Fastener film

Abstract

A fastener film includes a plurality of structures disposed on a base layer. Each structure includes opposing first and second sidewalls extending from the base layer. Each of the first and second sidewalls includes first, second, and third portions where the second portions, but not the first and third portions, slope away from one another as the sidewalls extend away from the base layer. The first and second portions meet at a first distance from the base layer along the thickness direction, and the second and third portions meet at a greater second distance from the base layer along the thickness direction. Average widths of the structures at the first and second distances are W1 and W2, respectively, and average spacings between adjacent structures at the first and second distances are SI and S2, respectively, where 1.05 x S1≥ W2 > S2 > 0.95 x W1.

Description

[0001] FASTENER FILM

[0002] TECHNICAL FIELD

[0003] The present description relates generally to fasteners and more specifically to fastener films that may be reversibly fastened to other fastener films.

[0004] BACKGROUND

[0005] A fastener can include structures that interlock with structures of another fastener.

[0006] SUMMARY

[0007] According to some aspects, the present description provides a fastener film including a plurality of structures disposed on a base layer. Each structure includes opposing first and second sidewalls extending from the base layer. Each of the first and second sidewalls includes first, second, and third portions where the second portions, but not the first and third portions, slope away from one another as the sidewalls extend away from the base layer. The first and second portions meet at a first distance from the base layer along the thickness direction, and the second and third portions meet at a greater second distance from the base layer along the thickness direction. Average widths of the structures at the first and second distances are W1 and W2, respectively, and average spacings between adjacent structures at the first and second distances are SI and S2, respectively, where 1.05 x SI > W2 > S2 > 0.95 x Wl.

[0008] According to some aspects, the present description provides a fastener film including a plurality of unitary structures disposed on a base layer of the fastener film, where the structures are arranged along a width of the fastener film and extend along a length of the fastener film. Each structure includes opposing first and second side walls extending from the base layer along a thickness direction of the fastener film to a top portion of the structure, where the top portion extends between and connects the first and second sidewalls. Each of the first and second sidewalls includes first, second, and third portions sequentially arranged between the base layer and the top portion of the structure, where the first and second portions meet at a first distance from the base layer along the thickness direction, and the second and third portions meet at a greater second distance from the base layer along the thickness direction, such that for each of the first and third portions of first and second sidewalls, the first and second sidewalls slope toward one another as the first and second sidewalls extend away from the base layer, and for the second portions of the first and second side walls, the first and second sidewalls slope away from one another as the first and second sidewalls extend away from the base layer. Average widths of the structures at the first and second distances are W 1 and W2, respectively, and average spacings between adjacent structures at the first and second distances are SI and S2, respectively. In some embodiments, 1.05 x SI > W2 > S2 > 0.95 x Wl.

[0009] According to some aspects, the present description provides a fastener film including a plurality of unitary structures disposed on a base layer of the fastener film, where the structures are arranged along a width of the fastener film and extend along a length of the fastener film. Each structure includes opposing first and second side walls extending from the base layer along a thickness direction of the fastener film to a top portion of the structure, where the top portion extends between and connects the first and second sidewalls. Each of the first and second sidewalls includes a middle portion between the base layer and the top portion, where the middle portion extends along the thickness direction for at least 20%, and no more than 80%, of a height H of the structure from the base layer. The middle portions of the first and second sidewalls slope away from one another as the middle portions extend away from the base layer. The fastener film is configured to reversibly fasten to a second film substantially identical to the fastener film when a plurality of the structures of the fastener film is disposed in a corresponding plurality of spaces between structures of the second film, such that when the fastener and second films are reversibly fastened together and disposed between first and second rigid substrates with the base layer of the fastener film and a corresponding base layer of the second film fixedly attached to the respective first and second rigid substrates, the fastener and second films reversibly fasten the first and second rigid substrates to one another such that: prying the first and second rigid substrates apart causes the fastener and second films to separate from one another without substantial damage to the fastener and second films; and a peak shear stress to separate the fastener and second films is: for a shear force applied along the width of the fastener and second films, in a range of 1 to 10 MPa; and for a shear force applied along the length of the fastener and second films, in a range of 0. 1 to 6 MPa.

[0010] These and other aspects will be apparent from the following detailed description. In no event, however, should this brief summary be construed to limit the claimable subject matter.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a schematic cross-sectional view of a fastener film, according to some embodiments. FIG. 2 is a schematic illustration of a structure of one fastener film mating with a pair of structures of another fastener film, according to some embodiments.

[0013] FIG. 3 is a schematic perspective view of an assembly including two fastener films fastened together, according to some embodiments.

[0014] FIG. 4 is a schematic cross-sectional view of an assembly including fastener films disposed between and attaching substrates, according to some embodiments.

[0015] FIG. 5A is a schematic cross-sectional view of an assembly of fastener films disposed between a structural element and electrochemical cells, according to some embodiments.

[0016] FIG. 5B is a schematic cross-sectional view of first and second assemblies of fastener films disposed between a structural element and respective first and second electrochemical cells, according to some embodiments. DETAILED DESCRIPTION

[0017] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0018] In the assembly of durable goods (e.g., vehicles, appliances, electronic hardgoods), structural adhesives provide a convenient and low cost means for joining components. Accordingly, epoxy, acrylic, and polyurethane adhesives, for example, are used extensively for this purpose. Although structural adhesives offer advantages over mechanical fasteners, they also have drawbacks, including the needs for curing time, part fixturing, and curing equipment. Another drawback is the challenge of disassembly. Disassembly is often desired for rework, repair, or reclamation / recycling of materials. Such disassembly can be substantially difficult due to the bonding strength of structural adhesives that are achievable (high bond strength, elongation, and toughness). This challenge is emerging increasingly in the context of electric vehicle (EV) batteries, where there are strong economic and performance motivators for the increased use of structural adhesives, counterbalanced by a desire to be able to extract the battery cells later for replacement, repurposing, recycling, etc. without damage to the cells. Many commercial EV battery packs are adhesively assembled (e.g., bonding of cells to module components such as cooling plates) with no practical way to disassemble them. Efforts to repurpose or recycle the cells of these modules is starting with extreme measures (e.g., cryogenic cooling plus impact, solvent-soaking, excessive prying) to separate components, which are potentially damaging and / or expensive and / or dangerous.

[0019] Accordingly, the present description, according to some embodiments, provides an approach utilizing fastener films for enabling the easy separation of battery cells from structural or thermal management components to which they are bonded. Easier disassembly without damage to cells is desired to advance the sustainability of EV technology. Fasteners have been described in Int. Appl. Pub. No. WO 2022 / 112948 (Gorman et al.), in U.S. Pat. Nos. 8,641,278 (Ducauchuis et al.); 9,198,483 (Adams et al.); and 4,655,862 (Christoff et al.), and in U.S. Pat. Appl. Pub. No. 2020 / 0352287 (Gorman et al.), for example. Compared to previous fasteners, fastener films, according to some embodiments of the present description, maintain attachment under substantially higher shear forces while still allowing the fastener films to be separated without substantial damage to the fastener films even when the films are bonded to rigid substrates by prying apart the substrates. The fastener films may include structures disposed on a base layer where the structures have suitably sloping sidewalls such that the structures mate and interlock with corresponding structures of another fastener film having the same geometry. The structures of the fastened films may substantially fill the volume between the films which can aid in achieving the desired shear force resistance. The fastener films may be used in other applications where reversible fastening is desired. Reversible fastening has been used in a variety of applications, including applications in construction, machinery, medical equipment, automotive assembly, personal care products, and the textile industry, for example.

[0020] The fastener films may be formed via extrusion replication or via cast and cure replication methods. Such methods for forming structured (e.g., microstructured) films are known in the art. Extrusion replication processes and suitable materials for such processes are described in U.S. Pat. Appl. Pub. Nos. 2010 / 0252961 (Bay et al.); 2023 / 0226733 (Ausen et al.) and 2022 / 0266495 (Ausen et al.), for example. Cast and cure processes and suitable materials for such processes are described in U.S. Pat. Nos. 5,175,030 (Eu et al.); 5,183,597 (Lu); 8,012,567 (Gaides); and 8,133,572 (Gaides et al) and in U.S. Pat. Appl. Pub. No. 2012 / 0064296 (Walker, JR. et al.), for example. In brief summary, in cast and cure processes, structures may be fabricated via replication from a tool by casting and curing a polymerizable resin composition in contact with a structured surface of the tool and a substrate. It has traditionally been believed that structures with an undercut could not be made with such processes because of difficulty removing such structures from the tool. However, it has been found that cast and cured structures with an undercut can be removed from the tool and still achieve sufficient replication fidelity. It has been found, according to some embodiments, that utilizing materials that have a sufficient elasticity can aid in removing the resulting structures from the tool. In some embodiments, the material for making the structures of the fastener film is an elastic or hyperelastic material. Suitable materials can be made from a polymerizable material that includes oligomers having long linear chains contributing to elasticity. In some embodiments, the polymerizable material is a solvent-free ultraviolet (UV) curable acrylate formulation made from a flexible urethane acrylate oligomer diluted with lower viscosity multi-acrylates, for example. Such materials are generally described in U.S. Pat. Nos. 8,012,567 (Gaides) and 8,133,572 (Gaides et al), for example.

[0021] Conventionally structures of fasteners have been made by replicating structures and then deforming the replicated structures to form the final structures. The fastener films of the present description can be made, according to some embodiments, in a single replication step without a need for a secondary deformation step. The allows elastic materials that are difficult to deform in secondary deformation step to be utilized and allows substantially smaller fastening structures to be made. In addition, conventional fasteners, which require the secondary deformation step, can be slower and more expensive to manufacture than the fastener films of the present description, according to some embodiments.

[0022] FIG. 1 is a schematic cross-sectional view of a fastener film 400, according to some embodiments. FIG. 2 is a schematic illustration of a structure 310 of one fastener film mating with a pair of structures 310' of another fastener film, according to some embodiments. FIG. 3 is a schematic perspective view of an assembly 450 including two fastener films 400, 400' fastened together, according to some embodiments. Fastener film 400' can be as described for fastener film 400. The fastener film 400 includes structures 310 disposed on a base layer 320. In some embodiments, the fastener film 400 further includes a substrate 125 disposed on the base layer 320, where the base layer 320 is disposed between the substrate 125 and the plurality of structures 310. The structures 310 may be formed on the substrate 125 via a cast and cure process which produces the base layer 320 as a land layer so that the structures 310 and the base layer 320 are integrally formed. In this case, a unitary structure may comprise the base layer 320 and the structures 310. The structures are arranged along a width of the fastener film 400 and extend along a length of the fastener film 400. The fastener film 400 can define a length direction (y-direction) along the length of the film, a width direction (x-direction) along the width of the film, and a thickness direction (z -direction) along the thickness of the film where the width, length and thickness directions are mutually orthogonal. The structures 310 have an average width W0 at the base layer 320, average widths W1 and W2 at distances dl and d2 above the base layer 320, and an average width W3 at the top portions 325 of the structures 310. The top portions 325 can be substantially planar or can be curved. The top portions 325 can include peaks or tops 328 of the structures 310. An average spacing between the structures 310 is SO at the base layer 320, SI and S2 at the distances dl and d2 above the base layer 320, and S3 at the top portions 325 of the structures 310. The sidewalls 311 and 312 of the structures 310 have portions 331, 332, and 332 where an angle between the sidewall and a thickness direction (z-direction) of the fastener film is al, a2, and a3, respectively. The slopes of the sidewalls can be measured from optical images, or from scanning electron microscope (SEM) images, of the structures 310 in a cross-section parallel to the thickness and width directions.

[0023] In some embodiments, a fastener film 400 includes a plurality of unitary structures 310 disposed on a base layer 320 of the fastener film 400, where the structures are arranged along a width (x-direction) of the fastener film 400 and extend along a length (y-direction) of the fastener film 400. Each structure 310 includes opposing first and second sidewalls 311 and 312 extending from the base layer along a thickness direction (z-direction) of the fastener film 400 to a top portion 325 of the structure. The top portion 325 extends between and connects the first and second sidewalls 311 and 312. Each of the first and second sidewalls 311 and 312 includes first, second, and third portions 331, 332, and 333 (which may alternatively, or in addition, be referred to as lower, middle and upper portions) sequentially arranged between the base layer and the top portion of the structure. The first and second portions 331 and 332 meet at a first distance dl from the base layer 320 along the thickness direction. The second and third portions 332 and 333 meet at a greater second distance d2 (i.e., d2 > dl) from the base layer along the thickness direction. In some embodiments, for each of the first and third portions 331 and 333 of first and second sidewalls 311 and 312, the first and second sidewalls 311 and 312 slope toward one another as the first and second sidewalls 311 and 312 extend away (+z-direction) from the base layer 320 (e.g., in each of the first and third portions 331 and 333, the first and second sidewalls 311 and 312 are closer for larger z-coordinate values than for smaller z-coordinate values). In some embodiments, for the second portions 332 of the first and second sidewalls 311 and 312, the first and second sidewalls 311 and 312 slope away from one another as the first and second sidewalls 311 and 312 extend away from the base layer 320 (e.g., in the second portions 332, the first and second sidewalls 311 and 312 are farther apart for larger z- coordinate values than for smaller z-coordinate values).

[0024] In some embodiments, for each structure 310 and for each of the first and third portions 331 and 333 of first and second sidewalls 311 and 312, the first and second sidewalls 311 and 312 slope toward one another as the first and second sidewalls 311 and 312 extend away from the base layer 320 along substantially an entire length of each of the first and third portions 331 and 333. In some such embodiments, or in other embodiments, for each structure 310 and for the second portions 332 of the first and second sidewalls 311 and 312, the first and second sidewalls 311 and 312 slope away from one another as the first and second sidewalls 311 and 312 extend away from the base layer 320 along substantially an entire length of the second portions 332. The sidewalls may slope linearly away or toward one another or may have a curved shape. In some embodiments, for each structure 310 and for each of the first and third portions 331 and 333 of first and second sidewalls 311 and 312, the first and second sidewalls 311 and 312 slope substantially linearly (e.g., linear, or nominally linear, or linear up to deviations from linearity small (e.g., less than 10%) compared to a total length of the portion) toward one another as the first and second sidewalls 311 and 312 extend away from the base layer 320 along substantially an entire length of each of the first and third portions 331 and 333. In some such embodiments, or in other embodiments, for each structure 310 and for the second portions 332 of the first and second sidewalls 311 and 312, the first and second sidewalls 311 and 312 slope substantially linearly away from one another as the first and second sidewalls 311 and 312 extend away from the base layer 320 along substantially an entire length of the second portions 332.

[0025] Substantially an entire length (e.g., of a sidewall or a portion of a sidewall) can be the entire length or the entire length except possibly for small portions where a slope has shifted due to manufacturing variations or due to other variations (e.g., a radiused comer where portions meet). Substantially an entire length generally includes at least 75% of the entire length. In some embodiments, substantially an entire length can be at least 80, 85, 90, 95, 96, 97, 98, or 99 percent of the entire length.

[0026] In some embodiments, a difference between the second and first distances (d2-dl) is at least 10, 20, 30, 40, or 50 micrometers. In some such embodiments, or in other embodiments, d2-dl is no more than 400, 350, 300, 250, 200, 150, 100, or 90 micrometers. For example, in some embodiments, d2-dl is in a range of 10 micrometers to 400 micrometers, or 30 micrometers to 300 micrometers, or 40 micrometers to 200 micrometers.

[0027] In some embodiments, for each structure 310, the second portion 332 of each of the first and second sidewalls 311 and 312 makes an angle a2 with the thickness direction (z-direction). In some embodiments, a2 is at least 1, 2, 3, 4, or 5 degrees. In some such embodiments, or in other embodiments, a2 is no more than 20, 18, 15, 12 or 10 degrees. For example, in some embodiments, a2 is in a range of 1 to 20 degrees, or 2 to 15 degrees, or 3 to 12 degrees, or 4 to 10 degrees. In some such embodiments, or in other embodiments, a height hm of the second portion 332 is d2-dl and an overhang distance g is hm times a tangent of the angle a2, where the overhang distance g can be at least 2, 3, 4, 5, or 6 micrometers. In some such embodiments, or in other embodiments, the overhang distance g is no more than 50, 40, 30, or 20 micrometers. For example, in some embodiments, the overhang distance g is in a range of 2 to 50 micrometers, or 3 to 40 micrometers, or 4 to 30 micrometers, or 5 to 20 micrometers.

[0028] In some embodiments, for each structure 310, the first and third portions 331 and 333 of each of the first and second sidewalls 311 and 312 make angle al and a3, respectively, with the thickness direction (z-direction). In some embodiments, each of the angles al and a3 is greater than a2. In some embodiments, each of the angles al and a3 is at least 2, 3, 5, 7, or 10 degrees greater than a2. In some such embodiments, or in other embodiments, each of the angles al and a3 are at least 15, 20, 21, 22, or 23 degrees. In some such embodiments, or in other embodiments, each of the angles al and a3 is no more than 40, 35, 32, 31, or 30 degrees. The angles al and a3 may be about the same or may be different.

[0029] Average widths of the structures 310 at the first and second distances dl and d2 are W1 and W2, respectively. Average spacings between adjacent structures (e.g., neighboring structures 310a and 310b) at the first and second distances dl and d2 are SI and S2, respectively. In some embodiments, W2 > S2 to provide interlocking. In some embodiments, SI is about equal to W2 (e.g., SI can be equal to W2 to allow the structures 310 to fit snuggly together, or W2 may be a few percent less than S 1 to allow some space between structures of the fastened films, or W2 may be a few percent greater than S 1 so that the structures 310 compress when the structures of the fastened films are interlocked). In some embodiments, S2 is about equal to W 1 (e .g . , S2 can be equal to W 1 to allow the structures 310 to fit snuggly together, or W1 may be a few percent less than S2 to allow some space between structures of the fastened films, or W1 may be a few percent greater than S2 so that the structures 310 compress when the structures of the fastened films are interlocked). In some embodiments, 1.05 x SI > W2 > S2 > 0.95 x Wl. In some such embodiments, or in other embodiments, W2 is no more than 1.04, 1.03, 1.02, 1.01, or 1 times SI. In some such embodiments, or in other embodiments, S2 is at least 0.96, 0.97, 0.98, 0.99, or 1 times Wl. For example, in some embodiments, 1.04 x SI > W2 > S2 > 0.96 x Wl, or 1.02 x SI > W2 > S2 > 0.98 x Wl, or Sl > W2 > S2 > W1.

[0030] In some embodiments, average widths of the structures 310 at the base layer 320 and at the top portions 325 of the structures 310 are W0 and W3, respectively, and average spacings between adjacent structures (e.g., neighboring structures 310a and 310b) at the base layer 320 and at the top portions of the structures are SO and S3, respectively, where 1.05 x S3 > W0 and 1.05 x SO > W3. In some such embodiments, or in other embodiments, 1.04, 1.03, 1.02, 1.01, or 1 times S3 is greater than or equal to W0. In some such embodiments, or in other embodiments, 1.05, 1.04, 1.03, 1.02, 1.01, or 1 times SO is greater than or equal to W3. For example, in some embodiments, 1.03 x S3 > W0 and 1.03 x S0 > W3, or S3 > W0 and S0 > W3.

[0031] In some embodiments, the fastener film 400 is adapted to reversibly fasten to a second film (e.g., fastener film 400' schematically illustrated in FIG. 3) such that when the fastener film and the second film are fastened to one another, a plurality of the structures of the fastener film is disposed in a corresponding plurality of spaces between structures of the second film. In some embodiments, when the fastener and second films are fastened to one another, at least 90, 92, 94, 96, 98, 99, 99.5 percent of a total volume between the base layer 320 of the fastener film and a corresponding base layer of the second film is filed by the structures of the fastener and second films.

[0032] In some embodiments, the structures 310 have an average height H from the base layer to a top 328 of the structures, where 4 > H / W2 > 1. In some such embodiments, or in other embodiments, H / W2 is no more than 3.5, 3, or 2.5. In some such embodiments, or in other embodiments, H / W2 is at least 1, 1.25, 1.5, 1.75, or 2. For example, in some embodiments, 3.5 > H / W2 > 1.25 or 3 > H / W2 > 1.75, or 2.5 > H / W2 > 2. In some such embodiments, or in other embodiments, the average height H is at least 50, 75, 100, 125, 150, 175, or 200 micrometers. In some such embodiments, or in other embodiments, the average height H is no more than 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, or 0.3 mm. For example, in some embodiments, the average height H is in a range of 50 micrometers to 1 mm, or 75 micrometers to 0.9 mm, or 100 micrometers to 0.8 mm, or 125 micrometers to 0.6 mm, or 150 micrometers to 0.4 mm.

[0033] FIG. 4 is a schematic cross-sectional view of an assembly 550 including fastener films 400, 400' disposed between and attaching (e.g., rigid) substrates 411 and 412, according to some embodiments. A substrate is rigid when it is substantially stiffer than the assembly 450 of fastener films 400, 400'. For example, a rigid substrate can have a flexural modulus at least 5, 10, 20, 50, or 100 times greater than a flexural modulus of the assembly 450. Examples of rigid substrates include 5 mm thick glass, polymethylmethacrylate (PMMA), or steel plates.

[0034] In some embodiments, the fastener film 400 further includes an adhesive layer disposed on a side of the base layer 320 opposite the plurality of structures 310. For example, the adhesive layer 250 schematically illustrated in FIG. 4 may be considered to be a layer of the fastener film 400.

[0035] In some embodiments, a fastener film 400 includes a plurality of unitary structures 310 disposed on a base layer 320 of the fastener film 400, where the structures 310 are arranged along a width (x- direction) of the fastener film 400 and extend along a length (y-direction) of the fastener film 400. Each structure 310 includes opposing first and second sidewalls 311 and 312 extending from the base layer 320 along a thickness direction (z-direction) of the fastener film 400 to a top portion 325 of the structure 310, where the top portion 325 extends between and connects the first and second sidewalls 311 and 312. Each of the first and second sidewalls 311 and 312 includes a middle portion 332 between the base layer 320 and the top portion 325, where the middle portion extends along the thickness direction for at least 20%, and no more than 80%, of a height H of the structure 310 from the base layer 320. In some such embodiments, or in other embodiments, the middle portion extends along the thickness direction for at least 25% or at least 30% of the height H. In some such embodiments, or in other embodiments, the middle portion extends along the thickness direction for no more than 75% or 70% of the height H. In some embodiments, the middle portions 332 of the first and second sidewalls 311 and 312 slope away from one another as the middle portions 332 extend away from the base layer 320. In some embodiments, the fastener film 400 is configured to reversibly fasten to a second film 400' substantially identical (e.g., nominally identical but possibly differing due to manufacturing variations or other minor variations) to the fastener fdm 400 when a plurality of the structures of the fastener fdm is disposed in a corresponding plurality of spaces between structures of the second fdm (see, e.g., FIG. 3), such that when the fastener and second fdms 400 and 400' are reversibly fastened together and disposed between first and second rigid substrates 411 and 412 with the base layer of the fastener film 400 and a corresponding base layer of the second film fixedly attached (e.g., via respective adhesive layers 250 and 251) to the respective first and second rigid substrates 411 and 412, the fastener and second films 400, 400' reversibly fasten the first and second rigid substrates 411 and 412 to one another such that: prying (e.g., via applying a prying force Fz near an edge of the assembly) the first and second rigid substrates 411 and 412 apart causes the fastener and second films 400, 400' to separate from one another without substantial damage to the fastener and second films 400, 400'; and a peak shear stress to separate the fastener and second films 400, 400' is: for a shear force Fx applied along the width (x-direction) of the fastener and second films 400, 400', in a range of 1 to 10 MPa; and for a shear force Fy applied along the length (y-direction) of the fastener and second films 400, 400', in a range of 0. 1 to 6 MPa. In some such embodiments, or in other embodiments, the peak shear stress to separate the fastener and second films 400, 400' for a shear force Fx applied along the width (x-direction) of the fastener and second films 400, 400', is in a range of 1.5 to 8 MPa, or 2 to 7 MPa, or 3 to 7 MPa. In some such embodiments, or in other embodiments, the peak shear stress to separate the fastener and second films 400, 400' for a shear force Fy applied along the length (y-direction) of the fastener and second films 400, 400', in a range of 0.2 to 5 MPa, 0.4, to 4 MPa, 0.5 to 3 MPa, or 0.7 to 2.5 MPa. The shear stress is the corresponding shear force divided by an overlap area orthogonal to the thickness direction (z-direction). That is, the area for determining the shear stress as a shear force divided by area is the area in plan view along the thickness direction (i.e., area along the xy-plane). Without substantial damage means that there is no damage (e.g., no broken or badly deformed structures 310) that prevents the fastener and second films 400 and 400’ from again fastening to one another.

[0036] The fastener film 400 (e.g., included in the assembly 550) can have any geometry described elsewhere herein. In some embodiments, for each structure 310, the middle portion 332 (which may also be referred to as second portion 332) of each of the first and second sidewalls 311 and 312 makes an angle a2 with the thickness direction (z-direction) in a range of 1 to 20 degrees. In some embodiments, the middle portion 332 has a height hm along the thickness direction (z-direction), and an overhang distance g) is hm times a tangent of the angle a2, where the overhang distance g2 is in range of 2 to 50 micrometers. In some embodiments, hm is in a range of 10 micrometers to 400 micrometers. Any of the quantities a2, hm, or g may be in any of the corresponding ranges described elsewhere herein. In some embodiments, for each structure 310, each of the first and second sidewalls 311 and 312 includes a lower portion 331 adjacent the base layer 320 and an upper portion 333 adjacent the top portion 325 of the structure 310, where the middle portion 332 is disposed between the lower and upper portions 331 and 333, such that for each of the lower and upper portions 331 and 333 of first and second sidewalls 311 and 312, the first and second sidewalls 311 and 312 slope towards one another as the first and second sidewalls 311 and 312 extend away from the base layer. In some embodiments, for each structure 310 and for each of the first and second side walls 311 and 312, the middle portion 332 extends from a first distance dl from the base layer 320 along the thickness direction (z-direction) to a greater second distance d2 from the base layer 320 along the thickness direction; and average widths of the structures at the first and second distances are W1 and W2, respectively, average spacings between adjacent structures at the first and second distances are SI and S2, respectively, where 1.05x SI > W2 > S2 > 0.95 x Wl or the relationships between SI, S2, W1 and W2 can be as described elsewhere herein.

[0037] In some embodiments, an assembly 450, 550 (or 551, 552 described elsewhere herein) includes first and second films 400 and 400', where each of the first and second films is a fastener film of the present description, and where a plurality of the structures 310 of the first film 400 is disposed in a corresponding plurality of spaces between structures of the second film 400' such that the first and second films 400 and 400' are reversibly fastened to one another. In some embodiments, a peel strength along at least one in-plane direction using a 180 degree peel test of the first to the second films is at least 0.01, 0.012, 0.014, 0.016, 0.018, 0.02, 0.03, 0.04, 0.05, 0.08, 0.1, 0.15, or 0.2, N / cm. In some such embodiments, or in other embodiments, the peel strength along the at least one in-plane direction using a 180 degree peel test of the first to the second films is no more than 10, 8, 6, 4, 3, 2, 1, 0.8, 0.7, or 0.6 N / cm. For example, in some embodiments, a peel strength along at least one in-plane direction using a 180 degree peel test of the first to the second films is in a range of 0.01 to 10 N / cm, or 0.02 to 8 N / cm, or 0.03 to 6 N / cm, or 0.04 to 4 N / cm, or 0.05 to 2 N / cm, or 0.1 to 1 N / cm, or 0.01 to 1 N / cm, or 0.012 to 0.7 N / cm, or 0.014 to 0.6 N / cm. 180 degree peel strengths Fpx and Fpy along the respective x- and y- directions are schematically illustrated in FIG. 3. Peel strengths can be increased (resp., decreased) by increasing (resp., decreasing) the overlap distance g, for example. The peel strength may be measured as described in the ASTM D3330 / D3330M-04(2018) test standard, for example.

[0038] In some embodiments, the assembly 450, 550 (or 551, 552 described elsewhere herein) further includes, for at least one of the first and second films 400, 400', an adhesive layer (e.g., one or both of 250, 251 schematically illustrated in FIG. 4) disposed on a side of the base layer opposite the plurality of structures. In some embodiments, the assembly 550 further includes first and second substrates 411 and 412, where the first and second films 400 and 400' are disposed between the first and second substrates 411 and 412 with the base layers of the first and second films 400 and 400' fixedly attached to the respective first and second substrates 411 and 412. In some embodiments, each of the first and second substrates 411 and 412 are rigid and prying the first and second substrates 411 and 412 apart causes the first and second films 400 and 400' to separate from one another without substantial damage to the first and second films 400 and 400'. In some embodiments, the first and second films 400 and 400' reversibly fasten the first and second substrates 411 and 412 to one another such that a peak shear stress to separate the first and second films is: for a shear force Fx applied along the width of the first and second films, in a range of 1 to 10 MPa (or the peak shear stress can be in a range described elsewhere herein); and for a shear force Fy applied along the length of the first and second films, in a range of 0.1 to 6 MPa (or the peak shear stress can be in a range described elsewhere herein). Shear stresses can be increased (resp., decreased) by increasing (resp., decreasing) a height or width of the structures 310, for example. The peak shear stress may be measured as described in the ASTM DI 002- 10(2019) test standard, for example.

[0039] In some embodiments, the first and second substrates 411 and 412 are or include respective first and second portions of a battery pack. In some embodiments, the substrates 411 and 412 may be independently selected from the group consisting of an electrochemical cell and a structural element (e.g., of a battery pack).

[0040] FIG. 5 A is a schematic cross-sectional view of an assembly 551 including an assembly 450 of fastener films disposed between a structural element 280 (e.g., of a battery pack) and electrochemical cells 411 and 412, according to some embodiments. FIG. 5B is a schematic cross-sectional view of an assembly 552 including first and second assemblies 450 and 450' of fastener films disposed between a structural element 280 (e.g., of a battery pack) and respective first and second electrochemical cells 411 and 412, according to some embodiments. The assembly 450' can be as described for assembly 450. In some embodiments, the assembly 450 is substantially coextensive with one or both of the first and second substrates 411 and 412. For example, in the assembly 550 of FIG. 4, the assembly 450 is substantially coextensive with each of the first and second substrates 411 and 412, while in the assembly 551 of FIG. 5 A, the assembly 450 is substantially coextensive with the substrate 280, and in the assembly 552 of FIG. 5B, the first and second assemblies 450 and 450' are substantially coextensive with the respective first and second substrates 411 and 412.

[0041] In some embodiments, the assembly 450, 550, 551, 552 further includes first and second substrates 411 and 412, where the first and second films 400 and 400' are disposed between the first and second substrates 411 and 412 with the base layers of the first and second films fixedly attached to the respective first and second substrates. In some embodiments, the first and second substrates 411 and 412 are or include respective first and second electrochemical cells. In some embodiments, the first and second substrates 411 and 412 are or include respective first and second portions of a battery pack (e.g., a battery pack assembly can be or include assembly 550, 551, or 552). In some embodiments, the first and second portions of the battery pack are independently selected from the group consisting of a structural element 280 and an electrochemical cell 411 and / or 412. In some embodiments, the structural element 280 is selected from the group consisting of a cooling plate, a frame, a lid, a cross beam, and a battery cell.

[0042] EXAMPLES

[0043] Fastener films generally as illustrated in FIGS. 1-3 were made in a cast and cure processes using a solvent-free ultraviolet (UV) curable acrylate formulation made from a flexible urethane acrylate oligomer diluted with lower viscosity multi-acrylates to form structures 310 and a base layer 320 on a substrate 125 where the substrate was a primed polyethylene terephthalate (PET) film. Such acrylate formulations and cast and cure processes are generally described in U.S. Pat. Nos. 8,012,567 (Gaides) and 8,133,572 (Gaides et al). Example 1 was made by hand spreads while Examples 2 and 3 were made on a continuous roll-to-roll line.

[0044] For Examples 1 and 2, the designed height H was about 208 micrometers; the designed pitch (S2+W2) was about 159 micrometers; the designed angles al, a2, and a3 were about 27, 5, and 27 degrees, respectively; and the designed widths Wl, W2, and W3 were 70, 85, and 25 micrometers, respectively. For Example 3, the designed height H was about 208 micrometers; the designed pitch (S2+W2) was about 159 micrometers; the designed angles al, a2, and a3 were about 26, 5, and 26 degrees, respectively; and the designed widths Wl, W2, and W3 were 69, 95, and 40 micrometers, respectively.

[0045] For each Example, a pair of resulting fdms were fastened together to form an assembly 450 (see, e.g., FIG. 3), UV curable adhesive was laminated to the assembly on both sides to make a double-sided tape. Strips were cut from the double-sided tape, UV activated, and samples were made with 14”xl” bond area overlap for testing shear in both cross-pattern direction (x-direction) and down-pattern direction (y- direction). Samples were tested as assembled and, in some cases, disassembled, reassembled, and retested. For some cases, three samples were tested, and mean and standard deviation were determined. Results are reported in the following table. In cases where a mean and standard deviation were determined, the result is reported as mean ± standard deviation.

[0046] Peel strength was also tested for initially assembled samples using a 180 degree peel test.

[0047] Pressure sensitive adhesive (PSA) transfer tapes were used in place of the UV curable adhesive transfer tapes for the peel tests. Results are reported in the following table.

[0048] Example Peel Strength (N / cm)

[0049] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1. 1, and that the value could be 1.

[0050] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially” with reference to a property or characteristic is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description and when it would be clear to one of ordinary skill in the art what is meant by an opposite of that property or characteristic, the term “substantially” will be understood to mean that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited.

[0051] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

[0052] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

What is claimed is:

1. A fastener film comprising a plurality of unitary structures disposed on a base layer of the fastener film, the structures arranged along a width of the fastener film and extending along a length of the fastener film, each structure comprising: opposing first and second sidewalls extending from the base layer along a thickness direction of the fastener film to a top portion of the structure, the top portion extending between and connecting the first and second sidewalls, each of the first and second sidewalls comprising first, second, and third portions sequentially arranged between the base layer and the top portion of the structure, the first and second portions meeting at a first distance from the base layer along the thickness direction, the second and third portions meeting at a greater second distance from the base layer along the thickness direction, such that for each of the first and third portions of first and second sidewalls, the first and second sidewalls slope toward one another as the first and second sidewalls extend away from the base layer, and for the second portions of the first and second side walls, the first and second sidewalls slope away from one another as the first and second sidewalls extend away from the base layer, wherein average widths of the structures at the first and second distances are W 1 and W2, respectively, and average spacings between adjacent structures at the first and second distances are SI and S2, respectively, 1.05 x SI > W2 > S2 > 0.95 x Wl.

2. The fastener film of claim 1, wherein average widths of the structures at the base layer and at the top portions of the structures are WO and W3, respectively, and average spacings between adjacent structures at the base layer and at the top portions of the structures are SO and S3, respectively, 1.05 x S3 > WO and 1.05 x S0 > W3.

3. The fastener film of claim 1, wherein for each structure: for each of the first and third portions of first and second sidewalls, the first and second sidewalls slope substantially linearly toward one another as the first and second sidewalls extend away from the base layer along substantially an entire length of each of the first and third portions; and for the second portions of the first and second sidewalls, the first and second sidewalls slope substantially linearly away from one another as the first and second sidewalls extend away from the base layer along substantially an entire length of the second portions.

4. The fastener film of claim 1 being adapted to reversibly fasten to a second film according to claim 1 such that when the fastener film and the second film are fastened to one another, a plurality of the structures of the fastener film is disposed in a corresponding plurality of spaces between structures of the second film.

5. The fastener film of claim 4, wherein when the fastener and second films are fastened to one another, at least 90 percent of a total volume between the base layer of the fastener film and a corresponding base layer of the second film is filed by the structures of the fastener and second films.

6. The fastener film of claim 1, wherein the structures have an average height H from the base layer to a top of the structures, 4 > H / W2 > 1.

7. The fastener film of claim 6, wherein the average height H is in a range of 50 micrometers to 1 mm.

8. The fastener film of claim 1, wherein for each structure, the second portion of each of the first and second sidewalls makes an angle with the thickness direction in a range of 1 to 20 degrees.

9. The fastener film of claim 8, wherein a height hm of the second portion is a difference between the second and first distances, and an overhang distance is hm times a tangent of the angle, the overhang distance being in range of 2 to 50 micrometers.

10. An assembly comprising first and second films and first and second substrates, each of the first and second films being a fastener film according to claim 1, a plurality of the structures of the first film disposed in a corresponding plurality of spaces between structures of the second film such that the first and second films are reversibly fastened to one another, the first and second films disposed between the first and second substrates with the base layers of the first and second films fixedly attached to the respective first and second substrates.

11. The assembly of claim 10, wherein the first and second substrates comprise respective first and second portions of a battery pack.

12. A fastener film comprising a plurality of unitary structures disposed on a base layer of the fastener film, the structures arranged along a width of the fastener film and extending along a length of the fastener film, each structure comprising: opposing first and second sidewalls extending from the base layer along a thickness direction of the fastener film to a top portion of the structure, the top portion extending between and connecting the first and second sidewalls, each of the first and second sidewalls comprising a middle portion between the base layer and the top portion, the middle portion extending along the thickness direction for at least 20%, and no more than 80%, of a height H of the structure from the base layer, the middle portions of the first and second sidewalls sloping away from one another as the middle portions extend away from the base layer,wherein the fastener film is configured to reversibly fasten to a second film substantially identical to the fastener film when a plurality of the structures of the fastener film is disposed in a corresponding plurality of spaces between structures of the second film, such that when the fastener and second films are reversibly fastened together and disposed between first and second rigid substrates with the base layer of the fastener film and a corresponding base layer of the second film fixedly attached to the respective first and second rigid substrates, the fastener and second films reversibly fasten the first and second rigid substrates to one another such that: prying the first and second rigid substrates apart causes the fastener and second films to separate from one another without substantial damage to the fastener and second films; and a peak shear stress to separate the fastener and second films is: for a shear force applied along the width of the fastener and second films, in a range of 1 to 10 MPa; and for a shear force applied along the length of the fastener and second films, in a range of 0.1 to 6 MPa.

13. The fastener film of claim 12, wherein for each structure, the middle portion of each of the first and second sidewalls makes an angle with the thickness direction in a range of 1 to 20 degrees.

14. The fastener film of claim 12, wherein for each structure, each of the first and second sidewalls comprises a lower portion adjacent the base layer and an upper portion adjacent the top portion of the structure, the middle portion disposed between the lower and upper portions, such that for each of the lower and upper portions of first and second sidewalls, the first and second sidewalls slope towards one another as the first and second sidewalls extend away from the base layer.

15. The fastener film of claim 12, wherein: for each structure and for each of the first and second sidewalls, the middle portion extends from a first distance from the base layer along the thickness direction to a greater second distance from the base layer along the thickness direction; and average widths of the structures at the first and second distances are W1 and W2, respectively, average spacings between adjacent structures at the first and second distances are SI and S2, respectively, 1.05 x SI > W2 > S2 > 0.95 x Wl.

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