Perforated adhesive handling layers for structural adhesive tapes

Abstract

A handling layer comprising a polymeric formulation that is dry to the touch in its green state, and a plurality of perforations, wherein the handling layer is able to be applied to a tacky adhesive and upon cure of the tacky adhesive and handling layer, the lap shear strength in accordance with ASTM D1002 of the handling layer and tacky adhesive is within 15% or less of the lap shear strength of the tacky adhesive without the handling layer.

Description

Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025PERFORATED ADHESIVE HANDLING LAYERS FOR STRUCTURAL ADHESIVE TAPESCLAIM OF PRIORITY

[0001] This application claims the benefit of the filing date of United States Provisional Application Serial No. 63 / 737,213, filed on December 20, 2024. The contents of that application is incorporated by reference herein in its entirety and for all purposes.FIELD OF INVENTION

[0002] The present teachings relate generally to perforated adhesive handling layers for structural adhesive tapes. The perforated adhesive handling layers allow for easy handling of tacky adhesive tapes while maintaining superior adhesive properties in comparison to nonperforated handling layers, and for anchoring functional substances on the surface of the adhesive tapes.BACKGROUND

[0003] Heat-activated, toughened, structural adhesives have been widely used in various industries, particularly in the automotive industry. These adhesives have been used to increase the stiffness of the car body for driving comfort. They allow for the use of lightweight materials like aluminum and carbon composites for fuel efficiency. When used in combination with mechanical fastening including welding and riveting, these structural adhesives provide a vehicle with an even distribution of the load and toughened bonding. Many of these structural adhesives are typically in a paste form (e.g., Betamate® products from Dupont) for robotic dispensing. However, where robotic dispensing is not possible or desirable, structural adhesive tapes can be used as bonding materials. These adhesive tapes are pressure sensitive in the green state (prior to curing and / or foaming) for bonding to a first substrate, which is then mated to a second substrate prior to curing by heat activation. When cured, the structural adhesive tapes provide comparable bonding performance to paste structural adhesives.

[0004] Since structural adhesive tapes are often tacky in the green state, release handling layers such as polyethylene (PE) films and other release papers are typically used on the top and bottom of the tapes for handleability, storage, and application. Release handling layers provide a dry-to- touch surface and dimensional stability when operators apply the tapes to the substrates. They also enable packaging stacks of multiple adhesive layers for transportation and / or storage. However, release handling layers must be removed prior to bonding because they do not haveAttorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025 any adhesive properties and instead act as an isolation layer between the adhesive and substrates. Removing top handling layers can be troublesome because they tend to adhere to the adhesive layer, especially in an environment where ambient temperature is high. To overcome this challenge, adhesive handling layers have been developed to provide both handleability and adhesive properties. In contrast to release handling layers, adhesive handling layers are thin films with adhesive properties that are only applied on top of the adhesive tapes. These adhesive handling layers are expected to show good adhesion to substrates and thus do not need to be removed prior to application of a tape to a substrate.

[0005] Many adhesive handling layers are typically made of high molecular weight polymers which are required for film formation, along with additives for processability and adhesion. Because of the inferior wettability of high molecular weight polymer, these adhesive handling layers have shown adhesion loss to lubricant-contaminated surface compared to adhesive tapes without handling layers, especially when baked at low temperatures (e.g., 311 °F and 285 °F). Additionally, significant decrease in impact peel strength has also been noted when adhesive handling layers are used on crash-toughened structural adhesive tapes (e.g., structural adhesives with additional toughening components).

[0006] The present teachings seek to provide perforated adhesive handling layers for improved adhesive properties in comparison to non-perforated handling layers while maintaining minimal surface tack for handleability and tensile strength for dimensional stability.SUMMARY OF INVENTION

[0007] The teachings herein are directed to a handling layer comprising a polymeric formulation that is dry to the touch in its green state, and includes a plurality of perforations, wherein the handling layer is able to be applied to a tacky adhesive and upon cure of the tacky adhesive and handling layer, the lap shear strength in accordance with ASTM D1002 of the handling layer and tacky adhesive is within 15% or less of the lap shear strength of the tacky adhesive without the handling layer.

[0008] The plurality of perforations may have a perforation size in the range of from 0.02 to 2 inches, or 0.5 to 50 mm.

[0009] The plurality of perforations may be located in a perforation area which has an area in the range of from about 0.01 mm2to about 380 mm2(0.0004 to 15 in2).

[0010] The percentage of the perforation area may be in the range of from 3 to 75% of the total area of the handling layer.Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025

[0011] The perforation shape may be selected from: round, triangular, square, elongated, slotted, star, crystal, houndstooth style, polygonal, hexagonal, and any combination thereof.

[0012] The distribution of perforations may be aligned, staggered, or random.

[0013] One or more functional substances may be anchored onto the perforated area.

[0014] The one or more functional substances may include conductive steel spheres.

[0015] An adhesive including the handling layer has a wedge impact peel load that may be at least 80% of the wedge impact peel load (0.030” EG60, 2 m / s impact speed, 25 kg drop weight) of the adhesive without the handling layer.

[0016] An adhesive including the handling layer has a wedge impact peel energy that may be at least 80% of the wedge impact peel energy (0.030” EG60, 2 m / s impact speed, 25 kg drop weight) of the adhesive without the handling layer.

[0017] The thickness of the layer in between two perforations may be the same as the original thickness of the non-perforated handling layer, and the thickness of the edge of the perforations (e.g., the wall of the perforations) is at least three times the thickness of the layer in between the two perforations.

[0018] The plurality of perforations may receive metallic spheres that adhere to the adhesive and the metallic spheres allow for no shunt welding of the adhesive.

[0019] Each perforation may be spaced from adjacent perforations by at least 5 mm.

[0020] Each perforation may be spaced from adjacent perforations by at least 10 mm.

[0021] Each perforation may be spaced from adjacent perforations by at least 20 mm.

[0022] The handling layer may comprise a Bisphenol A and cashew and nutshell liquid polymer with epichlorohydrin.

[0023] The handling layer may comprise Bisphenol A and zinc oxide.

[0024] The plurality of perforations may be located in a perforation area and the perforation area is in the range of at least 20% of the total area of the entirety of the handling layer.

[0025] The teachings herein are further directed to a structural adhesive including a perforated handling layer as described herein disposed on a top surface of the adhesive.

[0026] The adhesive may comprise a Bisphenol A and cashew and nutshell liquid polymer with epichlorohydrin.

[0027] The adhesive may comprise a Bisphenol A and cashew and nutshell liquid polymer with epichlorohydrin.

[0028] The adhesive may be non-expanding.

[0029] The adhesive may foam upon exposure to a stimulus.

[0030] The adhesive may foam upon exposure to heat.Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025

[0031] The adhesive may be co-extruded with the handling layer.

[0032] The teachings herein are also directed to a method comprising extruding a structural adhesive, wherein the structural adhesive is epoxy-based, forming a handling layer, perforating the handling layer with a plurality of openings, locating the handling layer onto one or more surfaces of the structural adhesive, and optionally locating a plurality of metallic spheres onto the structural adhesive.BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A is a SEM image of a laser perforated film having relatively small holes that are staggered.

[0034] Figure 1 B is a SEM image of a laser perforated film having relatively small holes that are aligned.

[0035] Figure 1 C is a SEM image of a laser perforated film having relatively large holes that are aligned.

[0036] Figure 1 D is a SEM image of a laser perforated film detailing the wall thickness of the holes.

[0037] Figure 2A is a SEM image of a laser perforated film having relatively small holes that are staggered.

[0038] Figure 2B is a SEM image of a laser perforated film having relatively small holes that are staggered with beads disposed thereon.DETAILED DESCRIPTION

[0039] The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the present teachings, its principles, and its practical application. The specific embodiments of the present teachings as set forth are not intended as being exhaustive or limiting of the present teachings. The scope of the present teachings should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. Other combinations are also possible as will be gleaned from the following claims, which are also hereby incorporated by reference into this written description. Percentages herein refer to weight percent, unless otherwise indicated.Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025

[0040] The handling layer and / or adhesive tape of the present teachings may be applied to various articles of manufacture for adding handleability, improved adhesion, and functional substances to portions or members of the articles. Examples of such articles of manufacture include, without limitation, aerospace, automotive, submarine construction, boating, household or industrial appliances, furniture, buildings, or the like.

[0041] The present teachings are directed to a perforated adhesive handling layer for the handleability of structural adhesive tapes without sacrificing the adhesive properties significantly and for anchoring functional substances on the surface of the adhesive tapes.

[0042] The present teachings are directed to perforated adhesive handling layers providing superior adhesive performance and minimal surface tack prior to activation for easy handling and storage of structural adhesive tapes.

[0043] Mechanical and laser perforation are two common processes to prepare perforated film materials. Mechanical perforation is performed with the help of needles or pins which punch out part of the film. Laser perforation, on the other hand, utilizes a laser pulse. When the size of the hole is smaller than the laser spot’s diameter, laser pulse is used to penetrate or burn the film to generate the desired perforation characteristics. For larger perforations, the diameter of the hole is transversed by moving the laser beam to achieve perforation. Both processes can be used to perforate the adhesive handling layers described herein. In some cases, depending on the chemical composition of the adhesive handling layers, the laser perforations will have a “seared” edge with greater thickness than remainder of the layer which helps to reinforce holes and prevent tearing of the film during the manufacturing process. The raised wall also facilitates a dry-to-touch surface when being applied to the top of tacky structural adhesive tapes.

[0044] Perforation shape and distribution can be easily tailored for targeted performance. Perforation shape may be round, triangle, square, elongated, slotted, star, crystal, houndstooth style, hexagonal, polygonal and the like. Distribution of perforations may be aligned, staggered, or random. The shape, size, and distribution of the perforations may be the same or they may vary along the layer.

[0045] Perforation size and perforation area play a role in adhesive performance and handling layer processibility in production. Larger perforation size and area allows for more adhesive in direct contact with the substrates and thus better adhesive performance and cohesive failure mode. On the other hand, they also lower the strength of the adhesive handling layer, making it more susceptible to breakage in the film lamination process. It is generally preferable for the perforation size to be greater than or equal to 0.02 inches (0.5 mm) and less than 2 inches (50 mm), more typically greater than 0.03 (0.76 mm) inches and less than 1.5 inches (38 mm), andAttorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025 even more typically greater than 0.038 inches (0.97 mm) and less than 1 inch (25.5 mm). The perforation area (a section of the film where the perforations are located) may be at least 5%, more typically at least 15%, and even more typically at least 30% of the surface area of the entirety of the film layer. The perforation area may be less than 80%, less than 60%, or even less than 40% of the entirety of the film layer.

[0046] The adhesive used in the following examples is a structural epoxy-based adhesive. The adhesive may include one or more of a phenol, polymer with formaldehyde, glycidyl ether, rubber modified epoxy resin, epoxy resin, 2-propenoic acid, 2-methyl-, methyl ester, polymer with 1 ,3- butadiene and ethenylbenzene, liquid adduct, polyurethane adduct, formaldehyde, oligomeric reaction products with l-chloro-2,3-epoxypropane and phenol, calcium oxide, bisphenol A - epichlorohydrin polymer and carbon black.

[0047] The structural adhesive may be a commercially available adhesive, which may be L-5005 sold by L&L Products, Inc.

[0048] The film handling layers used in the present teachings may be formulated thin films with adhesive properties. The handling layers may include for example: (handling layer 1) Bisphenol A and Cashew and nutshell liquid polymer with epichlorohydrin; (handling layer 2) Bisphenol A and zinc oxide. The formulated films may have a thickness of about 25 microns. The lap shear strength in accordance with ASTM D1002 of adhesive handling layers 1 and 2 may be 21.8 MPa (e.g., at least 20 MPa) and 14.6 MPa (e.g., at least 12 MPa), respectively, on clean electrogalvanized steel after being baked at 325 °F for 30 minutes. Adhesive handling layers with and without perforation have been used as top handling layers on adhesive tapes in the present teachings.

[0049] Table 1. Characteristics of perforation pattern A, B, and C.

[0050] Perforation characteristics including perforation number per unit area, perforation size and distribution can be tuned (see Figure 1 and Table 1). Patterns A and B have smaller holes vs pattern C. Perforations of pattern B and C are aligned in contrast to the staggered perforation of pattern A. Laser perforation also changes the thickness of the handling layer in affinity to the laser spot. The high heat of the laser burns the film rather than removing part of the film as inAttorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025 mechanical perforation, leading to seared, thicker walls just adjacent the perforation. As shown in Figure 1 D, the thickness between two perforations stays at approximately 25 microns, which is the same as the original thickness of the non-perforated handling layer. The wall of the perforations is over 90 microns. The greater wall thickness helps to reinforce holes and prevent tearing during a film lamination process. The raised wall also facilitates a dry-to-touch surface when being applied to the top of tacky structural adhesive tapes.

[0051] Table 2. Properties of non-expandable structural tapes with adhesive handling layer 1 of different patterns in comparison to the adhesive without a handling layer.

[0052] Crash-toughened adhesives are used in the automotive industry to improve crash worthiness of a vehicle. When used in combination with mechanical fastening, they help to sustain higher loads. Additionally, these adhesives enable the use of lightweight materials that are difficult or impossible to weld like aluminum and carbon composites. Critical properties of such adhesives include wedge impact peel strength and energy. Non-perforated handling layers have been used to handle non-expandable adhesive tapes. Unfortunately, significant loss of wedge impact peelAttorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025 strength and energy is observed in films without perforations. As shown in Table 2, an adhesive without a handling layer has a wedge impact peel strength of 40 N / mm and peel energy of 19 J at room temperature. When a non-perforated adhesive handling layer 1 is used as the top handling layer (sample 2), the wedge impact peel strength and peel energy both dropped significantly by over 30%. In contrast, sample 3, 4, and 5 with perforated handling layers all show drastic improvement in wedge impact peel strength and peel energy. Handling layers with a greater number of smaller perforations per unit area (i.e., sample 3 and 4) lead to a more noticeable increase compared to handling layers with larger perforation but less perforation per unit area (sample 5). Of note, sample 5 shows greater T-peel strength than samples 3 and 4, suggesting that larger perforation is more effective at maintaining the T peel strength relative to adhesive without a top handling layer.

[0053] Table 3. Properties of low-expanding structural adhesive tapes with and without handling layers*0.060" EG60, 2.5-3.0 mg / inch2FERROCOTE 61MAL HCI, 2 inch / min crosshead speed, 0.75 mm bondline

[0054] Low-expansion structural adhesive tapes have been widely used in automotive industries. Adhesion to metal with lubricant contamination at relatively low bake temperatures (e.g., 311 °F and 285 °F) has always been a tremendous challenge due to the adhesion loss caused by nonperforated handling layers. As shown in Table 3, when a non-perforated handling layer is used, lap shear strength of the adhesive tape on FERROCOTE 61MAL HCI-coated galvanized steel drops significantly when cured at both 285 °F and 311 °F. For example, lap shear strength of adhesive tape with a non-perforated handling layer drops to 9.1 MPa in comparison to 15.8 MPa for the adhesive without handling layer when cured at 285 °F. On the other hand, the use of perforated handling layer 1-A results in a significant increase in lap shear strength (i.e., 16.1 MPa) which is comparable to adhesive tape without a top handling layer. As such, perforated handlingAttorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025 layers are proven to enable better adhesion to lubricant-contaminated surfaces, especially at low bake temperatures.

[0055] Table 4. Influence of different adhesive handling layers on the performance of nonexpandable structural tapes

[0056] In addition to perforation patterns, the adhesive properties of the handling layer also play an important role in the performance of adhesive tapes. Adhesive handling layers can be used to bond various substrates on their own due to their adhesive properties. Two different adhesive handling layers are demonstrated in the examples. The lap shear strength of non-perforated adhesive handling layers 1 and 2 is 21.8 MPa and 14.6 MPa, respectively, on clean electrogalvanized steel after baked at 325 °F for 30 min. The present teachings evaluate both handling layers with perforation pattern A for non-expandable adhesive tapes. As shown in Table 4, although both handling layers are perforated with pattern A, sample 6 with perforated handling layer 2 shows inferior properties to sample 3 with perforated handling layer 1 .

[0057] Figure 2 shows structural adhesive tapes with perforated handling layer and with (B) and without (A) electrically conductive beads.

[0058] In addition to providing handleability and better adhesion, perforated film can also be used to anchor functional substances on the surface of the adhesive tapes. As shown in Figure 2B, electrically conductive beads are sprinkled onto an adhesive tape with a perforated adhesive handling layer. The perforated area with exposed tape holds the beads due to surface tack, enabling no-shunt weldability of the adhesive tapes.

[0059] As used herein, unless otherwise stated, the teachings envision that any member of a genus (list) may be excluded from the genus; and / or any member of a Markush grouping may be excluded from the grouping.Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025

[0060] Unless otherwise stated, any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component, a property, or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that intermediate range values such as (for example, 15 to 85, 22 to 68, 43 to 51 , 30 to 32 etc.) are within the teachings of this specification. Likewise, individual intermediate values are also within the present teachings. For values which are less than one, one unit is considered to be 0.0001 , 0.001 , 0.01 , or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner. As can be seen, the teaching of amounts expressed as "parts by weight" herein also contemplates the same ranges expressed in terms of percent by weight. Thus, an expression in the of a range in terms of at "'x' parts by weight of the resulting polymeric blend composition" also contemplates a teaching of ranges of same recited amount of "x" in percent by weight of the resulting polymeric blend composition."

[0061] Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. The use of "about" or "approximately" in connection with a range applies to both ends of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", inclusive of at least the specified endpoints.

[0062] The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The term "consisting essentially of to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, ingredients, components or steps herein also contemplates embodiments that consist of, or consist essentially of the elements, ingredients, components or steps.

[0063] Plural elements, ingredients, components or steps can be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step might be divided into separate plural elements, ingredients, components or steps. The disclosure of "a" or "one" to describe an element, ingredient, component or step is not intended to foreclose additional elements, ingredients, components or steps.Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025

[0064] It is understood that the above description is intended to be illustrative and not restrictive. Many embodiments as well as many applications besides the examples provided will be apparent to those of skill in the art upon reading the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The omission in the following claims of any aspect of subject matter that is disclosed herein is not a disclaimer of such subject matter, nor should it be regarded that the inventors did not consider such subject matter to be part of the disclosed inventive subject matter.

Claims

Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 2025CLAIMSWHAT IS CLAIMED IS:

1. A handling layer comprising: a polymeric formulation that is dry to the touch in its green state; and a plurality of perforations; wherein the handling layer is able to be applied to a tacky adhesive and upon cure of the tacky adhesive and handling layer, the lap shear strength in accordance with ASTM D1002 of the handling layer and tacky adhesive is within 15% or less of the lap shear strength of the tacky adhesive without the handling layer.

2. The handling layer of claim 1 , wherein the plurality of perforations have a perforation size is in the range of from 0.02 to 2 inches (e.g., 0.5 to 50 mm).

3. The handling layer of claim 1 or claim 2, wherein the plurality of perforations are located in a perforation area having a size in the range of from 0.0004 to 15 inches2(e.g., 0.01 mm2to 381 mm2).

4. The handling layer of any of the preceding claims, wherein the plurality of perforations are located in a perforation area and the perforation area is in the range of from 3% to 75% of the total area of the entirety of the handling layer.

5. The handling layer of any of the preceding claims, wherein the perforation shape is selected from: round, triangular, square, elongated, slotted, star, crystal, houndstooth style, polygonal, hexagonal, and any combination thereof.

6. The handling layer of any of the preceding claims, wherein the distribution of perforation is aligned, staggered, or random.

7. The handling layer of any of the preceding claims, including functional substances anchored onto the perforated area.

8. The handling layer of claim 7, wherein the functional substance includes conductive steel spheres.

9. The handling layer of any of the preceding claims, wherein an adhesive including the handling layer has a wedge impact peel load that is at least 80% of the wedge impact peel load (0.030” EG60, 2 m / s impact speed, 25 kg drop weight) of the adhesive without the handling layer.

10. The handling layer of any of the preceding claims, wherein an adhesive including the handling layer has a wedge impact peel energy that is at least 80% of the wedge impact peel energy (0.030” EG60, 2 m / s impact speed, 25 kg drop weight) of the adhesive without the handling layer.Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 202511. The handling layer of any of the preceding claims, the thickness of the layer in between two perforations is the same as the original thickness of the non-perforated handling layer, and the thickness of the edge of the perforations (e.g., the wall of the perforations) is at least three times the thickness of the layer in between the two perforations.

12. The handling layer of any of the preceding claims, wherein the plurality of perforations receive metallic spheres that adhere to the adhesive and the metallic spheres allow for no shunt welding of the adhesive.

13. The handling layer of any of the preceding claims, wherein each perforation is spaced from adjacent perforations by at least 5 mm.

14. The handling layer of any of the preceding claims, wherein each perforation is spaced from adjacent perforations by at least 10 mm.

15. The handling layer of any of the preceding claims, wherein each perforation is spaced from adjacent perforations by at least 20 mm.

16. The handling layer of any of the preceding claims, wherein the handling layer comprises a Bisphenol A and cashew and nutshell liquid polymer with epichlorohydrin.

17. The handling layer of any of the preceding claims, wherein the handling layer comprises Bisphenol A and zinc oxide.

18. The handling layer of any of the preceding claims, wherein the plurality of perforations are located in a perforation area and the perforation area is in the range of at least 20% of the total area of the entirety of the handling layer.

19. A structural adhesive including a perforated handling layer disposed on a top surface of the adhesive.

20. The structural adhesive of claim 10, wherein the handling layer is in accordance with the handling layer of any of claims 1 through 8.

21. The structural adhesive of either of claims 19 or 20, wherein the adhesive comprises a Bisphenol A and cashew and nutshell liquid polymer with epichlorohydrin.

22. The structural adhesive of any of claims 19 through 21 , wherein the adhesive comprises a Bisphenol A and cashew and nutshell liquid polymer with epichlorohydrin.

23. The structural adhesive of any of claims 19 through 22, wherein the adhesive is nonexpanding.

24. The structural adhesive of any of claims 19 through 22, wherein the adhesive foams upon exposure to a stimulus.

25. The structural adhesive of any of claims 19 through 24, wherein the adhesive foams upon exposure to heat.Attorney Docket No.: 1001.935WOFiled Via USPTO.GOV on December 20, 202526. The structural adhesive of any of claims 19 through 24, wherein structural adhesive is coextruded with the handling layer.

27. A method comprising: i) extruding a structural adhesive, wherein the structural adhesive is epoxy-based; ii) forming a handling layer; iii) perforating the handling layer with a plurality of openings; iv) locating the handling layer onto one or more surfaces of the structural adhesive; v) optionally locating a plurality of metallic spheres onto the structural adhesive.

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