A super-elastic glue and a preparation method thereof

Abstract

The application discloses a super-elastic glue and a preparation method thereof. The preparation method comprises the following steps: providing a precursor liquid containing monomers, an initiator and a crosslinking agent, and a substrate; transferring the precursor liquid to the substrate, and then placing the substrate in an environment with a preset oxygen concentration; and irradiating the precursor liquid on the substrate with ultraviolet light for a preset time to perform a polymerization reaction, so that the super-elastic glue with viscosity on the upper layer and elasticity on the lower layer is obtained. The preparation method of the super-elastic glue with low hysteresis and strong adhesion is realized by using one-step air-blocking polymerization, so that the super-elastic glue with thin thickness and low bending stiffness can be synthesized, and the super-elastic glue has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of superelastic adhesive technology, and in particular to a superelastic adhesive and its preparation method. Background Technology

[0002] Currently, the development of adhesives that simultaneously possess both viscosity and elasticity inevitably encounters an inherent contradiction in adhesives: the contradiction between hyperelasticity and adhesion. Specifically, for a homogeneous network, forming a polymer with low hysteresis and strong adhesion is inherently contradictory. A polymer network with low hysteresis and good resilience requires a high crosslinking density, short chains between crosslinking points, minimal entanglement, and a polymer network where entropic elasticity dominates and dissipation is minimal during loading and unloading. Conversely, a polymer network with strong adhesion requires a low or no crosslinking density, long-chain polymers, abundant entanglement, greater dissipation during loading and unloading, and high hysteresis. Therefore, the only way to resolve this contradiction is through the design of polymers with heterogeneous structures. As described in CN114836138 A, the inventors decoupled the superelastic matrix and the adhesive surface, combining a layer of superelastic, low-hysteresis material with a second layer of strongly adhesive surface using a two-step method. By changing the thickness ratio of the superelastic material to the strongly adhesive surface, they prepared a superelastic adhesive with a heterogeneous network structure, possessing both strong adhesion and low hysteresis. They achieved the preparation of a 1.1 mm thick superelastic adhesive with a hysteresis of 4%, lower than the 7% of the recognized superelastic material PDMS Sylgard184 (10:1), and a peel bond energy of 270 J·m⁻¹ with a polyethylene terephthalate (PET) substrate. -2 It is superior to the commonly used 3M stretchable, transparent pressure-sensitive adhesive VHB 4905. However, the preparation process of this superelastic adhesive is a two-step process, which is not only complex in terms of material selection and manufacturing, but also makes it difficult to reduce the thickness of the material, making it impossible to achieve conformal bending stiffness with the substrate and a good bonding effect with the substrate.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a superelastic adhesive and its preparation method, which aims to solve the problem that the existing methods for preparing superelastic adhesives use a two-step process and are complicated.

[0005] The technical solution of the present invention is as follows:

[0006] A first aspect of the present invention provides a method for preparing a superelastic adhesive, comprising the steps of:

[0007] Provides precursor solutions and substrates containing monomers, initiators, and crosslinking agents;

[0008] The precursor liquid is transferred to the substrate and then placed in an environment with a preset oxygen concentration. The precursor liquid on the substrate is irradiated with ultraviolet light for a preset time to carry out a polymerization reaction, resulting in a superelastic adhesive with a viscous upper layer and an elastic lower layer.

[0009] Optionally, the mass ratio of the monomer, initiator and crosslinking agent is (80-100):(1-15):(1-10).

[0010] Optionally, the monomer includes at least one of a monofunctional reactive diluent, a polyfunctional reactive diluent, and an oligomer.

[0011] Optionally, the monofunctional reactive diluent includes at least one of acrylic acid, alkyl acrylate, methacrylate, methacrylate with cycloalkane or benzene ring, and vinyl reactive diluent.

[0012] Optionally, the multifunctional active diluent includes at least one of ethylene glycol diacrylates, propylene glycol diacrylates, alkoxylated acrylates, dioxopentanoates, alkoxylated bisphenol A diacrylates, and vinyl ethers.

[0013] Optionally, the oligomer includes at least one of unsaturated polyester, epoxy acrylate, polyurethane acrylate, polyester acrylate, and organosilicon oligomer.

[0014] Optionally, the initiator includes a type I cleavage photoinitiator, which includes at least one of benzoyl photoinitiators, benzoyl ketal photoinitiators, α-hydroxy ketal photoinitiators, and acylphosphine oxide photoinitiators.

[0015] Optionally, the crosslinking agent includes a multifunctional active diluent.

[0016] Optionally, the multifunctional active diluent includes at least one of diethylene glycol diacrylate, polyethylene glycol (diol) diacrylate, propoxylated neopentyl glycol diacrylate, and 1,6-hexanediol diacrylate.

[0017] In a second aspect, the present invention provides a superelastic adhesive, wherein it is prepared by the preparation method of the present invention as described above.

[0018] Beneficial Effects: This invention transfers a precursor liquid containing monomers, initiators, and crosslinking agents onto a substrate, and then places it in an environment with a preset oxygen concentration. Oxygen diffuses from the surface of the precursor liquid on the substrate into the interior of the precursor liquid body. The area that oxygen can diffuse to is the upper layer, and the area that oxygen cannot diffuse to is the lower layer. In the upper layer where oxygen can diffuse, the reactive free radicals at each stage react more easily with oxygen to form more stable peroxides, which inhibits chain growth in the monomer polymerization process and almost prevents chain crosslinking, forming short polymer chains or uncrosslinked suspended chains. The properties of these chains are closer to those of viscous liquids, exhibiting interfacial wettability with the substrate. At the same time, these chains form topological entanglements or physical crosslinks, increasing viscous dissipation, thereby forming a network adhesive layer composed of defects in short polymer chains or uncrosslinked suspended chains (i.e., a network adhesive layer with more defects and lower crosslinking density), thus forming a viscous upper layer. In the lower layer where oxygen cannot diffuse, free radical polymerization proceeds normally, including chain initiation, chain growth, chain crosslinking, and chain termination reactions, forming an elastic lower layer. Therefore, this invention can prepare a thin-film superelastic adhesive with low hysteresis and strong adhesion using a one-step gas-barrier polymerization method. The preparation method provided by this invention is simple, and the resulting superelastic adhesive exhibits low hysteresis, strong adhesion, and thin film thickness, thus possessing broad application prospects. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the preparation of the superelastic adhesive in an embodiment of the present invention.

[0020] Figure 2 This diagram illustrates the polymerization inhibition process caused by normal free radical polymerization and the introduction of oxygen at each stage of polymerization in embodiments of the present invention.

[0021] Figure 3 This is a graph showing the relationship between the modulus and thickness of the superelastic rubber in this embodiment of the invention and the oxygen diffusion gradient and polymerization time.

[0022] Figure 4 This is a polymer phase diagram under oxygen diffusion.

[0023] Figure 5 (a) is a 3D optical microscope image of the superelastic adhesive prepared in Example 1 of the present invention, and (b) is an enlarged view of the boxed area in (a).

[0024] Figure 6 Images (a)-(c) show the elastic recovery of the superelastic material prepared in Example 2 of this invention after loading and unloading to a strain of 100%, where (a) is the original state, (b) is the state after loading and unloading to a strain of 100%, and (c) is the elastic recovery state after loading and unloading to a strain of 100%.

[0025] Figure 7(a) is a diagram showing the superelastic adhesive prepared in Example 3 of the present invention with the elastic lower layer facing upward during the downward pressing and upward pulling process; (b) is a diagram showing the superelastic adhesive prepared in Example 3 of the present invention with the viscous upper layer facing upward during the downward pressing and upward pulling process.

[0026] Figure 8 The stress-tension ratio curves used for loading and unloading hysteresis tests of the superelastic adhesives in Examples 1-7 of this invention.

[0027] Figure 9 This is a schematic diagram of the downward pressure and upward pull test of the superelastic rubber in Embodiments 1-7 of the present invention.

[0028] Figure 10 This is a schematic diagram of the 90-degree peel test performed on the superelastic adhesive in Examples 1-7 of the present invention.

[0029] Figure 11 This is a schematic diagram of the shear test performed on the superelastic adhesive in Examples 1-7 of the present invention. Detailed Implementation

[0030] This invention provides a superelastic adhesive and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] Most free radical polymerizations do not tolerate the presence of oxygen, as it can have many adverse effects on the network, such as preventing polymerization altogether and resulting in low polymer yield. Therefore, researchers have developed various methods to isolate oxygen, most commonly including nitrogen-based polymer preparation, mold-based oxygen removal polymerization, organic amine-based oxygen removal, and organic sugar-based oxygen removal. However, this invention, contrary to traditional concepts, fully utilizes oxygen for polymerization inhibition. Specifically, this invention provides a method for preparing a superelastic, comprising the following steps:

[0033] S1. Provide a precursor solution and substrate containing monomers, initiators, and crosslinking agents;

[0034] S2, such as Figure 1 As shown, the precursor liquid is transferred to the substrate and then placed in an environment with a preset oxygen concentration. The precursor liquid on the substrate is irradiated with ultraviolet light for a preset time to carry out a polymerization reaction, resulting in a superelastic adhesive with a viscous upper layer and an elastic lower layer.

[0035] In this invention, a precursor liquid containing monomers, initiators, and crosslinking agents is transferred onto the substrate. When placed in an environment with a preset oxygen concentration and simultaneously irradiated with ultraviolet light, the initiator forms free radicals, consuming the oxygen in the precursor liquid (the dissolved oxygen of the precursor liquid itself). At this time, the oxygen above the liquid surface begins to diffuse from top to bottom into the precursor liquid body. In the upper layer where the oxygen diffuses, polymerization is inhibited, while in the lower layer where the oxygen does not diffuse, there is no oxygen, and polymerization is uniform.

[0036] Specifically, in this invention, a certain volume of a precursor liquid containing monomers, initiators, and crosslinking agents is transferred (e.g., transferred and spread evenly) onto the substrate, and then placed in an environment with a preset oxygen concentration. Oxygen diffuses from the surface of the precursor liquid on the substrate into the interior of the precursor liquid body. The area that oxygen can diffuse to is the upper layer, and the area that oxygen cannot diffuse to is the lower layer. Figure 2 As shown (reflecting the polymerization inhibition behavior of normal free radical polymerization and in the presence of oxygen), oxygen diffusion can reach various levels of reactive free radicals in the upper layer (such as initiator free radical R·, monomer free radical RM·, and short-chain polymer free radical RM). x • It reacts more readily with oxygen to form more stable peroxides (RO2·, RMO2·, RM). x O2· inhibits chain growth during monomer polymerization, and chain crosslinking hardly occurs, resulting in short polymer chains (low crosslinking density) or uncrosslinked suspended chains. These chains exhibit properties closer to those of viscous liquids, providing interfacial wettability with the substrate. Simultaneously, these chains form topological entanglements or physical crosslinks, increasing viscous dissipation and ultimately forming a network adhesive layer composed of short polymer chains or uncrosslinked suspended chain defects—the viscous upper layer (i.e., the surface adhesive layer). In the lower layer, where oxygen fails to diffuse, free radical polymerization proceeds normally, including chain initiation, chain growth, chain crosslinking, and chain termination reactions (such as…). Figure 2 From initiator In to R·, RM·, RM x · Then to RM x M y The R process forms a super-elastic lower layer (elastic body layer).

[0037] In the superelastic adhesive provided in the embodiments of the present invention, the upper layer, which mainly exists in the form of short chains or suspended chains, provides an adhesive surface to the lower layer (i.e., the bulk polymer network of the superelastic) where oxygen has not reached.

[0038] For homogeneous networks, low hysteresis and strong adhesion are contradictory. Low-hysteresis, highly resilient polymer networks require high cross-linking density, exhibiting entropic elasticity as the dominant force during loading and unloading with minimal dissipation. Conversely, highly adhesive polymer networks require low or no cross-linking density, resulting in significant dissipation and high hysteresis during loading and unloading. This invention employs a one-step gas-barrier polymerization method to prepare a low-hysteresis, highly adhesive heterogeneous network superelastic, effectively resolving this contradiction. The process is simple and can synthesize thinner superelastics with low flexural stiffness, making it more valuable for practical applications.

[0039] Furthermore, since oxygen diffuses from top to bottom into the forward liquid mass, the oxygen concentration in the upper layer has a gradient, resulting in inconsistent polymerization at different levels. That is, the viscous upper layer exhibits gradient polymerization, which is initially less uniform. Therefore, the modulus and thickness of the viscous upper layer mentioned below are effective average values.

[0040] In step S1, in some embodiments, the substrate includes, but is not limited to, a substrate with grooves, such as circular grooves, square grooves, etc.

[0041] This invention does not limit the specific ratio of monomer, initiator, and crosslinking agent, as these ratios will vary depending on the raw material system and can be set according to actual needs. For example, the mass ratio of monomer, initiator, and crosslinking agent is 80–100:1–15:1–10. Adjusting the monomer, initiator, and crosslinking agent within this ratio can effectively achieve the consumption of a certain concentration of oxygen to form the upper layer of a gradient network structure; the lower layer, unaffected by oxygen, forms a highly crosslinked elastic network that exhibits only entropic elasticity under loading and unloading conditions.

[0042] In some embodiments, the preparation method of the precursor solution containing monomers, initiators, and crosslinking agents includes the following steps:

[0043] The monomer, initiator, and crosslinking agent are mixed to obtain a precursor solution containing the monomer, initiator, and crosslinking agent.

[0044] In some embodiments, the monomer includes, but is not limited to, at least one of monofunctional reactive diluents, polyfunctional reactive diluents, and oligomers.

[0045] In some embodiments, the monofunctional reactive diluent includes, but is not limited to, at least one of acrylic acid, alkyl acrylates, methacrylates, methacrylates containing cycloalkanes or benzene rings (the cycloalkanes are saturated or unsaturated cycloalkanes), and vinyl reactive diluents. In some embodiments, the alkyl acrylates include, but are not limited to, at least one of butyl acrylate, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, and lauryl acrylate.

[0046] In some embodiments, the methacrylate includes, but is not limited to, at least one of hydroxyethyl methacrylate.

[0047] In some embodiments, the methacrylate containing cycloalkanes or benzene rings includes, but is not limited to, at least one of isobornyl methacrylate and glycidyl methacrylate.

[0048] In some embodiments, the vinyl reactive diluent includes, but is not limited to, at least one of styrene (St), N-vinylpyrrolidone (NVP), and vinyl acetate (VA).

[0049] In some embodiments, the multifunctional active diluent includes, but is not limited to, at least one of ethylene glycol diacrylates, propylene glycol diacrylates, butanediol diacrylates, hexanediol diacrylates, pentanediol diacrylates, alkoxylated acrylates, dioxotrope acrylates, alkoxylated bisphenol A diacrylates, and vinyl ethers.

[0050] In some embodiments, the ethylene glycol diacrylates include, but are not limited to, at least one of diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, and ethylene glycol phthalate diacrylate.

[0051] In some embodiments, the propylene glycol diacrylates include, but are not limited to, at least one of dipropylene glycol diacrylate and tripropylene glycol diacrylate.

[0052] In some embodiments, the butanediol diacrylates include, but are not limited to, 1,4-butanediol diacrylates.

[0053] In some embodiments, the pentylene glycol diacrylates include, but are not limited to, neopentylene glycol diacrylates.

[0054] In some embodiments, the hexanediol diacrylates include, but are not limited to, 1,6-hexanediol diacrylates.

[0055] In some embodiments, the alkoxylated acrylates include, but are not limited to, at least one of ethoxylated trimethylolpropane triacrylate and ethoxylated neopentyl glycol diacrylate.

[0056] In some embodiments, the alkoxylated bisphenol A diacrylate includes, but is not limited to, at least one of ethoxylated bisphenol A diacrylate, tetraoxylated bisphenol A diacrylate, and decaoxylated bisphenol A diacrylate.

[0057] In some embodiments, the vinyl ether includes, but is not limited to, at least one of trivinyl glycol divinyl ether and 4-hydroxybutyl vinyl ether.

[0058] In some embodiments, the oligomer includes, but is not limited to, at least one of unsaturated polyesters, epoxy acrylates, polyurethane acrylates, polyester acrylates, and organosilicon oligomers.

[0059] In some embodiments, the unsaturated polyester includes, but is not limited to, at least one of maleic anhydride-type polyester resin, acrylic-type polyester resin, and acrylic epoxy ester-type polyester resin. In some embodiments, the unsaturated polyester is a linear polymer formed by the condensation polymerization of unsaturated dicarboxylic acids or anhydrides with diols, or a linear polymer formed by the condensation polymerization of saturated dicarboxylic acids or anhydrides with diols.

[0060] In some embodiments, the organosilicon oligomer includes, but is not limited to, at least one of vinyl ethoxysilane oligomers and organosilicon polyether acrylates.

[0061] In some embodiments, the initiator includes a type I cleavage photoinitiator, which includes, but is not limited to, at least one of benzoyl photoinitiators, benzoyl ketal photoinitiators, α-hydroxy ketal photoinitiators, and acylphosphine oxide photoinitiators.

[0062] In some embodiments, the benzoyl photoinitiator includes, but is not limited to, at least one of diphenyl ethyl ketone, methyl benzoylformate, and α,α-dimethoxy-α-phenylacetophenone.

[0063] In some embodiments, the benzoyl ketal photoinitiator includes, but is not limited to, at least one of benzoin, benzoin methyl ether, and benzoin isopropyl ether.

[0064] In some embodiments, the α-hydroxyketone photoinitiator includes, but is not limited to, at least one of 2,2-dimethyl-2-hydroxyacetophenone (I-1173), 1-hydroxycyclohexylphenyl ketone (I-184), and diphenyl-(2,4,6-trimethylbenzoyl)phosphorus oxychloride (TPO).

[0065] In some embodiments, the acylphosphine oxide photoinitiator includes, but is not limited to, at least one of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, aromatic acylphosphine oxide, and bisbenzoylphenylphosphine oxide.

[0066] In some embodiments, the crosslinking agent includes a multifunctional active diluent.

[0067] In some embodiments, the multifunctional active diluent includes, but is not limited to, at least one of diethylene glycol diacrylate, polyethylene glycol (diol) diacrylate (such as PEG400-DA, PEG600-DA, etc.), propoxylated neopentyl glycol diacrylate, and 1,6-hexanediol diacrylate.

[0068] In step S2, at the same oxygen concentration, the diffusion depth of small oxygen molecules is directly proportional to the polymerization reaction time; that is, the thickness of the viscous upper layer is directly proportional to the polymerization time. The polymerization reaction time can be adjusted by regulating the initiator, crosslinking agent, or photopolymerization intensity. Therefore, as... Figure 3 As shown, the modulus E1(t) and thickness h1(t) of the viscous upper layer (adhesive layer), which are related to the depth of oxygen diffusion, are both functions of time (oxygen diffusion time). When the thickness of the superelastic is fixed at H, the modulus E2 of the lower layer (which undergoes normal polymerization and is elastic, i.e., the elastic layer) to which no oxygen diffuses is only related to the formulation materials and can be considered as the modulus of the polymer under anaerobic conditions. It is a constant, and its thickness h2(t) depends on H-h1(t). Therefore, the thickness of the elastic lower layer is also a function of time.

[0069] In some embodiments, the oxygen volume concentration in the environment with the preset oxygen concentration is greater than or equal to 5%. In some specific embodiments, the oxygen volume concentration in the environment with the preset oxygen concentration is 5-21% (i.e., the oxygen volume content is 5-21%). Under the same conditions, the lower the oxygen concentration, the slower the oxygen diffusion rate, the shallower the diffusion depth, and the thinner the viscous upper layer, i.e., the adhesive layer. When the preset oxygen concentration is greater than or equal to 5%, sufficient adhesion of the superelastic adhesive can be guaranteed.

[0070] like Figure 4 As shown, the polymerization reaction time should not be too long, otherwise oxygen will diffuse continuously, preventing polymerization and solidification into a gel. Conversely, the polymerization reaction time should not be too short, as oxygen will not have enough time to diffuse and inhibit polymerization, resulting in gel formation and only an elastic bulk layer. A moderate polymerization reaction time determines whether the viscous or elastic properties are superior, based on the thickness of the oxygen diffusion layer and the modulus of the viscous upper layer. Specifically, the crosslinking agent content, initiator content, ultraviolet light intensity, and oxygen concentration all affect the polymerization reaction time. Therefore, the polymerization reaction time can be set according to actual conditions. When using ultraviolet light to irradiate the precursor liquid on the substrate for polymerization, the irradiation time is the polymerization time.

[0071] This invention also provides a superelastic adhesive, which is prepared using the preparation method described above. The superelastic adhesive exhibits low hysteresis and strong adhesion.

[0072] The following detailed description uses specific examples.

[0073] Example 1

[0074] This embodiment provides a method for preparing a superelastic adhesive, including the following steps:

[0075] 85 parts of butyl acrylate, 5 parts of acrylic acid, 5 parts of initiator I-1173, and 5 parts of PEG600-DA were mixed to obtain a precursor solution.

[0076] Add 0.5 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment (oxygen content of 21%).

[0077] At room temperature, 1w / cm 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light (wavelength 365nm) to form a 150μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

[0078] Its 3D optical microscope image is as follows Figure 5 As shown in (a) and (b), it can be seen that the present invention can prepare a superelastic adhesive with a thickness of only 170±20μm.

[0079] Example 2

[0080] This embodiment provides a method for preparing a superelastic adhesive, which differs from Embodiment 1 only in that 1 mL of the precursor is added to a circular groove with a diameter of 5 cm to obtain a superelastic adhesive with a thickness of 300 μm, having an viscous upper layer and an elastic lower layer.

[0081] The elastic recovery of the superelastic adhesive after loading and unloading to a strain of 100% is shown as follows. Figure 6 As shown in (a)-(c), it can be seen that the superelastic adhesive provided in this embodiment has good elastic recovery after loading and unloading to a strain of 100%, and has good elasticity.

[0082] Example 3

[0083] This embodiment provides a method for preparing a superelastic adhesive, which differs from Example 1 only in that 1.5 mL of the precursor is added to a circular groove with a diameter of 5 cm to obtain a superelastic adhesive with a thickness of 500 μm, having an viscous upper layer and an elastic lower layer.

[0084] like Figure 7 As shown in (a) and (b), when the elastic lower layer faces upward, the glass ball rebounds without any sticky stringing, indicating that it has no stickiness or only weak stickiness. When the sticky upper layer faces upward, the sticky stringing phenomenon can be clearly seen when the glass ball rebounds, indicating that it has strong stickiness.

[0085] Example 4

[0086] This embodiment provides a method for preparing a superelastic adhesive, which differs from Embodiment 1 only in that 2 mL of the precursor is added to a circular groove with a diameter of 5 cm to obtain a superelastic adhesive with a thickness of 700 μm, having an viscous upper layer and an elastic lower layer.

[0087] Example 5

[0088] This embodiment provides a method for preparing a superelastic adhesive, including the following steps:

[0089] 90 parts of 1,6-hexanediol diacrylate (HDDA) and 10 parts of initiator I-184 were mixed to obtain a precursor solution;

[0090] Add 1 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment (oxygen content of 21%).

[0091] At room temperature, 1w / cm 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light (wavelength 365nm) to form a 300μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

[0092] Example 6

[0093] This embodiment provides a method for preparing a superelastic adhesive, including the following steps:

[0094] 3 parts styrene, 85 parts butyl acrylate, 7 parts initiator I-1173, and 5 parts PEG400-DA were mixed to obtain the precursor solution;

[0095] Add 1.5 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment (oxygen content of 21%).

[0096] At room temperature, 1w / cm 2 Photopolymerization was carried out for 5 minutes under ultraviolet light (wavelength 365nm) to form a 500μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

[0097] Example 7

[0098] This embodiment provides a method for preparing a superelastic adhesive, including the following steps:

[0099] A precursor solution was obtained by mixing 50 parts of unsaturated polyester condensed with maleic anhydride and ethylene glycol, 40 parts of dodecyl lauryl ester, 8 parts of TPO, and 5 parts of triethylene glycol diacrylate.

[0100] Add 1.5 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment (oxygen content of 21%).

[0101] At room temperature, 1w / cm 2Photopolymerization was carried out for 5 minutes under ultraviolet light (wavelength 365nm) to form a 500μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

[0102] I. Testing the elasticity of the superelastic adhesives in Examples 1-7

[0103] (1) As Figure 8 As shown, loading and unloading hysteresis tests were conducted on the superelastic rubbers in Examples 1-7. Loading and unloading were performed under a given strain. The hysteresis was equal to the area of ​​the hysteresis loop under the stress-stretch ratio curve, i.e., the dissipated energy W. d With the total loading area (i.e., the total loading strain energy W) d The ratio of +We, where We is the recoverable elastic energy. Specifically, the superelastics in Examples 1-7 were prepared into rectangular strip samples, and the hysteresis (hysteresis refers to the ratio of dissipated energy to total strain energy in the process) of one cycle of loading and unloading was measured in the range of 0-1. The smaller the value, the closer it is to entropy elasticity and the better the resilience. The results are shown in Table 1 below.

[0104] Table 1 Results of Loading / Unloading Lag Test

[0105] Example hysteresis Example 1 1％ Example 2 2.5％ Example 3 2.5％ Example 4 4％ Example 5 3％ Example 6 5％ Example 7 3.5％

[0106] The results show that the superelastic adhesive of the present invention has a hysteresis of less than 5% (hysteresis of less than 5% is considered to be superelastic adhesive) and good resilience at a thickness of 150 μm or more.

[0107] II. Testing the tack of the superelastic adhesives in Examples 1-7

[0108] (1) As Figure 9 As shown, the superelastic adhesives in Examples 1-7 were subjected to downward pressure and upward pull tests, and the adhesion force of the glass beads was measured. The results are shown in Table 2 below.

[0109] Table 2 Adhesion test results

[0110] Example Adhesive strength (N) Example 1 0.2 Example 2 0.3 Example 3 0.8 Example 4 0.5 Example 5 0.4 Example 6 1 Example 7 0.6

[0111] It can be seen that the adhesive strength of the superelastic adhesives in Examples 1-7 is between 0.2-1N.

[0112] (2) Figure 10 As shown, the superelastic adhesives in Examples 1-7 were subjected to a 90-degree peel test, with acrylic sheets as the substrate. The bonding performance results are shown in Table 3 below.

[0113] Table 3. Bonding strength test results

[0114] Example <![CDATA[Adhesive strength (J / m 2 )]]> Example 1 40 Example 2 80 Example 3 100 Example 4 130 Example 5 70 Example 6 110 Example 7 90

[0115] As can be seen, the bonding energy between the superelastic adhesive and the acrylic sheet in Examples 1-7 is all between 40-130 J / m.2 Between (greater than 10 J / m) 2 It is believed to have strong viscosity.

[0116] (2) Figure 11 As shown in Table 4, shear strength tests were performed on the superelastic adhesives of Examples 1-7.

[0117] Table 4 Shear strength test results

[0118] Example Shear strength (kPa) Example 1 30 Example 2 45 Example 3 80 Example 4 120 Example 5 50 Example 6 75 Example 7 60

[0119] It can be seen that the shear strength of the superelastic rubber in Examples 1-7 is between 30-120 kPa.

[0120] Example 8

[0121] To investigate the effect of different initiator contents on polymerization, this embodiment provides a method for preparing a superelastic, including the following steps:

[0122] 85 parts of butyl acrylate, 5 parts of acrylic acid, 1-15 parts of initiator I-1173, and 3 parts of PEG600-DA were mixed to obtain the precursor solution.

[0123] Add 1 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment (oxygen content of 21%).

[0124] At room temperature, 1w / cm 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light (wavelength 365nm) to form a 300μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

[0125] When the initiator I-1173 is 1 part, it cannot be cured;

[0126] When the initiator I-1173 is 3-7 parts, it can cure with a hysteresis of 7-8% and an adhesion energy of 50-100 J·m. -2 between;

[0127] When the initiator I-1173 is 9-15 parts, it can cure with a hysteresis of less than 5% and an adhesion energy of 50-100 J·m. -2 between.

[0128] Furthermore, when forming a 500μm thick superelastic adhesive, initiator I-1173 in amounts of 3-15 parts can polymerize to obtain a low-hysteresis superelastic adhesive with an adhesion range of 100-150 J·m. -2 The adhesive energy is thickness-dependent; within the characteristic fracture dimension, the adhesive energy is proportional to the thickness.

[0129] Therefore, the amount of initiator affects whether a superelastic rubber can be formed, and the specific amount can be adjusted according to the actual situation.

[0130] Example 9

[0131] Using the same preparation method, thickness also affects the performance of the product. This example illustrates the process using an environment with 100% oxygen content.

[0132] This embodiment provides a method for preparing a superelastic adhesive, including the following steps:

[0133] 85 parts of butyl acrylate, 5 parts of acrylic acid, 11 parts of initiator I-1173, and 3 parts of PEG600-DA were mixed to obtain the precursor solution.

[0134] Add 1-2 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an environment with 100% oxygen content; maintain the solution at room temperature and 1 w / cm². 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light (wavelength 365nm) to form a gradient adhesive of different thicknesses with an viscous upper layer and an elastic lower layer.

[0135] When the volume of the precursor liquid is 1 mL, a gradient gel with a thickness of 300 μm is obtained, but the curing is poor.

[0136] When the volume of the precursor liquid is 1.2 mL, a gradient adhesive with a thickness of 400 μm is obtained. It can be cured, but the hysteresis is between 7-8%, which does not meet the requirements of the superelastic adhesive.

[0137] When the precursor liquid volume is 1.5 mL, a gradient adhesive with a thickness of 500 μm is obtained, which can cure with a hysteresis of around 3% and an adhesion energy of 100 J·m. -2 It meets the requirements for super elastic rubber;

[0138] When 2 mL of the precursor liquid was used, a gradient adhesive with a thickness of 700 μm was obtained. It could cure with a hysteresis of approximately 3% and an adhesion energy of 150 J·m⁻¹. -2 It meets the requirements for super elastic rubber.

[0139] It is evident that, under the same preparation conditions, the thickness of the product (also known as the thickness of the precursor liquid layer) also affects its performance. Therefore, the specific thickness of the precursor liquid layer can be adjusted according to actual conditions to prepare a superelastic adhesive with a viscous upper layer and an elastic lower layer.

[0140] In summary, this invention provides a superelastic adhesive and its preparation method. The invention involves transferring a precursor liquid containing monomers, initiators, and crosslinking agents onto a substrate, and then placing it in an environment with a preset oxygen concentration. Oxygen diffuses from the surface of the precursor liquid onto the substrate into the precursor liquid body. The area reached by oxygen diffusion is the upper layer, and the area not reached by oxygen diffusion is the lower layer. In the upper layer where oxygen diffusion is possible, the reactive free radicals at each stage react more readily with oxygen to form more stable peroxides, inhibiting chain growth during monomer polymerization and almost preventing chain crosslinking. This results in shorter polymer chains or uncrosslinked suspended chains. The properties of these chains are closer to those of viscous liquids, exhibiting interfacial wettability with the substrate. Simultaneously, these chains form topological entanglements or physical crosslinks, increasing viscous dissipation, thus forming a network adhesive layer composed of defects in the shorter polymer chains or uncrosslinked suspended chains (i.e., a network adhesive layer with more defects and lower crosslinking density), forming a viscous upper layer. In the lower layer where oxygen diffusion is unavailable, free radical polymerization proceeds normally, including chain initiation, chain growth, chain crosslinking, and chain termination reactions, forming an elastic lower layer. Therefore, this invention can prepare a thin-film superelastic adhesive with low hysteresis and strong adhesion using a one-step gas-barrier polymerization method. The preparation method provided by this invention is simple, and the resulting superelastic adhesive exhibits low hysteresis, strong adhesion, and thin film thickness, thus possessing broad application prospects.

[0141] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a superelastic adhesive, characterized in that, Including the following steps: 85 parts of butyl acrylate, 5 parts of acrylic acid, 5 parts of initiator I-1173, and 5 parts of PEG600-DA were mixed to obtain a precursor solution. Add 0.5 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment; At room temperature, 1w / cm 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light with a wavelength of 365nm to form a superelastic adhesive with a thickness of 150μm, which has an viscous upper layer and an elastic lower layer.

2. A method for preparing a superelastic adhesive, characterized in that, Including the following steps: 85 parts of butyl acrylate, 5 parts of acrylic acid, 5 parts of initiator I-1173, and 5 parts of PEG600-DA were mixed to obtain a precursor solution. Add 1 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment; At room temperature, 1w / cm 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light with a wavelength of 365nm to form a 300μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

3. A method for preparing a superelastic adhesive, characterized in that, Including the following steps: 85 parts of butyl acrylate, 5 parts of acrylic acid, 5 parts of initiator I-1173, and 5 parts of PEG600-DA were mixed to obtain a precursor solution. Add 1.5 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment; At room temperature, 1w / cm 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light with a wavelength of 365nm to form a 500μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

4. A method for preparing a superelastic adhesive, characterized in that, Including the following steps: 85 parts of butyl acrylate, 5 parts of acrylic acid, 5 parts of initiator I-1173, and 5 parts of PEG600-DA were mixed to obtain a precursor solution. Add 2 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment; At room temperature, 1w / cm 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light with a wavelength of 365nm to form a superelastic adhesive with a thickness of 700μm, which has an viscous upper layer and an elastic lower layer.

5. A method for preparing a superelastic adhesive, characterized in that, Including the following steps: 90 parts of 1,6-hexanediol diacrylate and 10 parts of initiator I-184 were mixed to obtain a precursor solution; Add 1 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment; At room temperature, 1w / cm 2 Photoinitiated polymerization was carried out for 5 minutes under ultraviolet light with a wavelength of 365nm to form a 300μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

6. A method for preparing a superelastic adhesive, characterized in that, Including the following steps: 3 parts styrene, 85 parts butyl acrylate, 7 parts initiator I-1173, and 5 parts PEG600-DA were mixed to obtain a precursor solution. Add 1.5 mL of the precursor solution to a circular trough with a diameter of 5 cm and place it in an air environment; At room temperature, 1w / cm 2 Photopolymerization was carried out for 5 minutes under ultraviolet light with a wavelength of 365nm to form a 500μm thick superelastic adhesive with an viscous upper layer and an elastic lower layer.

7. A superelastic adhesive, characterized in that, It is prepared by the preparation method described in any one of claims 1-6.

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