Sample processing device with resealable process chamber

[0001] The present application is a continuation-in-part of U.S. patent application Ser. No. 09/894,810, filed on Jun. 28, 2001, titled ENHANCED SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS (Attorney Docket No. 55266USA7A.002) and a continuation-in-part of U.S. patent application Ser. No. 09/847,467, filed on May 2, 2001, titled CONTROLLED-PUNCTURE FILMS (Attorney Docket No. 56322USA6A), both of which are hereby incorporated by reference in their respective entireties.

[0002] The present invention relates to devices, methods and systems for processing of sample materials, such as methods used to amplify genetic materials, etc.

[0003] Many different chemical, biochemical, and other reactions are sensitive to temperature variations. Examples of thermal processes in the area of genetic amplification include, but are not limited to, Polymerase Chain Reaction (PCR), Sanger sequencing, etc. The reactions may be enhanced or inhibited based on the temperatures of the materials involved. Although it may be possible to process samples individually and obtain accurate sample-to-sample results, individual processing can be time-consuming and expensive.

[0004] A variety of sample processing devices have been developed to assist in the reactions described above. A problem common to many of such devices is that it is desirable to seal the chambers or wells in which the reactions occur to prevent, e.g., contamination of the reaction before, during, and after it is completed.

[0005] Yet another problem that may be experienced in many of these approaches is that the volume of sample material may be limited and/or the cost of the reagents to be used in connection with the sample materials may also be limited and/or expensive. As a result, there is a desire to use small volumes of sample materials and associated reagents. When using small volumes of these materials, however, additional problems related to the loss of sample material and/or reagent volume through vaporization, etc. may be experienced as the sample materials are, e.g., thermally cycled.

[0006] The present invention provides devices including resealable film used to close one or more process chambers in a sample processing device. The resealable films preferably provide for controlled puncture, followed by resealing of the puncture site such that the process chamber remains substantially isolated from the surrounding environment. The present invention also provides methods for delivering sample materials to a process chamber through a resealable membrane, as well as removal of materials from a process chamber through a membrane.

[0007] In those embodiments that include connected process chambers in which different processes may be sequentially performed on a starting sample, the present invention may provide an integrated solution to the need for obtaining a desired finished product from a starting sample even though multiple processes are required to obtain the finished product.

[0008] In other embodiments in which the process chambers are multiplexed from a loading chamber (in which the starting sample is loaded), it may be possible to obtain multiple finished samples from a single starting sample. Those multiple finished samples may be the same materials where the multiplexed process chambers are designed to provide the same finished samples. Alternatively, the multiple finished samples may be different samples that are obtained from a single starting sample.

[0009] As used herein, elongation at break of the film refers to the tensile strain at break as determined by ASTM standard D822.

[0010] As used herein, film refers to a flexible article having any shape that has two major surfaces, e.g., sheet or tube. Optionally the film has more than one layer. The film may preferably have, e.g., a total thickness of no more than about 400 micrometers (0.016 inches), more preferably no more than about 250 micrometers (0.010 inches) depending on the materials and construction used.

[0011] As used herein, flexural rigidity of the film refers to the product of the modulus of elasticity and moment of inertia of a film.

[0012] As used herein, load refers to the mechanical force that is applied to a body.

[0013] As used herein, modulus of elasticity of the film refers to the amount of force necessary to deform the film one strain unit.

[0014] As used herein, moment of inertia of the film refers to the geometric stiffness of the film (i.e., the cube of the thickness divided by 12).

[0015] As used herein puncturability refers to the displacement to break when the load of a probe is applied to a film.

[0016] As used herein, rescalability refers to the ability of a film to reduce the size of an opening in the film at a puncture site up to the point of completely closing the puncture site. In embodiments where resealability is desired, preferably, an opening that is created in the film by a puncturing object reseals such that the circumference of the opening is less than 50% of the circumference of the puncturing object. More preferably, the opening will decrease to less than 20% of the circumference of the puncturing object.

[0017] As used herein, sealability refers to the ability of a film to form a seal around a puncturing object while it is puncturing the film.

[0018] As used herein, recovering stress of the film refers to the difference between the film's tensile stress at 300% elongation as determined by ASTM standard D822 and the stress when the film is returned to its original length after stretching to 300% elongation.

[0019] As used herein, surface friction between the film and a puncturing object refers to the linear coefficient expressing the tangential force to pull a sled covered with that film over a track consisting of the material of the puncturing object compared to the normal force (weight) of the sled.

[0020] In one aspect, the present invention provides a sample processing device including a body with at least one process chamber having a process chamber volume; resealable film attached to the body, the resealable film having an internal surface defining a portion of the process chamber volume and an external surface facing away from the process chamber volume; and friction modifying material on the external surface of the resealable film or friction modifying material incorporated into the resealable film, wherein the incorporated friction modifying material is chosen because it substantially migrates to the external surface of the resealable film.

[0021] In another aspect, the present invention provides a sample processing device including a body with at least one process chamber having a process chamber volume; resealable film attached to the body, the resealable film having an internal surface defining a portion of the process chamber volume and an external surface facing away from the process chamber volume, wherein the resealable film includes plastic material forming a first layer and elastomeric material forming a second layer attached to the first layer.

[0022] In another aspect, the present invention provides a method of manufacturing a sample processing device, the method including providing a body that includes at least one process chamber with a process chamber volume; attaching resealable film to the body, wherein the resealable film has an internal surface defining a portion of the process chamber volume and an external surface facing away from the process chamber volume; providing friction modifying material on the external surface of the resealable film to provide a targeted level of at least one of: the friction between the resealable film and a puncturing object, the flexural rigidity of the resealable film, the recovering stress of the resealable film, and the elongation at break of the resealable film.

[0023] In another aspect, the present invention provides a method of manufacturing a sample processing device by providing a body having at least one process chamber with a process chamber volume; attaching resealable film to the body, wherein the resealable film has an internal surface defining a portion of the process chamber volume and an external surface facing away from the process chamber volume; providing friction modifying material incorporated into the resealable film, wherein the incorporated friction modifying material is chosen because it substantially migrates to the external surface of the resealable film to provide a targeted level of at least one of: the friction between the resealable film and a puncturing object, the flexural rigidity of the resealable film, the recovering stress of the resealable film, and the elongation at break of the resealable film.

[0024] In another aspect, the present invention provides a method of transferring sample material by providing a sample processing device including a body with at least one process chamber having a process chamber volume; resealable film attached to the body, the resealable film having an internal surface defining a portion of the process chamber volume and an external surface facing away from the process chamber volume. The method further includes puncturing the resealable film with a fluid transfer device to form an opening in the resealable film; inserting the fluid transfer device through the opening in the resealable film, wherein a portion of the fluid transfer device is located within the process chamber volume; transferring sample material into or out of the process chamber using the fluid transfer device; and removing the fluid transfer device from the process chamber, wherein the resealable film reseals the opening after removal of the fluid transfer device.

[0025] These and other features and advantages of the devices, systems and methods of the invention are described below with respect to illustrative embodiments of the invention.

[0026] FIG. 1 is a top plan view of one device according to the present invention.

[0027] FIG. 2 is an enlarged partial cross-sectional view of a process chamber in the device of FIG. 1.

[0028] FIG. 3 is an enlarged partial cross-sectional view of the process chamber with a fluid transfer device inserted into the process chamber through a resealable film.

[0029] FIG. 4 is an enlarged partial cross-sectional view of the process chamber after removal of the fluid transfer device from the process chamber.

[0030] FIG. 5 depicts an apparatus used to drive a puncturing object into a film and measure the flexure at rupture or break of the film.

[0031] The present invention provides a device that can be used in methods that involve thermal processing, e.g., sensitive chemical processes such as PCR amplification, ligase chain reaction (LCR), self-sustaining sequence replication, enzyme kinetic studies, homogeneous ligand binding assays, and more complex biochemical or other processes that require precise thermal control and/or rapid thermal variations.

[0032] Although one illustrative embodiment of a device is described below, sample processing devices according to the principles of the present invention may be manufactured according to the principles described in U.S. Provisional Patent Application Serial No. 60/214,508 filed on Jun. 28, 2000 and titled THERMAL PROCESSING DEVICES AND METHODS (Attorney Docket No. 55265USA19.003); U.S. Provisional Patent Application Serial No. 60/214,642 filed on Jun. 28, 2000 and titled SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS (Attorney Docket No. 55266USA99.003); U.S. Provisional Patent Application Serial No. 60/237,072 filed on Oct. 2, 2000 and titled SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS (Attorney Docket No. 56047USA29); and U.S. Provisional Patent Application Serial No. 60/284,637 filed on Apr. 18, 2001 and titled ENHANCED SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS (Attorney Docket No. 56546USA49.002). Other potential device constructions may be found in, e.g., U.S. patent application Ser. No. 09/710,184 filed on Nov. 10, 2000 and titled CENTRIFUGAL FILLING OF SAMPLE PROCESSING DEVICES (Attorney Docket No. 55265USA9A) and U.S. Provisional Patent Application Serial No. 60/260,063 filed on Jan. 6, 2001 and titled SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS (Attorney Docket No. 56284USA19.002). Still other constructions may be described in U.S. patent application Ser. No. 09/894,810, filed on Jun. 28, 2001, titled ENHANCED SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS (Attorney Docket No. 55266USA7A.002).

[0033] Although relative positional terms such as top and bottom may be used in connection with the present invention, it should be understood that those terms are used in their relative sense only. For example, when used in connection with the devices of the present invention, top and bottom are used to signify opposing sides of the devices. In actual use, elements described as top or bottom may be found in any orientation or location and should not be considered as limiting the methods, systems, and devices to any particular orientation or location. For example, the top surface of the device may actually be located below the bottom surface of the device in use (although it would still be found on the opposite side of the device from the bottom surface).

[0034] One illustrative device manufactured according to the principles of the present invention is depicted in FIGS. 1 and 2. The device 10 may be in the shape of a circular disc as illustrated in FIG. 1, although any other shape could be used. The depicted device 10 includes a plurality of process chambers 50, each of which defines a volume for containing a sample and any other materials that are to be processed with the sample.

[0035] The illustrated device 10 includes ninety-six process chambers 50, although it will be understood that the exact number of process chambers provided in connection with a device -manufactured according to the present invention may be greater than or less than ninety-six, as desired.

[0036] The process chambers 50 in the illustrative device 10 are in the form of chambers, although the process chambers in devices of the present invention may be provided in the form of capillaries, passageways, channels, grooves, or any other suitably defined volume.

[0037] Although the depicted device relies on centrifugal forces and distribution channels to move materials into the various process chambers, it should be understood that any sample processing device used in connection with the present may or may not include distribution channels or other fluid movement structures. Rather, the sample processing devices of the present invention may include a number of completely isolated and separate process chambers into which materials are delivered and from which materials are removed independent of the other process chambers. For example, the present invention may include conventional microtiter plates and other sample processing devices including one or more independent, isolated process chambers.

[0038] The device 10 of FIGS. 1 and 2 is a multi-layered composite structure including a substrate 20, first layer 30, and a resealable film 40. It is preferred that the substrate 20, first layer 30 and resealable film 40 of the device 10 be attached or bonded together with sufficient strength to resist any expansive forces that may develop within the process chambers 50 as, e.g., the constituents located therein are rapidly heated during thermal processing. The robustness of the bonds between the components may be particularly important if the device 10 is to be used for thermal cycling processes, e.g., PCR amplification. The repetitive heating and cooling involved in such thermal cycling may pose more severe demands on the bond between the sides of the device 10. Another potential issue addressed by a more robust bond between the components is any difference in the coefficients of thermal expansion of the different materials used to manufacture the components.

[0039] The process chambers 50 in the depicted device 10 are in fluid communication with distribution channels 60 that, together with loading chamber 62, provide a distribution system for distributing samples to the process chambers 50. Introduction of samples into the device 10 through the loading chamber 62 may be accomplished by rotating the device 10 about a central axis of rotation such that the sample materials are moved outwardly due to centrifugal forces generated during rotation. Before the device 10 is rotated, the sample can be introduced into the loading chamber 62 for delivery to the process chambers 50 through distribution channels 60. The process chambers 50 and/or distribution channels 60 may include ports through which air can escape and/or other features to assist in distribution of the sample materials to the process chambers 50. Alternatively, sample materials could be loaded into the process chambers 50 under the assistance of vacuum or pressure.

[0040] The illustrated device 10 includes a loading chamber 62 with two subchambers 64 that are isolated from each other. As a result, a different sample can be introduced into each subchamber 64 for loading into the process chambers 50 that are in fluid communication with the respective subchamber 64 of the loading chamber 62 through distribution channels 60. It will be understood that the loading chamber 62 may contain only one chamber or that any desired number of subchambers 64, i.e., two or more subchambers 64, could be provided in connection with the device 10.

[0041] FIG. 2 is an enlarged cross-sectional view of a portion of the device 10 including one of the process chambers 50. The substrate 20 includes a first major side 22 and a second major side 24. Each of the process chambers 50 is formed, at least in part in this embodiment, by a void 26 formed through the substrate 20. The illustrated void 26 is formed through the first and second major sides 22 and 24 of the substrate 20.

[0042] The substrate 20 may preferably be polymeric, but may be made of other materials such as glass, silicon, quartz, ceramics, etc. Furthermore, although the substrate 20 is depicted as a homogenous, one-piece integral body, it may alternatively be provided as a non-homogenous body of, e.g., layers of the same or different materials. For those devices 10 in which the substrate 20 will be in direct contact with the sample materials, it may be preferred that the material or materials used for the substrate 20 be non-reactive with the sample materials. Examples of some suitable polymeric materials that could be used for the substrate in many different bioanalytical applications may include, but are not limited to, polycarbonate, polypropylene (e.g., isotactic polypropylene), polyethylene, polyester, etc.

[0043] A first layer 30 is provided on one side of the substrate 20 in the illustrated embodiment. Although the first layer 30 is depicted as a homogenous, one-piece integral layer, it may alternatively be provided as a non-homogenous layer of, e.g., sub-layers of the same or different materials, e.g., polymeric materials, metallic layers, etc. Also, in some embodiments, the process chamber 50 may be formed as a depression in the substrate 20 with no first layer 30 required to define the volume of the process chamber 50.

[0044] A resealable film 40 is provided on the opposite side of the substrate 20 to define the remainder of the volume of the process chamber 50. Although the resealable film 40 is depicted as a homogenous, one-piece integral layer, it may alternatively be provided as a non-homogenous layer of, e.g., sub-layers of the same or different materials, e.g., polymeric materials, etc. The resealable film 40 includes an external surface 42 facing away from the volume of the process chamber 50 and an internal surface 44 facing the volume of the process chamber 50.

[0045] It may be preferred that at least a portion of the materials defining the volume of the process chamber 50 be transmissive to electromagnetic energy of selected wavelengths. In the depicted device 10, if the body 20, first layer 30, and/or resealable film 40 may be transmissive to electromagnetic energy of selected wavelengths.

[0046] The selected wavelengths may be determined by a variety of factors, for example, electromagnetic energy designed to heat and/or interrogate a sample in the process chamber 50, electromagnetic energy emitted by the sample (e.g., fluorescence), etc. By providing a transmissive process chamber 50, a sample in the chamber can be interrogated by electromagnetic energy of selected wavelengths (if desired) and/or electromagnetic energy of the selected wavelengths emanating from the sample can be transmitted out of the process chamber 50 where it can be detected by suitable techniques and equipment. For example, electromagnetic energy may be emitted spontaneously or in response to external excitation. A transmissive process chamber 50 may also be monitored using other detection techniques, such as color changes or other indicators of activity or changes within the process chambers 50.

[0047] In some instances, however, it may be desirable to prevent the transmission of selected wavelengths of electromagnetic energy into the process chambers. For example, it may be preferred to prevent the transmission of electromagnetic energy in the ultraviolet spectrum into the process chamber where that energy may adversely impact any reagents, sample materials, etc. located within the process chamber.

[0048] Also depicted in FIG. 2 is sample material 52 located within the volume of the process chamber 50. The sample material may include at least one fluid component, preferably a liquid. Furthermore, the sample material may be a biological sample material.

[0049] FIG. 3 is an enlarged partial cross-sectional view of the process chamber of FIG. 2 after insertion of a fluid transfer device 70 into the volume of the process chamber 50 through the resealable film 40. The fluid transfer device 70 may be, e.g., a pipette, needle, or other device capable of taking up and/or delivering fluids. In addition, the fluid transfer device 70 may preferably have sufficient structural rigidity to pierce the resealable film 40 by itself. Alternatively, the fluid transfer device 70 may be inserted through an opening already pierced by another instrument. The fluid transfer device 70 may have a sharp tip 72 as shown or the tip may be blunt depending on the properties of the resealable film 40 and the fluid transfer device itself.

[0050] FIG. 4 is an enlarged partial cross-sectional view of the process chamber of FIGS. 2 & 3 after removal of the fluid transfer device 70 from the volume of the process chamber 50. In the depicted embodiment, a portion of the sample material 52 in the process chamber 50 has been removed using the fluid transfer device 70 (although as discussed above, the fluid transfer device 70 may also deliver materials into the process chamber 50).

[0051] The opening 46 through which the fluid transfer device 70 entered and exited the process chamber includes an perforation in the resealable film 40 that reseals upon removal of the fluid transfer device 70. While the materials used for resealable film 40 exhibit resealability of the opening 46 upon removal of a fluid transfer device as depicted in FIG. 4, the resealable film 40 may also preferably exhibit sealability when the fluid transfer device 70 is inserted through the layer 40.

[0052] The resealable film 40 may be attached to the body 20 around at least the boundaries of the process chamber 50 to seal the sample materials 52 therein. Any suitable technique or combination of techniques may be used to attach the resealable film 40 to the body 20. Examples of some suitable attachment techniques include, but are not limited to, adhesives (e.g., pressure sensitive, hot-melt, curable, etc.), thermal welding, ultrasonic welding, heat sealing, chemical welding, clamping, mechanical fasteners, etc.

[0053] The resealable film 40 may preferably be a polymeric film, preferably a polymeric film that can be controllably punctured and optionally sealed and/or resealed. Typically, these properties are determined by at least one of flexural lo rigidity of the film, the elongation at break of the film, the recovering stress of the film, and friction between the film and a puncturing object.

[0054] Control over puncturability in a resealable film 40 can be accomplished by modifying a surface of the film to provide desired levels of flexural rigidity of the film, the elongation at break of the film, the recovering stress of the film, and surface friction between the film and the puncturing object, e.g., a fluid transfer device 70.

[0055] Modifying the surface can be accomplished by a number of methods. For example, it can include changing the modulus of the film by altering the temperature of the film prior to, and during, the penetration by a puncturing object; stretching and optionally releasing the film prior to penetration by a puncturing object; applying a modifying material to the surface of the film; or adding a modifying material to the bulk material comprising a film. For multi-layer films, modifying can also include changing the thickness of one or more layers or changing the properties of the surface layer that first contacts a puncturing object.

[0056] Another option is to modify the coefficient of friction between the puncturing object and the film (hereafter COF) to control the puncture resistance of the films. A puncturing object and flexible film generally interact as follows: as the puncturing object makes contact with the film, the film deforms in the direction of the puncturing object's motion. This is accompanied by local stretching of the film in the vicinity of the puncturing object's tip.

[0057] As the film stretches, the elasticity of the film's materials requires the film construction to exert a hoop (compressive radially inward) stress on the puncturing object. This force is exerted nearly normal to the lateral surface of the puncturing object. Simultaneously, there is a tangential, or surface, force associated with driving the puncturing object downward and perpendicular to the force exerted by the hoop stress of the film.

[0058] If the COF is high (i.e., the puncturing object adheres to the film surface) the tangential stress associated with driving the puncturing object down into the film will not be great enough to overcome the normal force from the film hoop stress holding the film against the puncturing object (i.e., the product of the COF and the normal force is greater than the tangential force). Thus, the puncturing object will pull the surrounding film downward with it such that the force exerted by the object will be distributed over the entire film surface in contact with the object.

[0059] Because the film in contact with the puncturing object does not experience a stress large enough to cause mechanical failure, the portion of the film not in contact with the puncturing object will also be strained as the film in contact with the object is pulled with the movement of the puncturing object. This deformation of the non-contacting film will effectively distribute the load of the puncturing object so that mechanical failure will only be caused at much larger displacements, i.e., large film deformations.

[0060] Conversely, if the COF is low, the tangential force from the puncturing object will overcome the normal force and the object will slip against the film surface. This will allow the load of the puncturing object to be concentrated entirely at its tip thus causing greater distortion of the film material underneath the object's tip until the object punctures (i.e., mechanically ruptures) the film. Thus, one may control the ease of puncture in flexible films by controlling the COF.

[0061] Additionally, changing the moment of inertia of a film can control puncture in films. A stiff film is more easily punctured than a flexible film. As has been explained, as a puncturing object makes contact with a film, the area immediately underneath the puncturing object undergoes distortion and stretching. This causes the film to exert a hoop stress inward to make contact (or conform around) the puncturing object.

[0062] However, this ability to make contact around the puncturing object depends on the ability of the film itself to conform to the object. For example, with a three-layered film of an elastomeric core layer and relatively rigid outer layers, as the film is stretched under the tip of the puncturing object, the elastomeric core layer exerts a force generated by the tendency of the film to recover from the hoop stress to drive the film toward contact with the object. If the outer layer is not rigid (due to small moment of inertia, or low modulus of elasticity of the film) in comparison to the core layer then the core layer material can drive the entire film to contact the puncturing object. However, if the outer layer is thick or stiff, then the core layer will be less able to force the entire film to conform to the puncturing object. The extent of the ability of the film to conform to the puncturing object also controls puncture resistance. If the film cannot conform to the puncturing object surface then the object will be able to concentrate its entire load immediately below its tip regardless of the COF. Conversely, if the film can conform to the puncturing object 25 surface then puncture may be impeded, if the COF is sufficiently high.

[0063] When films having at least two layers are used in connection with the present invention, changing the recovering stress of the layer that is not first contacted by a puncturing object influences puncturability because it is this force that drives the contact of the surface of the film with the puncturing object. The surface of a material with a lower recovery stress will be less driven to contact the puncturing object, thereby allowing puncture to occur more easily.

[0064] The puncture resistance of some film constructions can be affected by the recovery stress of the film even when the elongation at break of each of the layers of the film is substantially unchanged.

[0065] The films of the present invention preferably include elastomeric layers in a manner that results in a resealable film. As was discussed in regard to puncture resistance, elastomeric films exert high hoop stresses, i.e., recovering forces from cylindrical deformation, (because they try to return to their original, unstressed state). It is this inward (toward the puncturing object) force that facilitates resealing. The tendency of less elastic films to generate the restoring force to reseal or recover strain in response to deformation is greatly reduced in comparison to elastomeric films.

[0066] It has been found that there is a correlation between case of puncture and the ability of the film to reseal. If the film punctures easily, then only the perimeter of a relatively small area of the film (the area in contact with the tip of the puncturing object) is stretched to break. Depending on the size of the puncturing object, this can be a relatively small area and the resulting opening will be small. However, if the film is puncture-resistant, the ability of the film to conform to the puncturing object will be increased such that the area of the film in contact with the puncturing object will cover not only the object's tip but also at least some of the lateral surfaces of the object. Accordingly, the perimeter of the area that is stressed to break will include at least the portion of film in contact with the lateral surface of the object.

[0067] Thus, for films with high COFs, the opening (the area within the broken perimeter) is relatively large and the film is less able to reseal the opening depending on the size and shape of the puncturing object. Thus, the resealability of openings in the films may be controlled in tandem with (though not independent of) the puncture resistance of the films.

[0068] Elastomeric layers also contribute to the ability of a film to seal around a puncturing object. The elastic recovery of a film also allows the film to conform to the shape of the puncturing object. This sealability property is advantageous when it is desirable to isolate a process chamber from a surrounding environment while a film is being punctured. For example, sealability allows a film to be punctured without allowing contaminants or other materials to pass through the puncture site.

[0069] In one embodiment, the resealable is a polymeric multilayer film of two outer layers and at least one inner layer. Modifying such a multilayer film can involve modifying at least one of the outer layers of the film to provide a targeted level of at least one of flexural rigidity of the film, the elongation at break of the film, the recovering stress of the film, and the friction between the film and a puncturing object. For example, the thickness and/or stiffness of an outer layer can be changed to make an overall change in the thickness or stiffness of a film. Alternatively, modifying such a multilayer film can involve modifying an inner layer of the film to provide a targeted level of flexural rigidity of the film and elongation at break of the film.

[0070] In general, films having an (AB)_nA (where n is greater than 1) construction can be more flexible than films of equal thickness having an ABA construction. This occurs, for example, when the A layer is a hard stiff material and the B material is a soft, pliable material. When a film is flexed the material at one surface is compressed and the material at the opposing surface is stretched. The material in the middle of the film is not significantly compressed or stretched. If the stiff material is at or near the film's surface and the soft material is near the film's center, stretching the film requires more force than if the stiff material were near the film's center and the soft material were at the surfaces.

[0071] However, in a film having, e.g., an ABABABA structure with the same relative amounts of A and B as an ABA film of equal thickness, some of the soft material has been moved out toward the surfaces where the stretching and compression occur during flexing, and some of the stiff material has been moved toward the center of the film where there is minimal stretching and compression. This structure makes it easier to bend the film because less of the stiff material needs to be stretched or compressed.

[0072] Nevertheless, if you pull the film in tension (parallel to the layers) the stiffness of the film should be the same as for the ABA film because the same amount of A and B material is in cross section.

[0073] In one embodiment of the present invention, controlling the puncturability, resealability, and, optionally, sealability of a puncture site in a polymeric film can be accomplished by producing a polymeric film having at least two layers wherein a first layer includes a plastic material and a second layer includes an elastomeric material. In this embodiment, the type and amount of materials of the first layer and second layer are selected to impart specified levels of flexural rigidity of the film, the elongation at break of the film, the recovering stress of the film, and friction between the film and a puncturing object.

[0074] In another embodiment, controlling the puncturability, resealability, and, optionally, sealability of a puncture site in a polymeric film can be accomplished by: selecting a polymeric material and a modifying material; combining the polymeric material and the modifying material to form a molten mixture; and forming the molten mixture into a film; wherein the type, and amount of polymeric and modifying materials 0 are selected to provide a targeted level of at least one of flexural rigidity of the film, the elongation at break of the film, the recovering stress of the film, and the friction between the film and a puncturing object.

[0075] Whether it is applied to a surface of a polymeric film or mixed into the polymeric film, the modifying material can be a variety of materials able to change at least one of flexural rigidity of the film, the elongation at break of the film, the recovering stress of the film, or the friction between the film and puncturing object, such as a lubricant, an adhesive, or other monomers, oligomers, or polymers. Examples of modifying materials that can enhance puncturability include silicone oil and a wide variety of thermoplastic materials having a low COF relative to the puncturing object.

[0076] For example, a high density polyethylene film would be an appropriate puncturable film if the puncturing object were a polypropylene needle. Examples of modifying materials that enhance puncture resistance are elastomers resulting in relatively high COFs such as, for example, tackified elastomers or self-tacky elastomers. The modifying material may be selected for its ability to slide against a specific puncturing object, thereby contributing to the resealability of the puncture site by causing a small diameter opening to be formed. The more puncturable a film is, the better it is able to reseal because the force and effect of the puncturing object is concentrated in a small area.

[0077] As mentioned above, the polymeric film can include one or more layers. For example, the polymeric film can include three layerstwo outer layers and a core layer. In such a three-layer construction, the desired degree of puncture resistance and ability to seal and reseal can be affected by adjusting the properties of the film's core layers or at least one of the film's outer layers rigidity.

[0078] Plastic materials suitable for use in the present invention include those that are capable of being formed into a film layer, have a modulus of elasticity over 108 Pa, and cannot sustain more than 20% strain without incurring permanent set (i.e., permanent deformation) at ambient temperature. Examples of suitable plastic materials include thermoplastics such as polyethylenes (high density, low density, and very low density), polypropylene, polymethylmethacrylate, polyethylene terephthalate, polyamides, and polystyrene; thermosets such as dyglycidyl esters of bisphenol A epoxy resins, lo bisphenol A dicyanate esters, orthophthalic unsaturated polyesters, bisphenol A vinyl esters.

[0079] Elastomeric materials suitable for use in the present invention can include any material that is capable of being formed into a thin film layer and exhibits elastomeric properties at ambient conditions. Elastomeric means that the material will substantially resume its original shape after being stretched. Further, preferably, the elastomer will sustain only small permanent set following deformation and relaxation which set is preferably less than 20% and preferably less than 10% at moderate elongation, e.g., about 400-500%. Generally any elastomer is acceptable which is capable of being stretched to a degree that causes relatively consistent permanent deformation in a plastic outer layer. This can be as low as 50% elongation. Preferably, however the elastomer is capable of undergoing up to 300 to 1200% elongation at room temperature, and most preferably 600 to 800% elongation at room temperature. The elastomer can be pure elastomer or blends with an elastomeric phase or content that will exhibit substantial elastomeric properties at room temperature.

[0080] Examples of suitable elastomeric materials include natural or synthetic rubbers block copolymers that are elastomeric, such as those known to those skilled in the art as A-B or A-B-A block copolymers. Such copolymers are described for example on U.S. Pat. Nos. 3,265,765; 3,562,356; 3,700,633; 4,116,917, and 4,156,673. Useful elastomeric compositions include, for example, styrene/isoprene/styrene (SIS) block 30 copolymers, elastomeric polyurethanes, ethylene copolymers such as ethylene vinyl acetates, ethylene/propylene monomer copolymer elastomers or ethylene/propylene/diene terpolymer elastomers. Blends of these elastomers with each other or with modifying non-elastomers are also contemplated. For example, up to 50 weight %, but preferably less than 30 weight %, of polymers can be added as stiffening aids such as polyvinylstyrenes such as polyalphamethyl styrene, polyesters, epoxies, 5 polyolefins, e.g., polyethylene or certain ethylene/vinyl acetates, preferably those of higher molecular weight, or coumarone-indene resin.

[0081] In a multi-layer film, the plastic layer can be an outer or inner layer (e.g., sandwiched between two elastomeric layers). In either case, it will modify the elastic properties of the multilayer film.

[0082] Recovery of a multilayer film after puncture will depend on a number of factors such as the nature of the elastomeric layer, the nature of the plastic layer, the manner in which the film is stretched, and the relative thickness of the elastomeric and plastic layers. Percent recovery (with no load is on the film) refers to stretched length minus the recovered length, the sum of which is divided by the original length.

[0083] Generally, the plastic layer will hinder the elastic force with a counteracting resisting force. A plastic outer layer will not stretch with an inner elastomeric layer after the film has been stretched (provided that the second stretching is less than the first), the plastic outer layer will just unfold into a rigid sheet. This reinforces the core layer, resisting or hindering the contraction of the elastomeric core layer.

[0084] For obtaining a more puncturable film, the friction between a puncturing object and the surface of the film should be reduced. A wide variety of mechanisms can be used to reduce this friction as long as there is a concentration of stress at the point of load applied by the object. This can include applying a modifying material to the film surface or selecting a different material for the outer surface of the film such that the coefficient of friction between the puncturing object and film surface is reduced. For example, a polypropylene/styrene-isoprene synthetic rubber/polypropylene multi layer film can be made more puncturable by a polypropylene tip if the film surface is sprayed with silicone oil.

[0085] Puncturability may be increased by stretching a film. Holding a film in a 30 stretched position can make it more puncturable because it is less able to conform to the puncturing object.

[0086] In contrast, stretching and releasing a multilayer film comprising both elastomeric and plastic layers can decrease puncturability by decreasing the film's flexural rigidity. This can be done by stretching the multilayer film past the elastic limit of the plastic layer(s). Stretching and releasing can also lower a multilayer film's s coefficient of friction and modulus of elasticity. In some embodiments, the plastic layer can function to permit controlled release or recovery of the stretched elastomeric layer, modify the modulus of elasticity of the multilayer film and/or stabilize the shape of the multilayer film.

[0087] The present invention provides polymeric films, including single films with a modified surface, having varying degrees of puncturability, resealability, and, optionally varying degrees of sealability with regard to the shape of a specific type of puncturing object, e.g., a fluid transfer device. In one embodiment, the film can be punctured when the film is stretched to a given displacement by a puncturing object applied to a first major surface, but the film cannot be punctured when the film is stretched to the same displacement by the same puncturing object applied to a second opposing major surface. For example a two-layer film having a low COF on the first major surface and a high COF on the second would be more easily punctured by a puncturing object through the first surface than through the second surface. Of course, the shape of the tip of a puncturing object can also affect the puncturability of the film.

[0088] The single layer films of the present invention may be made by extrusion methods or any other suitable methods known in the art.

[0089] The multilayer films of the present invention may be formed by any convenient layer forming process such as coating, lamination, coextruding layers or stepwise extrusion of layers, but coextrusion is preferred. Coextrusion per se is know and is described, for example, in U.S. Pat. Nos. 3,557,265 and 3,479,425. The layers are typically coextruded through a specialized feedblock or a specialized die that will bring the diverse materials into contact while forming the film.

[0090] Coextrusion may be carried out with multilayer feedblocks or dies, for example, a three-layer feedblock (fed to a die) or a three-layer die such as those made by Cloeren 30 Co., Orange, Tex. A suitable feedblock is described in U.S. Pat. No. 4,152,387. Typically streams of materials flowing out of extruders at different viscosities are separately introduced into the feedblock and converge to form a film. A suitable die is described in U.S. Pat. No. 6,203,742.

[0091] The feedblock and die used are typically heated to facilitate polymer flow and layer adhesion. The temperature of the die depends on the polymers used. Whether the film is prepared by coating, lamination, sequential extrusion, coextrusion, or a combination thereof, the film formed and its layers will preferably have substantially uniform thicknesses across the film.

[0092] The present invention also provides systems of puncturable, resealable films and puncturing objects (e.g., fluid transfer devices) that can be tailored to each other to obtain a desired level of puncturability. For example, if a specific fluid transfer device is to be used as a puncturing object, the properties and characteristics of a film can be made to complement the puncturing object to provide the desired level of ease of puncturability. The fluid transfer device may be made of a particular material, may have a particular shape (including the shape of its tip), etc. Knowing this information, the composition and structure of a film can be made to provide the appropriate flexural rigidity of the film, the elongation at break of the film, the recovering stress of the film, and friction between the film and puncturing object to provide the desired level of ease of puncturability of the film. Optionally, sealability and resealability of the film can be tailored in the same manner.

[0093] Conversely, if a given film is to be punctured, based on its composition, structure, flexural rigidity, elongation at break, and recovering stress, a puncturing object can be chosen based on its composition (which will affect the friction between the film and puncturing object), and its shape (including the shape of its tip), to provide the desired level of ease of puncturability, resealability, and, optionally, sealability of the film. Specific examples of the methods of this invention as well as objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.

[0094] Puncture Resistance Test

[0095] Film samples were tested for puncture resistance using two variations of ASTM D3763-97a in which apparatus 110 illustrated in FIG. 5 was used to drive a puncturing object into a film and measure the flexure at rupture or break. In Variation A, opening 112 in the center of clamp assembly 114 of the test apparatus had a diameter of 25 mm and the puncturing object 116 was a metal plunger with a fixture holding a 10 microliter (AL) polypropylene plastic pipette (available from Eppendorf, Germany).

[0096] The pipette has a tip with an outside diameter of 0.84 mm and a shaft that tapered over a length of 5 mm to a substantially constant diameter of about 2 mm. In Variation B, hole 112 in the center of clamp assembly 114 of the test apparatus had a diameter of 76 mm. The puncturing object 116 was a smooth cylindrical metal probe having a hemispherical tip with a diameter of about 12 mm. The speed of the probe was 508 mm/min. The amount of deflection, i.e., displacement at peak load prior to rupture was measured in inches and converted into millimeters. Each reported value is an average of 5 test measurements.

[0097] Dynamic Coefficient of Friction Test

[0098] The dynamic coefficient of friction of the surface of the film sample that would first contact a puncturing object was determined by using ASTM D1894-95 with the apparatus described in drawing c, FIG. 1 of the ASTM and the sled as described in Section 5.1 of the ASTM. The sliding surface was a sheet of cast polypropylene film (available as7C12N from Shell Chemical Co., Beaupre, Ohio). A metal filament wire was used to pull the sled and various weights were placed on the sled to achieve different forces normal to the plane of the sample being tested. The normal force was calculated as the mass of the weight on the sled multiplied by the gravitational acceleration. The steady-state pulling force was determined, after initial transient values, for each normal force and was plotted against the normal force. The dynamic coefficient was the slope of the curve of the plotted data.

[0099] Opening Dimension Measurement

[0100] To determine this measurement, a punctured opening was viewed with a Boeckeler VIA-170 microscope (Tuscon, Ariz.) using 50and 200objective lenses. The dimensions were measured with a Moritex Scopeman (Model MS803, San Diego, Calif.) and the data was converted to an area measurement. Each reported value represents the average of three measurements.

[0101] Example 1 illustrates the effect of the dynamic coefficient of friction of a film on the puncture resistance and resealability of a multilayer film.

[0102] Sample A was a three layer film with a thermoplastic elastomer core layer and high density polyethylene (HDPE) outer layers. The outer layers were made of thermoplastic HDPE A (available as PETROTHENE LS3150-00, elongation percent at break of 300, Equistar Chemicals, Houston, Tex.). The outer layer material was conveyed through an extruder having multiple zones with a single screw extruder (diameter of 19 mm, L/D of 32/1, available from Killion, Inc., Cedar Grove, N.J.). The outer layer material extruder operated with zone temperatures increasing from 163 C. to 216 C. The outer layer material was conveyed through a gear pump to the A and C channels of the three-layer Cloeren feedblock (available from Cloeren Co., Orange, Tex.) that was set at 216 C. The core layer was made from a thermoplastic elastomer (available as KRATON D1107 styrene-isoprene block copolymer, recovering stress (at 300% elongation) of 2.07 MPa (300 psi), from Shell Chemical Co., Beaupre, Ohio) and conveyed through an extruder having multiple zones with a single screw extruder (diameter of 32 mm, L/D of 24/1, available from Killion, Inc.). The core layer material extruder operated with zone temperatures increasing from 188 C. to 216 C. The core layer material was passed to the B channel of the Cloeren feedblock. The resulting multilayered flow stream was passed through a single orifice film die (having a width of 254 mm (10 inch) and available from EDI, Chippewa Falls, Wis.) that was set at a temperature of 216 C. The resulting molten film was drop cast onto a chill roll, which was set at a temperature of 11 C., and collected. The line speed was 12.2 m/min., the individual flow rates of the outer layer and core layer were such that each outer layer had a thickness of about 3.1 micrometer (m) and the overall film thickness was measured at about 72 m.

[0103] Sample B was made as Sample A except a layer of Silicone Oil A (available as DC-200 PDMS oil from Dow Corning, Midland Mich.) was applied on one side of the three layer film.

[0104] Sample C was made as Sample A except a layer of Silicone Oil B (available as Part No. 700-01015 PDMS oil from Rheometrics Scientific, Piscataway, N.J.) was applied on one side of the three layer film.

[0105] Sample D was made as Sample A except a layer of pressure-sensitive adhesive (an acrylate-based pressure-sensitive adhesive (98/2 isooctyl acrylate/acrylic acid) made according to U.S. Pat. No. 5,804,610, Example 11 (except the ratio of IOA to AA was 98:2 instead of 97:3) having a thickness of approximately 125 m was applied on one side of the three layer film by lamination.

[0106] Each sample was measured for puncture resistance with Variation A, dynamic coefficient of friction on the surface that first contacted the puncturing object, and resulting opening area. Results are reported in Table 1 or in the discussion following the table.

TABLE 1
		Dynamic	Displacement
Sample	Surface modifier	friction coeff.	to break mm (in)
A	None	0.183	106 (4.167)
B	Silicone Oil A	0.028	18 (0.712)
C	Silicone Oil B	0.051	29 (1.153)
D	Adhesive	(a)	304 (11.958)
a: The coefficient of friction could not be measured because the sled did not move before the film broke.

[0107] The data in Table 1 indicate that puncture resistance as measured by displacement at break decreased when the frictional properties of the film surface first contacting the puncturing object decreased. Likewise, the puncture resistance increased when the surface friction increased.

[0108] For samples A and B, the effective diameters of the opening and the shaft of the puncturing object were also measured and a ratio of areas was calculated. The effective area of the puncturing object, calculated based on the largest diameter of the plastic pipette that entered the opening, was 2.00 mm. The effective diameter of the opening for Sample A and B, converting the area of the often jagged tear in the film into a circle having an equivalent area, was approximately 1.80 mm and 0.25 mm, respectively. The ratio of the effective area of the puncturing object to the effective area of the resulting opening for Samples A and B were calculated to be 0.81 and 0.016, respectively.

[0109] Example 2 illustrates the effect of the dynamic coefficient of friction of a film on the puncture resistance of a single layer film.

[0110] Sample A was made by extruding very low density polyethylene (available as ENGAGE 8200 from Dow Chemical Company, Midland, Mich.) into a film having a thickness of about 75 m. The polymer was conveyed with a single screw extruder through the core layer slot of the feedblock and single orifice film die used for Example 1.

[0111] Sample B was made as sample A except a layer of Silicone Oil A was applied one side of the single layer film.

[0112] Each sample was measured for puncture resistance with Variation A and dynamic coefficient of friction on the surface that first contacted the puncturing object. Results are reported in Table 2.

TABLE 2
		Dynamic	Displacement
Sample	Surface modifier	friction coeff.	to break mm (in)
A	None	3.38	142 (5.594)
B	Silicone Oil A	0.019	10 (0.402)

[0113] The data in Table 2 indicate that puncture resistance decreased when the frictional properties of the film surface first contacting the puncturing object decreased.

[0114] Example 3 illustrates the effect of stretching and relaxing a film on the puncture resistance of the film.

[0115] Sample A was made in a manner similar to Sample A of Example 1 except the three layer film was further consecutively stretched in one direction to 500% of its original length in both the machine and transverse directions. Then the film was allowed to recover until it reached a steady state in approximately 10 minutes.

[0116] Sample A and Sample A of Example 1 were measured for puncture resistance with Variation B. Results are reported in Table 3.

	TABLE 3
			Displacement
	Sample	Modification	to break mm (in)
	A	Stretched to 500% & relaxed	202 (7.943)
	1-A	none	139 (5.453)

[0117] The data in Table 3 indicate that puncture resistance increased when the film was stretched and relaxed before being punctured.

[0118] Example 4 illustrates the effect of stretching a film on the puncture resistance of the film.

[0119] Sample A was made by further stretching Sample A of Example 1 in one direction to 300% of its original length while held in the testing sample holder (and was punctured while it was stretched).

[0120] The sample was measured for puncture resistance with Variation A. Results are reported in Table 4 together with that of Sample A of Example 1.

	TABLE 4
			Displacement
	Sample	State	to break mm (in)
	A	Stretched to 300%	66 (2.579)
	1-A	original	106 (4.167)

[0121] The data in Table 4 indicate that puncture resistance decreased when the film was punctured while it was stretched.

[0122] Example 5 illustrates how a film can be made less or more puncture resistance depending on which side of a film consisting of two layers of different materials first contacts the puncturing object.

[0123] Sample A was made by further applying different materials to each side of Sample A of Example 1. Silicone Oil A was applied to side one of the film in a manner similar to Sample B of Example 1 and adhesive was applied to side two in a manner similar to Sample D of Example 1.

[0124] The sample was measured for puncture resistance with Variation A. Results are reported in Table 5 together with that of Sample A of Example 1.

	TABLE 5
			Displacement
	Sample	Surface	to break mm (in)
	Aside 1	Silicone Oil A	29 (1.136)
	1-A	original	106 (4.167)
	Aside 2	Adhesive	284 (11.182)

[0125] The data in Table 5 indicate that the film was significantly less puncture resistant when the penetrating means first contacted the side with the silicone oil rather than the side with the adhesive.

[0126] Example 6 illustrates another way a film can be made less or more puncture resistant depending on which side of a film consisting of two layers of different materials first contacts the puncturing object.

[0127] Sample A was made in a manner similar to that of Sample A of Example 1 except the side-2 outer layer material was a metallocene catalyzed very low density polyethylene (VLDPE) available as ENGAGE 8200 from Dow Chemical). The VLDPE was conveyed with a single screw extruder having multiple zones (Killion Model KLB075) that was operating with zone temperatures increasing from 160 C. to 216 C. The material was passed to the C channel of the three-layer feedblock. The line speed was 7.77 n/min. and the overall thickness was measured at 91 m.

[0128] Each side of the sample was measured for puncture resistance with Variation B. Results are reported in Table 6.

	TABLE 6
			Displacement
	Sample	Surface	to break mm (in)
	Aside 1	HDPE	203 (7.984)
	Aside 2	VLDPE	327 (12.871)

[0129] The data in Table 6 indicate that this film also had different puncture resistance depending on which outer layer material was first contacted with the penetrating means.

[0130] Example 7 illustrates the effect of outer layer thickness on puncture resistance.

[0131] Sample A-D were made as Sample A of Example 1 except gear pump settings on the outer layer extruder were adjusted to obtain a different outer layer thickness for each sample, as reported in Table 7, while the core layer extruder settings and line speed were unchanged.

[0132] The samples as well as Sample A of Example 1 were measured for puncture resistance with Variation B. Results are reported in Table 7.

	TABLE 7
		Gear pump	Outer layer	Displacement
	Sample	setting rpm	thickness m	to break mm (in)
	1-A	7	3.1	139 (5.453)
	A	10	3.5	122 (4.785)
	B	13	4.6	90 (3.552)
	C	18	6	76 (3.008)
	D	23	6.4	64 (2.510)

[0133] The data in the above table indicate that puncture resistance decreases as outer layer thickness increases for the construction tested.

[0134] Example 8 illustrates the effect of total film thickness on puncture resistance.

[0135] Sample A-C were made as Sample C of Example 7 except line speed settings were adjusted to obtain a different total film thickness for each sample, as reported in Table 8 (both extruder settings were unchanged).

[0136] The samples were measured for puncture resistance with Variation B. Results are reported in Table 8 together with that of Sample C of Example 7.

	TABLE 8
		Line speed	Total	Displacement
	Sample	meters/minute	thickness m	to break mm (in)
	A	7.6	122	55 (2.184)
	B	9.14	94	69 (2.730)
	7-C	12.2	76	76 (3.008)
	C	15.2	60	82 (3.242)

[0137] The data in the above table indicate that puncture resistance decreases as total film thickness increases for the construction tested.

[0138] Example 9 illustrates the effect of different outer layer materials, each having a different elongation at break, on puncture resistance of a three layer construction.

[0139] Sample A was made as Sample A of Example 1 except the outer layer material was HDPE B (available as DOWLEX IP60 HDPE, elongation percent at break of 225, from Dow Chemical); the extruders reached upper temperatures of 232 C., and the die was set at a temperature of 232 C. Also, the line speed and extruder flow rates were changed to result in a total film thickness of 140 m with outer layer thicknesses of about 10 m each.

[0140] Sample B and Sample C were made as Sample A except the outer layer material was HDPE A (described in Example 1) and HDPE C (ALATHON M5865 HDPE from Equistar, elongation percent at break of 800), respectively.

[0141] The samples were measured for puncture resistance with Variation B. Results are reported in Table 9.

	TABLE 9
		Outer layer	Elongation	Displacement
	Sample	Material	Percent	to break mm (in)
	A	HDPE B	225	62 (2.422)
	B	HDPE A	300	72 (2.828)
	C	HDPE C	800	136 (5.374)

[0142] The data in the above table indicate that as the elongation at break of the outer layer increased, the puncture resistance of the outer layer increased.

[0143] Example 10 illustrates the effect of outer layer thickness on the puncture resistance and resealability of a multilayer film.

[0144] Sample A, B and C were the same as Sample A, B and C of Example 7 except the films were punctured with a plastic pipette having a shaft diameter of 2.0 mm instead of a metal rod having a shaft diameter of 13.7 mm.

[0145] The samples were measured for puncture resistance with Variation A and the resulting area of the opening. Results are reported in Table 10.

TABLE 10
	Outer layer	Displacement	Ratio of opening
Sample	thickness m	to break mm (in)	area to pipette area
A	3.5	44 (1.719)	0.0070
B	4.6	38 (1.482)	0.0041
C	6	22 (0.852)	0.0009

[0146] As seen in Table 10, the ratio of the opening area to puncturing object area decreased as the film was less puncture resistant.

[0147] Example 11 illustrates the effect of a different core material with different recovering stress on puncture resistance of an outer layer/core layer/outer layer construction.

[0148] Sample A was made as Sample B of Example 9 except the core material was KRATON D1112P, having a recovering stress of 1.45 MPa (210 psi), available from Shell Chemical Company.

[0149] The sample was measured for puncture resistance. Results are reported in Table 11 with those of Sample B of Example 9.

TABLE 11
		Recovering	Displacement to
Sample	Core Material	stress MPa	break mm (in)
9-B	KRATON D1107	2.07	72 (2.828)
A	KRATON D1112P	1.45	51 (1.999)

[0150] The data in the above table indicate that as the recovering stress of the core material decreases, the puncture resistance of the film decreases. The elongations at break of the core layer materials of Examples 9-B and 11A were substantially the same at 1300% and 1400%, respectively.

[0151] Patents, patent applications, and publications disclosed herein are hereby incorporated by reference (in their entirety) as if individually incorporated. It is to be understood that the above description is intended to be illustrative, and not restrictive. Various modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing description without departing from the scope of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.