Environment-friendly structural reinforcement adhesive material, preparation method and application thereof

Abstract

The application relates to the field of high polymer materials, in particular to an environment-friendly structure-reinforced adhesive material and a preparation method and application thereof. The environment-friendly structure-reinforced adhesive material comprises the following raw materials in parts by weight: modified bio-based epoxy resin 30-80 parts, bifunctional epoxy resin 20-50 parts, high-functionality epoxy resin 3-10 parts, diluent 1-5 parts, modified SiO2 nanoparticles 1-5 parts, filler 10-40 parts, thixotropic agent 1-3 parts and curing agent 2-25 parts; the modified bio-based epoxy resin is a bio-based epoxy resin modified by semi-bio-based core-shell rubber particles, and the semi-bio-based core-shell rubber particles are styrene-butadiene rubber@tannic acid nanoparticles. The adhesive material has the advantages of ultrahigh mechanical performance shear strength, excellent heat resistance and outstanding environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymer materials, in particular to an environment-friendly structural reinforcing adhesive material and a preparation method and application thereof. BACKGROUND

[0002] Epoxy structural reinforcing adhesive materials have a core connection role in the fields of aerospace, automobile manufacturing, and electronic packaging. Traditional epoxy adhesives are mainly derived from petroleum-based raw materials, which have problems such as non-renewability, high carbon footprint, and potential biological toxicity. The development of bio-based epoxy resin systems has become an industry trend.

[0003] However, the bio-based epoxy adhesives in the prior art still have significant defects. For example, patent CN118755427A discloses a bio-based epoxy adhesive, which has good corrosion resistance, but its mechanical properties are weaker than those of petroleum-based products, and it is brittle after curing and prone to cracking and failure in impact or bending environments. In addition, patent CN105176003A discloses a method for toughening epoxy resin using core-shell rubber particles, but the shell is mostly styrene or methyl methacrylate copolymer, which lacks functional groups on the surface, resulting in insufficient compatibility with bio-based epoxy resin and inability to participate in the curing reaction, limiting the toughening effect. At the same time, traditional toughening methods often sacrifice the strength and glass transition temperature (Tg) of the material.

[0004] Therefore, how to prepare a structural reinforcing adhesive material that maintains high strength and high heat resistance, has excellent toughness, and is environmentally friendly is a technical problem that needs to be solved in the field at present. SUMMARY

[0005] In order to improve the strength and heat resistance of the adhesive material while maintaining excellent toughness, the present application provides an environment-friendly structural reinforcing adhesive material and a preparation method and application thereof.

[0006] In a first aspect, the present application provides an environment-friendly structural reinforcing adhesive material, which adopts the following technical scheme:

[0007] An environment-friendly structural reinforcing adhesive material comprises the following raw materials by weight:

[0008] 30-80 parts of modified bio-based epoxy resin, 20-50 parts of bifunctional epoxy resin, 3-10 parts of high-functionality epoxy resin, 1-5 parts of diluent, 1-5 parts of modified SiO2 nanoparticles, 10-40 parts of filler, 1-3 parts of thixotropic agent, and 2-25 parts of curing agent.

[0009] The modified bio-based epoxy resin is a bio-based epoxy resin modified by semi-bio-based core-shell rubber particles, and the semi-bio-based core-shell rubber particles are styrene-butadiene rubber@tannic acid nanoparticles.

[0010] By adopting the technical scheme, a synergistic and environmentally friendly adhesive material system is constructed with modified bio-based epoxy resin as the core. By compounding modified bio-based epoxy resin, double-functionality and high-functionality epoxy resin in a specific ratio, the high proportion of bio-based raw materials is replaced while the main body mechanical properties and curing crosslinking density are ensured, and the environmental load and VOC emission of the material are significantly reduced. The introduction of modified SiO2 nanoparticles further improves the mechanical strength, thermal stability and anti-settling property of the material, so that the final product has excellent environmental friendliness, high strength, high heat resistance and good construction adaptability.

[0011] Further, the styrene-butadiene rubber@tannic acid nanoparticles have a core-shell structure, the inner core is a poly(butadiene-styrene-glycidyl methacrylate) crosslinked copolymer containing an epoxy group, and the outer shell is a tannic acid nanoparticle coated by chemical bonding.

[0012] By adopting the technical scheme, the "soft core-hard shell" structure is the key to realizing efficient toughening and strengthening of the material. The styrene-butadiene rubber phase of the inner core has excellent elasticity and can absorb and disperse impact energy through deformation and cavitation when stressed, effectively passivating crack propagation. The tannic acid nanoparticles of the outer shell are rich in rigid benzene ring structure and a large number of phenolic hydroxyl groups, which on the one hand compensate for the strength loss caused by toughening, and on the other hand the phenolic hydroxyl groups can form strong hydrogen bonds with the epoxy resin system and participate in the curing reaction to form a stable chemical bond (covalent bond) interface, thereby solving the problem of poor compatibility and weak interface bonding between traditional core-shell particles and resin matrix, realizing the effect of toughening without strength reduction, even synergistic reinforcement.

[0013] Further, the preparation method of the styrene-butadiene rubber@tannic acid nanoparticles is as follows:

[0014] 1) Preparation of tannic acid nanoparticles

[0015] Dissolve tannic acid in water, adjust the pH to neutral or weak alkaline, and react with ferric chloride solution to obtain a tannic acid colloidal solution;

[0016] 2) Preparation of styrene-butadiene rubber@tannic acid nanoparticles

[0017] Pre-emulsification and seed polymerization: the core layer monomer mixture containing butadiene, styrene, glycidyl methacrylate and crosslinking agent is pre-emulsified in the presence of emulsifier to form a core layer monomer pre-emulsion; water, emulsifier and pH buffer are added to the reaction kettle, heated under inert atmosphere and initiator is added, and the core layer monomer pre-emulsion is added dropwise for seed emulsion polymerization to obtain a poly(butadiene-styrene-glycidyl methacrylate) seed emulsion;

[0018] Tannin nanoparticle shell coating: adding a tertiary amine promoter to the seed emulsion, adding the tannin colloidal solution obtained in step 1) dropwise, heating the reaction, and allowing the tannin nanoparticles to react with the epoxy groups on the surface of the seed emulsion through phenolic hydroxyl groups to coat the surface of the rubber core, thereby obtaining a core-shell particle dispersion;

[0019] Post-processing: coagulation, washing, and drying to obtain styrene-butadiene rubber @ tannin nanoparticles

[0020] By using the above technical solution, the active reaction group (epoxy group) is ingeniously introduced to the surface of the rubber core. In the shell coating step, the phenolic hydroxyl groups on the tannin nanoparticles undergo ring-opening reaction with the epoxy groups on the surface of the rubber core to form stable chemical bonds, ensuring that the shell is firmly and uniformly coated on the core. This in-situ chemical bonding method avoids the problems of uneven coating and easy peeling caused by physical adsorption or simple mixing, and the prepared core-shell particles have clear structure and stable performance, laying a foundation for subsequent stable and efficient toughening effect in epoxy resin.

[0021] Further, in the core layer monomer mixture, the weight ratio of butadiene to styrene is (1-5): 1, and the amount of glycidyl methacrylate is 5-20% of the total weight of the core layer monomer mixture.

[0022] By using the above technical solution, precise control of the core layer monomer ratio is the core of regulating the performance of the core-shell particles. The ratio of butadiene to styrene directly determines the glass transition temperature and elastic modulus of the rubber phase of the core, which in turn affects its toughening efficiency. The amount of glycidyl methacrylate is directly related to the density of the available epoxy groups on the surface of the core. Controlling the amount of glycidyl methacrylate within this optimal range can ensure sufficient reaction sites for the full and firm bonding of the tannin shell, while avoiding the decrease in the elasticity of the core rubber due to excessive glycidyl methacrylate, thereby precisely balancing the toughening ability and interfacial reactivity of the core-shell particles.

[0023] Further, the preparation method of the modified bio-based epoxy resin is as follows: dispersing the styrene-butadiene rubber @ tannin nanoparticle in the bio-based epoxy resin, and uniformly mixing to obtain a bio-based epoxy resin, wherein the weight ratio of the styrene-butadiene rubber @ tannin nanoparticle to the bio-based epoxy resin is (5-15): 100.

[0024] By adopting the technical scheme, the pre-modification process uniformly disperses the toughening unit (core-shell particles) in the bio-based epoxy resin in advance and stably exists in the bio-based epoxy resin, forming a functionalized prepolymer. This helps to solve the problems of uneven dispersion and sedimentation of the core-shell particles in the final complex formula system due to differences in density and polarity. Pre-dispersion ensures uniform distribution of the core-shell particles in the final cured product, enabling the toughening and reinforcing effect of the core-shell particles to be stable and fully exerted, while simplifying the preparation process of the final adhesive material and improving the consistency and reliability of the product.

[0025] Further, the bio-based epoxy resin is one or more of epoxy soybean oil, cashew phenol glycidyl ether, and cashew phenol-based diphenyl epoxy resin;

[0026] The dual-functionality epoxy resin is one or more of bisphenol A type epoxy resin, furan epoxy resin, polyphenol type glycidyl ether epoxy resin, bisphenol F type epoxy resin, glycidyl ester type epoxy resin, and heterocyclic glycidyl epoxy resin.

[0027] The high-functionality epoxy resin is one or more of 4,4-diaminodiphenyl methane tetraglycidyl amine and trimethylolpropane triglycidyl ether.

[0028] By adopting the technical scheme, the specific types of various resin components are optimized and limited. The selected bio-based epoxy resin is renewable, environmentally friendly, and partially has flexible segments, which helps to improve the toughness of the system. The dual-functionality epoxy resin provides a basic mechanical skeleton and curing network. The introduction of high-functionality epoxy resin can significantly increase the crosslinking density of the cured product, thereby effectively improving the glass transition temperature, heat resistance, and overall mechanical strength of the material, compensating for the loss of heat resistance due to the introduction of flexible bio-based components and toughening particles, and ensuring the use performance of the material in high temperature environment.

[0029] Further, the modified SiO2 nanoparticles are any one of epoxy-modified SiO2 nanoparticles and amino-modified SiO2 nanoparticles.

[0030] By adopting the technical scheme, the SiO2 nanoparticles with surface modified by epoxy group or amino group are selected, and the surface functional groups can chemically react with the epoxy resin matrix, enhancing the interfacial bonding force between the nanoparticles and the resin. This not only more effectively plays the role of the nanoparticles in enhancing and toughening, but also improves the dispersion stability of the nanoparticles in the resin, preventing agglomeration, thereby more comprehensively improving the mechanical properties, thermal stability, and durability of the composite material.

[0031] Further, it also includes 2-6 parts of a foaming agent and 0.5-3 parts of a foaming aid.

[0032] By adopting the technical scheme, the foaming system is introduced, so that the material can form a uniform microporous structure controllably in the curing process, thereby preparing a foaming type structure reinforced adhesive material with light weight. The material has significantly reduced density while maintaining sufficient adhesive strength, better filling, sound insulation and heat insulation performance, and lower material consumption, thereby expanding its application range in application scenarios requiring light weight, filling gaps or having damping requirements.

[0033] Further, the diluent is one or more of diglycidyl ether, polyglycidyl ether, alkyl glycidyl ether, butyl glycidyl ether, and allyl glycidyl ether.

[0034] Further, the filler is one or more of calcium carbonate, calcium oxide, wollastonite, mica powder, carbon black, clay, barite, quartz powder, talc powder, and glass microbeads.

[0035] Further, the coupling agent is one or more of vinyl silane, amino silane, epoxy silane, mercapto silane, and methacryloyloxy silane.

[0036] Further, the thixotropic agent is one or more of fumed silica, organic bentonite, hydrogenated castor oil, and polyamide wax.

[0037] Further, the foaming agent is one or more of azodicarbonamide, azobisisobutyronitrile, dibenzoyl peroxide, urea and urea derivatives, and expanded microsphere foaming agent.

[0038] Further, the foaming aid is one or more of zinc oxide, zinc stearate, and cobalt isooctanoate.

[0039] In a second aspect, the application provides a preparation method of the environmentally friendly structure reinforced adhesive material, which adopts the following technical scheme:

[0040] A preparation method of an environmentally friendly structure reinforced adhesive material includes the following steps:

[0041] The modified bio-based epoxy resin, the difunctional epoxy resin, the high-functionality epoxy resin, and the diluent are mixed uniformly, and then the modified SiO2 nanoparticles, the filler, the curing agent, the thixotropic agent, and the optional foaming agent and foaming aid are added and uniformly dispersed by vacuum stirring.

[0042] By adopting the above technical solution, the preparation method has clear process steps, is simple to operate, and has excellent repeatability and industrialization potential. It employs a step-by-step mixing sequence: first, the resin matrix and reactive diluent are mixed to form a homogeneous liquid phase, which is beneficial for the wetting and dispersion of subsequent solid components; then, fillers, curing agents, and other solid components are added and vacuum high-speed stirring is performed, which effectively avoids the introduction of air bubbles and ensures that all components, especially nanoscale modified SiO2 and core-shell particles, are uniformly dispersed in the system. This process is a key guarantee for obtaining high-quality, environmentally friendly structurally reinforced adhesives with stable and uniform performance.

[0043] Thirdly, this application provides an application of an environmentally friendly structural reinforcement adhesive material, employing the following technical solution:

[0044] An environmentally friendly structural reinforcement adhesive material is applied in the fields of automobile manufacturing, electronic packaging, and building reinforcement.

[0045] By adopting the above technical solutions, the adhesive material provided in this application, with its excellent comprehensive performance, high strength, high toughness, high heat resistance and green environmental protection characteristics, can fully meet the needs of automobile manufacturing for lightweight and high impact-resistant bonding materials, the requirements of electronic packaging for precision, reliability, low stress and heat-resistant adhesive materials, and the needs of building reinforcement for durable, high-strength, adaptable and environmentally friendly structural adhesives.

[0046] In summary, this application has the following beneficial effects:

[0047] The environmentally friendly structural reinforcement adhesive material provided in this application, through the innovative use of semi-biological core-shell rubber particle modification technology, has successfully prepared a new type of material that possesses ultra-high mechanical properties (shear strength >24 MPa), excellent heat resistance (Tg >110℃), outstanding environmental performance, and good designability. Its comprehensive performance not only fully meets the requirements of high-end structural bonding but also fundamentally surpasses traditional petroleum-based products in terms of environmental protection indicators. Attached Figure Description

[0048] Figure 1 Photograph of the modified bio-based epoxy resin prepared for this application (Example 1). Detailed Implementation

[0049] The present application will be further described in detail below with reference to the embodiments.

[0050] Example of raw material and intermediate preparation

[0051] raw material

[0052] It should be noted that: in the following examples, unless otherwise specified, the conditions shall be in accordance with conventional conditions or the manufacturer's recommended conditions; and the raw materials used in the following examples, unless otherwise specified, shall be from commercially available sources.

[0053] Epoxy resins:

[0054] Epoxidized soybean oil: B-22D (200), epoxy value ≥ 6.0%, technical grade;

[0055] Bisphenol A epoxy resin (type 128): epoxy equivalent weight 184-190 g / eq, technical grade;

[0056] Epoxy value 0.18-0.22 mol / 100 g, technical grade;

[0057] Cardanol glycidyl ether: epoxy value 0.45-0.50 mol / 100 g, technical grade;

[0058] 4,4-Diaminodiphenylmethane tetraglycidyl amine: epoxy value 0.70-0.75 mol / 100 g, technical grade;

[0059] Diglycidyl ether: epoxy value ≥ 0.85 mol / 100 g, chemically pure;

[0060] Core-shell particle preparation raw materials:

[0061] Tannic acid: purity ≥ 98%, chemically pure;

[0062] Styrene-butadiene rubber: grade type 1502, purchased from Xianghe International Trade Development (Tianjin) Co., Ltd.;

[0063] Iron trichloride (FeCl3·6H2O): purity ≥ 99%, chemically pure;

[0064] Butadiene: polymerization grade, purity ≥ 99.5%;

[0065] Styrene: polymerization grade, purity ≥ 99%, distilled under reduced pressure to remove the polymerization inhibitor before use;

[0066] Glycidyl methacrylate: purity ≥ 97%, chemically pure;

[0067] Divinylbenzene: purity ≥ 55% (the rest is ethylvinylbenzene), technical grade;

[0068] Emulsifiers, initiators and auxiliaries:

[0069] Dodecylbenzenesulfonic acid: technical grade;

[0070] Sodium dodecylbenzenesulfonate: technical grade;

[0071] Sorbitan fatty acid ester (Span 80): chemically pure;

[0072] Potassium persulfate: analytical pure;

[0073] Sodium persulfate: analytical pure;

[0074] Sodium carbonate: analytical pure;

[0075] Triethylamine: purity ≥ 99%, chemically pure;

[0076] N,N-dimethylaniline: chemically pure;

[0077] Sodium hydroxide: analytical pure;

[0078] Fillers, curing agents and other auxiliaries:

[0079] Dicyandiamide: average particle size ≤ 5 μm, technical grade;

[0080] Substituted urea accelerators (UR500): technical grade;

[0081] Wollastonite powder: particle size 800-1250 mesh, technical grade;

[0082] Fumed silica: specific surface area 200 ± 25 m² / g, technical grade;

[0083] Epoxy-modified SiO2 nanoparticles: particle size 20-30 nm, SiO2 surface epoxy group content ≥ 0.5 mmol / g;

[0084] Azodicarbonamide (AC blowing agent): decomposition temperature 200-210°C, technical grade;

[0085] N-type urea-stearic acid complex: technical grade;

[0086] Zinc oxide: active zinc oxide, technical grade;

[0087] Solvents:

[0088] Anhydrous ethanol: analytical pure.

[0089] Preparation Example

[0090] Preparation Example 1

[0091] A modified bio-based epoxy resin, the method for preparing the same is:

[0092] S1. Preparation of butadiene-styrene rubber @ tannic acid nanoparticles

[0093] 1) Preparation of tannic acid nanoparticles

[0094] Tannic acid solution was prepared by dissolving 0.1 kg of tannic acid in 100 kg of deionized water, and then adjusting the pH value to 7.1 with NaOH solution; ferric chloride solution was prepared by dissolving 0.01 kg of ferric chloride in deionized water and adjusting the pH value to 7.1; the tannic acid solution was slowly poured into the ferric chloride solution, and a magnetic stirrer was started at the same time, with a speed of 600 rpm; the dropping was completed in 50 min, and the stirring was continued at room temperature for 30 min in the dark; the reaction obtained a tannic acid colloidal solution;

[0095] 2) Preparation of styrene-butadiene rubber@tannic acid nanoparticles

[0096] Pre-emulsification and seed polymerization: 5.64 kg of butadiene, 3.76 kg of styrene, 0.5 kg of glycidyl methacrylate, and 0.1 kg of crosslinking agent divinylbenzene were mixed uniformly as the core layer monomer mixture; 1 kg of dodecylbenzenesulfonic acid was added to 100 kg of deionized water, and then the above core layer monomer mixture was added under stirring at a speed of 600 rpm, and pre-emulsification was carried out for 30 min to form a core layer monomer pre-emulsion; 20 kg of deionized water, 0.1 kg of dodecylbenzenesulfonic acid emulsifier, and 0.1 kg of sodium carbonate pH buffer were added to the reaction kettle, nitrogen was used to replace oxygen three times, the temperature was raised to 65°C, and 0.1 kg of potassium persulfate was added to initiate polymerization. Then the core layer monomer pre-emulsion was slowly added, and the dropping speed was controlled to be completed within 3 hours. After the addition was completed, the temperature was raised to 75°C, and the reaction was carried out for 3 hours to obtain a poly(butadiene-styrene-glycidyl methacrylate) seed emulsion;

[0097] Tannic acid nanoparticle shell coating: 0.01 kg of triethylamine was added to the seed emulsion, and the tannic acid colloidal solution obtained in step 1) was slowly added, and the dropping was completed in 30 min, while a magnetic stirrer was started at a speed of 500 rpm, and the water bath was heated to 85°C, and the reaction was carried out for 3 hours to coat the rubber core surface, to obtain a core-shell particle dispersion;

[0098] Post-treatment: 10 L of ethanol solution was added to the above core-shell particle dispersion, and the core-shell particles were allowed to coagulate and precipitate under stirring, and centrifuged, and washed with deionized water and ethanol three times to remove emulsifiers and impurities. The washed solid was dried at 40°C under vacuum for 48 hours to obtain styrene-butadiene rubber@tannic acid nanoparticles, and the average particle size of the styrene-butadiene rubber@tannic acid nanoparticles was 194 nm;

[0099] S2. Preparation of modified bio-based epoxy resin

[0100] 100 kg of epoxy soybean oil was heated to 60°C, 5 kg of styrene-butadiene rubber @ tannic acid nanoparticles (5% ethanol dispersion was added in advance) was slowly added, and the stirring speed was 250 rpm. The stirring time was 1 hour, and the modified bio-based epoxy resin was obtained. The obtained modified bio-based epoxy resin is shown in Figure 1

[0101] Preparation Example 2

[0102] Different from Preparation Example 1, in Preparation Example 2, the amount of tannic acid in S1 1) was 0.5 kg, the amount of ferric chloride was 0.07 kg, the stirring speed was 800 rpm, the stirring time was 2 hours, and the average particle size of the styrene-butadiene rubber @ tannic acid nanoparticles was 330 nm.

[0103] Preparation Example 3

[0104] Different from Preparation Example 2, in Preparation Example 3, the total amount of the core layer monomer mixture was 30 kg, the weight ratio of butadiene to styrene was 4:1, the amount of glycidyl methacrylate was 15 kg, and the amount of divinylbenzene was 0.2 kg; In the pre-emulsification stage, 5 kg of sodium dodecylbenzenesulfonate was used as an emulsifier; In the polymerization stage, 50 kg of deionized water, 2 kg of sodium dodecylbenzenesulfonate emulsifier and 0.5 kg of sodium carbonate pH buffer were added to the reaction kettle, and the oxygen was replaced with nitrogen three times. The average particle size of the styrene-butadiene rubber @ tannic acid nanoparticles was 334 nm.

[0105] Preparation Example 4

[0106] Different from Preparation Example 3, in Preparation Example 4, the amount of styrene-butadiene rubber @ tannic acid nanoparticles in S2 was 15 kg, and the emulsifier was sorbitan fatty acid ester.

[0107] Preparation Example 5

[0108] Different from Preparation Example 4, in Preparation Example 5, S2. Modified bio-based epoxy resin preparation: 60 kg of epoxy soybean oil and 40 kg of cardanol glycidyl ether were heated to 60°C, 15 kg of styrene-butadiene rubber @ tannic acid nanoparticles (5% ethanol dispersion was added in advance) was slowly added, and the stirring speed was 250 rpm. The stirring time was 1 hour, and the modified bio-based epoxy resin was obtained.

[0109] Preparation Example 6

[0110] Different from Preparation Example 5, in Preparation Example 6, the bio-based epoxy resin was 80 kg of epoxy soybean oil and 20 kg of cardanol glycidyl ether.

[0111] Example

[0112] Examples 1-3 ​

[0113] An environmentally friendly structural reinforcement adhesive material, and a preparation method thereof is provided.

[0114] In a premixing container, the modified bio-based cyclic resin, the difunctional epoxy resin, the high-functionality epoxy resin, and the diluent were sequentially added and stirred at a speed of 500 rpm for 10 minutes. Then the remaining raw materials were added, the stirring speed was increased to 700 rpm, and the mixture was degassed under vacuum high-speed stirring for 20 minutes until it was uniform and fine without visible powder lumps.

[0115] Table 1. Raw material ratio table of Examples 1-3 / kg

[0116]

[0117] The modified bio-based epoxy resin in Example 1 was from Preparation Example 1, the difunctional epoxy resin in Example 1 was 20 kg of bisphenol A epoxy resin 128 and 5 kg of E20 solid epoxy resin, and the difunctional epoxy resin in Examples 2-3 was 10 kg of bisphenol A epoxy resin 128 and 35 kg of E20 solid epoxy resin; the high-functionality epoxy resin was 4,4-diaminodiphenylmethane tetraglycidyl amine; the diluent was diglycidyl ether; the modified SiO2 nanoparticles were epoxy-modified SiO2 nanoparticles; the filler was wollastonite; the curing agent was dicyandiamide; the thixotropic agent was fumed silica; the foaming agent was azodicarbonamide; the foaming aid was zinc oxide; the low-temperature accelerator was a substituted urea accelerator UR500; and the other foaming aid was an N-type urea-stearic acid complex.

[0118] Examples 4-6

[0119] Different from Example 1, the modified bio-based epoxy resin in Examples 4-6 was from Preparation Examples 2-4, respectively.

[0120] Examples 7-8

[0121] Different from Example 2, the modified bio-based epoxy resin in Examples 7-8 was from Preparation Examples 5-6, respectively.

[0122] Comparative Examples

[0123] Comparative Example 1

[0124] Different from Example 1, in Comparative Example 1, an equal amount of bisphenol A epoxy resin 128 was used to replace the modified bio-based epoxy resin, i.e., no modified bio-based epoxy resin was contained in Comparative Example 1, and the bisphenol A epoxy resin 128 was 90 kg.

[0125] Comparative Example 2

[0126] Different from Example 2, the modified bio-based epoxy resin in Comparative Example 2 was replaced with an equal amount of bisphenol A epoxy resin 128, i.e. no modified bio-based epoxy resin was contained in Comparative Example 2, and the bisphenol A epoxy resin 128 was 60 kg.

[0127] Comparative Example 3

[0128] Different from Example 1, the core-shell particles in the modified bio-based epoxy resin used in Comparative Example 3 were “styrene-butadiene rubber@PMMA nanoparticles”, which were prepared as follows:

[0129] S1. Preparation of styrene-butadiene rubber@PMMA nanoparticles

[0130] 1) Pre-emulsification and seed polymerization: the procedure was the same as the corresponding part in S1 of Preparation Example 1, and a poly(butadiene-styrene-glycidyl methacrylate) seed emulsion was obtained;

[0131] 2) PMMA shell coating: 0.01 kg of triethylamine was added to the above seed emulsion, and then a mixed solution composed of 5 kg of methyl methacrylate monomer, 0.05 kg of azobisisobutyronitrile and 10 kg of deionized water was added dropwise, while a magnetic stirrer was started at a speed of 500 rpm, and water bath heating was carried out at 85°C for 3 hours, to obtain a core-shell particle dispersion;

[0132] 3) Post-treatment: the same as Preparation Example 1, to obtain styrene-butadiene rubber@PMMA nanoparticles;

[0133] S2. Preparation of modified bio-based epoxy resin: the same as the S2 step of Preparation Example 1, and the above styrene-butadiene rubber@PMMA nanoparticles were used instead of the styrene-butadiene rubber@tannin nanoparticles;

[0134] According to the formulation and preparation method of Example 1, the modified bio-based epoxy resin in Example 1 was replaced with the above modified bio-based epoxy resin, to prepare a comparative adhesive material.

[0135] Performance testing

[0136] Tensile shear samples were prepared according to GB / T 7124-2008 for testing shear strength; the sample expansion ratio was tested according to GJB 1480A-2013; the glass transition temperature (Tg) of the cured glue block was tested by DSC; the content of volatile organic compounds (VOC) was detected according to EPA Method 24, and the test results are shown in Tables 2 and 3.

[0137] Table 2: Mechanical property test results

[0138]

[0139] Table 3: VOC test results

[0140]

[0141] Note: N.D. = Not detected (less than the detection limit of 0.25 μg)

[0142] Mechanical strength and heat resistance are the core indicators of structural adhesive materials. Comparative Example 1 uses a pure petroleum-based epoxy resin system, with a shear strength of 22.21 MPa and a glass transition temperature (Tg) of 105°C, representing the typical level of traditional high-performance structural adhesives. Example 1, as the base formula of the present application, uses a large amount of bio-based epoxy resin, with a shear strength (16.30 MPa) and Tg (68°C) initially lower than Comparative Example 1, which objectively reflects the challenges faced when replacing part of the rigid petroleum-based component with a flexible bio-based component, while also highlighting its environmental advantage of zero VOC.

[0143] However, by introducing and optimizing the core semi-bio-based core-shell rubber particles of the present application, the material performance has achieved a significant leap. After adjusting the structure of the core-shell particles, Example 4 has significantly improved to 18.91 MPa and 80°C. Example 5 and Example 6 further exhibit breakthrough effects, with shear strengths of 23.22 MPa and 24.72 MPa, respectively, and Tgs of 99°C and 111°C, respectively. The strength and heat resistance of Example 6 have both surpassed the traditional petroleum-based benchmark (Comparative Example 1). This series of data powerfully proves that the "soft core-hard shell" structure particles designed in the present application not only effectively solve the problem of insufficient intrinsic strength and modulus of bio-based epoxy systems, but also achieve the synergistic improvement of toughening, strengthening, and heat resistance, breaking through the traditional technical bottleneck of "toughening at the expense of strength and heat resistance".

[0144] The shear strength and glass transition temperature of Comparative Example 3 are significantly lower than those of Example 1, and much lower than those of Example 4. This result clearly shows that only having a core-shell structure, but lacking reactive functional groups in the shell, not only fails to achieve strengthening effect, but also may become a performance shortcoming due to weak interfacial bonding. Specifically, in Comparative Example 3, the PMMA shell is inert, and only physical wrapping and weak polar interaction exist between the epoxy resin matrix, which cannot form a stable chemical bonding interface. When stressed, the interface is prone to become a stress concentration point and defect source, resulting in poor strength and heat resistance. On the other hand, the tannin nanoparticle shell is rich in phenolic hydroxyl groups, which not only directly contributes to the strengthening effect due to its rigid benzene ring structure, but also forms strong hydrogen bonds with epoxy groups and participates in the curing reaction, building a firm chemical bonding interface between the particles and the resin matrix. This interface not only effectively transmits stress, but also prevents crack propagation, thereby achieving the breakthrough effect of "toughening without reducing strength, and synergistically improving heat resistance".

[0145] The environmental protection is another important demand of the present application. The VOC test results provide strong evidence: all of the comparative example 1 and comparative example 2 samples are clearly detected acetaldehyde and considerable TVOC. In sharp contrast, in the VOC test results of all examples of the present application, various harmful substances such as benzene, toluene, acetaldehyde, etc. are "not detected", and TVOC is zero. This directly proves that the use of bio-based raw materials and the specific structure system of the present application can fundamentally eliminate the release of small molecule harmful substances and meet the stringent environmental protection and health standards.

[0146] To show the universality of the present application technology, the examples further explore the foaming type material. The comparison between example 2 and comparative example 2 realizes higher shear strength and Tg while achieving similar expansion ratio. This shows that the present application material can still maintain excellent comprehensive performance in lightweight and filling applications. In addition, examples 7 and 8 further improve the Tg to 112℃ and 90℃ by adjusting the types of bio-based epoxy resins while maintaining good foaming effect and strength, which reflects the ability to flexibly control the final performance through formula fine-tuning, and meets the needs of diversified application scenarios.

[0147] The specific embodiments are only an explanation of the present application, which is not a limitation of the present application. Those skilled in the art can make modifications to the present embodiments without creative contribution after reading the present specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. An environmentally friendly structural reinforcement adhesive material, characterized in that, Including the following parts by weight of raw materials: 30-80 parts of modified bio-based epoxy resin, 20-50 parts of bifunctional epoxy resin, 3-10 parts of high-functionality epoxy resin, 1-5 parts of diluent, 1-5 parts of modified SiO2 nanoparticles, 10-40 parts of filler, 1-3 parts of thixotropic agent, and 2-25 parts of curing agent. The modified bio-based epoxy resin is a bio-based epoxy resin modified with semi-bio-based core-shell rubber particles, wherein the semi-bio-based core-shell rubber particles are styrene-butadiene rubber@tannic acid nanoparticles. The styrene-butadiene rubber@tannic acid nanoparticles have a core-shell structure, with the core being a cross-linked copolymer of poly(butadiene-styrene-glycidyl methacrylate) containing epoxy groups, and the outer shell being tannic acid nanoparticles coated by chemical bonding. The preparation method of the styrene-butadiene rubber@tannic acid nanoparticles is as follows: 1) Preparation of tannic acid nanoparticles Tannic acid is dissolved in water, the pH is adjusted to neutral or weakly alkaline, and then reacted with ferric chloride solution to obtain a tannic acid colloidal solution. 2) Preparation of styrene-butadiene rubber@tannic acid nanoparticles Pre-emulsification and seed polymerization: A mixture of core layer monomers containing butadiene, styrene, glycidyl methacrylate and crosslinking agent is pre-emulsified in the presence of an emulsifier to form a core layer monomer pre-emulsion; water, emulsifier and pH buffer are added to a reactor, and the mixture is heated under an inert atmosphere while an initiator is added. Seed emulsion polymerization is carried out by dropwise addition of the core layer monomer pre-emulsion to obtain poly(butadiene-styrene-glycidyl methacrylate) seed emulsion; Tannic acid nanoparticle shell coating: Add a tertiary amine promoter to the seed emulsion, add the tannic acid colloidal solution obtained in step 1), heat the reaction, so that the tannic acid nanoparticles react with the epoxy groups on the surface of the seed emulsion through the phenolic hydroxyl groups and coat the rubber core surface to obtain a core-shell particle dispersion. Post-processing: coagulation, washing, and drying to obtain styrene-butadiene rubber@tannic acid nanoparticles; In the core layer monomer mixture, the weight ratio of butadiene to styrene is (1-5):1, and the amount of glycidyl methacrylate is 5-20% of the total weight of the core layer monomer mixture; The modified SiO2 nanoparticles are either epoxy-modified SiO2 nanoparticles or amino-modified SiO2 nanoparticles.

2. The environmentally friendly structural reinforcement adhesive material according to claim 1, characterized in that, The modified bio-based epoxy resin is prepared by dispersing styrene-butadiene rubber@tannic acid nanoparticles in bio-based epoxy resin and mixing them evenly. The weight ratio of styrene-butadiene rubber@tannic acid nanoparticles to bio-based epoxy resin is (5-15):

100.

3. The environmentally friendly structural reinforcement adhesive material according to claim 1, characterized in that, The bio-based epoxy resin is one or more of epoxidized soybean oil, cashew phenol glycidyl ether and cashew phenol diphenyl diepoxy resin. The bifunctional epoxy resin is one or more of the following: bisphenol A type epoxy resin, furan epoxy resin, polyphenol type glycidyl ether epoxy resin, bisphenol F type epoxy resin, glycidyl ester type epoxy resin, and heterocyclic type glycidyl epoxy resin. The high-functionality epoxy resin is one or more of 4,4-diaminodiphenylmethane tetraglycidylamine and trimethylolpropane triglycidyl ether.

4. The environmentally friendly structural reinforcement adhesive material according to claim 1, characterized in that, It also includes 2-6 parts of foaming agent and 0.5-3 parts of foaming aid.

5. A method for preparing an environmentally friendly structurally reinforced adhesive material as described in any one of claims 1-4, characterized in that, Includes the following steps: The modified bio-based epoxy resin, bifunctional epoxy resin, high-functionality epoxy resin, and diluent are mixed evenly, and then modified SiO2 nanoparticles, fillers, curing agents, thixotropic agents, and optional foaming agents and foaming aids are added and dispersed evenly under vacuum stirring.

6. An application of the environmentally friendly structural reinforcement adhesive material as described in any one of claims 1-4, characterized in that, It is used in automobile manufacturing, electronic packaging, and building reinforcement.

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