High-resilience foamed acrylic substrate and method for preparing the same

Abstract

This invention provides a high-resilience foamed acrylic substrate and its preparation method, relating to the field of adhesives for homopolymers or copolymers of esters, and particularly to acrylate adhesives. The substrate is composed of acrylic oligomers, acrylate-modified resins, crosslinking agents, dynamically crosslinked resins, photoinitiators, inorganic pigments, and foaming agents in specific weight proportions. Its core lies in constructing a dual-dynamic reversible crosslinking network within a static covalent network using a dynamically crosslinked acrylic resin containing disulfide bonds and UPy-modified polycaprolactone prepolymer. The key to the preparation method is the "UV curing" and heat treatment processes. This invention enables the material to simultaneously possess low density, high tensile strength, and elongation at break, especially achieving high resilience (85%) and extremely low compression set (8%), and possessing potential self-healing capabilities. It effectively solves the problem of poor thickness recovery after compression in traditional cushioning materials, making it suitable for high-end electronics, precision instruments, and other fields.

Description

Technical Field

[0001] This invention relates to the field of adhesives for homopolymers or copolymers of esters, and more particularly to acrylate adhesives. Background Technology

[0002] Foamed acrylic is a synthetic material made from acrylic compounds through foaming technology, possessing excellent shock absorption and cushioning properties. Using foamed acrylic as a reinforcing substrate can reduce damage to electronic components caused by external forces, drops, or impacts, extending their lifespan. Currently, reinforcing adhesives made from acrylic foamed acrylic are widely used in electronics, automotive, construction, and furniture industries, with substantial demand in these sectors, indicating a huge market potential. To achieve the cushioning performance of the substrate, the porous structure within the foamed acrylic reinforcing adhesive is essential. This porous structure absorbs impact energy, achieving a good cushioning effect. However, during application, the acrylic reinforcing adhesive undergoes bonding and pressure, often resulting in a reduction in thickness due to pressure, affecting the shock absorption and cushioning effect. Therefore, this places higher demands on the resilience of the acrylic substrate itself. Summary of the Invention

[0003] The purpose of this invention is to provide a high-resilience foamed acrylic substrate and its preparation method. The substrate is composed of acrylic oligomers, acrylate-modified resins, crosslinking agents, dynamically crosslinking resins, photoinitiators, and foaming agents in specific weight proportions. Its core lies in constructing a dual-dynamic reversible crosslinking network within a static covalent network using a dynamically crosslinked acrylic resin containing disulfide bonds and a UPy-modified polycaprolactone prepolymer. The key to the preparation method is the "UV curing" and heat treatment process: first, UV irradiation rapidly shapes the coating and strengthens the static network; then, low-temperature heat treatment activates the dynamic network, promoting disulfide bond exchange and UPy hydrogen bond recombination. This invention enables the material to simultaneously possess low density, high tensile strength, and elongation at break, especially achieving high resilience (85%) and extremely low compression set (8%), and possessing potential self-healing capabilities. It effectively solves the problem of poor thickness recovery after compression in traditional cushioning materials, making it suitable for high-end electronics, precision instruments, and other fields. The specific solution is as follows:

[0004] A highly resilient foamed acrylic substrate includes an acrylic oligomer, an acrylate-modified resin, a crosslinking agent, a dynamically crosslinking resin, a photoinitiator, an inorganic pigment, and a foaming agent.

[0005] Further, by weight, it includes 100 parts of acrylic oligomer, 5-30 parts of dynamic crosslinking resin, 1-3 parts of acrylate modified resin, 0.02-1 parts of crosslinking agent, 0.1-2 parts of photoinitiator, 0-2 parts of inorganic pigment, and 1-5 parts of foaming agent.

[0006] Further, by weight, it includes 100 parts of acrylic oligomer, 18 parts of dynamic crosslinking resin, 2 parts of acrylate modified resin, 0.5 parts of crosslinking agent, 1.5 parts of photoinitiator, 1 part of inorganic pigment, and 3 parts of foaming agent.

[0007] Furthermore, the acrylic oligomer is a linear polymer synthesized from various monofunctional acrylic monomers, including acrylic acid, isobornyl acrylate, isooctyl acrylate, isodecanyl acrylate, butyl acrylate, lauryl acrylate, (3,3,5)-trimethylcyclohexyl acrylate, stearic acid acrylate, and phenoxybenzyl acrylate; the crosslinking agent is an acrylate with bifunctional or multiple functional groups, including 1,4-butanediol acrylate, (3-ethoxy)bisphenol fluorene acrylate, and dipropylene glycol dipropylene. Acrylates, 1,6-hexanediol acrylate, polyethylene glycol (200) diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate; acrylate-modified resins are difunctional or multifunctional acrylate-modified resins with resilience, grafted or modified with epoxy resins, polyurethane resins, polyester resins and acrylic polymers, including any one or a mixture of two of epoxy acrylates, polyurethane acrylates, and polyester acrylates; the photoinitiator is ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 4- The inorganic pigment is any one or a mixture of at least two of the following: ethyl dimethylaminobenzoate, 1-hydroxycyclohexylphenyl ketone, bis(2,6-difluoro-3-pyrrolephenyl)dicenoctane, and benzophenone; the inorganic pigment is any one or a mixture of at least two of the following: titanium dioxide, chrome yellow, iron blue, cadmium red, cadmium yellow, lithopone, carbon black, iron oxide red, and iron oxide yellow; the chemical foaming agent is a microporous material based on plastic or rubber polymers, which has been pre-heat-treated to contain a large number of air bubbles and does not require further foaming, including polyurethane foaming agents and polystyrene foaming agents. The foaming agent is any one or a mixture of at least two of the following: polyolefin foaming agent, polyvinyl chloride foaming agent, phenolic foaming agent, epoxide resin foaming agent, nitrile rubber foaming agent, and thermoplastic elastomer foaming agent; the dynamically crosslinked resin is a dynamic acrylic resin containing disulfide bonds, a Diels-Alder thermally reversible resin based on furan / maleimide, UPy-modified polycaprolactone (PCL-U) prepolymer, UPy-modified polyurethane (PU-U) prepolymer, and highly elastic thermoplastic polyurethane (TPU) particles.

[0008] A method for preparing a high-resilience foamed acrylic substrate includes the following steps: S1. Premixing and degassing: The acrylic oligomer, dynamic crosslinking resin, acrylate modified resin, crosslinking agent, photoinitiator, inorganic pigment and foaming agent are thoroughly mechanically mixed under light-protected conditions, and then vacuum degassing is performed to obtain a uniform foamed acrylic substrate coating liquid. S2, Coating and Encapsulation: The coating liquid obtained in S1 is quantitatively coated onto the lower transparent release film, and then the upper transparent release film is covered. The coating thickness is controlled by roller pressing to form a "sandwich" structure. S3, UV curing and dynamic network activation: The material encapsulated in step S2 is placed in a UV curing device for irradiation and curing, which initiates the free radical polymerization of acrylic oligomers and the crosslinking reaction with the crosslinking agent to form the first static network; then, the cured material is heat-treated in an oven to activate the reversible bonds in the dynamic crosslinking resin, so that it can fully participate in the construction of the second dynamic reversible network that runs through the static network. S4. Cooling and curing: Cool the heat-treated material to room temperature, cure it, and then peel off the release film to obtain the high-resilience and compression-resistant acrylic foam substrate.

[0009] Compared with the prior art, the present invention has at least one of the following technical effects: 1) This invention solves the industry problem of poor thickness recovery and rapid decay of cushioning performance in traditional foamed materials after compression. Background technology indicates that acrylic cushioning materials suffer from reduced cushioning effect due to thickness reduction after bonding and pressure application. This invention introduces a "dual dynamic reversible network" composed of disulfide bonds and UPy hydrogen bonds, endowing the material with an intelligent deformation recovery mechanism. When the material is compressed, the UPy hydrogen bonds act like countless microscopic springs, efficiently dissipating impact energy through reversible, step-by-step dissociation; simultaneously, the disulfide bonds undergo dynamic exchange, releasing localized stress concentration and preventing permanent network damage. After the external force is removed, the UPy hydrogen bonds can instantly recombine at the new position of the chain segment rebound at microsecond speeds, precisely locking elastic deformation; while the disulfide bonds complete network topology reconstruction in the subsequent thermal environment. This dual protection at the molecular level enables the material of this invention (as in Example 1) to achieve a thickness recovery rate of over 90% (i.e., 8% permanent compression deformation) and a springback rate as high as 85% after undergoing 50% compression. This means that when applied to the buffering of electronic devices, the material can almost completely maintain the initial buffer gap after multiple impacts or long-term static pressure, providing durable and stable protection and overcoming the performance failure problem caused by thickness decay.

[0010] 2) This invention employs a synergistic process of "UV pre-curing + heat treatment." First, UV curing acts like a rapid setting technique, forming a robust polymer preform. Subsequently, heat treatment plays a crucial role: 90°C serves as a "dedicated stage for dynamic network activation," providing a mild yet sufficient energy and time window for the exchange rearrangement of disulfide bonds and the full, orderly recombination of UPy hydrogen bonds, ensuring that the dynamic bonds maximize their functional efficiency. This process ensures that a high-performance dynamic network is precisely "woven" into a porous static framework, enabling the material to simultaneously possess high resilience, high strength, and low permanent deformation at a low density (0.25 g / cm³), resulting in overall performance superior to conventional simple blends.

[0011] 3) This invention achieves ultra-high resilience while endowing the material with inherent self-healing potential and excellent durability, expanding its application prospects in the field of high-end precision equipment. The dynamic covalent network of disulfide bonds introduced into the material gives it inherent self-healing capabilities. When the material develops micro-cracks due to extreme impact, the disulfide bonds at the damaged site can undergo a reversible metathesis reaction under moderate heat or stress stimulation, achieving "bond reconnection" and healing the crack. This characteristic significantly improves the material's reliability and service life under long-term cyclic loading, avoiding the degradation of cushioning performance caused by the accumulation of micro-damage. Combined with its excellent normal-temperature flexibility and fatigue resistance, this material not only meets the needs of conventional packaging cushioning but is also suitable for precision fields with extremely stringent reliability requirements, such as long-term cushioning of foldable screen phone hinges, shockproof packaging of precision optical instruments, impact-resistant padding layers for new energy vehicle battery packs, and cushioning components for high-end sports equipment. This opens up a completely new high-value-added market for traditional acrylic foam materials, with huge technological competitiveness and market potential. Detailed Implementation

[0012] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0013] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0014] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0015] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0016] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0017] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0018] This invention relates to the sources of various substances: isobornyl acrylate has the CAS number 103-11-7 and the molecular formula C. 13 H 20 O2; the CAS number for isooctyl acrylate is 29590-42-9, and its molecular formula is C. 11 H 20 O2; the crosslinking agent 1,4-butanediol acrylate has the CAS number 2479-42-1 and the molecular formula C7H 10 O3; the photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate has the CAS number 84434-11-7 and the molecular formula is C. 18 H 21 O3P; Benzophenone's CAS number is 119-61-9, and its molecular formula is C. 13 H 10 O; the CAS number of the inorganic pigment titanium dioxide is 13463-67-7, and the molecular formula is TiO2; the CAS number of iron oxide red is 1309-37-1, and the molecular formula is Fe2O3; all of the above are common commercially available products; dynamic acrylic resin with disulfide bonds refers to a polymer of side chain or terminal disulfide bonds (-SS-) and acrylate functional groups, purchased from Xi'an Ruixi Biotechnology Co., Ltd.; UPy modified polycaprolactone (PCL-U) prepolymer is made by grafting ureidopyrimidinone (UPy) groups onto the end of ordinary PCL polyol, purchased from Yisheng New Materials (Suzhou) Co., Ltd.; polyurethane foaming agent is purchased from Guangzhou Yourun Synthetic Materials Co., Ltd., model WCAT-F30 controllable micro-foaming environmentally friendly foaming agent.

[0019] Example 1 A high-resilience foamed acrylic substrate comprises, by weight, 100 parts of acrylic oligomer (isoborneol acrylate, acrylic acid and isooctyl acrylate 2:1:7), 2 parts of acrylate modified resin (epoxy acrylate and polyurethane acrylate 1:1), 0.5 parts of crosslinking agent (1,4-butanediol acrylate), 18 parts of dynamic crosslinking resin (dynamic acrylic resin containing disulfide bonds and UPy modified polycaprolactone (PCL-U) prepolymer 1:1), 1.5 parts of photoinitiator (ethyl 2,4,6-trimethylbenzoylphenylphosphonate: benzophenone 2:1), 1 part of inorganic pigment, and 3 parts of foaming agent (polyurethane foaming agent).

[0020] The preparation method of the above-mentioned high resilience foamed acrylic substrate includes the following steps: S1. Premixing and Degassing: First, pre-disperse the pigment: Mix 1 part titanium dioxide and 15 parts iron oxide red with about 15 parts isooctyl acrylate in a small high-speed disperser to make a uniform pigment slurry; In the main mixing tank, add the remaining 85 parts of acrylic oligomer, 1 part each of epoxy acrylate and polyurethane acrylate, and 9 parts each of dynamic acrylic resin containing disulfide bonds and UPy modified polycaprolactone (PCL-U) prepolymer, and mix at 200 rpm for 20 minutes to allow the resin to initially impregnate; Increase the speed to 500 rpm for medium-speed dispersion for 30 minutes; Finally, shear at 800 rpm for 40 minutes, for a total of 90 minutes, to ensure that the dynamic resin is completely dispersed and compatible, and that the system is homogeneous and free of gel particles; While stirring at 500 rpm, add 0.5 parts of 1,4-butanediol acrylate, 1 part of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 0.5 parts of benzophenone in sequence. Stir for 20 minutes, then reduce the speed to 200 rpm and slowly sprinkle in 3 parts of polyurethane foaming agent. Stir for 10 minutes to prevent the foaming agent from decomposing prematurely due to shear heat. Transfer to a vacuum degassing machine and degas at -0.095 MPa for at least 25 minutes until the liquid surface is calm and free of bubbles. S2. Coating and Encapsulation: Using a coating machine, the degassed coating liquid is evenly coated onto a 125μm PET release film (release force 50g / in) with a set thickness of 1.0mm. Immediately cover it with another layer of the same release film and roll it with a laminating machine under a pressure of 0.3MPa to ensure that there are no air bubbles and the thickness is uniform. S3, UV Curing and Dynamic Network Activation: The "sandwich" structure is placed on the conveyor belt of the UV curing machine; a medium-pressure mercury lamp with a main wavelength of 365nm is used, and the lamp distance is adjusted to make the irradiance of the sample surface 60mW / cm², and curing is completed by passing through the irradiation zone (irradiation for 70 seconds). Heat treatment in a forced-air drying oven: Dynamic network activation and optimization: The temperature is set to 90°C and heat-treated for 40 minutes. This extended time is designed to ensure that the high content of disulfide bonds and UPy hydrogen bonds have sufficient opportunity to undergo adequate exchange and recombination to build a dense dynamic network.

[0021] S4. Cool at room temperature for 2 hours, then cure flat at 23°C / 50%RH for 48 hours, and then peel off the release film.

[0022] Acrylic oligomers (isobornyl acrylate, acrylic acid and isooctyl acrylate 2:1:7) constitute the material's skeleton. Hard monomers (isobornyl acrylate and acrylic acid) provide rigidity and strength, while soft monomers (isooctyl acrylate) provide flexibility and chain segment mobility. Together, they form a static covalent network that combines rigidity and flexibility, which is the source of elasticity that enables resilience.

[0023] Acrylic-modified resins (epoxy:polyurethane = 1:1) provide reinforcement and toughening. Epoxy acrylates improve adhesion and hardness, while polyurethane acrylates enhance flexibility and impact resistance. Both are embedded in the main network, improving the overall mechanical properties and durability of the material and ensuring compatibility with subsequent dynamic resins.

[0024] 1,4-Butanediol diacrylate, as a multifunctional crosslinking monomer, participates in the UV curing reaction through the acrylate double bonds at both ends to form a permanent static covalent crosslinking network, providing the material with basic structural rigidity and dimensional stability.

[0025] Photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate and benzophenone efficiently initiate UV curing. The combination of the two absorbs ultraviolet light of different wavelengths (around 365nm), generates free radicals, and efficiently initiates the polymerization reaction of acrylic oligomers and crosslinking agents, rapidly forming a "sandwich" structured solid preform in the first step, fixing the initial shape.

[0026] Polyurethane foaming agents create a cell structure. This cell structure is the macroscopic physical basis for achieving high resilience, effectively buffering and dispersing stress.

[0027] Titanium dioxide and iron oxide red provide opacity and color. During the pre-dispersion stage, a pigment paste is formed with a portion of the resin to ensure uniform dispersion in the final substrate, without affecting optical properties and mechanical integrity.

[0028] The static covalent network (formed by acrylic oligomers and static crosslinking agents) is the permanent framework, providing basic strength and shape memory. The dual dynamic network (a covalently reversible network of disulfide bonds + a physically reversible network of UPy) is the functional core, like a "reconfigurable steel beam" and a "high-performance spring" embedded in the framework, jointly responsible for dissipating stress, rapid rebound, and damage repair.

[0029] UV curing ensures rapid shaping; heat treatment first strengthens the static network, then optimizes the dynamic network under mild conditions to ensure the perfect construction of the cell structure and the dual dynamic network. This is the key process design for achieving high resilience and low compression set.

[0030] Disulfide bond exchange requires a certain amount of heat / stress to drive it, and recombination is relatively slow; it is mainly responsible for long-term shape recovery and self-repair. UPy hydrogen bonds dissociate / recombine extremely quickly, mainly responsible for instantaneous shock buffering and rapid rebound. Both are precisely activated and optimized during heat treatment (heat treatment mainly targets disulfide bonds, while the low-temperature stage mainly targets UPy hydrogen bond recombination): Dynamically crosslinked resins (DSSD & UPy): These introduce dynamic, reversible crosslinking points into the main network formed by acrylic oligomers and crosslinking agents. Disulfide bonds can reversibly exchange under moderate heat / stress, while UPy quadruple hydrogen bonds can rapidly and reversibly combine, collectively endowing the material with high resilience, resistance to compression deformation, and self-healing capabilities. Heat treatment primarily promotes the exchange and rearrangement of disulfide bonds, enhancing the overall network integrity; the subsequent mild low-temperature phase is a crucial window for optimizing and reorganizing UPy hydrogen bonds. The synergy of both ensures the perfect construction of the dynamic network within the foamed structure.

[0031] Under heat or stress, disulfide bonds can undergo metathesis exchange with other thiols or disulfide bonds, thereby achieving topological restructuring without changing the overall crosslinking density of the network. The chemical equation for metathesis exchange is as follows: R1-SS-R2+R3-SS-R4<--(thermal / stress)-->R1-SS-R3+R2-SS-R4 When a material experiences stress concentration due to localized pressure or damage, the disulfide bonds at that location will exchange, releasing stress, preventing crack propagation, and reforming new bonds during heat treatment, thereby achieving macroscopic self-healing and resistance to permanent compressive deformation.

[0032] The UPy units form dimers through self-complementary, highly directional quadruple hydrogen bonds, resulting in extremely high binding constants (Kdim > 10 in chloroform). 7 M -1 It resembles some covalent bonds, but its binding and dissociation are fast and reversible: Dimerization equilibrium reaction equation:

[0033] (UPy unit on a single chain) External force removal (dimer formed through quadruple hydrogen bonds) As a super-strong dynamic physical cross-linking point, UPy dimer undergoes hydrogen bond dissociation in stages and sequence like "molecular Velcro" when subjected to force, dissipating a large amount of energy. After the external force is removed, the polymer chain spontaneously retracts due to entropy increase. At this time, the four-fold hydrogen bonds of UPy dimer can instantly recombine at the new position of the retracted chain segment at a speed of microseconds. Like countless precise "molecular buckles", they lock the released elastic potential energy and the retracted conformation in an instant, thus efficiently and losslessly converting the microscopic entropy elasticity into macroscopic shape recovery, driving the material to rebound rapidly. This is the key to the material achieving a high resilience rate.

[0034] DSSD resin (i.e., dynamic acrylic resin with disulfide bonds, where "D" represents the polymer chain segment of the resin, usually an acrylate skeleton; "-SS-" represents the disulfide bond connecting two polymer chain segments, i.e. a sulfur-sulfur single bond; indicating the chemical structure of a disulfide bond (-SS-) connecting two polymer chain segments (D) at both ends) is like a "reconfigurable steel beam skeleton" of a building, providing long-term stability and damage repair capabilities. UPy prepolymer (UPy prepolymer is a triblock structure, the core of which is a flexible polycaprolactone (PCL) long chain as the "soft segment", while ureidopyrimidinone (UPy) groups are branched at both ends or sides of the long chain as "functional ends". The UPy groups at both ends can be efficiently combined with UPy on other chains through quadruple hydrogen bonds, thereby forming a reversible physical cross-linking network) is like a "high-performance spring" that runs throughout the skeleton, providing instant buffering and rapid rebound. Both are embedded in the static covalent network formed by acrylic oligomers and cross-linking agents, and the final result is an advanced foaming material with high strength, high resilience, low permanent deformation and self-healing potential. This is the fundamental molecular mechanism of the significant improvement in performance (low compression set and high resilience) of Examples 1-3.

[0035] DSSD resin has an acrylate polymer backbone, with dynamic covalent bonds introduced through disulfide (-SS-) segments or crosslinking agents. Its core structural unit can be represented as follows: ; Here, ~~ represents the continuation of the polymer chain, -(CH2-CH-). m With -(CH-CH2) nThe polymer chain segment representing acrylates (such as methyl methacrylate, butyl acrylate, etc.) is represented by R1 to R4, which represent different ester side chains (such as methyl, ethyl, butyl, etc.). -R-[SS]-R'- is the key part for introducing disulfide dynamic bonds. R and R' are usually flexible alkyl chains (such as -(CH2)6-) or linking groups containing ester or urethane groups, used to bridge disulfide bonds to the polymer backbone or side chains. Under heat or stress, the disulfide bond (-SS-) can undergo a reversible metathesis exchange reaction, realizing network topology reconstruction and endowing the material with self-healing and stress relaxation capabilities.

[0036] UPy-modified polycaprolactone (PCL-U) prepolymer is a prepolymer whose polycaprolactone chain ends are modified by UPy (ureidopyrimidinone) groups. Its typical triblock structure is as follows: ; Wherein -[O-(CH2)5-C-] k It is a flexible long chain of polycaprolactone (PCL), serving as the soft segment of the material, providing flexibility and chain mobility. k represents the degree of polymerization. The two ends, UPy─NH-(CH2)5-, are functional end groups. The terminal amino groups (-NH-) are attached to the PCL chain ends via caprolactam ring-opening reactions or reactions with isocyanates. The dynamic crosslinking mechanism of UPy dimers: the UPy groups on the two prepolymer molecular chains can form dimers through extremely strong quadruple hydrogen bonds. Their binding and dissociation are rapid and reversible, which is key to achieving high resilience in the material.

[0037] Example 2 A high-resilience foamed acrylic substrate comprises, by weight, 100 parts of acrylic oligomer (isobornyl acrylate, acrylic acid and isooctyl acrylate 2:1:7), 5 parts of dynamic crosslinking resin (dynamic acrylic resin containing disulfide bonds and UPy modified polycaprolactone (PCL-U) prepolymer 1:1), 3 parts of acrylate modified resin (epoxy acrylate and polyurethane acrylate 1:1), 0.02 parts of crosslinking agent (1,4-butanediol acrylate), 0.1 parts of photoinitiator (ethyl 2,4,6-trimethylbenzoylphenylphosphonate: benzophenone 2:1), 2 parts of inorganic pigment, and 1 part of foaming agent (polyurethane foaming agent).

[0038] The preparation method differs from the steps in Example 1 in that: S3, UV curing and dynamic network activation: Adjust the UV irradiance to 120mW / cm² and extend the exposure time to 90 seconds to provide sufficient penetration energy; Heat treatment in a forced-air drying oven: Dynamic network activation and optimization: 90°C, 20 minutes; due to the low content of dynamic resin, the construction of dynamic networks is relatively easy, and the time for this stage can be appropriately shortened.

[0039] Example 3 A high-resilience foamed acrylic substrate comprises, by weight, 100 parts of acrylic oligomer (isobornyl acrylate, acrylic acid and isooctyl acrylate 2:1:7), 30 parts of dynamic crosslinking resin (dynamic acrylic resin containing disulfide bonds and UPy modified polycaprolactone (PCL-U) prepolymer 1:1), 1 part of acrylate modified resin, 1 part of crosslinking agent, 2 parts of photoinitiator (ethyl 2,4,6-trimethylbenzoylphenylphosphonate: benzophenone 2:1), and 5 parts of foaming agent (polyurethane foaming agent).

[0040] The preparation method differs from the steps in Example 1 in that: S3, UV curing and dynamic network activation: UV curing and dynamic network activation: Since there is no pigment, the UV irradiance is adjusted to 80mW / cm² and the exposure time is adjusted to 60 seconds. Heat treatment in a forced-air drying oven: Dynamic network activation and optimization: 90°C, 50 minutes; the ultra-long mild heat treatment time is to ensure that the ultra-high content of dynamic bonds (disulfide bonds and UPy) can complete sufficient dynamic exchange and optimized arrangement to achieve the best rebound and self-healing performance.

[0041] Comparative Example 1 The difference from Example 1 is that the formulation does not contain a foaming agent.

[0042] Comparative Example 2 The difference from Example 1 is that the formulation does not contain crosslinking agents and photoinitiators.

[0043] Comparative Example 3 The difference from Example 1 is that the formulation does not contain dynamic crosslinking resin (dynamic acrylic resin with disulfide bonds and UPy modified polycaprolactone (PCL-U) prepolymer 1:1), and the above substances are not added in the preparation process. The remaining components / processes are the same as in Example 1.

[0044] Performance testing and analysis: Density: According to GB / T 6343-2009 "Determination of Apparent Density of Foamed Plastics and Rubber", cut regular-shaped samples, measure the mass of the sample in air using an electronic balance with an accuracy of at least 0.1 mg, and measure its dimensions using vernier calipers (accuracy 0.02 mm) to calculate the volume. The apparent density is calculated by dividing the mass by the volume. This method is applicable to both closed-cell and open-cell foams and is the basic standard for determining the density of porous materials.

[0045] Compression set: According to Method A (Isothermal deformation method) of GB / T 6669-2008 "Determination of Compression Set of Flexible Foam Polymer Materials". The sample is compressed to 50% of its original thickness in a 70°C oven using a compression set tester (including parallel restraint plates) and held for 22 hours. After removal, it is allowed to recover at room temperature for 30 minutes, and the final thickness is measured. The percentage of thickness loss is the compression set value.

[0046] Rebound rate: According to GB / T 6670-2008 "Determination of rebound performance of flexible foam polymer materials by falling ball method". Using a falling ball rebound tester, a steel ball of specified diameter and mass is dropped freely from a fixed height onto the surface of a horizontally placed sample. The maximum height of the rebound is measured, and the percentage of the rebound height to the drop height is the rebound rate.

[0047] Tensile strength and elongation at break: According to GB / T 6344-2008 "Determination of tensile strength and elongation at break of flexible foam polymer materials". Using a universal testing machine, the dumbbell-shaped specimen is stretched at a specified speed (e.g., 500 mm / min) until it breaks. The testing machine automatically records the maximum tensile force and the elongation between the gauge length and the breakage point. The tensile strength (maximum tensile force / original cross-sectional area) and elongation at break (elongation at break / original gauge length × 100%) are calculated respectively.

[0048] Table 1 shows the performance parameters of various embodiments and comparative examples:

[0049] Table 1 Example 1 (Optimal Example): All performance indicators fall within the preset reference range, and achieve an optimal balance in the two core buffer indicators of resilience (85%) and compression set (8%). This is due to the golden ratio of 18 parts dynamic crosslinking resin and 3 parts foaming agent, as well as precise process control, which enables the static network skeleton and the dual dynamic reversible network to achieve ideal synergy.

[0050] Compared to Example 1, Example 2 exhibits a decline in performance: its dynamic crosslinking resin content (5 parts) is severely insufficient, resulting in sparse reversible crosslinking points and an inability to effectively dissipate impact energy and rebuild the network. Consequently, the resilience rate barely meets the standard (80%), while the compression set reaches its upper limit (20%). Simultaneously, the foaming agent content is the lowest (1 part), leading to an underdeveloped cell structure and thus the highest density (0.75 g / cm³). Furthermore, the material is relatively hard and lacks flexibility, with a significantly lower elongation at break (320%) compared to Example 1.

[0051] Compared to Example 1, Example 3 exhibits a divergence in performance: its extremely high dynamic resin content (30 parts) creates an extremely dense dynamic network, resulting in the highest resilience (88%) and lower compression set (12%). However, the excessively high proportion of dynamic network relatively "dilutes" the static covalent network that serves as the permanent skeleton, leading to a decrease in tensile strength (0.95 MPa). Simultaneously, the highest foaming agent content (5 parts) generates numerous cells, following the logic that "higher foaming agent content results in lower density," resulting in the lowest density (0.52 g / cm³). However, the excessive cells also introduce numerous structural defects and stress concentration points, making the material more prone to rupture at the cells during stretching, thus significantly reducing the material's ductility. This reflects the inherent logic that "higher foaming agent content leads to lower elongation at break," with its elongation at break (300%) barely reaching the lower limit of the reference range.

[0052] Comparative Example 1: Without foaming agent, it cannot form a porous structure. The material is a dense solid, lacking the deformation space of pores to buffer stress. All stress is borne by the matrix, leading to irreversible plastic deformation. Therefore, its compression set is extremely high (70%), its resilience is extremely low (25%), and its elongation at break drops sharply, completely losing its function as a buffer material.

[0053] Comparative Example 2: Lacking photoinitiators and crosslinking agents, an initial static covalent network could not be formed through UV curing. The mixture remained in a liquid or extremely weak gel state, unable to acquire any mechanical strength, thus all performance tests could not be conducted, demonstrating the necessity of the static network as the "skeleton" of the dynamic network.

[0054] Compared with Example 1, Comparative Example 3 completely lacks the dual dynamic reversible network constructed by disulfide bonds and UPy hydrogen bonds. As a result, the material cannot dissipate energy through the reversible breakage of dynamic bonds during compression, nor can it drive the chain segment rebound by rapid recombination after decompression. Therefore, its compression permanent deformation deteriorated sharply from 8% to 35%, and the rebound rate dropped significantly from 85% to 62%, directly proving that the dynamic crosslinking resin is the core to achieving high rebound and low deformation.

[0055] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0056] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

Claims

1. A high-resilience foamed acrylic substrate, characterized in that, This includes acrylic oligomers, acrylate-modified resins, crosslinking agents, dynamically crosslinked resins, photoinitiators, and foaming agents.

2. The high resilience foamed acrylic substrate as described in claim 1, characterized in that, By weight, it includes 100 parts of acrylic oligomer, 5-30 parts of dynamic crosslinking resin, 1-3 parts of acrylate modified resin, 0.02-1 part of crosslinking agent, 0.1-2 parts of photoinitiator, 0-2 parts of inorganic pigment and 1-5 parts of foaming agent.

3. The high resilience foamed acrylic substrate as described in claim 2, characterized in that, By weight, it includes 100 parts of acrylic oligomer, 18 parts of dynamic crosslinking resin, 2 parts of acrylate modified resin, 0.5 parts of crosslinking agent, 1.5 parts of photoinitiator, 1 part of inorganic pigment and 3 parts of foaming agent.

4. The high resilience foamed acrylic substrate as described in any one of claims 2-3, characterized in that, The acrylic oligomer is a linear polymer formed by polymerizing various monofunctional acrylic monomers, including acrylic acid, isobornyl acrylate, isooctyl acrylate, isodecanyl acrylate, butyl acrylate, lauryl acrylate, (3,3,5)-trimethylcyclohexyl acrylate, stearic acid acrylate, and phenoxybenzyl acrylate; the crosslinking agent is an acrylate with bifunctional or multiple functional groups, including 1,4-butanediol acrylate, (3-ethoxy)bisphenol fluorene acrylate, and dipropylene glycol diacrylate. Acrylic esters, 1,6-hexanediol acrylate, polyethylene glycol (200) diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate; acrylate-modified resins are difunctional or multifunctional acrylate-modified resins with resilience, grafted or modified with epoxy resins, polyurethane resins, polyester resins and acrylic polymers, including any one or a mixture of two of epoxy acrylates, polyurethane acrylates, and polyester acrylates; the photoinitiator is 2,4,6-trimethylbenzoylbenzene. The inorganic pigment is any one or a mixture of at least two of the following: ethyl phosphonate, ethyl 4-dimethylaminobenzoate, 1-hydroxycyclohexylphenyl ketone, bis(2,6-difluoro-3-pyrrolephenyl)dicenoctane, and benzophenone; the inorganic pigment is any one or a mixture of at least two of the following: titanium dioxide, chrome yellow, iron blue, cadmium red, cadmium yellow, lithopone, carbon black, iron oxide red, and iron oxide yellow; the foaming agent is a microporous material with a plastic or rubber polymer as the matrix, which has been pre-heat-treated to contain a large number of air bubbles and does not require further foaming, including polyurethane foaming agents. Foaming agent, polystyrene foaming agent, polyolefin foaming agent, polyvinyl chloride foaming agent, phenolic foaming agent, epoxide resin foaming agent, nitrile rubber foaming agent, thermoplastic elastomer foaming agent, any one or a mixture of at least two of these; the dynamically crosslinked resin is a dynamically crosslinked acrylic resin containing disulfide bonds, a Diels-Alder thermally reversible resin based on furan / maleimide, UPy-modified polycaprolactone (PCL-U) prepolymer, UPy-modified polyurethane (PU-U) prepolymer, any one or a mixture of at least two of these.

5. A method for preparing a high-resilience foamed acrylic substrate as described in claim 4, characterized in that, Includes the following steps: S1. Premixing and degassing: The acrylic oligomer, dynamic crosslinking resin, acrylate modified resin, crosslinking agent, photoinitiator, inorganic pigment and foaming agent are thoroughly mechanically mixed under light-protected conditions, and then vacuum degassing is performed to obtain a uniform foamed acrylic substrate coating liquid. S2, Coating and Encapsulation: The coating liquid obtained in S1 is quantitatively coated onto the lower transparent release film, and then the upper transparent release film is covered. The coating thickness is controlled by roller pressing to form a "sandwich" structure. S3, UV curing and dynamic network activation: The material encapsulated in step S2 is placed in a UV curing device for irradiation and curing, which initiates the free radical polymerization of acrylic oligomers and the crosslinking reaction with the crosslinking agent to form the first static network. Subsequently, the cured material is heat-treated in an oven to activate the reversible bonds in the dynamic crosslinking resin, allowing them to fully participate in the construction of a second dynamic reversible network that runs through the static network. S4. Cooling and curing: Cool the heat-treated material to room temperature, cure it, and then peel off the release film to obtain the high-resilience and compression-resistant acrylic foam substrate.

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