Flame-retardant heat-insulating acrylic plate and preparation method thereof

Abstract

The invention relates to the technical field of acrylic plates, and discloses a flame-retardant heat-insulating acrylic plate and a preparation method thereof.The flame-retardant heat-insulating acrylic plate comprises methyl methacrylate, an initiator and a specific composite additive system, and the composite additive system comprises four key functional components, the preparation method comprises the following steps of: taking tri (2-hydroxyethyl) boric acid ester as a precursor of a glass phase network, octa (aminophenyl) polyhedral oligomeric silsesquioxane as a network framework, diethyl diethanol amino methyl phosphonate as a precursor of a catalyst and a foaming agent, and pentaerythritol tetra [beta-(3, 3, 4-trimethyl-1, 3, 5-trimethyl-1, 3, 5-trimethyl-1, 3, 5-trimethyl-1, 3, 5-trimethyl-1, 3, 5-trimethyl-1, 3, 5-trimethyl-1, 3, 5 The invention relates to 2, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid] ester. Through the synergistic effect of the components, a compact ceramic foam thermal insulation layer can be generated in situ during combustion, the unification of excellent flame-retardant thermal insulation property and inherent high optical and mechanical properties of the material is realized, and the problem that comprehensive properties are difficult to consider in a traditional modification technology is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acrylic sheet, in particular to a flame-retardant and heat-insulating acrylic sheet and a preparation method thereof. BACKGROUND

[0002] Polymethyl methacrylate (PMMA), commonly known as acrylic, has a wide range of applications in many fields due to its excellent optical transparency, excellent weather resistance and good processing performance. However, as an organic polymer material, PMMA has inherent flammability defects. When it encounters fire, it will quickly melt and burn, producing molten droplets, not only accelerating the spread of the flame, but also greatly limiting its application in buildings, transportation and other places with high requirements for fire safety.

[0003] To improve the flame retardant performance of PMMA, the existing mainstream technology usually adds various flame retardants to the matrix. However, this method generally faces a core contradiction: the addition of flame retardants often comes at the expense of key material properties. For example, common inorganic filler flame retardants have poor compatibility with the PMMA matrix, and their micron-level distribution can severely scatter light, causing the acrylic material to lose its most valuable high transparency and low haze characteristics. At the same time, the introduction of these fillers often destroys the continuity of the polymer matrix, resulting in a decrease in the mechanical properties of the material such as impact strength, making it difficult to balance flame retardancy and inherent physical properties of the material.

[0004] In some intumescent flame retardant technologies aimed at forming a char layer on the surface for heat insulation, there are also insurmountable technical problems. On the one hand, in thermoplastic resins such as PMMA, the carbon layer formed during combustion is often loosely structured and low in strength, making it difficult to adhere firmly to the surface of the molten matrix and easily falling off and breaking under the scouring of the flame or the flow of the matrix, resulting in the premature failure of the heat insulation barrier. On the other hand, the formation of this protective layer is highly dependent on the complex timing matching between matrix decomposition and flame retardant activation, and the premature melting and degradation of the matrix often leads to a mismatch in the reaction process, making it impossible for functional components to form a stable and continuous protective layer in place, ultimately leading to the failure of the flame retardant design. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a flame-retardant and heat-insulating acrylic sheet and a preparation method thereof, which solves the problem that traditional flame-retardant modification techniques inevitably cause serious degradation of inherent advantages such as high light transmittance, low haze and excellent mechanical properties of the acrylic sheet while imparting flame-retardant and heat-insulating properties to the acrylic sheet.

[0006] To solve the above problems, the present application provides a flame-retardant and heat-insulating acrylic sheet, which adopts the following technical solution: A flame-retardant and heat-insulating acrylic sheet is prepared by polymerization of raw materials comprising the following weight parts: Methyl methacrylate: 100 parts; Azobisisobutyronitrile: 0.1-0.5 parts; Component A: 1.0-5.0 parts; Component B: 1.0-5.0 parts; Component C: 3.0-8.0 parts; Component D: 0.1-1.0 parts; Wherein, Component A is tris(2-hydroxyethyl) borate, Component B is octakis(aminophenyl) cage silsesquioxane, Component C is diethyldiethanolaminomethyl phosphonate, and Component D is pentaerythritol tetrakis[beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate].

[0007] By adopting the technical scheme, the application establishes a composite additive system composed of four functional components, which has the functions of synergistic effect and reaction process self-regulation. The composite additive system can be uniformly dispersed at the molecular level or nanometer level in the acrylic matrix, ensuring the inherent high transparency and mechanical properties of the plate. When encountering fire, the composite additive system forms a stable protective layer with both flame-retardant and heat-insulating functions on the surface of the material through a precise, multi-step in-situ reaction process, and the action mechanism is as follows: When the material is heated, the component C with low thermal stability is first decomposed. The decomposition products release non-combustible gas, which plays a role of diluting oxygen concentration and acting as a foaming agent, and generate acidic substances with strong dehydration catalysis.

[0008] Under the catalysis of the above acidic substances, the acrylic matrix and other organic components begin to dehydrate and carbonize, forming a preliminary carbon layer.

[0009] As the temperature further rises, the component A reacts with the component B as a rigid nanoskeleton to form a boron-silicon crosslinked network in-situ. The boron-silicon crosslinked network combines with the carbon layer generated in the early stage to form a ceramic skeleton with structural strength and high temperature stability.

[0010] In this process, the core innovation of the application lies in the role of component D. As a heat-sensitive free radical inhibitor, component D decomposes within a specific temperature range, precisely controls the decomposition rate of the matrix by inhibiting the chain degradation reaction of the acrylic matrix. This control ensures that the matrix has sufficient gas to expand when the skeleton has sufficient strength, and ultimately forms a structurally complete, dense and continuous porous ceramic foam heat insulation layer. The heat insulation layer can effectively block heat transfer, isolate oxygen and inhibit the escape of combustible volatile substances.

[0011] This solution fundamentally solves the problem of deteriorated optical and mechanical properties caused by large amounts of filler and poor compatibility in traditional filler technology. At the same time, by introducing a self-regulating mechanism for the reaction process, it ensures the effective formation of the protective layer and achieves excellent comprehensive performance.

[0012] Preferably, the raw materials are in the following weight proportions: 100 parts methyl methacrylate, 0.3 parts azobisisobutyronitrile, 3.0 parts component A, 3.0 parts component B, 5.5 parts component C, and 0.5 parts component D.

[0013] By adopting the above technical solution, the proportions of each component are optimally balanced, resulting in the best performance of the obtained board in terms of flame retardancy, heat insulation, optical and mechanical properties.

[0014] Preferably, component A is prepared by reacting boric acid and triethanolamine under reflux in the presence of a dehydrating agent, followed by vacuum distillation. Component C is prepared by reacting diethyl phosphite, diethanolamine, and an aqueous formaldehyde solution in a solvent, followed by vacuum distillation to remove the solvent.

[0015] By adopting the above technical solution, it can be ensured that components A and C, as key precursors, have high purity and stable chemical structures, thus guaranteeing the consistency and reliability of the final material properties.

[0016] Preferably, during the reaction process for preparing component C, the internal temperature of the reaction system is maintained within the range of 15°C to 30°C.

[0017] By adopting the above technical solution, the synthesis reaction rate of component C can be effectively controlled, the occurrence of side reactions can be suppressed, and the yield and purity of the product can be improved.

[0018] This invention provides a method for preparing flame-retardant and heat-insulating acrylic sheets, using the following technical solution: A method for preparing a flame-retardant and heat-insulating acrylic sheet as described in any of the preceding claims includes the following steps: S1. Add azobisisobutyronitrile initiator to methyl methacrylate monomer and stir continuously to form a solution; S2. Under stirring, add component A, component C and component D to the solution in step S1 in sequence, dissolve them evenly to form a premixed solution; S3. Add component B to the premixed solution and perform ultrasonic dispersion treatment to obtain a uniform slurry; S4. Perform vacuum degassing treatment on the slurry; S5. Pour the degassed slurry into the mold and perform programmed temperature rise curing; S6. Cool and demold the cured product to obtain the flame-retardant and heat-insulating acrylic sheet.

[0019] By employing the above technical solution, this preparation method ensures that each functional additive achieves uniform molecular or nanoscale dispersion within the methyl methacrylate monomer through a specific feeding sequence and dispersion technique. First, soluble components A, C, and D are dissolved to form a homogeneous solution. Then, nanoscale component B is dispersed in this solution via ultrasonic treatment, preventing the aggregation of component B. This highly uniform dispersion is a prerequisite for preparing high-transparency, low-haze boards and ensuring efficient synergistic reactions of all components during combustion. Furthermore, the programmed temperature curing process effectively controls the polymerization reaction, reduces internal stress, and guarantees the mechanical properties and optical uniformity of the board.

[0020] Preferably, the continuous stirring in step S1 is carried out at room temperature until the azobisisobutyronitrile initiator is completely dissolved. By adopting the above technical solution, the complete dissolution of the initiator can be ensured while avoiding premature decomposition of the initiator due to excessively high temperature, thereby ensuring the controllability of the polymerization reaction.

[0021] Preferably, the vacuum degassing treatment in step S4 is carried out at room temperature and a vacuum level below 1 kPa. By adopting the above technical solution, air bubbles introduced during the mixing process of the slurry can be efficiently removed, while avoiding monomer volatilization loss due to high temperature or high vacuum, ensuring that the final board is dense and defect-free.

[0022] Preferably, the programmed temperature curing in step S5 includes a first curing stage performed in a temperature range of 45°C to 65°C, and a second curing stage performed in a temperature range of 65°C to 110°C.

[0023] By adopting the above technical solution, the first lower temperature curing stage is conducive to the stable initiation and gelation of the polymerization reaction, and reduces the concentrated release of polymerization heat; the second higher temperature curing stage ensures complete conversion of monomers, making the cross-linking and curing of the board more complete, thereby obtaining the best mechanical strength and thermal stability.

[0024] Preferably, in the programmed temperature rise curing process, the process of rising from one isothermal stage to the next isothermal stage is carried out in a linear temperature rise manner.

[0025] By adopting the above technical solution, linear heating ensures that the slurry inside the mold is heated evenly, avoiding internal stress caused by excessive local temperature difference, which is conducive to improving the flatness and optical quality of the final product.

[0026] This invention provides a flame-retardant and heat-insulating acrylic sheet and its preparation method. It has the following beneficial effects: 1. This invention solves the problem of balancing flame retardancy and material physical properties in traditional technologies by compounding components A, B, C, and D. Because each component has high compatibility with the acrylic matrix, it imparts excellent flame retardant and heat insulation properties to the board while avoiding damage to optical and mechanical properties, resulting in a final product that maintains high light transmittance, low haze, and good impact strength.

[0027] 2. This invention induces an in-situ reaction between components A, B, and C under combustion conditions, generating a structurally stable ceramicized porous foam layer on the material surface. This layer acts as a physical barrier, effectively blocking heat transfer and inhibiting the escape of combustibles, thereby improving the flame retardancy rating of the board to UL-94V-0 and endowing it with excellent dynamic thermal insulation performance.

[0028] 3. By introducing component D, this invention effectively inhibits premature decomposition of the matrix in the early stages of material heating. This creates the necessary reaction time window for components A, B, and C to form a stable ceramicized foam layer, ensuring the effective formation of the protective layer and solving the technical problem of decreased flame-retardant and heat-insulating performance when this component is absent. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0031] Preparation Examples 1-4: Preparation Example 1: This preparation example discloses a method (standard conditions) for preparing tris(2-hydroxyethyl)boronic acid ester, including the following steps: In a 500 mL three-necked flask equipped with a mechanical stirrer, thermometer, and water separator, 0.20 mol of boric acid, 0.46 mol of triethanolamine, and 100 mL of toluene were added sequentially as a dehydrating agent.

[0032] Turn on the stirrer and heat the mixture to 135°C, allowing the system to undergo a reflux reaction at a gentle boil. The water generated during the reaction azeotropically distills off with toluene, condenses, and separates into layers in a water separator, with the lower layer of water continuously removed.

[0033] Maintain this reflux state until no obvious water stratification occurs in the distributor, which takes about 4 hours.

[0034] Stop heating and cool the reaction solution to room temperature (25°C).

[0035] The cooled reaction mixture was transferred to a rotary evaporator and subjected to vacuum distillation at a vacuum of 0.095 MPa and a water bath temperature of 120 °C to completely remove the solvent toluene and a small amount of unreacted raw materials.

[0036] The final product was 105.5g of a colorless, transparent, viscous liquid, which was tris(2-hydroxyethyl)boronic acid ester.

[0037] Preparation Example 2: This preparation example discloses a method for preparing tris(2-hydroxyethyl)boronic acid esters (with different reactant ratios), including the following steps: The same equipment as in Preparation Example 1 was used. 0.20 mol of boric acid, 0.54 mol of triethanolamine, and 120 mL of toluene were added sequentially to a three-necked flask. In this formulation, the molar ratio of triethanolamine to boric acid was increased.

[0038] Turn on the stirrer, heat to 140°C and maintain reflux. Continuously remove the water produced in the reaction.

[0039] Continue heating until no water stratification occurs in the water distributor (approximately 3.5 hours), then stop heating and allow it to cool to room temperature.

[0040] The solvent and unreacted substances were removed using the same vacuum distillation conditions as in Preparation Example 1.

[0041] The final product was 106.1g of a pale yellow, transparent, viscous liquid, which was tris(2-hydroxyethyl)boronic acid ester.

[0042] Preparation Example 3: This preparation example discloses a method (standard conditions) for preparing diethyldiethanolaminomethylphosphonate, including the following steps: In a 1000 mL three-necked flask equipped with a mechanical stirrer, a constant pressure dropping funnel, and a thermometer, 0.40 mol of diethyl phosphite, 0.40 mol of diethanolamine, and 250 mL of anhydrous ethanol were added as solvents.

[0043] Place the three-necked flask in an ice-water bath, turn on the stirrer, and wait for the internal temperature of the system to drop below 5°C.

[0044] Using a constant-pressure dropping funnel, slowly add 32.43 g of a 37% formaldehyde aqueous solution. Strictly control the dropping rate to ensure the internal temperature of the reaction system is maintained between 15°C and 20°C. The dropping process takes approximately 1.5 hours.

[0045] After the addition was complete, the ice-water bath was removed, and the reaction system was stirred and reacted for another 10 hours at room temperature (25°C).

[0046] After the reaction was completed, the reaction solution was transferred to a rotary evaporator, where the solvents ethanol and water were removed by vacuum evaporation at a water bath temperature of 55°C.

[0047] The final product yielded 98.8g of a pale yellow oily liquid, which was diethyldiethanolaminomethylphosphonate. Preparation Example 4: This preparation example discloses a method for preparing diethyldiethanolaminomethylphosphonate (at different reaction temperatures), including the following steps: The same equipment and raw material amounts were used as in Preparation Example 3.

[0048] After mixing diethyl phosphite, diethanolamine, and anhydrous ethanol, the mixture was cooled in a water bath at room temperature (25°C) instead of using an ice-water bath.

[0049] A 37% formaldehyde aqueous solution was slowly added dropwise using a constant pressure dropping funnel. By adjusting the dropping rate and using a water bath for cooling, the internal temperature of the reaction system was controlled between 25°C and 30°C.

[0050] After the addition was complete, the reaction was continued to be stirred for 8 hours at room temperature (approximately 25°C).

[0051] The same post-treatment method as in Preparation Example 3 was used to remove the solvent and water by rotary evaporation.

[0052] The final product was 97.5g of a pale yellow oily liquid, which was diethyldiethanolaminomethylphosphonate.

[0053] Examples 1-5: Example

[0054] This embodiment provides a method for preparing flame-retardant and heat-insulating acrylic sheets, wherein the component ratios are based on a standard ratio, and includes the following steps: S1. In a 500mL beaker, add 100g of purified methyl methacrylate (MMA) monomer and 0.3g of azobisisobutyronitrile (AIBN) initiator. Stir at 400rpm for 15min at room temperature (25℃) using a magnetic stirrer until the AIBN is completely dissolved.

[0055] S2. While stirring continuously, add 3.0g of tris(2-hydroxyethyl)boronic acid ester (component A) prepared in Preparation Example 1, 5.5g of diethyldiethanolaminomethylphosphonic acid ester (component C) prepared in Preparation Example 3, and 0.5g of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ester (component D) to the solution in the previous step, and continue stirring for 45 minutes to ensure that all components are dissolved evenly.

[0056] S3. Add 3.0 g of octa(aminophenyl) cage-like silsesquioxane (OAPS-POSS, component B) to the mixed solution from the previous step. Place the beaker in an ultrasonic cleaner and perform ultrasonic dispersion treatment at 400W power and 30kHz frequency for 15 min to obtain a clear, transparent, uniformly dispersed nanoscale slurry.

[0057] S4. Transfer the slurry to a vacuum drying oven and degas for 25 minutes at room temperature and a vacuum level below 1 kPa.

[0058] S5. Pour the degassed slurry into a glass mold (3mm) preheated to 45℃. Place the mold horizontally in a programmable temperature-controlled oven and cure it according to the following procedure: Keep at 45℃ for 20 hours; The temperature was linearly increased to 65°C within 1 hour and held at this temperature for 3 hours. The temperature was linearly increased to 110°C within 1 hour and held at this temperature for 2 hours.

[0059] S6. After the program ends, turn off the heating and allow the mold to cool naturally to room temperature in the oven. Demold to obtain the hot acrylic sheet. Example

[0060] This embodiment provides a method for preparing flame-retardant and heat-insulating acrylic sheets, which has a high total amount of core functional additives, and includes the following steps: S1. Weigh 100g of MMA monomer and 0.5g of AIBN, and mix and dissolve them according to step 1 of Example 1.

[0061] S2. While stirring continuously, add 5.0g of the product from Preparation Example 1 (component A), 5.5g of the product from Preparation Example 3 (component C), and 0.5g of component D in sequence. Continue stirring for 45 minutes.

[0062] S3. Add 5.0g of OAPS-POSS (component B) and disperse it under the same ultrasonic conditions as in Example 1.

[0063] S4. The subsequent vacuum degassing, pouring, programmed temperature curing and demolding steps are exactly the same as in Example 1, to obtain the thermoacrylic sheet. Example

[0064] This embodiment provides a method for preparing flame-retardant and heat-insulating acrylic sheets, which has a low total amount of core functional additives, and includes the following steps: S1. Weigh 100g of MMA monomer and 0.1g of AIBN, and mix and dissolve them according to step 1 of Example 1.

[0065] S2. While stirring continuously, add 1.0g of the product from Preparation Example 1 (component A), 3.0g of the product from Preparation Example 3 (component C), and 0.1g of component D in sequence. Continue stirring for 45 minutes.

[0066] S3. Add 1.0 g of OAPS-POSS (component B) and disperse it under the same ultrasonic conditions as in Example 1.

[0067] S4. The subsequent vacuum degassing, pouring, programmed temperature curing and demolding steps are exactly the same as in Example 1, to obtain the thermoacrylic sheet. Example

[0068] This embodiment provides a method for preparing flame-retardant and heat-insulating acrylic sheets, which changes the internal ratio between core functional additives and includes the following steps: S1. Weigh 100g of MMA monomer and 0.3g of AIBN, and mix and dissolve them according to step 1 of Example 1.

[0069] S2. While stirring continuously, add 3.0g of the product from Preparation Example 2 (component A), 8.0g of the product from Preparation Example 4 (component C), and 0.5g of component D in sequence. Continue stirring for 45 minutes.

[0070] S3. Add 3.0g of OAPS-POSS (component B) and disperse it under the same ultrasonic conditions as in Example 1.

[0071] S4. The subsequent vacuum degassing, pouring, programmed temperature curing and demolding steps are exactly the same as in Example 1, to obtain the thermoacrylic sheet. Example

[0072] This embodiment provides a method for preparing flame-retardant and heat-insulating acrylic sheets, which adjusts the amount of component D (thermally sensitive free radical inhibitor), and includes the following steps: S1. Weigh 100g of MMA monomer and 0.3g of AIBN, and mix and dissolve them according to step 1 of Example 1.

[0073] S2. While stirring continuously, add 3.0g of the product of Preparation Example 1 (component A), 5.5g of the product of Preparation Example 3 (component C), and 1.0g of component D in sequence.

[0074] S3. Add 3.0g of OAPS-POSS (component B) and disperse it under the same ultrasonic conditions as in Example 1.

[0075] S4. The subsequent vacuum degassing, pouring, programmed temperature curing and demolding steps are exactly the same as in Example 1, to obtain the thermoacrylic sheet.

[0076] Comparative Examples 1-5: Comparative Example 1: The difference between this comparative example and Example 1 is that the material prepared in this example is pure PMMA sheet, and components A, B, C, and D are not added to the formulation. The remaining preparation steps are exactly the same as in Example 1.

[0077] Comparative Example 2: Compared to Example 1, the difference lies in that this comparative example employs conventional inorganic filler flame retardant technology. Components A, B, C, and D are not added to the formulation; instead, 40g of aluminum hydroxide (ATH) is added to 100g of MMA monomer as a flame retardant. To ensure uniform dispersion of the ATH powder, an additional step of processing with a high-speed shear emulsifier (8000rpm) for 30min is added after the ultrasonic treatment step. All other preparation steps are the same as in Example 1.

[0078] Comparative Example 3: The difference between this comparative example and Example 1 is that this comparative example uses conventional organic intumescent flame retardant technology. Components A, B, C, and D are not added to the formulation; instead, 15g of melamine polyphosphate (MPP) is added to 100g of MMA monomer as an intumescent flame retardant. The remaining preparation steps are the same as in Example 1.

[0079] Comparative Example 4: Compared with Example 1, the difference is that the formulation of this comparative example lacks the key component D (thermosensitive free radical inhibitor). Specifically, 3.0g of component A, 3.0g of component B, and 5.5g of component C were added to 100g of MMA monomer, but component D was not added. All other preparation steps are exactly the same as in Example 1.

[0080] Comparative Example 5: The difference compared to Example 1 is that the formulation of this comparative example lacks components A and B, which form the ceramic network. Specifically, 5.5g of component C and 0.5g of component D were added to 100g of MMA monomer, but components A and B were not added. All other preparation steps are exactly the same as in Example 1.

[0081] Test Example 1-2: Test Example 1: This test case aims to verify that the acrylic sheet prepared according to Examples 1 to 5 of the present invention can effectively function under heated combustion conditions, forming a protective layer with flame-retardant and heat-insulating functions.

[0082] Experimental steps: The plates obtained in Examples 1 to 5 were cut into square samples of 100mm × 100mm × 3mm. Before testing, all samples were conditioned for at least 48 hours in an environment of 23±2℃ and 50±5% relative humidity.

[0083] The sample was placed horizontally on the sample holder, and the external thermal radiation flux was set to 50 kW / m². 2 The volatile gases escaping from the sample surface are ignited using an electric spark igniter.

[0084] Key data throughout the combustion process are continuously recorded and collected, including ignition time, heat release rate and its peak value, total heat release, and smoke generation rate.

[0085] Macroscopic observation of the morphology of post-combustion residues: After the cone calorimeter test is completed, the sample and residue are allowed to cool completely before being removed from the sample holder. Under natural light conditions, the macroscopic morphological characteristics of the residue are observed and recorded visually, including: the integrity of the residue, whether a continuous coating layer has formed, the surface morphology, and the structural strength is assessed by gently touching it with tweezers.

[0086] Experimental data: Table 1 below summarizes the data obtained from the cone calorimeter tests of the samples from Examples 1 to 5, as well as the morphology of the residues after combustion.

[0087] Table 1. Cone calorimeter test data and residue morphology of the sample from the examples Test sample Ignition time / s Peak heat release rate (kW / m²) Total heat release (MJ / m²) Peak smoke production rate (m² / s) Macroscopic morphology of the residue after combustion Example 1 78 215.4 43.7 0.048 Continuous, intact black porous foam layer, structurally strong Example 2 92 188.1 39.2 0.041 Extremely dense and continuous black porous foam layer, high structural strength Example 3 61 289.7 56.4 0.065 Substantially continuous black foam layer, partially broken, relatively strong structure Example 4 85 204.6 41.8 0.044 Continuous and uniform black porous foam layer, structurally strong Example 5 103 221.3 45.1 0.052 Continuous, intact black porous foam layer, structurally strong in conclusion: The test data in Table 1 show that the acrylic sheets prepared in Examples 1 to 5 of the present invention all exhibit effective combustion suppression performance.

[0088] The ignition time of all the sample examples was prolonged, proving that an effective thermal barrier was formed on the material surface in the early stage of heating, which delayed the substrate from reaching the ignition point.

[0089] The peak heat release rate and total heat release of the samples in all embodiments were at a low level. This is attributed to the formation of a physically stable ceramicized foam layer on the material surface through a series of in-situ reactions during combustion, resulting in the composite additive system. Macroscopic observation of the post-combustion residue confirmed this finding: all embodiments formed a continuous and robust porous layer. This porous layer, acting as an efficient physical barrier, hindered further heat transfer from the external environment to the internal matrix and suppressed the escape of combustible volatiles generated from the thermal decomposition of the matrix into the gas phase for combustion, thus effectively interrupting the continuation of combustion.

[0090] The above results confirm that the technical solution proposed in this invention, which generates a self-regulating ceramicized foam insulation layer in situ during combustion using a composite additive system, is feasible and effective.

[0091] Test Example 2: This test case aims to systematically evaluate and compare the comprehensive performance of the technical solution of the present invention relative to blank samples, prior art, and samples lacking key technical features by conducting a series of performance tests on the plates prepared in Examples 1 to 5 and Comparative Examples 1 to 5.

[0092] Transmittance and haze tests: Test equipment: WGT-S type transmittance / haze meter.

[0093] Test Procedure: Cut the prepared boards into 50mm×50mm samples. After wiping the sample surface with a lint-free cloth, place them in the integrating sphere test port of the testing instrument and measure their total transmittance and haze value respectively. Each sample is measured 3 times, and the average value is taken.

[0094] Impact strength test: Testing equipment: XJJ-5 type cantilever beam / simply supported beam combined impact testing machine.

[0095] Test Procedure: The prepared plates for each example were processed into standard unnotched specimens measuring 80mm × 10mm × 3mm. Impact tests were conducted on the specimens using a 2J pendulum at 23±2℃, and the impact strength was recorded. Five specimens were tested in each group, and the average value was taken.

[0096] Limiting Oxygen Index (LOI) Test: Testing equipment: JF-3 limiting oxygen index tester.

[0097] Test procedure: The prepared plates for each example were processed into 100mm×6.5mm×3mm samples. The samples were vertically clamped in the combustion chamber, the flow rate of the nitrogen-oxygen mixture was adjusted, and the samples were ignited using the top ignition method. The lowest oxygen concentration that could sustain continuous combustion of the samples for 3 minutes or achieve a combustion length of 50mm was recorded.

[0098] Vertical burning test: Test Procedure: The prepared boards were processed into 125mm × 13mm × 3mm strips. The strips were suspended vertically, and the lower end was ignited with a standard flame for 10 seconds. The flame was then removed, and the first afterflame time (t1) was recorded. If the flame extinguished, it was immediately relit for 10 seconds, and the flame was removed. The second afterflame time (t2) and glow time (t3) were recorded. Simultaneously, it was observed whether any burning droplets ignited the absorbent cotton below. The flame retardancy rating was assessed according to the standard.

[0099] Dynamic thermal insulation performance test: Test equipment: Self-built test platform, including adjustable power Bunsen lamps, sample holders, K-type thermocouples and multi-channel data loggers.

[0100] Test Procedure: Cut the prepared plates into 100mm × 100mm × 3mm samples and fix them vertically. Place the test tip of the K-type thermocouple firmly against the center of the unexposed side of the sample. Adjust the Bunsen burner so that the tip of its flame (outer flame) continuously and stably burns the central area of ​​the sample's front side. Start timing from the moment the flame contacts the sample, and continuously record the temperature change of the unexposed side over time using a data logger. The total test duration is 180 seconds.

[0101] Experimental data: Table 2 below summarizes the overall performance test data of all examples and comparative samples.

[0102] Table 2. Overall performance test data of the examples and comparative examples Sample Light transmittance / % Haze / % Impact strength / (kJ / m²) LOI / % UL-94 rating Backfire surface temperature at 180 s / ℃ Example 1 91.5 1.3 14.8 31.5 V-0 185 Example 2 90.3 1.8 13.9 34.0 V-0 162 Example 3 91.8 1.1 15.1 28.5 V-1 224 Example 4 91.1 1.5 14.3 32.5 V-0 179 Example 5 91.3 1.4 14.6 31.0 V-0 193 Comparative Example 1 92.4 0.8 15.5 17.5 NR (melt dripping) >600 (burning through at 110 s) Comparative Example 2 53.2 85.4 8.1 35.5 V-0 341 Comparative Example 3 81.7 15.8 11.5 29.5 V-1 (melt dripping) 388 Comparative Example 4 91.6 1.2 14.9 26.0 V-2 (melt dripping) 453 Comparative Example 5 91.9 1.0 15.3 21.5 NR (melt dripping) 537 NR indicates that the rating has not been passed.

[0103] in conclusion: The comprehensive performance comparison test data in Table 2 clearly reveals the advantages of the technical solution of the present invention.

[0104] First, regarding fundamental physical and optical properties, the samples from Examples 1 to 5 all maintained high transmittance, low haze, and excellent impact strength similar to pure PMMA (Comparative Example 1). In contrast, Comparative Examples 2 and 3, which employed conventional filler technology, showed deterioration in both optical and mechanical properties. This indicates that the additive system of the present invention, due to its molecular or nanoscale dispersion in the matrix, can effectively avoid performance losses caused by micron-scale fillers.

[0105] Secondly, the present invention demonstrates superior performance in terms of flame retardancy and thermal insulation. The limiting oxygen index (LOI) of all the sample examples was significantly higher than that of pure PMMA (Comparative Example 1), and the core examples (1, 2, 4, 5) all achieved the highest V-0 UL-94 rating with no melt dripping. The results of dynamic thermal insulation performance testing further highlight the core advantages of the present invention: the temperature rise on the unexposed side of the sample examples was extremely slow, far lower than that of all comparative examples.

[0106] Of particular note is the comparison with Comparative Example 4. Comparative Example 4 included the main functional components for ceramic formation and foaming, but lacked the crucial component D (a thermosensitive free radical inhibitor). Its test results (lower LOI, UL-94 rating V-2 with melt dripping, and a sharp increase in temperature on the unexposed side) showed a significant difference compared to Example 1. This comparison directly demonstrates the necessity of the self-regulating reaction process mechanism introduced by component D. Without this mechanism, even with the presence of functional components, the system cannot form a structurally stable and dense ceramicized foam insulation layer during the dynamic combustion process, leading to protective failure.

[0107] In summary, this invention, through a low-dosage, highly compatible composite additive system and the innovative introduction of a self-regulating reaction process mechanism, successfully resolves the contradiction between flame-retardant and heat-insulating properties and the inherent optical and mechanical properties of materials in traditional technologies, achieving a balance and improvement in the overall performance of the material.

Claims

1. A flame-retardant and heat-insulating acrylic sheet, characterized in that, It is polymerized from raw materials comprising the following parts by weight: Methyl methacrylate: 100 parts; Azobisisobutyronitrile: 0.1-0.5 parts; Component A: 1.0-5.0 parts; Component B: 1.0-5.0 parts; Component C: 3.0-8.0 parts; Component D: 0.1-1.0 parts; Wherein, component A is tris(2-hydroxyethyl)boronic acid ester, component B is octa(aminophenyl)cage-like silsesquioxane, component C is diethyldiethanolaminomethylphosphonic acid ester, and component D is pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

2. The flame-retardant and heat-insulating acrylic sheet according to claim 1, characterized in that, The weight parts of the raw materials are: Methyl methacrylate: 100 parts; Azobisisobutyronitrile: 0.3 parts; Component A: 3.0 parts; Component B: 3.0 parts; Component C: 5.5 parts; Component D: 0.5 parts.

3. The flame-retardant and heat-insulating acrylic sheet according to claim 1, characterized in that, Component A is prepared by reacting boric acid and triethanolamine under reflux in the presence of a dehydrating agent, followed by vacuum distillation.

4. The flame-retardant and heat-insulating acrylic sheet according to claim 1, characterized in that, Component C is prepared by reacting diethyl phosphite, diethanolamine and formaldehyde aqueous solution in a solvent, followed by solvent removal under reduced pressure.

5. The flame-retardant and heat-insulating acrylic sheet according to claim 4, characterized in that, During the reaction of component C, the internal temperature of the reaction system is maintained within the range of 15℃-30℃.

6. A method for preparing a flame-retardant and heat-insulating acrylic sheet, characterized in that, The method of applying the flame-retardant and heat-insulating acrylic sheet according to any one of claims 1-5 includes the following steps: S1. Add azobisisobutyronitrile initiator to methyl methacrylate monomer and stir continuously to form a solution; S2. Under stirring, add component A, component C and component D to the solution in step S1 in sequence, dissolve them evenly to form a premixed solution; S3. Add component B to the premixed solution and perform ultrasonic dispersion treatment to obtain a uniform slurry; S4. Perform vacuum degassing treatment on the slurry; S5. Pour the vacuum-degassed slurry into the mold and perform programmed temperature rise curing. S6. Cool and demold the cured product to obtain the flame-retardant and heat-insulating acrylic sheet.

7. The method for preparing a flame-retardant and heat-insulating acrylic sheet according to claim 6, characterized in that, The continuous stirring in step S1 is carried out at room temperature until the azobisisobutyronitrile initiator is completely dissolved.

8. The method for preparing a flame-retardant and heat-insulating acrylic sheet according to claim 6, characterized in that, The vacuum degassing process in step S4 is carried out at room temperature and a vacuum level of less than 1 kPa.

9. The method for preparing a flame-retardant and heat-insulating acrylic sheet according to claim 6, characterized in that, The programmed temperature curing in step S5 includes a first curing stage performed in a temperature range of 45℃-65℃, and a second curing stage performed in a temperature range of 65℃-110℃.

10. The method for preparing a flame-retardant and heat-insulating acrylic sheet according to claim 9, characterized in that, In the programmed temperature rise curing process, the process of rising from one isothermal stage to the next isothermal stage is carried out in a linear temperature rise manner.