High-strength structural adhesive for bonding automobile aluminum plate and preparation process thereof

Abstract

The application relates to the technical field of structural adhesive, and discloses high-strength structural adhesive for bonding automobile aluminum plates and a preparation process thereof, specifically: under the action of a free radical initiator, a free radical polymerization reaction is carried out between a methyl methacrylate functional group of an active end ether group siloxane-based block compound or an active end ether group phenyl siloxane-based block compound and an alkenyl functionalized nano silicon dioxide, so that an organic-inorganic hybrid toughening functional filler is prepared; a ring-opening reaction is carried out between a hydroxyl functional group in the organic-inorganic hybrid toughening functional filler and an epoxy functional group of a bisphenol A glycidyl ether type epoxy resin, so that a toughening type epoxy resin is prepared; the toughening type epoxy resin is used as a modified component of a bisphenol A glycidyl ether type epoxy resin matrix, so that the high-strength structural adhesive for bonding automobile aluminum plates is prepared; the structural adhesive product exhibits the characteristics of hardness and toughness after curing, and meets the performance requirements of structural adhesive for bonding inner and outer aluminum plates in a new energy automobile manufacturing process.

Description

Technical Field

[0001] This invention relates to the field of structural adhesive technology, specifically to a high-strength structural adhesive for bonding automotive aluminum panels and its preparation process. Background Technology

[0002] Structural adhesives, with their high strength, strong adhesion, and tear resistance, are an important and modern bonding bridge for materials such as metals, ceramics, plastics, concrete, wood, and glass, in addition to welding, riveting, and bolting. Epoxy resin, due to its excellent bonding strength, dimensional stability, chemical corrosion resistance, and electrical insulation properties, has become one of the most widely used and comprehensive structural adhesives, playing a dominant role in the new energy vehicle manufacturing field. For example, the most common combination for lightweighting of new energy vehicle body panels such as doors, hoods, and tailgates is an aluminum outer panel + aluminum inner panel. The process involves: after the inner and outer panels are stamped into shape using a mold, structural adhesive is applied to the joint flange of the inner panel; then, the edge of the outer panel is folded over to wrap around the inner panel using an edge-wrapping process. For areas requiring additional strength, self-piercing riveting or drilling screws are used for mechanical connection and fixation. Finally, the structural adhesive is cured by electrophoretic baking.

[0003] However, the highly cross-linked network structure formed after epoxy resin cures can also lead to high brittleness, poor flexibility, and insufficient fatigue and impact resistance of the material. When subjected to external impact or long-term vibration load, cracks are prone to propagate, affecting the service life and reliability of the bonded parts.

[0004] Based on this, the present invention aims to toughen and modify epoxy resin to give it both hard and tough properties. When used as a structural adhesive for bonding inner and outer aluminum plates in the manufacturing process of new energy vehicles, it can improve the service life and reliability of the bonded parts. Summary of the Invention

[0005] This invention develops a novel organic-inorganic hybrid toughening functional filler, which is introduced into the crosslinking network of epoxy resin through chemical bonding. The resulting epoxy resin exhibits hard and tough properties after curing, meeting the performance requirements of structural adhesives used for bonding inner and outer aluminum plates in the manufacturing process of new energy vehicles.

[0006] A high-strength structural adhesive for bonding automotive aluminum panels, the structural adhesive being composed of an epoxy resin component and a curing agent component;

[0007] The epoxy resin component comprises the following raw materials in parts by weight: 50-70 parts of bisphenol A glycidyl ether type epoxy resin, 30-40 parts of toughening type epoxy resin and 3-8 parts of diluent;

[0008] The formulation of the toughened epoxy resin is: 70-90wt% bisphenol A glycidyl ether type epoxy resin and 10-30wt% organic-inorganic hybrid toughening functional filler; the preparation method of the organic-inorganic hybrid toughening functional filler is: under the action of a free radical initiator, the alkenyl functional groups pre-modified on the surface of nano-silica undergo a free radical copolymerization reaction with block compounds containing alkenyl functional groups to achieve covalent grafting of polymer chains on the surface of nano-silica, thereby obtaining the organic-inorganic hybrid toughening functional filler;

[0009] Among them, the block compound is an active-terminal ether-siloxane block compound or an active-terminal ether-phenylsiloxane block compound;

[0010] The curing agent components include the following raw materials in parts by weight: 15-25 parts by weight of phenolic amine curing agent and 0.1-0.8 parts by weight of curing accelerator;

[0011] The mass ratio of epoxy resin component to curing agent component is (4.5-6):1.

[0012] Preferably, the formulation of the organic-inorganic hybrid toughening functional filler is: 0.5-2 parts by weight of vinyltrimethoxysilane, 3-8 parts by weight of nano-silica, 2-5 parts by weight of active-terminated ether-based siloxane block compound or 2-5 parts by weight of active-terminated ether-based phenylsiloxane block compound.

[0013] Preferably, the particle size of the nano-silica is 20-30 nm.

[0014] Preferably, the free radical initiator is one of dicumyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and tert-butyl peroxide.

[0015] The preparation process of high-strength structural adhesive for bonding automotive aluminum panels includes the following steps:

[0016] Step 1, Preparation of epoxy resin component: Mix the bisphenol A glycidyl ether type epoxy resin and toughened epoxy resin according to the formula, stir and mix evenly, then add the diluent according to the formula, stir and disperse evenly to obtain epoxy resin component.

[0017] Step 2, Preparation of curing agent components: Mix the curing agent and curing accelerator according to the formula, stir and mix evenly to obtain the curing agent components;

[0018] Step 3: Mix the epoxy resin component and the curing agent component evenly to obtain a high-strength structural adhesive for bonding automotive aluminum panels.

[0019] Preferably, the toughened epoxy resin is prepared by: utilizing the hydroxyl functional group in the organic-inorganic hybrid toughening functional filler to undergo a ring-opening reaction with the epoxy functional group of the bisphenol A glycidyl ether type epoxy resin to obtain the toughened epoxy resin.

[0020] Preferably, the preparation method of the active-terminated ether-terminated siloxane block compound is as follows:

[0021] Using pentaethylene glycol as a base material, an addition reaction is carried out between the hydroxyl functional group of 1 molar equivalent pentaethylene glycol and the isocyanate functional group of 0.90-0.95 molar equivalent isocyanate of methacrylate to generate an alkenyl-functionalized pentaethylene glycol monomer.

[0022] The intermediate Ma is generated by the addition reaction of the Si-H functional group of 1 molar equivalent of 1,1,3,3,5,5-hexamethyltrisiloxane with the alkenyl functional group of 0.90-0.95 molar equivalent of alkenyl-functionalized pentaethylene glycol monomer.

[0023] An addition reaction is carried out between the alkenyl functional group of 1 molar equivalent ethylene glycol dimethacrylate and the Si-H functional group of 0.90-0.95 molar equivalent intermediate Ma to generate an active-terminated ether-based siloxane block compound.

[0024] Preferably, the preparation method of the active-terminated ether-terminated phenylsiloxane block compound is as follows:

[0025] The intermediate Mb is generated by the addition reaction of the Si-H functional group of 1 molar equivalent of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane with the alkenyl functional group of 0.90-0.95 molar equivalent of the alkenyl-functionalized pentaethylene glycol monomer.

[0026] An addition reaction is carried out between the alkenyl functional group of 1 molar equivalent ethylene glycol dimethacrylate and the Si-H functional group of 0.90-0.95 molar equivalent intermediate Mb to generate an active-terminated ether-based phenylsiloxane block compound. Beneficial effects

[0027] Based on molecular design mechanisms, this invention synthesizes active-terminated ether-terminated siloxane block compounds and active-terminated ether-terminated phenylsiloxane block compounds.

[0028] Under the action of a free radical initiator, the methacrylate functional group of an active-terminated ether-based siloxane block compound or an active-terminated ether-based phenyl siloxane block compound undergoes a free radical polymerization reaction with alkenyl-functionalized nano-silica to obtain an organic-inorganic hybrid toughening functional filler.

[0029] Toughened epoxy resin is prepared by utilizing the ring-opening reaction between the hydroxyl functional group in the organic-inorganic hybrid toughening functional filler and the epoxy functional group of the bisphenol A glycidyl ether type epoxy resin.

[0030] A high-strength structural adhesive for bonding automotive aluminum panels was prepared by using toughened epoxy resin as a modifying component of bisphenol A glycidyl ether type epoxy resin matrix and adding diluent, curing agent and curing accelerator.

[0031] The experimental results show that the structural adhesive product prepared by this invention meets the performance index of room temperature tensile shear strength ≥30MPa and impact peel strength ≥30N / mm, that is, the product prepared by this invention belongs to hard and tough structural adhesive material. Attached Figure Description

[0032] Figure 1 The 1H NMR spectrum of the active-terminated ether-terminated siloxane block compound;

[0033] Figure 2 This is the 1H NMR spectrum of an active-terminated ether-terminated phenylsiloxane block compound. Detailed Implementation

[0034] Example 1:

[0035] The synthetic process for synthesizing active-terminated ether-terminated siloxane block compounds is as follows:

[0036] Process 1: Using pentaethylene glycol as the base material, an addition reaction is carried out between the hydroxyl functional group of 1 molar equivalent of pentaethylene glycol and the isocyanate functional group of 0.92 molar equivalent of isocyanate methacrylate to generate an alkenyl-functionalized pentaethylene glycol monomer, the chemical structural formula of which is as follows:

[0037] ;

[0038] Process 2: An addition reaction occurs between the Si-H functional group of 1 molar equivalent of 1,1,3,3,5,5-hexamethyltrisiloxane and the alkenyl functional group of 0.91 molar equivalent of an alkenyl-functionalized pentaethylene glycol monomer to generate intermediate Ma, whose chemical structural formula is as follows:

[0039] ;

[0040] Step 3: An addition reaction occurs between the alkenyl functional group of 1 molar equivalent of ethylene glycol dimethacrylate and the Si-H functional group of 0.92 molar equivalent of intermediate Ma, generating an active-terminated ether-terminated siloxane block compound with the following chemical structure:

[0041] ;

[0042] The specific experimental steps for synthesizing active-terminated ether-terminated siloxane block compounds are as follows:

[0043] Under nitrogen protection, 4.8 g of pentaethylene glycol, 2.9 g of isocyanate methacrylate and 60 mL of anhydrous N,N-dimethylformamide were added to a three-necked flask and stirred at room temperature for 30 min. The mixture was then heated to 70 °C and stirred for 6 h. After cooling to room temperature, the solvent was removed by rotary evaporation. Excess pentaethylene glycol was removed by washing with anhydrous chloroform and then dried under vacuum to obtain the alkenyl-functionalized pentaethylene glycol monomer.

[0044] Under nitrogen protection, 2.0 g of 1,1,3,3,5,5-hexamethyltrisiloxane and 20 mL of anhydrous N,N-dimethylformamide were added to a three-necked flask and stirred at room temperature until completely dissolved. Then, 30 mL of an alkenyl-functionalized pentaethylene glycol monomer solution (prepared from 4.0 g of alkenyl-functionalized pentaethylene glycol monomer and 30 mL of anhydrous N,N-dimethylformamide) and 5 drops of caster catalyst were added to the three-necked flask. The mixture was heated to 80 °C and stirred for 6 h. After cooling to room temperature, the solvent was removed by rotary evaporation. Excess 1,1,3,3,5,5-hexamethyltrisiloxane was removed by washing with anhydrous cyclohexane. The mixture was then dried under vacuum to obtain intermediate Ma.

[0045] Under nitrogen protection, 1.0 g of ethylene glycol dimethacrylate and 10 mL of anhydrous N,N-dimethylformamide were added to a three-necked flask and stirred at room temperature until completely dissolved. Then, 20 mL of intermediate Ma solution (prepared from 2.7 g of intermediate Ma and 30 mL of anhydrous N,N-dimethylformamide) and 5 drops of caster catalyst were added to the three-necked flask. The mixture was heated to 80 °C and stirred for 6 h. After cooling to room temperature, the solvent was removed by rotary evaporation. Excess ethylene glycol dimethacrylate was removed by washing with anhydrous chloroform. The mixture was then dried under vacuum to obtain an active-terminated ether-based siloxane block compound.

[0046] like Figure 1 As shown, the 1H NMR characterization of the active-terminated ether-terminated siloxane block compounds is as follows:

[0047] 1 H NMR (DMSO-d6, 400MHz) δ: 0.02 (s, 6H), 0.05 (s, 6H), 0.10 (s, 6H), 0.82-0.84 (d, 2H), 1.01-1.07 (m, 8H), 1.94 (s, 3H), 2.38-2. 46 (m, 2H), 3.37-3.43 (m, 2H), 3.55-3.70 (m, 18H), 4.24-4.36 (m, 9H), 5.63 (s, 2H), 5.85-5.89 (t, 1H).

[0048] Example 2:

[0049] The synthetic process for the active-terminated ether-terminated phenylsiloxane block compounds is as follows:

[0050] Process 1: An addition reaction occurs between the Si-H functional group of 1 molar equivalent of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and the alkenyl functional group of 0.91 molar equivalent of an alkenyl-functionalized pentaethylene glycol monomer to generate intermediate Mb, whose chemical structural formula is as follows:

[0051] ;

[0052] Process 2: An addition reaction occurs between the alkenyl functional group of 1 molar equivalent ethylene glycol dimethacrylate and the Si-H functional group of 0.92 molar equivalent intermediate Mb, generating an active-terminated ether-based phenylsiloxane block compound with the following chemical structure:

[0053] ;

[0054] The specific experimental steps for synthesizing active-terminated ether-based phenylsiloxane block compounds are as follows:

[0055] The specific experimental steps for preparing intermediate Mb differ from those for intermediate Ma only in that 3.3 g of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane is used instead of 2.0 g of 1,1,3,3,5,5-hexamethyltrisiloxane.

[0056] The specific experimental steps for preparing the active-terminated ether-based phenylsiloxane block compounds differ from those for the active-terminated ether-based siloxane block compounds only in that 3.4 g of intermediate Mb is used instead of 2.7 g of intermediate Ma.

[0057] like Figure 2 As shown, the 1H NMR characterization of the active-terminated ether-terminated phenylsiloxane block compound is as follows:

[0058] 1 H NMR (DMSO-d6, 400MHz) δ: 0.04 (s, 6H), 0.09 (s, 6H), 0.88-0.90 (d, 2H), 1.00-1.04 (m, 8H), 1.94 (s, 3H), 2.38-2.47 (m, 2H), 3.36- 3.42 (m, 2H), 3.57-3.70 (m, 18H), 4.22-4.35 (m, 9H), 5.65 (s, 2H), 5.85-5.89 (t, 1H), 7.27-7.47 (m, 10H).

[0059] Example 3:

[0060] Organic-inorganic hybrid toughening functional filler I was prepared with the following formulation: 1 part by weight of vinyltrimethoxysilane, 5 parts by weight of nano-silica, and 3 parts by weight of active-terminated ether-based siloxane block compound. The preparation steps are as follows:

[0061] Step 1: Preparation of alkenyl-functionalized nano-silica: The surface of nano-silica is modified using vinyltrimethoxysilane. The silanol functional groups obtained by the hydrolysis of the silanol functional groups of vinyltrimethoxysilane undergo a dehydration condensation reaction with the hydroxyl functional groups on the surface of the nano-silica to obtain alkenyl-functionalized nano-silica. The specific preparation steps are as follows: 5g of hydrophilic nano-silica (particle size 20-30nm), 20mL of deionized water, and 80mL of ethanol are added to a three-necked flask. The mixture is ultrasonically dispersed for 1h and stirred at room temperature for 2h. Then, 10mL of vinyltrimethoxysilane solution (prepared from 1g vinyltrimethoxysilane, 8mL ethanol, and 2mL deionized water) and two drops of glacial acetic acid are added dropwise to the three-necked flask. The mixture is heated to 60℃ and stirred for 4h. After cooling to room temperature, the mixture is centrifuged. The mixture is repeatedly washed and centrifuged with deionized water, and then vacuum dried at 50℃ for 8h to obtain alkenyl-functionalized nano-silica.

[0062] Step 2, preparation of organic-inorganic hybrid toughening functional filler I: Under the action of a free radical initiator, the alkenyl functional groups of the active-terminated ether-based siloxane block compound and the exposed alkenyl functional groups on the surface of alkenyl functionalized nano-silica undergo a free radical polymerization reaction to achieve the grafting modification treatment of nano-silica by the polymer chain of the active-terminated ether-based siloxane block compound, thus obtaining organic-inorganic hybrid toughening functional filler I. The specific preparation steps are as follows: Under nitrogen protection, 3g of the active-terminated ether-based siloxane block compound, the alkenyl functionalized nano-silica obtained in Step 1, 0.1g of tert-butyl peroxide and 50mL of anhydrous N,N-dimethylformamide are added to a three-necked flask, heated to 80℃ and stirred for 12h, cooled to room temperature, the solvent is removed by rotary evaporation, and vacuum dried at 60℃ for 12h to obtain organic-inorganic hybrid toughening functional filler I;

[0063] The free radical initiator can be selected from one of dicumyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and tert-butyl peroxide, and in this embodiment, tert-butyl peroxide is selected.

[0064] Example 4:

[0065] Organic-inorganic hybrid toughening functional filler II was prepared. Its formula was: 1 part by weight of vinyltrimethoxysilane, 5 parts by weight of nano-silica and 3 parts by weight of active-terminated ether-phenylsiloxane block compound. The only difference between its preparation steps and those of organic-inorganic hybrid toughening functional filler I was that the active-terminated ether-phenylsiloxane block compound was replaced with an active-terminated ether-phenylsiloxane block compound.

[0066] Example 5:

[0067] Toughened epoxy resin I was prepared with the following formulation: 80 wt% bisphenol A glycidyl ether type epoxy resin and 20 wt% organic-inorganic hybrid toughening functional filler I. The preparation method involved a ring-opening reaction between the hydroxyl functional groups in the organic-inorganic hybrid toughening functional filler I and the terminal epoxy functional groups on the main molecular chain of the bisphenol A glycidyl ether type epoxy resin, achieving effective composite of the organic-inorganic hybrid toughening functional filler I and the epoxy resin, thus obtaining toughened epoxy resin I. The specific preparation steps were as follows: 8.0 g of bisphenol A... Glycidyl ether type epoxy resin (model E51, epoxy value 0.51eq / 100g) and 100mL of anhydrous N,N-dimethylformamide were added to a three-necked flask. The mixture was heated to 60℃ and stirred until completely dissolved. Under nitrogen protection, 2.0g of organic-inorganic hybrid toughening functional filler I and 2.5mL of triethylamine catalyst were added to the three-necked flask in sequence. The mixture was heated to 80℃ and stirred for 5h. After cooling to room temperature, the solvent was removed by rotary evaporation. The mixture was then vacuum dried at 60℃ for 12h to obtain toughened epoxy resin I.

[0068] The epoxy value of toughened epoxy resin I was determined to be 0.48 eq / 100g according to the standard GB / T 1677-2018 "Determination of epoxy value of epoxy resin".

[0069] Example 6:

[0070] Toughened epoxy resin II was prepared with the following formulation: 80 wt% bisphenol A glycidyl ether type epoxy resin and 20 wt% organic-inorganic hybrid toughening functional filler II. The only difference between the preparation steps and those of toughened epoxy resin I is that organic-inorganic hybrid toughening functional filler I is replaced with organic-inorganic hybrid toughening functional filler II.

[0071] Example 7:

[0072] A high-strength structural adhesive for bonding automotive aluminum panels is composed of an epoxy resin component and a curing agent component; wherein, the formulation of the epoxy resin component is shown in Table 1, and the formulation of the curing agent component is shown in Table 2.

[0073]

[0074]

[0075] Among them, the toughened epoxy resin is either toughened epoxy resin I or toughened epoxy resin II.

[0076] Example 8:

[0077] A preparation process for a high-strength structural adhesive for bonding automotive aluminum panels includes the following steps:

[0078] Step 1, Preparation of epoxy resin component: According to the formula in Table 1, mix the bisphenol A glycidyl ether type epoxy resin and toughened epoxy resin in the formula amount, stir and mix at 500 r / min for 10 min, then add the diluent in the formula amount, and stir and disperse at 500 r / min for 20 min to obtain epoxy resin component.

[0079] Step 2, Preparation of curing agent components: According to the formula in Table 2, mix the curing agent and curing accelerator in the specified amounts, and stir at 100 r / min for 30 min to obtain the curing agent components;

[0080] Step 3: Mix the epoxy resin component and the curing agent component evenly at a mass ratio of 5:1 to obtain a high-strength structural adhesive for bonding automotive aluminum panels.

[0081] Among them, when the toughening epoxy resin is toughening epoxy resin I, the product obtained is denoted as high-strength structural adhesive I for bonding automotive aluminum panels.

[0082] When the toughening epoxy resin is toughening epoxy resin II, the resulting product is denoted as high-strength structural adhesive II for bonding automotive aluminum panels.

[0083] Performance testing:

[0084] 1. Place the structural adhesive sample in a vacuum drying oven to degas for 15 minutes, then pour it into a polytetrafluoroethylene mold coated with a release agent. After curing for 24 hours, demold and perform performance testing after 120 hours of curing, as detailed below:

[0085] (1) Mechanical property test: The mechanical properties of the structural adhesive samples were tested in accordance with GB / T 2567-2021 "Test Method for Performance of Resin Castings". The initial tensile strength, elongation at break (tensile speed of 2 mm / min) and impact toughness (size of 80 mm × 10 mm × 4 mm, no notch, pendulum of 5.5 J) were recorded.

[0086] (2) Weather resistance test: The structural adhesive sample was placed in room temperature water and soaked for 240 hours. After soaking, it was taken out and dried. Tensile test was carried out according to GB / T2567-2021 "Test Method for Performance of Resin Castings" standard. The tensile speed was 2 mm / min. The tensile strength of the sample was recorded. The change rate of tensile strength of the sample after soaking in room temperature water for 240 hours was calculated. The specific method is as follows:

[0087] Tensile strength change rate = (initial longitudinal tensile strength - tensile strength after soaking in water at room temperature for 240 hours) / initial longitudinal tensile strength × 100%;

[0088] (3) Aging resistance test: The structural adhesive sample was placed in a 60℃ constant temperature drying oven for 168h, then removed and placed at room temperature for 24h. Tensile test was performed according to GB / T 2567-2021 "Test Method for Performance of Resin Castings" standard, with a tensile speed of 2mm / min. The tensile strength of the sample was recorded, and the change rate of tensile strength of the sample after 168h treatment at 60℃ was calculated. The specific method is as follows:

[0089] Tensile strength change rate = (initial longitudinal tensile strength - tensile strength after treatment at 60℃ for 168h) / initial longitudinal tensile strength × 100%;

[0090] The results of the above performance experiments are shown in Table 3.

[0091]

[0092] Note: The only difference between the unmodified structural adhesive and the high-strength structural adhesive I for bonding automotive aluminum panels is that the unmodified structural adhesive does not use toughened epoxy resin I.

[0093] The following conclusions can be drawn from the analysis of the experimental results in Table 3:

[0094] Conclusion 1: This invention utilizes a self-developed toughened epoxy resin as a toughening and modifying component for a bisphenol A glycidyl ether type epoxy resin matrix. The structural adhesive product prepared thereby achieves significant improvements in elongation at break and impact toughness compared to conventional structural adhesives, and also has good tensile strength, thus realizing the technical goal of modifying structural adhesives to be both hard and tough.

[0095] Conclusion 2: The high-strength structural adhesive for bonding automotive aluminum panels prepared in this invention exhibits excellent weather resistance and aging resistance.

[0096] II. Using 5182 aluminum alloy plate as the test substrate, the surface of the aluminum alloy was polished with 800# silicon carbide sandpaper, and then degreased with n-heptane. After drying, the adhesive performance of the structural adhesive samples was tested, as follows:

[0097] (1) Tensile shear strength test: in accordance with GB / T The standard 7124-2008, "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)," tests structural adhesive samples. The specific test steps are as follows: Using vernier calipers, mark a 12.5mm overlap length (the overlap width is the width of the aluminum alloy plate, 25mm) on the side where two aluminum alloy plates (100mm×25mm×5mm) will be bonded. Then, use a stainless steel rod to evenly apply the structural adhesive sample to the overlap joint of one of the aluminum alloy plates. Place three copper wires in a triangular shape on the adhesive (the adhesive layer thickness is set to 0.2mm, and the thickness is controlled by three copper wires with a length of 0.5mm and a diameter of 0.2mm). Overlap the coated aluminum alloy plate and the uncoated aluminum alloy plate together with the 12.5mm mark line as the reference, and clamp them at both ends of the overlap joint with two clips. Remove excess adhesive, and after curing, test at a loading speed of 9.0MPa / min and record the tensile shear strength of the sample.

[0098] (2) Impact peel strength test: The structural adhesive sample was tested according to GB / T 36877-2018 "Determination of impact peel strength of structural adhesives by wedge method". The specific test steps are as follows: Use a vernier caliper to mark a bonding area with a length of 30mm and a width of 25mm on the side of the two aluminum alloy plates (100mm×25mm×5mm) to be bonded. Then, use a stainless steel rod to evenly apply the structural adhesive sample to the bonding area of ​​one of the aluminum alloy plates. Place three copper wires in a triangular shape on the adhesive (the adhesive layer thickness is set to 0.2mm, and three copper wires with a length of 0.5mm and a diameter of 0.2mm are used to control the adhesive layer thickness). The aluminum alloy plate with adhesive and the other aluminum alloy plate without adhesive are completely overlapped together and clamped at both ends of the bonding area with two clamps respectively. Remove the excess adhesive, and after curing, test at an impact speed of 2m / s and record the impact peel strength of the sample.

[0099] The results of the above performance experiments are shown in Table 4.

[0100]

[0101] Note: In the field of structural adhesives, at room temperature, when the tensile shear strength is ≥30MPa and the impact peel strength is ≥30N / mm, it is generally considered to have the characteristics of high strength and good toughness.

[0102] The following conclusions can be drawn from the analysis of the experimental results in Table 4:

[0103] The structural adhesive product prepared by this invention meets the performance index of room temperature tensile shear strength ≥30MPa and impact peel strength ≥30N / mm. Therefore, it can be seen that the product prepared by this invention belongs to hard and tough structural adhesive materials.

Claims

1. High-strength structural adhesive for bonding of automobile aluminum panels, characterized in that, The structural adhesive is composed of an epoxy resin component and a curing agent component; The epoxy resin component comprises the following raw materials in parts by weight: 50-70 parts of bisphenol A glycidyl ether type epoxy resin, 30-40 parts of toughening type epoxy resin and 3-8 parts of diluent; The toughening type epoxy resin has a formulation of 70-90 wt% of bisphenol A glycidyl ether type epoxy resin and 10-30 wt% of organic-inorganic hybrid toughening functional filler; The organic-inorganic hybrid toughening functional filler has a formulation of 0.5-2 parts by weight of vinyl trimethoxysilane, 3-8 parts by weight of nano-silica, 2-5 parts by weight of active end ether group siloxane-based block compound or 2-5 parts by weight of active end ether group phenyl siloxane-based block compound; The preparation method of the organic-inorganic hybrid toughening functional filler is that, under the action of a free radical initiator, the alkenyl functional groups pre-modified on the surface of nano-silica and the block compound containing alkenyl functional groups are subjected to free radical copolymerization reaction to realize covalent grafting of polymer chains on the surface of nano-silica, thereby obtaining the organic-inorganic hybrid toughening functional filler; The chemical structural formula of the active end ether group siloxane-based block compound is as follows: ； The chemical structural formula of the active end ether group phenyl siloxane-based block compound is as follows: ； The curing agent component comprises the following raw materials in parts by weight: 15-25 parts by weight of phenolic amine curing agent and 0.1-0.8 parts by weight of curing accelerator; The mass ratio of the epoxy resin component to the curing agent component is (4.5-6):

1.

2. The high-strength structural adhesive for bonding of automobile aluminum panels according to claim 1, characterized by The particle size of the nano-silica is 20-30 nm.

3. The high-strength structural adhesive for bonding of automobile aluminum panels according to claim 1, characterized in that, The free radical initiator is one of dicumyl peroxide, tert-butyl hydroperoxide, dibenzoyl peroxide and tert-butyl peroxybenzoate.

4. The process for preparing high-strength structural adhesive for bonding automobile aluminum plates according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: Step one, preparation of the epoxy resin component: mix the bisphenol A glycidyl ether type epoxy resin and the toughening type epoxy resin in the formulation amount, stir and mix uniformly, then add the diluent in the formulation amount, stir and disperse uniformly, and obtain the epoxy resin component; Step two, preparation of the curing agent component: mix the curing agent and the curing accelerator in the formulation amount, stir and mix uniformly, and obtain the curing agent component; Step three, mix the epoxy resin component and the curing agent component uniformly, and obtain the high-strength structural adhesive for bonding of automobile aluminum plates.

5. The process for preparing high-strength structural adhesive for bonding of automobile aluminum panels according to claim 4, characterized in that, The preparation method of the toughening type epoxy resin is that the hydroxyl functional groups in the organic-inorganic hybrid toughening functional filler and the epoxy functional groups of the bisphenol A glycidyl ether type epoxy resin are subjected to ring-opening reaction to obtain the toughening type epoxy resin.

6. The process for preparing high-strength structural adhesive for bonding of automobile aluminum plates according to claim 5, characterized in that, The preparation method of the active end ether group siloxane-based block compound is as follows: An alkenyl functionalized pentaethylene glycol monomer is generated through addition reaction of 1 mole equivalent of hydroxyl functional groups of pentaethylene glycol and 0.90-0.95 mole equivalent of isocyanate functional groups of isocyanatoethyl methacrylate; An intermediate Ma is generated through addition reaction of 1 mole equivalent of Si-H functional groups of 1,1,3,3,5,5-hexamethyltrisiloxane and 0.90-0.95 mole equivalent of alkenyl functional groups of the alkenyl functionalized pentaethylene glycol monomer; The active end ether group-containing phenyl siloxane-based block compound is prepared by addition reaction of 1 mole equivalent of the alkenyl functional group of the ethylene glycol dimethacrylate and 0.90-0.95 mole equivalent of the Si-H functional group of the intermediate Ma.

7. The process for preparing high-strength structural adhesive for bonding of automobile aluminum panels according to claim 6, characterized in that, The method for preparing the active end ether group-containing phenyl siloxane-based block compound is: The intermediate Mb is prepared by addition reaction of 1 mole equivalent of the Si-H functional group of 1,1,5,5-tetramethyl-3,3-diphenyl trisiloxane and 0.90-0.95 mole equivalent of the alkenyl functional group of the alkenyl-functionalized pentaethylene glycol monomer; The active end ether group-containing phenyl siloxane-based block compound is prepared by addition reaction of 1 mole equivalent of the alkenyl functional group of the ethylene glycol dimethacrylate and 0.90-0.95 mole equivalent of the Si-H functional group of the intermediate Mb.

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