An ultrahigh expansion welding glue and a preparation process thereof

Abstract

This invention relates to the field of welding adhesive materials, specifically disclosing an ultra-high expansion welding adhesive and its preparation process. The ultra-high expansion welding adhesive comprises the following raw materials: ethylene propylene diene monomer (EPDM) rubber, functionalized thermally expandable microspheres, modified aramid fibers, composite amide wax, calcium carbonate, paraffin oil, azodicarbonamide, and peroxide; the peroxide is a mixture of DCP and BIPB. The preparation process includes: first, internally mixing EPDM rubber with composite amide wax, paraffin oil, and calcium carbonate to obtain a masterbatch; then, open-milling the masterbatch with functionalized thermally expandable microspheres, modified aramid fibers, azodicarbonamide, and peroxide to obtain a compound; finally, calendering, cooling, and cutting to obtain the ultra-high expansion welding adhesive. The ultra-high expansion welding adhesive obtained by this invention can improve the expansion ratio, cell structure stability, and support performance after foaming, and is suitable for filling, sealing, and reinforcing automotive welding parts.

Description

Technical Field

[0001] This invention relates to the field of welding adhesive materials technology, and more specifically, to an ultra-high expansion welding adhesive and its preparation process. Background Technology

[0002] Welding adhesives are widely used in automotive body welding areas to fill gaps, seal, sound insulation, and provide localized reinforcement during welding, electrophoresis, and baking processes. Existing welding adhesives are typically prepared with rubber or resin as a base, combined with foaming agents, fillers, and additives. They expand under subsequent heating conditions, thereby filling and sealing welds, cavities, and joints.

[0003] In existing technologies, welding adhesives generally suffer from problems such as limited expansion ratio, insufficient stability of cell structure, and poor mechanical support performance at high temperatures. On the one hand, traditional foaming systems are prone to cell merging, collapse, or cooling shrinkage during the thermal expansion process, resulting in limited final expansion volume and unstable sealing effect. On the other hand, the interfacial bonding between conventional reinforcing fillers and the rubber matrix is ​​limited, making it difficult to balance high expansion ratio and cell wall strength during the foaming process, thus affecting the dimensional stability, heat resistance, and long-term service performance of the welding adhesive.

[0004] In addition, most of the thermal expansion microspheres, fiber reinforcement materials and processing aids commonly used in existing welding adhesives exist in a single-function form, with insufficient synergistic effect between the components, making it difficult to simultaneously meet the comprehensive requirements of high expansion, cell stability, interface reinforcement and processing adaptability.

[0005] Therefore, developing an ultra-high expansion soldering adhesive with high expansion ratio, stable cell structure and excellent overall performance is of great practical significance. Summary of the Invention

[0006] To address the problems of low expansion ratio of existing welding adhesives, easy collapse or shrinkage of foam structure after foaming, and difficulty in achieving comprehensive performance, this invention provides an ultra-high expansion welding adhesive and its preparation process.

[0007] In a first aspect, the present invention provides an ultra-high expansion welding adhesive, which adopts the following technical solution:

[0008] An ultra-high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts of EPDM rubber, 4-6 parts of functionalized thermal expansion microspheres, 1-2 parts of modified aramid fiber, 3-5 parts of composite amide wax, 10-20 parts of calcium carbonate, 10-12 parts of paraffin oil, 5-8 parts of azodicarbonamide, and 0.2-0.4 parts of peroxide.

[0009] Preferably, the peroxide is composed of a mixture of DCP and BIPB in a mass ratio of 1-1.5:1.

[0010] Preferably, the preparation method of the functionalized thermally expandable microspheres includes the following steps:

[0011] A1. Add the thermally expanded microspheres to the mixed solvent, add polycaprolactone, stir until uniform, then add deionized water, continue stirring until uniform, filter, wash and dry to obtain PCL-coated thermally expanded microspheres.

[0012] A2. Tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane were added to the mixed solution, the pH of the system was adjusted to 4-5, and the reaction was stirred. Then the pH of the system was adjusted to 7-8, PCL-coated thermal expansion microspheres and nano zinc oxide were added, and the reaction was stirred again. After the reaction was completed, the functionalized thermal expansion microspheres were obtained by filtration, washing and drying.

[0013] Preferably, in step A1, the mass ratio of thermally expanded microspheres, polycaprolactone, and mixed solvent is 10:1.5-2:90-100.

[0014] Preferably, the mixed solvent in step A1 is composed of dichloromethane and acetone mixed in a volume ratio of 7-8:2-3.

[0015] Preferably, the term "stirring evenly" in step A1 refers to stirring for 20-30 minutes at room temperature and a speed of 300-400 rpm.

[0016] Preferably, in step A1, the mass of deionized water is 3-4 times the mass of the mixed solvent.

[0017] Preferably, in step A1, continuing to stir until homogeneous means stirring for 40-60 minutes at room temperature and a speed of 200-300 rpm.

[0018] Preferably, the filtration, washing, and drying in step A1 refers to: filtering with medium-speed quantitative filter paper under a vacuum of -0.04MPa to -0.06MPa, washing the filter cake with deionized water 2-3 times, and drying it at a temperature of 40-50℃ for 8-10 hours.

[0019] Preferably, in step A2, the mass ratio of PCL-coated thermally expandable microspheres, tetraethyl orthosilicate, γ-glycidyl etheroxypropyltrimethoxysilane, nano zinc oxide, and the mixed solution is 10:0.3-0.5:0.6-1:0.5-1:80-100.

[0020] Preferably, the mixed solution in step A2 is composed of anhydrous ethanol and deionized water in a volume ratio of 9-9.5:0.5-1.

[0021] Preferably, the stirring reaction in step A2 refers to stirring the reaction for 20-30 minutes at room temperature and a rotation speed of 300-400 rpm.

[0022] Preferably, in step A2, the continued stirring reaction means continuing the stirring reaction for 2-3 hours at room temperature and a rotation speed of 300-400 rpm.

[0023] Preferably, in step A2, the filtration, washing, and drying process refers to: filtering with medium-speed quantitative filter paper under a vacuum of -0.04MPa to -0.06MPa, washing the filter cake 2-3 times with anhydrous ethanol, and then drying it at a temperature of 40-50℃ for 6-8 hours.

[0024] Preferably, the method for preparing the modified aramid fiber includes the following steps:

[0025] B1. Short-cut aramid fibers are activated by adding NaOH aqueous solution. After activation, the fibers are filtered, washed, and dried to obtain activated aramid fibers.

[0026] B2. Mix activated aramid fibers and deionized water, add tannic acid, stir evenly, adjust the pH of the system to 7-8, add ferric chloride aqueous solution, stir to react, after the reaction is completed, complete one deposition cycle, repeat the deposition cycle 2-3 times, filter, wash and dry to obtain MPN coated aramid fibers.

[0027] B3. Under nitrogen protection, MPN-coated aramid fibers were added to anhydrous toluene, along with itaconic anhydride, triethylamine, and hydroquinone. The mixture was stirred and reacted. After the reaction was completed, the fibers were filtered, washed, and dried to obtain modified aramid fibers.

[0028] Preferably, the mass ratio of chopped aramid fibers to NaOH aqueous solution in step B1 is 1:15-20.

[0029] Preferably, the mass fraction of the NaOH aqueous solution in step B1 is 5-8%.

[0030] Preferably, the activation in step B1 refers to: stirring and activating for 2-3 hours at a temperature of 60-70℃ and a rotation speed of 200-300rpm.

[0031] Preferably, in step B1, the filtration, washing, and drying process refers to: filtering with nylon filter cloth with a pore size of 30-50 μm under a vacuum of -0.06 MPa to -0.08 MPa, washing the filter cake with deionized water until the washing liquid is neutral, and then drying it at a temperature of 60-70°C for 4-6 hours.

[0032] Preferably, in step B2, the mass ratio of activated aramid fiber to deionized water is 1:40-50; the mass of tannic acid added in each deposition cycle is 5-10% of the mass of activated aramid fiber, and the mass of ferric chloride hexahydrate added is 2-3% of the mass of activated aramid fiber.

[0033] Preferably, the mass fraction of the ferric chloride aqueous solution in step B2 is 1-2%.

[0034] Preferably, the term "stirring evenly" in step B2 refers to stirring for 5-10 minutes at room temperature and a speed of 200-300 rpm.

[0035] Preferably, the stirring reaction in step B2 refers to stirring the reaction for 20-30 minutes at room temperature and a rotation speed of 300-400 rpm.

[0036] Preferably, in step B2, one deposition cycle refers to: adding tannic acid → stirring evenly → adjusting pH → adding ferric chloride aqueous solution → stirring reaction.

[0037] Preferably, in step B2, the filtration, washing, and drying process refers to: filtering with nylon filter cloth with a pore size of 30-50 μm under a vacuum of -0.06 MPa to -0.08 MPa, washing the filter cake with deionized water 2-3 times, and drying at a temperature of 40-50℃ for 4-6 hours.

[0038] Preferably, in step B3, the mass ratio of MPN-coated aramid fiber, itaconic anhydride, triethylamine, hydroquinone, and anhydrous toluene is 10:1-2:0.3-0.5:0.005-0.01:80-100.

[0039] Preferably, the stirring reaction in step B3 refers to stirring the reaction for 3-4 hours at a temperature of 80-90℃ and a rotation speed of 300-400 rpm.

[0040] Preferably, in step B3, the filtration, washing, and drying process refers to: filtering with nylon filter cloth with a pore size of 30-50 μm under a vacuum of -0.06 MPa to -0.08 MPa, washing the filter cake with anhydrous toluene and anhydrous ethanol 2-3 times each, and then drying it at a temperature of 50-60℃ for 6-8 hours.

[0041] Preferably, the preparation method of the composite amide wax includes the following steps:

[0042] After heating and melting ethylene bis-stearamide, maleic anhydride and vinyltrimethoxysilane were added and stirred until completely dissolved. Then, dicumyl peroxide was added and stirred to react. After the reaction was completed, the mixture was cooled and solidified. After crushing, washing, drying, grinding and sieving, a composite amide wax was obtained.

[0043] Preferably, the mass ratio of ethylene bis-stearamide, maleic anhydride, vinyltrimethoxysilane and dicumyl peroxide is 100:5-8:3-5:1-1.5.

[0044] Preferably, the heating and melting temperature is 145-155°C.

[0045] Preferably, the stirring until completely dissolved means stirring for 10-15 minutes at a temperature of 145-155℃ and a speed of 100-200 rpm.

[0046] Preferably, the stirring reaction refers to a stirring reaction for 35-45 minutes at a temperature of 155-165℃ and a rotation speed of 150-200 rpm.

[0047] Preferably, the crushing, washing, and drying process refers to: using a universal crusher, crushing at a speed of 16000-18000 rpm for 2-3 minutes, washing with acetone 2-3 times, and drying at a temperature of 60-70℃ for 4-6 hours.

[0048] Preferably, the grinding and sieving refers to: using a planetary ball mill, grinding for 10-15 minutes at a speed of 300-400 rpm, and then passing through an 80-100 mesh sieve.

[0049] Secondly, the present invention provides a preparation process for ultra-high expansion soldering adhesive, which adopts the following technical solution:

[0050] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0051] S1. Add EPDM rubber to a mixer for plasticizing, then add compound amide wax, paraffin oil and calcium carbonate in sequence, mix evenly, discharge the rubber after mixing, and then re-mix and sheet it on a two-roll mill. After sheeting, let it stand at room temperature to obtain the masterbatch.

[0052] S2. Wrap the masterbatch on the rollers of the open mill, and add functionalized thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. After thinning and uniformly extruding, the mixture is sheeted to obtain the compound.

[0053] S3. Calender the compounded rubber into sheets, cool and cut them to obtain ultra-high expansion welding adhesive.

[0054] Preferably, in step S1, plasticizing refers to plasticizing for 2-3 minutes at a temperature of 80-90℃ and a rotor speed of 50-60 rpm.

[0055] Preferably, in step S1, uniform mixing means mixing for 8-10 minutes at a mixing temperature of 100-110℃ and a rotor speed of 60-70 rpm.

[0056] Preferably, in step S1, the process of turning and cutting on the open mill refers to: after forming a triangular wrap 3-5 times under the conditions of a roll temperature of 50-60℃ and a roll gap of 0.5-1mm, the roll gap is adjusted to 6-8mm before cutting the sheet.

[0057] Preferably, in step S1, "room temperature storage" means storing at room temperature for 4-8 hours.

[0058] Preferably, in step S2, the roll wrapping refers to wrapping the roll for 2-3 minutes under the conditions of a roll temperature of 50-60℃ and a roll gap of 1.5-2mm.

[0059] Preferably, in step S2, the thin pass through the film evenly and then the film is unloaded: the film is passed through the film 3-5 times with a roller gap of 0.3-0.5mm, the roller temperature does not exceed 80℃, the glue discharge temperature does not exceed 90℃, and the roller gap is adjusted to 6-8mm before unloading.

[0060] Preferably, in step S3, calendering into sheets refers to calendering under the conditions of a calender roll temperature of 70-80℃ and a roll speed ratio of 1:1.1-1.2 to obtain a sheet with a thickness of 2-2.5mm.

[0061] In summary, the present invention has the following beneficial effects:

[0062] 1. The functionalized thermally expandable microspheres prepared in this invention form a composite functional layer on the surface of the microspheres through surface coating and silanization treatment. The PCL coating layer buffers and protects the microsphere shell during thermal expansion, reducing pore rupture. The silanization layer introduces active groups onto the microsphere surface, enhancing the interfacial bonding between the thermally expandable microspheres and the EPDM rubber matrix, thereby improving the dispersibility and compatibility of the thermally expandable microspheres in the rubber matrix, which is beneficial for improving the expansion uniformity and stability of the welding adhesive.

[0063] 2. This invention involves sequentially alkali-activated aramid fibers, MPN coating, and itaconic anhydride grafting. Alkali activation enhances the surface activity of the aramid fibers, providing reaction sites for subsequent surface deposition. MPN coating constructs a metal-polyphenol network layer on the aramid fiber surface, improving surface reactivity and interfacial compatibility. Itaconic anhydride grafting introduces functional groups capable of participating in rubber system reactions onto the aramid fiber surface, thereby strengthening the interfacial bonding strength between the aramid fibers and the rubber matrix. This improves the structural integrity and support performance of the foamed welding adhesive.

[0064] 3. The composite amide wax prepared in this invention uses ethylene bis-stearamide as a matrix, introducing polar groups through grafting maleic anhydride and silane groups through grafting vinyltrimethoxysilane, thus possessing both lubricating modification and interface regulation functions. This composite amide wax improves the processing fluidity of the system during the mixing stage, enhances the interfacial bonding between aramid fibers and the rubber matrix during the curing stage, and stabilizes the cell structure after foaming and curing, reducing cell shrinkage and collapse during cooling, thereby improving the dimensional stability of the welding adhesive.

[0065] 4. This invention introduces functionalized thermally expandable microspheres, modified aramid fibers, and composite amide wax into a EPDM rubber system. These three components work synergistically during the foaming and curing process. The functionalized thermally expandable microspheres provide expansion, the modified aramid fibers provide support for the foam structure, and the composite amide wax promotes interfacial bonding and cell stability. This results in a welding adhesive that, under heating conditions, exhibits a high expansion ratio, a stable cell structure, and good sealing, filling, and reinforcing effects. Combined with a staged mixing and calendering process, the uniform dispersion and processing stability of each component in the system are ensured, thus meeting the requirements of the welding industry for high expansion ratios and comprehensive performance. Detailed Implementation

[0066] The present invention will be further described in detail below with reference to the embodiments.

[0067] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0068] The key raw materials used in the embodiments and comparative examples of this invention are sourced from the following sources:

[0069] Thermal expansion microspheres: Brand: Weiyi Trading, Model: JUZ-8019, purchased from Shanghai Weiyi New Materials Co., Ltd.

[0070] Polycaprolactone: CAS No.: 24980-41-4, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0071] γ-glycidoxypropyltrimethoxysilane: CAS No.: 2530-83-8, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0072] Short-cut aramid fiber: Brand: Shuobang New Materials, Specification: 6mm, purchased from Jiangxi Shuobang New Materials Technology Co., Ltd.;

[0073] Vinyltrimethoxysilane: CAS No.: 2768-02-7, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0074] Ethylene bis-stearamide: CAS No.: 110-30-5, purchased from Hubei Biaoyue Biotechnology Development Co., Ltd.;

[0075] EPDM rubber: Brand: Dow Chemical, Model: 774P, purchased from Dongguan Xinchengda Plastics Co., Ltd.

[0076] Paraffin oil: Brand: Taichang, Model: No. 10, purchased from Shandong Taichang Petrochemical Technology Co., Ltd.

[0077] Examples 1-3 provide an ultra-high expansion soldering adhesive and its preparation process.

[0078] Example 1

[0079] The preparation method of functionalized thermally expandable microspheres includes the following steps:

[0080] A1. The mass ratio of thermally expanded microspheres, polycaprolactone, and mixed solvent was controlled at 10:1.5:90. The thermally expanded microspheres were added to the mixed solvent (composed of dichloromethane and acetone in a volume ratio of 7:3). Polycaprolactone was added, and the mixture was stirred for 30 min at room temperature and 300 rpm. Then, deionized water (three times the mass of the mixed solvent) was added to precipitate the precipitate. The mixture was stirred for another 60 min at room temperature and 200 rpm. The mixture was then filtered using medium-speed quantitative filter paper under a vacuum of -0.04 MPa. The filter cake was washed twice with deionized water and dried at 40℃ for 10 h to obtain PCL-coated thermally expanded microspheres.

[0081] A2. The mass ratio of PCL-coated thermal expansion microspheres, tetraethyl orthosilicate, γ-glycidoxypropyltrimethoxysilane, nano zinc oxide, and the mixed solution was controlled at 10:0.3:0.6:0.5:80. Tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane were added to the mixed solution (composed of anhydrous ethanol and deionized water in a volume ratio of 9:1). The pH of the system was adjusted to 4 using a 0.5% acetic acid aqueous solution. The reaction was stirred at room temperature and 300 rpm for 30 min. Then, the pH of the system was adjusted to 7 using a 0.5% ammonia solution. The PCL-coated thermal expansion microspheres and nano zinc oxide were added. The reaction was continued at room temperature and 300 rpm for 3 h. After the reaction was completed, the mixture was filtered under a vacuum of -0.04 MPa using medium-speed quantitative filter paper. The filter cake was washed twice with anhydrous ethanol and dried at 40℃ for 8 h to obtain functionalized thermal expansion microspheres.

[0082] The preparation method of modified aramid fiber includes the following steps:

[0083] B1. Control the mass ratio of chopped aramid fibers to NaOH aqueous solution to 1:15. Add the chopped aramid fibers to NaOH aqueous solution with a mass fraction of 5% and stir to activate for 3 hours at 60℃ and 200 rpm. After activation, filter the solution using nylon filter cloth with a pore size of 30μm under a vacuum of -0.06MPa. Wash the filter cake with deionized water until the washing solution is neutral and then dry it at 60℃ for 6 hours to obtain activated aramid fibers.

[0084] B2. Controlling the mass ratio of activated aramid fiber to deionized water to 1:40, the activated aramid fiber and deionized water were mixed, and tannic acid (5% of the mass of activated aramid fiber) was added. The mixture was stirred for 10 min at room temperature and 200 rpm. The pH of the system was adjusted to 7 using a 5% NaOH aqueous solution. A 1% ferric chloride aqueous solution (2% of the mass of activated aramid fiber) was added, and the mixture was stirred for 30 min at room temperature and 300 rpm. After the reaction was completed, one deposition cycle was completed (add tannic acid → stir evenly → adjust pH → add ferric chloride aqueous solution → stir reaction). The deposition cycle was repeated twice. The mixture was then filtered using a nylon filter cloth with a pore size of 30 μm under a vacuum of -0.06 MPa. The filter cake was washed twice with deionized water and dried at 40℃ for 6 h to obtain MPN-coated aramid fiber.

[0085] B3. The mass ratio of MPN-coated aramid fiber, itaconic anhydride, triethylamine, hydroquinone, and anhydrous toluene was controlled at 10:1:0.3:0.005:80. Under nitrogen protection, the MPN-coated aramid fiber was added to anhydrous toluene, along with itaconic anhydride, triethylamine, and hydroquinone. The mixture was stirred and reacted at 80℃ and 300rpm for 4 hours. After the reaction was completed, the mixture was filtered under a vacuum of -0.06MPa using a nylon filter cloth with a pore size of 30μm. The filter cake was washed twice each with anhydrous toluene and anhydrous ethanol, and then dried at 50℃ for 8 hours to obtain modified aramid fiber.

[0086] The preparation method of the composite amide wax includes the following steps:

[0087] The mass ratio of ethylene bis-stearamide, maleic anhydride, vinyltrimethoxysilane, and dicumyl peroxide was controlled at 100:5:3:1. Ethylene bis-stearamide was melted at 145°C, maleic anhydride and vinyltrimethoxysilane were added, and the mixture was stirred at 145°C and 100 rpm for 15 minutes until completely dissolved. Dicumyl peroxide was then added, and the mixture was stirred at 155°C and 150 rpm for 45 minutes. After the reaction was completed, the mixture was cooled to room temperature to solidify. It was then pulverized at 16000 rpm for 3 minutes using a universal pulverizer, washed twice with acetone, dried at 60°C for 6 hours, and then ground at 300 rpm for 15 minutes using a planetary ball mill. Finally, it was passed through an 80-mesh sieve to obtain the composite amide wax.

[0088] The peroxide is composed of a 1:1 mass ratio of DCP and BIPB.

[0089] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts EPDM rubber, 4 parts functionalized thermal expansion microspheres, 1 part modified aramid fiber, 3 parts composite amide wax, 10 parts calcium carbonate, 10 parts paraffin oil, 5 parts azodicarbonamide, and 0.2 parts peroxide.

[0090] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0091] S1. Add EPDM rubber to a mixer and plasticize for 3 minutes at 80℃ and 50 rpm. Then add compound amide wax, paraffin oil and calcium carbonate in sequence and mix for 10 minutes at 100℃ and 60 rpm. After mixing, discharge the rubber and make triangular wraps 5 times at 50℃ and 0.5mm. Adjust the roller gap to 6mm and sheet the rubber. Let it stand at room temperature for 4 hours to obtain the masterbatch.

[0092] S2. Add the masterbatch to the open mill and wrap it around the rolls for 3 minutes at a roll temperature of 50℃ and a roll gap of 1.5mm. Then add the functionalized thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. Pass it through the mill 3 times at a roll gap of 0.3mm, with the roll temperature not exceeding 80℃ and the discharge temperature not exceeding 90℃. Adjust the roll gap to 6mm and sheet it to obtain the compound.

[0093] S3. The compounded rubber is calendered in a calender at a roller temperature of 70℃ and a roller speed ratio of 1:1.1 to obtain a sheet with a thickness of 2mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0094] Example 2

[0095] The preparation method of functionalized thermally expandable microspheres includes the following steps:

[0096] A1. The mass ratio of thermally expanded microspheres, polycaprolactone, and mixed solvent was controlled at 10:1.75:95. The thermally expanded microspheres were added to the mixed solvent (composed of dichloromethane and acetone in a volume ratio of 7.5:2.5). Polycaprolactone was added, and the mixture was stirred for 25 min at room temperature and 350 rpm. Then, deionized water (3.5 times the mass of the mixed solvent) was added to precipitate the precipitate. The mixture was stirred for another 50 min at room temperature and 250 rpm. The mixture was then filtered using medium-speed quantitative filter paper under a vacuum of -0.05 MPa. The filter cake was washed three times with deionized water and dried at 45℃ for 9 h to obtain PCL-coated thermally expanded microspheres.

[0097] A2. The mass ratio of PCL-coated thermally expanding microspheres, tetraethyl orthosilicate, γ-glycidoxypropyltrimethoxysilane, nano-zinc oxide, and the mixed solution was controlled to be 10:0.4:0.8:0.75:90. Tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane were added to the mixed solution (composed of anhydrous ethanol and deionized water in a volume ratio of 9.2:0.8). The pH of the system was adjusted to 4.5 using a 0.5% (w / w) acetic acid aqueous solution. The mixture was then heated at room temperature. The reaction was stirred at 350 rpm for 25 min. Then, the pH of the system was adjusted to 7.5 with 0.5% ammonia water. PCL-coated thermal expansion microspheres and nano zinc oxide were added. The reaction was stirred at room temperature and 350 rpm for 2.5 h. After the reaction was completed, the mixture was filtered under a vacuum of -0.05 MPa using medium-speed quantitative filter paper. The filter cake was washed three times with anhydrous ethanol and dried at 45℃ for 7 h to obtain functionalized thermal expansion microspheres.

[0098] The preparation method of modified aramid fiber includes the following steps:

[0099] B1. Controlling the mass ratio of chopped aramid fibers to NaOH aqueous solution to 1:17.5, the chopped aramid fibers were added to a 6% NaOH aqueous solution and stirred for 2.5 hours at 65℃ and 250 rpm. After activation, the solution was filtered using a nylon filter cloth with a pore size of 40 μm under a vacuum of -0.07 MPa. The filter cake was washed with deionized water until the washing solution was neutral and then dried at 65℃ for 5 hours to obtain activated aramid fibers.

[0100] B2. Controlling the mass ratio of activated aramid fiber to deionized water to 1:45, the activated aramid fiber and deionized water were mixed, and tannic acid (8% of the mass of activated aramid fiber) was added. The mixture was stirred for 7.5 min at room temperature and 250 rpm. The pH of the system was adjusted to 7.5 using a 5% NaOH aqueous solution. A 1.5% ferric chloride aqueous solution (2.5% of the mass of activated aramid fiber) was added, and the mixture was stirred for 25 min at room temperature and 350 rpm. After the reaction was completed, one deposition cycle was completed (add tannic acid → stir evenly → adjust pH → add ferric chloride aqueous solution → stir reaction). The deposition cycle was repeated 3 times. The mixture was then filtered using a nylon filter cloth with a pore size of 40 μm under a vacuum of -0.07 MPa. The filter cake was washed 3 times with deionized water and dried at 45℃ for 5 h to obtain MPN-coated aramid fiber.

[0101] B3. The mass ratio of MPN-coated aramid fiber, itaconic anhydride, triethylamine, hydroquinone, and anhydrous toluene was controlled at 10:1.5:0.4:0.008:90. Under nitrogen protection, MPN-coated aramid fiber was added to anhydrous toluene, along with itaconic anhydride, triethylamine, and hydroquinone. The mixture was stirred and reacted at 85°C and 350 rpm for 3.5 h. After the reaction was completed, the mixture was filtered under a vacuum of -0.07 MPa using a nylon filter cloth with a pore size of 40 μm. The filter cake was washed three times each with anhydrous toluene and anhydrous ethanol, and then dried at 55°C for 7 h to obtain modified aramid fiber.

[0102] The preparation method of the composite amide wax includes the following steps:

[0103] The mass ratio of ethylene bis-stearamide, maleic anhydride, vinyltrimethoxysilane, and dicumyl peroxide was controlled at 100:6.5:4:1.25. Ethylene bis-stearamide was melted at 150°C, then maleic anhydride and vinyltrimethoxysilane were added. The mixture was stirred at 150°C and 150 rpm for 12.5 min until completely dissolved. Dicumyl peroxide was then added, and the mixture was stirred at 160°C and 180 rpm for 40 min. After the reaction was complete, the mixture was cooled to room temperature to solidify. It was then pulverized at 17000 rpm for 2.5 min using a universal pulverizer, washed three times with acetone, and dried at 65°C for 5 h. Finally, it was ground at 350 rpm for 12.5 min using a planetary ball mill and passed through a 90-mesh sieve to obtain the composite amide wax.

[0104] The peroxide is composed of a mixture of DCP and BIPB in a mass ratio of 1.25:1.

[0105] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts EPDM rubber, 5 parts functionalized thermal expansion microspheres, 1.5 parts modified aramid fiber, 4 parts composite amide wax, 15 parts calcium carbonate, 11 parts paraffin oil, 6.5 parts azodicarbonamide, and 0.3 parts peroxide.

[0106] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0107] S1. Add EPDM rubber to a mixer and plasticize for 2.5 minutes at a temperature of 85℃ and a rotor speed of 55 rpm. Then add compound amide wax, paraffin oil and calcium carbonate in sequence and mix for 9 minutes at a mixing temperature of 105℃ and a rotor speed of 65 rpm. After mixing, discharge the rubber and make triangular wraps 4 times at a roller temperature of 55℃ and a roller gap of 0.8 mm. After adjusting the roller gap to 7 mm and sheeting, let it stand at room temperature for 6 hours to obtain the masterbatch.

[0108] S2. Add the masterbatch to the open mill and wrap it around the rolls for 2.5 minutes at a roll temperature of 55℃ and a roll gap of 1.8mm. Then add the functionalized thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. Pass it through the mill 4 times at a roll gap of 0.4mm, with the roll temperature not exceeding 80℃ and the discharge temperature not exceeding 90℃. Adjust the roll gap to 7mm and sheet it to obtain the compound.

[0109] S3. The compounded rubber is calendered in a calender at a roller temperature of 75°C and a roller speed ratio of 1:1.15 to obtain a sheet with a thickness of 2.3mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0110] Example 3

[0111] The preparation method of functionalized thermally expandable microspheres includes the following steps:

[0112] A1. The mass ratio of thermally expanded microspheres, polycaprolactone, and mixed solvent was controlled at 10:2:100. The thermally expanded microspheres were added to the mixed solvent (composed of dichloromethane and acetone in a volume ratio of 8:2). Polycaprolactone was added, and the mixture was stirred for 20 min at room temperature and 400 rpm. Then, deionized water (4 times the mass of the mixed solvent) was added to precipitate the precipitate. The mixture was stirred for another 40 min at room temperature and 300 rpm. The mixture was then filtered using medium-speed quantitative filter paper under a vacuum of -0.06 MPa. The filter cake was washed three times with deionized water and dried at 50°C for 8 h to obtain PCL-coated thermally expanded microspheres.

[0113] A2. The mass ratio of PCL-coated thermally expanding microspheres, tetraethyl orthosilicate, γ-glycidoxypropyltrimethoxysilane, nano zinc oxide, and the mixed solution was controlled at 10:0.5:1:1:100. Tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane were added to the mixed solution (composed of anhydrous ethanol and deionized water in a volume ratio of 9.5:0.5). The pH of the system was adjusted to 5 using a 0.5% acetic acid aqueous solution. The reaction was stirred at room temperature and 400 rpm for 20 min. Then, the pH of the system was adjusted to 8 using a 0.5% ammonia solution. The PCL-coated thermally expanding microspheres and nano zinc oxide were added. The reaction was stirred at room temperature and 400 rpm for 2 h. After the reaction was completed, the mixture was filtered under a vacuum of -0.06 MPa using medium-speed quantitative filter paper. The filter cake was washed three times with anhydrous ethanol and then dried at 50℃ for 6 h to obtain functionalized thermally expanding microspheres.

[0114] The preparation method of modified aramid fiber includes the following steps:

[0115] B1. Control the mass ratio of chopped aramid fibers to NaOH aqueous solution to 1:20. Add the chopped aramid fibers to NaOH aqueous solution with a mass fraction of 8% and stir to activate for 2 hours at 70℃ and 300 rpm. After activation, filter the solution using nylon filter cloth with a pore size of 50μm under a vacuum of -0.08MPa. Wash the filter cake with deionized water until the washing solution is neutral and then dry it at 70℃ for 4 hours to obtain activated aramid fibers.

[0116] B2. Control the mass ratio of activated aramid fiber and deionized water to 1:50. Mix the activated aramid fiber and deionized water, add tannic acid (10% of the mass of activated aramid fiber), and stir for 5 min at room temperature and 300 rpm. Adjust the pH of the system to 8 using a 5% NaOH aqueous solution. Add a 2% ferric chloride aqueous solution (3% of the mass of activated aramid fiber), and stir for 20 min at room temperature and 400 rpm. After the reaction is complete, complete one deposition cycle (add tannic acid → stir evenly → adjust pH → add ferric chloride aqueous solution → stir reaction). Repeat the deposition cycle 3 times. Filter the mixture using a nylon filter cloth with a pore size of 50 μm under a vacuum of -0.08 MPa. Wash the filter cake 3 times with deionized water and dry it at 50℃ for 4 h to obtain MPN-coated aramid fiber.

[0117] B3. The mass ratio of MPN-coated aramid fiber, itaconic anhydride, triethylamine, hydroquinone, and anhydrous toluene was controlled at 10:2:0.5:0.01:100. Under nitrogen protection, the MPN-coated aramid fiber was added to anhydrous toluene, along with itaconic anhydride, triethylamine, and hydroquinone. The mixture was stirred and reacted at 90℃ and 400rpm for 3 hours. After the reaction was completed, the mixture was filtered under a vacuum of -0.08MPa using a nylon filter cloth with a pore size of 50μm. The filter cake was washed three times each with anhydrous toluene and anhydrous ethanol, and then dried at 60℃ for 6 hours to obtain modified aramid fiber.

[0118] The preparation method of the composite amide wax includes the following steps:

[0119] The mass ratio of ethylene bis-stearamide, maleic anhydride, vinyltrimethoxysilane, and dicumyl peroxide was controlled at 100:8:5:1.5. Ethylene bis-stearamide was melted at 155°C, maleic anhydride and vinyltrimethoxysilane were added, and the mixture was stirred at 155°C and 200 rpm for 10 min until completely dissolved. Dicumyl peroxide was added, and the mixture was stirred at 165°C and 200 rpm for 35 min. After the reaction was completed, the mixture was cooled to room temperature to solidify. It was then pulverized at 18000 rpm for 2 min using a universal pulverizer, washed three times with acetone, dried at 70°C for 4 h, and then ground at 400 rpm for 10 min using a planetary ball mill. Finally, it was passed through a 100-mesh sieve to obtain the composite amide wax.

[0120] The peroxide is composed of a mixture of DCP and BIPB in a mass ratio of 1.5:1.

[0121] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts of EPDM rubber, 6 parts of functionalized thermal expansion microspheres, 2 parts of modified aramid fiber, 5 parts of composite amide wax, 20 parts of calcium carbonate, 12 parts of paraffin oil, 8 parts of azodicarbonamide, and 0.4 parts of peroxide.

[0122] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0123] S1. Add EPDM rubber to a mixer and plasticize for 2 minutes at 90℃ and 60 rpm. Then add compound amide wax, paraffin oil and calcium carbonate in sequence and mix for 8 minutes at 110℃ and 70 rpm. After mixing, discharge the rubber and make three triangular wraps at 60℃ and 1mm roller gap. Adjust the roller gap to 8mm and sheet the rubber. Let it stand at room temperature for 8 hours to obtain the masterbatch.

[0124] S2. Add the masterbatch to the open mill and wrap it around the roll for 2 minutes at a roll temperature of 60℃ and a roll gap of 2mm. Then add the functionalized thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. Pass it through the mill 5 times at a roll gap of 0.5mm, with the roll temperature not exceeding 80℃ and the discharge temperature not exceeding 90℃. Adjust the roll gap to 8mm and sheet it to obtain the compound.

[0125] S3. The compounded rubber is calendered in a calender at a roller temperature of 80℃ and a roller speed ratio of 1:1.2 to obtain a sheet with a thickness of 2.5mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0126] To verify the comprehensive performance of the ultra-high expansion soldering adhesives prepared in Examples 1-3 of this invention, the inventors set up Comparative Examples 1-7, as follows:

[0127] Comparative Example 1

[0128] The difference between this comparative example and Example 1 is that the functionalized thermal expansion microspheres are replaced with thermal expansion microspheres of equal mass, while the remaining steps and raw materials are the same as in Example 1.

[0129] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts EPDM rubber, 4 parts thermal expansion microspheres, 1 part modified aramid fiber, 3 parts composite amide wax, 10 parts calcium carbonate, 10 parts paraffin oil, 5 parts azodicarbonamide, and 0.2 parts peroxide.

[0130] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0131] S1. Add EPDM rubber to a mixer and plasticize for 3 minutes at 80℃ and 50 rpm. Then add compound amide wax, paraffin oil and calcium carbonate in sequence and mix for 10 minutes at 100℃ and 60 rpm. After mixing, discharge the rubber and make triangular wraps 5 times at 50℃ and 0.5mm. Adjust the roller gap to 6mm and sheet the rubber. Let it stand at room temperature for 4 hours to obtain the masterbatch.

[0132] S2. Add the masterbatch to the open mill and wrap it around the rolls for 3 minutes at a roll temperature of 50℃ and a roll gap of 1.5mm. Then add the thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. Pass it through the mill 3 times at a roll gap of 0.3mm, with the roll temperature not exceeding 80℃ and the discharge temperature not exceeding 90℃. Adjust the roll gap to 6mm and sheet it to obtain the compound.

[0133] S3. The compounded rubber is calendered in a calender at a roller temperature of 70℃ and a roller speed ratio of 1:1.1 to obtain a sheet with a thickness of 2mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0134] Comparative Example 2

[0135] The difference between this comparative example and Example 1 is that the functionalized thermal expansion microspheres are replaced with PCL-coated thermal expansion microspheres of equal mass, while the remaining steps and raw materials are the same as in Example 1.

[0136] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts of EPDM rubber, 4 parts of PCL-coated thermal expansion microspheres, 1 part of modified aramid fiber, 3 parts of composite amide wax, 10 parts of calcium carbonate, 10 parts of paraffin oil, 5 parts of azodicarbonamide, and 0.2 parts of peroxide.

[0137] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0138] S1. Add EPDM rubber to a mixer and plasticize for 3 minutes at 80℃ and 50 rpm. Then add compound amide wax, paraffin oil and calcium carbonate in sequence and mix for 10 minutes at 100℃ and 60 rpm. After mixing, discharge the rubber and make triangular wraps 5 times at 50℃ and 0.5mm. Adjust the roller gap to 6mm and sheet the rubber. Let it stand at room temperature for 4 hours to obtain the masterbatch.

[0139] S2. Add the masterbatch to the open mill and wrap the rolls for 3 minutes at a roll temperature of 50℃ and a roll gap of 1.5mm. Then add PCL-coated thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. Pass the mixture through the mill 3 times at a roll gap of 0.3mm, with the roll temperature not exceeding 80℃ and the discharge temperature not exceeding 90℃. Adjust the roll gap to 6mm and sheet the mixture to obtain the compound.

[0140] S3. The compounded rubber is calendered in a calender at a roller temperature of 70℃ and a roller speed ratio of 1:1.1 to obtain a sheet with a thickness of 2mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0141] Comparative Example 3

[0142] The difference between this comparative example and Example 1 is that the modified aramid fiber is replaced with chopped aramid fiber by the same mass, while the remaining steps and raw materials are the same as in Example 1.

[0143] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts EPDM rubber, 4 parts functionalized thermal expansion microspheres, 1 part chopped aramid fiber, 3 parts composite amide wax, 10 parts calcium carbonate, 10 parts paraffin oil, 5 parts azodicarbonamide, and 0.2 parts peroxide.

[0144] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0145] S1. Add EPDM rubber to a mixer and plasticize for 3 minutes at 80℃ and 50 rpm. Then add compound amide wax, paraffin oil and calcium carbonate in sequence and mix for 10 minutes at 100℃ and 60 rpm. After mixing, discharge the rubber and make triangular wraps 5 times at 50℃ and 0.5mm. Adjust the roller gap to 6mm and sheet the rubber. Let it stand at room temperature for 4 hours to obtain the masterbatch.

[0146] S2. Add the masterbatch to the open mill and wrap it around the rolls for 3 minutes at a roll temperature of 50°C and a roll gap of 1.5 mm. Then add the functionalized thermal expansion microspheres, chopped aramid fibers, azodicarbonamide and peroxide in sequence. Pass the mixture through the mill 3 times at a roll gap of 0.3 mm, with the roll temperature not exceeding 80°C and the discharge temperature not exceeding 90°C. Adjust the roll gap to 6 mm and sheet the mixture to obtain the compound.

[0147] S3. The compounded rubber is calendered in a calender at a roller temperature of 70℃ and a roller speed ratio of 1:1.1 to obtain a sheet with a thickness of 2mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0148] Comparative Example 4

[0149] The difference between this comparative example and Example 1 is that the modified aramid fiber is replaced by MPN-coated aramid fiber of equal mass, while the remaining steps and raw materials are the same as in Example 1.

[0150] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts of EPDM rubber, 4 parts of functionalized thermal expansion microspheres, 1 part of MPN-coated aramid fiber, 3 parts of composite amide wax, 10 parts of calcium carbonate, 10 parts of paraffin oil, 5 parts of azodicarbonamide, and 0.2 parts of peroxide.

[0151] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0152] S1. Add EPDM rubber to a mixer and plasticize for 3 minutes at 80℃ and 50 rpm. Then add compound amide wax, paraffin oil and calcium carbonate in sequence and mix for 10 minutes at 100℃ and 60 rpm. After mixing, discharge the rubber and make triangular wraps 5 times at 50℃ and 0.5mm. Adjust the roller gap to 6mm and sheet the rubber. Let it stand at room temperature for 4 hours to obtain the masterbatch.

[0153] S2. Add the masterbatch to the open mill and wrap the rolls for 3 minutes at a roll temperature of 50℃ and a roll gap of 1.5mm. Then add functionalized thermal expansion microspheres, MPN-coated aramid fibers, azodicarbonamide, and peroxide in sequence. Pass the mixture through the mill 3 times at a roll gap of 0.3mm, with the roll temperature not exceeding 80℃ and the discharge temperature not exceeding 90℃. Adjust the roll gap to 6mm and sheet the mixture to obtain the compound.

[0154] S3. The compounded rubber is calendered in a calender at a roller temperature of 70℃ and a roller speed ratio of 1:1.1 to obtain a sheet with a thickness of 2mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0155] Comparative Example 5

[0156] The difference between this comparative example and Example 1 is that the composite amide wax is replaced with ethylene bis-stearamide by mass, while the remaining steps and raw materials are the same as in Example 1.

[0157] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts of EPDM rubber, 4 parts of functionalized thermal expansion microspheres, 1 part of modified aramid fiber, 3 parts of ethylene bis-stearamide, 10 parts of calcium carbonate, 10 parts of paraffin oil, 5 parts of azodicarbonamide, and 0.2 parts of peroxide.

[0158] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0159] S1. Add EPDM rubber to a mixer and plasticize for 3 minutes at 80℃ and 50 rpm. Then add ethylene bis-stearamide, paraffin oil and calcium carbonate in sequence and mix for 10 minutes at 100℃ and 60 rpm. After mixing, discharge the rubber and make triangular wraps 5 times at 50℃ and 0.5mm roller gap. Adjust the roller gap to 6mm and sheet the rubber. Let it stand at room temperature for 4 hours to obtain the masterbatch.

[0160] S2. Add the masterbatch to the open mill and wrap it around the rolls for 3 minutes at a roll temperature of 50℃ and a roll gap of 1.5mm. Then add the functionalized thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. Pass it through the mill 3 times at a roll gap of 0.3mm, with the roll temperature not exceeding 80℃ and the discharge temperature not exceeding 90℃. Adjust the roll gap to 6mm and sheet it to obtain the compound.

[0161] S3. The compounded rubber is calendered in a calender at a roller temperature of 70℃ and a roller speed ratio of 1:1.1 to obtain a sheet with a thickness of 2mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0162] Comparative Example 6

[0163] The difference between this comparative example and Example 1 is that no modified aramid fiber is added, while the remaining steps and raw materials are the same as in Example 1.

[0164] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts of EPDM rubber, 4 parts of functionalized thermal expansion microspheres, 4 parts of composite amide wax, 10 parts of calcium carbonate, 10 parts of paraffin oil, 5 parts of azodicarbonamide, and 0.2 parts of peroxide.

[0165] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0166] S1. Add EPDM rubber to a mixer and plasticize for 3 minutes at 80℃ and 50 rpm. Then add compound amide wax, paraffin oil and calcium carbonate in sequence and mix for 10 minutes at 100℃ and 60 rpm. After mixing, discharge the rubber and make triangular wraps 5 times at 50℃ and 0.5mm. Adjust the roller gap to 6mm and sheet the rubber. Let it stand at room temperature for 4 hours to obtain the masterbatch.

[0167] S2. Add the masterbatch to the open mill and wrap it around the roll for 3 minutes at a roll temperature of 50°C and a roll gap of 1.5 mm. Then add the functionalized thermal expansion microspheres, azodicarbonamide and peroxide in sequence. Pass it through the mill 3 times at a roll gap of 0.3 mm, with the roll temperature not exceeding 80°C and the discharge temperature not exceeding 90°C. Adjust the roll gap to 6 mm and sheet it to obtain the compound.

[0168] S3. The compounded rubber is calendered in a calender at a roller temperature of 70℃ and a roller speed ratio of 1:1.1 to obtain a sheet with a thickness of 2mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0169] Comparative Example 7

[0170] The difference between this comparative example and Example 1 is that no composite amide wax is added, while the remaining steps and raw materials are the same as in Example 1.

[0171] A high expansion welding adhesive comprises the following raw materials in parts by weight: 100 parts EPDM rubber, 4 parts functionalized thermal expansion microspheres, 4 parts modified aramid fiber, 10 parts calcium carbonate, 10 parts paraffin oil, 5 parts azodicarbonamide, and 0.2 parts peroxide.

[0172] A preparation process for an ultra-high expansion solder adhesive includes the following steps:

[0173] S1. Add EPDM rubber to a mixer and plasticize for 3 minutes at 80℃ and 50 rpm. Then add paraffin oil and calcium carbonate in sequence and mix for 10 minutes at 100℃ and 60 rpm. After mixing, discharge the rubber and form a triangular package 5 times at 50℃ and 0.5mm. Adjust the roller gap to 6mm and sheet the rubber. Let it stand at room temperature for 4 hours to obtain the masterbatch.

[0174] S2. Add the masterbatch to the open mill and wrap it around the rolls for 3 minutes at a roll temperature of 50℃ and a roll gap of 1.5mm. Then add the functionalized thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. Pass it through the mill 3 times at a roll gap of 0.3mm, with the roll temperature not exceeding 80℃ and the discharge temperature not exceeding 90℃. Adjust the roll gap to 6mm and sheet it to obtain the compound.

[0175] S3. The compounded rubber is calendered in a calender at a roller temperature of 70℃ and a roller speed ratio of 1:1.1 to obtain a sheet with a thickness of 2mm. After cooling to room temperature, it is cut to obtain ultra-high expansion welding adhesive.

[0176] Performance testing

[0177] The comprehensive performance of the ultra-high expansion solder adhesives prepared in Examples 1-3 and Comparative Examples 1-7 of this invention was tested respectively.

[0178] The ultra-high expansion solder adhesives prepared in Examples 1-3 and Comparative Examples 1-7 were placed in a standard environment of 23±2℃ and 50±10% relative humidity for 24 hours before performance testing was conducted.

[0179] 1. Expansion ratio

[0180] The ultra-high expansion solder adhesives prepared in Examples 1-3 and Comparative Examples 1-7 were cut into samples with dimensions of 50mm × 50mm × 2mm, respectively. Their initial length, width, and thickness were measured, and the initial volume V0 was calculated. The samples were then placed in a forced-air drying oven and baked at 180±2℃ for 30 minutes. After removal, they were cooled at room temperature for 2 hours, and their length, width, and thickness were measured again to calculate the expanded volume V1. The expansion ratio was calculated using the formula: Expansion Ratio = V1 / V0. Five samples were tested in parallel for each group, and the average value was taken as the test result.

[0181] 2. Average cell size

[0182] Cut the expanded sample along its thickness, select a region with uniform cell size in the middle of the sample, and determine the average cell size according to standard GB / T12811-2025 "Test Method for Average Cell Size of Rigid Foamed Plastics". Test 5 samples in each group in parallel, and take the average value as the test result.

[0183] 3. Compressive strength

[0184] The expanded specimens were processed to meet the dimensions required by standard GB / T 8813-2020 "Determination of Compressive Properties of Rigid Foamed Plastics". The specimens were placed between the upper and lower plates of a universal testing machine, ensuring the compression direction was aligned with the thickness direction and that the stress was uniform and the specimen was centered. The testing machine was started, and a loading rate of 5 mm / min was applied. The load-displacement relationship during compression was continuously recorded. When the specimen reached the specified compressive deformation, the corresponding compressive load was read and converted into compressive stress, which was used as the compressive strength characterization value of the specimen.

[0185] Compressive strength is calculated using the formula:

[0186] σ = F / A, where F is the load under specified compressive deformation in N; and A is the initial compressive area of ​​the specimen in mm².

[0187] Five samples were tested in parallel in each group, and the average value was taken as the test result.

[0188] 4. Overlap shear strength

[0189] Steel / steel single lap joint specimens were prepared in accordance with the standard GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)". Steel plates of the same size were selected as the substrates to be bonded. Before bonding, the surface of the steel plates was sanded with sandpaper and then cleaned with anhydrous ethanol to remove surface oil and impurities. After cleaning, the plates were allowed to air dry for later use.

[0190] The welding adhesive sample was evenly applied between the overlapping areas of the two steel plates, with the initial thickness of the adhesive layer controlled at 2 mm, ensuring uniform distribution and no obvious air bubbles or voids. The assembled sample was placed in an oven and baked at 180±2℃ for 30 minutes to allow the welding adhesive to expand and cure within the overlapping interface; then it was removed, cooled at room temperature, and placed in a standard environment for 24 hours.

[0191] During testing, the specimen is clamped in the universal testing machine fixture, ensuring the force direction is parallel to the lap joint surface to guarantee uniform stress and avoid uneven loading. Tension is applied at a tensile speed of 10 mm / min until specimen failure, and the maximum failure load Fmax is recorded. The lap shear strength is calculated using the formula:

[0192] τ = Fmax / A, where Fmax is the maximum load at which the specimen fails, in N; and A is the overlap area, in mm².

[0193] Five samples were tested in parallel in each group, and the average value was taken as the test result.

[0194] The test results are shown in Table 1.

[0195] Table 1: Performance parameters of ultra-high expansion solder adhesives in Examples 1-3 and Comparative Examples 1-7

[0196]

[0197] As shown in Table 1, the ultra-high expansion welding adhesives prepared in Examples 1-3 of this invention are significantly superior to Comparative Examples 1-7 in terms of expansion ratio, average cell size, compressive strength, and lap shear strength.

[0198] As shown by the data in Example 1 and Comparative Example 1, when using unmodified thermally expandable microspheres instead of functionalized thermally expandable microspheres in Comparative Example 1, the compatibility and interfacial bonding ability of the thermally expandable microspheres with the EPDM rubber matrix decreased, the dispersibility in the rubber compound deteriorated, and the nucleation and growth stability of the cells was insufficient when heated, resulting in a decrease in the expansion ratio of the welding adhesive, an increase in the average cell size, and a decrease in the compressive strength and lap shear strength.

[0199] As shown by the data from Example 1 and Comparative Example 2, in Comparative Example 2, PCL-coated thermal expansion microspheres were used to replace functionalized thermal expansion microspheres. Due to the lack of subsequent surface functionalization modification, the interfacial interaction between the microspheres and the rubber matrix and the stabilizing effect on the cell structure were weakened, resulting in a decrease in the expansion ratio of the welding adhesive, an increase in the average cell size, and lower compression strength and lap shear strength than in Example 1.

[0200] As shown by the data from Example 1 and Comparative Example 3, in Comparative Example 3, unmodified chopped aramid fibers were used instead of modified aramid fibers. The aramid fibers had insufficient active sites on their surface, resulting in weakened interfacial compatibility and adhesion with the rubber matrix. This reduced the supporting effect on the cell structure, leading to poor cell uniformity, reduced expansion ratio, and increased average cell size after the welding adhesive expanded. At the same time, the compressive strength and lap shear strength decreased.

[0201] As can be seen from the data shown in Example 1 and Comparative Example 4, Comparative Example 4 uses MPN-coated aramid fibers instead of modified aramid fibers. Since the surface of the MPN-coated aramid fibers does not have an itaconic anhydride modified structure, the interfacial interaction between the MPN-coated aramid fibers and the rubber matrix and other components is weak, resulting in insufficient reinforcement and stabilization effect on the cell walls. Consequently, the expansion ratio, compressive strength and lap shear strength of the welding adhesive are all lower than those in Example 1.

[0202] As shown by the data in Example 1 and Comparative Example 5, in Comparative Example 5, unmodified ethylene bis-stearamide was used to replace the composite amide wax. Ethylene bis-stearamide mainly plays a conventional lubricating and dispersing role, and it is difficult to take into account functions such as interfacial compatibility, cell control and structural stability. The synergistic effect of each component in the system is weakened, the stability of cell formation and growth decreases, resulting in a decrease in the expansion ratio of the solder adhesive, an increase in the average cell size, and a decrease in compressive strength and lap shear strength.

[0203] As can be seen from the data shown in Example 1 and Comparative Example 6, when no modified aramid fiber is added to Comparative Example 6, the system lacks a fiber-reinforced skeleton and a supporting and stabilizing effect on the cell structure. During the expansion process, the cells are more prone to bubbling, collapse, or local instability, resulting in an increase in cell size after the welding adhesive expands, and a significant decrease in expansion ratio, compressive strength, and lap shear strength.

[0204] Data from Example 1 and Comparative Example 7 show that: without the addition of composite amide wax, the processing fluidity, component dispersibility and interface control ability of the system in Comparative Example 7 decreased, resulting in a decrease in the expansion ratio of the solder adhesive, an increase in the average cell size, and a decrease in compressive strength and lap shear strength.

[0205] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A high-expansion welding adhesive, characterized in that, The raw materials include the following parts by weight: 100 parts of EPDM rubber, 4-6 parts of functionalized thermal expansion microspheres, 1-2 parts of modified aramid fiber, 3-5 parts of composite amide wax, 10-20 parts of calcium carbonate, 10-12 parts of paraffin oil, 5-8 parts of azodicarbonamide, and 0.2-0.4 parts of peroxide.

2. The ultra-high expansion welding adhesive according to claim 1, characterized in that, The preparation method of the functionalized thermally expandable microspheres includes the following steps: A1. Add the thermally expanded microspheres to the mixed solvent, add polycaprolactone, stir until uniform, then add deionized water, continue stirring until uniform, filter, wash and dry to obtain PCL-coated thermally expanded microspheres. A2. Tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane were added to the mixed solution, the pH of the system was adjusted to 4-5, and the reaction was stirred. Then the pH of the system was adjusted to 7-8, PCL-coated thermal expansion microspheres and nano zinc oxide were added, and the reaction was stirred again. After the reaction was completed, the functionalized thermal expansion microspheres were obtained by filtration, washing and drying.

3. The ultra-high expansion welding adhesive according to claim 2, characterized in that, In step A1, the mass ratio of thermally expanded microspheres, polycaprolactone, and mixed solvent is 10:1.5-2:90-100.

4. The ultra-high expansion welding adhesive according to claim 2, characterized in that, In step A2, the mass ratio of PCL-coated thermally expandable microspheres, tetraethyl orthosilicate, γ-glycidyl etheroxypropyltrimethoxysilane, nano zinc oxide, and the mixed solution is 10:0.3-0.5:0.6-1:0.5-1:80-100.

5. The ultra-high expansion welding adhesive according to claim 1, characterized in that, The method for preparing the modified aramid fiber includes the following steps: B1. Short-cut aramid fibers are activated by adding NaOH aqueous solution. After activation, the fibers are filtered, washed, and dried to obtain activated aramid fibers. B2. Mix activated aramid fibers and deionized water, add tannic acid, stir evenly, adjust the pH of the system to 7-8, add ferric chloride aqueous solution, stir to react, after the reaction is completed, complete one deposition cycle, repeat the deposition cycle 2-3 times, filter, wash and dry to obtain MPN coated aramid fibers. B3. Under nitrogen protection, MPN-coated aramid fibers were added to anhydrous toluene, along with itaconic anhydride, triethylamine, and hydroquinone. The mixture was stirred and reacted. After the reaction was completed, the fibers were filtered, washed, and dried to obtain modified aramid fibers.

6. The ultra-high expansion welding adhesive according to claim 5, characterized in that, In step B1, the mass ratio of chopped aramid fibers to NaOH aqueous solution is 1:15-20. In step B2, the mass ratio of activated aramid fiber to deionized water is 1:40-50. In each deposition cycle, the mass of tannic acid added is 5-10% of the mass of the activated aramid fiber, and the mass of ferric chloride hexahydrate added is 2-3% of the mass of the activated aramid fiber. In step B3, the mass ratio of MPN-coated aramid fiber, itaconic anhydride, triethylamine, hydroquinone, and anhydrous toluene is 10:1-2:0.3-0.5:0.005-0.01:80-100.

7. The ultra-high expansion welding adhesive according to claim 1, characterized in that, The preparation method of the composite amide wax includes the following steps: After heating and melting ethylene bis-stearamide, maleic anhydride and vinyltrimethoxysilane were added and stirred until completely dissolved. Then, dicumyl peroxide was added and stirred to react. After the reaction was completed, the mixture was cooled and solidified. After crushing, washing, drying, grinding and sieving, a composite amide wax was obtained.

8. The ultra-high expansion welding adhesive according to claim 7, characterized in that, The mass ratio of ethylene bis-stearamide, maleic anhydride, vinyltrimethoxysilane, and dicumyl peroxide is 100:5-8:3-5:1-1.

5.

9. The ultra-high expansion welding adhesive according to claim 1, characterized in that, The peroxide is composed of a mixture of DCP and BIPB in a mass ratio of 1-1.5:

1.

10. A preparation process for the ultra-high expansion solder adhesive according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Add EPDM rubber to a mixer for plasticizing, then add compound amide wax, paraffin oil and calcium carbonate in sequence, mix evenly, discharge the rubber after mixing, and then re-mix and sheet it on a two-roll mill. After sheeting, let it stand at room temperature to obtain the masterbatch. S2. Wrap the masterbatch on the rollers of the open mill, and add functionalized thermal expansion microspheres, modified aramid fiber, azodicarbonamide and peroxide in sequence. After thinning and uniformly extruding, the mixture is sheeted to obtain the compound. S3. Calender the compounded rubber into sheets, cool and cut them to obtain ultra-high expansion welding adhesive.

Images