Piezoelectric epoxy adhesive laminate tapes

Abstract

The present invention relates to a piezoelectric epoxy adhesive laminate tape assembly. The adhesive laminate tape demonstrates excellent adhesive properties while maintaining good piezoelectric response.

Description

2024P00380PIEZOELECTRIC EPOXY ADHESIVE LAMINATE TAPESBACKGROUNDField

[0001] The present invention relates to a piezoelectric epoxy adhesive laminate tape assembly. The piezoelectric epoxy adhesive laminate tape demonstrates excellent adhesive properties while maintaining good piezoelectric response.Brief Description of Related Technology

[0002] To date, piezoelectric materials have been incorporated into adhesive resins and matrices, although with different objectives. Two common ones are: composites with piezoelectric ceramics and combination of piezoelectric and nonpiezoelectric polymers.

[0003] Piezoelectric ceramics have been mixed with polymeric resins to form composite materials. While this approach is widely known, in many cases, the polymeric resin is not used for its adhesive properties but rather as a binder. In this regard, the polymeric resin can improve the mechanical properties (otherwise, too brittle) and the processability of the piezoelectric systems (otherwise, difficult to process in general). See e.q. R.E. Newnham et al., “Connectivity and piezoelectricpyroelectric composites”, Mat. Res. Bull., Vol. 13(5), pp. 525-36 (May 1978) and K. Uchino, “Piezoelectric Composites”, Reference Module in Materials Science and Materials Engineering. Oxford: Elsevier, pp. 1-12 (2016).

[0004] Piezoelectric compositions are known to belong to a variety of different configurations. For instance, [0,3] composites, which can be cast or applied like paints, ordinarily contain a fluorinated polymer and piezoelectric particles. These composites may be cured and thereafter poled (such as under exposure to 3-5 kV / mm for a period of 10 minutes) prior to evaluating the piezoelectric properties. These composites show a piezoelectric coefficient (dss), oftentimes as high as about2024P0038030 pC / N. But, to the extent they once did, when cured the composites no longer show structural adhesive capabilities.

[0005] In addition, poling [0,3] composites can be complex and challenging. For instance, contact poling requires the use of a high applied electric field due to differences in dielectric constant (K) between the piezo particles (high K) and the surrounding polymer matrix (low K). These differences mean that the low dielectric polymer matrix shields the ceramic particles from the applied electric field, which translates to the required use of very high applied electric fields to pole the ceramic particles. The use of such high applied poling electric fields increases the likelihood of dielectric breakdown of the polymer matrix and of dielectric breakdown due to presence of defects (air bubbles, voids, fish eye, dust particles and the like) which will result in electrical shorting.

[0006] In addition, these high applied poling electric fields require a test specimen to be immersed in a silicone oil bath to minimise risk of dielectric breakdown in air. Because of this, limitations on the size of specimens and scale and practicality of contact poling a [0,3] composite film are imposed. Thus, contact poling can only be performed conveniently on small sample areas / thin films. Larger composite film areas require the use of larger applied poling electric fields, which increase the chances of shorting via defects found in larger area film.

[0007] Contact poling also requires the placement of electrodes on the composite surface. That is, a conductive metal electrode must be in full contact with the area of the composite to be poled. This can involve further difficult and expensive processing steps (such as metal (gold or silver) sputtering or use of gold metallised low roughness PET which is then pressure sandwiched onto the composite surface to ensure good surface contact of electrodes to composites). These additional processing steps preclude the use of the composite as an adhesive as the poling electrode cannot be in contact with the metal substrate to be adhesively bonded.

[0008] From a practical standpoint, it is difficult to reach an applied electric field sufficiently high enough to pole the piezo particles (typically the applied electric field2024P00380 must be much greater than the coercive field of the piezo particle to pole efficiently) which leaves the [0,3] composite with poor piezoelectric activity.

[0009] One may reduce the difference in dielectric constant of the piezo particles and the surrounding polymer matrix by for instance increasing the volume fraction of the piezo particles in the polymer matrix. But processing / dispersing such large amounts of filler into the polymer creates viscosity issues and wetting issues. These issues influence the possibility of air entrapment / voids at the fi Iler-poly mer interface, which can lead to film defects and porosity creation. These defects and porosity creation can result in dielectric breakdown and thus poor poling performance. Moreover, highly filled composites are more difficult to process, become brittle / reduced flexibility, and suffer from reduced design flexibility.

[0010] Piezoelectric materials are widely used in industry as receiver sensors (accelerometers, gyroscopes, shock wave sensors, impact sensors, stress-strain sensors and receiver transducers) and as emitters (level sensors, ultrasonic distance sensors, flow rate measurement sensors, transducers for non-destructive evaluation- SHM, sonar, hydrophones, for high intensity ultrasonic cleaning, for high intensity ultrasonic welding and as actuators). Piezoelectric materials are widely used in medical diagnosis (e.q., ultrasonic scan) and as medical tools (e.q., surgical knives, bubble detectors, aerosol production for inhalers, shock wave lithotripsy or as a cleaning tool). Consumer market applications for piezoelectric materials include speakers, pick-ups for instruments, microphones, lighters, keypads, printers, and the newly developed energy harvesters.

[0011] All of these applications have used piezoelectric materials (e.q., ceramics or polymers), which are then attached separately with adhesives.

[0012] Prior efforts in this connection include:

[0013] German Patent Document No. DE 10104605, which discloses an adhesive bond for structural members comprising a piezo particle (see the title, the abstract, claim 1) and which exemplifies the use of 56.2 percent of piezo particles and 43.8 percent of a thermoplastic polymer.2024P00380

[0014] International Patent Publication No. WO 2014 / 162976 discloses an electroacoustic transduction film, comprising a polymer composite piezoelectric body in which piezoelectric body particles are dispersed in a viscoelastic matrix formed of a polymer material having viscoelasticity at a normal temperature; and electrode layers disposed to interpose the polymer composite piezoelectric body therebetween, wherein an area fraction of the piezoelectric body particles in a contact surface with respect to the electrode layer is less than or equal to 50 percent (see the abstract, claim 1). The PCT ‘976 document exemplifies a composition comprising 75 percent of piezoelectric particles, 7.5 percent of a viscoelastic matrix and 17.5 percent of a solvent.

[0015] European Patent Document No. EP 3235016 is directed to and claims a piezoelectric adhesive composition comprising: a) from 3 percent to 30 percent of an adhesive matrix; b) from 5 to 85 percent of a piezoelectric component; and c) from 30 percent to 90 percent of a solvent, where all weight percentages are based on weight of the total weight of the composition, and where said piezoelectric component is in a piezoelectric phase.

[0016] International Patent Publication No. WO2016 / 097077 is directed to and claims an adhesive composition comprising: a) from 2 to 50 percent of an adhesive matrix; b) from 5 to 85 percent of a piezoelectric component selected from the group consisting of polyvinylidene difluoride (PVDF), polyvinylidene difluoride trifluoroethylene (P(VDF-TrFE)), polyvinylidene difluoride hexafluoropropylene (P(VDF-HFP)), polyvinylidene difluoride trifluoroethylene chlorofluoroethylene (P(VDF-TrFE-CFE)), where all weight percentages are based on weight of the total weight of the composition.

[0017] With respect to the PCT ‘077 document, observation of piezoelectric performance requires poling of the composition. And in this connection poling occurs after curing of the adhesive matrix. Once the adhesive matrix is cured no meaningful structural adhesive properties are retained. In other words, while the composition2024P00380 exhibits piezoelectric performance it no longer demonstrates any meaningful adhesive properties.

[0018] Similar to the PCT ‘077 document, U.S. Patent Application Publication No. US 2020 / 00303621 describes in sum and substance a [0,3] piezoelectric polymer composites prepared by polymerising a formulation of a dispersion of barium titanate piezo filler in a MMA monomer / HEMA monomer blend containing a radical initiator and an ionic liquid. The formulations are cast as films, allowed to cure at 60°C and corona poled, either after curing or as curing is occurring. Again, as with the PCT ‘077 document this course produces a piezoelectric polymer composite that demonstrates no meaningful adhesive properties.

[0019] JP2015186909, EP4331838, JP2020165887 and JP2015101673 each describe laminated sheets having a piezoelectric component. JP2015186909 describes a laminated sheet having a cured adhesive product which acts as a pressure-sensitive adhesive composition. In JP2015186909, the adhesive is present in an already cured state. And while such cured adhesives may function as pressure sensitive adhesives, once the adhesive is cured, they are no longer in a curable form and as such cannot cure to form bonds having structural strength. EP4331838 describes a piezoelectric laminated film with a transparent adhesive sheet for use in touch panels. JP2020165887 describes a piezoelectric laminate sheet comprising a first conductive layer, a piezoelectric layer, an adhesive layer, a release layer, and a second conductive layer. JP2015101673 describes a double-sided pressure-sensitive adhesive sheet for piezoelectric films, which has pressure-sensitive adhesive layers which acts as a pressure-sensitive adhesive composition. In these disclosures, the stickiness and viscoelastic properties of the adhesive layers provide a tack. This tackiness gives adhesion but the bonds formed provide no structural strength, such as sufficient shear or tensile strength. No meaningful structural adhesive properties are possible.

[0020] Thus, it is seen that the state of the art fails to provide a piezoelectric structure which includes an adhesive composition, where the piezoelectric structure2024P00380(1) adheres to a substrate on its own without using a separate adhesive to adhere it and (2) is able to act as an adhesive, sealant or coating, particularly a structural adhesive having good adhesion strength, while at the same time providing good piezoelectric response.SUMMARY

[0021] A solution to that failure has been provided here.

[0022] The present invention relates to a curable adhesive laminate tape comprising: a first release liner; a first adhesive composition; a piezoelectric polymer film or piezoelectric polymer composite film having: a film thickness of from about 1 pm to about 500 pm, from about 10 pm to about 150 pm, from about 20 pm to about 110 pm, or from about 25 pm to about 75 pm, a piezoelectric coefficient d33 value of from about 5 to about 40 picocoulombs / Newton (pC / N), from about 10 to about 35 pC / N, or from about 20 to about 30 pC / N, each measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001), a modulus of from about 2,000 to about 2,700 Pascals (Pa), and a dielectric constant of from about 8 to about 50, such as about 12.5 to about 13; a second adhesive composition; and a second release liner.

[0023] In the curable adhesive laminate tape of the invention, the first and / or second adhesive composition is a curable adhesive composition. Desirably each is a curable adhesive composition. Here, at least one, desirably each, of the first adhesive composition and the second adhesive composition is based on an epoxy matrix. The epoxy matrix that forms the adhesive layer(s) of the present invention is (are each) a2024P00380 curable epoxy matrix. In particular, the epoxy matrix takes the form of a curable epoxy composition within a matrix. A matrix is desirably formed by at least one film former together with the curable epoxy composition. The film former imparts a matrix form within which the curable epoxy composition remains curable. Suitable epoxy resins for use in the adhesive layer(s) / epoxy matrix of the present invention are set out below. Desirably the epoxy resins used in the adhesive layer(s) / epoxy matrix of the present invention are epoxy monomers.

[0024] When only one of the adhesive layers is an epoxy matrix, the other adhesive layer may be a curable cyanoacrylate matrix or a curable (meth)acrylate matrix. Such curable cyanoacrylate matrix or curable (meth)acrylate matrix is desirably formed by at least one film former together with a curable cyanoacrylate composition or a curable (meth)acrylate composition. The film former imparts a matrix form within which the curable epoxy composition or the curable (meth)acrylate composition remains curable. In the laminate of the invention the film former is typically in film form. In practice, the piezoelectric polymer film or piezoelectric polymer laminate film should be electroded at the upper and lower surfaces of the film.

[0025] When cured the adhesive laminate tape demonstrates one or more of the following physical properties:• lap shear strength on mild steel of from about 3.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002-10(2019);• after exposure to room temperature aging conditions for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 3.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002-10(2019),• after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 6.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002- 10(2019);• after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks, lap shear strength on mild steel2024P00380 of from about 3.0 to about 6.5 (N / mm2or MPa), when measured according to ASTM D1002-10(2019);• up to 129 percent adhesion retention on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks;• up to 59 percent d33 coefficient retention on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks;• up to 61 percent adhesion retention on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks;• up to 103 percent d33 coefficient retention on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks;• when disposed and cured between mild steel substrates a d33 coefficient across the mild steel substrates of from about 1 .5 to about 8, such as about 2 to about 8 for epoxy-based adhesive layers, after exposure to room temperature aging conditions for a period of time of 2 weeks, when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001).

[0026] The present invention relates to the use of the curable adhesive laminate tape as described herein as a sensor to monitor structural health of adhesively bonded structures.

[0027] In addition, the present invention relates to the use of a piezoelectric adhesive laminate tape as an adhesive, sealant or coating with sensorised properties suitable for condition monitoring the structural health of adhesively bonded / sealed / coated industrial assets. For example, the present invention relates to the use of a piezoelectric adhesive laminate tape as an adhesive, sealant or coating with sensorised properties suitable for condition monitoring the structural health of fluid flow pathways such as pipes. The present invention also relates to the use of the curable adhesive laminate tape of the invention as a sensor to monitor structural2024P00380 health of adhesively bonded structures. The present invention also relates to the use of a piezoelectric adhesive laminate tape according to the invention in a monitoring system, such as for fluid flow pathways, for example for monitoring pipes. Such systems comprise monitoring equipment which can detect changes to the substrate to which it is attached, for example to fluid flow pathway(s), where those changes are communicated to the monitoring equipment through the piezoelectric adhesive laminate tape according to the invention. In such cases the piezoelectric adhesive laminate tape according to the invention may be considered to be a sensor where piezoelectric changes are detected. Monitoring may be local or remote and may be wireless.

[0028] Further, the present invention also encompasses a device comprising a piezoelectric adhesive laminate tape disposed between two conductive elements.

[0029] Accordingly, an adhesive laminate tape with piezoelectric properties is provided. In this way, once constructed the adhesive tape film does not require poling to exhibit piezoelectric properties while at the same time exhibiting adhesive properties.

[0030] The present invention also encompasses a method for monitoring assets, such as in a fluid flow pathway(s), the method comprising: applying the laminate tape according to the invention to a surface of a portion of an asset such as a fluid flow pathway for example a pipe; providing monitoring equipment, such as a remote device, to receive signals generated by the piezoelectric layer of the laminate tape, and receiving generated signals for monitoring and reporting conditions in the fluid flow pathway(s). In order to apply the laminate tape according to the invention to a surface of a portion of an asset, the first and / or second release liner must be removed.

[0031] The present invention also encompasses a system for monitoring assets such as in a fluid flow pathway(s) for example in pipes. The system comprises the application of the inventive curable adhesive laminate tape, which comprises:2024P00380 a first release liner; a first adhesive composition (which may comprise an epoxy matrix); a piezoelectric polymer film or piezoelectric polymer composite film having: a film thickness of from about 1 pm to about 500 pm, a piezoelectric coefficient d33 value of from about 5 to about 40 picocoulombs / Newton (pC / N), from about 10 to about 35 pC / N, or from about 20 to about 30 pC / N, each when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001), a modulus of from about 2,000 to about 2,700 Pascals (Pa), and a dielectric constant of from about 8 to about 50; a second adhesive composition (which may comprise an epoxy matrix); and a second release liner, to a surface of a portion of a substrate such as an industrial asset including a fluid flow pathway for example a pipe. Prior to application of the inventive curable adhesive laminate tape, at least one release liner must be removed. The system may include monitoring equipment, such as a remote device, to receive signals generated by the piezoelectric layer of the laminate tape. The monitoring equipment will typically receive generated signals and utilise those for monitoring and reporting conditions in the substrate such as in an asset including a fluid pathway for example a pipe.BRIEF DESCRIPTION OF THE FIGURES

[0032] FIG. 1 illustrates a schematic diagram of a piezoelectric adhesive laminate tape according to the present invention.

[0033] FIG. 2 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient d33 value, each over time when aged at room temperature, using a piezoelectric laminated tape comprising a piezoelectric layer of 30 pm and a fixed epoxy adhesive layer of 50 pm.2024P00380

[0034] FIG. 3 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient d33 value, each over time when aged at room temperature, using a piezoelectric laminated tape comprising a piezoelectric layer of 50 pm and a fixed epoxy adhesive layer of 50 pm.

[0035] FIG. 4 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient d33 value, each over time when aged at room temperature, using a piezoelectric laminated tape comprising a piezoelectric layer of 80 pm and a fixed epoxy adhesive layer of 50 pm.

[0036] FIG. 5 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient d33 value, each over time when aged at room temperature, using a piezoelectric laminated tape comprising a piezoelectric layer of 110 pm and a fixed epoxy adhesive layer of 50 pm.

[0037] FIG. 6 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient d33 value, each over a period of time of 6 weeks when aged at room temperature, with a piezoelectric layer of 80 pm for the epoxy adhesive layers at a thickness of 30 pm.

[0038] FIG. 7 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient d33 value, each over a period of time of 6 weeks when aged at room temperature, with a piezoelectric layer of 80 pm for the epoxy adhesive layers at a thickness of 50 pm.

[0039] FIG. 8 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient, each over time, at a piezoelectric layer of 80 pm for the epoxy adhesive layers at a thickness of 100 pm.

[0040] FIG. 9 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient, each over time at a temperature of 40°C and a relative humidity of 98%, at a piezoelectric layer of 80 pm for the epoxy adhesive layers at a thickness of 100 pm.

[0041] FIG. 10 depicts visually a bar chart representing adhesive strength coupled with a curve showing piezoelectric coefficient, each over time at a2024P00380 temperature of 80°C, at a piezoelectric layer of 80 pm for the epoxy adhesive layers at a thickness of 100 pm.

[0042] FIG. 11 depicts a schematic of a system for monitoring assets. The system comprises monitoring equipment, such as signal harvesting circuitry, for use with the inventive piezoelectric adhesive laminate tape of the invention. The piezoelectric adhesive laminate tape of the invention is depicted bonded between two metal substrates (8, 9). The release I iner(s) is(are) removed such that the adhesive layer(s) in use ordinarily bonds to (or, together) one or two substrates e.g. a metal substrate as in FIG 11. In this Example, the inventive piezoelectric adhesive laminate tape of the invention is depicted as sandwiched between two metal substrates (8, 9) and comprises: a first adhesive composition (an adhesive composite layer 2); a piezoelectric polymer film or piezoelectric polymer composite film 4; a second adhesive composition (an adhesive composite layer 6). In this Example, the piezoelectric polymer film or piezoelectric polymer composite film is electroded at the upper and lower surfaces of the film via conductive electrode layers (3,5).DETAILED DESCRIPTION

[0043] As noted above, the present invention relates to a piezoelectric adhesive laminate tape. The piezoelectric adhesive laminate tape demonstrates adhesive properties and piezoelectric properties. And the piezoelectric adhesive laminate tape is curable and once cured demonstrates adhesive properties and piezoelectric properties. The piezoelectric adhesive laminate tape may also demonstrate coating and / or sealant properties depending on the application to which the laminate tape is placed. As described herein, a curable adhesive laminate tape of the invention adheres to a substrate. The substrate may be a metallic substrate, for example, steel, aluminium, copper, iron, brass, bronze, titanium, nickel, tin, zinc or lead. (Adhering to one of more substrate(s) requires removal of the first and / or second release liner.)

[0044] The piezoelectric adhesive laminate tape comprises:2024P00380 a first release liner 1; a first adhesive composition 2; a piezoelectric polymer film or piezoelectric polymer composite film 4; a second adhesive composition 6; and a second release liner 7. (See FIG. 1 .)

[0045] Here at least one, desirably each, of the first adhesive composition and the second adhesive composition is based on an epoxy composition, desirably a curable epoxy composition.

[0046] When only one of the adhesive layers is an epoxy composition, the other adhesive layer may be a cyanoacrylate matrix or a (meth)acrylate matrix, desirably a curable cyanoacrylate matrix or a curable (meth)acrylate matrix.

[0047] In practice, the piezoelectric polymer film or piezoelectric polymer composite film should be electroded at the upper and lower surfaces of the film. (See FIG. 1 , 3,5 and FIG. 11 , 3, 5.) The electrodes may be constructed from conductive materials that do not substantially interfere with the performance of the adhesive layer(s) or impair transparency when the epoxy matrix is subjected to radiation for cure. For instance, the electrodes may be constructed from conductive such as conductive organic polymers like PEDOT-PSS (blend of two distinct polymers: poly(3,4-ethylenedioxythiophene) (“PEDOT”) and polystyrene sulfonate (“PSS”)), or surface treated conductive metals. The electrodes may be constructed from copper or silver, such as in the form of a copper or silver tape or film, or as a coating.

[0048] The piezoelectric polymer film or piezoelectric polymer composite film should have:• a film thickness of from about 1 pm to about 500 pm, such as from about 10 pm to about 150 pm, desirably from about 20 pm to about 110 pm, particularly from about 25 pm to about 75 pm, optionally the film thickness may be about 30 pm, further optionally the film thickness may be about 50 pm, further optionally the film thickness may be about 80 pm, further optionally the film thickness may be about 110 pm,2024P00380• a piezoelectric coefficient CI33 value of from about 5 to about 40 picocoulombs / Newton (pC / N), such as from about 10 to about 35 pC / N, or desirably from about 20 to about 30 pC / N, each measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001), optionally the piezoelectric coefficient d33 value is from about 2 to about 15 pC / N, further optionally the piezoelectric coefficient d33 value is from about 2 to about 10 pC / N, further optionally the piezoelectric coefficient d33 value is from about 2 to about 7.5 pC / N,• a modulus of from about 2,000 to about 2,700 Pascals (Pa), and• a dielectric constant of from about 8 to about 50, such as about 12.5 to about 13.

[0049] When cured, the adhesive laminate tape demonstrates one or more of the following physical properties:• lap shear strength on mild steel of from about 3.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002-10(2019),• after exposure to room temperature aging conditions for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 3.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002-10(2019),• after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 6.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002-10(2019),• after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 3.0 to about 6.5 (N / mm2or MPa), when measured according to ASTM D1002-10(2019),• up to 129 percent adhesion retention on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks;2024P00380• up to 59 percent CI33 coefficient retention on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks;• up to 61 percent adhesion retention on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks;• up to 103 percent d33 coefficient retention on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks;• when disposed and cured between mild steel substrates a d33 coefficient across the mild steel substrates of from about 1.5 to about 8, such as about 2 to about 8 for epoxy-based adhesive layers, after exposure to room temperature aging conditions for a period of time of 2 weeks, when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001).

[0050] When cured (i.e. when the at least one curable epoxy adhesive composition has cured to a substrate), the adhesive laminate tape demonstrates one or more of the following physical properties:• lap shear strength on mild steel of from about 3.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002-10(2019), o The lap shear strength on mild steel may be from about 5.0 to about 7.5 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 30 pm. o The lap shear strength on mild steel may be from about 3.0 to about 4.5 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 50 pm.2024P00380 o The lap shear strength on mild steel may be from about 4.0 to about 6.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm. o The lap shear strength on mild steel may be from about 4.0 to about 6.0 (N / mm2) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 110 pm. o The lap shear strength on mild steel may be from about 4.0 to about 6.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 30 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm. o The lap shear strength on mild steel may be from about 4.0 to about 6.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm. o The lap shear strength on mild steel may be from about 5.0 to about 9.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 100 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm.• after exposure to room temperature aging conditions for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 3.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002-10(2019),2024P00380 The lap shear strength on mild steel after exposure to room temperature aging conditions for a period of time of up to 6 weeks may be from about 5 to about 7.5 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 30 pm. The lap shear strength on mild steel after exposure to room temperature aging conditions for a period of time of up to 6 week may be from about 3.0 to about 4.5 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 50 pm. The lap shear strength on mild steel after exposure to room temperature aging conditions for a period of time of up to 6 weeks may be from about 4.0 to about 6.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm. The lap shear strength on mild steel after exposure to room temperature aging conditions for a period of time of up to 6 week may be from about 4.0 to about 6.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 110 pm.2024P00380 o The lap shear strength on mild steel after exposure to room temperature aging conditions for a period of time of up to 6 week may be from about 4.0 to about 6.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 30 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm. o The lap shear strength on mild steel after exposure to room temperature aging conditions for a period of time of up to 6 week may be from about 4.0 to about 6.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 50 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm. o The lap shear strength on mild steel after exposure to room temperature aging conditions for a period of time of up to 6 week may be from about 5.0 to about 9.0 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 100 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm.• after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 6.0 to about 9.0 (N / mm2or MPa), when measured according to ASTM D1002-10(2019), o The lap shear strength on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks may be from about 6.0 to about 8.5 (N / mm2) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 30 pm with a piezoelectric2024P00380 polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm.• after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 3.0 to about 6.5 (N / mm2or MPa), when measured according to ASTM D1002-10(2019), o The lap shear strength on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks may be from about 3.5 to about 6.5 (N / mm2or MPa) when the laminate tape comprises at least one adhesive composition layer(s) (such as an adhesive composition comprising an epoxy matrix) of 100 pm with a piezoelectric polymer film or piezoelectric polymer composite film (e.g. PVDF layer) of 80 pm.• up to 129 percent adhesion retention on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks;• up to 59 percent d33 coefficient retention on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks;• up to 61 percent adhesion retention on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks;• up to 103 percent d33 coefficient retention on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks;• when disposed and cured between mild steel substrates a d33 coefficient across the substrates of from about 1 .5 to about 8, such as about 2 to about 8 for epoxy-based adhesive layers after exposure to room temperature aging conditions for a period of time of 2 weeks, when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001).2024P00380

[0051] The piezoelectric adhesive laminate tape according to the present invention thus demonstrates piezoelectric properties and adhesive properties.

[0052] Components of the piezoelectric adhesive laminate tape are described in detail below.Piezoelectric Component

[0053] A piezoelectric adhesive laminate tape according to the present invention comprises an organic or inorganic piezoelectric component. The piezoelectric component is sandwiched as a layer between two adhesive layers, each of whose outer surfaces which prior to use is disposed under a release liner. When the release liner(s) is(are) removed the adhesive layer(s) in use ordinarily bond to(together) one or two substrates.

[0054] In practice, the piezoelectric polymer film or piezoelectric polymer laminate film should be electroded at the upper and lower surfaces of the film. By placement of the electrodes at the respective surfaces, an electrical signal arising as a result of an applied mechanical stress / strain on the cured piezoelectric adhesive composite or bonded / sealed / coated asset may be harvested. This may be beneficial in the commercial context of monitoring fluid flow pathways. It may also be beneficial within other monitoring systems such as those monitoring industrial assets.

[0055] As noted above, the electrodes may be constructed from conductive materials that do not substantially interfere with the performance of the adhesive layer(s) or impair transparency when the epoxy matrix is subjected to radiation for cure. Desirably, the electrodes may be constructed from copper or sliver, such as in the form of a copper or silver tape or film, or as a coating.

[0056] The piezoelectric components provide novel properties to the adhesive laminate tape. Yet in carrying out the present invention, unlike technology that existed heretofore, exposure of the inventive adhesive laminate tape to poling conditions is unnecessary to achieve the so-described piezoelectric properties.

[0057] The piezoelectric component may be formed as a layer in a variety of thicknesses. For instance, the piezoelectric component may be used in a film2024P00380 thickness of from about 1 m to about 500 pm, from about 10 pm to about 150 pm, from about 20 pm to about 110 pm, or from about 25 pm to about 75 pm. Certain thicknesses - e.q., 30 pm, 50 pm, 80 pm, 100 pm, 110 pm or 120 pm -- are particularly desirable. Each of these film thicknesses for PVDF is available from PolyK Technologies, LLC, State College, PA, US. Other commercially available sources include one or more of Alfa Chemistry Fluoropolymers: PVDF Piezoelectric Film with 100 nm thick Aluminum Electrode - Fluoropolymers / Alfa Chemistry; Precision acoustics: PVDF - Precision Acoustics; GoodFellow: Piezo-electric Film PVDF Film | Goodfellow; T.E. Connectivity: Piezo Film Sheets | TE Connectivity; Arkema Piezotech; and Kureha.

[0058] In some instances, it may be desirable to include in the piezoelectric layer a piezoelectric filler, such as a ceramic powder or a polymer, which may be dissolved or dispersed, and which may have a treated surface.

[0059] The type and quantity of the piezoelectric filler added to the piezoelectric layer can have an effect on the piezoelectric response of the piezoelectric adhesive laminate tape.

[0060] Suitable commercially available piezoelectric fillers to be used in the present invention are for example PZT from T & Partners Praha, abcr GmbH and PVDF Kynar 740 from Arkema. Additional piezoelectric components may be sourced from PolyK Technologies, LLC, State College, PA, US.

[0061] The piezoelectric component comprises a piezoelectric polymer film or piezoelectric polymer composite film constructed from one or more fluorinated polymers, such as any one of the following polymers (listed here together with their respective dielectric constants): polyvinylidene difluoride -12-13 polyvinylidene difluoride trifluoroethylene -8 polyvinylidene difluoride hexafluoropropylene -10 polyvinylidene difluoride chlorofluoroethylene -20-502024P00380 polyvinylidene fluoride-co-trifluoroethylene-co- ~4.5 hexafluoropropylene polyvinylidene fluoride-co-trifluoroethylene-co- -20-50 chlorofluoroethylene

[0062] The piezoelectric component is desirably constructed from polyvinylidene difluoride. The piezoelectric component may be constructed from polyvinylidene difluoride having a thickness of 30 pm. The piezoelectric component may be constructed from polyvinylidene difl uoride having a thickness of 50 pm. The piezoelectric component may be constructed from polyvinylidene difluoride having a thickness of 80 pm. The piezoelectric component may be constructed from polyvinylidene difluoride having a thickness of 110 pm.Adhesive Layerts)

[0063] A piezoelectric adhesive laminate tape according to the present invention comprises at least two adhesive layers. The adhesive layer(s) sandwich the piezoelectric component in the form of a layer. The adhesive layer(s) may be provided at a thickness of about 10 pm to about 200 pm, preferably about 20 pm to about 150 pm. The adhesive layer(s) may be provided at a thickness of about 30 pm. The adhesive layer(s) may be provided at a thickness of about 50 pm. The adhesive layer(s) may be provided at a thickness of about 100 pm.

[0064] The adhesive layer(s) used in the piezoelectric adhesive laminate tape may be selected from epoxies. In the piezoelectric adhesive laminate tape of the invention, the adhesive layer comprises an epoxy matrix, wherein the epoxy matrix is a curable epoxy matrix. In particular, the epoxy matrix takes the form of a curable epoxy composition within a matrix. A matrix is desirably formed by at least one film former together with the curable epoxy composition. The film former imparts a matrix form within which the curable epoxy composition remains curable. In other words, once the film former has formed a film, the epoxy composition remains curable. Therefore, once assembled in the curable adhesive laminate tape according to the2024P00380 invention, the film former in the epoxy adhesive composition will have already formed a film. Desirably the epoxies used in the adhesive layer(s) / epoxy matrix of the present invention are epoxy monomers.

[0065] In this regard, the epoxy matrix can be pre-applied to an article and then later cured. The epoxy matrix may be tacky when uncured. When only one of the adhesive layers is an epoxy matrix, the other adhesive layer may be a cyanoacrylate matrix or a (meth)acrylate matrix, desirable a curable cyanoacrylate matrix or a curable (meth)acrylate matrix. Such curable cyanoacrylate matrix or curable (meth)acrylate is desirably formed by at least one film former as described herein together with a curable cyanoacrylate matrix or a curable (meth)acrylate composition.

[0066] Suitable epoxy resins (or an oxetane matrix, the 4 membered ring counterpart of an epoxy or an oxirane, which is a 3 membered ring) for use in the present invention are selected from aliphatic, cycloaliphatic, and aromatic epoxy resins, as well as hydrogenated aromatic epoxy resins.

[0067] The epoxy resin component can include a single material or mixture of materials (e.q., monomeric, oligomeric, or polymeric compounds) selected to provide the desired viscosity characteristics before curing and while B staged, and to provide the desired mechanical properties after curing. If the epoxy resin includes a mixture of materials, at least one of the epoxy resins in the mixture is usually selected to have at least two oxirane groups per molecule. For example, a first epoxy resin in the mixture can have two to four or more oxirane groups and a second epoxy resin in the mixture can have one to four oxirane groups. In some of these examples, the first epoxy resin is a first glycidyl ether with two to four glycidyl groups and the second epoxy resin is a second glycidyl ether with one to four glycidyl groups.

[0068] Although the constituents of the epoxy resin component can have any suitable molecular weight, the weight average molecular weight of at least one of those constituents is usually high enough so that a solid adhesive film may be formed that retains structural adhesive properties. The weight average molecular weight can be up to 50,000 grams / mole or even higher for polymeric epoxy resins. The weight2024P00380 average molecular weight is often up to 40,000 grams / mole, up to 20,000 grams / mole, up to 10,000 grams / mole, up to 5,000 grams / mole, up to 3,000 grams / mole, or up to 1 ,000 grams / mole. For example, the weight average molecular weight can be in the range of 100 to 50,000 grams / mole, in the range of 100 to 20,000 grams / mole, in the range of 10 to 10,000 grams / mole, in the range of 100 to 5,000 grams / mole, in the range of 200 to 5,000 grams / mole, in the range of 100 to 2,000 grams / mole, in the range of 200 to 2,000 grams / mole, in the range of 100 to 1 ,000 grams / mole, or in the range of 200 to 1 ,000 grams / mole.

[0069] Suitable epoxy resins may be liquid at room temperature; however, solid epoxy resins that can be dissolved in one of the other components of the composition, such as a liquid epoxy resin, can be used if desired. The term “solid” means in a solid state within the temperature range of from about 5°C to 40°C, suitably in a solid state at room temperature and at atmospheric pressure. Solid state is defined as the state of matter in which materials are not fluid but retain their boundaries without support, the atoms or molecules occupying fixed positions with respect to each other and unable to move freely. Desirably, the epoxy resin is in the solid phase at room temperature.

[0070] Glycidyl ethers may be used, particularly those of Formula (I).

[0071] In Formula (I), R1is a polyvalent group that is aromatic, aliphatic, or a combination thereof, and can be linear, branched, cyclic, or a combination thereof. R1can optionally include halo groups, oxy groups, thio groups, carbonyl groups, carbonyloxy groups, carbonylimino groups, phosphono groups, sulfono groups, nitro groups, nitrile groups, and the like. Although the variable p can be any suitable integer greater than or equal to 2, p is often an integer in the range of 2 to 10, in the range of 2 to 6, or in the range of 2 to 4.2024P00380

[0072] The epoxy resin may be a polyglycidyl ether of a polyhydric phenol, such as polyglycidyl ethers of bisphenol A, bisphenol F, bisphenol AD, catechol, and resorcinol. In some embodiments, the epoxy resin is a reaction product of a polyhydric alcohol with epichlorohydrin. Exemplary polyhydric alcohols include butanediol, polyethylene glycol, and glycerin. In some embodiments, the epoxy resin is an epoxidised (poly)olefi nic resin, epoxidised phenolic novolac resin, epoxidised cresol novolac resin, and cycloaliphatic epoxy resin. In some embodiments, the epoxy resin is a glycidyl ether ester, such as that which can be obtained by reacting a hydroxycarboxylic acid with epichlorohydrin, or a polyglycidyl ester, such as that which can be obtained by reacting a polycarboxylic acid with epichlorohydrin. In some embodiments, the epoxy resin is a urethane-modified epoxy resin. In some embodiments, the epoxy resin is epoxidised fused alicyclic resins, such as those available under the tradename EPOCHALIC like the EPOCHALIC resins THI-DE, DE- 102, and DE-103, each from Kowa Chemical. Various combinations of two or more epoxy resins can be used if desired.

[0073] In some exemplary epoxy resins of Formula (I), p is 2 (i.e., the epoxy resin is a diglycidyl ether) and R1includes an alkylene (i.e., an alkylene is a divalent radical of an alkane and can be referred to as an alkane-diyl), heteroalkylene (i.e., a heteroalkylene is a divalent radical of a heteroalkane and can be referred to as a heteroalkane-diyl), arylene (i.e., a divalent radical of an arene compound), or combination thereof. Suitable alkylene groups often have 1 to 20 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. Suitable heteroalkylene groups often have 2 to 50 carbon atoms, 2 to 40 carbon atoms, 2 to 30 carbon atoms, 2 to 20 carbon atoms, 2 to 10 carbon atoms, or 2 to 6 carbon atoms with 1 to 10 heteroatoms, 1 to 6 heteroatoms, or 1 to 4 heteroatoms. The heteroatoms in the heteroalkylene can be selected from oxy, thio, or — NH — groups but are often oxy groups. Suitable arylene groups often have 6 to 18 carbon atoms or 6 to 12 carbon atoms. For example, the arylene can be phenylene or biphenylene. R1can further optionally include halo groups, oxy groups, thio groups, carbonyl2024P00380 groups, carbonyloxy groups, carbonylimino groups, phosphono groups, sulfono groups, nitro groups, nitrile groups, and the like. P is usually an integer in the range of 2 to 4.

[0074] Some epoxy resins of Formula (I) are diglycidyl ethers where R1includes (a) an arylene group or (b) an arylene group in combination with an alkylene, heteroalkylene, or both. Group R1can further include optional groups such as halo groups, oxy groups, thio groups, carbonyl groups, carbonyloxy groups, carbonylimino groups, phosphono groups, sulfono groups, nitro groups, nitrile groups, and the like. These epoxy resins can be prepared, for example, by reacting an aromatic compound having at least two hydroxyl groups with an excess of epichlorohydrin. Examples of useful aromatic compounds having at least two hydroxyl groups include resorcinol, catechol, hydroquinone, p,p'-dihydroxydibenzyl, p,p'- dihydroxyphenylsulfone, p,p'-dihydroxybenzophenone, 2,2'-dihydroxyphenyl sulfone, and p,p'-dihydroxybenzophenone.

[0075] Some commercially available diglycidyl ether epoxy resins of Formula (I) are derived from bisphenol A (i.e., bisphenol A is 4,4'-dihydroxydiphenylmethane). Examples include those available under the trade designation EPON (e.q., EPON 1510, EPON 1310, EPON 828, EPON 872, EPON 1001 , EPON 1004, and EPON 2004) from Hexion Specialty Chemicals, Inc. (Columbus, OH), those available under the trade designation DER (e.q., DER 331 , DER 332, DER 336, and DER 439) from Olin Epoxy Co. (St. Louis, MO), and those available under the trade designation EPICLON (e.q., EPICLON 850) from Dainippon Ink and Chemicals, Inc. (Parsippany, NJ). Other commercially available diglycidyl ether epoxy resins are derived from bisphenol F (i.e., bisphenol F is 2,2'-dihydroxydiphenylmethane). Examples include, those available under the trade designation DER (e.q., DER 334) from Olin Epoxy Co. (St. Louis, MO), those available under the trade designation EPICLON (e.g., EPICLON 830) from Dainippon Ink and Chemicals, Inc. (Parsippany, NJ), and those available under the trade designation ARALDITE (e.q., ARALDITE 281) from Huntsman Corporation (The Woodlands, TX).2024P00380

[0076] Other epoxy resins of Formula (I) are diglycidyl ethers of a poly(alkylene oxide) diol. Here, p is 2 and R1is a heteroalkylene having oxygen heteroatoms. The poly(alkylene glycol) portion can be a copolymer or homopolymer and often includes alkylene units having 1 to 4 carbon atoms. Examples include diglycidyl ethers of poly(ethylene oxide) diol, diglycidyl ethers of polypropylene oxide) diol, and diglycidyl ethers of poly(tetramethylene oxide) diol. Epoxy resins of this type are commercially available from Polysciences, Inc. (Warrington, PA) such as those derived from a poly(ethylene oxide) diol or from a polypropylene oxide) diol having a weight average molecular weight of 400 grams / mole, about 600 grams / mole, or about 1000 grams / mole.

[0077] Still other epoxy resins of Formula (I) are diglycidyl ethers of an alkane diol (R' is an alkylene and the variable p is equal to 2). Examples include a diglycidyl ether of 1 ,4-dimethanol cyclohexyl, diglycidyl ether of 1 ,4-butanediol, and a diglycidyl ether of the cycloaliphatic diol formed from a hydrogenated bisphenol A such as those commercially available under the trade designation EPONEX (e.q., EPONEX 1510) from Hexion Specialty Chemicals, Inc. (Columbus, OH) and under the trade designation EPALLOY (e.q., EPALLOY 5001) from CVC Thermoset Specialties (Moorestown, NJ).

[0078] The epoxy resins may be novolac epoxy resins, which are glycidyl ethers of phenolic novolac resins. These resins can be prepared, for example, by reaction of phenols with an excess of formaldehyde in the presence of an acidic catalyst to produce the phenolic novolac resin. Novolac epoxy resins are then prepared by reacting the phenolic novolac resin with epichlorohydrin in the presence of sodium hydroxide. The resulting novolac epoxy resins typically have more than two oxirane groups and can be used to produce cured coating compositions with a high crosslinking density. The use of novolac epoxy resins can be particularly desirable in applications where corrosion resistance, water resistance, chemical resistance, or a combination thereof is desired. One such novolac epoxy resin is poly[(phenyl glycidyl ether)-co-formaldehyde]. Other suitable novolac resins are commercially available2024P00380 under the trade designation ARALDITE (e.g., ARALDITE GY289, ARALDITE EPN 1183, ARALDITE EP 1179, ARALDITE EPN 1139, and ARALDITE EPN 1138) from Huntsman Corporation (The Woodlands, TX), under the trade designation EPALLOY (e.g., EPALLOY 8230) from CVC Thermoset Specialties (Moorestown, NJ), and under the trade designation DEN (e.g., DEN 424 and DEN 431) from Olin Epoxy Co. (St. Louis, MO), and EPON Resin SU-8 from Hexion Specialty Chemicals, Inc. (Columbus, OH).

[0079] Yet other epoxy resins include silicone resins with at least two glycidyl groups and flame retardant epoxy resins with at least two glycidyl groups (e.g., a brominated bisphenol-type epoxy resin having at least two glycidyl groups such as that commercially available from Dow Chemical Co. (Midland, Ml) under the trade designation DER 580).

[0080] Blending a film former with an epoxy resin, such as a solid epoxy resin, may be performed by any means known to those skilled in the art, such as melt blending or dissolution in an appropriate solvent or reactive diluent, by way of example. Solvent-borne systems can be coated and dried to yield the film adhesive product; melt blends can be extruded or hot melt coated.

[0081] Typical film formers for use with the epoxy matrix include polyesters, polyurethanes, polyimides, siloxane polyimides, polyamides, rubbers such as styrenebutadiene rubber (“SBR”), nitrile rubber (“NBR”), carboxy-terminal nitrile rubber (“CTBN”), ethylene-propylene-diene monomer copolymer (“EPDM”), polybutadiene rubber, polyisoprene rubber, poly(styrene-butadiene-styrene) block copolymer (“SBS”), poly(styrene-isoprene-styrene) block copolymer (“SIS”), styrene-b-ethylene- co-butylene-b styrene block copolymer (“SEBS”), styrene-b-ethylene-co-propylene-b- styrene block copolymer (“SEPS”), ethylene co-vinyl acetate, polyvinyl butyrals (such as those available commercially under the trade name BUTVAR), cellulose-based film formers as well as acrylic polymers, all by way of example. The film former may contain functionality that is reactive with the epoxy resin. Alternatively, the film former may be non-reactive. Polyester resins, such as those available commercially under2024P00380 the trade names DYNACOLL (available commercially from Evonik) and VITEL (available commercially from Bostik), are particularly desirable.

[0082] A solid thermoplastic polyvinyl butyral resin may act as a film former. The solid thermoplastic polyvinyl butyral resin may have a molecular weight Mw in the range of from about 40,000 g / mol to about 250,000 g / mol, suitably in the range of from about 40,000 g / mol to about 170,000 g / mol, such as about 40,000 g / mol to 120,000 g / mol, for example 50,000 g / mol to 80,000 g / mol, wherein the molecular weight Mw is as determined in accordance with ASTM D5296-05 (Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography).

[0083] Polyvinyl butyral (PVB) is a thermoplastic polymer prepared by hydrolysis of polyvinyl acetate and subsequent condensation with butyraldehyde. The polymer contains hydroxyl, acetyl and butyraldehyde functional groups and its generic chemical structure is depicted below:

[0084] PVB is commercially available as different grades with varying molecular weight and different hydroxyl, acetyl and butyraldehyde contents i.e. , different x, y, z values and which determine their physical and chemical properties. Commercially available solid thermoplastic polyvinyl butyral resins include those sold under the trade name ButvarTM by Eastman Chemical Company, or MowitalTM by Kuraray Europe GmbH.2024P00380

[0085] Suitable solid thermoplastic polyvinyl butyral resins include Butvar® B- 79, available from Eastman. Butvar® B-79 is a solid thermoplastic polyvinyl butyral resin having a molecular weight of 50,000-80,000 (size exclusion chromatography with low angle laser light scattering standard) and a softening point in the range of 140-200 °C. Other suitable commercial solid thermoplastic polyvinyl butyral resins may include Butvar® B-72, Butvar® B-74, Butvar® B-76, Butvar® B-90, and Butvar® B-98, available from Eastman.

[0086] Other suitable solid thermoplastic polyvinyl butyral resins include Mowital B30 HH, available from Kuraray. Mowital B30 HH is a solid thermoplastic polyvinyl butyral resin having a molecular weight of 50,000 -70,000 and a softening range of 140-180°C. Other suitable commercial solid thermoplastic polyvinyl butyral resins may include Mowital B20 H, B30 T, B30 H, B45 H, B60 T, B60 H, and B60 HH.

[0087] The solid thermoplastic polyvinyl butyral resin may have a softening point in the range of from about 80°C to about 300 °C, suitably from about 100 °C to about 250 °C, preferably from about 140 °C to about 200 °C.

[0088] The solid thermoplastic polyvinyl butyral resin may be present in an amount of from about 10 wt% to about 50 wt%, based on the total weight of the curable adhesive composition, suitably in an amount of from about 15 wt% to about 40 wt% based on the total weight of the curable adhesive composition, such as from about 15 wt% to about 35 wt%, for example about 20 wt% based on the total weight of the curable composition.

[0089] Compositions comprising less than about 10 wt% of the solid thermoplastic polyvinyl butyral resin tend to have insufficient elastomeric properties to allow the composition to be adequately applied to a part to be bonded. Compositions comprising greater than about 50 wt% of the solid thermoplastic polyether polyurethane component tend to exhibit poor adhesive properties. When the solid thermoplastic polyether polyurethane resin is present in an amount of from about 10 wt% to about 50 wt%, based on the total weight of the curable composition this provides the composition with an acceptable balance between adhesive performance2024P00380 and a composition that can form a coating with sufficient elastomeric properties to allow application of the composition to a part to be bonded.

[0090] Thermoplastic polyurethanes (“TPUs”) may also be used as the film former in connection with the epoxy within the epoxy matrix. The film forming polymer component may alternatively or additionally comprise a thermoplastic polyurethane which is activatable by UV radiation, for example a thermoplastic polyurethane that comprises at least one acrylate group, at least one methacrylate group or at least one acrylamide group.

[0091] TPUs in this connection are typically multi-block copolymers with hard and soft segments that can be produced by a poly addition reaction of an isocyanate with a linear polymer polyol and a low molecular weight diol as a chain extender. The soft segments form an elastomer matrix thereby affording the polymer elastic properties. The hard segments typically act as multifunctional tie points that function both as physical crosslinks and reinforcing fillers. See U.S. Patent No. 11 ,299,651 (Barnes), the disclosure of which is hereby incorporated by reference in its entirety, and GB Patent Nos. 2601776 and 2622417.

[0092] Solid thermoplastic polyurethane resins typically have a molecular weight in the range of from 40,000 g / mol to 100,000 g / mol, wherein the molecular weight Mw is as determined in accordance with ASTM D5296-05 (Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography), and a melting point in the range of from 40°C to 80°C; and a curing component for curing the anaerobically curable components. Suitable solid thermoplastic polyurethane resins include Pearlbond® 100, Pearlbond® 106, Pearlbond® 120, Pearlbond® 122, Pearlbond® 180, Pearlstick® 5712, Pearlstick® 5714 and Pearlstick® 40-70 / 08 which are commercially available from Lubrizol, Carrer del Gran Vial, 17, 08160 Montmelo, Barcelona, Spain.

[0093] One group of elastomeric polymers that may be used as film formers are copolymers of methyl acrylate and ethylene, manufactured by DuPont, under the2024P00380 name of VAMAC, such as VAMAC N123 and VAMAC B-124. VAMAC N123 and VAMAC B-124 are reported by DuPont to be a master batch of ethylene / acrylic elastomer. The DuPont material VAMAC G is a similar copolymer, though with no fillers to provide color or stabilizers. VAMAC VCS rubber appears to be the base rubber, from which the remaining members of the VAMAC product line are compounded. VAMAC VCS (also known as VAMAC MR) is a reaction product of the combination of ethylene, methyl acrylate and monomers having carboxylic acid cure sites, which once formed is then substantially free of processing aids (such as the release agents octadecyl amine, complex organic phosphate esters and / or stearic acid), and anti-oxidants (such as substituted diphenyl amine).

[0094] DuPont provides to the market under the trade designation VAMAC VMX 1012 and VCD 6200, rubbers which are made from ethylene and methyl acrylate. It is believed that the VAMAC VMX 1012 rubber possesses little to no carboxylic acid in the polymer backbone. Like the VAMAC VCS rubber, the VAMAC VMX 1012 and VCD 6200 rubbers are substantially free of processing aids such as the release agents octadecyl amine, complex organic phosphate esters and / or stearic acid, and anti-oxidants, such as substituted diphenyl amine, noted above. All of these VAMAC elastomeric polymers are useful herein.

[0095] Poly(e-caprolactone) may also be used as a film former in connection with epoxies, particularly those in the liquid phase.

[0096] Copolymers of polyethylene and polyvinyl acetate, available commercially under the trade name LEVAMELT from Arlanxeo are also useful. A range of LEVAMELT -branded copolymers are available and includes for example, LEVAMELT 400, LEVAMELT 600 and LEVAMELT 900. The LEVAMELT products differ in the amount of vinyl acetate present. For example, LEVAMELT 400 comprises an ethylene-vinyl acetate copolymer comprising 40 weight percent vinyl acetate. The LEVAMELT products are supplied in granular form. The granules are almost colourless and dusted with silica and talc. LEVAMELT consists of methylene units forming a saturated main chain with pendant acetate groups. The presence of a fully2024P00380 saturated main chain is an indication that LEVAMELT-branded copolymers are particularly stable; they do not contain any reactive double bonds which make conventional rubbers prone to aging reactions, ozone and UV light. The saturated backbone is reported to make the polymer robust.

[0097] LEVAPREN-branded copolymers may also be used. According to the manufacturer, Arlanxeo, LEVAPREN-branded copolymers consist of methylene units forming a saturated polymer backbone with pendant acetate groups. These rubberlike copolymers are designated as ethylene-vinyl acetate copolymers, or EVM. These ethylene-vinyl acetate copolymers are used as synthetic rubbers, or as modifiers in thermoplastics, specifically PVC. Multiple LEVAPREN-branded copolymers are available commercially with each one designated based on its vinyl acetate content in the copolymer. For instance, LEVAPREN 400 (40% vinyl acetate), 450 (45% vinyl acetate), 500 (50% vinyl acetate), 600 (60% vinyl acetate), 700 (70% vinyl acetate), 800 (80% vinyl acetate), and 900 (90% vinyl acetate), are now commercially available. Some of these grades are offered with different viscosities within the same grade. The LEVAPREN-branded copolymer is desirably LEVAPREN 900, which is Ethylene-vinyl acetate copolymer (EVM) with 90 wt % vinyl acetate.

[0098] VINNOL surface coating resins available commercially from Wacker Chemie AG, Munich, Germany represent a broad range of vinyl chloride-derived copolymers and terpolymers that are promoted for use in different industrial applications. The main constituents of these polymers are different compositions of vinyl chloride and vinyl acetate. The terpolymers of the VINNOL product line additionally contain carboxyl or hydroxyl groups.

[0099] VINNOL surface coating resins with carboxyl groups are terpolymers of vinyl chloride, vinyl acetate and dicarboxylic acids, varying in terms of their molar composition and degree and process of polymerization. These terpolymers are reported to show excellent adhesion, particularly on metallic substrates.2024P00380

[0100] VINNOL surface coating resins with hydroxyl groups are copolymers and terpolymers of vinyl chloride, hydroxyacrylate and dicarboxylate, varying in terms of their composition and degree of polymerization.

[0101] VINNOL surface coating resins without functional groups are copolymers of vinyl chloride and vinyl acetate of variable molar composition and degree of polymerization.

[0102] VINNOL H 40 / 60, as an example, is reported by the manufacturer as 61 .0 ± 1 .0:39.0 ± 1 .0 vinyl chloride to vinyl acetate, with the following physical properties: K value of 60 ± 1 (by EN ISO 1628-2); molecular weight of 100 - 140 x 103 Mw by size exclusion chromatography (with THF as a solvent and polystyrene as a standard); viscosity of 180 ± 30; particle size of < 1 ; and a Tg of about 62 °C (by DSC).

[0103] The film can also be formed by using a UV curing step with an epoxy- (meth)acrylate resin blend, where the UV step cures the (meth)acrylate portion to give a reactive epoxy tape. Or the film can also be formed with a blend of epoxy containing (meth)acrylate resins and a photoinitiator to cure the (meth)acrylate resins to a curable epoxy adhesive film / tape. See e.q. U.S. Patent No. 11 ,884,850. The photoinitiator may desirably be a photoinitiator containing a mixture of triarylsulfonium hexafluoroantimonate salts in propylene carbonate, which may be sold under the trade name UVI-6976.

[0104] The identity, characteristics, functionality, if any, and other specific properties of the film former may vary based on the particular processing conditions, and that the selection of the appropriate film former in any particular case is within the ability of one of ordinary skill in the art.

[0105] The epoxy and the film former should be used in a relative amount of at least about 1 :1 by weight ratio, desirably up to about a 3:1 by weight ratio epoxy:film former, such as about a 2:1 by weight ratio epoxy:film former.

[0106] The film formers oftentimes are dissolved in a solvent or a suitable liquid carrier to permit processing the epoxy matrix into an adhesive layer. The processing2024P00380 may be done by solvent casting the epoxy matrix and subsequently removing the solvent, either actively or passively. Suitable solvents include those that do not substantially interfere with the performance of the adhesive layer(s), such as acetone, ethyl acetate, and methyl ethyl ketone (“MEK”). The solvent may desirably be ethyl acetate.

[0107] A variety of additives may be included in the epoxy matrix, such as the following materials in an amount of up to about 10 percent by weight of the total weight of the composition: surface active agents, surfactants, wetting agents, antioxidants, thixotropy agents, reinforcement fibers, silane functional perfluoroether, phosphate functional perfluoroether, titanates, waxes, phenol formaldehyde, air release agents, flow additives, adhesion promoters, rheology modifiers, spacer beads, toughening agents, fillers, plasticizers and the like, examples of all of which are known to those of skill in the art.

[0108] For instance, as regards toughening agents, examples include a variety of materials, such as those available commercially under the tradename HYCAR.

[0109] Also, various commercially available rubber particles, such as core shell rubbers, may be used.

[0110] Rubber particles, especially rubber particles that have relatively small average particle size (e.q., less than about 500 nm or less than about 200 nm), may also be included. The rubber particles may or may not have a shell common to known core-shell structures.

[0111] In the case of rubber particles having a core-shell structure, such particles generally have a core comprised of a polymeric material having elastomeric or rubbery properties (i.e., a glass transition temperature less than about 0°C, e.q., less than about -30°C) surrounded by a shell comprised of a non-elastomeric polymeric material (i.e., a thermoplastic or thermoset / crosslinked polymer having a glass transition temperature greater than ambient temperatures, e.q., greater than about 50°C). For example, the core may be comprised of a diene homopolymer or copolymer (for example, a homopolymer of butadiene or isoprene, a copolymer of2024P00380 butadiene or isoprene with one or more ethy lenical ly unsaturated monomers such as vinyl aromatic monomers, (meth)acrylonitrile, (meth)acrylates, or the like) while the shell may be comprised of a polymer or copolymer of one or more monomers such as (meth)acrylates (e.q., methyl methacrylate), vinyl aromatic monomers (e.q., styrene), vinyl cyanides (e.q., acrylonitrile), unsaturated acids and anhydrides (e.q., acrylic acid), (meth)acrylamides, and the like having a suitably high glass transition temperature. Other rubbery polymers may also be suitably be used for the core, including polybutylacrylate or polysiloxane elastomer (e.q., polydimethylsiloxane, particularly crosslinked polydimethylsiloxane).

[0112] Typically, the core will comprise from about 50 to about 95 weight percent of the rubber particles while the shell will comprise from about 5 to about 50 weight percent of the rubber particles.

[0113] Preferably, the rubber particles are relatively small in size. For example, the average particle size may be from about 0.03 to about 2 microns or from about 0.05 to about 1 micron. The rubber particles may have an average diameter of less than about 500 nm, such as less than about 200 nm. For example, the coreshell rubber particles may have an average diameter within the range of from about 25 to about 200 nm.

[0114] When used, these core shell rubbers allow for toughening to occur in the composition and oftentimes in a predictable manner — in terms of temperature neutrality toward cure - because of the substantial uniform dispersion, which is ordinarily observed in the core shell rubbers as they are offered for sale commercially.

[0115] In the case of those rubber particles that do not have such a shell, the rubber particles may be based on the core of such structures.

[0116] Desirably, the rubber particles are relatively small in size. For example, the average particle size may be from about 0.03 pm to about 2 pm or from about 0.05 pm to about 1 pm. In certain embodiments of the invention, the rubber particles have an average diameter of less than about 500 nm. In other embodiments, the average particle size is less than about 200 nm. For example, the rubber particles2024P00380 may have an average diameter within the range of from about 25 nm to about 200 nm or from about 50 nm to about 150 nm.

[0117] The rubber particles may be used in a dry form or may be dispersed in a matrix, as noted above.

[0118] Typically, the epoxy composition may contain from about 5 to about 35 weight percent rubber particles.

[0119] Combinations of different rubber particles may advantageously be used in the present invention. The rubber particles may differ, for example, in particle size, the glass transition temperatures of their respective materials, whether, to what extent and by what the materials are functionalized, and whether and how their surfaces are treated.

[0120] Rubber particles that are suitable for use in the present invention are available from commercial sources. For example, rubber particles supplied by Eliokem, Inc. may be used, such as NEP R0401 and NEP R401 S (both based on acrylonitrile / butadiene copolymer); NEP R0501 (based on carboxylated acrylonitrile / butadiene copolymer; CAS No. 9010-81-5); NEP R0601A (based on hydroxy-terminated polydimethylsiloxane; CAS No. 70131-67-8); and NEP R0701 and NEP 0701 S (based on butadiene / styrene / 2-vinylpyridine copolymer; CAS No. 25053- 48-9). Also those available under the PARALOID tradename, such as PARALOID 2314, PARALOID 2300, and PARALOID 2600, from Dow Chemical Co. (Philadelphia, PA), and those available under the STAPHYLOID tradename, such as STAPHYLOID AC-3832, from Ganz Chemical Co., Ltd. (Osaka, Japan).

[0121] Rubber particles that have been treated with a reactive gas or other reagent to modify the outer surfaces of the particles by, for instance, creating polar groups (e.q., hydroxyl groups, carboxylic acid groups) on the particle surface, are also suitable for use herein. Illustrative reactive gases include, for example, ozone, C , F2, O2, SO3, and oxidative gases. Methods of surface modifying rubber particles using such reagents are known in the art and are described, for example, in U.S. Patent Nos. 5,382,635; 5,506,283; 5,693,714; and 5,969,053, each of which being2024P00380 hereby expressly incorporated herein by reference in its entirety. Suitable surface modified rubber particles are also available from commercial sources, such as the rubbers sold under the tradename VISTAMER by Exousia Corporation.

[0122] Where the rubber particles are initially provided in dry form, it may be advantageous to ensure that such particles are well dispersed in the adhesive composition prior to curing the adhesive composition. That is, agglomerates of the rubber particles are preferably broken up so as to provide discrete individual rubber particles, which may be accomplished by intimate and thorough mixing of the dry rubber particles with other components of the adhesive composition.

[0123] Rubber particles in the form of core-shell impact modifier may be prepared by emulsion polymerization. For example, a suitable method is a two-stage polymerization technique in which the core and shell are produced in two sequential emulsion polymerization stages. If there are more shells another emulsion polymerization stage follows. A graft copolymer is obtained by graft-polymerizing a monomer or monomer mixture containing at least an aromatic vinyl, alkyl methacrylate or alkyl acrylate in the presence of a latex containing a butadiene-based rubber polymer. Commercially available examples of such core-shell impact modifiers are available commercially under the CLEARSTRENGTH tradename from Arkema Inc. (Cary, NC). Arkema describes CLEARSTRENGTH XT100, for instance, as a methyl methacrylate-butadiene-styrene core-shell toughening agent, which is compatible with various monomers and easily dispersible in most liquid resin systems, and exhibits a limited impact on their viscosity while providing a toughening effect over a wide range of service temperatures.

[0124] Cure systems for the epoxy (or oxetane) matrix may include one or more nitrogen-containing compounds, such as amines like aliphatic or aromatic amines as shown, for example in U.S. Patent Nos. 4,139,524 and 4,162,358, or imidazole or imidazole derivatives, provided that the cure system operates at an appropriate temperature to cure the epoxy matrix and to not compromise the2024P00380 piezoelectric properties of the piezoelectric polymer film or piezoelectric laminate polymer film.

[0125] Other suitable cure systems include latent hardeners, such as those available commercially from Ajinomoto Fine Chemical, Japan under the tradenames AMICURE or AJICURE, like PN-23 and PN-H; Evonik under the tradename ANCAMINE, such as 2441 / 2442; Shikoku such as FXR-1020 / 1081 ; the NOVACURE HX series from Asahi Kasei; polyamine-anhydride adducts such as Ciba HT-9506. Thermal or UV cationic epoxy curatives can also be used, such as the blocked acids available commercially from Nacure or from King Industries, or sulfonium or iodonium salts. Dicyanodiamide (“DICY”) is another curative that can be used.

[0126] The amount of the cure system for the epoxy (or oxetane) matrix should be in an amount of from 0.5 percent by weight to 30 percent by weight of the total weight of the composition, preferably from 1 percent by weight to 20 percent by weight, more preferably from 1 percent by weight to 8 percent by weight of the total weight of the composition.

[0127] Desirably, the epoxy matrix may comprise an epoxy resin, such as a polymer with (chloromethyl)oxirane and 4,4'-(1-methylethylidene)bis[phenol], which may be sold under the trade name EPON SU-8 and ethylene-vinyl acetate copolymer (EVM) with 90 wt % vinyl acetate, such as that sold under the trade name LEVAPREN 900 as the film former. The epoxy matrix may further comprise an aliphatic d igly cidylether, such as the diglycidyl ether of 1 ,4-butanediol, which may be sold under the trade name EPODIL 750. The epoxy matrix may further comprise a photoinitiator such as a photoinitiator containing a mixture of triarylsulfonium hexafluoroantimonate salts in propylene carbonate, which may be sold under the trade name UVI-6976.

[0128] The piezoelectric adhesive tape laminate according to the present invention can be used as an adhesive, sealant or coating, particularly a structural adhesive having good adhesion strength, while at the same time providing good piezoelectric response.2024P00380

[0129] By the term structural adhesive is meant herein an adhesive, which is a relatively strong adhesive that is normally used below its glass transition temperature, such an adhesive can carry significant stresses, and lend itself to structural applications, wherein the adhesive plays as a part of the physical structure of joined surfaces.

[0130] In contrast to the application of the piezoelectric adhesive composition onto the surface of the conductive element according to International Patent Publication No. WO 2016 / 0977077 where these steps are followed:1) applying the piezoelectric adhesive composition according to the present invention onto the surface of conductive element;2) evaporating the solvent (if present);3) curing the adhesive composition;4) annealing; and5) poling; or these steps are followed:1) applying the piezoelectric adhesive composition according to the present invention onto the surface of conductive element;2) evaporating the solvent (if present);3) applying second conductive element top of the piezoelectric adhesive layer;4) curing the adhesive composition;5) annealing; and6) poling, practicing the present invention involves the formation and use of the inventive piezoelectric adhesive tape laminate.

[0131] The known methods set forth in International Patent Publication No. WO 2016 / 0977077 are useful in forming the comparative [0,3] composites, as described in the examples below. But those known methods are not useful in forming the inventive [2,2] composites.2024P00380

[0132] In contrast to that which is described in International Patent Publication No. WO 2016 / 0977077, in constructing the inventive piezoelectric adhesive tape laminate poling is not conducted on the type of combination and annealing is not conducted either.

[0133] The curable adhesive laminate tape may comprise: a first release liner; a first adhesive composition; a piezoelectric polymer film or piezoelectric polymer composite film; a second adhesive composition; and a second release liner, wherein at least one of the first adhesive composition or the second adhesive composition comprises an epoxy composition in the form of an epoxy matrix, wherein the epoxy matrix comprises an epoxy resin, such as a polymer with (chloromethyl)oxirane and 4,4'-(1 -methylethylidene)bis[phenol], which may be sold under the trade name EPON SU-8 and ethylene-vinyl acetate copolymer (EVM) with 90 wt % vinyl acetate such as that sold under the trade name LEVAPREN 900 as the film former. The first adhesive composition or the second adhesive composition may further comprise an aliphatic diglycidy lether, such as the diglycidyl ether of 1 ,4- butanediol, which may be sold under the trade name EPODIL 750 and / or a photoinitiator containing a mixture of triarylsulfonium hexafluoroantimonate salts in propylene carbonate, which may be sold under the trade name UVI 6976 as the photoinitiator. The first and / or the second release liner may be a PET release liner, preferably a coated PET release liner e.g. siliconised PET release liner. The piezoelectric polymer film or piezoelectric polymer composite film may desirably be constructed from polyvinylidene difluoride (PVDF) .

[0134] The PVDF in the epoxy adhesive composition may be 56% weight percent after solvent evaporation based on weight of the total weight of the composition.2024P00380

[0135] The epoxy adhesive composition layer may have a thickness of 50 pm and the piezoelectric polymer film or piezoelectric polymer composite film layer has a thickness of 30 pm. The epoxy adhesive composition layer may have a thickness of 50 pm and the piezoelectric polymer film or piezoelectric polymer composite film layer has a thickness of 50 pm. The epoxy adhesive composition layer may have a thickness of 50 pm and the piezoelectric polymer film or piezoelectric polymer composite film layer has a thickness of 80 pm. The epoxy adhesive composition layer may have a thickness of 50 pm and the piezoelectric polymer film or piezoelectric polymer composite film layer has a thickness of 110 pm.

[0136] The epoxy adhesive composition layer may have a thickness of 30 pm and the piezoelectric polymer film or piezoelectric polymer composite film layer has a thickness of 80 pm. The epoxy adhesive composition layer may have a thickness of 50 pm and the piezoelectric polymer film or piezoelectric polymer composite film layer has a thickness of 80 pm. The epoxy adhesive composition layer may have a thickness of 100 pm and the piezoelectric polymer film or piezoelectric polymer composite film layer has a thickness of 80 pm.

[0137] Desirably, the epoxy adhesive composition layer comprises a solid epoxy as defined herein.

[0138] The inventive piezoelectric adhesive tape laminate can be used as a sensor, an emitter or as a generator in energy harvester.

[0139] Suitable sensors can be for example pressure sensors and suitable emitters can be for example acoustic transducers.

[0140] A device, such as an emitter, a sensor or a generator for an energy harvester can be provided, wherein the device comprises a piezoelectric adhesive composition according to the present invention between two conductive elements.

[0141] The device can be manufactured without separately adhering or attaching a piezoelectric component to a surface of conductive elements with an additional or separate adhesive.2024P00380

[0142] Other uses of such piezoelectric adhesive laminate tapes include sensor materials for structural health monitoring of adhesively bonded structures, coatings for such structures and / or sealants used in such structures.. For instance, with reference to an English language machine translation of Chinese Patent Document No. CN 105765750B, a sandwich layer may be disposed between two piezoelectric layers, where each piezoelectric layer includes a polarized piezoelectric polymer. In the case of a touch sensor, according to the CN ‘750B document, a separately addressable electrode is arranged above a first piezoelectric layer or a second piezoelectric layer. A circuit is coupled to the first electrode and the second electrode, so that detection of a response to the touch surface being activated, telecommunications between the one electrode relative to second electrode may occur. The electrodes themselves can be directly deposited on the piezoelectric layer(s) and the deposition may occur in a random or non-random pattern. In some instances, the electrodes can be transparent.

[0143] Other uses of such piezoelectric adhesive laminate tapes include use in a monitoring system, such as for fluid flow pathways, for example for monitoring pipes.

[0144] With reference to commercial applications, effective maintenance of pipelines is essential in order to transport / distribute in many cases long distances fluids of many kinds. For instance, fuel is transported / distributed from production or storage facilities to consumers throughout the United States, through a vast network of existing fuel transmission and distribution pipelines which exists to ensure the ready availability of affordable fuel. But, with well over 1 million miles of pipeline, constant monitoring is not economically feasible or routinely performed.

[0145] Currently, pipeline inspection may use in-line-inspection tools, such as “pigs” (pipeline inspection gauges), which are inserted into a pipeline or pipeline segment, and then either self-propelled or pushed along the interior of the pipe via applied pressure. “Smart-pigs” may also collect data on the interior pipeline surface based on, for example, magnetic flux leakage, ultrasound testing, or visual inspection.2024P00380While established and accepted methods for structural health monitoring for pipelines, pigging is only performed infrequently. For instance, certain older pipelines may suffer from limited access or low / no-flow conditions, making inspection via pigging a potentially risky operation. And use of such smart-pigs also involves periodic shutdown, or restriction of flow of the fluid in the pipes to permit introduction of the pig for inspection. Of course, once introduced the pig should then be removed.

[0146] If a fault is detected this will also then have to be monitored over time, which then also requires pipe fluid flow stoppages. In other words many of the current inspection methods do not allow continuous, online and remote monitoring. Such continuous, online and remote inspection is desirable as it allows the detection and location of a fault at the moment that it is formed. Such a fault can then be continuously monitored without interrupting fluid flow, allowing operators to plan repair of a particular section when the fault reaches a critical stage where it poses a danger to the integrity / structural safety of the greater pipeline.

[0147] Therefore, many testing methods and systems at a minimum do not have the ability to remotely and continuously monitor the interior conditions of pipes and pipelines.

[0148] In addition, even where leaks are identified they are likely to be much smaller as they have been identified earlier. Such smaller leaks oftentimes go undetected and unrepaired for extended periods of time, during which loss of fluid has occurred, potential ground pollution has occurred and the small leaks have the chance to become larger leaks, exacerbating fluid loss and ground pollution.

[0149] Accordingly, there exists a need for a new way in which to monitor remotely, continuously if desired and non-invasively pipeline integrity. Meeting that need would allow for optimization of pipeline use and scheduled maintenance, such as by enabling accurate location detection of faults as they form and without the need for human intervention or manual handling. This correlates to less pipeline downtime and less unnecessary cleaning and replacement of pipelines. A significant public benefit would be realized, as fewer major pipeline leaks and blowouts would occur.2024P00380And a much smaller expense would be involved instead of a full replacement of a pipeline or installation of fiber optic monitoring or sensing systems. As such, fast and widespread adoption may be realized, even by public entities, such as utilities, whose budgets are constrained by law or by appropriations.

[0150] The inventive laminate may be applied to one or more surface(s) of a pipe or pipeline, a flange, a pump, an elbow, a hopper or a chute (collectively, “fluid flow pathways”), for instance, to permit for remote detection, monitoring and / or reporting of a condition on the applied surface and how that condition may be impacting performance of the flow of fluid and / or the surrounding environment of the fluid flow pathway(s).

[0151] The system thus created for detection, monitoring and / or reporting of the condition and the performance of the fluid flow pathway(s) involves the placement of the inventive laminate tape about a surface of a portion of the fluid flow pathway(s). The inventive laminate tape may be applied as a wrap or a patch on the selected surface. Oftentimes but not necessarily the placement is on a portion of the fluid flow pathway(s) - e.g., a valve, joint, bend or junction -- that may be more susceptible to stress or stress related defects. Within the inventive laminate is a piezoelectric layer that is capable of generating an electrical signal and when a flaw occurs within the fluid flow pathway(s), a different electrical signal is generated.

[0152] The signals generated may be harvested by circuitry disposed in proximity to the fluid flow pathway(s) on which the inventive laminate tape is disposed. The harvested signals may then be transmitted as data which is then stored for evaluation purposes. The differentiation in the electrical signals provides information on the extent and even the nature of the fault, and whether a repair or replacement is needed then or in the future. See e.g. FIG 11 .

[0153] Accordingly, in another aspect, provided herein is a method for monitoring assets, such as in a fluid flow pathway(s), the method comprising: applying the inventive curable adhesive laminate tape of the invention to a surface of a portion of an asset such as a fluid flow pathway for example a pipe;2024P00380 providing monitoring equipment, such as a remote device, to receive signals generated by the piezoelectric layer of the laminate tape, and receiving generated signals for monitoring and reporting conditions in the fluid flow pathway(s). The laminate tape may be in the form of a wrap or a patch and comprises: a first release liner; a first adhesive composition (which may comprise an epoxy matrix); a piezoelectric polymer film or piezoelectric polymer composite film having: a film thickness of from about 1 pm to about 500 pm, a piezoelectric coefficient d33 value of from about 5 to about 40 picocoulombs / Newton (pC / N), from about 10 to about 35 pC / N, or from about 20 to about 30 pC / N, each when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001), a modulus of from about 2,000 to about 2,700 Pascals (Pa), and a dielectric constant of from about 8 to about 50; a second adhesive composition (which may comprise an epoxy matrix); and a second release liner.

[0154] Prior to application of the inventive curable adhesive laminate tape, the first and / or second release liner must be removed. The inventive curable adhesive laminate tape of the invention may be applied to one or more surface(s) of a portion of an asset. Accordingly, the first and / or second release liner may be removed and the second and / or first release liner may remain on the inventive curable adhesive laminate tape where it is not adhered to the surface of a portion of an asset.

[0155] In another aspect, provided herein is a system for monitoring assets such as in a fluid flow pathway(s) for example in pipes. The system comprises the application of the inventive curable adhesive laminate tape, which comprises: a first release liner; a first adhesive composition (which may comprise an epoxy matrix);2024P00380 a piezoelectric polymer film or piezoelectric polymer composite film having: a film thickness of from about 1 pm to about 500 pm, a piezoelectric coefficient CI33 value of from about 5 to about 40 picocoulombs / Newton (pC / N), from about 10 to about 35 pC / N, or from about 20 to about 30 pC / N, each when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001), a modulus of from about 2,000 to about 2,700 Pascals (Pa), and a dielectric constant of from about 8 to about 50; a second adhesive composition (which may comprise an epoxy matrix); and a second release liner, to a surface of a portion of an asset such as a fluid flow pathway for example a pipe.

[0156] Prior to application of the inventive curable adhesive laminate tape, the first and / or second release liner must be removed. The system may include monitoring equipment, such as a remote device, to receive signals generated by the piezoelectric layer of the laminate tape. The monitoring equipment will typically receive generated signals and utilise those for monitoring and reporting conditions in the asset such as a fluid pathway for example a pipe.

[0157] Conditions to be reported may include anomaly detection such as cracks or leaks, pressure and temperature abnormalities and failed adhesion bonds. Suitable monitoring equipment, e.g. signal harvesting circuitry, for use with the inventive piezoelectric adhesive laminate tape is depicted in FIG. 11. Three main stages of monitoring are described, including the signal generation, processing (involving data acquisition and processing) and data analysis.

[0158] The invention will be more fully described by the following examples which are presented solely for illustrative purposes.2024P00380EXAMPLES

[0159] The initial examples shown below involve the creation of [2,2] composites and [0,3] composites to show the respective piezoelectric capabilities together with the adhesive capabilities.Epoxy

[0160] The constituents and relative amounts in a weight percent basis of the epoxy matrix for the adhesive layers is noted below in Table 1 .Table 1Component: _ Weight Percent:EPON SU-8 28.6LEVAPREN 900 13.3Ethyl Acetate 38.1EPODIL 750 19.0Initiator (UVI 6976) 1.0

[0161] To ethyl acetate in a HDPE wide-neck bottle was added LEVAPREN 900 with mixing on a roller mixer at 60 rpm until fully dissolved. EPON SU-8, EPODIL 750 and initiator were then added with mixing on a roller mixer at 60 rpm until a homogenous mixture was obtained.

[0162] The epoxy matrix formed as above was used to make an epoxy [2,2] composite. This epoxy [2,2] composite within the scope of the present invention was formed using a 50 pm section of PVDF from PolyK Technologies under the trade designation PVDF-P0050 of 30 x 300 x 0.05 mm width, length and thickness. That PVDF section was placed on a layer of siliconised PET release liner. The PVDF topped release liner was placed on the stage of an Elcometer 4340 Automatic Film Applicator, onto which was bar-coated the epoxy matrix at the desired thickness, which could be 30 pm, 50 pm or 100 pm. The epoxy-coated PVDF laid upon the release liner was then heated at a temperature of 50°C for a period of time of 5 minutes and then removed from the Elcometer stage.2024P00380

[0163] A second siliconised PET release liner was placed on top of the exposed epoxy layer to form an assembly. The assembly was then turned upsidedown and the first siliconised PET release liner was removed to expose the uncoated surface of the PVDF layer. This upside down assembly was again placed on the stage of an Elcometer 4340 Automatic Film Applicator, onto which was bar-coated the epoxy matrix at the desired thickness, which again could be 30 pm, 50 pm or 100 pm. The epoxy-coated PVDF assembly laid upon the release liner was then heated at a temperature of 50°C for a period of time of 5 minutes and then removed from the Elcometer stage. A second release liner was then laid upon the exposed adhesive layer to provide the laminate tape assembly as shown in FIG. 1 .

[0164] Lapshear test specimens were prepared as follows in accordance with ASTM D1002-10(2019), using the laminate tape assembly as described above and shown in FIG. 1 :

[0165] The first siliconised PET release liner was removed to expose the first epoxy adhesive layer from the epoxy adhesive laminate tape. A mild steel substrate was placed face down onto a surface. A section of epoxy adhesive laminate tape was cut in dimensions of at least about 25.4 mm x 12.7 mm and disposed on the mild steel lapshear in a manner to ensure bondline coverage of 322.6 mm2.

[0166] The second siliconised PET release liner was then removed exposing the second adhesive layer, which was then exposed to UV radiation at an intensity of about 60 mW / cm2for a period of time of about 3 seconds using a UVALOC UV Cure Chamber set at 500 W. Another mild steel lapshear was then brought into contact with the second adhesive layer to give a 322.6 mm2bonded area. The mated lapshear assembly was clamped in place for a period of time of about 24 hours.

[0167] The piezoelectric coefficient ‘d33 was measured through the metal lapshear bondline using a PIEZOTEST d33 PiezoMeter System employing the Berlincourt Method. See M. Stewart, M.G. Cain, Direct Piezoelectric Measurement: The Berlincourt Method BT - Characterisation of Ferroelectric Bulk Materials and Thin2024P00380Films, Springer, Netherlands, Dordrecht, pp. 37-64 (2014), 10.1007 / 978-1-4020- 9311-1 3.

[0168] Shear Strength of the lapshear assembly (i.e., bondline) was measured on a Zwick (Z010) Tensile Testing machine at a pull speed of 2 mm / min on a 10kN loadcell.

[0169] The epoxy matrix formed as above was used to make an epoxy [0,3] composite.

[0170] The PVDF in epoxy [2,2] composite was determined to be 56 weight percent after solvent evaporation. In order to directly compare the epoxy [2,2] composite with the epoxy [0,3] composite, the weight percent of PVDF was calculated from the epoxy [2,2] composite and applied to the epoxy [0,3] composite.

[0171] Thus, a comparative epoxy formulation for the adhesive layers was prepared from the constituents and relative amounts noted below in Table 2.Table 2Component:Percent:EPON SU-8 15.99LEVAPREN 900 7.44Ethyl Acetate 21.3EPODIL 750 10.62Initiator (UVI 6976) 0.56PVDF Powder* 44.09Available from abcr GmbH, product code AB211736

[0172] The comparative epoxy formulation made from the constituents in Table 2 was prepared by mixing the constituents in a speed mixer at 3500 rpm for a period of time of 5 minutes.

[0173] A layer of siliconised PET release liner was placed on the stage of an Elcometer 4340 Automatic Film Applicator, and this epoxy formulation was then bar- coated onto the release liner at the desired thickness, namely 30 pm, 50 pm or 100 pm.2024P00380

[0174] The epoxy formulation-coated release liner was then heated at a temperature of 50°C for a period of time of 5 minutes and then removed from the Elcometer stage.

[0175] Lapshear specimens were prepared with this epoxy formulation as previously outlined above.

[0176] The remaining film was cut into small sections that could be exposed to UV radiation at an intensity of about 60 mW / cm2for a period of time of about 3 seconds using a UVALOC UV Cure Chamber set at 500 W. These sections of the film were used for contact poling by disposing them between conductive electrode surfaces.

[0177] The piezoelectric coefficient 'dss' was measured using a PIEZOTEST d33PiezoMeter System employing the Berlincourt Method.

[0178] The physical properties measured and observed for the epoxy [2,2] composite and the epoxy [0,3] composite have been captured in Table 3 below.Table 3a56 wt.% PVDFb24 hour cure, after exposure to UV radiation, on Mild SteelcPoling Conditions: Corona Poling was carried out using a Milman Corona Poling Unit with Pin Voltage= 40 kV, Grid Voltage = 20 kV, Pin Height = 60 mm, Grid Height = 30 mm, Time = 5 minutes* Electric Shortage occurred through sample2024P00380

[0179] The physical properties measured and observed for the inventive epoxy [2,2] composite and the comparative epoxy [0,3] composite captured in Table 3 demonstrate comparable bond strength for the epoxy [2,2] composite compared to the epoxy [0,3] composite on mild steel lapshear specimen while the epoxy [2,2] composite demonstrated a d33 value whereas the epoxy [0,3] composite showed none.

[0180] The comparative epoxy formulation contains randomly dispersed PVDF particles. As a consequence of the random dispersion, no alignment of dipoles exists until disposed between metal electrodes for the purpose of contact poling.Piezoelectric Film Thickness in [2,2] Composites

[0181] The next series of examples involve the creation of [2,2] composites to show the respective piezoelectric capabilities depending on the thickness of the PVDF layer in the adhesive tape laminate.

[0182] The composites were made from epoxy adhesive layers at a thickness of 50 pm and a PVDF layer of 30 pm, 50 pm, 80 pm and 110 pm. Mild steel lapshear substrates were used with the epoxy adhesive layers.

[0183] Tables 4 shows the epoxy adhesive layers with a PVDF layer of 30 pm and the bond strengths and piezoelectric effect achieved over time. FIG. 2 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, each for the listed room temperature aging periods.Table 42024P00380

[0184] At a thickness of 30 pm for the piezoelectric layer, adhesive bond strength seems to improve somewhat over time in these assemblies, while the piezoelectric effect seems to at least remain somewhat constant over time (though each within experimental error according to the standard deviations).

[0185] Table 5 shows the epoxy adhesive layers with a PVDF layer of 50 pm and the bond strengths and piezoelectric effect achieved over time. FIG. 3 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, at each for the listed room temperature aging time periods.Table 5

[0186] At a thickness of 50 pm for the piezoelectric layer, adhesive bond strength and piezoelectric effect seems to at least remain somewhat maintained (though each within experimental error according to the standard deviations).

[0187] Table 6 shows the epoxy adhesive layers with a PVDF layer of 80 pm and the bond strengths and piezoelectric effect achieved over time. FIG. 4 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, at each for the listed room temperature aging time periods.2024P00380Table 6

[0188] At a thickness of 80 m for the piezoelectric layer, adhesive bond strength and piezoelectric effect seems to at least remain somewhat maintained (though each within experimental error according to the standard deviations).

[0189] Table 7 shows the epoxy adhesive layers with a PVDF layer of 110 pm and the bond strengths and piezoelectric effect achieved over time. FIG. 5 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, at each for the listed room temperature aging time periods.Table 7

[0190] At a thickness of 110 pm for the piezoelectric layer, adhesive bond strength and piezoelectric effect seems to at least remain somewhat maintained (though each within experimental error according to the standard deviations).2024P00380

[0191] In general, from the data collected in Tables 4-7 it appears that as the thickness of the layer of the PVDF film increases within an epoxy adhesive layer at a constant thickness, the value of the corresponding d33 is retained within experimental error over the time periods evaluated for the room temperature aging evaluations. The d33 results here thus demonstrate excellent piezoelectric properties are achieved.Adhesive Film Thickness in [2,21 Composites

[0192] The next series of examples involve the creation of [2,2] composites to show the respective piezoelectric capabilities depending on the thickness of the adhesive layers in the adhesive tape laminate and its impact on piezoelectric effect.

[0193] The composites were made from epoxy adhesive layers, each at a thickness of 30 pm, 50 pm and 100 pm, and a PVDF layer of 80 pm sandwiched in between.

[0194] Table 8 shows the epoxy adhesive layers at a thickness of 30 pm with a PVDF layer of 80 pm and the bond strengths and piezoelectric effect achieved over time. FIG. 6 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, at each of the listed room temperature aging periods.Table 82024P00380

[0195] At a thickness of 80 pm for the piezoelectric layer and an adhesive layer thickness of 30 pm, adhesive bond strength and piezoelectric effect seems to at least remain somewhat maintained (though each within experimental error according to the standard deviations).

[0196] Table 9 shows the various adhesive layers at a thickness of 50 pm with a PVDF layer of 80 pm and the bond strengths and piezoelectric effect achieved over time. FIG. 7 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, at each of the listed room temperature aging periods.Table 9

[0197] At a thickness of 80 pm for the piezoelectric layer and an adhesive layer thickness of 50 pm, adhesive bond strength and piezoelectric effect seems to at least remain somewhat maintained (though each within experimental error according to the standard deviations).

[0198] Table 10 shows the various adhesive layers at a thickness of 100 pm with a PVDF layer of 80 pm and the bond strengths and piezoelectric effect achieved over time. FIG. 8 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, at each of the listed room temperature aging periods.2024P00380Table 10

[0199] At a thickness of 80 m for the piezoelectric layer and an adhesive layer thickness of 100 pm, adhesive bond strength and piezoelectric effect seems to at least remain somewhat maintained (though each within experimental error according to the standard deviations).

[0200] Table 11 shows the epoxy adhesive layers at a thickness of 100 pm with a PVDF layer of 80 pm and the bond strengths and piezoelectric effect achieved initially at room temperature for 24 hours and then over time when exposed to a temperature of 40°C and a relative humidity of 98%. FIG. 9 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, at each of the listed time periods under the noted accelerated aging conditions.Table 112024P00380

[0201] Under these accelerated aging conditions, adhesive bond strength seems to have decreased over time while the piezoelectric effect seems to at least remain somewhat maintained (though each within experimental error according to the standard deviations).

[0202] Table 12 shows the various adhesive layers at a thickness of 30 pm with a PVDF layer of 80 pm and the bond strengths and piezoelectric effect achieved initially at room temperature for 24 hours and then over time when exposed to a temperature of 80°C. FIG. 10 depicts this data visually, where the bar charts show adhesive strength and the curve shows piezoelectric effect, each of the listed time periods under the noted accelerated aging conditions.Table 12

[0203] Under these accelerated aging conditions, adhesive bond strength seems to improve over time in these assemblies, while the piezoelectric effect seems to at least remain somewhat constant.

Claims

2024P00380What is Claimed is:1 . A curable adhesive laminate tape comprising: a first release liner; a first adhesive composition; a piezoelectric polymer film or piezoelectric polymer composite film having: a film thickness of from about 1 pm to about 500 pm, a piezoelectric coefficient d33 value of from about 5 to about 40 picocoulombs / Newton (pC / N), from about 10 to about 35 pC / N, or from about 20 to about 30 pC / N, each when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001), a modulus of from about 2,000 to about 2,700 Pascals (Pa), and a dielectric constant of from about 8 to about 50; a second adhesive composition; and a second release liner, wherein at least one of the first adhesive composition or the second adhesive composition comprises an epoxy composition, and when cured the adhesive laminate tape demonstrates one or more of the following physical properties:• lap shear strength on mild steel of from about 3.0 to about 9.0 (N / mm2), when measured according to ASTM D1002,• after exposure to room temperature aging conditions for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 3.0 to about 9.0 (N / mm2), when measured according to ASTM D1002,• after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks, lap shear strength on mild steel of from about 6.0 to about 9.0 (N / mm2), when measured according to ASTM D1002,• after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks, lap shear strength on mild steel2024P00380 of from about 3.0 to about 6.5 (N / mm2), when measured according to ASTM D1002,• up to 129 percent adhesion retention on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks;• up to 59 percent d33 coefficient retention on mild steel after exposure to accelerated aging conditions of 80°C for a period of time of up to 6 weeks;• up to 61 percent adhesion retention on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks;• up to 103 percent d33 coefficient retention on mild steel after exposure to accelerated aging conditions of 40°C and 98% relative humidity for a period of time of up to 6 weeks;• when disposed and cured between mild steel substrates a d33 coefficient across the mild steel substrates of from about 1 .5 to about 8 for epoxy-based adhesive layers, after exposure to room temperature aging conditions for a period of time of 2 weeks, when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001).

2. The curable adhesive laminate tape according to claim 1 , wherein the epoxy composition is in the form of an epoxy matrix and comprises a film former.

3. The curable adhesive laminate tape according to claim 1 , wherein the piezoelectric polymer film or piezoelectric polymer composite film has a film thickness of from about 1 pm to about 500 pm.

4. The curable adhesive laminate tape according to claim 1 , wherein the piezoelectric polymer film or piezoelectric polymer composite film has a film thickness of from about 10 pm to about 150 pm.

5. The curable adhesive laminate tape according to claim 1 , wherein the piezoelectric polymer film or piezoelectric polymer composite film has a film thickness of from about 20 pm to about 110 pm.2024P003806. The curable adhesive laminate tape according to claim 1 , wherein the piezoelectric polymer film or piezoelectric polymer composite film has a film thickness of from about 25 pm to about 75 pm.

7. The curable adhesive laminate tape according to claim 1 , wherein the piezoelectric polymer film or piezoelectric polymer composite film has a piezoelectric coefficient d33 value of from about 10 to about 35 pC / N, when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001).

8. The curable adhesive laminate tape according to claim 1 , wherein the piezoelectric polymer film or piezoelectric polymer composite film has a piezoelectric coefficient d33 value of from about 20 to about 30 pC / N, when measured according to National Physical Laboratory Measurement Good Practice Guide No. 44: Measuring Piezoelectric d33 Coefficients Using Direct Method (2001).

9. The curable adhesive laminate tape according to claim 1 , wherein the piezoelectric polymer film or piezoelectric polymer composite film is constructed from a member selected from the group consisting of polyvinylidene difluoride (PVDF), polyvinylidene difluoride trifluoroethylene (P(VDF-TrFE)), polyvinylidene difluoride hexafluoropropylene (P(VDF-HFP)), polyvinylidene difluoride chlorofluoroethylene (P(VDF-CFE)), polyvinylidene fluoride-co-trifluoroethylene-co-hexafluoropropylene (PVDF-TrFE-HFP), and polyvinylidene fluoride-co-trifluoroethylene-co- chlorofluoroethylene (PVDF-TrFE-CFE).

10. The curable adhesive laminate tape according to claim 1 , wherein the first adhesive composition comprises an epoxy composition and the second adhesive composition comprises a cyanoacrylate or a (meth)acrylate composition.11 . The curable adhesive laminate tape according to claim 1 , wherein each of the first adhesive composition and the second adhesive composition comprises an epoxy composition.2024P0038012. Use of the curable adhesive laminate tape according to any preceding claim in a monitoring system, such as for fluid flow pathways, for example for monitoring pipes.

13. Use of the curable adhesive laminate tape according to claim 1 as a sensor to monitor structural health of adhesively bonded structures.

14. A device comprising the curable adhesive laminate tape according to any of claims 1 to 11 disposed between two conductive elements.

15. A method for monitoring assets, such as in a fluid flow pathway(s), the method comprising: applying the laminate tape of any of claims 1 to 11 to a surface of a portion of an asset such as a fluid flow pathway for example a pipe; providing monitoring equipment, such as a remote device, to receive signals generated by the piezoelectric layer of the laminate tape, and receiving generated signals for monitoring and reporting conditions in the fluid flow pathway (s).

16. The method of Claim 15, wherein the laminate tape is in the form of a wrap or a patch.

17. A system for monitoring assets, such as in a fluid flow pathway(s), the system comprising: the laminate tape of any of claims 1 to 11 bonded to a surface of a portion of an asset such as a fluid flow pathway for example a pipe; monitoring equipment, such as a remote device, to receive signals generated by the piezoelectric layer of the laminate tape.

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