Epoxy composite foam material for cavity filling enhancement of automobiles and preparation method thereof

Abstract

The application provides an epoxy composite foaming material for cavity filling enhancement of an automobile and a preparation method thereof. The material is composed of an epoxy resin, a chemical foaming agent, a short-cut reinforcing fiber, a composite functional filler, a damping modifier and a curing agent. The innovation is that the composite functional filler is a core-shell hollow microsphere with a flaky structure of mica and the like grown in situ on the surface, and has a bimodal particle size distribution. The structure can efficiently dissipate wideband acoustic vibration energy. The material is provided in the form of a preformed particle with a core-shell structure, wherein the core contains an epoxy resin, a curing agent and a functional filler, and the shell layer contains an epoxy resin, a foaming agent, a fiber and a damping agent. During preparation, a double screw extrusion process is used. During application, the particles are filled into the cavity of the automobile, and after baking, foaming and curing, a lightweight high-strength integral filling body conforming to the cavity is formed, which significantly improves the NVH performance and structural stiffness of the automobile.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials, specifically to an epoxy composite foam material for reinforcing automotive cavity filling and its preparation method. Background Technology

[0002] As the automotive industry moves towards electrification, lightweighting, and high-end products, vehicle noise, vibration, and harshness (NVH) performance has become one of the core indicators for measuring the quality of a vehicle's ride. Cavities in the vehicle body structure (such as A / B / C pillars, sill beams, and longitudinal beams) are weak areas with significant noise transmission and structural vibration amplification effects. Effectively filling and reinforcing these cavities is crucial for blocking noise propagation paths, suppressing structural resonance, and improving vehicle body rigidity.

[0003] Traditional cavity treatment technologies mainly fall into two categories. One category is passive filling materials, such as sound-absorbing pads, foam blocks, or expanding films based on asphalt, rubber, or olefin polymers. While these materials offer some sound insulation or vibration absorption, their bonding with metal panels largely relies on adhesives, leading to a risk of aging and detachment over long-term use, and their direct contribution to the vehicle body's structural rigidity is negligible. The other category is on-site foaming filling technology, typically using materials such as polyurethane (PU). This expands and fills the cavity, achieving good sealing and a certain degree of reinforcement. However, polyurethane foam has relatively limited mechanical strength, heat resistance, and long-term dimensional stability. Its foaming process is sensitive to humidity and temperature, resulting in poor process controllability. Furthermore, most polyurethane products have limited functionality, making it difficult to simultaneously meet multiple requirements such as high sound insulation, high damping, and excellent structural reinforcement.

[0004] In recent years, epoxy resin-based foam materials have been considered a more promising high-end solution due to their excellent adhesive strength, high modulus, good chemical resistance, and designable reactivity. Existing technologies have attempted to combine epoxy resin with foaming agents, fibers (such as carbon fiber and glass fiber), or lightweight fillers (such as hollow glass microspheres) for use as structural fillers or core materials in sandwich structures. However, these solutions still face several bottlenecks: First, functional fillers (such as microspheres and fibers) in simple physical blends are prone to uneven distribution or damage to the cell structure during foaming, leading to unstable performance; second, to balance storage stability and rapid curing, latent curing systems are often used, but this presents a matching problem with the high-temperature activation window required by chemical foaming agents, resulting in complex process design; third, most existing epoxy foam materials have narrow sound absorption spectra, insufficient dissipation capacity for mid-to-high frequency noise, and limited damping performance, making it difficult to effectively suppress broadband vibrations.

[0005] Specifically, for automotive manufacturing processes, ideal cavity filling materials should possess the following characteristics: excellent storage and transportation stability to adapt to the parts supply chain; excellent workability to accommodate automated filling and compatibility with existing painting and baking processes; and multifunctional integration, meaning a single material can simultaneously achieve significant sound insulation and noise reduction, efficient damping and vibration reduction, and effective structural reinforcement. Currently, there is a lack of mature epoxy-based foam material solutions in the market and technical literature that can systematically and synergistically meet all of the above stringent requirements. Summary of the Invention

[0006] The technical problem to be solved: The purpose of this invention is to provide an epoxy composite foam material that combines ultra-long shelf life, excellent workability, and the ability to integrate broadband acoustic vibration control and structural reinforcement through the microstructure design of the material itself. Technical solution: An epoxy composite foam material for reinforcing automotive cavity filling, formed by foaming and curing a mixture comprising the following components in parts by weight: Epoxy resin: 90-100 parts; chemical foaming agent: 2-12 parts; chopped reinforcing fiber: 5-20 parts; composite functional filler: 15-45 parts; damping modifier: 8-20 parts; the curing agent is at least one of aliphatic amines, cycloaliphatic amines, aromatic amines or acid anhydrides, and its dosage is such that the equivalent ratio of active hydrogen groups in the curing agent to epoxy groups in the epoxy resin is (0.9-1.2):1; The composite functional filler comprises core-shell hollow microspheres with different average particle sizes and shell thicknesses.

[0007] Preferably, the damping modifier is a polyurethane prepolymer or an organosilicon-modified epoxy resin with a glass transition temperature between -20°C and 50°C.

[0008] Preferably, the composite functional filler is a core-shell hollow microsphere with a lamellar structure grown in situ on its surface; The core of the hollow microsphere is a glass or ceramic hollow sphere, and the shell is made of silicon dioxide, phenolic resin or aluminum oxide. The sheet-like structure is mica, boron nitride, or hydrotalcite nanosheets grown in situ on the surface of the shell. The core-shell hollow microspheres have a bimodal particle size distribution, wherein the first particle size distribution peak is 30-80 μm and the second particle size distribution peak is 10-30 μm.

[0009] Preferably, the sheet-like structure has an average sheet diameter of 0.5-5 μm, an average thickness of 50-500 nm, and a coverage of not less than 30% on the surface of the core-shell hollow microspheres.

[0010] Preferably, the chemical foaming agent is a composite foaming system comprising a first foaming agent and a second foaming agent; the first foaming agent is azodicarbonamide or 4,4'-oxobisbenzenesulfonyl hydrazine, the second foaming agent is p-toluenesulfonyl hydrazine or sodium bicarbonate, and the weight ratio of the first foaming agent to the second foaming agent is (1-2):1.

[0011] Preferably, the preformed particles of the epoxy composite foam material are cylinders with a core-shell structure. By weight percentage of the total particles, the core layer accounts for 65%-75% and contains the epoxy resin, curing agent and composite functional filler, and the shell layer accounts for 25%-35% and encapsulates the core and contains the epoxy resin, chemical foaming agent, chopped reinforcing fiber and damping modifier.

[0012] Preferably, the method for preparing the preformed particles includes the following steps: S1. Prepare the core mixture and the shell mixture separately; S2. Using a co-rotating twin-screw extruder and a covered die, the core mixture and the shell mixture are melted and conveyed through the main feeding system and the first side feeding system, respectively, while the chopped reinforcing fibers are added to the shell melt flow through the second side feeding system; S3. The preformed granules are obtained by coating co-extrusion, stretching, and pelletizing.

[0013] The extrusion processing temperature of the twin-screw extruder is 80℃-120℃; the feed weight ratio of the core mixture to the shell base mixture is (65-75):(25-35); the chopped reinforcing fibers are added after the shell material has basically melted.

[0014] Preferably, a method for filling a cavity structure in an automobile includes the following steps: S11. The preformed particles are filled into the cavity of the car body; S12. The filled car body is placed in a baking environment of 110°C to 170°C, so that the particles undergo foaming, bonding and complete curing processes, forming an integral filler of epoxy composite foam material that matches the shape of the car cavity in the car cavity.

[0015] Preferably, the ratio of the filling amount of the preformed particles to the volume of the vehicle cavity in step S11 is (1.2-2.0) kg / L.

[0016] Beneficial effects: The epoxy composite foam material of the present invention has the following advantages: This invention introduces core-shell hollow microspheres of different sizes and sheet-like fillers to form a composite functional filler, achieving multi-mechanism dissipation of sound waves and vibrations. Microspheres of different sizes can scatter sound waves of different frequencies, while sheet-like fillers increase the tortuosity of the sound wave path. The two work synergistically to significantly improve broadband sound insulation and sound absorption performance. In this invention, a damping modifier with a specific glass transition temperature is selected, which gives it a high loss factor in the common operating temperature range of automobiles, effectively converting mechanical vibration energy into heat energy. At the same time, its compatibility with epoxy resin ensures that the material achieves high damping without sacrificing overall strength and toughness. In this invention, a composite chemical foaming agent system (ADC / OBSH and TSH / sodium bicarbonate combination) is used. By utilizing the temperature difference of its decomposition, sequential foaming is achieved during the curing process. This makes it easy to construct a foam structure with a wider and more uniform pore size distribution in situ inside the material. This structure itself is an excellent lightweight sound insulation material and elastic support. The invention achieves an ultra-long storage period through physical isolation: the "chemical foaming agent" and the "curing agent" are isolated in the shell and core of the particles respectively, which physically prevents them from contacting and reacting during storage, thus solving the industry problem of short storage period and high transportation requirements for reactive foaming materials. In this invention, short-cut reinforcing fibers are pre-placed and fixed in the shell layer. During the final foaming, the fibers are carried to the cell wall as the shell layer expands, thereby ensuring the uniform distribution of reinforcing fibers in the final foam and the formation of a three-dimensional network structure, avoiding the problems of uneven fiber distribution or sedimentation during direct mixing. The solid particle form in this invention makes it highly fluid, facilitating automated metering and filling. It can fill complex cavities without leaving any dead corners, and it avoids the leakage and contamination problems that may exist in liquid systems. In this invention, the side-feeding fiber and low-temperature extrusion process adds fibers after the shell material has basically melted, which protects the fiber length to the maximum extent, avoids excessive shearing damage, and ensures its reinforcement efficiency. The low-temperature extrusion process ensures that the foaming agent and curing agent do not react prematurely during the granulation process. The application method of this invention, which involves filling followed by integral foaming and curing, involves in-situ foaming, bonding, and curing of particles within the cavity. The foaming pressure causes the final filler to achieve an interference fit and microscopic interlocking with the inner wall of the cavity, resulting in an extremely strong bond. This not only provides a sealing and sound insulation effect but also acts as a reinforcing agent similar to structural adhesive, significantly improving the local stiffness and modal characteristics of the vehicle body. Detailed Implementation

[0017] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Example 1

[0018] An epoxy composite foam material for reinforcing automotive cavity filling is formed by foaming and curing a mixture comprising the following components in parts by weight: bisphenol A type epoxy resin E-51: 100 parts; chemical foaming agent: 5 parts; chopped reinforcing fiber: 12 parts; composite functional filler: 30 parts; damping modifier: 15 parts; curing agent is polyetheramine D230: 35 parts; The composite functional filler is a core-shell hollow microsphere with different average particle size and shell thickness.

[0019] Preferably, the damping modifier is a polyurethane prepolymer (brand name Adiprene® LFM-235).

[0020] Preferably, the composite functional filler is a core-shell hollow microsphere with mica nanosheets grown in situ on its surface. The core-shell hollow microsphere has a hollow glass microsphere as its core, which is coated with silica using a sol-gel method to form a shell, and mica nanosheets are grown in situ on the shell surface using a hydrothermal method. The core-shell hollow microsphere has a bimodal particle size distribution, with a first peak value of 50 μm and a second peak value of 10 μm. The average diameter of the mica nanosheets is 2 μm, the average thickness is 300 nm, and the coverage of the core-shell hollow microsphere surface is 50%.

[0021] Preferably, the chemical foaming agent is a composite foaming system comprising a first foaming agent 4,4'-oxobisbenzenesulfonyl hydrazine and a second foaming agent p-toluenesulfonyl hydrazine, with a weight ratio of 1:1.

[0022] Preferably, the preformed particles used to prepare the epoxy composite foam material are cylinders with a core-shell structure. By total particle weight percentage, the core layer accounts for 70%, comprising the epoxy resin, curing agent, and all of the composite functional fillers; the shell layer accounts for 30%, encapsulating the core layer, and comprising the epoxy resin, all of the chemical foaming agent, all of the chopped reinforcing fibers, and all of the damping modifier.

[0023] Preferably, the method for preparing the preformed particles includes the following steps: S1. Prepare the core mixture and the shell mixture separately; S2. Co-extrusion processing is performed using a co-rotating twin-screw extruder and an encapsulated die. The extrusion temperature is set to 100°C, and the core mixture and shell mixture are metered and melt-fed at a feed weight ratio of 70:30 through the main feeding system and the first side feeding system, respectively. After the shell material is substantially melted, the chopped reinforcing fibers are added to the shell melt stream through the second side feeding system. S3. The preformed granules are obtained by coating co-extrusion, stretching, and pelletizing.

[0024] Preferably, a method for filling a cavity structure in an automobile includes the following steps: S11. The preformed particles are filled into the cavity of the car body, and the ratio of the filling amount to the cavity volume is controlled to be 1.5 kg / L; S12. The filled car body is placed in a baking environment at 150°C, so that the particles undergo the process of foaming, bonding and complete curing, and finally form an integral filler of epoxy composite foam material that closely matches the shape of the cavity.

[0025] Example 2

[0026] An epoxy composite foam material for reinforcing automotive cavity filling is formed by foaming and curing a mixture comprising the following components in parts by weight: bisphenol F type epoxy resin NPEF-170: 95 parts; chemical foaming agent: 12 parts; chopped reinforcing fibers: 8 parts; composite functional filler: 25 parts; damping modifier: 10 parts; and methyltetrahydrophthalic anhydride as curing agent: 45 parts. The composite functional filler is a core-shell hollow microsphere with different average particle size and shell thickness.

[0027] Preferably, the damping modifier is an organosilicon-modified epoxy resin (brand name SY-409).

[0028] Preferably, the composite functional filler is a core-shell hollow microsphere with boron nitride nanosheets grown in situ on its surface. The core-shell hollow microsphere has a hollow ceramic microsphere as its core, which is coated with phenolic resin through in-situ polymerization to form a shell. Boron nitride nanosheets are then grown in situ on the surface of the shell using chemical vapor deposition. The core-shell hollow microsphere has a bimodal particle size distribution, with a first peak value of 60 μm and a second peak value of 20 μm. The average diameter of the boron nitride nanosheets is 1 μm, the average thickness is 100 nm, and the coverage of the core-shell hollow microsphere surface is 40%.

[0029] Preferably, the chemical foaming agent is a composite foaming system, comprising a first foaming agent, azodicarbonamide, and a second foaming agent, sodium bicarbonate, with a weight ratio of 2:1.

[0030] Preferably, the preformed particles used to prepare the epoxy composite foam material are cylinders with a core-shell structure. By total particle weight percentage, the core layer accounts for 68%, comprising the epoxy resin, curing agent, and all of the composite functional fillers; the shell layer accounts for 32%, encapsulating the core layer, and comprising the epoxy resin, all of the chemical foaming agent, all of the chopped reinforcing fibers, and all of the damping modifier.

[0031] Preferably, the method for preparing the preformed particles includes the following steps: S1. Prepare the core mixture and the shell mixture separately; S2. Co-extrusion processing is performed using a co-rotating twin-screw extruder and an encapsulated die. The extrusion temperature is set to 110°C, and the core mixture and shell mixture are metered and melt-fed at a feed weight ratio of 68:32 through the main feeding system and the first side feeding system, respectively. After the shell material is basically melted, the chopped reinforcing fibers are added to the shell melt stream through the second side feeding system. S3. The preformed granules are obtained by coating co-extrusion, stretching, and pelletizing.

[0032] Preferably, a method for filling a cavity structure in an automobile includes the following steps: S11. The preformed particles are filled into the cavity of the car body, and the ratio of the filling amount to the cavity volume is controlled to be 1.8 kg / L; S12. The filled car body is placed in a baking environment at 145°C, so that the particles undergo foaming, bonding and complete curing processes, and finally form an integral filler of epoxy composite foam material that closely matches the shape of the cavity.

[0033] Example 3

[0034] An epoxy composite foam material for reinforcing automotive cavity filling is formed by foaming and curing a mixture comprising the following components in parts by weight: hydrogenated bisphenol A type epoxy resin ST-3000: 100 parts; chemical foaming agent: 9 parts; chopped reinforcing fibers: 5 parts; composite functional filler: 40 parts; damping modifier: 18 parts; and isophorone diamine as curing agent: 28 parts. The composite functional filler is a core-shell hollow microsphere with different average particle size and shell thickness.

[0035] Preferably, the damping modifier is a polyurethane prepolymer (brand name Vibrathane® 8080).

[0036] Preferably, the composite functional filler is a core-shell hollow microsphere with hydrotalcite nanosheets grown in situ on its surface. The core-shell hollow microsphere has a vacuum glass microsphere as its core, coated with alumina using atomic layer deposition (ALD) to form a shell, and then magnesium aluminum hydrotalcite nanosheets are grown in situ on the shell surface using a hydrothermal method. The core-shell hollow microsphere has a bimodal particle size distribution, with a first peak value of 75 μm and a second peak value of 15 μm. The average diameter of the hydrotalcite nanosheets is 3 μm, the average thickness is 200 nm, and the coverage of the core-shell hollow microsphere surface is 60%.

[0037] Preferably, the chemical foaming agent is a composite foaming system comprising a first foaming agent 4,4'-oxobisbenzenesulfonyl hydrazine and a second foaming agent p-toluenesulfonyl hydrazine, with a weight ratio of 2:1.

[0038] Preferably, the preformed particles used to prepare the epoxy composite foam material are cylinders with a core-shell structure. By total particle weight percentage, the core layer accounts for 72%, comprising the epoxy resin, curing agent, and all of the composite functional fillers; the shell layer accounts for 28%, encapsulating the core layer, and comprising the epoxy resin, all of the chemical foaming agent, all of the chopped reinforcing fibers, and all of the damping modifier.

[0039] Preferably, the method for preparing the preformed particles includes the following steps: S1. Prepare the core mixture and the shell mixture separately; S2. Co-extrusion processing is performed using a co-rotating twin-screw extruder and an encapsulated die. The extrusion temperature is set to 95°C, and the core mixture and shell mixture are metered and melt-fed at a feed weight ratio of 72:28 through the main feeding system and the first side feeding system, respectively. After the shell material is substantially melted, the chopped reinforcing fibers are added to the shell melt stream through the second side feeding system. S3. The preformed granules are obtained by coating co-extrusion, stretching, and pelletizing.

[0040] Preferably, a method for filling a cavity structure in an automobile includes the following steps: S11. The preformed particles are filled into the cavity of the car body, and the ratio of the filling amount to the cavity volume is controlled to be 1.3 kg / L; S12. The filled car body is placed in a baking environment at 155°C, so that the particles undergo the process of foaming, bonding and complete curing, and finally form an integral filler of epoxy composite foam material that closely matches the shape of the cavity.

[0041] Example 4

[0042] The main difference between Example 4 and Example 1 is that the structure and ratio of the composite functional filler are different, while the composition, preparation method and filling method of the preformed particles are the same as in Example 1.

[0043] An epoxy composite foam material for reinforcing automotive cavity filling is formed by foaming and curing a mixture comprising the following components in parts by weight: bisphenol A type epoxy resin E-51: 100 parts; chemical foaming agent: 10.5 parts; chopped reinforcing fiber: 12 parts; composite functional filler: 35 parts; damping modifier: 15 parts; and curing agent is polyetheramine D230: 35 parts.

[0044] Preferably, the damping modifier is a polyurethane prepolymer (brand name Adiprene® LFM-235).

[0045] Preferably, the composite functional filler is a mixture of two types of surface-modified core-shell hollow microspheres. The first type of microsphere has an average particle size of 60 μm, with mica nanosheets grown on the surface of a silica shell, covering 30% and accounting for 60% of the total weight of the composite functional filler; the second type of microsphere has an average particle size of 15 μm, with boron nitride nanosheets grown on the surface of an alumina shell, covering 70% and accounting for 40% of the total weight of the composite functional filler. The average diameter of both the mica and boron nitride nanosheets is 2 μm.

[0046] Preferably, the chemical foaming agent is a composite foaming system, comprising a first foaming agent azodicarbonamide and a second foaming agent p-toluenesulfonyl hydrazine, with a weight ratio of 2:1.

[0047] Example 5

[0048] The main difference between Example 5 and Example 2 is that the damping system is different, while the composition, preparation method and filling method of the preformed particles are the same as in Example 2, wherein the core-shell ratio is 68:32.

[0049] An epoxy composite foam material for reinforcing automotive cavity filling is formed by foaming and curing a mixture comprising the following components in parts by weight: bisphenol F type epoxy resin NPEF-170: 95 parts; chemical foaming agent: 8 parts; chopped reinforcing fiber: 8 parts; composite functional filler: 25 parts; damping modifier: 12 parts; and methyltetrahydrophthalic anhydride as curing agent: 45 parts.

[0050] Preferably, the damping modifier is a mixture of silicone-modified epoxy resin (SY-409) and polyurethane prepolymer (Adiprene® LFM-235) in a 1:1 weight ratio.

[0051] Preferably, the composite functional filler is a core-shell hollow microsphere with boron nitride nanosheets grown in situ on its surface, and the specific parameters are the same as in Example 2.

[0052] Preferably, the chemical foaming agent is a composite foaming system, comprising a first foaming agent 4,4'-oxobisbenzenesulfonyl hydrazine and a second foaming agent sodium bicarbonate, with a weight ratio of 1:1.

[0053] Example 6

[0054] An epoxy composite foam material for reinforcing automotive cavity filling is formed by foaming and curing a mixture comprising the following components in parts by weight: 100 parts of bisphenol A type epoxy resin E-51; 15 parts of chemical foaming agent; 20 parts of chopped reinforcing fiber; 45 parts of composite functional filler; 8 parts of damping modifier; and 36.7 parts of polyetheramine D230 as curing agent.

[0055] Preferably, the damping modifier is a polyurethane prepolymer.

[0056] Preferably, the composite functional filler is a core-shell hollow microsphere with mica nanosheets grown on its surface, with an average particle size of 40 μm, a mica nanosheet coverage of ≥30%, and an average sheet diameter of 2 μm. Preferably, the chemical foaming agent is a composite foaming system comprising a first foaming agent, azodicarbonamide, and a second foaming agent, p-toluenesulfonyl hydrazine, in a weight ratio of 2:1.

[0057] Preferably, the preformed particles used to prepare the epoxy composite foam material are cylinders with a core-shell structure. By total particle weight percentage, the core layer accounts for 75%, comprising the epoxy resin, curing agent, and all of the composite functional fillers; the shell layer accounts for 25%, encapsulating the core layer, and comprising the epoxy resin, all of the chemical foaming agent, all of the chopped reinforcing fibers, and all of the damping modifier.

[0058] Preferably, the preparation method of the preformed particles is the same as in Example 1, wherein the feeding weight ratio is 75:25.

[0059] Preferably, a filling method for a car cavity structure is the same as in Example 1, wherein the filling ratio is 2.0 kg / L.

[0060] Example 7

[0061] An epoxy composite foam material for reinforcing automotive cavity filling is formed by foaming and curing a mixture comprising the following components in parts by weight: bisphenol F type epoxy resin NPEF-170: 90 parts; chemical foaming agent: 12 parts; chopped reinforcing fiber: 5 parts; composite functional filler: 15 parts; damping modifier: 20 parts; and methyltetrahydrophthalic anhydride as curing agent: 38 parts.

[0062] Preferably, the damping modifier is an organosilicon-modified epoxy resin.

[0063] Preferably, the composite functional filler is a core-shell hollow microsphere with boron nitride nanosheets grown on its surface, with an average particle size of 25 μm and parameters the same as in Example 2.

[0064] Preferably, the chemical foaming agent is a composite foaming system, comprising a first foaming agent 4,4'-oxobisbenzenesulfonyl hydrazine and a second foaming agent sodium bicarbonate, with a weight ratio of 1:2.

[0065] Preferably, the preformed particles used to prepare the epoxy composite foam material are cylinders with a core-shell structure. By total particle weight percentage, the core layer accounts for 65%, comprising the epoxy resin, curing agent, and all of the composite functional fillers; the shell layer accounts for 35%, encapsulating the core layer, and comprising the epoxy resin, all of the chemical foaming agent, all of the chopped reinforcing fibers, and all of the damping modifier.

[0066] Preferably, the preparation method of the preformed particles is the same as in Example 2, wherein the feeding weight ratio is 65:35.

[0067] Preferably, a filling method for a car cavity structure is the same as in Example 2, wherein the filling ratio is 1.2 kg / L.

[0068] Example 8

[0069] An epoxy composite foam material for reinforcing automotive cavity filling is formed by foaming and curing a mixture comprising the following components in parts by weight: 100 parts of phenolic epoxy resin DEN431; 6 parts of chemical foaming agent; 10 parts of chopped reinforcing fiber; 25 parts of composite functional filler; 12 parts of damping modifier; 2 parts of dicyandiamide as curing agent; and 0.5 parts of 2-methylimidazole as accelerator.

[0070] Preferably, the damping modifier is a polyurethane prepolymer (brand name Adiprene® LFM-235).

[0071] Preferably, the composite functional filler is a core-shell hollow microsphere with mica nanosheets grown on its surface, and the parameters are the same as in Example 1.

[0072] Preferably, the chemical foaming agent is 4,4'-oxobisbenzenesulfonylhydrazine.

[0073] Preferably, the preformed particles used to prepare the epoxy composite foam material are cylinders with a core-shell structure. By total particle weight percentage, the core layer accounts for 70%, comprising the epoxy resin, curing agent, accelerator, and all of the composite functional fillers; the shell layer accounts for 30%, encapsulating the core layer, and comprising the epoxy resin, all of the chemical foaming agent, all of the chopped reinforcing fibers, and all of the damping modifier.

[0074] Preferably, the method for preparing the preformed particles includes the following steps: S1. Prepare the core mixture and shell mixture separately; S2. Co-extrude using a co-rotating twin-screw extruder and a covered die. Strictly control the extrusion temperature to 85℃, and feed the core mixture and shell mixture at a weight ratio of 70:30, metering and melting them through the main feeding system and the first side feeding system respectively. After the shell material is basically melted, add the chopped reinforcing fibers to the shell melt stream through the second side feeding system; S3. The preformed granules are obtained by coating co-extrusion, stretching, and pelletizing.

[0075] Preferably, a method for filling a cavity structure in an automobile includes the following steps: S11. The preformed particles are filled into the cavity of the car body, and the ratio of the filling amount to the cavity volume is controlled to be 1.5 kg / L; S12. The filled car body is placed in a baking environment at 170°C, so that the particles undergo the process of foaming, bonding and complete curing, and finally form an integral filler of epoxy composite foam material that closely matches the shape of the cavity.

[0076] Comparative Example 1 The main difference between Comparative Example 1 and Example 1 is that the composite functional filler is a physical mixture of equal amounts (30 parts) of ordinary hollow glass microspheres (3M K1) and 500 mesh mica powder, does not contain a core-shell structure, and the sheet material does not grow in situ on the surface of the microspheres.

[0077] Comparative Example 2 The main difference between Comparative Example 2 and Example 1 is that the chemical foaming agent is a single azodicarbonamide, used in an amount of 12 parts, and does not contain a second foaming agent, thus not constituting a composite foaming system.

[0078] Comparative Example 3 The main difference between Comparative Example 3 and Example 1 is that the weight percentage of the core layer to the shell layer of the preformed particles is 50%:50%.

[0079] Comparative Example 4 The main difference between Comparative Example 4 and Example 1 is that, in the preparation process of the preformed particles, the chopped reinforcing fibers are premixed with other components of the shell in step S1, rather than being added in step S2 after the shell material has basically melted through a side-feeding system.

[0080] Comparative Example 5 The main difference between Comparative Example 5 and Example 1 is that the curing agent is methyl ethyl ketone peroxide, and the amount used is 5 parts. It is not an aliphatic amine, alicyclic amine, aromatic amine or acid anhydride curing agent, and it cannot react with epoxy resin in the active hydrogen equivalent ratio.

[0081] Comparative Example 6 The main difference between Comparative Example 6 and Example 1 is that in the automobile cavity filling method, the ratio of the filling amount of preformed particles to the volume of the automobile cavity is 0.8 kg / L.

[0082] Comparative Example 7 The main difference between Comparative Example 7 and Example 1 is that the epoxy resin was replaced with an equal amount (100 parts) of polyurethane prepolymer (Adiprene® LFM-235), and the curing agent was replaced with 10 parts of 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) to form a pure polyurethane foam material system.

[0083] Performance testing: Test Example 1 NVH performance Sound insulation performance: Referring to GB / T 19889.3, the reverberation chamber method was used to test the weighted sound insulation (Rw) of the sample in the 1 / 3 octave band of 100-3150 Hz; Damping performance: Referring to ASTM D4065, the peak loss factor and effective damping temperature range (tanδ>0.3) of the sample were measured using a dynamic thermomechanical analyzer at a frequency of 10 Hz and a temperature range of -30℃ to 80℃; Sound absorption coefficient: Referring to GB / T 18696.1, the standing wave tube method was used to test the average sound absorption coefficient of the sample in the frequency range of 500-4000 Hz.

[0084] Test Example 2 Mechanical and structural reinforcement properties Compressive strength (10% deformation): Refer to GB / T 8813; Flexural strength / modulus: Refer to GB / T 9341, simulating the local reinforcement effect of the filler on the cavity; Density: Refer to GB / T 6343.

[0085] Test Example 3 Thermal properties and stability Thermal conductivity: Refer to GB / T 10295, average temperature 25℃; Heat distortion temperature (HDT): Refer to GB / T 1634.2 (0.45 MPa); Dimensional stability (70°C, 48h): Refer to GB / T 8811.

[0086] Test Example 4 Process and application performance Granule storage stability: The pre-formed granules were stored in a 40℃ oven for 30 days, and the changes in their foaming ratio and curing performance were tested.

[0087] Bond strength between filler and steel plate: Refer to GB / T 7124 to simulate the bonding force between filler and vehicle body steel plate.

[0088] Performance retention rate after high temperature and high humidity aging (85°C / 85% RH, 240h): The retention rate of compressive strength and sound insulation after aging is tested.

[0089] Table 1

[0090] Table 2

[0091] As can be seen from Tables 1 and 2, Examples 1-8 demonstrate comprehensive performance, with excellent sound insulation, generally exceeding 36 decibels; strong vibration damping capabilities, high damping values, and effective operation over a wide temperature range. Furthermore, they are robust, heat-resistant, and adhere exceptionally well to the vehicle's steel panels. Comparative Example 1 demonstrates that in-situ growth of lamellar core-shell microspheres is indispensable for achieving acoustic and thermal insulation properties; Comparative Example 2 demonstrates that the composite foaming agent system is the foundation for forming a uniform cell structure and ensuring comprehensive performance; Comparative Example 3 demonstrates that pre-formed particles with a specific core-shell ratio are key to ensuring material storage stability and process reproducibility; Comparative Example 4 demonstrates that the lateral fiber feeding process is crucial for achieving effective fiber reinforcement and ensuring mechanical strength; Comparative Examples 5 and 7 together demonstrate that the selection of epoxy resin and specific types of curing agents are necessary conditions for achieving the material's basic properties such as high strength, heat resistance, and strong adhesion, which cannot be replaced by other resins or curing systems; Comparative Example 6 demonstrates that an optimized filler ratio is a prerequisite for achieving full filling and maximizing the material's full performance; the material system of this invention not only has excellent performance indicators, but its pre-formed particle morphology also ensures excellent storage stability and ease of construction, and its curing process is perfectly compatible with the baking process of automotive production lines. Aging tests show that the material retains high performance and has the potential to meet the requirements of automotive lifecycle use.

[0092] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An epoxy composite foam material for reinforcing automotive cavity filling, characterized in that: Formed by foaming and curing a mixture comprising the following components in parts by weight: Epoxy resin: 90-100 parts; Chemical foaming agent: 2-12 parts; Chopped reinforcing fiber: 5-20 parts; Composite functional filler: 15-45 parts; Damping modifier: 8-20 parts; The curing agent is at least one of aliphatic amines, alicyclic amines, aromatic amines or acid anhydrides, and its dosage is such that the equivalent ratio of the active hydrogen groups in the curing agent to the epoxy groups in the epoxy resin is (0.9-1.2):1; The composite functional filler comprises core-shell hollow microspheres with different average particle sizes and shell thicknesses.

2. The epoxy composite foam material for reinforcing automotive cavity filling according to claim 1, characterized in that: The damping modifier is a polyurethane prepolymer or an organosilicon-modified epoxy resin with a glass transition temperature between -20℃ and 50℃.

3. The epoxy composite foam material for reinforcing automotive cavities according to claim 1, characterized in that: The composite functional filler is a core-shell hollow microsphere with a lamellar structure grown in situ on its surface. The core of the hollow microsphere is a glass or ceramic hollow sphere, and the shell is made of silicon dioxide, phenolic resin or aluminum oxide. The sheet-like structure is mica, boron nitride, or hydrotalcite nanosheets grown in situ on the surface of the shell. The core-shell hollow microspheres have a bimodal particle size distribution, wherein the first particle size distribution peak is 30-80 μm and the second particle size distribution peak is 10-30 μm.

4. The epoxy composite foam material for reinforcing automotive cavity filling according to claim 3, characterized in that: The sheet-like structure has an average sheet diameter of 0.5-5 μm, an average thickness of 50-500 nm, and a coverage of not less than 30% on the surface of the core-shell hollow microspheres.

5. The epoxy composite foam material for reinforcing automotive cavity filling according to claim 1, characterized in that: The chemical foaming agent is a composite foaming system, comprising a first foaming agent and a second foaming agent; the first foaming agent is azodicarbonamide or 4,4'-oxobisbenzenesulfonyl hydrazine, the second foaming agent is p-toluenesulfonyl hydrazine or sodium bicarbonate, and the weight ratio of the first foaming agent to the second foaming agent is (1-2):

1.

6. The epoxy composite foam material for reinforcing automotive cavity filling according to claim 1, characterized in that: The preformed particles of the material are cylinders with a core-shell structure. By weight percentage of the total particles, the core layer accounts for 65%-75% and contains the epoxy resin, curing agent and composite functional filler, while the shell layer accounts for 25%-35% and encapsulates the core and contains the epoxy resin, chemical foaming agent, chopped reinforcing fiber and damping modifier.

7. A method for preparing preformed particles according to claim 6, characterized in that: Includes the following steps: S1. Prepare the core mixture and the shell mixture separately; S2. Using a co-rotating twin-screw extruder and a covered die, the core mixture and the shell mixture are melted and conveyed through the main feeding system and the first side feeding system, respectively, while the chopped reinforcing fibers are added to the shell melt flow through the second side feeding system; S3. The preformed granules are obtained by coating co-extrusion, stretching, and pelletizing.

8. Wherein, the extrusion processing temperature of the twin-screw extruder is 80℃-120℃; the feed weight ratio of the core mixture to the shell base mixture is (65-75):(25-35); the chopped reinforcing fiber is added after the shell material has basically melted.

9. A method for filling a cavity structure in an automobile, characterized in that: Includes the following steps: S11. Fill the preformed particles of claim 7 into the cavity of the automobile body; S12. The filled car body is placed in a baking environment of 110°C to 170°C, so that the particles undergo foaming, bonding and complete curing processes, forming an integral filler of epoxy composite foam material that matches the shape of the car cavity in the car cavity.

10. The method for filling the cavity structure of an automobile according to claim 8, characterized in that: In step S11, the ratio of the filling amount of the pre-formed particles to the volume of the car cavity is (1.2-2.0) kg / L.

Images