High-temperature-resistant organosilicon foaming material with sandwich structure and preparation method of high-temperature-resistant organosilicon foaming material

Abstract

The invention relates to a high-temperature-resistant organosilicon foaming material with a sandwich structure and a preparation method thereof, and belongs to the technical field of polymer composite materials. The high-temperature-resistant organosilicon foaming material with the sandwich structure is of an integrated sandwich structure, comprises a core layer and skin layers arranged on the two sides of the core layer respectively, and specifically comprises an organosilicon resin matrix, a key functional compound, a fiber reinforcement body and a foaming and curing system. The preparation method comprises the following steps: step 1, pretreating the fiber reinforcement; 2, preparing core layer foaming slurry; step 3, preparing a skin layer impregnating resin and forming a prepreg; step 4, performing integrated compression molding on the sandwich structure; and step 5, post-curing. Through the sandwich structure design and the introduction of the key interface modifier, the synergistic improvement of light weight, high strength, flame retardance and supernormal high temperature resistance is realized.

Description

Technical Field

[0001] This invention relates to a foaming material and its preparation method, specifically to a high-temperature resistant sandwich structure organosilicon foaming material and its preparation method, belonging to the field of polymer composite materials technology. Background Technology

[0002] In recent years, with the rapid development of the aerospace industry, the demand for high-temperature resistant materials has been continuously increasing. Traditional high-temperature resistant materials (such as ceramics and metal alloys) have gradually revealed their limitations due to their high density and brittleness. High-polymer high-temperature resistant materials, such as silicone foam, have been widely used in aerospace, rail transportation, and building fire protection due to their excellent high and low temperature resistance, flame retardancy, hydrophobicity, and chemical stability. However, traditional silicone foam materials generally suffer from insufficient mechanical strength, rapid decline in dimensional stability and strength retention at high temperatures, and easy pulverization after long-term thermal aging, which limits their application in more advanced and demanding environments.

[0003] To improve its mechanical properties, existing technologies typically employ the addition of inorganic fillers (such as silica or glass microspheres) or blending with fibers (such as glass fibers or ceramic fibers). However, these methods have significant drawbacks: simple blending leads to uneven filler dispersion, creating stress concentration points at the foam cell walls, which may actually reduce toughness; the addition of large amounts of filler significantly increases material density, sacrificing its lightweight properties; simultaneously, the interfacial bonding between the filler and the silicone matrix is ​​insufficient, making it prone to interfacial debonding under long-term thermal shock or external forces, resulting in performance degradation.

[0004] Therefore, developing a novel composite material structure and preparation method that can significantly improve the mechanical strength and high-temperature durability of silicone foam while maintaining its lightweight and flame-retardant properties has become a pressing technical challenge in this field. Summary of the Invention

[0005] To overcome the above-mentioned defects of the prior art, the present invention provides a high-temperature resistant sandwich structure organosilicon foam material and its preparation method. Through innovative sandwich structure design and the introduction of key interface modifiers, the material achieves a synergistic improvement in lightweight, high strength, flame retardancy and ultra-high temperature resistance.

[0006] The technical solution adopted in this invention is: a high-temperature resistant sandwich-structured silicone foam material, wherein the material has an integrated sandwich structure, including a core layer and skin layers respectively disposed on both sides of the core layer, and specifically includes the following components: Organosilicon resin matrix: The organosilicon resin matrix is ​​vinyl silicone resin with a vinyl content of 0.5-1.2 wt% and a viscosity of 5000-20000 cP @25℃; Key functional compound: The key functional compound is 2-(1-phenylpiperidin-1-yl)acetic acid or its functional equivalent; Fiber reinforcement: The fiber reinforcement is a glass fiber fabric, including at least one of chopped strand mat, plain weave fabric or unidirectional fabric; Foaming and curing system: The foaming and curing system includes crosslinking agent, catalyst, foaming agent and optional additives; The outer layer is a continuous and dense reinforcing layer composed of the glass fiber fabric and the silicone resin matrix; the core layer is a porous foam layer formed by foaming the silicone resin matrix, in which the key functional compounds are uniformly dispersed.

[0007] Preferably, when it is an addition-curing system, the crosslinking agent in the core layer is a hydrogen-containing silicone oil, the catalyst is a platinum catalyst, and the core layer comprises the following components by mass: 100 parts of silicone resin matrix 0.5-10 parts of key functional compounds 5-100 parts of hydrogen-containing silicone oil 1-10 parts of foaming agent Platinum catalyst 0.001-0.05 parts.

[0008] Preferably, when it is a condensation curing system, the crosslinking agent in the core layer is an alkoxysilane, the catalyst is an organotin catalyst, and the core layer comprises the following components by mass: 100 parts of silicone resin matrix 0.5-10 parts of key functional compounds 1-10 parts of alkoxysilane 1-10 parts of foaming agent 0.1-2 parts of organotin catalyst.

[0009] Furthermore, the content of the key functional compound in the core layer is 2-5 parts by mass.

[0010] Preferably, the core layer further includes optional additives, which include at least one of the following: 0.01-0.5 parts of inhibitor, 1-20 parts of filler, 1-20 parts of flame retardant, or 0.1-5 parts of colorant.

[0011] Preferably, the areal density of the glass fiber fabric is 100-500 g / m².

[0012] Preferably, the glass fiber fabric and the silicone resin matrix in the skin layer are specifically combined in such a way that the glass fiber fabric is impregnated in the skin layer impregnated with resin, and the mass ratio of resin to skin layer is 0.3:1-0.6:1.

[0013] Preferably, when it is an addition-curing system, the crosslinking agent in the skin impregnation resin is a hydrogen-containing silicone oil, the catalyst is a platinum catalyst, and the skin impregnation resin comprises the following components by mass: 100 parts of silicone resin matrix 0-5 parts of key functional compounds 5-100 parts of hydrogen-containing silicone oil Platinum catalyst 0.001-0.05 parts.

[0014] Preferably, when it is a condensation curing system, the crosslinking agent in the skin impregnation resin is an alkoxysilane, the catalyst is an organotin catalyst, and the skin comprises the following components by mass: 100 parts of silicone resin matrix 0-5 parts of key functional compounds 1-10 parts of alkoxysilane 0.1-2 parts of organotin catalyst.

[0015] Preferably, the components in the skin layer further include optional additives, which include at least one of the following: 0.01-0.5 parts of inhibitor, 5-30 parts of filler, 1-20 parts of flame retardant, or 0.1-5 parts of colorant.

[0016] The preparation method of any of the high-temperature resistant sandwich structure organosilicon foam materials disclosed in this invention includes the following steps: Step 1: Pretreatment of fiber reinforcement; immerse the glass fiber fabric in a silane coupling agent ethanol solution, dry it, and set it aside for later use; Step 2: Preparation of core layer foaming slurry; premix the key functional compounds with part of the silicone resin matrix, and then add the remaining silicone resin matrix, crosslinking agent, foaming agent, catalyst and optional additives in sequence, and mix evenly; Step 3: Preparation of skin impregnation resin and molding of prepreg; premix the key functional compound with part of the silicone resin matrix, and then add the remaining silicone resin matrix, crosslinking agent, catalyst and optional additives in sequence, and mix evenly; impregnate the glass fiber reinforcement after the pretreatment in step 1 into the skin impregnation resin, and obtain a semi-cured skin prepreg after pregeling or pre-curing. Step 4: Sandwich structure integrated molding; In the preheated mold, the lower layer of prepreg is laid in sequence, the core layer foaming slurry is injected, and the upper layer of prepreg is laid. After the mold is closed and pressure is applied, the temperature is raised in stages to first foam the core layer and then solidify the whole structure before demolding. Step 5: Post-curing; The demolded product is subjected to post-curing treatment at 150-200℃ for 2-10 hours to obtain the high-temperature resistant sandwich structure silicone foam material.

[0017] Preferably, in step one, the concentration of the silane coupling agent ethanol solution is 1%-5%, the impregnation time is 5-20 minutes, the drying temperature is 80-120℃, and the drying time is 0.5-2 hours.

[0018] Preferably, in step two, the organosilicon prepolymer is at least one of vinyl silicone oil, methyl vinyl silicone resin, or hydroxyl-terminated polydimethylsiloxane.

[0019] Preferably, in step three, the pre-gel or pre-curing temperature is 60-100℃ and the time is 5-30 minutes.

[0020] Preferably, in step four, the formula for calculating the injection volume X of the core layer slurry is: X ≈ S * H ​​* D_c * k, Where S is the product area, H is the product thickness, D_c is the core layer target density, and k is the process coefficient, which ranges from 1.1 to 1.5.

[0021] Furthermore, in step four, the temperature during the foaming stage is 100-140℃, and the temperature during the curing stage is 140-180℃.

[0022] Furthermore, in step four, the molding pressure is 0.5-5 MPa.

[0023] The beneficial effects of this invention are: 1. This invention utilizes the additive 2-(1-phenylpiperidin-1-yl)acetic acid, which functions as both a molecular anchor and a heat stabilizer. Its carboxyl groups react with the hydroxyl groups on the glass fiber surface and the active groups in the silicone resin, while its rigid phenylpiperidin structure effectively embeds and anchors within the silicone polymer network. This fundamentally solves the problem of weak interfaces between glass fiber / resin and between foam pore walls / resin.

[0024] 2. Strong interfacial bonding, combined with the inherently good thermal stability of the functional compounds, delays the performance degradation caused by interfacial thermo-oxidative degradation at high temperatures. After long-term thermal aging at 250-350℃, the material exhibits significantly better strength retention and dimensional stability than the control group without added or using ordinary coupling agents.

[0025] 3. The sandwich structure of this invention fully utilizes the structural efficiency of the materials. The high-modulus, high-strength dense glass fiber skin bears the main load, while the low-density foam core maintains stiffness and reduces weight, giving the material extremely high specific strength and specific modulus.

[0026] 4. Adopting synchronous foaming-curing integrated molding technology, the skin layer and core layer are metallurgically bonded, with no adhesive layer and no weak interface layer, avoiding the risk of interlayer delamination of traditional adhesive sandwich panels, resulting in excellent product integrity and environmental reliability.

[0027] 5. The functional compound concept, sandwich structure and integrated molding approach proposed in this invention are applicable to various organosilicon curing systems (addition, condensation, etc.), various types of glass fiber reinforcements and different foaming processes, and have good process adaptability and scalability. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart illustrating one embodiment of the preparation method of the high-temperature resistant sandwich structure silicone foam material of the present invention. Figure 2 An optical microscope image of the sandwich-structured organosilicon foam material prepared in Example 1 of this invention; Figure 3 An optical microscope image of the sandwich-structured organosilicon foam material prepared in Example 2 of this invention; Figure 4 This is an optical microscope image of the organic material prepared in the comparative example of this invention; Figure 5 Electron microscope image of the sandwich-structured organosilicon foam material prepared in Example 1 of this invention; Figure 6 Electron microscope image of the sandwich-structured organosilicon foam material prepared in Example 2 of this invention; Figure 7 Electron microscope image of the organic material prepared in the comparative example of this invention; Figure 8 The image shows the combustion of the sandwich-structured organosilicon foam material prepared in Example 1 of this invention under an open flame. Figure 9 The image shows the combustion of the sandwich-structured organosilicon foam material prepared in Example 2 of this invention under an open flame. Figure 10 This is a combustion diagram of the organic material prepared in the comparative example of this invention under an open flame; Figure 11 The temperature change curve of the back side of the sandwich-structured silicone foam material prepared in Example 1 of this invention under an open flame at 850°C; Figure 12 The temperature change curve of the back side of the sandwich-structured silicone foam material prepared in Example 2 of this invention under an open flame at 850°C; Figure 13 The temperature change curve of the back side of the organic material prepared in the comparative example of this invention under an open flame at 850°C is shown. Detailed Implementation

[0029] This invention discloses a high-temperature resistant sandwich-structured silicone foam material. The material has an integrated sandwich structure, including a core layer and skin layers respectively disposed on both sides of the core layer. The sandwich structure fully utilizes the structural efficiency of the material. The high-modulus, high-strength dense glass fiber skin layer bears the main load, while the low-density foam core layer maintains stiffness and reduces weight, giving the material extremely high specific strength and specific modulus. Specifically, it comprises the following components: Organosilicon resin matrix: The organosilicon resin matrix is ​​vinyl silicone resin with a vinyl content of 0.5-1.2 wt% and a viscosity of 5000-20000 cP @25℃.

[0030] Key functional compound: The key functional compound is 2-(1-phenylpiperidin-1-yl)acetic acid or its functional equivalent. This compound acts as an interface enhancer and heat-resistant modifier, serving a dual role as a molecular anchor and a heat stabilizer. Its carboxyl group can react with the hydroxyl groups on the glass fiber surface and the active groups in the silicone resin, and its rigid phenylpiperidin structure can be effectively embedded and anchored in the silicone polymer network. This fundamentally solves the problem of weak interfaces between glass fiber / resin and between foam pore walls / resin.

[0031] The term "functional equivalents" refers to other compounds that, like 2-(1-phenylpiperidin-1-yl)acetic acid, can enhance interfacial adhesion and improve the thermal stability of composite materials through their rigid aromatic / heterocyclic structures and active functional groups (such as carboxyl, amino, hydroxyl, and epoxy groups) within the molecule, either between silicone resin and glass fiber or within the resin matrix of the foam pore walls. These compounds include, but are not limited to: other carboxylic acid derivatives containing phenylpiperidin structures, carboxylic acids or amines containing similar rigid heterocycles (such as quinoline, pyridine, imidazole, and triazole), and polycyclic aromatic hydrocarbon derivatives with strong polarity and reactive groups.

[0032] Fiber reinforcement: The fiber reinforcement is a glass fiber fabric, including at least one of chopped strand mat, plain weave fabric or unidirectional fabric.

[0033] Foaming and curing system: The foaming and curing system includes crosslinking agent, catalyst, foaming agent and optional additives.

[0034] The material has an integrated sandwich structure of a dense skin layer / a porous core layer / a dense skin layer. The skin layer is a continuous dense reinforcing layer composed of the glass fiber fabric and the silicone resin matrix. The core layer is a porous foam layer formed by foaming the silicone resin matrix, in which the key functional compounds are uniformly dispersed.

[0035] When it is an addition-curing system, the crosslinking agent in the core layer is hydrogen-containing silicone oil, and the catalyst is a platinum catalyst. The core layer comprises the following components by mass: 100 parts of silicone resin matrix 0.5-10 parts of key functional compounds 5-100 parts of hydrogen-containing silicone oil 1-10 parts of foaming agent Platinum catalyst 0.001-0.05 parts.

[0036] When it is a condensation curing system, the crosslinking agent in the core layer is an alkoxysilane, and the catalyst is an organotin catalyst. The core layer comprises the following components by mass: 100 parts of silicone resin matrix 0.5-10 parts of key functional compounds 1-10 parts of alkoxysilane 1-10 parts of foaming agent 0.1-2 parts of organotin catalyst.

[0037] Preferably, the content of the key functional compound in the core layer is 2-5 parts by weight. This preferred range is an experimentally verified optimal balance point that can fully exert its interface enhancement and heat resistance modification effects without causing performance degradation or process problems due to improper dosage.

[0038] The foaming agent is at least one of azodicarbonamide (AC), 4,4'-oxobis(benzenesulfonyl)hydrazine (OBSH), sodium bicarbonate, or physical foaming agent microspheres.

[0039] The core layer also includes optional additives, which include at least one of the following: 0.01-0.5 parts of inhibitor, 1-20 parts of filler, 1-20 parts of flame retardant, or 0.1-5 parts of colorant.

[0040] The inhibitor can be ethynylcyclohexanol. 0.01-0.5 parts of ethynylcyclohexanol can precisely control the curing and foaming sequence of the organosilicon system, ensuring the stability of the preparation process and the material properties.

[0041] The filler can be fumed silica. 1-20 parts of fumed silica can improve the mechanical strength of the material (such as tensile and flexural strength), improve the dispersibility and thixotropy of the resin system, prevent component sedimentation, and enhance the support stability of the core foam structure, thereby reducing deformation at high temperatures.

[0042] Flame retardants can be platinum compounds or aluminum hydroxide. 1-20 parts of flame retardant can give the material excellent flame retardant properties, meet the safety requirements of high-temperature resistant materials, reduce the risk of combustion in high-temperature use scenarios, and expand the application of materials in electrical, aerospace and other fields that require flame retardancy.

[0043] Colorant of 0.1-5 parts can meet the needs of material appearance differentiation, facilitate product identification, classification and application scenario adaptation, and improve product practicality and market adaptability.

[0044] The glass fiber fabric and the silicone resin matrix in the skin layer are specifically composited by impregnating the glass fiber fabric in the skin layer impregnated with resin. The mass ratio of resin to skin layer is 0.3:1-0.6:1, and the areal density of the glass fiber fabric is 100-500 g / m². This further ensures that the skin layer possesses excellent reinforcement and durability. Simultaneously, it allows the impregnation process to proceed smoothly, obtaining high-quality prepreg, which forms a strong integrated interface with the core layer during molding and foaming. Ultimately, the product achieves optimal performance in core properties such as lightweight, high-temperature resistance, and structural strength.

[0045] When it is an addition-curing system, the crosslinking agent in the skin impregnation resin is a hydrogen-containing silicone oil, and the catalyst is a platinum catalyst. The skin impregnation resin comprises the following components by mass: 100 parts of silicone resin matrix 0-5 parts of key functional compounds 5-100 parts of hydrogen-containing silicone oil Platinum catalyst 0.001-0.05 parts.

[0046] When the system is a condensation curing system, the crosslinking agent in the skin impregnation resin is an alkoxysilane, and the catalyst is an organotin catalyst. The skin comprises the following components by mass: 100 parts of silicone resin matrix 0-5 parts of key functional compounds 1-10 parts of alkoxysilane 0.1-2 parts of organotin catalyst.

[0047] The components of the skin layer also include optional additives, which include at least one selected from the following: 0.01-0.5 parts of inhibitor, 5-30 parts of filler, 1-20 parts of flame retardant, or 0.1-5 parts of colorant. Except for the filler content, the optional additives in the skin layer are the same as those in the core layer. Selecting this range for the filler in the skin layer can further optimize its performance.

[0048] like Figure 1 As shown, the present invention also discloses a method for preparing the high-temperature resistant sandwich-structured silicone foam material, comprising the following steps: Step 1: Pretreatment of fiber reinforcement: The glass fiber fabric is immersed in a silane coupling agent ethanol solution and dried for later use; the concentration of the silane coupling agent ethanol solution is 1%-5%, the immersion time is 5-20 minutes, the drying temperature is 80-120℃, and the drying time is 0.5-2 hours.

[0049] Specifically, the pretreatment includes: immersing the glass fiber in a 1%-5% ethanol solution of a silane coupling agent for 5-20 minutes, then drying it at 80-120°C for 0.5-2 hours. The areal density of the fiber reinforcement is 100-500 g / m². The silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane (KH550), γ-glycidoxypropyltrimethoxysilane (KH560), or γ-(methacryloyloxy)propyltrimethoxysilane (KH570).

[0050] Step 2: Preparation of core layer foaming slurry (organic silicone resin composition): The key functional compounds are premixed with a portion of the silicone resin matrix, and then the remaining silicone resin matrix, crosslinking agent, foaming agent, catalyst and optional additives are added in sequence and mixed evenly. Specifically, prepare and mix the materials according to the following weight proportions: Organosilicon prepolymer: 100 parts. Selected from at least one of vinyl silicone oil (viscosity 1000-10000 mPa·s), methyl vinyl silicone resin, or hydroxyl-terminated polydimethylsiloxane.

[0051] Functional compound: 0.5-10 parts, preferably 2-5 parts.

[0052] Crosslinking agent (first curing agent): Its dosage is determined by the functional groups of the organosilicon prepolymer. For addition curing systems, the first curing agent is hydrogen-containing silicone oil, and its addition amount is calculated based on the molar ratio of Si-H bonds to vinyl groups in the organosilicon prepolymer (Si-H:Vi) of (0.8-2.0):1, generally 5-100 parts; for condensation curing systems, the first curing agent is alkoxysilane (such as tetraethyl orthosilicate), and the addition amount is 1-10 parts of the organosilicon prepolymer.

[0053] Foaming agent: 1-10 parts.

[0054] Catalyst: For addition curing systems, a platinum catalyst is used, with an addition amount of 10-200 ppm of the organosilicon prepolymer, typically 0.001-0.05 parts, based on platinum metal; for condensation curing systems, an organotin catalyst (such as dibutyltin dilaurate) is used, with an addition amount of 0.1-2 parts of the organosilicon prepolymer. Optional additives: inhibitors (such as ethynylcyclohexanol, 0.01-0.5 parts), fillers (such as fumed silica, 1-20 parts), flame retardants (such as platinum compounds, aluminum hydroxide, 1-20 parts), colorants (0.1-5 parts).

[0055] During preparation, the functional compound is first premixed with a portion of the organosilicon prepolymer or inert solvent to ensure its dispersion or dissolution, and then mixed uniformly with other components in sequence.

[0056] Step 3: Preparation of the skin impregnation resin and molding of the prepreg: The key functional compound is premixed with a portion of the silicone resin matrix, and then the remaining silicone resin matrix, crosslinking agent, catalyst and optional additives are added in sequence and mixed evenly. The glass fiber reinforcement after the pretreatment in step one is impregnated with the skin impregnation resin, and a semi-cured skin prepreg is obtained after pregeling or pre-curing. The pregeling or pre-curing temperature is 60-100℃ and the time is 5-30 minutes.

[0057] Specifically, the preparation of the skin impregnation resin is similar to that of the core foaming slurry in step S2. The composition of the skin impregnation resin does not contain a foaming agent, and the amounts of functional compounds and fillers can be adjusted within the specified range to optimize the skin performance. Its formulation is: 100 parts of organosilicon prepolymer, 0-5 parts of functional compound (preferably 0.5-3 parts), the amounts of the first curing agent and catalyst are the same as in step two, and 5-30 parts of filler.

[0058] After the skin impregnation resin is prepared, prepreg molding is performed. The fiber reinforcement after the pretreatment in step one is impregnated in the skin impregnation resin, and the resin content is controlled to be 30%-60% (mass ratio). Then, pregelation or pre-curing is performed at 60-100℃ for 5-30 minutes to obtain a semi-cured skin prepreg.

[0059] Step 4: Integrated molding of the sandwich structure: In a preheated mold, the lower layer of prepreg is laid sequentially, followed by the injection of core foaming slurry and then the upper layer of prepreg. After mold closing and pressurization, the temperature is increased in stages, first foaming the core layer and then curing the entire structure, before demolding. The formula for calculating the injection volume X of the core slurry is: X ≈ S * H ​​* D_c * k, where S is the product area, H is the product thickness, D_c is the target density of the core layer, and k is a process coefficient, ranging from 1.1 to 1.5. The foaming stage temperature is 100-140℃, and the curing stage temperature is 140-180℃. The mold closing pressure is 0.5-5 MPa.

[0060] Specifically, the following steps are included: S4.1: Preheat the mold to 80-120℃.

[0061] S4.2: Lay the following materials sequentially in the mold cavity: lower skin layer prepreg, core layer foaming slurry prepared in step S2, and upper skin layer prepreg.

[0062] The injection volume (X, in g) of the core layer slurry is calculated based on the target product thickness (H, in mm), area (S, in cm²), and target core layer density (D_c, in g / cm³), using the following formula: X ≈ S * H ​​* D_c * k, where k is the process coefficient, with a value ranging from 1.1 to 1.5.

[0063] S4.3: Close the mold and apply a molding pressure of 0.5-5 MPa.

[0064] S4.4: Increase the temperature at a rate of 1-5℃ / min to the range above the decomposition temperature of the foaming agent and below the curing temperature (usually 100-140℃) and hold for 5-20 minutes to allow the core layer to fully foam.

[0065] S4.5: Continue heating to the complete curing temperature (usually 140-180℃), and cure at this temperature and under the maintained pressure for 20-60 minutes to allow the skin and core layers to complete the final curing simultaneously and form a strong interface.

[0066] S4.6: Cool to below 60℃ and demold.

[0067] Employing a simultaneous foaming and curing integrated molding technology, the skin and core layers are metallurgically bonded, with no adhesive layer or weak interface layer, avoiding the risk of interlayer delamination associated with traditional adhesive sandwich panels, resulting in excellent product integrity and environmental reliability.

[0068] Step 5: Post-curing: After demolding, the product is placed in an oven and cured at 150-200℃ for 2-10 hours to improve the cross-linking network, thereby obtaining the high-temperature resistant sandwich structure silicone foam material and a final product with stable performance.

[0069] The following are examples of high-temperature resistant sandwich-structured silicone foam materials and their preparation methods: Example 1: 1. Raw materials and formula (unit: parts by mass) Core layer foaming slurry formulation: Vinyl silicone oil (Vi-PDMS, viscosity 5000 mPa·s): 100 parts; 2-(1-Phenylopidin-1-yl)acetic acid (PPAA): 3 parts; Hydrogen-containing silicone oil (crosslinking agent, hydrogen content 0.8%): 8 parts (calculated based on Si-H:Vi ≈ 1.5:1); Azodicarbonamide (AC, foaming agent): 4 parts; Platinum catalyst (Pt content 3000 ppm): 0.05 parts (approximately 50 ppm Pt); Ethynylcyclohexanol (inhibitor): 0.1 parts; Fumed silica (filler, hydrophobic): 5 parts; Skin impregnation resin formulation: Vinyl silicone oil (Vi-PDMS): 100 parts; PPAA: 1.5 servings; Hydrogen-containing silicone oil (crosslinking agent): 5.5 parts (calculated based on Si-H:Vi ≈ 1.1:1); Platinum catalyst: 0.05 parts; Fumed silica: 15 parts; Reinforcing material: Grade E glass fiber woven fabric, surface density 300 g / m², size 200 mm × 200 mm.

[0070] Pretreatment agent: γ-aminopropyltriethoxysilane (KH550) 2% ethanol solution.

[0071] 2. Preparation steps Step 1: Pretreatment of fiberglass cloth Immerse the fiberglass cloth in a sufficient amount of 2% KH550 ethanol solution, ensuring complete saturation, and soak for 15 minutes.

[0072] Remove the fiberglass cloth and hang it at room temperature to drain excess liquid for about 5 minutes.

[0073] The drained fiberglass was placed in a forced-air drying oven and dried at 110°C for 1 hour. After drying, it was placed in a desiccator for later use.

[0074] Step 2: Preparation of core layer foaming slurry In a 500 mL plastic beaker, add 100 parts vinyl silicone oil and 3 parts PPAA.

[0075] Stir for 30 minutes using a high-speed mechanical stirrer (approximately 800 rpm) until the PPAA is evenly dispersed (or partially dissolved) and the system appears slightly milky white.

[0076] Add 5 parts of fumed silica, 0.1 parts of inhibitor and 4 parts of AC foaming agent in sequence. Stir for 5 minutes after each component is added until the mixture is uniform.

[0077] Add 8 parts of hydrogen-containing silicone oil and stir for 10 minutes.

[0078] Finally, add 0.05 parts of platinum catalyst and stir rapidly for 5 minutes to obtain a uniform core foaming slurry. Proceed immediately to the next step or store briefly in a sealed container.

[0079] Step 3: Preparation of skin impregnation resin and prepreg preparation In another beaker, mix the skin-impregnating resin according to the formula: mix 100 parts vinyl silicone oil with 1.5 parts PPAA for 20 minutes.

[0080] Add 15 parts of fumed silica and stir for 10 minutes until no dry powder remains.

[0081] Add 5.5 parts of hydrogen-containing silicone oil and stir for 5 minutes.

[0082] Add 0.05 parts of platinum catalyst and stir for 5 minutes to obtain a uniform skin-impregnated resin.

[0083] Lay a pre-treated fiberglass cloth flat and evenly coat it with a layer of prepared impregnation resin using a scraper or roller, ensuring the resin fully wets the fibers. Weigh the cloth to control the resin coating amount on one side to be approximately 50% of the fiberglass cloth's mass.

[0084] The coated fiberglass cloth was placed in an 80°C oven for pre-curing (gelling) for 10 minutes. After removal, a semi-cured, still tacky, skin prepreg was obtained. Two sheets were prepared in total.

[0085] Step 4: Integrated molding Preheat the flat mold (cavity dimensions 210 mm × 210 mm × 6 mm) to 100°C. Lay the first layer of prepreg (resin side up) inside the cavity. Quickly and evenly pour all the core foaming slurry into the center of the prepreg.

[0086] Immediately cover with the second layer of prepreg (resin side down) to form a prepreg / slurry / prepreg sandwich structure.

[0087] Close the mold quickly and apply a clamping pressure of 1.5 MPa. Increase the mold temperature to 120°C at a rate of 2°C / min and maintain it at 120°C and 1.5 MPa for 15 minutes (during this stage, the foaming agent decomposes, the slurry foams, and initially solidifies). Continue to increase the temperature to 160°C at a rate of 2°C / min and maintain it at 160°C and 1.5 MPa for 40 minutes to complete full curing. Cool the mold with water to below 60°C, release the pressure, and demold to obtain the sandwich structure panel blank.

[0088] Step 5: Post-curing The demolded boards were placed in a forced-air drying oven and cured at 180°C for 4 hours, then cooled to room temperature in the oven. Example 2: 1. Raw materials and formula (unit: parts by mass) Core layer foaming slurry formulation: Hydroxyl-terminated polydimethylsiloxane (OH-PDMS, viscosity 10000 mPa·s): 100 parts; 2-Quinolinecarboxylic acid (functional compound substitute): 2 parts; Methyltrimethoxysilane (crosslinking agent): 5 parts; Dibutyltin dilaurate (catalyst): 0.5 parts; Sodium bicarbonate (foaming agent): 3 parts; Water (as a foaming agent and condensation reactant): 1 part; Light calcium carbonate (filler): 10 parts; Skin impregnation resin formulation: OH-PDMS: 100 copies; 2-Quinoline carboxylic acid: 1 part; Methyltrimethoxysilane: 7 parts; Dibutyltin dilaurate: 0.7 parts; Light calcium carbonate: 25 parts Reinforcing material: chopped strand mat made of glass fiber, with a surface density of 200 g / m² and dimensions of 200 mm × 200 mm.

[0089] Pretreatment agent: None (utilizing the wettability of the condensation system on glass fiber and the direct effect of functional compounds).

[0090] 2. Preparation steps Step 1: Preparation of fiberglass mat Fiberglass chopped strand mat can be directly cut to the required size without chemical pretreatment, but it needs to be dried in an 80°C oven for 2 hours to remove moisture.

[0091] Step 2: Preparation of core layer foaming slurry In a planetary mixer, add 100 parts OH-PDMS and 2 parts 2-quinoline carboxylic acid, and mix at low speed for 20 minutes. Add 10 parts light calcium carbonate and mix at medium speed for 15 minutes until evenly dispersed. Add 5 parts methyltrimethoxysilane and 3 parts sodium bicarbonate, and mix at low speed for 10 minutes. Just before pouring, add 0.5 parts dibutyltin dilaurate and 1 part water, mix at high speed for 1-2 minutes until evenly mixed, and immediately proceed to the next step (this slurry has a short pot life).

[0092] Step 3: Preparation of skin impregnation resin and prepreg preparation In a container, mix 100 parts OH-PDMS and 1 part 2-quinoline carboxylic acid and stir for 15 minutes. Add 25 parts light calcium carbonate and stir until homogeneous. Add 7 parts methyltrimethoxysilane and 0.7 parts dibutyltin dilaurate and stir until homogeneous.

[0093] The fiberglass mat is immersed in the resin, or the resin is applied by scraping to fully impregnate the fiberglass mat, controlling the resin content to be about 60%.

[0094] Allow to stand at room temperature (25°C) for approximately 30 minutes to pre-cure (surface dry) to obtain a prepreg with some strength but still soft. Two sheets were prepared.

[0095] Step 4: Atmospheric pressure thermoforming The first piece of leather prepreg is laid in a flat mold (cavity size 210 mm × 210 mm × 10 mm) coated with a release agent.

[0096] Quickly pour the core foaming slurry onto the prepreg and lightly level it. Cover with the second layer of skin prepreg. Cover the mold with the top cover (without applying significant mechanical pressure, relying solely on its own weight). Place the entire mold in an oven preheated to 80°C for 60 minutes to allow the core foaming slurry to foam and initially cure within the confined space. Increase the oven temperature to 120°C and maintain for 2 hours to achieve full curing. Turn off the oven and allow it to cool naturally to room temperature before demolding.

[0097] Step 5: Post-curing The product was placed in a 100°C oven and cured for 8 hours to remove residual small molecules and improve crosslinking, thus obtaining the high-temperature resistant sandwich structure silicone foam material.

[0098] Comparative example: Preparation of sandwich-structured silicone foam board without functional compounds 1. Raw materials and formula (unit: parts by mass) Core layer foaming slurry formulation: Vinyl silicone oil (Vi-PDMS, viscosity 5000 mPa·s): 100 parts; No functional compounds (such as PPAA) are added; Hydrogen-containing silicone oil (crosslinking agent, hydrogen content 0.8%): 8 parts (Si-H:Vi ≈ 1.5:1); Azodicarbonamide (AC, foaming agent): 4 parts; Platinum catalyst (Pt content 3000 ppm): 0.05 parts; Ethynylcyclohexanol (inhibitor): 0.1 parts; Fumed silica (filler): 5 parts; Skin impregnation resin formulation: Vinyl silicone oil (Vi-PDMS): 100 parts; No functional compounds are added; Hydrogen-containing silicone oil (crosslinking agent): 5.5 parts (Si-H:Vi ≈ 1.1:1); Platinum catalyst: 0.05 parts; Fumed silica: 15 parts; Reinforcing materials and pretreatment: exactly the same as in Example 1, using Grade E glass fiber woven fabric (300 g / m²) pretreated with 2% KH550 solution.

[0099] 2. Preparation steps The preparation steps (pretreatment, ingredient mixing, prepreg preparation, molding parameters, post-curing conditions) were strictly kept exactly the same as in Example 1. The only variable was that 2-(1-phenylpiperidin-1-yl)acetic acid (PPAA) was not added to any of the resin formulations.

[0100] This comparative example aims to clearly demonstrate, through direct comparison with the examples, the key role of the functional compound (2-(1-phenylpiperidin-1-yl)acetic acid or its analogues) in achieving excellent interfacial bonding and high-temperature resistance in this invention.

[0101] according to Figure 2-7 As shown, the high-temperature resistant sandwich-structured silicone foam materials prepared in Examples 1 and 2 have lower porosity and smaller pore size compared to the high-temperature resistant sandwich-structured silicone foam material prepared in the comparative example. The addition of functional compounds, whose polar groups such as carboxyl groups in their molecules can act as physical crosslinking points or interact with the components of the foaming system, effectively increases the viscosity of the resin slurry before foaming. During the foaming process, the higher melt strength better encapsulates the foaming gas, inhibiting excessive merging and coarsening of bubbles, thus forming a finer and more uniform cell structure. This fine cell structure means thinner and more complete cell walls, with a larger stress-bearing skeleton per unit volume, thereby providing higher compressive and resilience strength at the same density.

[0102] according to Figure 8-10 As shown, the high-temperature resistant sandwich-structured silicone foam material prepared in the comparative example showed damage after combustion compared to the high-temperature resistant sandwich-structured silicone foam materials prepared in Examples 1 and 2. Samples of 50 mm x 10 mm x 5 mm were taken from Examples 1, 2, and the comparative example, and flame retardancy tests were conducted. The samples were placed in the outer flame of an alcohol lamp and burned for 60 seconds, and the combustion status was observed. For the samples of Examples 1 and 2 of this invention, the flame gradually self-extinguished after about 30 seconds of ignition, and completely self-extinguished within 60 seconds, with no molten dripping produced during the entire combustion process. The silicone foam materials of Examples 1 and 2 of this invention both exhibit good flame retardancy, as shown in Table 1, with a vertical burning rating of V-0. In contrast, the comparative example sample burned rapidly after about 5 seconds of ignition, and completely burned to ash within 30 seconds, lacking high-temperature flame retardant properties.

[0103] Table 1 Vertical Combustion Rating Comparison Table

[0104] Table 2850℃ Open Flame: Comparison of Temperature Changes on Back Side of Foamed Material Samples Under Combustion Over Time (Measured by Measured Temperature over Time)

[0105] according to Figure 11-13 As shown in Table 2, regarding the temperature change of the back side of the foamed material sample under an open flame at 850℃, it can be seen from Experimental Examples 1 and 2 that under an open flame at 850℃, the temperature of the back side of the foamed material sample rises slowly. After 30 minutes of open flame, the temperature on the side away from the open flame does not exceed 150℃, meeting the flame retardant Class A standard. In contrast, the unmodified control sample shows a faster temperature rise on the back side under an open flame at 850℃. After 30 minutes of open flame, the temperature on the side away from the open flame reaches a maximum of 550℃, indicating no flame retardant properties. The experiments demonstrate that the embodiments of the present invention possess high-temperature flame retardant properties.

[0106] This invention achieves a synergistic improvement in lightweight, high strength, flame retardancy, and exceptional high-temperature resistance through an innovative sandwich structure design and the introduction of key interface modifiers. It combines ultra-lightweight, high-strength, flame-retardant, and high-temperature resistant properties. This significantly enhances the mechanical strength and high-temperature durability of silicone foam while maintaining its inherent advantages of being lightweight and flame-retardant.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A high temperature resistant sandwich structured silicone foam material, characterized in that The material is in an integrated sandwich structure, including a core layer and skin layers respectively arranged on both sides of the core layer, and specifically comprising the following components: Silicone resin matrix: the silicone resin matrix is a vinyl silicone resin with a vinyl content of 0.5-1.2 wt% and a viscosity of 5000-20000 cP @25℃; Key functional compound: the key functional compound is 2-(1-phenylpiperidin-1-yl)acetic acid or its functionally equivalent compound; Fiber reinforcement: the fiber reinforcement is a glass fiber fabric, including at least one of chopped mat, plain cloth or unidirectional cloth; Foaming and curing system: the foaming and curing system includes crosslinking agent, catalyst, foaming agent and optional additives; The skin layer is a continuous dense reinforced layer composed of the glass fiber fabric and the silicone resin matrix; the core layer is a porous foam layer formed by foaming the silicone resin matrix, and the key functional compound is uniformly dispersed in the porous foam layer.

2. The high temperature resistant sandwich structure silicone foam material according to claim 1, characterized in that When it is an addition curing system, the crosslinking agent in the core layer is hydrogen-containing silicone oil, and the catalyst is platinum gold catalyst, and the core layer includes the following components by mass fraction: Silicone resin matrix 100 parts Key functional compound 0.5-10 parts Hydrogen-containing silicone oil 5-100 parts Foaming agent 1-10 parts Platinum gold catalyst 0.001-0.05 parts.

3. The high temperature resistant sandwich structure silicone foam material according to claim 1, characterized in that When it is a condensation curing system, the crosslinking agent in the core layer is alkoxy silane, and the catalyst is organotin catalyst, and the core layer includes the following components by mass fraction: Silicone resin matrix 100 parts Key functional compound 0.5-10 parts Alkoxy silane 1-10 parts Foaming agent 1-10 parts Organotin catalyst 0.1-2 parts.

4. The high temperature resistant sandwich structure silicone foam material according to claim 2 or 3, characterized in that The components in the core layer also include optional additives, and the optional additives include at least one of inhibitor 0.01-0.5 parts, filler 1-20 parts, flame retardant 1-20 parts or colorant 0.1-5 parts.

5. The high temperature resistant sandwich structure silicone foam material according to claim 1, characterized in that The areal density of the glass fiber fabric is 100-500 g / m².

6. The high temperature resistant sandwich structure silicone foam material according to claim 5, characterized in that The specific compounding manner of the glass fiber fabric and the silicone resin matrix in the skin layer is that the glass fiber fabric is impregnated in the skin layer impregnation resin, and the mass ratio of resin to the skin layer is 0.3:1-0.6:

1.

7. The high temperature resistant sandwich structure silicone foam material according to claim 6, characterized in that When it is an addition curing system, the crosslinking agent in the skin layer impregnation resin is hydrogen-containing silicone oil, and the catalyst is platinum gold catalyst, and the skin layer impregnation resin includes the following components by mass fraction: Silicone resin matrix 100 parts Key functional compound 0-5 parts Hydrogen-containing silicone oil 5-100 parts Platinum gold catalyst 0.001-0.05 parts.

8. The high temperature resistant sandwich structure silicone foam material according to claim 6, characterized in that When it is a condensation curing system, the crosslinking agent in the skin layer impregnation resin is alkoxy silane, and the catalyst is organotin catalyst, and the skin layer includes the following components by mass fraction: Silicone resin matrix 100 parts Key functional compound 0-5 parts Alkoxy silane 1-10 parts Organotin catalyst 0.1-2 parts.

9. The high temperature resistant sandwich structure silicone foam material according to claim 7 or 8, characterized in that The components in the skin layer also include optional additives, and the optional additives include at least one of inhibitor 0.01-0.5 parts, filler 5-30 parts, flame retardant 1-20 parts or colorant 0.1-5 parts.

10. Process for the production of the high temperature resistant sandwich structure silicone foam material according to any one of claims 1 to 9, characterized in that The method includes the following steps: Step one: Pretreatment of fiber reinforcement; Glass fiber fabric was immersed in silane coupling agent ethanol solution, dried and stored for later use; Step two: Preparation of core layer foaming slurry; key functional compounds were premixed with part of silicone resin matrix, and the remaining silicone resin matrix, crosslinking agent, foaming agent, catalyst and optional additives were sequentially added and mixed uniformly; Step three: Preparation of skin layer impregnated resin and prepreg molding; key functional compounds were premixed with part of silicone resin matrix, and the remaining silicone resin matrix, crosslinking agent, catalyst and optional additives were sequentially added and mixed uniformly; the pretreated glass fiber reinforcement in step one was immersed in the skin layer impregnated resin, and a semi-cured skin layer prepreg was obtained after pre-gelation or pre-curing; Step four: Integrated molding of sandwich structure; the lower skin layer prepreg was laid in the preheated mold, the core layer foaming slurry was injected, and the upper skin layer prepreg was laid, the mold was closed and pressurized, and the temperature was raised in stages, first making the core layer foam and then making the whole solidify, and then demolding; Step five: Post-curing; the demolded product was post-cured at 150-200℃ for 2-10 hours to obtain the high-temperature-resistant sandwich structure silicone foaming material.

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