Low-density strong-viscous-force expansive structure reinforcing film and preparation method thereof

Abstract

The invention relates to the technical field of automobile manufacturing, and discloses a low-density strong-viscous-force intumescent structure reinforcing rubber sheet and a preparation method thereof, and the reinforcing rubber sheet comprises the following components: rubber, carbon black, a vulcanizing activator, hydrogenated petroleum resin, a plasticizer, a powder filler, epoxy resin, a curing agent, a foaming agent, sulfur and other rubber additives. The preparation method comprises the following steps: mixing the rubber, the carbon black, the vulcanizing activator, the hydrogenated petroleum resin, the plasticizer and the powder filler to prepare a rubber master batch; kneading the rubber master batch with epoxy resin, a powder filler, a curing agent, a foaming agent, sulfur and other auxiliaries to form a rubber material; and after being extruded and compounded and attached to glass fiber cloth and isolation paper, the mixture is compacted and cut into sheets. According to the invention, the reinforcing ratio, the foaming ratio and the initial bonding force are obviously improved, and the balance of light weight and high strength is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile manufacturing, and particularly to an expandable structural reinforcing film with low density and strong adhesion and a preparation method thereof. Background Art

[0002] With the rapid development of the automobile industry, lightweighting has become one of the main trends in automobile design. By reducing the vehicle body weight, not only can fuel consumption and carbon emissions be effectively reduced, but also the acceleration performance of the automobile can be improved. However, in order to achieve the lightweighting goal, the method of reducing the thickness of steel plates is often adopted, but this way brings problems such as a decrease in body stiffness, a weakening of the dent resistance performance, and the generation of noise and resonance in parts such as doors and roofs. These defects seriously affect the safety, comfort and overall performance of the automobile.

[0003] In this context, as a structural reinforcing material, the reinforcing film is gradually applied to large-area sheet metal parts such as doors, roofs, and hoods. The existing reinforcing films are mainly based on epoxy resin and enhance the local rigidity after curing. However, the existing reinforcing films generally have problems such as a fixed thickness and insufficient foaming ratio, resulting in limited effects on automobile lightweighting. At the same time, during the production process, since the vehicle body surface is usually attached with oil, the existing reinforcing films have poor adhesion performance in an oil surface environment and are likely to fall off during processes such as high-temperature baking and electrophoresis, which not only affects the production efficiency but also may damage the equipment.

[0004] Therefore, there is an urgent need for a new type of reinforcing film with a high foaming ratio, high adhesion performance, and the ability to adapt to complex production processes to solve the deficiencies of the existing technology and meet the dual requirements of the automobile industry for lightweighting and high performance. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the present invention provides an expandable structural reinforcing film with low density and strong adhesion and a preparation method thereof, which solves the problems of insufficient foaming ratio, poor adhesion performance, and poor lightweighting effect of the existing reinforcing films.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: On the one hand, the present invention provides an expandable structural reinforcing film with low density and strong adhesion. By selecting specific components and optimizing the proportions, it solves the problems of fixed thickness, low reinforcement ratio, limited lightweighting effect, and unsatisfactory adhesion in complex working conditions of the existing reinforcing films. While maintaining high-strength reinforcement performance, the present invention significantly reduces the film density, achieving the dual effects of lightweighting and strong adhesion.

[0007] The reinforcing film of the present invention is composed of the following components in parts by weight: 100-300 parts of rubber, 20-40 parts of carbon black, 1-10 parts of vulcanization activator, 10-30 parts of hydrogenated petroleum resin, 10-30 parts of plasticizer, 200-400 parts of powder filler, 200-400 parts of epoxy resin, 1-10 parts of curing agent, 1-10 parts of foaming agent, 1-10 parts of sulfur, and 1-10 parts of other rubber auxiliaries.

[0008] First, through the specific ratio of rubber and epoxy resin, the organic combination of flexibility and rigidity is achieved. After foaming, the two form an interpenetrating network structure (IPN). This structure not only ensures a high reinforcement ratio but also endows the film with higher toughness and durability. Rubber provides the basic flexibility and elasticity to adapt to structural deformation under different working conditions, while epoxy resin provides high strength and chemical stability to enhance the reinforcement effect.

[0009] Second, as a reinforcing agent, carbon black acts synergistically with the powder filler to enhance the strength of the pore walls after foaming, enabling the film to still maintain good mechanical properties at a high foaming ratio. The carbon black particles are evenly distributed in the matrix to form physical cross-linking points, which not only improve the wear resistance and tear resistance but also effectively enhance the overall rigidity and stability of the film.

[0010] Third, the foaming agent releases gas through heating to form a uniform microporous structure, significantly reducing the density of the film while optimizing the reinforcement ratio. By precisely adjusting the dosage of the foaming agent and the reaction conditions, the synchronization of the foaming process and the film curing process is ensured, avoiding problems such as pore wall collapse or uneven foaming.

[0011] In addition, the introduction of the powder filler significantly improves the cost-effectiveness of the reinforcing film, and further enhances the pore wall strength through its role in distributing in the pore walls after foaming. The selection of fillers such as calcium carbonate and talcum powder ensures that the film has excellent mechanical properties while being lightweight.

[0012] The combination of hydrogenated petroleum resin and plasticizer optimizes the processing performance and initial adhesion of the matrix material, ensuring excellent adhesion effect of the film under complex working conditions. The introduction of sulfur and vulcanization activator realizes the efficient vulcanization of rubber, enhancing the elasticity and anti-aging performance of the film. The use of other rubber auxiliaries (such as imidazole compounds) further accelerates the vulcanization and curing processes, improving the production efficiency.

[0013] Preferably, the rubber in the present invention is selected from one or a mixture of several of nitrile rubber (NBR), styrene-butadiene rubber (SBR), butyl rubber (IIR), natural rubber (NR), ethylene-propylene rubber (EPDM), or ethylene-vinyl acetate copolymer (EVA); Among them, nitrile rubber is widely used in scenarios requiring strong chemical resistance due to its good oil resistance and wear resistance; styrene-butadiene rubber can significantly improve mechanical properties when compounded with other rubbers due to its excellent processing performance and cost-effectiveness; butyl rubber has excellent airtightness and anti-aging properties, which can enhance the durability of the film; natural rubber provides good mechanical properties for the matrix due to its high elasticity and strong tear resistance; ethylene-propylene rubber is very suitable for high-temperature working conditions due to its excellent weather resistance and heat resistance; ethylene-vinyl acetate copolymer further improves the processing and application properties of the film by enhancing toughness and thermoplasticity.

[0014] Through the optimized combination of the above rubbers, the flexibility, strength and processing characteristics of the film can be flexibly adjusted according to application requirements, significantly improving the overall performance of the film, especially showing excellent adaptability in lightweight structures that require both high reinforcement performance and high adhesion.

[0015] Preferably, the powder filler in the present invention is selected from one or more of calcium carbonate, talc powder, aluminum hydroxide, magnesium hydroxide, mica powder, bentonite or fumed silica, and the particle size range of the powder filler is 3 - 50 μm. By selecting specific types and particle sizes of powder fillers, the mechanical properties, processing properties and cost-effectiveness of the film are further optimized.

[0016] As a widely used filler, calcium carbonate has the characteristics of low cost and good dispersibility, which can improve the rigidity of the film and at the same time improve the processing fluidity of the rubber compound; due to its flaky structure, talc powder can effectively enhance the crack resistance and deformation resistance of the composite material; aluminum hydroxide and magnesium hydroxide not only increase the strength of the film as fillers, but also endow it with certain flame retardant properties; mica powder can enhance the temperature resistance and electrical insulation of the film by virtue of its excellent heat resistance and insulation properties; bentonite can further optimize the dispersion uniformity of the rubber compound due to its good adsorption and lubrication properties; fumed silica, with its nano-scale particle characteristics, significantly improves the reinforcement effect and surface smoothness of the film.

[0017] Controlling the filler particle size within the range of 3 - 50 μm can form a uniform dispersion structure in the film, ensuring good interfacial bonding force between the filler and the matrix material. During the foaming process, these powder fillers are evenly distributed in the pore walls, providing effective support for the microporous structure, not only improving the pore wall strength but also avoiding pore wall collapse, thus ensuring the structural stability and high reinforcement ratio of the foamed film.

[0018] The preferred selection and particle size control of the above powder fillers enable the film to achieve lightweight and optimized production costs while maintaining high performance.

[0019] Preferably, the epoxy resin in the present invention is selected from one or more of DER-331, DER-330, CYD-128, EP-4200 or NPEL-134. With their excellent adhesion properties, high strength and chemical stability, these epoxy resins play a core role in enhancing the structure of the reinforcing film.

[0020] Among them, DER-331 and DER-330 are bisphenol A epoxy resins, which have high molecular weight and good toughness, and can form a dense cross-linked network structure in the film matrix, providing excellent mechanical strength and durability; CYD-128 is easy to be uniformly mixed with the rubber matrix and fillers due to its low viscosity and good workability, ensuring the stability of the material processing process; As a high-performance epoxy resin, EP-4200 has excellent heat resistance and chemical resistance, which can significantly improve the thermal stability and corrosion resistance of the film; NPEL-134 has low viscosity and fast curing performance, which can optimize the forming efficiency of the film and further improve the adhesion performance.

[0021] Through the reasonable selection and compounding of the above epoxy resins, the hardness, strength and heat resistance of the film can be flexibly adjusted, ensuring that in the design of high reinforcement ratio and lightweight, the film can balance flexibility and rigidity, and meet the bonding and reinforcement requirements under complex working conditions.

[0022] Preferably, the blowing agent is one or more of azodicarbonamide, sulfonylhydrazide compounds or nitroso compounds. These blowing agents decompose by heating to release gas, forming a uniform microporous structure inside the film, achieving excellent effects of low density and high foaming ratio.

[0023] Azodicarbonamide is a commonly used blowing agent, which has the characteristics of moderate decomposition temperature (170-200 °C) and large gas release amount, and can generate a delicate and stable microporous structure; Sulfonylhydrazide compounds can decompose at a lower temperature (120-150 °C), which is especially suitable for scenarios that require a lower foaming temperature, and can improve the controllability of the foaming process; Nitroso compounds, with their advantages of fast decomposition rate and uniform gas release, can effectively avoid the collapse of the pore walls and ensure the integrity of the foaming structure.

[0024] By preferably selecting these blowing agents and reasonably compounding them, the foaming temperature, gas release amount and density and distribution of the cell structure can be flexibly adjusted according to specific process conditions. In the present invention, the synergistic effect of the blowing agent, epoxy resin and filler not only reduces the overall density of the film, but also ensures the strength of the pore walls after foaming, thus achieving the lightweight and high reinforcement ratio of the film.

[0025] Preferably, the curing agent is dicyandiamide or latent modified amine. These curing agents form a cured network with high crosslink density through chemical reactions with epoxy resins, and are key components to achieve high strength and high stability of the reinforcing film.

[0026] Dicyandiamide is a commonly used latent curing agent with a relatively high thermal activation temperature (180 - 220 °C). It has good compatibility with epoxy resins at room temperature, which can ensure the storage stability of the rubber compound during processing. Under high-temperature curing conditions, it can quickly react with epoxy resins to form a dense crosslinked structure; the latent modified amine further reduces the reaction activation temperature (120 - 160 °C) by introducing active groups, and at the same time increases the reaction rate, which can shorten the curing time and improve the processing efficiency.

[0027] In the present invention, the synergistic effect of the preferred curing agent with epoxy resins and fillers not only provides excellent structural strength, but also optimizes the synchronization of curing and gas release during the foaming process, avoiding problems such as pore wall collapse or incomplete foaming caused by uneven reactions. In addition, the delayed reaction characteristics of the latent curing agent endow it with good operating performance during the preparation, extrusion and lamination processes of the rubber compound.

[0028] Preferably, the other rubber additives are one or more of imidazole compounds, tertiary amine salts or organic ureas. These additives play important catalytic and promoting roles in the vulcanization of the rubber matrix and the curing of epoxy resins, effectively improving the processing efficiency and comprehensive properties of the film.

[0029] Imidazole compounds have excellent catalytic performance, can significantly reduce the curing activation energy of epoxy resins, accelerate the curing reaction, shorten the processing time, and at the same time improve the crosslink density of the cured product, thereby enhancing the mechanical properties of the reinforcing film; tertiary amine salts, as catalysts, mainly promote the ring-opening reaction of epoxy resins, and cooperate with imidazole compounds to further increase the reaction rate and efficiency; organic ureas effectively avoid local overheating phenomena that may occur during the reaction by regulating the reaction rate and the smoothness of heat release, ensuring the structural uniformity and stability of the film.

[0030] The reasonable selection and compounding of these additives not only enhance the interfacial bonding force between the rubber matrix and epoxy resins, but also optimize the synchronization of crosslinking reactions and gas release during the foaming process, ensuring the integrity of the pore wall structure after foaming and enhancing the overall strength and lightweight effect of the film.

[0031] On the other hand, the present invention provides a method for preparing a low-density and high-adhesion expandable structural reinforcing film, comprising the following steps: S1. Kneading: Add rubber, carbon black, vulcanization activator, hydrogenated petroleum resin, plasticizer and powder filler into the internal mixer according to the ratio. Control the internal mixing temperature at 100 - 130 °C and the mixing time at 5 - 10 minutes. Through the internal mixing operation, fully mix the rubber matrix with the filler to form a uniform masterbatch, providing a base material with stable performance for subsequent processes.

[0032] S2. Kneading: Add the above-mentioned masterbatch into the kneader, and successively add epoxy resin, powder filler, curing agent, foaming agent, sulfur and other rubber additives. Control the kneading temperature at 70 - 100 °C and the kneading time at 10 - 20 minutes. In this step, each component is further uniformly dispersed, and at the same time, the mixing uniformity of the base material is enhanced through heat and shear effects, ensuring the uniform distribution of the foaming agent and the curing agent, providing guarantee for subsequent foaming and curing reactions.

[0033] S3. Extrusion and composite lamination: Transfer the kneaded semi-finished rubber compound into the extruder for extrusion operation. The extrusion temperature is 80 - 120 °C, and control the thickness of the film within the range of 0.5 - 2 mm. At the same time, during the extrusion process, the film is laminated with fiberglass cloth and release paper, and the composite pressure is 2 - 8 MPa to ensure that the fiberglass cloth is evenly attached to the surface of the film. The preferred tension of the fiberglass cloth is 3 - 5 N, and the composite speed is controlled at 0.5 - 1.5 m / min to ensure the structural stability and lamination quality of the film.

[0034] S4. Compaction and cutting: Compact the sheet after extrusion and lamination through a pressure roller. Control the pressure of the pressure roller at 5 - 10 MPa, and cut the sheet into pieces by a cutting machine after compaction. This step can further improve the surface flatness of the sheet, ensure the thickness is consistent, and at the same time cut it into finished products that meet the specifications according to actual requirements.

[0035] The present invention provides a low-density and strong adhesion expandable structural reinforcing film and its preparation method. It has the following beneficial effects: 1. Through the reasonable compounding of epoxy resin and rubber matrix in the present invention, an interpenetrating network structure (IPN) is formed, significantly improving the reinforcement ratio and mechanical properties. The appropriate use of the foaming agent enables the film to form a uniform microporous structure after foaming, achieving a lightweight effect. This design effectively reduces the overall density of the material while maintaining high strength, meeting the requirements of automotive lightweighting.

[0036] 2. Through the synergistic effect of hydrogenated petroleum resin, plasticizer and epoxy resin in the present invention, the initial adhesion of the film to the oil-contaminated surface is significantly enhanced. Even under complex working conditions such as vibration and high temperature, the film can still maintain reliable adhesion performance. This advantage is especially suitable for welding, baking and electrophoresis processes in automotive manufacturing, avoiding the phenomenon of film detachment.

[0037] 3. In the present invention, through the powder filler and carbon black, not only the pore wall support performance is enhanced, but also the material cost is reduced. The high foaming ratio reduces the raw material usage per unit film, and at the same time improves the cost performance of the product. The overall design takes into account both high performance and low cost, which is conducive to large-scale industrial applications.

[0038] 4. In the present invention, the design of the foaming agent and the powder filler reduces the energy consumption and waste generation during the material processing. The lightweight design of the film can reduce the driving energy consumption of the vehicle and further reduce carbon emissions. This technology meets the requirements of energy conservation, emission reduction and environmental protection, and provides technical support for green manufacturing. Specific Embodiments

[0039] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0040] In order to better illustrate the technical solutions of the present invention, the low-density and strong adhesion expandable structural reinforcement film and its preparation method of the present invention will be described in detail below in combination with specific embodiments, but the present invention is not limited to the following embodiments.

[0041] Examples 1 to 5: Table 1 Raw materials and their weight parts in each example Example 1: Raw material composition Initial mixing stage: 100 parts of rubber, 25 parts of carbon black, 5 parts of vulcanization activator, 15 parts of hydrogenated petroleum resin, 20 parts of plasticizer, 85 parts of powder filler.

[0042] Final mixing stage: 180 parts of powder filler, 200 parts of epoxy resin (including 120 parts of CYD-128 and 80 parts of CYD-172), 5 parts of curing agent, 5 parts of foaming agent, 1 part of sulfur, 10 parts of other additives.

[0043] Preparation method 1. Kneading: Add the raw materials in the initial mixing stage to a kneading machine, with a kneading temperature of 110°C and a kneading time of 8 minutes to obtain a uniform masterbatch.

[0044] 2. Mixing: Add the masterbatch to a mixer, add the raw materials in the final mixing stage, with a mixing temperature of 90°C and a mixing time of 15 minutes to obtain a semi-finished rubber compound.

[0045] 3. Extrusion and Lamination: Transfer the rubber compound into an extruder. The extrusion temperature is 100 °C, the thickness of the film is controlled at 1 mm, and it is laminated and bonded with fiberglass cloth and release paper. The lamination pressure is 5 MPa, the tension of the fiberglass cloth is 4 N, and the lamination speed is 1 m / min to obtain a laminated sheet.

[0046] 4. Compaction and Cutting: Compact the laminated sheet through a pressure roller with a pressure of 7 MPa and cut it into sheets.

[0047] Example 2: It is basically the same as Example 1, except that the addition amount of epoxy resin is adjusted to 150 parts.

[0048] Example 3: It is basically the same as Example 1, except that the addition amount of rubber is adjusted to 200 parts.

[0049] Example 4: It is basically the same as Example 1, except that the addition amount of the blowing agent is adjusted to 3 parts.

[0050] Example 5: It is basically the same as Example 1, except that the blowing agent is not added.

[0051] To compare and verify the technical effects of the present invention, the following comparative examples were also prepared: Comparative Examples 1 - 2: Comparative Example 1: It is basically the same as Example 1, except that the epoxy resin only contains CYD - 128 and does not contain other types of epoxy resins.

[0052] Comparative Example 2: It is basically the same as Example 1, except that the epoxy resin only contains CYD - 172 and does not contain other types of epoxy resins.

[0053] Test Example 1: Perform performance tests on the film products prepared in Examples 1 - 5 and Comparative Examples 1 and 2 with reference to the industry standard "QC / T 851 - 2011 Reinforcing Films for Automobiles". The test items include: Reinforcement magnification at 1 mm deflection: Test the reinforcement magnification of the film at a deflection of 1 mm.

[0054] Reinforcement magnification at 2.5 mm deflection: Test the reinforcement magnification of the film at a deflection of 2.5 mm.

[0055] High - expansion magnification: Calculate the ratio of the thickness after foaming to the initial thickness to evaluate the lightweight effect of the film.

[0056] Initial adhesion: Test the adhesion of the film at the initial stage of bonding (unit: N / 25 mm).

[0057] The test results are shown in Table 2 as follows: Table 2 Performance test results of the reinforcing film for automobiles in Test Example 1 From the performance test data in Table 2, it can be obtained that: 1. Analysis of reinforcement ratio The reinforcement ratios of Example 1 and Example 2 at 1 mm and 2.5 mm deflections are 4.39 / 5.99 and 4.35 / 5.82 respectively, showing excellent reinforcement effects. This is due to the synergistic effect of epoxy resin and rubber matrix, forming an interpenetrating network structure (IPN). This structure provides rigidity through the high strength support of epoxy resin, while the rubber matrix endows a certain flexibility, making the reinforcement performance reach a relatively high level.

[0058] The reinforcement ratios of Example 3 and Example 5 are relatively low, especially for Example 5 (2.55 / 2.85). This is related to the reduction or even absence of the blowing agent dosage, resulting in an increase in the pore wall thickness after foaming, but a decrease in elasticity and structural reinforcement ratio.

[0059] The reinforcement ratio of Comparative Example 1 is the highest, reaching 5.05 / 6.03. This is because when only CYD-128 is used as the epoxy resin, a higher crosslinking network density is formed after curing. However, due to the lack of flexibility adjustment of other epoxy resins, the pore walls are too rigid, which instead reduces the comprehensive performance, especially the adhesion.

[0060] 2. Analysis of foaming ratio The foaming ratios of Example 1 and Example 2 are 242% and 243% respectively, showing a highly foamed and uniform pore structure. This is because the blowing agent forms stable air holes under the action of an appropriate amount of epoxy resin, while the powder filler provides support in the pore walls to ensure the strength and flatness of the pore walls.

[0061] The foaming ratios of Example 3 and Example 4 are 196% and 168% respectively, indicating that the foaming effect has weakened. The main reason is the reduction in the dosage of epoxy resin or blowing agent, resulting in insufficient gas release or unstable pore wall support structure.

[0062] The foaming ratio of Example 5 is only 102%. Since no blowing agent is added, the product mainly relies on the initial thickness to form the structure, significantly reducing the lightweight advantage.

[0063] The foaming ratio of Comparative Example 1 reached 260%, exceeding that of the examples. This is because CYD-128 forms a highly rigid network structure after curing, which can support a higher foaming ratio. However, this single epoxy resin results in overly hard pore walls, prone to brittleness problems, and poor comprehensive performance.

[0064] 2. Foaming ratio analysis The foaming ratios of Example 1 and Example 2 were 242% and 243% respectively, showing a highly foamed and uniform pore structure. This is because the blowing agent forms stable air holes under the action of an appropriate amount of epoxy resin, and at the same time, the powder filler provides support in the pore walls, ensuring the strength and flatness of the pore walls.

[0065] The foaming ratios of Example 3 and Example 4 were 196% and 168% respectively, indicating that the foaming effect weakened. The main reason is that the amount of epoxy resin or blowing agent decreased, resulting in insufficient gas release or an unstable pore wall support structure.

[0066] The foaming ratio of Example 5 was only 102%. Since no blowing agent was added, the product mainly relied on the initial thickness to form the structure, significantly reducing the lightweight advantage.

[0067] The foaming ratio of Comparative Example 1 reached 260%, exceeding that of the examples. This is because CYD-128 forms a highly rigid network structure after curing, which can support a higher foaming ratio. However, this single epoxy resin results in overly hard pore walls, prone to brittleness problems, and poor comprehensive performance.

[0068] The comprehensive analysis is as follows: In Example 1, through the compound use of epoxy resins, combined with the flexibility of the rubber matrix and the appropriate application of the blowing agent, a high-strength crosslinked network and a uniform microporous structure were formed, thus achieving an excellent comprehensive balance in terms of reinforcement ratio, foaming ratio, and bonding performance.

[0069] The blowing agent acts synergistically with the epoxy resin and the powder filler, not only optimizing the foaming ratio (lightweight effect), but also ensuring the strength and rigidity of the pore walls, avoiding brittleness problems. This dynamic balance is prominent in Example 1 and Example 2, while in Comparative Example 1, due to the single epoxy resin, the pore wall rigidity is too high, resulting in a significant decrease in the adhesion force.

[0070] Hydrogenated petroleum resin and plasticizer significantly enhanced the initial adhesion of the film to the oil-contaminated surface. Acting together with the interfacial bonding force formed by crosslinking with the epoxy resin, Example 1 and Example 5 are far superior to the comparative examples in terms of bonding performance.

[0071] Through the performance tests and mechanism analyses of the examples and comparative examples, it can be concluded that the present invention realizes the multiple balance of high reinforcement ratio, high foaming ratio and excellent adhesion performance through the compounding of various epoxy resins, the collaborative design of the rubber matrix, and the optimized combination of the foaming agent and the filler.

[0072] Comparative Examples 3-4: Comparative Example 3: It is basically the same as Example 1, except that the powder filler is not added and other components remain unchanged.

[0073] Comparative Example 4: It is basically the same as Example 1, except that the amounts of the vulcanization activator and sulfur are each reduced by 50% and other components remain unchanged.

[0074] Test Example 2: Perform performance tests on the film products prepared in Example 1 and Comparative Examples 3 and 4 with reference to the industry standard "QC / T 851-2011 Reinforcing Films for Automobile Use". The test items are the same as those in Test Example 1.

[0075] The test results are shown in Table 3: Table 3 Performance Test Results of Reinforcing Films for Automobile Use in Test Example 2 From the performance test data in Table 3, it can be obtained that: 1. Analysis of reinforcement ratio The reinforcement ratios of Example 1 at deflections of 1 mm and 2.5 mm are 4.39 and 5.99 respectively, showing excellent reinforcement performance. This is because the powder filler and the foaming agent act synergistically to form a uniform and stable pore wall structure, and at the same time, the interpenetrating network structure (IPN) of the epoxy resin and the rubber matrix provides a balance between strength and toughness.

[0076] The reinforcement ratios of Comparative Example 3 are significantly reduced, being 2.80 and 3.64 respectively. This is because the absence of the powder filler results in the lack of a support structure for the pore wall, and the overall reinforcement performance deteriorates.

[0077] The reinforcement ratios of Comparative Example 4 are 3.99 and 4.91 respectively. Although they are close to those of Example 1, there is still a certain gap. This indicates that the reduction in the amounts of the vulcanization activator and sulfur leads to insufficient crosslinking of the rubber matrix, affecting the toughness of the pore wall and the overall strength.

[0078] 2. Analysis of foaming ratio The foaming ratio of Example 1 is 242%, showing a high lightweight effect. This benefits from the appropriate use of the foaming agent, which forms a uniform and stable microporous structure under the combined action of the epoxy resin and the filler.

[0079] The foaming ratio of Comparative Example 3 was 210%, which was lower than that of Example 1. This was because the absence of the powder filler made the pore wall structure unstable, resulting in the collapse of air holes and a decrease in the foaming effect.

[0080] The foaming ratio of Comparative Example 4 was 240%, which was close to that of Example 1. This indicated that the effect of the foaming agent was basically reflected, but the insufficient vulcanization crosslinking reduced the toughness of the pore wall, affecting the overall performance of the pore wall.

[0081] 3. Initial Adhesion Analysis The initial adhesion of Example 1 was 14.70 N / 25 mm, showing excellent adhesion performance. This was because of the combined action of hydrogenated petroleum resin, plasticizer, and compounded epoxy resin, which enhanced the adhesion ability of the film on the oily surface.

[0082] The initial adhesion of Comparative Example 3 was 10.42 N / 25 mm, significantly lower than that of Example 1. The absence of the powder filler reduced the interfacial bonding strength of the film, and the adhesion performance deteriorated significantly.

[0083] The initial adhesion of Comparative Example 4 was 9.80 N / 25 mm, the lowest among the test samples. This indicated that the insufficient vulcanization crosslinking significantly affected the adhesion performance and toughness of the rubber matrix.

[0084] Comprehensive analysis is as follows: The powder filler not only provides the support structure of the pore wall but also enhances the interfacial bonding strength of the film. The absence of the powder filler will lead to a decrease in the pore wall strength, a reduction in the foaming ratio and the reinforcement ratio, and a significant deterioration in the adhesion performance.

[0085] The degree of vulcanization crosslinking directly affects the toughness and adhesion performance of the rubber matrix. Insufficient dosage of the vulcanizing agent will reduce the flexibility and durability of the pore wall, resulting in a decrease in the reinforcement ratio and the initial adhesion.

[0086] Example 1 achieved an excellent comprehensive performance balance among the reinforcement ratio, foaming ratio, and initial adhesion through the reasonable proportioning of the foaming agent, powder filler, and vulcanizing agent, and showed significant advantages especially in the fields of automotive lightweight and high-strength structure reinforcement.

[0087] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An expandable structural reinforcing film with low density and strong adhesion, characterized in that, Comprising the following components in parts by weight: 100 - 300 parts of rubber, 20 - 40 parts of carbon black, 1 - 10 parts of vulcanization activator, 10 - 30 parts of hydrogenated petroleum resin, 10 - 30 parts of plasticizer, 200 - 400 parts of powder filler, 200 - 400 parts of epoxy resin, 1 - 10 parts of curing agent, 1 - 10 parts of foaming agent, 1 - 10 parts of sulfur, and 1 - 10 parts of other rubber auxiliaries.

2. The expandable structural reinforcement film with low density and strong adhesion according to claim 1, wherein The rubber is one or a mixture of several of nitrile rubber, styrene - butadiene rubber, butyl rubber, natural rubber, ethylene - propylene rubber, or ethylene - vinyl acetate copolymer.

3. The expandable structural reinforcement film with low density and strong adhesion according to claim 1, characterized in that, The powder filler is one or several of calcium carbonate, talc powder, aluminum hydroxide, magnesium hydroxide, mica powder, bentonite, or fumed silica, and the particle size of the powder filler is 3 - 50 μm.

4. The expandable structural reinforcing film with low density and strong adhesion according to claim 1, characterized in that, The epoxy resin is one or several of DER - 331, DER - 330, CYD - 128, EP - 4200, or NPEL - 134.

5. The expandable structural reinforcement film with low density and strong adhesion according to claim 1, characterized in that The foaming agent is one or several of azodicarbonamide, sulfonyl hydrazide compounds, or nitroso compounds.

6. The expandable structural reinforcement film with low density and strong adhesion according to claim 1, wherein The curing agent is dicyandiamide or latent modified amine.

7. The expandable structural reinforcing film with low density and strong adhesion according to claim 1, characterized in that The other rubber auxiliaries are one or several of imidazole compounds, tertiary amine salts, or organic ureas.

8. A preparation method of an intumescent structural reinforcement film with low density and strong adhesion, which is used to prepare the intumescent structural reinforcement film with low density and strong adhesion according to any one of claims 1-7, characterized in that, Including the following steps: (1) Add rubber, carbon black, vulcanization activator, hydrogenated petroleum resin, plasticizer, and powder filler into a Banbury mixer, with the mixing temperature being 100 - 130 °C and the mixing time being 5 - 10 minutes to obtain masterbatch rubber. (2) Add the masterbatch rubber into a kneader, and successively add epoxy resin, powder filler, curing agent, foaming agent, sulfur, and other rubber auxiliaries. The kneading temperature is 70 - 100 °C and the kneading time is 10 - 20 minutes to obtain semi - finished rubber compound. (3) Transfer the semi - finished rubber compound to an extruder for extrusion. The extrusion temperature is 80 - 120 °C, and at the same time, it is compounded and laminated with fiberglass cloth and release paper. The compounding pressure is 2 - 8 MPa to obtain a composite sheet. (4) Compact the composite sheet through a pressure roller, with the pressure being 5 - 10 MPa, and cut it into sheets.

9. The preparation method of the low-density and high-adhesion intumescent structural reinforcement film according to claim 8, wherein, During the extrusion process, the thickness of the rubber sheet is controlled at 0.5 - 2 mm.

10. The preparation method of the low-density and high-adhesion intumescent structural reinforcement film according to claim 8, characterized in that, During the compounding and laminating process, the tension of the fiberglass cloth is 3 - 5 N, and the compounding speed is 0.5 - 1.5 m / min.

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