A highly flame-retardant thermoplastic board for aviation interior and its preparation process

Abstract

The present invention discloses a highly flame-retardant thermoplastic plate for aviation interiors and a preparation process thereof, relating to the technical field of thermoplastic plates. The plate comprises a bottom layer, an intermediate layer, and a surface layer. The bottom layer and the surface layer are both non-woven fabrics, and the intermediate layer is made of the following components by weight: 80-100 parts of polycaprolactone, 20-40 parts of polylactic acid, 5-20 parts of a flame retardant, and 0.5-4 parts of a coupling agent. The present invention addresses the dual requirements of lightweight and durability for aviation equipment. While ensuring excellent deformation resistance, the plate can be processed through an integrated molding process, significantly improving assembly efficiency and reducing overall weight. At the same time, the material has a high flame retardant grade, generates very little smoke during combustion, and has no droplet phenomenon. It can still quickly self-extinguish in a high-oxygen environment, and its safety is significantly better than conventional products.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoplastic plates, and in particular to a highly flame-retardant thermoplastic plate for aviation interior decoration and a preparation process thereof. Background Art

[0002] Aviation interior materials are a core component of aircraft cabin safety design and occupant survival assurance, and their performance requirements are much higher than those of ordinary industrial materials. International airworthiness standards (such as FAR 25.853) impose strict restrictions on the flame retardancy, smoke density, toxicity release and other indicators of interior materials, requiring materials to have self-extinguishing properties, low smoke emissions and no droplets in fire scenarios, while also taking lightweighting into account to reduce fuel consumption. Such materials must also withstand long-term tests such as extreme temperature and humidity cycles and ultraviolet radiation in high-altitude environments to ensure dimensional stability and surface finish during service. At present, aviation interior materials are mainly used in components such as wall panels, luggage racks, and seat shells. Their comprehensive performance directly affects the efficiency of aircraft airworthiness certification and operational economy.

[0003] Thermoplastic sheets are becoming an important alternative to thermosetting composite materials due to their recyclability, high processing efficiency, and great design flexibility. Mainstream thermoplastic sheets in the market can be divided into several types based on the differences in the base resin: polypropylene (PP)-based sheets are low-cost and easy to injection mold, but their inherent flame retardancy is insufficient and they require high amounts of flame retardants, which leads to a significant increase in material density and deterioration in mechanical properties; polycarbonate (PC)-based sheets have excellent heat resistance, but the processing melt viscosity is high, making it difficult to mold complex components, and they are prone to producing droplets and toxic gases during combustion; polyetheretherketone (PEEK)-based materials have stable high-temperature resistance and self-extinguishing properties, but their high raw material costs and strict processing temperatures limit their large-scale application. In recent years, bio-based materials have attracted much attention due to their environmentally friendly properties. Polylactic acid (PLA), as a typical biodegradable polyester, has the potential for high rigidity and easy modification, but its inherent brittleness, low heat resistance, and easy hydrolysis seriously restrict its application in the aviation field. At the same time, polycaprolactone (PCL) has become the preferred component for blending modification due to its excellent low-temperature toughness, interfacial compatibility and processing fluidity, but its defects of low mechanical strength at room temperature and easy creep at high temperature still need to be overcome through optimization of the composite system.

[0004] The addition of flame retardants is a key technical approach to improving the airworthiness of thermoplastic panels. Halogen-based flame retardants, which were widely used in the early days, have been gradually phased out due to the release of highly toxic gases during combustion. Although inorganic flame retardants (such as aluminum hydroxide and boron nitride) are environmentally friendly, their high filling content leads to matrix interface defects, causing surface roughness and reduced impact performance of the panels. Although organic flame retardant systems such as phosphorus-nitrogen synergy can reduce the addition ratio, they face the problem of easy migration and decomposition in hot and humid environments and insufficient long-term stability. In addition, the traditional melt blending process makes it difficult to achieve nano-scale dispersion and directional arrangement of flame retardants, resulting in the inability to synergize the physical barrier effect and the gas-phase free radical quenching mechanism, which seriously limits the improvement of the flame retardant efficiency of the material.

[0005] CN107603021A discloses a fiber-reinforced thermoplastic board and a manufacturing process for traffic interior decoration using the thermoplastic board. The thermoplastic board is mainly composed of a reinforcement, a matrix, and a halogen-free flame retardant. The reinforcement is long glass fiber or continuous glass fiber, and the matrix is one or more of polypropylene, nylon 6, nylon 66, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene, polyester resin, polyphenylene sulfide, polyetherimide, polyetheretherketone, polycarbonate and acrylonitrile-butadiene-styrene alloy; the halogen-free flame retardant is one or more of polypropylene, glass fiber reinforced polypropylene, and polyolefin.

[0006] Currently, aviation interior thermoplastic panels face the following contradictions: it is difficult to achieve both improved flame retardant efficiency and maintained mechanical properties. The high addition of flame retardants leads to a simultaneous deterioration of the material's rigidity, toughness, and surface quality. Therefore, the industry urgently needs to develop a new generation of thermoplastic panels that are highly flame retardant, lightweight, durable, and economical to process through material system innovation and process breakthroughs to meet the dual needs of green aviation and safe airworthiness. Summary of the Invention

[0007] In order to address the shortcomings of the existing technology, the purpose of the present invention is to provide a highly flame-retardant thermoplastic board for aviation interiors and a preparation process thereof. In response to the dual requirements of lightweight and durability for aviation equipment, the board can be processed through an integrated molding process while ensuring excellent deformation resistance, significantly improving assembly efficiency and reducing overall weight; at the same time, the material has a high flame retardant grade, extremely low smoke production during combustion and no droplet phenomenon, and can still quickly self-extinguish in a high-oxygen environment, and its safety is significantly better than conventional products.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A highly flame-retardant thermoplastic plate for aviation interiors comprises a bottom layer, an intermediate layer, and a surface layer. The bottom layer and the surface layer are both non-woven fabrics, and the intermediate layer is made of the following components by weight: 80 to 100 parts of polycaprolactone, 20 to 40 parts of polylactic acid, 5 to 20 parts of a flame retardant, and 0.5 to 4 parts of a coupling agent.

[0010] Preferably, the method for preparing the flame retardant comprises the following steps:

[0011] (1) dispersing nano-boron nitride in isopropyl alcohol, ultrasonically exfoliating and centrifuging, collecting the precipitate after centrifugation, adding it to a sodium hydroxide solution, heating and stirring, filtering, washing, and drying the product to obtain hydroxylated boron nitride;

[0012] Preparation of hydroxylated boron nitride: Ultrasonic exfoliation destroys the van der Waals force between boron nitride layers, exposing the BN polar bonds at the edge of the layers; NaOH aqueous solution attacks the B atoms (B 3+ Lewis acidic sites), breaking the BN bond to generate B-OH and NH3 (BN+3H2O→B(OH)3+NH3↑), and the hydroxyl groups are preferentially anchored at the layer edge defects and step sites to form electron-rich surface active sites, providing chemical anchor points for subsequent coupling reactions.

[0013] Preferably, in step (1), the dosage ratio of nano-boron nitride, isopropyl alcohol, and sodium hydroxide solution is 10 g: 300-500 mL: 100-300 mL; the concentration of the sodium hydroxide solution is 1-5 mol / L; the ultrasonic stripping conditions are 40-60 kHz, 400-600 W ultrasonic treatment for 2-4 h; and the heating and stirring conditions are heating and stirring at 80-95° C. for 4-8 h.

[0014] (2) adding hydroxylated boron nitride and KH550 to an ethanol / water mixture, ultrasonically dispersing, adjusting the pH of the system, refluxing the reaction, centrifuging the product, washing with alcohol, and drying to obtain amino boron nitride;

[0015] Amination modification: KH550 (γ-aminopropyltriethoxysilane) undergoes stepwise hydrolysis in an ethanol / water system. The ethoxy groups (-OCH2CH3) first hydrolyze to silanols (-Si-OH). Subsequently, under weakly acidic conditions, the silanols react with the B-OH groups on the BN-OH surface through condensation, removing H2O and forming a stable Si-OB covalent bond. Self-condensation of unoccupied silanol groups is inhibited (pH control), ensuring that the amino groups (-NH2) are oriented outward, creating an "amino-siloxane-boron nitride" sandwich interface structure.

[0016] Preferably, in step (2), the usage ratio of hydroxylated boron nitride, KH550, and ethanol / water mixture is 10 g:1-5 mL:100-150 mL; and the volume ratio of ethanol to water in the ethanol / water mixture is 3-4:1.

[0017] Preferably, in step (2), the pH of the system is adjusted to 4.5-5.5 with glacial acetic acid; and the reflux reaction conditions are reflux stirring at 60-75° C. for 6-12 hours.

[0018] (3) dispersing the amino boron nitride in DMF, adding succinic anhydride and triethylamine, stirring and reacting under a nitrogen atmosphere, centrifuging, washing, and drying the product to obtain carboxylated boron nitride;

[0019] Carboxylation reaction: The amino group (-NH2) on the BN-NH2 surface acts as a nucleophile, attacking the cyclic anhydride carbonyl group of succinic anhydride, triggering the anhydride ring opening. The amino group forms an amide bond (-NH-C(O)-) with one carbonyl group, simultaneously releasing another free carboxylic acid group (-COOH). Triethylamine (Et3N) acts as a proton acceptor, neutralizing the carboxylic acid generated in the reaction and shifting the reaction equilibrium toward the product, ultimately grafting a high density of carboxylic acid functional groups onto the boron nitride surface.

[0020] Preferably, in step (3), the usage ratio of amination boron nitride, DMF, succinic anhydride and triethylamine is 10 g: 100-150 mL: 8-15 g: 1-3 mL.

[0021] Preferably, in step (3), the stirring reaction conditions are 45-60° C. for 8-16 hours; and the product is washed alternately with acetone and deionized water for 3-5 times.

[0022] (4) dispersing carboxylated boron nitride in deionized water, adding aluminum diethylphosphinate, adjusting the pH of the system, stirring the reaction, centrifuging, washing, and freeze-drying the product to obtain a flame retardant.

[0023] Aluminum ion chelation: At pH 3-4, the carboxylic acid group is partially ionized to carboxylate (-COO-) and reacts with the Al3 + Multidentate coordination occurs: each Al3 + It can simultaneously form an octahedral coordination structure with 3 to 4 oxygen atoms of carboxyl groups (Al3 + ←:OOCR), phosphinate reacts with Al3 through P=O double bond + This organic-inorganic hybrid network promotes the formation of dense carbon layer during combustion and generates auxiliary coordination through Al3 + The Lewis acid catalyzes the quenching of free radicals, achieving synergistic flame retardancy between the condensed phase and the gas phase.

[0024] Preferably, in step (4), the ratio of carboxylated boron nitride, deionized water, and aluminum diethylphosphinate is 10 g: 200-400 mL: 3-8 g; the pH of the system is adjusted to 3-4 with dilute hydrochloric acid; and the stirring reaction conditions are 65-80° C. and the stirring reaction is carried out for 2-5 hours.

[0025] Preferably, the coupling agent is one or more of a phthalate coupling agent, a silane coupling agent, and an epoxy coupling agent.

[0026] Preferably, the bottom layer has a thickness of 0.2 to 0.8 mm, the surface layer has a thickness of 0.2 to 0.8 mm, and the middle layer has a thickness of 3 to 13 mm.

[0027] Preferably, the non-woven fabric has a gram weight of 80 to 320 g / m 2 One or more of polyester non-woven fabric, polypropylene non-woven fabric, nylon non-woven fabric, and chloroprene non-woven fabric.

[0028] The present invention also claims protection for a preparation process of the highly flame-retardant thermoplastic plate for aviation interior, comprising the following steps: blending polycaprolactone, polylactic acid, a flame retardant, and a coupling agent at 100-300°C for 3-10 minutes, and then compression molding at 50-300°C to obtain an intermediate layer; stacking the bottom layer, the intermediate layer, and the surface layer in sequence, pressing them in a Teflon press at 120-200°C and 1-6 bar for 1-5 minutes, and obtaining the highly flame-retardant thermoplastic plate for aviation interior after cooling.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention provides a highly flame-retardant thermoplastic sheet for aviation interiors. It features a three-layer composite structure, with a non-woven surface layer providing surface protection and interface support, a middle functional layer serving as the core functional carrier, and a bottom layer providing a stable bond with the cabin interior structure. This structure, through a layered functional design, comprehensively improves flame retardancy, mechanical strength, and environmental adaptability while maintaining lightweight construction. In the middle layer, polycaprolactone provides excellent flexibility and processing fluidity, balancing the sheet's adaptability when forming complex curved surfaces. Polylactic acid, with its high modulus, imparts rigid support to the sheet, inhibiting deformation in high-temperature environments. A coupling agent enhances the interfacial bonding between the two polymers through chemical bonding, reducing internal stress concentration within the material. The flame retardant forms a stable dispersion with the matrix, creating a dense carbonization barrier during combustion to block heat conduction and the diffusion of combustible gases. The meticulous proportioning and synergistic effects of these components ensure that the middle layer combines high flame retardancy, dimensional stability, and process adaptability, meeting the multi-dimensional material performance requirements for aviation interiors.

[0031] 2. The present invention provides a high-performance flame retardant with boron nitride nanosheets as carriers. Its layered structure forms a parallel physical barrier in the matrix, which significantly delays the transfer of heat to the interior of the material by reflecting / scattering thermal radiation and extending the heat conduction path. At the same time, the chemical inertness of boron nitride can inhibit the occurrence of oxidation reactions during combustion, and its high thermal conductivity can help to evenly disperse heat, prevent local temperature accumulation, and thus slow down the overall thermal degradation rate. More importantly, the amino and carboxyl groups modified on the surface of boron nitride significantly improve the dispersibility of the flame retardant in the matrix through hydrogen bonding with polylactic acid molecules, avoid agglomeration, and lay the foundation for uniform distribution for subsequent synergistic flame retardancy. Aluminum diethylphosphinate, as an organic flame retardant component, decomposes into aluminum phosphate and polymetaphosphoric acid in the early stage of heating. The former catalyzes the dehydration of the material surface into carbon, forming a dense expanded carbon layer, and the latter releases phosphorus-containing free radicals (PO·, HPO·) to capture H· and OH· active free radicals in the gas phase, interrupting the combustion chain reaction. The two produce a synergistic flame retardant effect: the boron nitride sheets support the carbon layer structure to prevent high-temperature collapse, and the decomposition products of aluminum phosphinate fill the gaps between the boron nitride sheets to form a continuous closed barrier network, realizing the dual flame retardant mechanisms of gas-phase free radical quenching and condensed-phase thermal insulation. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0033] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased from commercial sources or synthesized from commercially purchased raw materials.

[0034] The average molecular weight of polycaprolactone is 8×10 4 , model CAPA6800;

[0035] The average molecular weight of polylactic acid is 1.2×10 5 , model number is 4032D;

[0036] Hexagonal boron nitride was purchased from Beijing Huawei Ruike Chemical Co., Ltd. with a purity of 99%.

[0037] A process for preparing a highly flame-retardant thermoplastic plate for aviation interiors comprises the following steps:

[0038] (1) 10 g of nano-boron nitride was dispersed in 300-500 mL of isopropanol, ultrasonically treated at 40-60 kHz and 400-600 W for 2-4 h, and then centrifuged. The precipitate after centrifugation was collected and added to 100-300 mL of 1-5 mol / L sodium hydroxide solution. The mixture was heated and stirred at 80-95° C. for 4-8 h. The product was filtered, washed, and dried to obtain hydroxylated boron nitride.

[0039] (2) 10 g of hydroxylated boron nitride and 1-5 mL of KH550 were added to 100-150 mL of an ethanol / water mixture (the volume ratio of ethanol to water was 3-4:1), and ultrasonically dispersed. The pH of the system was adjusted to 4.5-5.5 with glacial acetic acid, and the mixture was stirred under reflux at 60-75°C for 6-12 h. The product was centrifuged, washed with alcohol, and dried to obtain amino boron nitride.

[0040] (3) Dispersing 10 g of amino boron nitride in 100-150 mL of DMF, adding 8-15 g of succinic anhydride and 1-3 mL of triethylamine, stirring and reacting at 45-60° C. under a nitrogen atmosphere for 8-16 h, centrifuging the product, washing the product with acetone and deionized water alternately for 3-5 times, and drying to obtain carboxylated boron nitride;

[0041] (4) Dispersing 10 g of carboxylated boron nitride in 200-400 mL of deionized water, adding 3-8 g of aluminum diethylphosphinate, adjusting the pH of the system to 3-4 with dilute hydrochloric acid, stirring and reacting at 65-80° C. for 2-5 h, centrifuging, washing, and freeze-drying the product to obtain a flame retardant;

[0042] (5) 80-100 parts of polycaprolactone, 20-40 parts of polylactic acid, 5-20 parts of flame retardant, and 0.5-4 parts of coupling agent are blended at 100-300° C. for 3-10 minutes, and then compression molded at 50-300° C. to obtain an intermediate layer; the bottom layer, the intermediate layer, and the surface layer are stacked in sequence, pressed in a Teflon press at 120-200° C. and 1-6 bar for 1-5 minutes, and cooled to obtain the highly flame-retardant thermoplastic plate for aviation interior.

[0043] The coupling agent is one or more of a phthalate coupling agent, a silane coupling agent, and an epoxy coupling agent.

[0044] The thickness of the bottom layer is 0.2-0.8 mm, the thickness of the surface layer is 0.2-0.8 mm, and the thickness of the middle layer is 3-13 mm.

[0045] The present invention will be further described below with reference to specific examples.

[0046] Example 1

[0047] A process for preparing a highly flame-retardant thermoplastic plate for aviation interiors comprises the following steps:

[0048] (1) 10 g of nano-boron nitride was dispersed in 400 mL of isopropanol, ultrasonically treated at 50 kHz and 500 W for 4 h, and then centrifuged. The precipitate after centrifugation was collected and added to 200 mL of 2 mol / L sodium hydroxide solution. The mixture was heated and stirred at 95 ° C for 4 h. The product was filtered, washed, and dried to obtain hydroxylated boron nitride.

[0049] (2) 10 g of hydroxylated boron nitride and 5 mL of KH550 were added to 150 mL of ethanol / water mixture (the volume ratio of ethanol to water was 4:1), and ultrasonically dispersed. The pH of the system was adjusted to 5.0 with glacial acetic acid, and the mixture was stirred under reflux at 75°C for 6 h. The product was centrifuged, washed with alcohol, and dried to obtain amino boron nitride.

[0050] (3) Disperse 10 g of amino-boron nitride in 150 mL of DMF, add 15 g of succinic anhydride and 3 mL of triethylamine, and stir the mixture at 60 °C under a nitrogen atmosphere for 8 h. Centrifuge the product, wash it four times with acetone and deionized water, and dry it to obtain carboxylated boron nitride.

[0051] (4) Disperse 10 g of carboxylated boron nitride in 400 mL of deionized water, add 8 g of aluminum diethylphosphinate, adjust the pH of the system to 3.5 with dilute hydrochloric acid, stir and react at 80° C. for 2 h, centrifuge, wash, and freeze-dry the product to obtain a flame retardant;

[0052] (5) 1000 g of polycaprolactone, 400 g of polylactic acid, 200 g of flame retardant, and 40 g of KH560 coupling agent were blended at 200 ° C for 6 minutes, and then compression molded at 200 ° C to obtain an intermediate layer; the bottom layer, the intermediate layer, and the surface layer were stacked in sequence, pressed at 160 ° C and 3 bar for 3 minutes in a Teflon press, and cooled to obtain the high flame retardant thermoplastic plate for aviation interior.

[0053] The bottom layer is 0.5mm thick and weighs 100g / m 2 The polypropylene non-woven fabric has a thickness of 0.5 mm and a weight of 100 g / m 2 The polypropylene non-woven fabric has a thickness of 10 mm.

[0054] Example 2

[0055] A process for preparing a highly flame-retardant thermoplastic plate for aviation interiors comprises the following steps:

[0056] (1) 10 g of nano-boron nitride was dispersed in 400 mL of isopropanol, ultrasonically treated at 50 kHz and 500 W for 3 h, and then centrifuged. The precipitate after centrifugation was collected and added to 200 mL of 2 mol / L sodium hydroxide solution. The mixture was heated and stirred at 90 ° C for 5 h. The product was filtered, washed, and dried to obtain hydroxylated boron nitride.

[0057] (2) 10 g of hydroxylated boron nitride and 4 mL of KH550 were added to 150 mL of ethanol / water mixture (volume ratio of ethanol to water was 4:1), ultrasonically dispersed, and the pH of the system was adjusted to 5.0 with glacial acetic acid. The mixture was stirred under reflux at 70 °C for 8 h. The product was centrifuged, washed with alcohol, and dried to obtain amino boron nitride.

[0058] (3) Disperse 10 g of amino boron nitride in 150 mL of DMF, add 12 g of succinic anhydride and 2 mL of triethylamine, and react at 55 °C under nitrogen atmosphere for 10 h. Centrifuge the product, wash the product with acetone and deionized water alternately 4 times, and dry to obtain carboxylated boron nitride;

[0059] (4) Disperse 10 g of carboxylated boron nitride in 400 mL of deionized water, add 6 g of aluminum diethylphosphinate, adjust the pH of the system to 3.5 with dilute hydrochloric acid, stir and react at 75° C. for 3 h, centrifuge, wash, and freeze-dry the product to obtain a flame retardant;

[0060] (5) 950 g of polycaprolactone, 350 g of polylactic acid, 150 g of flame retardant, and 30 g of KH560 coupling agent were blended at 200 ° C for 6 minutes, and then compression molded at 200 ° C to obtain an intermediate layer; the bottom layer, the intermediate layer, and the surface layer were stacked in sequence, pressed in a Teflon press at 160 ° C and 3 bar for 3 minutes, and cooled to obtain the highly flame retardant thermoplastic plate for aviation interior.

[0061] The bottom layer is 0.5mm thick and weighs 100g / m 2 The polypropylene non-woven fabric has a thickness of 0.5 mm and a weight of 100 g / m 2 The polypropylene non-woven fabric has a thickness of 10 mm.

[0062] Example 3

[0063] A process for preparing a highly flame-retardant thermoplastic plate for aviation interiors comprises the following steps:

[0064] (1) 10 g of nano-boron nitride was dispersed in 400 mL of isopropanol, ultrasonically treated at 50 kHz and 500 W for 3 h, and then centrifuged. The precipitate after centrifugation was collected and added to 200 mL of 2 mol / L sodium hydroxide solution. The mixture was heated and stirred at 85° C. for 7 h. The product was filtered, washed, and dried to obtain hydroxylated boron nitride.

[0065] (2) 10 g of hydroxylated boron nitride and 2 mL of KH550 were added to 150 mL of ethanol / water mixture (the volume ratio of ethanol to water was 4:1), and ultrasonically dispersed. The pH of the system was adjusted to 5.0 with glacial acetic acid, and the reaction was refluxed and stirred at 65°C for 10 h. The product was centrifuged, washed with alcohol, and dried to obtain amino boron nitride;

[0066] (3) Disperse 10 g of amino-boron nitride in 150 mL of DMF, add 10 g of succinic anhydride and 2 mL of triethylamine, and react at 50 °C under nitrogen atmosphere for 12 h. Centrifuge the product, wash the product with acetone and deionized water alternately 4 times, and dry to obtain carboxylated boron nitride;

[0067] (4) Disperse 10 g of carboxylated boron nitride in 400 mL of deionized water, add 5 g of aluminum diethylphosphinate, adjust the pH of the system to 3.5 with dilute hydrochloric acid, stir and react at 70° C. for 4 h, centrifuge, wash, and freeze-dry the product to obtain a flame retardant;

[0068] (5) 850 g of polycaprolactone, 250 g of polylactic acid, 100 g of flame retardant, and 20 g of KH560 coupling agent were blended at 200 ° C for 6 minutes, and then compression molded at 200 ° C to obtain an intermediate layer; the bottom layer, the intermediate layer, and the surface layer were stacked in sequence, pressed at 160 ° C and 3 bar for 3 minutes in a Teflon press, and cooled to obtain the high flame retardant thermoplastic plate for aviation interior.

[0069] The bottom layer is 0.5mm thick and weighs 100g / m 2 The polypropylene non-woven fabric has a thickness of 0.5 mm and a weight of 100 g / m 2 The polypropylene non-woven fabric has a thickness of 10 mm.

[0070] Example 4

[0071] A process for preparing a highly flame-retardant thermoplastic plate for aviation interiors comprises the following steps:

[0072] (1) 10 g of nano-boron nitride was dispersed in 400 mL of isopropanol, ultrasonically treated at 50 kHz and 500 W for 2 h, and then centrifuged. The precipitate after centrifugation was collected and added to 200 mL of 2 mol / L sodium hydroxide solution. The mixture was heated and stirred at 80° C. for 8 h. The product was filtered, washed, and dried to obtain hydroxylated boron nitride.

[0073] (2) 10 g of hydroxylated boron nitride and 1 mL of KH550 were added to 150 mL of ethanol / water mixture (the volume ratio of ethanol to water was 4:1), and ultrasonically dispersed. The pH of the system was adjusted to 5.0 with glacial acetic acid, and the mixture was stirred under reflux at 60°C for 12 h. The product was centrifuged, washed with alcohol, and dried to obtain amino boron nitride.

[0074] (3) Disperse 10 g of amino-boron nitride in 150 mL of DMF, add 8 g of succinic anhydride and 1 mL of triethylamine, and stir the mixture at 45 °C under a nitrogen atmosphere for 16 h. Centrifuge the product, wash it four times with acetone and deionized water, and dry it to obtain carboxylated boron nitride.

[0075] (4) Disperse 10 g of carboxylated boron nitride in 400 mL of deionized water, add 3 g of aluminum diethylphosphinate, adjust the pH of the system to 3.5 with dilute hydrochloric acid, stir and react at 65° C. for 5 h, centrifuge, wash, and freeze-dry the product to obtain a flame retardant;

[0076] (5) 800 g of polycaprolactone, 200 g of polylactic acid, 50 g of flame retardant, and 5 g of KH560 coupling agent were blended at 200 ° C for 6 minutes, and then compression molded at 200 ° C to obtain an intermediate layer; the bottom layer, the intermediate layer, and the surface layer were stacked in sequence, pressed at 160 ° C and 3 bar for 3 minutes in a Teflon press, and cooled to obtain the high flame retardant thermoplastic plate for aviation interior.

[0077] The bottom layer is 0.5mm thick and weighs 100g / m 2 The polypropylene non-woven fabric has a thickness of 0.5 mm and a weight of 100 g / m 2 The polypropylene non-woven fabric has a thickness of 10 mm.

[0078] Comparative Example 1

[0079] A process for preparing a thermoplastic plate comprises the following steps:

[0080] (1) 10 g of nano-boron nitride was dispersed in 400 mL of isopropanol, ultrasonically treated at 50 kHz and 500 W for 4 h, and then centrifuged. The precipitate after centrifugation was collected and added to 200 mL of 2 mol / L sodium hydroxide solution. The mixture was heated and stirred at 95 ° C for 4 h. The product was filtered, washed, and dried to obtain hydroxylated boron nitride.

[0081] (2) 10 g of hydroxylated boron nitride and 5 mL of KH550 were added to 150 mL of ethanol / water mixture (volume ratio of ethanol to water was 4:1), and ultrasonically dispersed. The pH of the system was adjusted to 5.0 with glacial acetic acid, and the mixture was stirred under reflux at 75 °C for 6 h. The product was centrifuged, washed with alcohol, and dried to obtain amino boron nitride.

[0082] (3) Disperse 10 g of amino-boron nitride in 150 mL of DMF, add 15 g of succinic anhydride and 3 mL of triethylamine, and stir the mixture at 60 °C under a nitrogen atmosphere for 8 h. Centrifuge the product, wash it four times with acetone and deionized water, and dry it to obtain carboxylated boron nitride.

[0083] (4) 1000 g of polycaprolactone, 400 g of polylactic acid, 110 g of carboxylated boron nitride, 90 g of aluminum diethylphosphinate, and 40 g of KH560 coupling agent were blended at 200° C. for 6 min, and then compression molded at 200° C. to obtain an intermediate layer; the bottom layer, the intermediate layer, and the surface layer were stacked in sequence, pressed in a Teflon press at 160° C. and 3 bar for 3 min, and cooled to obtain the thermoplastic plate.

[0084] The bottom layer is 0.5mm thick and weighs 100g / m 2 The polypropylene non-woven fabric has a thickness of 0.5 mm and a weight of 100 g / m 2The polypropylene non-woven fabric has a thickness of 10 mm.

[0085] Comparative Example 2

[0086] A process for preparing a thermoplastic plate comprises the following steps:

[0087] (1) 10 g of nano-boron nitride was dispersed in 400 mL of isopropanol, ultrasonically treated at 50 kHz and 500 W for 4 h, and then centrifuged. The precipitate after centrifugation was collected and added to 200 mL of 2 mol / L sodium hydroxide solution. The mixture was heated and stirred at 95 ° C for 4 h. The product was filtered, washed, and dried to obtain hydroxylated boron nitride.

[0088] (2) 1000 g of polycaprolactone, 400 g of polylactic acid, 110 g of hydroxylated boron nitride, 90 g of aluminum diethylphosphinate, and 40 g of KH560 coupling agent were blended at 200° C. for 6 min, and then compression molded at 200° C. to obtain an intermediate layer; the bottom layer, the intermediate layer, and the surface layer were stacked in sequence, pressed in a Teflon press at 160° C. and 3 bar for 3 min, and cooled to obtain the thermoplastic plate.

[0089] The bottom layer is 0.5mm thick and weighs 100g / m 2 The polypropylene non-woven fabric has a thickness of 0.5 mm and a weight of 100 g / m 2 The polypropylene non-woven fabric has a thickness of 10 mm.

[0090] The thermoplastic panels prepared in Examples 1 to 4 were tested for performance according to GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels". The final results showed that the static bending strength was ≥45.3 MPa, the internal bonding strength was ≥1.76 MPa, the water absorption thickness expansion rate was ≤4.7%, the moisture resistance was ≤0.14 MPa, and the density was 0.95-1.02 g / cm 2 .

[0091] The intermediate layer samples of the embodiments and comparative examples were prepared into dumbbell-shaped splines of 50 mm × 4 mm × 2 mm, and tensile tests were carried out using a universal testing machine at a tensile speed of 50 mm / min with reference to GB / T1040.2-2022 "Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics"; the impact strength was determined with reference to GB / T 1843-2008 "Determination of cantilever beam impact strength of plastics"; the sample was made into a 50 mm × 10 mm × 2 mm spline, L0 was recorded, and then it was placed in a 70 ° C oven and held for 5 minutes. It was stretched 20 mm at a speed of 20 mm / min and recorded as L1. After cooling with the load for 5 minutes, L2 was recorded, and the shape fixation rate = (L2-L0) / (L1-L0) was calculated; the cooled sample was then placed in the oven again for 5 minutes to obtain L2, and the shape recovery rate = (L2-L3) / (L2-L0) was calculated; the specific data are shown in Table 1.

[0092] Table 1 Test results of mechanical properties of the intermediate layer

[0093]

[0094] The intermediate layers prepared in Examples 1-4 and Comparative Examples 1-2 were tested for limiting oxygen index according to GB / T 2406.3-2022, "Plastics - Determination of Combustion Behavior by the Oxygen Index Method - Part 3: High Temperature Tests." Smoke density was tested according to GB / T 8323.2-2008, "Plastics - Smoke Generation - Part 2: Single Chamber Test Method for Determination of Smoke Density." The UL94-5VA vertical combustion test was conducted on samples with a size of 125±5 mm x 13±0.5 mm x original thickness, with a maximum thickness of no more than 13 mm and a flame height of 125 mm. Specific data are shown in Table 2.

[0095] Table 2 Test results of flame retardant properties of the middle layer

[0096]

[0097] In Comparative Example 1, the modified boron nitride improves its dispersibility in the matrix through surface amino / carboxyl groups, but it is only in physical blending contact with aluminum diethylphosphinate and lacks chemical bonding. The carbon layer generated by aluminum diethylphosphinate cannot be anchored on the surface of the boron nitride sheet, resulting in loose interface bonding between the two. During the combustion process, the gas phase free radical quenching effect of aluminum diethylphosphinate and the condensed phase thermal insulation barrier of boron nitride are spatially mismatched due to random distribution, and the synergistic efficiency is significantly reduced. In addition, in the unchelated state, the carbon layer generated by aluminum diethylphosphinate has a porous and loose structure. Although the boron nitride sheet is evenly dispersed, it fails to cross-link with the carbon layer. The carbon layer is prone to cracking at high temperatures, and the barrier performance is reduced.

[0098] In Comparative Example 2, the unmodified boron nitride (BN) severely aggregates within the matrix due to surface inertness, resulting in disordered stacking of the layers and an inability to form an effective parallel thermal barrier. The catalytic reaction of aluminum diethylphosphinate and the physical barrier effect of BN are completely disconnected: the decomposition products of aluminum diethylphosphinate are randomly distributed within the matrix, unable to accumulate at the combustion interface, resulting in disordered and fragmented char growth. Furthermore, localized heat concentration at the edges of the BN aggregates accelerates the pyrolysis of the resin, releasing large amounts of smoke. This spatial isolation between the two leads to the ineffectiveness of the flame retardant network, allowing heat and oxygen to rapidly penetrate through the unprotected "barren zones," further deteriorating smoke suppression capabilities.

[0099] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A highly flame-retardant thermoplastic board for aviation interior, comprising a bottom layer, an intermediate layer, and a surface layer, characterized in that: The bottom layer and the surface layer are both non-woven fabrics, and the middle layer is made of the following components in parts by weight: 80-100 parts of polycaprolactone, 20-40 parts of polylactic acid, 5-20 parts of flame retardant, and 0.5-4 parts of coupling agent; The preparation method of the flame retardant comprises the following steps: (1) dispersing nano-boron nitride in isopropyl alcohol, ultrasonically exfoliating and centrifuging, collecting the precipitate after centrifugation, adding it to a sodium hydroxide solution, heating and stirring, filtering, washing, and drying the product to obtain hydroxylated boron nitride; (2) adding hydroxylated boron nitride and KH550 to an ethanol / water mixture, ultrasonically dispersing, adjusting the pH of the system, refluxing the reaction, centrifuging the product, washing with alcohol, and drying to obtain amino boron nitride; (3) dispersing the amino boron nitride in DMF, adding succinic anhydride and triethylamine, stirring and reacting under a nitrogen atmosphere, centrifuging, washing, and drying the product to obtain carboxylated boron nitride; (4) dispersing carboxylated boron nitride in deionized water, adding aluminum diethylphosphinate, adjusting the pH of the system, stirring the reaction, centrifuging, washing, and freeze-drying the product to obtain a flame retardant.

2. The highly flame-retardant thermoplastic plate for aviation interior according to claim 1, characterized in that: In step (1), the usage ratio of nano-boron nitride, isopropyl alcohol, and sodium hydroxide solution is 10 g: 300-500 mL: 100-300 mL; the concentration of the sodium hydroxide solution is 1-5 mol / L; the ultrasonic stripping conditions are 40-60 kHz, 400-600 W ultrasonic treatment for 2-4 h; and the heating and stirring conditions are heating and stirring at 80-95° C. for 4-8 h.

3. The highly flame-retardant thermoplastic plate for aviation interior according to claim 1, characterized in that: In step (2), the dosage ratio of hydroxylated boron nitride, KH550, and ethanol / water mixture is 10 g:1-5 mL:100-150 mL; and the volume ratio of ethanol to water in the ethanol / water mixture is 3-4:

1.

4. The highly flame-retardant thermoplastic plate for aviation interior according to claim 1, characterized in that: In step (2), the pH of the system is adjusted to 4.5-5.5 with glacial acetic acid; the reflux reaction conditions are reflux stirring at 60-75° C. for 6-12 hours.

5. The highly flame-retardant thermoplastic plate for aviation interior according to claim 1, characterized in that: In step (3), the usage ratio of amination boron nitride, DMF, succinic anhydride and triethylamine is 10 g: 100-150 mL: 8-15 g: 1-3 mL.

6. The highly flame-retardant thermoplastic plate for aviation interior according to claim 1, characterized in that: In step (3), the stirring reaction conditions are 45-60° C. and 8-16 hours; the product is washed alternately with acetone and deionized water for 3-5 times.

7. The highly flame-retardant thermoplastic plate for aviation interior according to claim 1, characterized in that: In step (4), the ratio of carboxylated boron nitride, deionized water, and aluminum diethylphosphinate is 10 g: 200-400 mL: 3-8 g; the pH of the system is adjusted to 3-4 with dilute hydrochloric acid; and the stirring reaction conditions are 65-80° C. and the stirring reaction is carried out for 2-5 hours.

8. The highly flame-retardant thermoplastic plate for aviation interior according to claim 1, characterized in that: The coupling agent is one or more of a phthalate coupling agent, a silane coupling agent, and an epoxy coupling agent.

9. A process for preparing a highly flame-retardant thermoplastic plate for aviation interiors according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: blending polycaprolactone, polylactic acid, a flame retardant and a coupling agent at 100-300° C. for 3-10 minutes, and then compression molding at 50-300° C. to obtain an intermediate layer; stacking the bottom layer, the intermediate layer and the surface layer in sequence, pressing them in a Teflon press at 120-200° C. and 1-6 bar for 1-5 minutes, and cooling to obtain the high flame retardant thermoplastic plate for aviation interior.

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