Induction heating of cured adhesives

Abstract

Disclosed herein is an adhesive additive for magnetically curing an adhesive. The adhesive additive includes magnetic nanoparticles comprising (i) a metal, wherein the metal comprises iron, manganese, cobalt, nickel, and / or zinc, or (ii) a metal oxide, wherein the metal oxide contains a metal comprising iron, manganese, cobalt, nickel, and / or zinc; a coating on the magnetic nanoparticles, wherein the coating comprises (a) a surfactant or an inorganic material, and (b) a monomer or a polymer miscible with an adhesive base material into which the adhesive additive can be incorporated; wherein the magnetic nanoparticles generate thermal energy in response to an alternating electromagnetic field applied thereto to cause the adhesive base material to form crosslinks. Also disclosed herein is a magnetically curable adhesive. The adhesive includes the adhesive additive and the adhesive base material. Further disclosed herein is a method of forming the adhesive additive.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Singapore Patent Application No. 10202008040V, filed on August 21, 2020, the contents of which are incorporated herein by reference in their entirety for all purposes. Technical Field

[0003] This disclosure relates to adhesive additives for use in magnetocurable adhesives. This disclosure also relates to magnetocurable adhesives and methods for forming adhesive additives. Background Technology

[0004] For a variety of applications, chemically cured adhesives (CCAs) may be superior to mechanical fasteners because they are lightweight and the stress distribution during bonding does not damage the surface or material. The global instant adhesive market is estimated to be over $3 billion, with two-component thermosetting structural adhesives likely to dominate. Structural adhesives may require mixing epoxy / hardener resins or thermally activated one-pot epoxy / hardener mixtures (thermosetting), which can lead to energy loss and stress / strain mismatch due to uneven temperature cycling of the material and resin. To overcome these obstacles, alternative methods have emerged, such as fast-curing epoxy resins, photocuring, electron beam curing, and the emerging electrocuring.

[0005] Fast-curing thermosetting adhesives are often one-pot adhesives that cure rapidly within minutes. However, the benefits of this rapid-curing property are limited for insulating or heat-sensitive materials such as wood, ceramics, or plastics.

[0006] Photopolymerization provides non-contact activation, but often relies on ultraviolet (UV)-transmitting materials and free radical initiators, which can lead to heat-sensitive manufacturing problems.

[0007] Electron beam curing may rely on incident high-speed electrons that initiate free radicals within a polymer initiator. The high energy of the electron beam / irradiation provides uniform curing, but requires significant investment in capital and infrastructure. All components must be irradiated with electrons, thus necessitating shielded rooms and highly trained technicians.

[0008] Surface-curing adhesives are often composed of methyl cyanoacrylate / ethyl cyanoacrylate, also known as "super glue." They may have unique properties that allow them to form strong surface bonds or no bond at all. The inability to bond to rough / acidic surfaces (metals), difficulty in handling, brittle material properties, and low-temperature durability (curing adhesives must be kept below 70°C) limit surface curing for manual home repairs.

[0009] Previously, few studies have developed adhesive curing mediated by alternating electromagnetic fields (AMF) (“magnetocuring”), which may involve in-situ activation of thermosetting adhesives. Magnetocuring provides a non-contact method for bonding nonmetallic materials. Examples of such studies include magnetocuring based on FeCo epoxy composites, induction curing of thiol-acrylate and thiol-olefin composites using cobalt and nickel particles, and polymerization of cyanate esters via induction heating using Fe3O4 as an internal heat source. Induction curing using nickel nanoparticles to bond composites and polymerization using iron oxide nanochains have also been investigated. However, these formulations often have inherent drawbacks that limit industrial practice, such as, but not limited to, (i) the lack of surface functionalization of the magnetopolymer additives, resulting in poor colloidal stability, which can impair storage stability due to the formation of large aggregates; (ii) the formation of nanoparticle aggregates, resulting in undesirable heterogeneous resins, which in turn leads to the formation of hot spots and localized resin / epoxy pyrolysis; (iii) the pairing of high heating power (3-32kW) with inefficient metal Co (2μm) and Ni (3μm) particles or Fe3O4 particles; and (iv) the use of high-frequency (above 2MHz) and wide particle size distribution (70nm-22μm) Ni particles is impractical for commercial applications.

[0010] In another example, previous research employed metal / uncoated magnetic nanoparticles, which led to nanoparticle aggregation and the formation of hot spots within the binder. To overcome these issues, the colloidal stability of the magnetic nanoparticles was investigated by coating them with silica; however, silica-coated particles do not allow for inclusion in various resins. Application-specific coatings require different approaches for each application. Furthermore, most methods involve harsh reaction conditions (high frequency and high magnetic field), thus requiring specially designed systems, resulting in high capital and facility costs that limit their commercial viability. For example, high frequencies cannot penetrate thick workpieces, while low frequencies are preferred.

[0011] If the colloidal stability of magnetic nanoparticles can be properly maintained to prevent hot spots caused by aggregation, then bonding and curing via induction heating often has industrial applications.

[0012] Therefore, a solution is needed to overcome one or more of the aforementioned limitations. This solution should at least provide an improved and environmentally friendly adhesive composite material. Summary of the Invention

[0013] In a first aspect, this document provides an adhesive additive for magnetocurable adhesives, the adhesive additive comprising:

[0014] Magnetic nanoparticles, wherein the magnetic nanoparticles comprise:

[0015] (i) a metal, said metal including iron, manganese, cobalt, nickel and / or zinc, or

[0016] (ii) a metal oxide containing a metal, the metal including iron, manganese, cobalt, nickel and / or zinc;

[0017] A coating layer on the magnetic nanoparticles, the coating layer comprising:

[0018] (a) Surfactants or inorganic materials, and

[0019] (b) A monomer or polymer miscible with the adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate.

[0020] The magnetic nanoparticles generate heat in response to an alternating electromagnetic field applied thereto, causing the adhesive substrate to crosslink.

[0021] On the other hand, this article provides a magnetocurable adhesive, the adhesive comprising:

[0022] The adhesive additives described in the various embodiments of the first aspect, and

[0023] Adhesive substrate.

[0024] On the other hand, this document provides a method for forming the adhesive additives described in various embodiments of the first aspect, the method comprising:

[0025] Magnetic nanoparticles are provided, the magnetic nanoparticles comprising:

[0026] (i) a metal, said metal including iron, manganese, cobalt, nickel and / or zinc, or

[0027] (ii) a metal oxide containing a metal, the metal including iron, manganese, cobalt, nickel and / or zinc;

[0028] Mix the aqueous solution containing the magnetic nanoparticles with a surfactant; and

[0029] An organic solution comprising magnetic nanoparticles coated with the surfactant is mixed with (i) a monomer or (ii) a polymer miscible with an adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate.

[0030] On the other hand, this document provides a method for forming the adhesive additives described in various embodiments of the first aspect, the method comprising:

[0031] Magnetic nanoparticles are provided, the magnetic nanoparticles comprising:

[0032] (i) a metal, said metal including iron, manganese, cobalt, nickel and / or zinc, or

[0033] (ii) a metal oxide containing a metal, the metal including iron, manganese, cobalt, nickel and / or zinc;

[0034] One or more surfactants are formed on the magnetic nanoparticles;

[0035] An inorganic precursor is formed on one or more surfactants;

[0036] The magnetic nanoparticles are calcined together with the inorganic precursor to remove one or more surfactants and form an inorganic material coated on the magnetic nanoparticles.

[0037] An organic mixture comprising magnetic nanoparticles coated with the inorganic material is mixed with (i) a monomer or (ii) a polymer miscible with an adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate.

[0038] Brief description of the attached figures

[0039] The accompanying drawings are not necessarily drawn to scale, but rather focus on illustrating the principles of this disclosure. Various embodiments of this disclosure will now be described with reference to the following drawings.

[0040] Figure 1A It shows the result from Mn 0.4 Zn 0.6 Fe2O4 to Mn 0.7 Zn 0.3 X-ray powder diffraction (XRD) pattern of spinel phase of Fe2O4.

[0041] Figure 1B It shows Figure 1A The crystal size of Curie nanoparticles (CNPs) was estimated using the Scherrer equation.

[0042] Figure 1C It shows Figure 1A The actual composition of CNPs for Mn / Zn 50 / 50 and 70 / 30 was measured by inductively coupled plasma mass spectrometry (ICP-MS) with a standard deviation (SD) of <1%.

[0043] Figure 1D Showing the target Figure 1A The CNP hysteresis loop was measured at room temperature (approximately 27°C) using a Physical Property Measurement System (PPMS).

[0044] Figure 1E It shows Figure 1A The graph shows the normalized magnetization of the CNP as a function of temperature in a magnetic field of 140 Oe, ranging from room temperature (e.g., about 27 °C) to 400 °C.

[0045] Figure 1F Mn is shown 0.7 Zn 0.3 The curves showing the magnetization of Fe2O4 CNP under applied magnetic fields of 50, 80, 100 and 140 Oe as a function of temperature.

[0046] Figure 2A Mn is shown 0.8 Zn 0.2 Fe2O4 and Mn 0.9 Zn 0.1 X-ray powder diffraction (XRD) pattern of spinel phase of Fe2O4.

[0047] Figure 2B Showing the target Figure 2A The CNP hysteresis loop was measured using PPMS at room temperature (approximately 27°C).

[0048] Figure 2C It shows Figure 1A The graph shows the normalized magnetization of the CNP under a magnetic field of 100 Oe as a function of temperature, ranging from room temperature (e.g., about 27 °C) to 500 °C.

[0049] Figure 3A Mn is shown 0.5 Zn 0.5 Fe2O4, Mn 0.6 Zn 0.4 Fe2O4 and Mn 0.7 Zn 0.3 Fourier transform infrared (FTIR) spectra of the ferrite phase of Fe2O4.

[0050] Figure 3B The FTIR spectra of OA (oleic acid), BADGE (bisphenol A diglycidyl ether), and OA+BADGE are shown.

[0051] Figure 3C The FTIR spectra of OA- and BADGE-modified CNPs are shown. “*” indicates the presence of OA and BADGE.

[0052] Figure 3D A graph showing the percentage weight of the coating layer as analyzed by the change in weight with temperature, based on measurements using thermogravimetric analysis (TGA).

[0053] Figure 3E The thermal degradation modes of OA, BADGE, and OA+BADGE are shown.

[0054] Figure 3FDynamic light scattering (DLS) plots are shown, depicting the change in particle size stability of functionalized CNPs in ethanol over time.

[0055] Figure 4A A graph showing the percentage weight of the coating layer as analyzed by weight changes with temperature based on measurements using a TGA is presented.

[0056] Figure 4B Mn is shown 0.8 Zn 0.2 Fe2O4 and Mn 0.9 Zn 0.1 FTIR spectrum of Fe2O4 ferrite phase.

[0057] Figure 4C The FTIR spectra of OA- and BADGE-modified CNPs are shown. “*” indicates the presence of OA and BADGE.

[0058] Figure 4D Mn coated with oleic acid (OA) and polycaprolactone (PCL) is shown. 0.7 Zn 0.3 Figure showing the weight percentage of the coating layer on Fe2O4 particles.

[0059] Figure 4E Exposed Mn 0.7 Zn 0.3 FTIR spectra of Fe2O4, OA and PCL.

[0060] Figure 4F PCL and Mn modified with OA- and PCL- are shown. 0.7 Zn 0.3 FTIR spectrum of Fe2O4.

[0061] Figure 5 Dynamic light scattering (DLS) plots are shown to compare the changes in colloidal stability of bare CNPs and functionalized CNPs in ethanol over time.

[0062] Figure 6A The following figure shows the Mn measured in the temperature range of 5K to 400K under an applied magnetic field of 140Oe. 0.4 Mn 0.5 Mn 0.6 and Mn 0.7 Magnetization curves of nanoparticles under zero field cooling (ZFC), field cooling (FCC), and field cooling heating (FCW).

[0063] Figure 6B Mn coated with external magnetic fields of 100 Oe, 140 Oe, 250 Oe and 500 Oe are shown in the temperature range of 5 K to 400 K. 0.7The ZFC, FCC and FCW magnetization curves.

[0064] Figure 7A Mn is shown 0.7 Zn 0.3 Transmission electron microscopy (TEM) image of Fe2O4. Scale bar indicates 50 nm.

[0065] Figure 7B Mn is shown 0.7 Zn 0.3 Particle size distribution of Fe2O4.

[0066] Figure 7C Mn is shown 0.7 Zn 0.3 TEM image of Fe2O4 / OA / BADGE. Scale bar indicates 50 nm.

[0067] Figure 7D Mn is shown 0.7 Zn 0.3 Particle size distribution of Fe2O4 / OA / BADGE.

[0068] Figure 8A Functionalized Mn is shown 0.5 Zn 0.5 Fe2O4 / OA / BADGE CNP loaded into bisphenol A diglycidyl ether (BADGE) at 5-30 wt.% under alternating electromagnetic field (AMF) heating at 140 Oe.

[0069] Figure 8B Functionalized Mn is shown 0.6 Zn 0.4 Fe2O4 / OA / BADGE CNP was loaded into bisphenol A diglycidyl ether (BADGE) at 5-30 wt.%, and the AMF heating curves were obtained at 140 Oe.

[0070] Figure 8C Functionalized Mn is shown 0.7 Zn 0.3 Fe2O4 / OA / BADGE CNP was loaded into bisphenol A diglycidyl ether (BADGE) at 5-30 wt.%, and the AMF heating curves were obtained at 140 Oe.

[0071] Figure 8D 15 wt.% functionalized Mn was shown 0.7 Zn 0.3 AMF heating curves of Fe2O4 / OA / BADGE CNP under different field strengths of 50, 80, 100 and 140 Oe.

[0072] Figure 9AFunctionalized Mn loaded into glycerol diglycidyl ether (GDE) at different loading amounts (5-20 wt.%) are shown. 0.8 Zn 0.2 AMF heating curve of Fe2O4 / OA / BADGE CNP at 140 Oe.

[0073] Figure 9B Functionalized Mn loaded into glycerol diglycidyl ether (GDE) at different loading amounts (1-20 wt.%) are shown. 0.9 Zn 0.1 AMF heating curves of Fe2O4 / OA / BADGE CNP at 140 Oe. For a load of 20 wt.%, the field strength was increased every 300 seconds.

[0074] Figure 10A Mn is shown 0.5 Zn 0.5 Fe2O4 / OA / BADGE(Mn 0.42 Mn 0.6 Zn 0.4 Fe2O4 / OA / BADGE(Mn 0.53 ) and Mn 0.7 Zn 0.3 Curie nanoparticles of Fe2O4 / OA / BADGE (Mn0.63) (m CNP The change in mass as temperature increases per second.

[0075] Figure 10B Mn is shown 0.42 Mn 0.53 and Mn 0.63 Graphs of specific absorptivity (SAR) and maximum AMF heating (Tmax) for different formulations.

[0076] Figure 11A The images show a photograph of a digital model (CAD) of an ABS specimen printed by a 3D printer (top left), an ABS specimen with magnetic adhesive cured under AMF (bottom left), an apparatus for mechanical testing (middle), and the bond / ABS fracture after mechanical testing (right). ABS stands for acrylonitrile butadiene styrene.

[0077] Figure 11B Stress-strain curves of cured ES558 with 20 wt.% CNP and ABS (ES558@ABS) are shown.

[0078] Figure 11C The overlap shear adhesion strength diagrams of magnetocured ES558@ABS with different CNP loadings are shown.

[0079] Figure 11DThe lap shear adhesion strength diagrams of different magnetocurable adhesives with 30 wt.% CNP loads to ABS (Adh.@ABS) are shown.

[0080] Figure 11E The diagram shows the overlap shear adhesion strength of magnetocured ES558 with a 30 wt.% CNP load to different adhesive materials.

[0081] Figure 11F The lap shear adhesion strength diagrams of oven-cured and AMF-cured adhesives to glass (adhesive@glass) are shown. Data are expressed as mean ± standard deviation, n = 3, and significance was determined by one-way ANOVA, p < 0.05.

[0082] Figure 12A The surface temperatures of different adhesive materials during the AMF curing process are shown.

[0083] Figure 12B The temperature of magnetic adhesion curing during the AMF process is shown, measured by fiber optic thermocouples and a FLIR camera. The scale bar in the illustration represents 10 mm.

[0084] Figure 12C TGA-DSC diagrams of clean, oven-cured, and AMF-cured ES558 are shown.

[0085] Figure 12D The attenuated total reflectance (ATR) FTIR spectra of ES558 magnetic adhesive cured with net ES558 and AMF are shown.

[0086] Figure 13A This shows the effect of Mn under a magnetic field strength of 100 Oe. x Zn 1-x The curve of magnetization of Fe2O4 CNP as a function of temperature.

[0087] Figure 13B This shows the effect of Mn under a magnetic field strength of 140 Oe. x Zn 1-x The curve of magnetization of Fe2O4 CNP as a function of temperature.

[0088] Figure 14A The temperature profile of CaproGlu curing during the AMF process, measured by fiber optic thermocouples, is shown.

[0089] Figure 14B It shows a concentration of 10 wt.% Mn 0.7 Zn 0.3 Storage / loss modulus of Fe2O4 / OA / PCL magnetized samples.

[0090] Figure 14CIt shows a concentration of 50 wt.% Mn 0.7 Zn 0.3 Laboratory shear bond strength of magnetopolymerized bone samples of Fe2O4 / OA / PCL.

[0091] Figure 15A It shows 5 wt.% Mn 0.9 Zn 0.1 Fe2O4 / OA / BADGE in glycerol diglycidyl ether (GDE) under AMF heating plots at different magnetic field strengths of 60, 80, 100, 120, and 140 Oe, with zero carbon nanotube (CNT) loading.

[0092] Figure 15B It shows Figure 15A AMF heating plot of CNPs, where the CNT loading is 0.5 wt.%.

[0093] Figure 15C It shows Figure 15A AMF heating plot of CNPs, where the CNT loading is 1 wt.%.

[0094] Figure 15D It shows Figure 15A AMF heating plot of CNPs, where the CNT loading is 2 wt.%.

[0095] Figure 16 It shows 5 wt.% Mn 0.9 Zn 0.1 Fe2O4 / OA / BADGE in glycerol diglycidyl ether (GDE) with 0-4 wt.% carbon nanotube coils (CNCs) incorporated, AMF heating diagram at 140 Oe.

[0096] Figure 17A The effect of an alternating electromagnetic field (140 Oe) on carbon nanotubes (CNTs) and carbon nanotube coils (CNCs) is shown, with 1 wt.% of CNTs and CNCs dispersed in a GDE.

[0097] Figure 17B The effect of an alternating electromagnetic field (140 Oe) on carbon nanotubes (CNTs) and carbon nanotube coils (CNCs) is shown, with 1 wt.% of CNTs and CNCs dispersed in ethanol.

[0098] Figure 18A A photograph shows the surface temperature recorded by a fiber optic thermocouple during 10 minutes of curing with ABS under AMF.

[0099] Figure 18B It shows the use of Figure 18A The device recorded the surface temperature of BADGE loaded with 5-30 wt.% CNP.

[0100] Figure 18C The TGA diagram is shown, demonstrating the thermal stability of the epoxy resin (glyceryl diglycidyl ether, GDE and bisphenol A diglycidyl ether, BADGE) and the epoxy adhesive Permabond ES558.

[0101] Figure 18D The DSC diagram shows the activation temperatures of the epoxy resin (glycerol diglycidyl ether, GDE and bisphenol A diglycidyl ether, BADGE) and the epoxy adhesive Permabond ES558.

[0102] Figure 19 The lap shear adhesion strength of magnetocured ABS with 10–30 wt.% CNP + BADGE cured at 140 Oe AMF is shown. Data are expressed as mean ± standard deviation, n = 3. Significance was determined by one-way ANOVA, p < 0.05. NS indicates no significant difference.

[0103] Figure 20 It shows Figure 11A The ABS sample was cured with the magnetic adhesive disclosed herein under AMF.

[0104] Detailed description

[0105] The following detailed description refers to the accompanying drawings, which illustrate specific details and embodiments that may be implemented in accordance with this disclosure.

[0106] Features described in the context of one embodiment may be adapted accordingly to the same or similar features in other embodiments. Features described in the context of one embodiment may be adapted accordingly to other embodiments, even if not explicitly described in those other embodiments. Furthermore, additions and / or combinations and / or alternatives described for features in the context of one embodiment may be adapted accordingly to the same or similar features in other embodiments.

[0107] This disclosure provides an adhesive additive for magnetocurable adhesives. Details of various embodiments of the adhesive additive are now described below, and the advantages associated with these embodiments are demonstrated in the examples.

[0108] The adhesive additive may include magnetic nanoparticles comprising (i) a metal, including iron, manganese, cobalt, nickel, and / or zinc, or (ii) a metal oxide containing a metal, including iron, manganese, cobalt, nickel, and / or zinc. It is understood that the metal oxide includes oxygen. The adhesive additive may include a coating layer on the magnetic nanoparticles. The coating layer may include (a) a surfactant or inorganic material, and (b) a monomer or polymer miscible with the adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate. The magnetic nanoparticles may generate thermal energy in response to an alternating electromagnetic field applied thereto, causing the adhesive substrate to crosslink.

[0109] In various embodiments, the magnetic nanoparticles may be referred to herein as "Curie nanoparticles," abbreviated as CNP. Magnetic nanoparticles are referred to herein as CNPs because they possess a Curie temperature above which they may temporarily lose their magnetism. In other words, the CNPs of this disclosure can generate heat energy when an alternating electromagnetic field is applied, but at a certain temperature, the heat energy generated by the CNPs may decrease or disappear because the CNPs lose their magnetism and therefore may not produce any thermal response to the applied alternating electromagnetic field. In various embodiments, the magnetic nanoparticles may have a Curie temperature, for example, ranging from 60°C to 300°C.

[0110] In various embodiments, the magnetic nanoparticles may include one or more metals. For example, magnetic nanoparticles may include iron and zinc. In another example, magnetic nanoparticles may include iron, zinc, and another metal (e.g., cobalt, manganese, or nickel). In various embodiments, the magnetic nanoparticles may be made of chemical formula A. x Zn 1-x Fe2O4 represents a material where A can be cobalt, manganese, or nickel, and x can be a value in the range of 0.4 to 0.99, 0.4 to 0.9, 0.4 to 0.8, 0.4 to 0.7, 0.4 to 0.6, 0.4 to 0.5, or 0.8 to 0.9. In various embodiments, x can be 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9.

[0111] As described above, the coating layer may include (a) a surfactant or inorganic material, and (b) a monomer or polymer miscible with the adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate. The coating layer contributes to the colloidal stability of the magnetic nanoparticles in the adhesive substrate. The coating layer does not need to form crosslinks with the adhesive substrate. The interaction between the monomer or polymer and the adhesive substrate can be non-covalent and can be primarily van der Waals attraction and dipole-dipole interaction, wherein the attractive force between the coated magnetic nanoparticles and the adhesive substrate is greater than the attraction between multiple coated magnetic nanoparticles, thus preventing the aggregation of magnetic nanoparticles and providing colloidal stability. The colloidal stability of the magnetic nanoparticles within the adhesive can also be achieved by replacing the intermediate organic shell in an organic environment (e.g., organic adhesives, such as resins).

[0112] In various embodiments, the surfactant may be formed as an organic coating layer. The thickness of the organic coating layer may be less than 10 nm. The organic coating layer may include a fatty acid having 15 to 20 carbon atoms. The fatty acid may include or may be composed of oleic acid. In various embodiments, the surfactant may include oleic acid. In various embodiments, the surfactant may be covalently bonded to the magnetic nanoparticles.

[0113] In some non-limiting embodiments, the coating layer may include an inorganic material. The inorganic material may include or be ceramic. The ceramic may include or be silica or alumina. In various embodiments, the inorganic material may include or be silica, alumina, carbon, or glass. In the resulting binder additive, the inorganic material can be formed directly on the magnetic nanoparticles, i.e., there are no organic surfactants adjacent to the inorganic material and the magnetic nanoparticles.

[0114] In various embodiments, the monomers and / or polymers may contain nucleophiles or may be nucleophiles, such as amines, hydroxyl groups, carboxylic acids, esters and / or thiols.

[0115] In various embodiments, the monomer may include an epoxy resin. The monomer may include bisphenol A diglycidyl ether and / or glycerol diglycidyl ether.

[0116] In various embodiments, the adhesive additive may be free of a hardener. In some embodiments, the monomer may also include a hardener. The hardener may include or may be dicyandiamide.

[0117] In various embodiments, the polymer may include or may be polycaprolactone.

[0118] In various embodiments, the adhesive additive may also include a carbon allotrope. The carbon allotrope may be a carbon nanotube or a carbon nanotube coil. This carbon allotrope allows for better control of magnetic induction heating by an applied magnetic field.

[0119] In various embodiments, the applied alternating electromagnetic field may have a frequency of 100 kHz to 1 MHz and / or a magnetic field strength of 50 Oe to 140 Oe.

[0120] The adhesive additive of the present invention can be used for the magnetic curing of adhesives, offering numerous advantages in terms of energy efficiency and tunable, on-demand activation. Magnetic curing involves applying a magnetic field to a magnetic material to generate a thermal response, thereby curing the adhesive. Therefore, the adhesive additive of the present invention may be referred to herein as an "adhesive modifier" or simply "modifier." The adhesive additive of the present invention provides the advantages without compromising the performance of the adhesive. For example, the adhesive additive of the present invention is miscible with the adhesive substrate. In other words, the presence of the adhesive additive does not lead to a decrease in the strength of the adhesive obtained by incorporating the adhesive additive. The adhesive strength of the adhesives disclosed herein can be in the range of 1-7 MPa.

[0121] The adhesive additive of the present invention can be uniformly distributed therein, and will not generate uneven local hot spots under the action of an alternating electromagnetic field. The adhesive additive of the present invention includes CNP, which can prevent charring, because CNP stops generating heat energy once it reaches its Curie temperature, thereby preventing the adhesive from overheating (e.g., charring).

[0122] Advantageously, since the adhesive additive of the present invention can generate heat for curing via an external magnetic field, heating and curing can be remotely controlled (without contact with the adhesive additive or the adhesive substrate). Heating with an external alternating electromagnetic field can reach the activation temperature of the magnetic adhesive in 5 minutes or less. Thus, curing can begin in 10 minutes or less and be completed within 30-60 minutes. Furthermore, processing costs and energy consumption can be reduced because the adhesive additive of the present invention can generate heat by applying a low 400 kHz frequency and a maximum magnetic field strength of 50-140 Oersted (Oe).

[0123] This disclosure also provides a magnetocurable adhesive. Therefore, the adhesive may be referred to herein as a "magnetic adhesive." This adhesive can be used to bond a range of materials, such as ceramics, polymers / plastics (e.g., PMMA (polymethyl methacrylate) and ABS (acrylonitrile butadiene styrene)), wood, and animal bones. Polymer materials, wood, and animal bones are difficult or nearly impossible to bond using conventional oven methods.

[0124] In various embodiments, the adhesive comprises the adhesive additives and adhesive substrates described in the various embodiments of the first aspect. The term "adhesive substrate" is used interchangeably with "adhesive material" herein. The embodiments and advantages described with respect to the adhesive additives of the first aspect are similarly applicable to the adhesives described herein thereafter, and vice versa. Since various embodiments and advantages of the adhesive additives and adhesives have already been described above and in the examples disclosed herein, they will not be repeated for the sake of brevity.

[0125] In various embodiments, the adhesive substrate may be a resin, which may include or may be a thermosetting material. The thermosetting material may be activated by heat generated from the magnetic nanoparticles in the adhesive additives described in the various embodiments of the first aspect to form crosslinks. The thermosetting material may include or may be an epoxy resin and bisacrylidine. Thermosetting materials with known curing activation temperatures (e.g., 60°C to 300°C) may be used. In some embodiments, the adhesive substrate may be a resin, which may include or may be a thermoplastic material. The thermoplastic material may include or may be polycaprolactone. The difference between thermosetting and thermoplastic materials is that thermosetting materials cannot be reshaped after curing, while thermoplastic materials can be reshaped by heating.

[0126] In various embodiments, the adhesive substrate may be a resin that does not contain a hardener.

[0127] In various embodiments, the weight ratio of the adhesive additive to the adhesive substrate may be 1:100 to 50:100, 10:100 to 50:100, 20:100 to 50:100, 30:100 to 50:100, 40:100 to 50:100, etc.

[0128] In this disclosure, a method for forming an adhesive additive as described in the various embodiments of the first aspect is also provided. The embodiments and advantages described with respect to the adhesive additive of the first aspect can be similarly applied to the method described herein, and vice versa. Since various embodiments and advantages of the adhesive additive and method have already been described above and in the examples disclosed herein, they will not be repeated for the sake of brevity.

[0129] The method may include providing magnetic nanoparticles comprising: (i) a metal, including iron, manganese, cobalt, nickel, and / or zinc, or (ii) a metal oxide containing a metal, including iron, manganese, cobalt, nickel, and / or zinc; mixing an aqueous solution comprising the magnetic nanoparticles with a surfactant; and mixing an organic solution comprising the magnetic nanoparticles coated with the surfactant with (i) a monomer or (ii) a polymer miscible with an adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate. It is understood that the metal oxide includes oxygen. In other words, this method can be used to form an adhesive additive having a surfactant in the coating layer.

[0130] In various embodiments, the steps of providing magnetic nanoparticles may include: mixing an alkaline solution with two precursor solutions to form an alkaline mixture, and hydrothermally treating the alkaline mixture to form magnetic nanoparticles. The alkaline solution may contain a first metal precursor, and each of the two precursor solutions may contain a second metal precursor and a third metal precursor, respectively, to form different metals in the magnetic nanoparticles. In other words, the first metal precursor, the second metal precursor, and the third metal precursor are different. Each of the first metal precursor, the second metal precursor, and the third metal precursor may differently contain iron, manganese, cobalt, nickel, or zinc. Therefore, the metal in the magnetic nanoparticles formed from the first metal precursor, the second metal precursor, and the third metal precursor may include iron, manganese, cobalt, nickel, and / or zinc. As a non-limiting example, the alkaline solution may contain an iron precursor for forming iron in the magnetic nanoparticles. The two precursor solutions may each contain manganese and zinc as the second and third metal precursors, respectively. Magnetic nanoparticles obtained from such metal precursors may contain iron, manganese, and zinc.

[0131] In various embodiments, mixing an aqueous solution comprising the magnetic nanoparticles with a surfactant may include: dispersing the magnetic nanoparticles in an aqueous medium, and mixing the aqueous medium with the surfactant.

[0132] In various embodiments, the surfactant may include or may be a fatty acid having 15 to 20 carbon atoms.

[0133] In various embodiments, mixing an organic solution comprising magnetic nanoparticles coated with the surfactant with (i) a monomer or (ii) a polymer may include: dispersing the magnetic nanoparticles coated with the surfactant in an organic medium; dissolving the monomer or polymer in an organic solvent to form a monomer solution or a polymer solution, respectively; and mixing the monomer solution or polymer solution with the organic medium containing the magnetic nanoparticles coated with the surfactant.

[0134] In various embodiments, the method may further include: adding the adhesive additive to another resin; and mixing the carbon allotrope with the other resin containing the adhesive additive.

[0135] This disclosure provides another method for forming an adhesive additive as described in the various embodiments of the first aspect. The embodiments and advantages described with respect to the adhesive additive of the first aspect can be similarly applied to the methods described herein, and vice versa. The embodiments and advantages described with respect to the other methods described above can be similarly effective and / or applicable to the methods described herein, and vice versa. Where applicable to the various embodiments and advantages of the adhesive additive described above and the embodiments disclosed herein, they will not be repeated for the sake of brevity. Where applicable to the various embodiments and advantages of the other methods described above and the examples disclosed herein, they will not be repeated for the sake of brevity.

[0136] This method may include: providing magnetic nanoparticles comprising: (i) a metal, including iron, manganese, cobalt, nickel, and / or zinc, or (ii) a metal oxide containing a metal, including iron, manganese, cobalt, nickel, and / or zinc; forming one or more surfactants on the magnetic nanoparticles; forming an inorganic precursor on the one or more surfactants; calcining the magnetic nanoparticles together with the inorganic precursor to remove the one or more surfactants and form an inorganic material coated on the magnetic nanoparticles; and mixing an organic mixture comprising magnetic nanoparticles coated with the inorganic material with (i) a monomer or (ii) a polymer miscible with an adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate. In other words, this method can be used to form an adhesive additive having an inorganic material in the coating layer.

[0137] In various embodiments of this method, as well as in other methods described above, providing magnetic nanoparticles may include: mixing an alkaline solution with two precursor solutions to form an alkaline mixture, wherein the alkaline solution contains a first metal precursor, each of the two precursor solutions contains a second metal precursor and a third metal precursor, wherein the first metal precursor, the second metal precursor, and the third metal precursor form different metals in the magnetic nanoparticles; and hydrothermally treating the alkaline mixture to form the magnetic nanoparticles.

[0138] In various embodiments of this method, one or more surfactants may include oleic acid, hexadecyltrimethylammonium bromide, and / or 1-butanol. One or more surfactants in this method facilitate the coating of inorganic materials onto magnetic nanoparticles. One or more surfactants may also include fatty acids having 15 to 20 carbon atoms, wherein oleic acid is a non-limiting example. One or more surfactants may include at least two surfactants. Other suitable surfactants that facilitate the coating of inorganic materials onto magnetic nanoparticles may be used. Non-limiting examples of surfactants are shown in the Examples section.

[0139] In various embodiments of this method, forming an inorganic precursor on one or more surfactants may include mixing magnetic nanoparticles having the one or more surfactants with an inorganic precursor for forming the inorganic material. The inorganic precursor for forming alumina as an inorganic material may include aluminum isopropoxide, aluminum hydroxide, and / or alumina. The inorganic precursor for forming silica as an inorganic material may include tetraethyl orthosilicate. The inorganic precursor for forming carbon as an inorganic material may include starch, glucose, and / or activated carbon (e.g., activated charcoal). The inorganic precursor for forming glass as an inorganic material may include fused silica, bioglass, and / or sodium calcium phosphosilicate. In various embodiments, the inorganic precursor may include tetraethyl orthosilicate, aluminum isopropoxide, aluminum hydroxide, alumina, starch, glucose, activated carbon, fused silica, bioglass, and / or sodium calcium phosphosilicate.

[0140] In various embodiments of this method, calcining the magnetic nanoparticles together with the inorganic precursor to remove the one or more surfactants and form an inorganic material coated on the magnetic nanoparticles may include heating the magnetic nanoparticles and the inorganic precursor at a temperature of at least 500°C, 500°C to 600°C, 550°C, etc.

[0141] In various embodiments of this method, mixing an organic mixture comprising magnetic nanoparticles coated with the inorganic material with (i) a monomer or (ii) a polymer may include: dispersing the magnetic nanoparticles coated with the inorganic material in an organic medium; dissolving the monomer or polymer in an organic solvent to form a monomer solution or a polymer solution, respectively; and mixing the monomer solution or polymer solution with the organic medium containing the magnetic nanoparticles coated with the inorganic material. The steps for preparing monomer solutions and polymer solutions described in the other methods above are applicable to this method.

[0142] In various embodiments of this method, as described in the other methods above, the method may further include: adding the adhesive additive to another resin; and mixing the carbon allotrope with the other resin containing the adhesive additive.

[0143] To demonstrate the various embodiments described above, some non-limiting examples are briefly discussed below, and will be discussed in more detail in the further examples section below.

[0144] The development of several magnetic adhesives involves readily available adhesives and BADGE-DICY (bisphenol A diglycidyl ether-dicyandiamide). These examples may involve the addition of CNPs and adhesives in proportions of 10 to 50 wt.%. Specifically, the proportions of the components may be CNP:ES558 = 15-30 wt.%, CNP:TIM 813HTC = 30 wt.%, CNP:BADGE-DICY = 30 wt.%, CNP:CaproGlu = 10 wt.% and 50 wt.%, etc. Overall, this disclosure provides an improved method superior to existing methods. The adhesive additives, adhesives, and methods of the present invention can be considered as a one-pot adhesive platform that allows for non-contact “magnetic curing” by exposure to an alternating electromagnetic field. Curie nanoparticles (CNPs) interact with the alternating electromagnetic field, where hysteresis heats the surrounding fluid or resin. An advantage of this CNP is its designable temperature limit, which can be controlled, for example, by the Mn / Zn ratio. Temperature control prevents charring, a detrimental property of other magnetic nanoparticles. The Mn / Zn ratio can be adjusted using hydrothermal synthesis feedstocks. 0.4 Zn 0.6 With Mn 0.7 Zn 0.3 The ratios are described in the Examples section, and they span a cutoff temperature range of 100-250°C, overlapping with most thermosetting resins.

[0145] This disclosure provides an additional conversion method that controls the temperature (e.g., Mn) of CNPs by introducing carbon allotropes, such as carbon nanotubes (CNTs) and carbon nanocoils (CNCs). 0.9 Zn 0.1 The incorporation of CNT / CNC improves thermal conductivity and magnetic field shielding, thereby enhancing the ability to prevent charring and localized heating.

[0146] To prevent aggregation and maximize storage stability, the synthesized CNP can be coated with a surfactant, such as oleic acid (OA). For phase transfer into the resin, the CNP / OA is functionalized with resin monomers. This disclosure provides non-limiting examples of resins including epoxy resins (bisphenol A diglycidyl ether, BADGE, and glycerol diglycidyl ether, GDE) and polycaprolactone (PCL, MW: 300 Da). The replacement of the intermediate organic shell achieves the purpose of bonding with the resin / adhesive during thermosetting initiation.

[0147] Advantageously, this CNP can be used to cure one-component epoxy adhesives via a non-contact alternating electromagnetic field. This modifier method allows for its incorporation into existing thermosetting adhesive formulations. The magnetic curing of this invention provides a more cost-effective activation method because it directly heats the adhesive without heating the surface / material to be bonded.

[0148] Here, single-component epoxy adhesives and bio-adhesives are cured on plastics, wood, ceramics, and animal bones via AMF activation or “magnetic curing,” which is of great significance in the medical, sports, automotive, and aerospace industries.

[0149] The structure-property relationship of the proportion of metal in CNP, the percentage loading of adhesive additives, the percentage loading of CNTs / CNCs, and the magnetic field strength is evaluated based on material properties and lap shear adhesion on industrially relevant surfaces / materials.

[0150] The word “substantially” does not exclude “completely”, for example, a composition that is “substantially free” of Y can be completely free of Y. The word “substantially” may be omitted from the definitions in this disclosure if necessary.

[0151] In the context of various embodiments, the articles “a,” “an,” and “the” used with respect to features or elements include references to one or more of the features or elements.

[0152] In the context of various embodiments, the term “about” or “approximately” applied to numerical values ​​includes both precise values ​​and reasonable differences.

[0153] As used herein, the term “and / or” includes any and all combinations of one or more of the listed related items.

[0154] Unless otherwise stated, the terms “include” and “contain” and their grammatical variations are intended to indicate “open-ended” or “inclusive” language, which includes listed elements but also allows for the inclusion of additional, unlisted elements. Example

[0155] This invention relates to an adhesion technology that can adhere to a variety of materials.

[0156] Traditional one-component adhesives typically cure via moisture, heat, and light. This curing method often limits applications to specific surfaces / materials, is inefficient in manufacturing processes, and mostly relies on indirect activation. To overcome these limitations, this paper discloses a one-pot epoxy adhesive capable of non-contact curing using an alternating electromagnetic field (AMF). This method provides an energy-efficient approach to on-demand adhesion via self-regulating Curie nanoparticles, known as magnetic curing. For example, Mn... x Zn 1-xFe2O4 Curie nanoparticles (CNPs) are incorporated into epoxy adhesives, and AMF is applied on top of them. The thermosetting resin cures within minutes with minimal temperature rise of the substrate. In-situ heating can be controlled by the CNP formulation, CNP loading, and the strength of the added AMF. Under certain conditions, internal temperatures can reach 160°C within minutes, allowing curing of most commercial epoxy adhesives without significant resin charring. Maximum lap shear bond strength exceeds 6.5 MPa. Magnetocurbation has been demonstrated on wood, ceramics, and plastics, attracting significant interest in the sports, automotive, and aerospace industries.

[0157] More specifically, to overcome the limitations of traditional magnetosetting adhesives, it is necessary to address the issues of colloidal stability and hotspots caused by aggregation. This paper describes the use of surface-functionalized Curie magnetic nanoparticles (CNPs) as magnetosetting additives in thermosetting resins. This allows one-pot adhesive formulations to activate substrate adhesion and adhesive crosslinking upon exposure to AMF. The adhesion of the adhesive can be precisely tuned to the Curie nanoparticle cutoff temperature by controlled heating, thereby allowing for the elimination of charring while bonding heat-sensitive substrates. Curie magnetic nanoparticles may comprise metals or metal oxides. In other words, Curie magnetic nanoparticles may consist of a single metal, a combination of metals, a metal oxide having a single metal, or a metal oxide containing multiple metals. In some non-limiting examples, Curie magnetic nanoparticles may be metallic magnetic nanoparticles formed from Fe, Mn, Co, Ni, Zn, or combinations thereof (e.g., Fe-Co, Fe-Mn-Zn). In some non-limiting examples, Curie magnetic nanoparticles may be metal oxide magnetic nanoparticles containing one or more metals, such as FeO, MnO, FeCoO3, FeMnZn oxides.

[0158] To demonstrate this, we investigated the following structure-property relationships. (1) Mn x Zn 1-x Fe₂O₄ CNPs were synthesized via a simple hydrothermal method, exhibiting controllable particle size (<20 nm) and Curie temperature (Tc). Mn x Zn 1-x (2) The Curie temperature of Fe2O4 ferrite can be finely adjusted by changing the ratio of Mn to Zn. (3) Organic coating and surface functionalization of CNP with oleic acid and bisphenol A diglycidyl ether improved the long-term stability of CNP colloid in liquid epoxy resin / adhesive. (4) Curie nanoparticles were incorporated into the adhesive and AMF induction (low-power system) to obtain a fast-curing formulation while preventing surface / material hot spots and charring. (5) Finally, the loading of CNP, the thermal and physical properties of the adhesive, and the selection of adhesive materials allow for adjustment of mechanical properties and shear bond strength when exposed to AMF.

[0159] The Curie nanoparticles, adhesives, and methods for forming Curie nanoparticles of the present invention will be further described in detail by way of non-limiting embodiments, as follows.

[0160] Example 1A: Materials

[0161] One-component epoxy adhesives (ES558 Permabond and TIM-813HTC-1HP) were purchased from Permabond (USA) and TIMTRONICS (USA), respectively. Manganese(II) chloride tetrahydrate (MnCl2·4H2O, 99%), anhydrous zinc chloride (ZnCl2, 98%), ferric chloride (III) hexahydrate (FeCl3·6H2O), oleic acid (OA), bisphenol A diglycidyl ether (BADGE), and dicyandiamide (DICY) were all purchased from Sigma Aldrich and used as is. Wooden rods and polymethyl methacrylate (PMMA) sheets were purchased from Art Friend (Singapore). Acrylonitrile butadiene styrene (ABS-100) for 3D printing was purchased from Additive 3D Asia (Singapore). Borosilicate microscope slides (25.4 mm x 76.2 mm, thickness 1–1.2 mm) were purchased from Newton 101 (Singapore).

[0162] Example 1B: Method - Synthesis of Curie Nanoparticles (CNP), a Magnetically Curied Adhesive Modifier

[0163] With the composition of Mn x Zn 1-x Taking Fe2O4 (e.g., x = 0.4 to 0.9) CNP as an example, a magnetic solidification additive (also known as an adhesive modifier) ​​was synthesized using a hydrothermal method. In short, to synthesize 4g of Mn... 0.7 Zn 0.3Fe₂O₄ particles were prepared into 10 mL solutions of 70 mmol MnCl₂·4H₂O (2.22 g) and 30 mmol ZnCl₂ (0.654 g) in distilled water (DI water). 200 mmol FeCl₃·6H₂O (8.64 g) was dissolved in 40 mL of DI water, and NaOH (4 M) solution was added dropwise until the pH reached 8. The resulting brown precipitate was centrifuged and washed three times with DI water, then transferred to a beaker equipped with a mechanical stirrer. The separately prepared Mn and Zn salt solutions were then added to the beaker, and the mixture was vigorously stirred while adding NaOH solution dropwise until the pH of the reaction mixture reached 12. The resulting slurry was decanted into a PTFE-lined stainless steel autoclave (4748A Parr, USA) and placed in an oven at 190 °C for 2 hours. The resulting nanoparticles were washed three times with DI water and twice with ethanol (96%), then vacuum dried for 48 hours. Vacuum-dried granules were obtained with a yield of 95% (3.8 g). All other CNPs (e.g., Mn) were also obtained. 0.4 Mn 0.5 Mn 0.6 Mn 0.8 and Mn 0.9 The CNPs were synthesized in a similar manner with yields of 95-97% and stored under vacuum. The structure, function, and magnetism of all synthesized CNPs were characterized using XRD, ICP-MS, TGA, FTIR, and PPMS (physical property measurement system) before further modification (see [link to documentation]). Figures 1A to 1F and Figures 2A to 2C ).

[0164] Example 2A: Method - Surface modification of Curie nanoparticles with oleic acid (OA) and bisphenol A diglycidyl Functionalization with ethers and polycaprolactone (PCL) (BADGE)

[0165] CNPs were coated with the surfactant oleic acid to prevent particle aggregation. 2 g of CNPs were dispersed in 80 mL of deionized water and placed in an ultrasonic water bath (Elmasonic S 60H, Germany) for 20 minutes to disrupt any aggregates. 4 mL of OA was added to the solution and sonicated for 10 minutes. The solution was then heated at 80 °C for 1 hour with mechanical stirring at 400 rpm. The resulting solution was washed 3-4 times with ethanol, and the OA-coated CNPs were separated using a permanent magnet. Oleic acid-coated particles (Mn...) x Zn 1- x Fe2O4 / OA was used as is for further functionalization of bisphenol A diglycidyl ether and polycaprolactone.

[0166] The above Mn x Zn 1-xFe₂O₄ / OA particles were dispersed in 10 mL of tetrahydrofuran (THF) and sonicated for 30 min. Then, a solution of 10 g of bisphenol A diglycidyl ether (BADGE) in 20 mL of THF was added to the above solution, and the particles were sonicated again for 30 min. This solution was maintained for 16 h until the nanoparticle surface was completely wetted by BADGE. Next, the particles were washed with tetrahydrofuran and acetone, separated using a permanent magnet, and vacuum dried for 24 h to obtain Mn. x Zn 1-x Fe2O4 / OA / epoxy nanocomposites. Based on dry particle weight, a yield of 1.94 g of surface functionalization was observed. The same procedure was repeated with polycaprolactone (molecular weight (MW) 300 Da) for Mn... x Zn 1-x Fe2O4 / OA particles were functionalized. The amounts of OA, BADGE, and PCL anchored on the surface of the functionalized particles were calculated by TGA, and the bonded functional groups were confirmed by FTIR (see [link to TGA]). Figures 3A to 3F and Figures 4A to 4F ).

[0167] Example 2B: Method - Alternating electromagnetic field heating of functionalized CNPs

[0168] It employs a D5 series alternating electromagnetic field (AMF) generator (MOW single-frequency F1 driver) from nB nanoScale Biomagnetics in Spain, equipped with a solenoid coil with a fixed frequency of 400kHz (S 56 AMF (Amphipathic Flavor) evaluation was performed on coated CNPs dispersed in BADGE at concentrations ranging from 5 to 140 Oe under an applied magnetic field. The temperature under AMF was measured using a fiber optic temperature sensor (Neoptix T1S-01-PT15, USA). All samples were freshly prepared by dispersing an appropriate amount of CNP in BADGE and sonicating for 60 minutes.

[0169] Example 2C: Methods - Sample Preparation via 3D Printing

[0170] All ABS specimens were printed using a Cubicon 3DP-110F printer. The T-shaped geometry of the ABS specimens was created using Solidworks and saved as a stereolithography (STL) file. The STL file was opened in the 3D printer software, printing parameters were set, and the G-code was exported to the printer. The dimensions and printing parameters of the ABS specimens are listed in Table 1.

[0171] Table 1 - Dimensions of ABS specimens and parameters for 3D printing.

[0172]

[0173] Example 2D: Method - Curing Adhesives via AC Magnetic Field

[0174] Commercially sourced (Permabond ES558 and TIMTRONICS 813-HTC) and mixtures of BADGE and dicyandiamide (100:12) were used for the magnetocuring of one-component epoxy adhesives. Different loadings of CNP (15-30 wt.%) relative to the adhesive / BADGE ratio were used as fillers for the magnetocuring of wood, glass, PMMA, and ABS samples. Samples were cured at a magnetic field strength of 140 Oe and a frequency of 400 kHz.

[0175] Example 2E: Structural and magnetic characterization of CNPs using the method

[0176] X-ray diffraction (XRD) characterization was performed using a Bruker D8 Advance powder diffractometer with Cu-κα radiation at 40 kV and 40 mA, 2θ = 20° to 70°, and a scan rate of 5° / min. -1 Phase identification was performed by matching the diffraction peak positions and relative intensities with a reference JCPDS file. The crystallite size was calculated using the Scherrer formula D = 0.9λ / (βcosθ), where λ is the wavelength of the X-rays. β is the full width at half maximum (FWHM) of the 311 diffraction peak, and θ is the Bragg angle.

[0177] Example 2F: Elemental Composition of Method-CNP

[0178] The elemental composition of the synthesized Curie nanoparticles was measured using an Agilent 7700 inductively coupled plasma mass spectrometer (ICP-MS). Samples were prepared by dissolving the particles in a 3:1 mixture of hydrochloric acid (HCl) and nitric acid (HNO3), followed by dilution with Millipore water. The sample solutions were filtered using a 0.2 mm pore size syringe filter (Agilent) prior to analysis.

[0179] Example 2G: Method - Measurement of the physical properties of CNP

[0180] The magnetism of the CNP was measured using a PPMS (EverCool-II, QuantumDesign, USA) equipped with a vibrating sample magnetometer and an oven (model P527). The room-temperature hysteresis curve of the CNP was recorded up to an applied magnetic field of 2T. The relationship between magnetization and temperature was measured over a temperature range from room temperature to 600°C at different applied magnetic field strengths from 50 Oe to 140 Oe.

[0181] Example 2H: Method - Quantization of Coatings on CNPs

[0182] Thermogravimetric analysis (TGA) was used to measure the thermal degradation of bare Curie nanoparticles and the amounts of OA and BADGE coated on the nanoparticles. TGA was performed using a TGA Q500 TA instrument at 10 °C / min over a temperature range of 30 to 900 °C. -1 The heating rate was carried out under a nitrogen atmosphere.

[0183] Example 2I: Colloidal Stability of CNP

[0184] The stability of Curie nanoparticles was assessed using a Zetasizer (Zetasizer Nano, Malvern Instruments, UK) with 173° backscattering measurements. The colloidal stability of the functionalized nanoparticles dispersed in ethanol over time was investigated by measuring the average count rate (thousands of counts per second, kcps). 5 mg of CNP (Mn) was added... x Zn 1-x Fe2O4 / OA / BADGE was dispersed in 5 mL of ethanol and sonicated for 1 hour. Ten measurements were recorded for ten repeated operations for all samples.

[0185] Example 2J: Method - Curing temperature from differential scanning calorimetry (DSC)

[0186] DSC analysis was performed using a synchronous DSC / TGA system, TA equipment, and SDT Q600. The analysis was conducted at 10°C / min intervals within a temperature range of 30 to 600°C. -1 The heating rate was analyzed.

[0187] Example 2K: Confirmation of CNP functionalization and crosslinking percentage

[0188] Using a general-purpose Zn-Se ATR (attenuated total internal reflection) accessory at 500-4000cm -1 FTIR (Perkin Elmer Frontier) measurements were performed on functionalized CNPs. FTIR spectra of CNPs and functionalized CNPs were recorded using the potassium bromide pelleting method. 3–4 mg of CNP was added to 20 mg of potassium bromide (KBr) and mixed in a mortar. The mixture was then pelleted using a 13 mm potassium bromide module under 10 tons of pressure using a potassium bromide hydraulic press (Specac, UK). FTIR measurements of the adhesive and cured adhesive were performed using a general-purpose ATR apparatus with ZnSe crystals. Each measurement was a cumulative total of 32 scans at a resolution of 4 cm⁻¹. -1 .

[0189] Example 2L: Method - Overlap Shear Adhesion

[0190] Magnetization was successfully demonstrated on various surfaces / materials: glass, wood, ABS, and PMMA. 125 mg of adhesive was applied to a 1 x 1 cm area. 2The surface / adhesion area was measured. The sample thickness on all surfaces was maintained at approximately 0.45 mm (±0.05 mm). The adhesive material was tightly clamped together with transparent tape. The lap shear adhesion force test of the magnetocured samples was performed on a static mechanical testing instrument (Criterion MTS C43, USA) using a 2.5 kN force sensor at a test speed of 3 mm / min.

[0191] Example 2M: Methods - Statistical Analysis

[0192] All experiments were repeated three times, and the data presented here are mean ± SD (n = 3). Significance was assessed by Tukey-corrected one-way ANOVA using OriginPro 2018b 64-bit software, where p < 0.05. (*) was considered statistically significant.

[0193] Example 2N: Method - Surface modification of Curie nanoparticles with inorganic materials

[0194] Fe3O4 nanoparticles are used as a non-limiting example to demonstrate the use of inorganic material coatings on CNPs. Other metals and metal oxides can be used. The metals and metal oxides can contain more than one metal.

[0195] Fe3O4 nanoparticles were synthesized via a modified thermal decomposition method. In this embodiment, 1.41 g of Fe(acac)3 was added to a mixture of dibenzyl ether (30 mL), oleic acid (0.6 mL), and oleylamine (1.31 mL). The suspension was then heated to 120 °C and maintained at this temperature under a nitrogen atmosphere for 30 minutes. The mixture was then rapidly heated to 280 °C and maintained at this temperature for 4 hours. After cooling the suspension to room temperature, the solution was centrifuged at 10,000 rpm for 15 minutes and washed three times with ethanol. Finally, the oleic acid-stabilized Fe3O4 nanoparticles were dispersed in chloroform for further use.

[0196] The Fe3O4 nanoparticles were then subjected to a "phase transfer" step, which involved coating them with one or more other surfactants that facilitated the subsequent deposition of inorganic precursors onto the Fe3O4 nanoparticles to form an inorganic material. 1 mL of the prepared Fe3O4 nanoparticles dispersed in chloroform was mixed with an aqueous solution containing 0.06 g of cetyltrimethylammonium bromide (CTAB). The resulting crude emulsion was sonicated for 1 hour and then heated to 70°C for 10 minutes to evaporate the chloroform, thereby forming a stable, transparent solution containing water-dispersible Fe3O4 nanoparticles. To remove excess surfactant from the nanoparticle suspension, the solution was cooled to 5°C and then centrifuged to separate the excess surfactant.

[0197] CNPs containing inorganic materials (e.g., silica) were then synthesized. Magnetic mesoporous silica CNPs were prepared using a modified reverse microemulsion method involving the use of CTAB / 1-butanol / water / cyclohexane as a surfactant / co-surfactant / aqueous phase / organic phase. 2 g of CTAB was added to a mixture of 1-butanol and cyclohexane at room temperature. Subsequently, 3 mL of an aqueous suspension containing CTAB-stabilized Fe3O4 nanoparticles and urea was added to the above solution to form a transparent microemulsion. A certain amount of tetraethyl orthosilicate (TEOS) was then added to the microemulsion under vigorous stirring. The TEOS-containing microemulsion was transferred to a 75 mL PTFE-lined autoclave and heated at the desired temperature (e.g., 70°C to 170°C) for 12 hours. The formed core-shell Fe3O4@SiO2 nanoparticles were collected by centrifugation (4000 rpm), washed three times with ethanol and water, and then dried in an oven at 60°C. Finally, to extract CTAB from the silica shell, the nanocomposite material was calcined at a temperature of at least 500°C (e.g., 550°C) for 6 hours. Calcination removes other surfactants used as described above through heat.

[0198] Subsequently, monomers or polymers may be functionalized on CNPs coated with inorganic materials according to the steps described in the foregoing embodiments, such as Example 2A.

[0199] Example 3A: Summary of Results

[0200] This one-pot binder platform aims to achieve non-contact “magnetic curing” by exposure to an alternating electromagnetic field. Curie nanoparticles (CNPs) interact with the alternating electromagnetic field, and the hysteresis phenomenon heats the surrounding fluid. CNPs offer the advantage of a designable temperature limit, controlled by a final Mn / Zn ratio. Temperature control prevents charring, a detrimental property of other magnetic nanoparticles. The Mn / Zn ratio is adjusted using hydrothermal synthesis feedstock and subsequently evaluated using X-ray diffraction. Mn selection... 0.4 Zn 0.6 With Mn 0.7 Zn 0.3The ratios of these components are due to their overlap with the cutoff temperatures of 100–250 °C, which are common to most thermosetting resins. To prevent aggregation and maximize storage stability, the synthesized CNPs were surface-functionalized with oleic acid and BADGE. Oleic acid (OA) was used for nanoparticle synthesis because it forms a dense protective layer that stabilizes the nanoparticles. The surface coating of BADGE was designed to contact the resin during thermosetting initiation. The structure-property relationships of CNP elemental ratios, additive loading percentages, and magnetic field strength were evaluated based on material properties and lap shear adhesion forces on industrially relevant surfaces / materials. Material and resin temperatures during exposure to AMF were independently evaluated using fiber optic probes. Resin activation and growth were characterized before and after magnetic curing using TGA, DSC, and infrared spectroscopy to further confirm the chemical crosslinking.

[0201] Example 3B: Results - XRD confirms the spinel structure and nanocrystal size of CNP

[0202] Mn was determined by XRD pattern analysis. x Zn 1-x The structure of Fe2O4 CNP ( Figure 1A Diffraction pattern analysis confirmed the formation of a cubic spinel structure in all samples. Experimental peaks matched their respective JSPDS files, and the hkl plane was calculated using Topas software. Strong crystallization peaks observed at 2θ(hkl) values ​​of 29.9 (220), 35.08 (311), 42.6 (400), 52.9 (422), 56.3 (511), and 61.9° (440) matched experimental data for the zinc-iron spinel structure (JCPDS number 10-0467), indicating the presence of Mn in all samples. x Zn 1-x The small diffraction peak at 2θ 33.61° in Fe₂O₄ is due to the presence of a small portion of hematite (α-Fe₂O₃) phase in the sample. Considering that the strongest diffraction peak at 2θ 35.08° corresponds to plane 311, the crystal size of the particles was calculated using the Scherrer formula (D = 0.9λ / (βcosθ)). The increase in Mn content led to an increase in the crystallite size. Mn was found to... 0.4 Mn 0.5 Mn 0.6 and Mn 0.7 The crystal sizes are 9.5, 13.5, 13.7, and 13.8 nm, respectively. Figure 1B ).

[0203] Example 3C: Results - The empirical ratio of Mn to Zn differs from the raw material ratio by 9% to 18%.

[0204] Four different Mn groups were identified by ICP-MS. x Zn 1-x The Mn / Zn ratio of the Fe2O4 composition. Figure 1CIn the figure, the measured mol% ratio of manganese (Mn) and zinc (Zn) was determined by ICP-MS, and the results were compared with scalar values. The ICP-MS results showed that Mn... 0.4 Mn 0.5 Mn 0.6 and Mn 0.7 The actual mole fractions differed from the scalar mole fractions by 18%, 15%, 12%, and 9%, respectively. Typically, Zn cations are uniformly distributed between tetrahedral and octahedral sites. Therefore, Mn is expected to... 2+ Compared to Zn 2+ More likely to be absorbed by atomic nuclei. Zn 2+ The radius is smaller than Mn 2+ The radius may be the cause of Zn 2+ The reason for the greater absorption into the crystal lattice. The results also show that the difference between the scalar and experimental values ​​decreases as the Mn content in the particles increases. For particles with lower Mn content (Mn... 0.4 More Zn particles can be observed. 2+ The combination of ions.

[0205] Example 3D: Results - Magnetization and Curie temperature (Tc) increase with increasing manganese content.

[0206] The magnetic order of ferrimagnetic spinel is mainly due to the superexchange interaction mechanism between metal ions in the A and B sublattices. Nonmagnetic Zn preferentially occupies the A sites. 2+ The substitution of ions reduces the exchange interactions between the A and B sites. Therefore, the magnetism of CNPs can be tuned by changing the Mn / Zn ratio. Figure 1D The curves of magnetization measured at room temperature versus an applied magnetic field are shown. Mn 0.4 Mn 0.5 Mn 0.6 and Mn 0.7 The saturation magnetization (Ms) of the CNPs were 33 emu / g, 40 emu / g, 46 emu / g, and 60 emu / g, respectively. All particles exhibited superparamagnetic behavior with negligible hysteresis. The room-temperature coercivity (Hc) of all samples is expressed as... Figure 1D The illustrations and Table 2 below show Hc with Mn. 2+ The content decreases with increasing Mn content. 0.7 The Hc value of the particles is as low as 2.4 Oe.

[0207] Table 2 - CNP(Mn) x Zn 1-x Magnetic properties of Fe2O4

[0208]

[0209] * indicates that the effective anisotropy constant is calculated using the following relationship: T B =KV / 25κ B T B = Barrier temperature, K = Anisotropy constant, V = Particle volume, κ B = Boltzmann constant.

[0210] Mn x Zn 1-x The increase in Mn concentration in Fe2O4 CNP leads to M s The increase in M. s This increase is due to changes in composition, and can also be attributed to changes in Mn. 2+ (5μ B The magnetic moment of the ion is higher than that of Fe. 2+ (4μ B ) and Zn 2+ (0μ B The magnetic moment of the ions is used to explain this. For Curie temperature measurements, the normalized magnetization of the CNP in temperature-dependent manner under an applied magnetic field of 100 Oe was recorded in the temperature range from room temperature to 400 °C. Figure 1E CNPs do not exhibit a sharp transition at the Curie temperature. This broad distribution of Curie temperature is frequently observed in fine magnetic nanoparticles. In this case, the spontaneous magnetization (M) is related to (Tc-T). β Proportional, the critical exponent is β = 1 / 3. Therefore, M 3 It is plotted relative to temperature; the Tc of all CNPs is from M. 3 Temperature map by M 3 It is determined by extrapolation to zero. Mn 0.4 Mn 0.5 Mn 0.6 and Mn 0.7 The Tc values ​​were 61℃, 115℃, 138℃ and 237℃, respectively. Figure 1E Tc with Mn x Zn 1-x The increase in Mn% in Fe2O4 CNP is due to the enhanced total magnetic interaction within the unit cell. We also measured Mn% at different magnetic field strengths of 50Oe, 80Oe, 100Oe, and 140Oe. 0.7 Zn 0.3 Temperature dependence of the magnetization (MT) of Fe2O4 Figure 1F The magnetization at room temperature increases with increasing magnetic field strength, which is related to the higher AMF heating of these CNPs at 140 Oe (see Example 3J). The properties of the MT curves vary with the applied magnetic field, which is related to the need for more thermal energy to randomize the magnetic spin under high applied magnetic fields.

[0211] Example 3E: Results - Confirmation of CNP's Superparamagnetism by Low-Temperature Magnetism Measurements

[0212] It is known that zero-field cooling (ZFC) and field cooling (FC) experiments can determine the barrier temperature (T) of magnetic nanoparticles. B In ZFC measurements, the CNP was cooled from 400 K to 5 K without an external magnetic field. Once 5 K was reached, the magnetization was determined to vary with increasing temperature under an external magnetic field. For FC measurements, the CNP was cooled from 400 K to 5 K under an external magnetic field of 140 Oe. The magnetization was then recorded in two modes: temperature increasing from 5 K to 400 K, termed field-cooled heating (FCW), and temperature decreasing from 400 K to 5 K, termed field-cooled cooling (FCC). Figure 6A The ZFC, FCC, and FCW magnetizations of all CNPs were plotted in the temperature range of 5–400 K under an external magnetic field of 140 Oe. For all samples, the ZFC magnetization increased with increasing temperature, exhibiting a trend towards the blocking temperature (T0). B The maximum value is centered on a wide range. This peak temperature in the ZFC curve indicates the transition from a magnetically blocked state at low temperatures to a superparamagnetic state at high temperatures. At a magnetic field of 140 Oe, Mn... 0.4 Mn 0.5 Mn 0.6 and Mn 0.7 T B They are 84, 125, 229, and 260K respectively, such as Figure 6A As shown by the black vertical arrow in the image. With Mn x Zn 1-x The increase of Mn content in Fe2O4, T B The shift to higher temperatures is due to Mn 2+ Strong magnetic anisotropy of ions. When CNPs are cooled to 5K without an external magnetic field, the net magnetic moments of the CNPs align along the easy axis to obtain a local minimum potential energy. The magnetic anisotropy of nanoparticles manifests as an energy barrier to maintain the magnetization direction along the easy axis. As the temperature increases from 5K, the CNPs are thermally activated and begin to align along an external magnetic field, which causes the magnetization to increase with increasing temperature. The magnetic anisotropy barrier at the blocking temperature (T B The magnetization is overcome by thermal energy, leading to a superparamagnetic state. FCW and FCC magnetization follow the same path and decrease with increasing temperature; they reach an irreversible temperature (T0). irr ( ) merged with ZFC magnetization. T irr This is related to the obstruction caused by larger (or aggregated) particles. Therefore, it can be seen from T irr -T B Mr / Ms qualitatively estimates particle size distribution and inhomogeneity. Higher T irr -T B and Mr / M s Values ​​that result in higher inhomogeneity are summarized in Table 2 above. Mn 0.6 and Mn 0.7 T irr They are 278K and 300K respectively. Figure 6B The coated Mn is shown 0.7 The magnetization of ZFC, FCC, and FCW in an external magnetic field range of 100 Oe to 500 Oe and a temperature range of 5–400 K. Under an applied magnetic field of 140 Oe, T B T irr and the coated Mn 0.7 The difference (T) between CNPs irr -T B The value of T is lower than that of the corresponding uncoated particles, which may be related to the reduced attraction between coated CNPs. It can also be noted that T increases with increasing applied magnetic field. B and T irr They all move towards lower temperatures, which is a characteristic of superparamagnetic particles.

[0213] Example 3F: Results - Surface functionalization of oleic acid and epoxy confirmed by infrared spectroscopy

[0214] Functional groups present on CNP, oleic acid, BADGE, and surface-modified CNP, such as Figures 3A to 3C As shown. Exposed Mn x Zn 1-x The FTIR spectra of Fe2O4 (x = 0.5, 0.6, and 0.7) CNP at 560 cm⁻¹ -1 There is a sharp peak at 3400 cm⁻¹, which corresponds to the characteristics of ferrite (Fe-O-Fe). -1 and 1642cm -1 Stretching vibrations and HOH shear vibrations from free or absorbed hydroxyl groups were also observed. Figure 3A ). Figure 3B and Figure 3C The net OA, BADGE, OA+BADGE and Mn were described. x Zn 1-x FTIR spectra of mixtures of Fe₂O₄ / oleic acid / BADGE (x = 0.5, 0.6, and 0.7). The peaks of OA and BADGE are observed to be very close and overlapping. At 2852 cm⁻¹... -1 and 2924cm -1 The two sharp peaks at the position represent the symmetric and asymmetric stretching vibrations of -CH2 and -CH3, confirming the presence of oleic acid. Figure 3C 1720cm -1 and 1295cm -1The peak at 2962 cm⁻¹ is due to the stretching of the C=O and CO groups in the carboxyl group of oleic acid. The CH group in the methylene group reaches this peak at 2962 cm⁻¹. -1 and 2927cm -1 Bending vibration at 830cm and -1 and 725cm -1 The presence of an ethylene oxide ring peak confirms the functionalization of BADGE.

[0215] Example 3G: Results - Surface functionalization of OA and BADGE accounted for 20 wt% of CNP mass.

[0216] The amounts of oleic acid and BADGE coated on the nanoparticles were determined by TGA. Figure 3D and Figure 3E Exposed CNP and Mn are shown respectively. x Zn 1-x TGA plots of Fe2O4 / oleic acid / BADGE, BADGE, OA, and mixtures of OA+BADGE. In both coated and uncoated samples, slight weight loss temperatures below 150°C may be related to moisture content. Figure 3D Oleic acid showed complete weight loss at 400°C, while the mixture of BADGE and OA+BADGE retained a certain percentage of residue. Figure 3E Functionalized CNPs exhibit two main weight loss phases between 150 °C and 500 °C, and one additional weight loss phase at higher temperatures (>500 °C). The first weight loss is related to the removal of physically absorbed OA and BADGE molecules from the CNP surface. A second weight loss occurs at 460 °C due to the strong binding forces between CNPs, OA, and BADGE. A third weight loss occurs at approximately 750 °C, likely due to the complete decomposition of the surfactant. For Mn... 0.5 Mn 0.6 and Mn 0.7 The total OA+BADGE coatings on CNP were 23%, 21%, and 16% (initial wt.% at room temperature - final wt.% at 800℃).

[0217] Example 3H: Results - Colloidal stability of surface-modified CNP

[0218] The colloidal stability of CNPs was analyzed using DLS. Generally, the balance between attractive forces (magnetic dipole-dipole and van der Waals forces) and repulsive forces (electrostatic and steric) contributes to the stability of nanoparticles. Therefore, bare CNPs are less stable due to the low electrostatic repulsion between them. Figure 5 The colloidal stability of functionalized CNPs was determined by monitoring hydrodynamic dimensions. Figure 3FAn optimal size of 200-400 nm and a count rate between approximately 300 and approximately 500 kcps were observed, confirming the stability of CNP in ethanol.

[0219] Example 3I: Results - Transmission electron microscopy confirms surface-functionalized Mn 0.7 The particle size is 9 to 25 nm.

[0220] Exposed and coated Mn were studied using TEM. 0.7 Particle size and morphology. Figures 7A to 7D TEM micrographs and corresponding particle size distribution histograms of bare and coated CNPs are presented. The TEM images show some aggregation of the equiaxed particles. The bare particles range in size from 8 to 60 nm, with an average particle size of 26 nm. The observed aggregation is due to magnetic interactions between particles and the absence of a surfactant layer. The coated particles range in size from 9 to 25 nm, with an average particle size of 16 nm, which is quite close to the value obtained from the XRD data (13.5 nm).

[0221] Example 3J: Results - By controlling the heating temperature of CNP's AMF using the Mn / Zn ratio, the epoxy resin virgin was heated within 5 minutes. Heat to 160 ℃

[0222] CNPs are used as an “AMF-to-heat” converter to initiate thermosetting adhesives. An induction coil generates a magnetic field that interacts with the nanoparticles. To test heating efficiency, different concentrations (5-30 wt.%) of functionalized CNPs are dispersed in a BADGE using ultrasound, and the solution is then placed in an induction coil (solenoid coil) with a frequency of 400 kHz and a magnetic field strength of 50 Oe to 140 Oe. Heating efficiency depends heavily on the strength of the alternating electromagnetic (AC) magnetic field, the Curie temperature (Tc) of the nanoparticles, and their concentration in the BADGE. By controlling the applied magnetic field strength, the temperature required for thermosetting activation can be reached within 4-5 minutes. The temperature rises for approximately 300 seconds until a plateau is reached. When the magnetic nanoparticles suspended in the adhesive are affected by the alternating electromagnetic field, the loss due to magnetization reversal causes electromagnetic energy to be converted into heat. The plateau temperature in AMF is the temperature at which electromagnetic energy is completely converted into heat under a specific application magnetic field / frequency. The reached plateau temperature varies depending on the strength of the alternating electromagnetic field and the CNP concentration in the adhesive. Figures 8A to 8D The graphs depicting temperature versus time for Mn / Zn ratio, CNP loading percentage, and electric field strength obtained from AMF heating are presented. 0.7 Zn 0.3 The highest temperature of Fe2O4 / OA / BADGE (T) max (Higher than Mn) 0.5 Zn 0.5 Fe2O4 / OA / BADGE and Mn 0.6 Zn 0.4 The highest temperature (T) of Fe2O4 / OA / BADGE under each fixed load.max In all three cases, the high CNP loading in the BADGE results in a higher maximum temperature, but importantly, the maximum temperature can only be reached by the Tc of the particles. Among these, Mn... 0.7 The nanoparticles exhibited the highest Tc (237℃) and saturation magnetization (M). s (60 emu / g). Mn 0.5 and Mn 0.6 The maximum temperatures of the particles are 90℃ and 105℃, respectively. The temperature can also be controlled by adjusting the AC magnetic field, frequency, and time. The frequency of the AMF system is fixed, but the field strength can vary between 0 and 140 Oe. Figure 8D Describing Mn 0.7 Zn 0.3 Fe₂O₄ / OA / BADGE (15 wt.%) nanoparticles were heated in AMF at field strengths of 50-140 Oe. Temperatures of 48 °C, 90 °C, 118 °C, and 134 °C were reached within 10 minutes, corresponding to AC magnetic fields of 50 Oe, 80 Oe, 100 Oe, and 140 Oe, respectively. At higher field strengths, the steady-state was reached in a shorter time due to faster heat dissipation. For Mn in BADGE... 0.7 Particles with loadings of 20 wt.% and 30 wt.% were observed to reach maximum temperatures of 140 °C and 160 °C respectively under an AC field strength of 140 Oe. Similarly, different concentrations (1–20 wt.%) of Mn in GDE were investigated. 0.8 Zn 0.2 Fe2O4 / OA / BADGE and Mn 0.9 Zn 0.1 AMF heating and magnetic field strength of Fe2O4 / OA / BADGE nanoparticles. 20wt.%Mn 0.9 Zn 0.1 Fe2O4 / OA / BADGE reached a maximum temperature of 289℃. Figure 9B To prevent scorching / hot spot formation during adhesive curing, temperature and curing time are crucial for each formulation. Here, the AC magnetic field and time can be selected to achieve a specific temperature or to predict the temperature under a specific magnetic field.

[0223] Example 3K: Results - Mn 0.7 Zn 0.3 Fe2O4 / OA / BADGE achieved its highest specific absorbance (SAR) of 5 Wg at 140 Oe. -1

[0224] The heating efficiency of magnetic nanoparticles under an AC magnetic field is defined by specific absorptivity (SAR) or specific power loss (SLP), expressed in Wg. -1 SAR is defined as the heat generated per gram of magnetic material per unit time, calculated using the following formula:

[0225] SAR=C 溶剂.m 溶剂 (dT / dt) / m CNP

[0226] Where C 溶剂 Here, m is the specific heat capacity of BADGE (346 J / mol K), and m is the total mass of the solvent. CNP Let be the mass of the Curie nanoparticle, and dT / dt be the temperature rise per unit time, i.e., the initial slope of the temperature versus time curve. The average SAR value of the surface-modified CNPs with different loadings is calculated by considering the linear fitting slope. Figure 10A The graph shows the relationship between CNP mass and temperature increase per unit time. SAR increases linearly with magnetic field amplitude for Mn. 0.7 Zn 0.3 The average loading of Fe2O4 / OA / BADGE (5-30 wt.%) showed the highest SAR (5 Wg) observed at 400 kHz frequency and 140 Oe amplitude. -1 This is due to the M of these CNPs. s High. Compared to the reported formulation, Mn 0.8 Zn 0.2 The SAR of Fe2O4 at 100 kHz frequency and 72 Oe amplitude is as low as 0.13 Wg. -1 Mn 0.62 Zn 0.41 Fe 1.97 O4 also reported high SAR (57 Wg) at a high frequency of 970 kHz and a field amplitude of 80 Oe. -1 (Mn+Fe). SAR values ​​of 7.5 to 10 Wg for Mn-Zn ferrites were also reported at different frequencies and magnetic field strengths of 520 kHz and 166 Oe. -1 The conclusion is that SAR depends on several parameters, such as the sample preparation method, the structure and magnetism of the nanoparticles, the amplitude and frequency of the applied magnetic field, and the shape and size of the nanoparticles.

[0227] Example 3L: Results - Curing Commercial Epoxy Adhesives with Magnetization Additives

[0228] The magnetic curing of epoxy adhesives was investigated by adding CNPs (15, 20, and 30 wt.%) to Permabond ES558, TIM 813-HTC, or BADGE-DICY composites to bond different adhesive materials (PMMA, ABS, glass, and wood). Mn with an average size of 14 nm was also studied. 0.7 Zn 0.3Fe2O4 / OA / BADGE particles provided ideal results due to their wider temperature range. The functionalized CNPs were incorporated into the adhesive material via simple manual mixing in a liquid thermosetting resin. Oven curing cycles were as follows: Permabond ES558: 130°C for 75 minutes, 150°C for 60 minutes, or 170°C for 40 minutes; TIM 813HTC: 100°C for 1 hour + 150°C for 1 hour (recommended) or 150°C for 30 minutes (alternative). For comparison, magnetocuring experiments were conducted for 1 hour at a frequency of 400 kHz and a magnetic field strength of 140 Oe. A control experiment with heat (oven) curing was conducted at 160°C for 1 hour at a heating rate of 10°C / min.

[0229] Apply pure adhesives (ES558, TIM 813HTC, and BADGE-DICY) between ABS specimens (see [link]). Figure 11A This was evaluated as a negative control. No heat was generated within the AMF coil due to the absence of magnetic additives. Next, an epoxy / CNP magnetic curing additive sample was placed inside the induction coil, and a rapid temperature rise was observed. Heat dissipation occurred when CNP was exposed to AMF due to Neel-Brown relaxation losses.

[0230] Example 3M: Results - Stable lap shear bond strength under 20-30% load

[0231] After exposure to AMF, the samples were cooled to room temperature and evaluated in lap shear mode on a tensile testing machine equipped with a 500N force sensor. Figure 11B Example curves for the following formulation are shown: 20 wt.% CNP + ES558 resin on ABS surfaces / materials. Figure 11C As shown, the loading percentage affects the final temperature, epoxy resin crosslinking kinetics, and ultimately the lap shear bond strength. ES558 thermosetting materials with 15 wt.% magnetocuring additive exhibit an lap shear strength of 0.83 MPa, but exceed 2 MPa at additive concentrations of 20 wt.% and above. Figure 11C As shown. Thermosetting materials TIM 813HTC and BADGE-DICY (100:12) also bonded the ABS samples to varying degrees. Figure 11D ).

[0232] Evaluation formulations for common industrial natural, plastic and glass surfaces (loading 30 wt.% CNP into ES558) Figure 11EThe wood exhibited the highest lap shear strength (6.7 MPa), followed by glass (3.5 MPa) and plastic (<3 MPa), which was roughly correlated with surface roughness and porosity. This does not necessarily represent the maximum adhesive strength, as both plastic and wood samples exhibit failure modes. Glass showed interfacial debonding at the resin / surface interface. Oven curing of ES558, TIM813HTC, and BADGE-DICY samples showed the same order of magnitude adhesion strength compared to the magnetically cured samples. Figure 11F As shown.

[0233] Example 3N: Results - Curie nanoparticles provide precise temperature control without charring.

[0234] The surface temperature of the sample and the temperature of the thermosetting resin were evaluated under in-situ heating provided by the AMF / CNP additive. The surface temperature was evaluated in real time using fiber optic thermocouples, while the internal temperature of the thermosetting resin was evaluated using both fiber optic thermocouples and an infrared camera. Figure 12A The surface temperatures of four different surfaces / materials during ES558 magnetic curing with a CNP loading of 20 wt.% were depicted. For samples 1–3 mm thick, the surface temperature did not exceed 60–65 °C, although... Figure 12B The internal resin temperature was observed to be 140°C. No overheating was observed. Images taken by an FL-IR camera during the AMF curing process of ES558 at a 20 wt.% load also confirmed the localized heating of the thermosetting resin under AMF.

[0235] Further analysis of resin curing was performed using TGA and DSC. If incomplete curing of the resin was observed, DSC would show a peak at the activation temperature. Figure 12C The DSC spectra of uncured ES558 resin (positive control) and magnetocured CNP composite are shown. A single peak at the thermosetting activation temperature was observed in the positive control at 150 °C, but not in the magnetocured composite. Overlapping TGA curves of the thermocured and magnetocured samples yielded similar thermal degradation curves, indicating that the magnetocured sample did not undergo charring. Delayed peaks after 500 °C were observed in both the net binder and the cured binder, which are attributed to oxidation, pyrolysis, or a combination thereof.

[0236] Example 3O: Results - Infrared spectroscopy shows epoxy ring-opening and rigid matrix

[0237] The degree of crosslinking in ES558 was qualitatively determined using infrared (IR) spectroscopy. Figure 12D The uncured resin and the magnetically cured CNP composite were compared. The bending vibration of CH in the methylene group (2923 cm⁻¹) was also observed. -1 ) and the stretching vibrations of C=C in aromatic rings (1602 and 1508 cm) -1 The decrease in all values ​​confirms that this is a rigid cross-linked resin. (915, 812, and 752 cm⁻¹) -1The disappearance of the peak at that point indicates that the epoxy ring opens to form ether crosslinks.

[0238] Example 4: Discussion of Results

[0239] As illustrated in the embodiments of this disclosure, a platform magnetopolymerization technology is described herein that cures thermosetting resins by exposing a non-metallic surface to an alternating electromagnetic field. Industry-relevant structure-property relationships demonstrate the platform's flexibility in in-situ thermodynamics, particle loading, field strength, and commercial resins. Advanced features of CNP-based magnetopolymerization technology include protection against overheating and colloidal stability in polar organic environments. Conventional magnetopolymerized adhesives have observed resin charring due to runaway heating caused by particle size-dependent thermodynamics and the aggregation of metal oxide particles in the organic resin. However, advantageously, the CNP of this disclosure overcomes these obstacles by self-regulating magnetic absorption when particles approach the Curie temperature, i.e., without the need for feedback electronics. The temperature limit of the CNP of this disclosure provides an advantage over other inductively magnetic nanoparticles. This is one of the fundamental principles for using this CNP in the magnetic induction heating and activation of thermosetting epoxy adhesives. The aggregation of high surface energy Curie nanoparticles, protected by a functional shell of a resin-based coating, controls chemical reactivity and dispersibility in solution for easy dispersion. Coating / functionalization is achieved by covalently grafting oleic acid onto CNPs after synthesis. Oleic acid-coated particles are then grafted with epoxy monomers (BADGE), improving thermosetting initiation through the similar-miscible particle solubility in a one-component epoxy adhesive. Fe present on the particle surface... 3+ Ions and hydroxyl groups can interact with the polar groups of oleic acid and BADGE, thereby providing colloidal stability in epoxy resins. FTIR spectroscopy and TGA analysis showed that the particle surface was coated with oleic acid and BADGE. However, the FTIR peak of BADGE observed in the coated particles was very small. This may be due to the interaction between oleic acid and BADGE (…). Figure 3C Long-term colloidal stability of functionalized CNPs in BADGE was observed. The particles settled after 1–2 hours but redispersed well after a few minutes of sonication / vortexing. The functionalized CNPs were evaluated based on AMF heating efficiency, SAR value, and Hf factor. Once the CNPs were subjected to an AC magnetic field, electromagnetic energy was converted into heat due to residual losses in the MnZn ferrite. These residual losses stemmed from various relaxation effects of magnetization in the magnetic field. The residual losses or heat generation of small nanoparticles were due to (i) Brownian relaxation mechanisms, where the magnetic moment is locked onto the crystal axis, thus the entire particle rotates with the magnetic field, and (ii) Niehr relaxation mechanisms, where the magnetic moment rotates within the particle in an external magnetic field. Furthermore, the heating capacity also depends on the properties of the nanomaterial, such as particle size, magnetization, and magnetic anisotropy, as well as the applied magnetic field strength (H) and frequency (f). Due to the influence of Mn...0.7 The high Curie temperature and magnetization of the particles are beneficial to Mn. 0.7 Zn 0.3 The highest heating of CNP can be observed in Fe2O4 / OA / BADGE particles. Besides high M s and T c In addition, Mn 0.7 Nanoparticles exhibit better performance than Mn in magnetic fields used for magnetic induction. 0.4 Mn 0.5 and Mn 0.6 Higher metastable magnetic moments, as shown in the magnetization versus temperature curve ( Figure 13A and 13B The SAR of these functionalized CNPs dispersed in the BADGE is 5 Wg. -1 SAR with Mn x Zn 1-x The variation in the mol% of Mn in Fe2O4 may be due to different related M s Therefore, the interaction between dipole particles changes significantly. Furthermore, the product of frequency and magnetic field amplitude (H×f) can determine whether the magnetic field / frequency is within the safe zone for medical applications. The Brezovich criterion limits the product of frequency and amplitude to 5×10⁻⁶. 8 Am -1 s -1 A safety threshold has been set for exposing alternating electromagnetic fields to the human body. Using high-frequency and high-amplitude AMFs can generate eddy currents in conductive media, leading to nonspecific heating or harm to the human body. Importantly, for medical applications, the Hf factor may not exceed 5 × 10⁻⁶. 9 Am -1 s -1 This is because patients can better tolerate smaller field exposures. The maximum Hf of this system is 4.4 × 10⁻⁶. 9 Am -1 s -1 This indicates that the method used for solidification can be applied to medical translation.

[0240] The AMF heating of CNP allows the one-component epoxy adhesive to crosslink via in-situ heating. Complete curing of the ES558 magnetic adhesive was achieved by applying a magnetic field strength of 140 Oe at a fixed frequency of 400 kHz for 1 hour. We investigated the structure-property relationships of CNP, adhesive composites, and bonding materials with different loadings, controlled by oven curing. Increasing the CNP loading increased the shear strength of ABS by 3 MPa. It is speculated that the addition of CNP improves the stiffness of the adhesive. The observed increase in shear strength is likely due to the interaction between the Curie nanoparticles and the one-component epoxy adhesive. The presence of an epoxy resin (BADGE) coating on the surface of the Curie nanoparticles promotes this interaction. Therefore, this results in greater force transfer between the Curie nanoparticles and the matrix, leading to increased strength. Wood exhibited the strongest adhesion among the different bonding materials, with a shear strength of 6.69 MPa, which may be related to the available porosity of the wood surface. During magnetic curing, the magnetic adhesive readily penetrates the porous structure of the wood, resulting in high lap shear strength. The slight differences in surface temperature among the different bonding materials are due to their varying thicknesses and thermal conductivity. Regardless of the type of adhesive, the highest surface temperature remained below 65°C, indicating that magnetic curing locally heated the bonded portion while preventing charring. These results reveal the potential application value of self-controlled heating in the polymer industry, where temperatures above a certain limit can damage materials. The CNP disclosed herein facilitates the development of various magnetic adhesives using commercially available adhesives that have already been proven to be able to bond a range of materials under AMF (Amphimetric and Flame-Factor) conditions, materials that have traditionally been bonded almost entirely using conventional oven methods. The CNP disclosed herein provides a curing method involving remote control via rapid and localized heating, while reducing costs and energy consumption, making it highly suitable for a wide range of industries.

[0241] The oleic acid and epoxy-functionalized CNPs described herein can be used for the magnetocuring of one-component epoxy adhesives, but depending on the application requirements, the CNPs of this invention can also be further functionalized or modified with various functional materials. AMF heating results of this disclosure show that a magnetic field (140 Oe) and a frequency (400 kHz) can heat the CNPs below the Curie temperature. Increasing the magnetic field strength may lead to an increase in the AMF that can be heated to the Curie temperature control point.

[0242] Example 5A: Further Example - Magnetically Curing Additives for Bioadhesives, CaproGlu

[0243] In a further example, we investigated CaproGlu with a 10 wt.% Mn-loaded CNP additive. 0.7 Zn 0.3 Fe2O4 / OA / PCL and 50wt.%Mn 0.7 Zn 0.3Magnetization of Fe2O4 / OA / PCL. CNP was incorporated into CaproGlu by simple manual mixing, and the matrix was filled into glass vials (1.5 mL) and animal bone (3 mm in diameter). Magnetization experiments were conducted for 30 minutes at a magnetic field strength of 140 Oe and a frequency of 400 kHz. Figure 14A CaproGlu and 10 wt.% Mn were shown in a glass bottle. 0.7 Zn 0.3 Temperature profiles of Fe2O4 / OA / PCL curing. After exposure to AMF, the samples were cooled to room temperature, and the storage / loss modulus of the cured samples was measured using a rheometer under a force of 5 N. Figure 14B The adhesion strength of bone samples was evaluated in lap shear mode on a tensile testing machine with a 100N force sensor. Figure 14C This indicates Mn with a loading of 50 wt.%. 0.7 Zn 0.3 The adhesion strength at 77 kPa of the magneto-cured bone sample of Fe2O4 / OA / BADGE.

[0244] Example 5B: Further Example - Controlling the AMF Heating Temperature of CNPs via Carbon Nanotubes (CNTs)

[0245] Adding 2 wt.% CNTs and mixing with dispersed CNPs caused AMF to shrink upon heating at 50°C. To test the heating efficiency, 5 wt.% Mn was ultrasonically treated. 0.9 Zn 0.1 Fe2O4 / OA / BADGE CNPs were dispersed in glycerol diglycidyl ether (GDE), then physically incorporated with 0.5 wt.% to 2 wt.% CNTs (COOH functionalized), and sonicated again to achieve good dispersion. The solution was then placed in an induction coil with a frequency of 400 kHz and a magnetic field strength ranging from 140 Oe to 60 Oe. Figures 15A to 15D A graph depicting the temperature versus magnetic field strength obtained from AMF heating for the CNT loading percentage is presented. 0.9 Zn 0.1 The highest temperatures achieved by Fe₂O₄ / OA / BADGE nanoparticles with and without 0.5, 1, and 2 wt.% CNTs were 200, 179, 165, and 150 °C, respectively. The heating of AMF was regulated by the incorporation of CNTs, and it was demonstrated that the temperature increased until a plateau was reached in approximately 1000 seconds. This plateau temperature varied depending on the AC magnetic field strength and the carbon nanotube concentration in the composite. Notably, CNTs in 5 wt.% Mn... 0.9 Zn 0.1 The increased loading of Fe2O4 / OA / BADGE and GDE mixtures resulted in a decrease in the maximum temperature at each magnetic field strength.

[0246] Example 5C: Further Example - Controlling the AMF Heating Temperature of CNPs via Carbon Nanotube Coils (CNC)

[0247] Carbon nanotube coils and CNC (1.5 wt.%) increased the heating temperature of AMF in CNP by 10 °C. The effect of CNC on 5 wt.% Mn in GDE was evaluated. 0.9 Zn 0.1 The effect of heating on AMF in Fe2O4 / OA / BADGE. This was achieved by first adding 5 wt.% Mn... 0.9 Zn 0.1 Fe2O4 / OA / BADGE particles were dispersed in glycerol diglycidyl ether (GDE) and then physically added to the matrix using CNC to prepare the samples. All samples were sonicated for 1 hour prior to the experiment. Figure 16 The relationship between temperature obtained by AMF heating and CNC load at a frequency of 400 kHz and a magnetic field strength of 140 Oe is shown. The addition of 1–1.5 wt.% CNC results in an increase of approximately 10 °C in AMF heating of the CNP, while higher CNC loads (2, 3, and 4 wt.%) are observed to shield the magnetic heating of the CNP. Shielding the heating of the CNP under a magnetic field with 4 wt.% CNC reduces AMF heating by approximately °C.

[0248] Example 5D: Further Example - Bare CNTs and CNC Machines without Heating at 140 Oe AMF

[0249] 1 wt.% COOH-functionalized carbon nanotubes (CNTs) and carbon nanocoils (CNCs) were dispersed in glycerol diglycidyl ether (GDE) and ethanol. Figure 17A and Figure 17B All samples were sonicated for 1 hour and vortexed for 1–2 minutes, then held at 140 Oe AMF. All control groups, 1 wt.% CNC, and samples in GDE ( Figure 17A ) and ethanol ( Figure 17B The CNTs in the image did not show any heating under an alternating electromagnetic field.

[0250] Example 6A: Further Example - Extending Storage Life Without Using a Hardener

[0251] Examples 6A to 6C demonstrate that the BADGE-based magnetic adhesive, without a hardener, can extend the shelf life of the adhesive. The BADGE-based, hardener-free magnetic adhesive of the present invention extends the shelf life of the adhesive. The magnetic curing additive CNP has been directly incorporated into the resin and cured under AMF on ABS samples (100% filled). Conventionally, in the presence of a hardener in the adhesive, resin / adhesive activation may occur over a period of time (approximately 4-6 months), which adversely shortens the shelf life of the composite adhesive. However, this method provides a more stable magnetic adhesive formulation because it avoids the use of a hardener. The BADGE-based magnetic adhesive of the present invention may include the following steps.

[0252] CNP and BADGE are added at a ratio between 5 and 30 wt.%. ABS samples are bonded within 10 minutes without charring. Advantageously, the resulting bond strength exceeds that of ABS samples loaded with 30 wt.% CNP (5.2 MPa). The following examples describe the BADGE-based magnetic adhesive of the present invention in more detail.

[0253] Example 6B: Further Example - Magnetic Adhesive Bonding ABS Without Hardener, No Coking

[0254] To develop a hardener-free magnetic adhesive, 5-30 wt.% of CNP was directly mixed with a hardener-free epoxy resin (bisphenol A diglycidyl ether, BADGE). The magnetic adhesive (CNP + BADGE) was applied to a 1 cm layer. 2 An ABS sample with a sandwich structure was prepared on the surface area of ​​the sample. A fiber optic sensor was placed on the surface of the ABS sample to monitor the surface temperature. Figure 18A and Figure 18B Prior to magnetic curing, the thermal stability and activation temperature of BADGE were monitored using TGA-DSC. Figure 18C and Figure 18D For epoxy resin (without hardener), no sharp activation temperature transition below 300°C was observed in the DSC curves. However, for the epoxy adhesive containing hardener (Permabond ES558), a sharp activation peak was observed at 150°C. Subsequently, ABS samples were bonded under AMF and the surface temperature during the magnetic curing process was recorded. Figure 18B A hardener-free magnetic adhesive containing 10-30 wt.% CNP in epoxy resin (BADGE) was applied to ABS specimens, and curing was observed within 600 seconds of exposure to AMF, while the surface temperature of the 30 wt.% CNP was limited to approximately 100°C. Figure 18B ).

[0255] Example 6C: Further Example - BADGE-based magnetic adhesive cured with magnetic curing additives, without hardening Agent

[0256] Pressure was applied to the above BADGE / CNP samples until failure to determine the failure mechanism and final bond strength. Overlap shear testing was performed using 3D-printed ABS specimens, requiring no surface cleaning, and a 2.5 kN force sensor. The adhesive strength of pure BADGE+CNP is shown below. Figure 19 In the absence of a hardener, CNP was loaded into epoxy resin (BADGE) at a ratio of three wt.% for evaluation. Figure 19The bond strength was correlated with CNP load, ranging from 1.9 MPa (10 wt.% CNP) to 3.1 MPa (20 wt.% CNP) to 5.2 MPa (30 wt.% CNP). Material failure was observed in the 30 wt.% CNP + BADGE sample, while other samples showed cohesive or bond failure. As a control, the tensile strength of the ABS specimens was similar to that of the 30 wt.% CNP sample at approximately 5.2 MPa. Figure 19 ).

[0257] Example 7: Summary, Business Applications, and Potential Applications

[0258] This disclosure relates to a one-pot composite material with colloidal stability, which is endowed with non-contact “magnetic curing” by exposure to an alternating electromagnetic field.

[0259] The present invention may include a composite comprising a thermosetting polymer, magnetic nanoparticles having a Curie temperature dispersed in the thermosetting polymer, wherein the magnetic nanoparticles have a surfactant layer chemically bonded to the magnetic nanoparticles, and a monomer layer grafted onto the surfactant layer.

[0260] The thermosetting polymer can be selected from bisphenol A diglycidyl ether (BADGE), Permabond ES558, TIM-813HTC, BADGE-dicyandiamide, and mixtures thereof. The thermosetting polymer can be cured when placed in an alternating electromagnetic field. The alternating electromagnetic field can have a field strength of 50-140 Oe and / or a frequency of 100 kHz to 1 MHz. The thermosetting polymer can be placed in the alternating electromagnetic field for 5 to 60 minutes.

[0261] The composition of magnetic nanoparticles can be represented by the formula Mn x Zn 1-x Fe2O4, Ni x Zn 1-x Fe2O4 and / or Co x Zn 1-x Fe2O4, wherein 0.4 ≤ × ≤ 0.9. The surfactant layer may include a fatty acid (e.g., oleic acid) having 15 to 20 carbons. The monomer layer may include epoxy-based molecules (e.g., bisphenol A diglycidyl ether, glycerol diglycidyl ether) and / or polycaprolactone-based molecules.

[0262] The composite material may also include carbon allotropes (such as carbon nanotubes (CNTs) and / or carbon nanotube coils (CNCs)).

[0263] In this disclosure, a series of Curie nanoparticles, such as those with Mn, were developed. x Zn 1-xThe composition of Fe2O4 has a Curie temperature range of 80-239℃. Oleic acid / BADGE-functionalized CNP disperses well in BADGE and provides long-term colloidal stability in epoxy resins and one-component epoxy adhesives. Adding 20-30 wt.% Mn... 0.7 Zn 0.3 Fe2O4 / OA / BADGE loaded into ES558 is suitable for magnetocuring of a non-coking, one-component epoxy adhesive. Mechanical testing results show that the lap shear strength of the wood sample reaches up to 6.69 MPa. This one-component magnetocuring adhesive allows for the development or modification of existing formulations, incorporating CNP as a filler / modifier. This composite material can be used in a variety of applications, such as sports, automotive, and aerospace.

[0264] This disclosure relates to a modifier method incorporating the CNP of the present invention. This method allows the incorporation of CNPs into readily available thermosetting adhesive formulations, such as laboratory-synthesized BADGE-DICY and the bio-adhesive CaproGlu. The magnetocuring of the present invention provides a more cost-effective activation method because the adhesive is directly heated without heat conduction through the surface / material to which it is coated. In this document, the curing of various adhesive materials on wood, ceramics, plastics, and animal bones is demonstrated by AMF activation, or “magnetocuring,” which has significant implications for the medical, sporting, automotive, and aerospace industries. The advancements in adhesive technology brought about by the present invention can drive economic development across a wide range of fields.

[0265] While this disclosure has been specifically shown and described with reference to particular embodiments, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope defined herein. Therefore, the scope of this disclosure is indicated by the appended claims and all modifications thereof within the meaning and scope of their equivalents.

Claims

1. An adhesive additive for magnetocurable adhesives, the adhesive additive comprising: Magnetic nanoparticles, wherein the magnetic nanoparticles comprise: (i) a plurality of metals, said plurality of metals including iron, manganese, cobalt, nickel and / or zinc, or (ii) A metal oxide containing a variety of metals, including iron, manganese, cobalt, nickel and / or zinc; A coating layer on the magnetic nanoparticles, the coating layer comprising: (a) Organic surfactants, and (b) A monomer or polymer miscible with the adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate. The magnetic nanoparticles generate heat in response to an alternating electromagnetic field applied thereto, causing the adhesive substrate to crosslink; and Due to the interaction between the monomer or polymer and the adhesive substrate, the attractive force between the coated magnetic nanoparticles and the adhesive substrate is greater than the attractive force between the coated magnetic nanoparticles themselves.

2. The adhesive additive according to claim 1, wherein the molecular formula of the magnetic nanoparticles is A. x Zn 1-x Fe2O4, where A is cobalt, manganese or nickel, and x ranges from 0.4 to 0.

99.

3. The adhesive additive according to claim 1 or 2, wherein the organic surfactant is formed as an organic coating layer, wherein the organic coating layer comprises a fatty acid having 15 to 20 carbon atoms.

4. The adhesive additive according to claim 1 or 2, wherein the organic surfactant comprises oleic acid.

5. The adhesive additive according to claim 1 or 2, wherein the organic surfactant is covalently bonded to the magnetic nanoparticles.

6. The adhesive additive according to claim 1 or 2, wherein the organic surfactant is formed between and in contact with: (i) the magnetic nanoparticles and the monomer, or (ii) the magnetic nanoparticles and the polymer.

7. The adhesive additive according to claim 1, wherein the monomer comprises epoxy.

8. The adhesive additive according to claim 1, wherein the monomer comprises bisphenol A diglycidyl ether and / or glycerol diglycidyl ether.

9. The adhesive additive according to claim 7 or 8, wherein the monomer further comprises a hardener, wherein the hardener comprises dicyandiamide.

10. The adhesive additive according to claim 1 or 2, wherein the polymer comprises polycaprolactone.

11. The adhesive additive according to claim 1 or 2, further comprising a carbon allotrope.

12. The adhesive additive according to claim 1 or 2, wherein the alternating electromagnetic field comprises a frequency of 100 kHz to 1 MHz and / or a magnetic field strength of 50 Oe to 140 Oe.

13. A magnetocurable adhesive, said adhesive comprising: The adhesive additive according to any one of claims 1 to 12, and Adhesive substrate.

14. The adhesive of claim 13, wherein the adhesive substrate is: (i) A resin comprising a thermosetting material, activated by thermal energy generated from magnetic nanoparticles in an adhesive additive as described in any one of claims 1 to 12 to form a crosslink, wherein the thermosetting material comprises an epoxy resin and bisacrylidine; or (ii) A resin comprising a thermoplastic material, wherein the thermoplastic material comprises polycaprolactone.

15. The adhesive according to claim 13 or 14, wherein the adhesive substrate is a resin without a hardener.

16. The adhesive according to claim 13 or 14, wherein the adhesive additive and the adhesive substrate are present in a weight ratio of 1:100 to 50:

100.

17. A method for forming the adhesive additive as claimed in claim 1, the method comprising: Magnetic nanoparticles are provided, the magnetic nanoparticles comprising: (i) a plurality of metals, said plurality of metals including iron, manganese, cobalt, nickel and / or zinc, or (ii) A metal oxide containing a variety of metals, including iron, manganese, cobalt, nickel and / or zinc; An aqueous solution comprising the magnetic nanoparticles is mixed with an organic surfactant; and An organic solution comprising magnetic nanoparticles coated with the organic surfactant is mixed with (i) a monomer or (ii) a polymer miscible with an adhesive substrate, wherein the adhesive additive may be incorporated into the adhesive substrate.

18. The method of claim 17, wherein providing the magnetic nanoparticles comprises: An alkaline solution is mixed with two precursor solutions to form an alkaline mixture, wherein the alkaline solution contains a first metal precursor, and each of the two precursor solutions contains a second metal precursor and a third metal precursor, wherein the first metal precursor, the second metal precursor and the third metal precursor form different metals in the magnetic nanoparticles; and The alkaline mixture is subjected to hydrothermal treatment to form the magnetic nanoparticles.

19. The method of claim 17 or 18, wherein mixing the aqueous solution comprising the magnetic nanoparticles with the organic surfactant comprises: The magnetic nanoparticles were dispersed in an aqueous medium, and The aqueous medium is mixed with the organic surfactant.

20. The method according to claim 17 or 18, wherein the organic surfactant comprises a fatty acid having 15 to 20 carbon atoms.

21. The method according to claim 17 or 18, wherein mixing the organic solution comprising magnetic nanoparticles coated with the organic surfactant with (i) a monomer or (ii) a polymer comprises: Magnetic nanoparticles coated with the organic surfactant are dispersed in an organic medium; The monomer or polymer is dissolved in an organic solvent to form a monomer solution or a polymer solution, respectively; and The monomer solution or polymer solution is mixed with the organic medium containing magnetic nanoparticles coated with the organic surfactant.

22. The method according to claim 17 or 18, further comprising: The adhesive additive added to another resin; and The carbon allotrope is mixed with the other resin containing the adhesive additive.

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