (e.g., PE structure 200 of FIG. 2) can be heated to a temperature above the melting temperature or glass transition temperature of PE. This temperature can be about 130°C, about 110-130°C, about 130-150°C, or about 150-180°C. Heat can be supplied from a heated environment (e.g., an oven). Heat can be applied from a heat source directed toward the exterior surface of the PE structure (e.g., the portion of the PE structure in contact with the second support) or from a heat source directed toward the interior surface of the PE structure (e.g., the portion of the PE structure in contact with the first support or the interior of an internal lumen). In some embodiments, at least a portion of the heat applied to the PE structure can be supplied by the same mechanism that applies force to expand the PE structure, including, for example, heating to transition a liquid to a gas or releasing a compressed gas.

[0070] In some embodiments, the step of heating the PE structure (e.g., PE structure 200 of FIG. 2 ) can be performed before step 150 of applying a force to the first support, the PE structure, and the second support to form a PE article. In some embodiments, the step of heating the PE structure can be performed simultaneously with step 150 of applying a force to the first support, the PE structure, and the second support to form a PE article. In some embodiments, applying heat to the PE structure forms a unitary structure (e.g., a seamless tube). In some embodiments, the PE structure can be molded into a medical device or medical device component. In some embodiments, the PE structure comprises ePE, applying heat and force to the PE structure densifies the PE structure.

[0071] In some embodiments, the PE structure is cooled after being exposed to heat. The PE structure can be cooled at room temperature, placed in an environment that is colder than room temperature (e.g., a freezer), or can be slowly cooled in an environment that is warmer than room temperature. In some embodiments, the environment in which the densified PE structure is cooled can be a steady temperature or a variable temperature. In some embodiments, the variable temperature of the environment allows the PE structure to cool at a controlled rate. The cooling rate of the PE structure can be constant or variable.

[0072] 2 is an illustration of an embodiment of forming a PE article from a PE structure, according to some embodiments. In some embodiments, the illustration of FIG. 2 follows the method 100 described with respect to FIG.

[0073] FIG. 2 illustrates a PE structure 200. In some embodiments, the PE structure 200 can include multiple PE substrates. In this embodiment, the PE structure 200 is shown in contact with a first support 210. The PE structure 200 can be applied to the outside of the first support 210. In this embodiment, the inside of the first support 210 is shown in contact with a mandrel 220. The first support can be applied around the outer surface of the mandrel. In this embodiment, the PE structure 200, the first support 210, and the mandrel 220 are all shown as cylindrical in shape. However, other shapes for the PE structure 200, the first support 210, and the mandrel 220 are contemplated, such as spherical, rectangular, etc.

[0074] A second support 230 can be applied to the PE structure 200. In this embodiment, the second support 230 is applied to the exterior side of the PE structure 200, thereby disposing the PE structure 200 between the first support 210 and the second support 230. In this embodiment, the first support 210, the PE structure 200, and the first support 230 are all disposed around the mandrel 220. In some embodiments, the first support 210 and the second support 230 are formed from silicone. However, embodiments in which the first support 210 and the second support 230 are formed from a flexible material other than silicone are also contemplated.

[0075] The first support 210, the PE structure 200, and the second support 230 are disposed near the housing 240. In some embodiments, the mandrel 220 is part of the housing 240, while in other embodiments, the mandrel 220 can be separate from the housing 240 and disposed near the housing 240. In further embodiments, the mandrel 220 can be separate from the housing 240, and the housing 240 can be disposed such that the housing 240 surrounds the mandrel 220. In this embodiment, the housing 240 has a cylindrical periphery. However, other peripheral shapes for the housing 240 can be utilized depending on the desired shape of the final PE article.

[0076] 2 , after first support 210, PE structure 200, and second support 230 are positioned adjacent housing 240, force 250 can be applied. Applying force 250 to first support 210, PE structure 200, and second support 230 can cause first support 210, PE structure 200, and second support 230 to expand to fit housing 240. Housing 240 is positioned such that first support 210, PE structure 200, and second support 230 are restricted from extending beyond housing 240. PE article 260 is formed as PE structure 200 expands.

[0077] In this embodiment, force 250 is a radially outward force. In some embodiments, force 250 applied to the PE structure may be a tensile force applied transversely or longitudinally. The tensile force may include stretching the PE structure to a longer length. In further embodiments, force 250 applied to the PE structure may be a combination of a radial force and a tensile force. In this embodiment, force 250 may be derived from mandrel 220 because mandrel 210 is porous or perforated. In some embodiments, mandrel 220 may have a liquid disposed therein that is heated to transition from a liquid phase to a gas, which migrates through the holes or perforations and exerts force 250. In other embodiments, force 250 may be exerted by the release of compressed gas.

[0078] Further to FIG. 2 , applying force 250 to the PE structure forms PE article 260. When mandrel 220 and housing 240 are removed, the formed PE article 260 is plastically deformed and retains the expanded radial dimension of the housing. First support 210 and second support 230 may also be elastically deformed, in which case first support 210 and second support 230 temporarily retain their expanded radial dimension but can then return to a smaller dimension. This allows first support 210 and second support 230 to be reused in subsequent manufacturing. In this embodiment, when first support 210 and second support 230 are removed, PE article 260 continues to retain its expanded radial dimension. In some embodiments, PE article 260 is a one-piece PE article. In some embodiments, the one-piece PE article is seamless. In this embodiment, the unitary PE article 260 is formed without adhesive, and instead of adhesive, a force 250 is applied to consolidate or intertwine the PE structural layers to form the PE article.

[0079] In some embodiments, as discussed above with respect to FIG. 1, the PE article 260 can be formed with desirable properties such as improved durability, abrasion resistance, smaller profile, high strength, and anti-thrombogenicity.

[0080] In this embodiment, the PE article 260 can be formed into a tubular structure and implemented, for example, as a graft. Other tubular medical devices or members are also contemplated.

[0081] FIG. 3 is a side view of the embodiment of FIG. 2 according to some embodiments. In this embodiment, housing 240 is shown as having a constant circular cross-section. The constant circular cross-section of housing 240 results in a PE article 260 having a corresponding constant circular cross-section, which can provide a constant thickness throughout the length of PE article 260. This can be used to form a PE article with a constant circular cross-section for a medical device or medical device component. For example, a graft or graft component can be formed. However, in other embodiments, housing 240 can have a variable cross-section. For example, in some embodiments, one end of housing 240 can have a circular cross-section and the other end can have a D-shaped cross-section. This can be used to form a PE article with a variable cross-section for a medical device or medical device component. For example, variable cross-section housing 240 can be used to form a bifurcated graft or bifurcated graft component. In other examples, some embodiments can have a variable thickness housing, in which case the PE article is formed to have a variable thickness along the length of PE article 260.

[0082] In some embodiments, the layers of PE structure 200 may be wrapped lengthwise around first substrate 210 in a cigarette-like fashion. However, other types of configurations are contemplated, including, but not limited to, spiral wrapping. In some embodiments, PE structure 200 has a seam formed lengthwise along PE structure 200 prior to heating and expansion. However, during a method step (e.g., method 100 shown in FIG. 1 ), the seam disappears to form a seamless PE article 260 (e.g., a seamless tubular structure).

[0083] 4 is a block diagram of a method 400 of forming a monolithic polyethylene (PE) article according to some embodiments. Method 400 can be implemented in a variety of contexts, including but not limited to, medical devices, which may include implantable medical devices.

[0084] In some embodiments, as shown in FIG. 4 , a method 400 of forming a unitary polyethylene (PE) article can include step 410 of positioning a PE structure such that a first portion of the PE structure overlaps a second portion of the PE structure, step 420 of applying heat to the PE structure, and step 430 of expanding the PE structure while applying heat.

[0085] Further to FIG. 4 , in step 410 of placing the PE structure such that a first portion of the PE structure overlaps a second portion of the PE structure, it is understood that in some embodiments, the PE structure can be formed from multiple PE substrates. In other embodiments, the multiple substrates can be other forms of polyethylene, including, but not limited to, ePE substrates or PTFE substrates. The multiple members can include, but are not limited to, individual sheets, tapes, films, extruded members, or laminates. In some embodiments, the first portion of the PE structure (e.g., first portion 510 of FIG. 5 ) can be one member of the multiple members, and the second portion of the PE structure (e.g., second portion 520 of FIG. 5 ) can be a different member of the multiple members. In some embodiments, the first portion of the PE structure and the second portion of the PE structure can be the same shape and size, such that the overlapping of the first and second portions of the PE structure can cover the other of the first and second portions of the PE structure. In other embodiments, the first portion of the PE structure and the second portion of the PE structure may be different shapes and sizes.

[0086] Step 410 of positioning the PE structure such that the first portion of the PE structure overlaps the second portion of the PE structure can further include positioning the PE structure (e.g., PE structure 500 of FIG. 5) between a first silicone support (e.g., first silicone support 515 of FIG. 5) and a second silicone support (e.g., second silicone support 525 of FIG. 5). In some embodiments, the PE structure is sandwiched between the first silicone support and the second silicone support. In some embodiments, the first silicone support and the second silicone support are tubes. In some embodiments, the PE structure is wrapped around the first silicone support, thereby forming the PE structure as a PE structure tube. In some embodiments, the PE structure tube is configured such that the second portion of the PE structure is outside the first portion of the PE structure, as shown in FIG. 5. In other embodiments, an inverse configuration of the PE structure is formed, where the first portion of the PE structure is outside the second portion of the PE structure. This PE structure tube configuration may only be apparent prior to the step of heating and / or applying force to the PE structure tube. The PE structure can have multiple layers that together form the PE structure. In some embodiments, the PE structure is wrapped around a mandrel (e.g., mandrel 530 in Figure 5).

[0087] Further to FIG. 4 , step 420 of applying heat to the PE structure can be performed at a temperature near the melting temperature or glass transition temperature of the PE. In some embodiments, heat can be applied at a temperature of about 130° C., about 110-130° C., about 130-150° C., or about 150-180° C. In some embodiments, heat can be supplied from a heated environment (e.g., an oven). In some embodiments, heat can be applied from a heat source directed at an exterior surface of the PE structure (e.g., the portion of the PE structure in contact with the second support) or an interior surface of the PE structure (e.g., the portion of the PE structure in contact with the first support or the interior of an inner lumen).

[0088] Further to FIG. 4 , step 430 of applying heat and simultaneously expanding the PE structure can include applying a force to one of the first silicone support and the second silicone support, causing the first silicone support, the PE structure, and the second silicone support to expand together. In some embodiments, the first silicone support, the PE structure, and the second silicone support expand together radially to form a tube. In other embodiments, the first silicone support, the PE structure, and the second silicone support are compressed together axially (e.g., laterally or longitudinally) to form a flattened structure. In further embodiments, the first silicone support, the PE structure, and the second silicone support expand together both radially and axially. In some embodiments, the heat can be applied by a mandrel (e.g., mandrel 530 of FIG. 5 ).

[0089] In some embodiments, applying heat and simultaneously expanding the PE structure 430 can further include applying a force by pressure. In some embodiments, the heat and / or pressure is provided by a heated liquid transitioning to a gas. In some embodiments, the heated liquid is water and the gas is water vapor. The heated liquid transitioning to a gas can be applied from the interior side of the tubular PE structure, resulting in a radial expansion of the tubular PE structure. In some embodiments, the heated liquid can be supplied into a mandrel (e.g., mandrel 530 in FIG. 5) and applied to the PE structure through holes or perforations on the surface of the mandrel.

[0090] In other embodiments, the heat and / or pressure is provided by a compressed gas, which may include an inert compressed gas, and the pressure from the compressed gas may be applied to the interior of the tubular PE structure (e.g., from mandrel 530 in FIG. 5 ) to radially expand the tubular PE structure. In some embodiments, the released compressed gas may apply heat and / or pressure by exposing the PE structure (e.g., PE structure 500 in FIG. 5 ) to the compressed gas upon release of the compressed gas. The release of the compressed gas may apply heat and / or pressure depending on the rate at which the compressed gas is released or depending on a pressure gradient between the interior side (e.g., the side in contact with the gas) and the exterior side of the tubular PE structure.

[0091] In some embodiments, applying heat and simultaneously expanding the PE structure in step 430 can form a seamless, one-piece PE article. In this embodiment, because the one-piece PE article is seamless, the first portion of the PE structure can be indistinguishable from the second portion of the PE structure. The first portion of the PE structure can be intertwined or integrated with the second portion of the PE structure.

[0092] In some embodiments, a one-piece PE article (e.g., one-piece PE article 560 of FIG. 5) can be formed by the methods described herein, and the material processing methods can impart properties such as improved durability, abrasion resistance, smaller profile, high strength, and thrombogenicity. This can be due to better integration of the layers of the PE structure (e.g., by applying force instead of adhesives), which can reduce voids between layers, delamination, loosening, or fraying. Eliminating these properties reduces potential defect points in the PE article. Forming a seamless PE article can also reduce defect propagation points and defects between layers, which can extend the life of the one-piece PE article. Additionally, forming a seamless PE article can improve thrombogenicity by reducing areas that can become thrombogenic. The one-piece PE article formed by method 400 can have a thin-walled profile. In some embodiments, the thickness may range from about 0.001 inch to about 0.004 inch, from about 0.004 inch to about 0.008 inch, from about 0.008 inch to about 0.012 inch, from about 0.012 inch to about 0.016 inch, from about 0.016 inch to about 0.020 inch, from about 0.020 inch to about 0.024 inch, from about 0.024 inch to about 0.028 inch, from about 0.028 inch to about 0.032 inch, from about 0.032 inch to about 0.036 inch, and from about 0.036 inch to about 0.040 inch.

[0093] In some embodiments, the PE article can be molded into or provided as a medical device or medical device component. Medical devices can include implantable medical devices. The PE article can be molded into a tubular structure and implemented, for example, as a graft. The PE article can be molded into a flattened structure and implemented, for example, as a hernia patch, cardiovascular patch, nerve membrane, etc.

[0094] 5 is an illustration of an embodiment of forming a monolithic (PE) article, according to some embodiments. In some embodiments, the illustration of FIG. 5 follows the method 400 described in FIG.

[0095] 5 illustrates that the first portion 510 of the PE structure and the second portion 520 of the PE structure are offset from one another and partially overlap one another. In some embodiments, the first portion 510 of the PE structure and the second portion 520 of the PE structure may be the same shape and size. In other embodiments, the first portion 510 of the PE structure and the second portion 520 of the PE structure may be different shapes and sizes. The PE structure 500 may include an overlapping stack of PE portions, including the first portion 510 of the PE structure and the second portion 520 of the PE structure. In this embodiment, the first portion 510 of the PE structure and the second portion 520 of the PE structure are substantially the same shape and size, such that the second portion 520 of the PE structure can completely cover the first portion 510 of the PE structure.

[0096] Similar to the embodiment shown in FIG. 2, the PE structure 500 can be applied to a mandrel 530. In this embodiment, the PE structure 500 is wound in a tubular shape around the mandrel 530. In some embodiments, the PE structure 500 can be disposed between a first silicone support 515 and a second silicone support 525. In some embodiments, the first silicone support 515 and the second silicone support 525 are substantially the same as the first silicone support 210 and the second silicone support 230 of FIG. 2. Furthermore, in some embodiments, the PE structure can be disposed near a housing 540. In some embodiments, the PE structure is disposed within the housing 540.

[0097] In some embodiments, heat can be applied to the PE structure 500 at a temperature near the glass transition temperature of the material. This temperature can be about 130°C, about 110-130°C, about 130-150°C, or about 150-180°C. In some embodiments, the PE structure 500 can be expanded simultaneously with the application of heat to the PE structure 500. Similar to FIG. 2, expanding the PE can include applying a force 550. In this embodiment, the force 550 can be a radial outward force and can be applied from a mandrel 530. In some embodiments, the force 530 can be a pressure force, where the pressure is generated by heated water transitioning to steam or by the release of compressed gas.

[0098] After applying heat to PE structure 500 to expand PE structure 500, seamless, integral PE article 560 is formed. Seamless PE article 560 is comprised of first and second PE structure portions 510, 520. However, once seamless, integral PE article 560 is formed, first PE structure portion 510 and second PE structure portion 520 are indistinguishable from one another and are integrated or intertwined.

[0099] In some embodiments, as discussed above with respect to FIG. 4, the PE article 560 can be formed with desirable properties such as improved durability, abrasion resistance, smaller profile, high strength, and anti-thrombogenicity.

[0100] In this embodiment, the unitary PE article 560 can be molded into a tubular structure and implemented, for example, as a graft. Other tubular medical devices or members are also contemplated.

[0101] 6 is a block diagram of a method 600 for forming an expanded polyethylene (ePE) article using a molded support, according to some embodiments. Method 600 can be implemented in a variety of contexts, including, but not limited to, medical devices, which may include implantable medical devices.

[0102] In some embodiments, as shown in FIG. 6 , a method 600 of forming a PE article can include step 610 of assembling a PE structure on a first mold support, step 620 of positioning a punch adjacent to the PE structure, step 630 of applying a force to the PE structure with the punch, step 640 of applying heat to the PE structure, and step 650 of releasing the punch from the PE structure to form the PE article.

[0103] Further to Figure 6, assembling 610 the PE structure on the first shaped support can further include using a second support to hold the PE structure in place (e.g., second support 740 of Figure 7). In some embodiments, the first shaped support (e.g., first shaped support 720 of Figure 7) can be formed of a rigid material. In other embodiments, the first shaped support can be formed of a flexible material (e.g., silicone).

[0104] Further to FIG. 6, step 620 of positioning a punch adjacent the PE structure can further include providing a shaped punch (see punch 730 in FIG. 7). In some embodiments, the shaped punch includes, but is not limited to, rounded or straight edges. The rounded or straight edges can be complementary to the first shaped support. In some embodiments, the shaped punch can be shaped to fit the first shaped support (see FIG. 7). In other embodiments, the shape of the shaped punch may not correspond to the shape of the first shaped support.

[0105] Further to Figure 6, step 630 of applying a force to the PE structure with a punch can further include applying a force to the PE structure with a punch such that the punch contacts the PE structure and presses the PE structure into the first shaped support. The PE structure can conform to the shape of the first shaped support. In some embodiments (e.g., the embodiment of Figure 7), the first shaped support can have a concave shape, and the PE structure is pressed into the concave shape by the punch, causing the PE structure to stretch to conform to the concave shape.

[0106] Further to FIG. 6 , applying heat to the PE structure step 640 can include applying heat to the PE structure at a temperature near the melting temperature or glass transition temperature of the PE structure. This temperature can be about 130° C., about 110-130° C., about 130-150° C., or about 150-180° C. In some embodiments, heat can be applied to the PE structure from a punch, where the punch is a heated punch. In other embodiments, heat can be applied to the PE structure from a first molding support. In further embodiments, heat can be applied to the PE structure from the environment (e.g., an oven or heated environment). In some embodiments, applying heat to the PE structure step 640 is performed while the PE structure resides in the first molding support to form a PE article (e.g., PE article 760 of FIG. 7 ).

[0107] In some embodiments, applying heat to the PE structure 640 densifies the PE article. In some embodiments, the PE article has a density gradient throughout the article. In this embodiment, the portion of the PE article with higher density may be the portion of the PE structure that extends deepest into the shape of the first support (see PE structure 710 in FIG. 7). In other embodiments, the PE article may be uniformly densified. In some embodiments, the PE article is one-piece. In some embodiments, the PE article is seamless.

[0108] In some embodiments, step 630 of applying a force to the PE structure with a punch and step 640 of applying heat to the PE structure are performed simultaneously. In other embodiments, step 630 of applying a force to the PE structure with a punch is performed before step 640 of applying heat to the PE structure. In further embodiments, step 640 of applying heat to the PE structure is performed before step 630 of applying a force to the PE structure with a punch.

[0109] Further to FIG. 6 , step 650 of releasing the punch from the PE structure to form the PE article can further include the step of the PE article retaining the shape of the first shaped support. In some embodiments, the PE article is a one-piece PE article. In some embodiments, one-piece PE articles can be formed with desirable properties such as improved durability, abrasion resistance, smaller profile, high strength, and anti-thrombogenicity. This may be due to better integration and intertwining of the layers of the PE structure (e.g., by applying force instead of adhesive), which may reduce voids between layers, delamination, loosening, or fraying of layers. This may reduce defect points in the PE article. Forming a seamless PE article may also reduce defect propagation points, all of which may increase the lifespan of the PE article. Furthermore, forming a seamless PE article may also improve anti-thrombogenicity.

[0110] In some embodiments, the PE article can be molded into or provided as a medical device or medical device component. Medical devices can include implantable medical devices. The PE article can be molded into a tubular structure and implemented, for example, as a graft. The PE article can be molded into a flattened structure and implemented, for example, as a hernia patch, cardiovascular patch, nerve membrane, etc.

[0111] 7 is a side view of an embodiment of forming an expanded polyethylene (ePE) article using a molded support, according to some embodiments. In some embodiments, the illustration of FIG. 7 follows the method 600 described in FIG.

[0112] FIG. 7 shows a PE structure 710 assembled on a first shaped support 720. In some embodiments, the PE structure 710 can include multiple PE substrates. In some embodiments, the multiple PE substrates can include, but are not limited to, individual sheets, tapes, films, extrusions, or laminates of PE. In some embodiments, the first shaped support 720 has a recessed portion 715 defining a first shape. In some embodiments, the PE structure 710 is held in place by a second support 740. In some embodiments, the first shaped support is formed of a flexible material (e.g., silicone). In other embodiments, the first shaped support can be formed of a rigid material. The first shaped support 720 and the second support can be formed of the same material or different materials. A punch 730 can be positioned adjacent to the PE structure 710. In this embodiment, the punch 730 can also be positioned adjacent to a set of second supports 740.

[0113] Further to FIG. 7 , a force 750 can be applied to the PE structure 710 by a punch 730. The force 750 can be applied such that the punch 730 contacts the PE structure 710 and pushes or pulls the PE structure 710 into the first shaped support 720. As the PE structure 710 is pushed into the first shaped support 720, the PE structure 710 can conform to the shape 715 of the first shaped support 720. In this embodiment, the PE structure 710 conforms to the concave shape 715 of the first shaped support 720. In this embodiment, the PE structure 710 can stretch or expand when the force 750 is applied, such that the PE structure 710 stretches to conform to the concave shape 715. In some embodiments, a force can also be applied to the second support 740 to further shape the PE structure 710. In other embodiments, no force may be applied to the second support 740.

[0114] In some embodiments, heat can be applied to the PE structure 710 simultaneously with the application of force 750 to the PE structure. Heat can be applied at a temperature near the glass transition temperature of PE. This temperature can be about 130°C, about 110-130°C, about 130-150°C, or 150-180°C. In some embodiments, applying heat to the PE structure 710 can be performed while the PE structure 710 resides within the first mold support 720. In some embodiments, applying heat to the PE structure 710 densifies the PE structure. In some embodiments, the PE structure 710 can be uniformly densified. In other embodiments, the PE structure 710 can be densified, resulting in a density gradient throughout the PE structure 710.

[0115] Further to Figure 7, punch 730 can be released from PE structure 710 to form PE article 760. In some embodiments, the PE article can retain the shape 715 of first shaped support 720. In some embodiments, the PE article retains the density gradient formed in PE structure 710. In some embodiments, the PE article is a one-piece PE article. In some embodiments, the PE article is seamless. [Example]

[0116] Example 1 In a first example, three PE articles were heated to temperatures above their melting temperatures. First, second, and third PE articles 800, 802, and 804 comprised a first porous PE film. The three PE articles comprised expanded polyethylene (ePE), although similar concepts can be observed for other PE articles. First PE article 800 was heated to approximately 127°C, second PE article 802 was heated to approximately 130°C, and third PE article 804 was heated to approximately 133°C.

[0117] The first PE article 800, the second PE article 802, and the third PE article 804 were each formed into a tube and then heated. A mandrel was used to apply substantially uniform heat to each of the first, second, and third PE articles 800, 802, and 804, although other heating sources could be used. A constant pressure was maintained without the use of a vacuum while each of the first, second, and third PE articles 800, 802, and 804 was heated. A constant low pressure of approximately 2 psi was applied using an overlap.

[0118] FIG. 8A shows a first PE article 800 that has been heated to 127°C and then cooled. FIG. 8B shows a second PE article 802 that has been heated to 130°C and then cooled. As can be seen, as the processing temperature increases and exceeds the melting temperature, the PE article melts, or layers within the PE article melt, causing the material to shrink and densify. As shown, the second PE article 802 further exhibits a more densified or compacted material compared to the first PE article 800, with fewer visible layers and spaces within the PE article. The absence of visible layers or fewer spaces within the PE article is also indicative of a more integrated structure with reduced distinction between individual layers. Additionally, as shown, the second PE article 802 is reduced in thickness and more compact compared to the first PE article 800. The second PE article 802 also appears to be compacted or densified, with a compacted microstructure.

[0119] Turning to FIG. 9 , the thicknesses of the first, second, and third PE articles 800, 802, 804 were measured in microns (μm) after each article was heated. As the data shows, as the processing temperature increases above the melting temperature, the thickness of each article decreases. In other words, the thickness of the third PE article 804 is less than the thickness of the second PE article 802, which is less than the thickness of the first PE article 800. As discussed with respect to FIGS. 8A-8B , the decrease in thickness may correlate with densification and shrinkage of the PE articles, a tighter microstructure of the PE articles, and a more integrated structure.

[0120] Turning to FIG. 10 , the bubble points of the first, second, and third PE articles 800, 802, and 804 were measured in psi. As the data shows, as the processing temperature increases above the melting temperature, the bubble point of each article increases. The bubble point may correlate to the size of the pores present in the PE article. If the bubble point increases, this indicates that the pore size of the article is decreasing. In other words, the pore size of the third PE article 804 is smaller than the pore size of the second PE article 802, which is smaller than the pore size of the first PE article 800. As discussed with respect to FIGS. 8A-8B , an increase in bubble point may also correlate to densification and shrinkage of the PE article, a tighter microstructure of the PE article, and / or a more integrated structure.

[0121] Turning to FIG. 11 , the airflow, or air leak, through the PE articles was measured in liters per hour (l / hr) for the first, second, and third PE articles 800, 802, and 804. The airflow measurements were performed using an ATEQ® leak detection device. As the processing temperature increased above the melting temperature, the air leak for each article decreased. The air leak volume can be correlated to the pore size present in the PE article; larger pore sizes can allow more air to leak through the PE article. This indicates that the pore size for each article decreased as the processing temperature increased. In other words, the pore size of the third PE article 804 was smaller than the pore size of the second PE article 802, which in turn was smaller than the pore size of the first PE article 800. As discussed with respect to Figures 8A-8B, reduced air leaks may correlate with increased densification and shrinkage of the PE article, a tighter microstructure of the PE article, and / or a more integrated structure.

[0122] Furthermore, pore size can correspond to the ability of the article to selectively allow or reduce cell ingress, penetration, and / or adhesion within its structure. Smaller pore sizes allow the respective article to reduce or limit cell ingress, which may be desirable in some applications, including, but not limited to, aortic devices. Larger pore sizes allow the respective article to allow cell ingress. Thus, processing temperatures can be selected to increase or decrease pore size as desired, allowing or reducing cell growth.

[0123] Although the above examples are described with respect to tubular PE articles, flat PE articles and PE articles of other shapes may exhibit similar behavior and similar changes in material properties when heated above melting. Example 2

[0124] In the second example, three PE articles were heated to a temperature above melting. Fourth, fifth, and sixth PE articles 806, 808, and 810 included a second porous PE film that was different from the first porous PE film of the first example. Three of the PE articles included expanded polyethylene (ePE), although similar concepts can be observed in other PE articles. Fourth PE article 806 was heated to approximately 127°C, fifth PE article 808 was heated to approximately 130°C, and sixth PE article 810 was heated to approximately 133°C.

[0125] As in the first example, the fourth PE article 806, the fifth PE article 808, and the sixth PE article 810 were each formed into a tube before heating. A mandrel was used to apply substantially uniform heat to each of the fourth, fifth, and sixth PE articles 806, 808, and 810, although other heating sources could be used. A constant pressure was maintained without the use of a vacuum while heating each of the fourth, fifth, and sixth PE articles 806, 808, and 810. A constant low pressure of approximately 2 psi was applied using an overlap.

[0126] As in the first example, the thickness, bubble point, and air leak were measured for each of the fourth, fifth, and sixth PE articles 806, 808, and 810. The trends in material properties were similar to those observed in the first example. As shown in FIG. 9, as the processing temperature increased above the melting temperature, the thickness of each PE article decreased. As shown in FIG. 10, as the processing temperature increased above the melting temperature, the bubble point increased. As shown in FIG. 11, as the processing temperature increased above the melting temperature, the air leak of each article decreased. These results indicate that an increase in processing temperature may correlate with densification and shrinkage of the PE article, a tighter microstructure of the PE article, a decrease in pore size, and / or a more integrated structure. This also indicates that the densification, tighter microstructure, smaller pore size, and more integrated structure of each PE article with an increase in processing temperature are not limited to one type of porous ePE film, but can be observed in both the first and second porous ePE films.

[0127] Turning to FIG. 12 , peel strength was measured for each of the fourth, fifth, and sixth PE articles 806, 808, and 810. Peel strength was measured as the force required to peel the article approximately 12 mm and is reported in units of N / 12 mm. As the data shows, as the processing temperature increased above the melting temperature, the peel strength of each article increased. In other words, the force required to pull the third PE article 804 was greater than the force required to pull the second PE article 802, which in turn was greater than the force required to pull the first PE article 800. The increase in force may also correlate with densification and compression of the PE articles and / or a tighter microstructure of the PE articles. The increase in force required to pull the articles back indicates that as the processing temperature increases, layers and spaces within the PE articles decrease, potentially resulting in the formation of new bonds within the PE articles. The increase in tensile force also indicates that the PE article becomes more integrated as the processing temperature increases, as the layers within the article become less distinct and may be more difficult to separate.

[0128] Although the above examples are described with respect to tubular PE articles, flat PE articles and PE articles of other shapes may exhibit similar behavior and similar changes in material properties when heated above melting.

[0129] While specific embodiments are provided herein, it is understood that different configurations and material properties can be selected and processed within the spirit of this disclosure. Additionally, specific embodiments provide for temperatures, processes, and properties that can be varied while still falling within the spirit of this disclosure.

[0130] The disclosure of this application has been described above both generically and with reference to specific embodiments. It will be apparent to those skilled in the art that various modifications and changes may be made to the embodiments without departing from the scope of the present disclosure. Accordingly, it is intended that the embodiments encompass modifications and variations of the present disclosure and their equivalents, provided they fall within the scope of the appended claims.

Claims

1. 1. A method of forming a polyethylene (PE) article, the method comprising: assembling a plurality of polyethylene substrates on a first support, wherein the plurality of polyethylene substrates define a PE structure; applying a second support to the PE structure to position the PE structure between the first support and the second support; placing the first support, the PE structure, and the second support adjacent a housing; applying a force to the first support, the second support, and the PE structure, causing the first support, the second support, and the PE structure to expand to fit into the housing; Including, The method, wherein the housing restricts the first support, the second support, and the PE structure from expanding beyond the housing, thereby forming a PE article as the PE structure expands.

2. 10. The method of claim 1, wherein applying said force to said PE structure results in a monolithic PE article.

3. The method of claim 2, wherein the one-piece PE article is seamless.

4. The method of claim 1 , wherein the method further comprises placing the first support, the second support, and the PE structure around a mandrel.

5. The method of claim 3 wherein the mandrel is porous or perforated.

6. The method of claim 1 , wherein the first substrate and the second substrate are formed of silicone.

7. 2. The method of claim 1, wherein the step of assembling the plurality of polyethylene members further comprises the step of assembling other members formed of a material other than PE, including at least one of expanded polyethylene, polytetrafluoroethylene, or expanded polytetrafluoroethylene.

8. The method of claim 1 further comprising the step of heating the PE structure.

9. 2. The method of claim 1, wherein applying a force to the first support, the second support, and the PE structure includes heating a liquid disposed within a mandrel to about 130°C, causing the liquid phase to transition to a gas, and applying the force with the gas.

10. 9. The method of claim 8, wherein heating the liquid to a gas results in a liquid to gas expansion ratio of about 1:1600.

11. The method of claim 1 , wherein applying a force to the first support, the second support, and the PE structure comprises releasing a compressed gas.

12. 1. A method for forming a one-piece polyethylene (PE) article, the method comprising: placing a PE structure such that a first portion of the PE structure overlaps a second portion of the PE structure; applying heat to the PE structure; applying heat to the PE structure and simultaneously expanding the PE structure; A method comprising:

13. 13. The method of claim 12, wherein the step of disposing the PE structure comprises disposing the PE structure between a first silicone support and a second silicone support.

14. 14. The method of claim 13, wherein expanding the PE structure comprises applying a force to one of the first silicone support and the second silicone support such that the first silicone support, the PE structure, and the second silicone support expand together.

15. The method of claim 14 , wherein expanding the PE structure comprises applying the force by pressure.

16. 16. The method of claim 15, wherein the pressure is provided by a heated liquid transitioning to a gas.

17. The method of claim 15 wherein the pressure is provided by compressed gas.

18. 15. The method of claim 14, wherein the step of simultaneously applying heat and expanding the PE structure forms a seamless, integral PE article.

19. 1. A method of forming a polyethylene (PE) article, the method comprising: Assembling a PE structure on a first molded support; positioning a punch adjacent to the PE structure; applying a force to the PE structure with the punch so that the punch contacts the PE structure and presses it into the first shaped support, whereby the PE structure conforms to the shape of the first shaped support; applying heat to the PE structure; releasing the punch from the PE structure to form the PE article, wherein the PE article retains the shape of the first shaped support; A method comprising:

20. 20. The method of claim 19, wherein applying heat to the PE structure comprises applying heat at about 130°C.

21. 20. The method of claim 19, wherein the step of applying heat to the PE structure densifies the PE article, and the density has a gradient throughout the PE article.

22. 20. The method of claim 19, wherein the steps of applying a force to the punch and applying heat to the PE structure are performed simultaneously.

23. 20. The method of claim 19, wherein the step of applying heat to the PE structure is performed while the PE structure resides within the first molded support.

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