A flame-retardant phenolic resin molding compound and a method for preparing the same

Abstract

The application discloses a kind of flame-retardant phenolic resin molding compound and preparation method thereof, the composition includes by mass fraction: cashew shell oil modified phenolic resin 35-50 parts, diethylphosphinic acid aluminum 8-15 parts, ammonium polyphosphate 5-10 parts, melamine cyanurate 3-6 parts, glass fiber 25-40 parts, silicone modified magnesium-aluminum layered double hydroxide 2-5 parts, curing agent 5-8 parts and release agent 0.5-1.5 parts.The application is designed by N-P-Si ternary synergistic flame-retardant system and cashew shell oil toughening, so that the limiting oxygen index of molding compound reaches 35-38%, UL94 flame-retardant grade reaches V-0 level (1.6 mm), smoke density Ds (max) is lower than 150, bending strength reaches 350-410 MPa, impact strength reaches 38-48 kJ / m², and the comprehensive performance meets FAR 25.853 aviation interior material flame-retardant standard.

Description

Technical Field

[0001] This invention relates to the field of thermosetting polymer materials technology, specifically to a flame-retardant phenolic resin molding compound composition and its preparation method. Background Technology

[0002] Civil aviation safety is one of the most stringent regulatory systems in the global transportation sector. The flame retardant properties of aircraft cabin interior materials are directly related to passenger safety. Annex F of FAR 25.853, established by the U.S. Federal Aviation Administration (FAA), specifies legal testing requirements for aircraft interior materials, including vertical burning (12-second / 60-second burning test), heat release rate (OSU 65 / 65 index), and smoke density (Ds). Based on this, the industry commonly uses the Limiting Oxygen Index (LOI, test standard ISO 4589 / ASTM D2863) as an auxiliary indicator to characterize the flame retardant properties of materials. High-quality aircraft interior structural components using phenolic molding compounds typically require an LOI ≥30%, a UL94 flame retardant rating of V-0, a smoke density (Ds(max)) not exceeding 200, and toxic gas release below specified thresholds (for specific components such as seat cushions, padding, and insulation materials). Meanwhile, interior structural components must also meet sufficient mechanical strength (bending strength not less than 300 MPa) and impact toughness (impact strength not less than 35 kJ / m²) to withstand vibration loads during flight and impacts during passenger use.

[0003] Phenolic resin is the preferred matrix resin for aerospace interior composite materials due to its excellent heat resistance (long-term operating temperature of about 150-180℃, short-term temperature resistance up to 250℃), high char residue (60-70% char residue at 600℃) and inherent flame retardancy (LOI of about 32-36%). However, ordinary phenolic resin molding compounds have the following technical limitations: First, they are brittle. After curing, ordinary phenolic resins have high cross-linking density and strong molecular chain rigidity, and their impact strength is usually only 15-25 kJ / m², which is far lower than the toughness requirement (greater than or equal to 35 kJ / m²) for aerospace interior parts. They are prone to chipping and cracking during molding, demolding, and assembly. Second, traditional brominated flame retardant systems are facing environmental bans. The EU REACH regulation and the FAA have increasingly stringent environmental requirements for aerospace materials, and brominated flame retardants such as decabromodiphenyl ether have been included in the prohibited list. Third, additive inorganic flame retardants have poor compatibility with the phenolic resin matrix. Adding large amounts (usually accounting for 20-30% of the total formula) leads to a sharp decrease in resin fluidity and a significant deterioration in mechanical strength.

[0004] The existing technologies have the following common bottlenecks in addressing the technical requirements of flame-retardant phenolic molding compounds for aviation interiors: (1) It is difficult to achieve both toughening and flame retardancy. Increasing toughness usually requires the introduction of flexible segments, but this will reduce the crosslinking density and char residue, thereby weakening the flame retardant performance; (2) The efficiency of a single flame retardant route is low. Relying solely on phosphorus-based or nitrogen-based flame retardants requires a large amount of addition to achieve the target flame retardant level, resulting in severe deterioration of mechanical properties; (3) There is a lack of synergistic design between the NP-Si ternary synergistic flame retardant system and the toughening system. The existing technologies have not systematically integrated nitrogen-based gas phase flame retardancy, phosphorus-based condensed phase flame retardancy, and silicon-based ceramic barrier, and cannot maximize the flame retardant efficiency.

[0005] Therefore, developing a halogen-free flame-retardant phenolic resin molding compound composition that combines high flame retardancy (LOI ≥ 35%, UL94 V-0 rating, Ds(max) ≤ 150), high toughness (impact strength ≥ 35 kJ / m²), high mechanical strength (flexural strength ≥ 300 MPa), and good processability (spiral flow length ≥ 200 mm) is of clear engineering necessity and important strategic significance for meeting the supporting requirements of domestically produced large aircraft C919 and C929. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide a flame-retardant phenolic resin molding compound composition and its preparation method, so as to overcome the technical bottleneck of existing phenolic molding compounds in aviation interior applications where flame retardancy, toughness and mechanical strength are difficult to balance, and to meet the comprehensive performance requirements of civil aircraft cabin interior structural components.

[0007] According to a first aspect of this disclosure, a flame-retardant phenolic resin molding compound composition is provided, comprising, by weight parts: Cashew shell oil modified phenolic resin 35-50 parts; 8-15 parts of aluminum diethylphosphinate; 5-10 parts of ammonium polyphosphate; 3-6 parts of melamine cyanurate; 25-40 parts glass fiber; Organosilicon-modified magnesium-aluminum layered double hydroxide, 2-5 parts; 5-8 parts of curing agent.

[0008] In one embodiment of this disclosure, the cashew nut shell oil modified phenolic resin is prepared by polycondensation of phenol, cashew nut shell oil and formaldehyde under an alkaline catalyst. The cashew nut shell oil has a mass substitution rate of 20-35% for phenol, a number average molecular weight of 800-1500, and a softening point of 85-110°C.

[0009] In one embodiment of this disclosure, the aluminum diethylphosphonate has an average particle size of 10-50 micrometers; and / or the ammonium polyphosphate is type II ammonium polyphosphate with a degree of polymerization greater than 1000 and a solubility of less than 0.5 g / 100 mL water; and / or the melamine cyanurate has a particle size of 5-30 micrometers.

[0010] In one embodiment of this disclosure, the interlayer spacing of the organosilicon-modified magnesium-aluminum layered double hydroxide is 1.5-3.0 nm, and the organosilicon grafting rate is 5-12%.

[0011] In one embodiment of this disclosure, the method for preparing the organosilicon-modified magnesium-aluminum layered double hydroxide includes dispersing the magnesium-aluminum layered double hydroxide in an ethanol / water mixed solvent, adding an aminosilane coupling agent, and reacting at 70-80°C for 4-6 h; wherein the Mg / Al molar ratio is 2:1-3:1, and the mass ratio of magnesium-aluminum layered double hydroxide to aminosilane coupling agent is 92-85%:8-15%.

[0012] In one embodiment of this disclosure, the glass fiber is alkali-free glass fiber with a fiber length of 3-6 mm and a fiber diameter of 10-14 micrometers.

[0013] In one embodiment of this disclosure, the curing agent is hexamethylenetetramine, and its content is 14-18% of the mass of cashew nut shell oil modified phenolic resin.

[0014] In one embodiment of this disclosure, the composition further includes 0.5-1.5 parts of a release agent, which is a mixture of calcium stearate and polyethylene wax in a mass ratio of 1:(1-2).

[0015] According to a second aspect of this disclosure, a method for preparing the flame-retardant phenolic resin molding compound composition is also provided, comprising the following steps: S1. Add cashew shell oil-modified phenolic resin to a kneader, heat to 70-90℃, add aluminum diethylphosphonate, ammonium polyphosphate and melamine cyanurate, and knead for 15-25 minutes. S2. Add organosilicon-modified magnesium-aluminum layered double hydroxide and release agent, and continue kneading for 10-15 minutes; S3. Add glass fiber and knead at 50-70℃ for 20-30 minutes to ensure uniform fiber impregnation. S4. Add curing agent, knead quickly for 5-10 minutes, and discharge and cool to room temperature; S5. The mixture is plasticized and extruded through a twin-screw extruder. The sections from the feed port to the die head are sequentially divided into a feeding section, a plasticizing section, a metering section, and a die head section. The temperature of each section of the barrel from the feed port to the die head section is 90-95℃→100-110℃→110-120℃→100-115℃, the screw length-to-diameter ratio is 28-35:1, the material residence time in the barrel is 45-90 seconds, the screw speed is 30-60 rpm, and the mixture is pelletized or crushed to obtain the flame-retardant phenolic resin molding compound composition.

[0016] In one embodiment of this disclosure, the length-to-diameter ratio of the twin-screw extruder in step S5 is 28-35:1, and the die temperature is 100-115°C.

[0017] The flame-retardant phenolic resin molding compound composition disclosed herein comprises, by mass fraction, 35-50 parts of cashew nutshell oil-modified phenolic resin; 8-15 parts of aluminum diethylphosphinate; 5-10 parts of ammonium polyphosphate; 3-6 parts of melamine cyanurate; 25-40 parts of glass fiber; 2-5 parts of organosilicon-modified magnesium aluminum layered double hydroxide; and 5-8 parts of curing agent. The cashew nutshell oil toughening and glass fiber reinforcement synergistically achieve high toughness and high strength. The long-chain aliphatic side groups of the cashew nutshell oil-modified phenolic resin provide internal toughening, while the glass fiber provides skeletal reinforcement. Together, they achieve a flexural strength of 350-410 MPa and an impact strength of 38-48 kJ / m², simultaneously meeting the high strength and high toughness requirements of aerospace interior parts. Aluminum diethylphosphinate, ammonium polyphosphate, melamine cyanurate, and organosilicon-modified magnesium aluminum layered double hydroxide constitute an NP-Si ternary synergistic flame-retardant system. Through the synergistic design of nitrogen-based (MCA+APP) gas-phase flame retardancy, phosphorus-based (AlPi+APP) condensed-phase char formation, and silicon-based (organosilicon-modified LDH) high-temperature ceramic barrier, the molding compound of this invention achieves a limiting oxygen index of 35.1-38.2%, a UL94 flame retardancy rating of V-0 (1.6 mm), and a smoke density Ds(max) of only 95-145, far below the upper limit of Ds(max) less than or equal to 200 specified in FAR 25.853. Furthermore, it is completely free of halogens and heavy metals, meeting the environmental regulations of REACH and FAA.

[0018] Other features and advantages of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the present disclosure and, together with their description, serve to explain the principles of the present disclosure.

[0020] Figure 1 This is a schematic diagram of the NP-Si ternary synergistic flame retardant mechanism provided by the present invention; Figure 2 The graphs show a comparison of the heat release rate (HRR) curves of the cone calorimeter for Examples 1-3 and Comparative Examples 1-15, where (a) is Examples 1-3 and Comparative Examples 1-7, and (b) is Examples 1-3 and Comparative Examples 8-15. Figure 3 Comparison chart of mechanical properties (flexural strength and impact strength) of Examples 1-3 and Comparative Examples 1-15; Figure 4 Comparison chart of flame retardant and smoke suppression performance (LOI and smoke density Ds(max)) of Examples 1-3 and Comparative Examples 1-15; Figure 5 The ¹H-NMR spectrum provided for the resin prepared in Example 1 of this disclosure; Figure 6 This is a schematic diagram of the structure of organosilicon-modified LDH prepared in Example 3 of this disclosure. Detailed Implementation

[0021] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with specific embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of this application.

[0022] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an unspecified range.

[0023] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0024] The foregoing description of this invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are merely representative and should not be construed as exhaustive.

[0025] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0026] This invention provides a flame-retardant phenolic resin molding compound composition, comprising, by weight parts: 35-50 parts cashew nut shell oil modified phenolic resin, 8-15 parts aluminum diethylphosphinate, 5-10 parts ammonium polyphosphate, 3-6 parts melamine cyanurate, 25-40 parts glass fiber, 2-5 parts organosilicon modified magnesium aluminum layered double hydroxide, and 5-8 parts curing agent.

[0027] Cashew nut shell oil-modified phenolic resin is produced by the condensation polymerization of phenol, cashew nut shell oil, and formaldehyde under an alkaline catalyst (ammonia or sodium hydroxide). The mass substitution rate of cashew nut shell oil for phenol is 20-35%. Cashew nut shell oil is a natural and renewable resource, mainly composed of C15-C27 polyphenols. Its molecular structure contains both phenolic rings and C15 long-chain unsaturated aliphatic side groups. The phenolic ring can participate in the phenolic condensation reaction to form a cross-linked network, providing heat resistance and flame retardancy. The long-chain aliphatic side groups act as internal toughening agents in the cross-linked network, absorbing impact energy through the compliant deformation of the molecular chains, thereby increasing the impact strength of the resin from approximately 20 kJ / m² of ordinary phenolic resin to 38-48 kJ / m².

[0028] This invention strictly controls the cashew shell oil substitution rate within a preferred window of 20-35%: when the substitution rate is below 20%, the toughening effect is not obvious, and the impact strength is difficult to exceed 35 kJ / m²; when the substitution rate is above 35%, the crosslinking density is excessively reduced, the Tg drops below 120℃, and the LOI drops below 30%, which cannot meet the requirements of FAR 25.853.

[0029] Among them, aluminum diethylphosphonate (AlPi) is a representative variety of organic phosphonate flame retardants, with an average particle size of 10-50 micrometers. The phosphorus element in AlPi exists in the form of PC bonds, exhibiting much higher thermal stability than inorganic phosphates (decomposition temperature greater than or equal to 350℃). During combustion, it primarily plays a flame-retardant role in the condensed phase: AlPi decomposes upon heating to generate phosphoric acid and metaphosphoric acid, catalyzing the dehydration and carbonization of the phenolic resin matrix to form a dense graphitized carbon layer. This carbon layer possesses excellent heat insulation and oxygen barrier properties, effectively preventing the transfer of heat and oxygen into the substrate. Simultaneously, the alumina (Al2O3) particles produced by the decomposition of AlPi are embedded in the carbon layer, improving its mechanical strength and thermal stability, making it less prone to cracking and detachment under high-temperature airflow.

[0030] In this invention, the amount of AlPi used is 8-15 parts. This range of usage has been optimized: when the amount is less than 8 parts, the catalytic effect of condensed phase carbonization is insufficient and the carbon layer is not dense enough; when the amount is more than 15 parts, AlPi is prone to agglomeration and uneven dispersion in the resin matrix, and excessive AlPi will reduce the crosslinking density of the resin, leading to deterioration of mechanical properties.

[0031] Ammonium polyphosphate (APP) is a type II ammonium polyphosphate with a degree of polymerization greater than 1000 and a solubility of less than 0.5 g / 100 mL water. During combustion, APP primarily functions as a flame retardant in the gas phase: upon heating, APP decomposes to release ammonia and water vapor, diluting the concentration of combustible gases; simultaneously, it decomposes to produce phosphoric acid and polyphosphoric acid, which synergistically catalyze char formation with the decomposition products of AlPi. More importantly, the NH3 and H2O produced by APP decomposition can form a synergistic gas-phase flame retardant effect with the nitrogen-containing gas produced by the decomposition of melamine cyanurate, significantly improving the gas-phase flame retardant efficiency and increasing the LOI from approximately 30% (containing only AlPi) to over 35%. This invention uses type II APP instead of type I because type II APP has a higher degree of polymerization, better thermal stability (decomposition temperature greater than or equal to 275℃), lower solubility, and is less prone to hydrolysis and migration in the humid heat processing environment of phenolic resins, exhibiting excellent long-term flame retardant stability.

[0032] Melamine cyanurate (MCA) is one of the components of the gas-phase flame retardant system of this invention. During combustion, MCA undergoes the following decomposition process: firstly, it decomposes at approximately 350°C to produce melamine and cyanuric acid. Melamine further decomposes to release large amounts of nitrogen (N2), ammonia (NH3), and carbon monoxide (CO). These non-combustible gases rapidly dilute the oxygen concentration and lower the temperature of the combustion zone. Cyanuric acid, in turn, synergistically promotes char formation with the decomposition products of AlPi and APP. A significant nitrogen-phosphorus synergistic effect exists between MCA and APP: the phosphate ions provided by APP and the melamine cations provided by MCA form a melamine phosphate intermediate. This intermediate exhibits higher char-forming catalytic activity than APP or MCA alone, initiating the char reaction at a lower temperature, resulting in earlier and more dense and complete char layers.

[0033] The dosage of MCA is 3-6 parts, which, together with the dosage of AlPi, forms an optimized P / N molar ratio (approximately 1:0.8-1.2). Within this ratio range, the synergistic efficiency of gas-phase flame retardancy and condensed-phase flame retardancy is the highest.

[0034] Layered magnesium aluminum hydroxide (LDH) is a type of layered bimetallic hydroxide with natural flame-retardant and smoke-suppressing properties: when LDH decomposes thermally, it absorbs a large amount of heat (endothermic effect), while releasing water vapor and CO2 to dilute combustible gases, and the residual MgO and Al2O3 form a ceramic protective layer. This invention modifies the surface of LDH with an aminosilane coupling agent using organosilicon, inserting silane molecules into the interlayer spaces, increasing the interlayer spacing from the natural approximately 0.78 nm to 1.5-3.0 nm. The increased interlayer spacing significantly improves the dispersibility of LDH in a phenolic resin matrix, and the silane groups form chemical bonds with the resin matrix, enhancing interfacial bonding. Organosilicon-modified LDH forms a continuous Si-O-Si ceramicized barrier layer in the later stages of combustion (≥500℃). This barrier layer covers the surface of the char layer and has the following unique functions: First, the Si-O-Si bond energy is extremely high (approximately 452 kJ / mol), with thermal stability far exceeding that of CC and CN bonds, maintaining structural integrity at extremely high temperatures; second, the oxygen permeability of the Si-O-Si layer is extremely low, effectively blocking the diffusion channels of oxygen to the lower char layer; third, the surface of the Si-O-Si layer is smooth and dense, reducing the release of smoke particles and significantly lowering smoke density. The introduction of organosilicon-modified LDH enables this invention to form a complete NP-Si ternary synergistic flame retardant system: nitrogen-based (MCA+APP) dominates gas-phase flame retardancy, phosphorus-based (AlPi+APP) dominates condensed-phase char formation, and silicon-based (organosilicon-modified LDH) dominates high-temperature ceramicized barrier. The synergy of these three components maximizes flame retardant efficiency.

[0035] The preparation method of organosilicon-modified magnesium-aluminum layered double hydroxide is as follows: magnesium-aluminum layered double hydroxide (Mg / Al molar ratio 2:1-3:1, original interlayer spacing about 0.78 nm) is dispersed in an ethanol / water mixed solvent (ethanol to water volume ratio 4:1-6:1, LDH solid content 5-10%), and an aminosilane coupling agent (γ-aminopropyltriethoxysilane, KH-550) is added. The amount of aminosilane is 8-15% of the mass of LDH. The reaction is refluxed at 70-80℃ for 4-6 hours. During the reaction, the amino groups of aminosilane form hydrogen bonds with the hydroxyl groups on the LDH layers, and at the same time, the silanol groups undergo a condensation reaction with the interlayer hydroxyl groups of LDH to achieve chemical grafting. After the reaction, the mixture is filtered, washed three times with ethanol to remove unreacted silane coupling agent, vacuum dried at 60-80℃ for 12-24 hours, and ground to obtain organosilicon-modified magnesium-aluminum layered double hydroxide. After the above treatment, the interlayer spacing of LDH increased from 0.78 nm to 1.5-3.0 nm, the organosilicon grafting rate was 5-12%, and the silane segments formed steric hindrance in the interlayer, effectively preventing the aggregation of LDH under high temperature and high shear molding conditions. At the same time, the grafted amino groups can form hydrogen bonds with the phenolic hydroxyl groups of phenolic resin, enhancing the interfacial bonding force between LDH and the resin matrix.

[0036] The glass fiber is alkali-free, with a fiber length of 3-6 mm and a diameter of 10-14 micrometers, and is surface-treated with a silane coupling agent. The glass fiber acts as a reinforcing skeleton in the molding compound, achieving a flexural strength of 350-410 MPa, while also improving dimensional stability and resistance to heat deformation.

[0037] Cashew nut shell oil-modified phenolic resin serves as the continuous matrix phase, undertaking the main functions of molding, load-bearing, heat resistance, and toughening. Its content must ensure sufficient wetting and bonding of the filler phase—35-50 parts resin combined with 25-40 parts glass fiber, with a resin / glass fiber mass ratio of approximately 1.0-1.5, represents the minimum resin level required to guarantee molding flowability (spiral flow length ≥200 mm) and flexural strength (≥350 MPa). The flame-retardant system is a functionally dispersed phase, designed to "achieve flame-retardant targets with the lowest effective total amount": the NP-Si ternary system, through the synergistic effect of the gas phase (MCA + APP), condensed phase (AlPi + APP), and ceramic barrier (organosilicon LDH), achieves a flame-retardant efficiency far exceeding that of a single flame retardant. A total amount of 16-31 parts is sufficient to achieve an LOI ≥35% and UL94 V-0 rating. Further increasing the flame retardant content leads to saturation of flame-retardant performance, dilutes the resin matrix, reduces crosslinking density and fiber wettability, resulting in deterioration of flexural and impact strength.

[0038] The curing agent is hexamethylenetetramine (urotropine), with a content of 14-18% of the mass of cashew nut shell oil modified phenolic resin. It decomposes at the molding temperature (160-180℃) to release formaldehyde, which reacts with the active phenolic hydroxyl groups in the resin to form a cross-linked network.

[0039] The composition also includes 0.5-1.5 parts of a release agent. The release agent is a mixture of calcium stearate and polyethylene wax in a mass ratio of 1:(1-2), which provides good release properties during compression molding while improving the flowability and surface finish of the molding compound.

[0040] The release agent, a blend of calcium stearate and polyethylene wax, migrates to the molding compound-mold interface during molding, reducing interfacial adhesion and ensuring smooth demolding with a clean, scratch-free product surface. Simultaneously, the polyethylene wax provides external lubrication, improving melt flowability and increasing the spiral flow length by approximately 10-15 mm. Demolding is poor when the release agent dosage is below 0.5 parts, while dosage above 1.5 parts easily leads to blooming on the product surface, negatively impacting mechanical properties.

[0041] The present invention also provides a method for preparing the above-mentioned flame-retardant phenolic resin molding compound composition, comprising the following steps: S1. Add cashew nut shell oil-modified phenolic resin to a kneader, heat to 70-90℃, add aluminum diethylphosphonate, ammonium polyphosphate, and melamine cyanurate, and knead for 15-25 minutes. Specifically, add cashew nut shell oil-modified phenolic resin to a kneader (double-paddle kneader, 100 L volume), turn on the jacketed steam heating system to heat to 80±2℃, and simultaneously start the kneading paddles to rotate at low speed (drive paddle n1=30 rpm, driven paddle n2=15 rpm) to preheat and soften the resin. After reaching the set temperature, add aluminum diethylphosphonate, ammonium polyphosphate, and melamine cyanurate, maintaining the kneading paddle speeds n1=30 rpm and n2=15 rpm, and knead for 20 minutes. During the kneading process, maintain the material temperature at 80±2℃ through the jacketed temperature control system to ensure that the flame retardant powder is uniformly dispersed in the molten resin matrix.

[0042] S2. Add organosilicon-modified magnesium-aluminum layered double hydroxide and release agent, and continue kneading for 10-15 minutes; S3. Add glass fiber and knead at 50-70℃ for 20-30 minutes to ensure uniform fiber impregnation. Kneading refers to a conventional speed dual-paddle mixing operation, with the active paddle speed n1=30 rpm and the driven paddle speed n2=15 rpm. The purpose is to ensure uniform mixing of the components, and it is suitable for the conventional mixing stage of steps S1-S3. Rapid kneading refers to a mixing operation with increased speed, with the active paddle speed increased to n1=45 rpm and the driven paddle speed n2=22 rpm. At the same time, the jacket cooling water system is turned on. The purpose is to complete the final addition and uniform dispersion of the curing agent in the shortest possible time. Meanwhile, the material temperature is controlled to not exceed 55℃ through forced cooling to prevent hexamethylenetetramine from decomposing prematurely above 60℃ and releasing formaldehyde, which would lead to pre-curing.

[0043] S4. Add curing agent (urotropine), and knead rapidly for 5-10 minutes under the cooling and temperature control conditions of the kneader jacket (material temperature not exceeding 55℃). Discharge and cool to room temperature. The temperature control measures prevent urotropine from decomposing prematurely and releasing formaldehyde above 60℃. S5. The mixture is plasticized and extruded through a twin-screw extruder. The sections from the feed port to the die head are sequentially divided into a feeding section, a plasticizing section, a metering section, and a die head section. The temperature of each section of the barrel from the feed port to the die head section is 90-95℃→100-110℃→110-120℃→100-115℃, the screw length-to-diameter ratio is 28-35:1, the material residence time in the barrel is 45-90 seconds, the screw speed is 30-60 rpm, and the mixture is pelletized or crushed to obtain the flame-retardant phenolic resin molding compound composition.

[0044] In step S5, the feeding section operates at 90-95℃ to soften and melt the resin without initiating solidification; the plasticizing section operates at 100-110℃ to complete the dispersion, mixing, and initial plasticization of the components; the metering section operates at 110-120℃ to provide sufficient plasticization and homogenization time for the material, ensuring a uniform and dense extrudate; the die section temperature is adjusted back to 100-115℃ to prevent pre-curing caused by the decomposition of hexamethylenetetramine at the die opening due to excessively high temperatures (hexamethylenetetramine decomposes more rapidly above 120℃), thus avoiding material accumulation and scorched particles at the die opening. If the metering section temperature is below 110℃, plasticization is insufficient, resulting in a rough extrudate surface; if it is above 120℃, the risk of pre-curing increases significantly, screw torque increases, and even strip breakage may occur.

[0045] Unless otherwise specified, percentage content and percentage concentration in this invention refer to mass percentage content and mass percentage concentration. Unless otherwise specified, all raw materials are commercially available.

[0046] Experimental materials Cashew nut shell oil: Cardlä Chemical (Zhuhai) Co., Ltd., industrial grade, phenolic hydroxyl content approximately 2.8 mmol / g; Aluminum diethylphosphonate (AlPi): Exolit OP 1230, Clariant Chemicals (China) Co., Ltd., average particle size 10-50 μm, phosphorus content 23.5-24.5 wt%; Ammonium polyphosphate type II: Exolit AP 422, Clariant Chemicals, degree of polymerization >1000, solubility <0.5 g / 100 mL water (25℃), particle size <50 μm; Melamine cyanurate: MCA-98 (powder, particle size 15 μm), Liaocheng Jinshilian Chemical Co., Ltd., particle size 5-30 μm, nitrogen content approximately 40 wt%; Magnesium aluminum layered double hydroxide: Pural MG 63HT, Sasol GmbH, Germany, Mg / Al molar ratio 3:1; γ-aminopropyltriethoxysilane (KH-550): Nanjing Shuguang Fine Chemical Co., Ltd., purity ≥99%; Organosilicon-modified LDH: LDH prepared according to the preparation examples, interlayer spacing 1.5-3.0 nm, grafting rate 5-12%; Alkali-free glass fiber: Taishan Glass Fiber Co., Ltd., ECR14-4.5-608A, length 3-6 mm, diameter 10-14 μm, surface treated with silane coupling agent; Hexamethylenetetramine: Shandong Xima Supply Chain Management Co., Ltd., purity ≥99%, 14-18% of phenolic resin mass; Calcium stearate: Shandong Xima, industrial grade; Polyethylene wax, Honeywell. AC-6A; Common thermoplastic phenolic resin: Jinan Shengquan Group Co., Ltd., PF-4012, number average molecular weight approximately 900, softening point 110℃; Decabromodiphenyl ether (DBDPE): Shandong Haiwang Chemical Co., Ltd., industrial grade, bromine content ≥82%; Antimony trioxide (Sb2O3): Xikuangshan Shanxing Antimony Industry Co., Ltd., purity ≥99.5%, average particle size 1-3 μm; Phosphoric anhydride: Polyphosphoric acid, Hubei Xingfa Chemical Group Co., Ltd., industrial grade; Acrylic ester nanoparticles: Core-shell structured emulsion, solid content 30%, average particle size 80 μm. nm, Foshan Nanhai Datian Chemical Co., Ltd.; Talc powder: 1250 mesh, Liaoning Haicheng Jinghua Minerals Co., Ltd.; Calcium carbonate: heavy, 800 mesh, Guangxi Hezhou Kelong Powder Co., Ltd.; Wood flour: poplar wood flour, 80-120 mesh, Shandong Linyi Lulin Wood Industry Co., Ltd.; Phenol: China Petroleum Yanshan Petrochemical Company, industrial grade; Formaldehyde aqueous solution: 37%, Shandong Lianmeng Chemical Group Co., Ltd.; Ammonia water: 25%, Xilong Scientific Co., Ltd., analytical grade; Sodium hydroxide: Xinjiang Zhongtai Chemical Co., Ltd., industrial grade.

[0047] Experimental equipment Kneader: NH-100, Foshan Nanhai Jinchangtai Machinery Equipment Co., Ltd., 100 L capacity, twin-paddle kneading, adjustable speed 0-50 rpm; Twin-screw extruder: SHJ-35, Nanjing Keya Chemical Equipment Co., Ltd., screw diameter 35 mm, L / D ratio 28-35:1, co-rotating; Oxygen index analyzer: JF-3, Nanjing Jiangning District Analytical Instrument Factory; Cone calorimeter: FTT iCone Plus, Fire Testing Technology, UK; Smoke density chamber: JCY-2, Nanjing Jiangning District Analytical Instrument Factory; Universal testing machine: CMT-4304, Shenzhen Sansi Testing Technology Co., Ltd.; Simply supported beam impact testing machine: XJJ-50, Chengde Testing Machine Factory; GPC instrument: Waters 1525 / 2414, Waters Corporation, USA.

[0048] Example 1 42.0 g of cashew nut shell oil-modified phenolic resin (cashew nut shell oil with a phenol substitution rate of 25%, a number-average molecular weight of 950, a softening point of 92℃, determined by GPC) was added to a kneader (model NH-100, Foshan Nanhai Jinchangtai Machinery Equipment Co., Ltd., volume 100 L, kneading paddle speed n1=30 rpm, n2=15 rpm) and heated to 80±2℃. Add 12.0 g of aluminum diethylphosphinate (Exolit OP 1230, Clariant Chemicals, average particle size 25 μm), 8.0 g of ammonium type II polyphosphate (Exolit AP 422, Clariant Chemicals, degree of polymerization 1500, solubility <0.5 g / 100 mL water), and 5.0 g of melamine cyanurate (MCA-98 (powder, particle size 15 μm), Liaocheng Jinshilian Chemical Co., Ltd., particle size 15 μm), and knead for 20 minutes (kneading paddle speed n1=30 rpm, n2=15 rpm, jacketed steam heating).

[0049] Add 3.5 g of organosilicon-modified magnesium-aluminum layered double hydroxide (prepared according to preparation example LDH-1, interlayer spacing 2.2 nm, grafting rate 8.1%, determined by XRD / TGA) and release agent (calcium stearate, Shandong Xima, industrial grade, 0.5 g; polyethylene wax, Honeywell AC-6A, 0.8 g), and continue kneading for 12 minutes. Add 32.0 g of alkali-free glass fiber (Taishan Glass Fiber Co., Ltd., ECR14-4.5-608A, fiber length 4.5 mm, diameter 12 μm, surface treated with γ-glycidoxypropyltrimethoxysilane), and knead for 25 minutes at 60±2℃. Add 6.7 g of hexamethylenetetramine (urotropine, Shandong Xima, purity ≥99%) (16% of the phenolic resin mass), knead rapidly for 8 minutes (rapid kneading is defined as: increasing the kneading paddle speed to n1=45 rpm and n2=22 rpm, while turning on the jacket cooling water to control the material temperature not to exceed 55℃ to prevent premature decomposition of urotropine), and discharge and cool to room temperature.

[0050] The mixture was plasticized and extruded through a twin-screw extruder (model SHJ-35, Nanjing Keya Chemical Equipment Co., Ltd., screw diameter 35mm, length-to-diameter ratio 30:1). The barrel temperature settings were: feeding section 90±2℃, plasticizing section 100±2℃, metering section 110±2℃, die section 105±2℃, screw speed 45 rpm. The mixture was then pelletized to obtain a flame-retardant phenolic resin molding compound.

[0051] The following methods were used to determine various data of the flame-retardant phenolic resin molding compound composition.

[0052] (1) Limiting Oxygen Index (LOI): Tested using an oxygen index analyzer according to GB / T 2406.2-2009. The sample size is 80mm × 10mm × 4mm. It is ignited in a mixed gas flow of oxygen and nitrogen. The oxygen volume fraction is adjusted so that the sample can just maintain flaming combustion for 3 minutes or the combustion length is 50mm. The oxygen volume fraction at this time is the LOI. Calculation formula: LOI (%) = [O2 flow rate / (O2 flow rate + N2 flow rate)] × 100%.

[0053] (2) Smoke density Ds(max): Tested according to GB / T 8627-2007 using the smoke density chamber method. The sample size is 25 mm × 25 mm × 6 mm. It is burned with flame under a thermal radiation flux of 25 kW / m². The transmittance of the smoke chamber as a function of time is measured by a photometer. Ds(max) is the maximum specific optical density. Calculation formula: Ds(max) = (V / L × A) × ln(100 / Tt), where V is the volume of the smoke chamber (m³), L is the optical path (m), A is the exposed area of ​​the sample (m²), and Tt is the minimum transmittance (%).

[0054] (3) Glass transition temperature (Tg): Tested according to ASTM D7028 using dynamic mechanical analysis (DMA). The sample size was 60 mm × 10 mm × 4 mm, three-point bending mode, frequency 1 Hz, heating rate 3℃ / min, from room temperature to 250℃, and the temperature corresponding to the peak value of tanδ was taken as Tg.

[0055] (4) Impact strength: Tested according to GB / T 1843-2008 (notched impact of simply supported beam). The sample size is 80 mm × 10 mm × 4 mm, the V-notch depth is 2 mm, the pendulum energy is 4 J, the test temperature is 23±2℃, and 5 samples are tested for each sample and the average value is taken.

[0056] (5) Spiral flow length: Tested according to GB / T 5471-2008. An Archimedes spiral groove mold (groove cross-section 8mm×4mm) was used, with a mold temperature of 170±2℃, a molding pressure of 15±1 MPa, and a holding time of 60 s. The maximum distance the molten molding compound traveled along the spiral groove from the central injection port was measured. Among them, 170±2℃ is the molding mold temperature.

[0057] Example 2 Add 38 parts of cashew nut shell oil-modified phenolic resin (cashew nut shell oil phenol substitution rate 25%, number average molecular weight 1000, softening point 88℃) to a kneader and heat to 75℃. Add 14 parts of aluminum diethylphosphinate (average particle size 20 μm), 10 parts of ammonium type II polyphosphate (degree of polymerization 1800), and 6 parts of melamine cyanurate (particle size 10 μm), and knead for 22 minutes. Add 4.5 parts of organosilicon-modified magnesium aluminum layered double hydroxide (interlayer spacing 2.8 nm, grafting rate 10%) and a release agent (0.6 parts of calcium stearate and 0.6 parts of polyethylene wax), and knead for 15 minutes. Add 38 parts of alkali-free glass fiber (fiber length 5 mm, diameter 11 μm), and knead at 55℃ for 30 minutes. Add 6.1 parts of hexamethylenetetramine (content 16%), and knead rapidly for 10 minutes. The twin-screw extruder barrel temperature settings were: feeding section 90°C, plasticizing section 100°C, metering section 112°C, and die section 105°C; screw speed was 40 rpm. Pelletizing yielded the molding compound composition of Example 2. The molding compound composition of Example 2 was tested using the method described in Example 1.

[0058] Since the filler content in Example 2 is relatively high, using a medium-high extrusion temperature is beneficial to ensure plasticization quality. The temperature here is 170°C, which is the temperature of the compression molding die. Fine-tuning the extrusion temperature within the above window has no sensitive impact on the performance of the sample.

[0059] Here, those skilled in the art can select the appropriate number of experimental materials for the experiment according to actual needs, and this disclosure does not limit the specific weight. The same applies below, so it will not be repeated.

[0060] Example 3 Add 48 parts of cashew nut shell oil-modified phenolic resin (cashew nut shell oil phenol substitution rate 35%, number average molecular weight 1400, softening point 105℃) to a kneader and heat to 85℃. Add 10 parts of aluminum diethylphosphinic acid (average particle size 35 μm), 6 parts of ammonium type II polyphosphate (degree of polymerization 1200), and 4 parts of melamine cyanurate (particle size 20 μm), and knead for 18 minutes. Add 2.5 parts of organosilicon-modified magnesium aluminum layered double hydroxide (interlayer spacing 1.8 nm, grafting rate 6%) and a release agent (0.4 parts of calcium stearate and 0.5 parts of polyethylene wax), and knead for 10 minutes. Add 28 parts of alkali-free glass fiber (fiber length 3.5 mm, diameter 13 μm), and knead at 65℃ for 22 minutes. Add 7.2 parts of hexamethylenetetramine (content 15%), and knead rapidly for 6 minutes. The twin-screw extruder barrel temperature settings were: feeding section 95°C, plasticizing section 105°C, metering section 115°C, and die section 108°C; screw speed was 50 rpm. Pelletizing yielded the molding compound composition of Example 3. The molding compound composition of Example 3 was tested using the method described in Example 1.

[0061] Preparation Example 1 (Preparation method of cashew nut shell oil modified phenolic resin, substitution rate 25%) 1. Experimental Methods 112.5 g (1.20 mol) of phenol and 37.5 g of cashew nut shell oil (containing approximately 0.11 mol of phenolic hydroxyl groups) were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was heated to 70-80°C and stirred until homogeneous. 169 g of formaldehyde aqueous solution (37% formaldehyde mass fraction) (containing 2.08 mol of formaldehyde, F / P (formaldehyde / total phenol) molar ratio = 1.6) and 5 mL of ammonia (25% concentration) were added as catalysts, and the mixture was heated to 85-90°C and reacted for 2 hours. Then, the mixture was heated to 95-100°C for dehydration and polycondensation for 1.5 hours, followed by vacuum dehydration (vacuum degree -0.09 MPa, temperature 110°C) until the moisture content was <2%, yielding a reddish-brown transparent resin.

[0062] Gel permeation chromatography (GPC) sample preparation: Weigh about 10 mg of the above reddish-brown transparent resin, add 5 mL of tetrahydrofuran (chromatographic grade), stir and dissolve at room temperature for 2 hours, filter through a 0.45 μm organic phase filter membrane to obtain a sample solution with a concentration of about 2 mg / mL, and inject 20 μL.

[0063] Softening point determination (ring and ball method, GB / T 8146): Melt the resin sample by heating and pour it into a brass ring (inner diameter 15.7 mm, height 6.35 mm), level it, and allow it to cool. Place the copper ring on the softening point tester stand, and place a steel ball with a diameter of 9.53 mm and a mass of 3.5 g on top. Immerse the ball in a glycerol bath (or a water bath if the softening point is expected to be below 80℃). Increase the temperature at a rate of 5℃ / min. Record the temperature at which the resin encapsulated by the steel ball falls to the bottom plate (25.4 mm from the lower surface of the copper ring). This temperature is the softening point. Perform two parallel determinations and take the average value. The difference between the two values ​​should not exceed 1℃.

[0064] Hydroxyl value determination (refer to GB / T 12008.3, acetic anhydride-pyridine method): Weigh approximately 1 g of resin sample (accurate to 0.0001 g) into a ground-glass conical flask, add 10 mL of acetic anhydride-pyridine acylation solution (volume ratio 1:10), and reflux in a water bath at 98±2℃ for 1 hour; after cooling, add 10 mL of distilled water to hydrolyze the remaining acetic anhydride, using phenolphthalein as an indicator, and titrate with 0.5 mol / L potassium hydroxide-ethanol standard solution until a faint red color remains for 30 s. Perform a blank test simultaneously. Hydroxyl value (mg KOH / g) = (V0–V1)×c×56.1 / m, where V0 and V1 are the volumes of standard solution consumed (mL) for the blank and sample, respectively, c is the concentration of the standard solution (mol / L), and m is the sample mass (g).

[0065] Approximately 15 mg of resin sample was dissolved in 0.6 mL of DMSO-d6. TMS was used as an internal standard, and ¹H-NMR spectra were acquired using a 400 MHz nuclear magnetic resonance spectrometer.

[0066] The specific chemical reaction processes involved include: (1) Addition reaction: Phenol (and the phenolic ring in cashew nut shell oil) undergoes hydroxymethylation addition with formaldehyde under the action of an alkaline catalyst to generate ortho / para-hydroxymethylphenol: C6H5OH + CH2O → HOC6H4CH2OH (hydroxymethylphenol) (2) Condensation reaction: Dehydration condensation between hydroxymethylphenols and between hydroxymethylphenols and phenolic rings forms methylene (–CH2–)-bridged phenolic oligomers: n HOC6H4CH2OH → [–C6H3(OH)–CH2–] n + (n–1) H2O The phenolic ring in cashew nut shell oil molecules participates in the above addition and condensation reactions in the same way. Its C15 unsaturated long chain side groups do not participate in the condensation reaction and remain in the cross-linked network to play an internal toughening role.

[0067] 2. Experimental Results The sample was analyzed by gel permeation chromatography with tetrahydrofuran as the mobile phase and polystyrene as the standard. The number-average molecular weight (Mn) was 950, the softening point was 92℃ (ring and ball method, GB / T 8146), and the hydroxyl value was 285 mg KOH / g. The mass substitution rate of cashew nut shell oil for phenol was 37.5 / (112.5 + 37.5) = 25%.

[0068] The mass substitution rate of cashew nut shell oil for phenol is defined as the ratio of the mass of cashew nut shell oil to (mass of phenol + mass of cashew nut shell oil) during the preparation of cashew nut shell oil-modified phenolic resin, expressed as a percentage. The calculation formula is: Substitution rate (%) = Mass of cashew nut shell oil / (mass of phenol + mass of cashew nut shell oil) × 100%.

[0069] Substitution rate control method: The substitution rate is controlled by the feeding ratio. Taking preparation example 1 as an example: (1) The target substitution rate is determined to be 25%, that is, the mass of cashew shell oil accounts for 25% of the total mass of phenol and cashew shell oil. Based on this, the feeding mass ratio is determined to be phenol: cashew shell oil = 75:25 (mass ratio); (2) 112.5 g of phenol and 37.5 g of cashew shell oil are weighed according to the feeding ratio; (3) The phenolic hydroxyl content of cashew shell oil is about 2.8 mmol / g according to the hydroxyl value determination method. The total number of phenol moles provided by the two raw materials is calculated (in this example, it is 112.5 / 94 + 37.5 × 2.8 / 1000 ≈ 1.20 + 0.11 = 1.31 mol); (4) The amount of 37% formaldehyde aqueous solution is calculated according to the F / P molar ratio of 1.4-1.8 (1.6 in this example) (1.31 × 1.6 × 30 / 0.37 ≈ 169). g); (5) Polycondensation reaction was carried out at 85-100℃ under the action of alkaline catalyst (ammonia or sodium hydroxide), and the cashew shell oil modified phenolic resin with the target substitution rate was obtained after vacuum dehydration; (6) The actual substitution rate was verified and determined by ¹H-NMR or FTIR (the test method is described below).

[0070] In summary, by controlling the mass ratio of phenol to cashew nut shell oil within the range of 80:20 to 65:35, cashew nut shell oil-modified phenolic resin with a substitution rate of 20-35% can be obtained. The mass ratio and substitution rate correspond one-to-one numerically, and the actual substitution rate is based on the ¹H-NMR test value.

[0071] like Figure 5As shown in the spectrum: δ6.5-7.5 ppm represents the aromatic proton signal of the phenolic ring (integrated area A(Ar) = 12.40), and δ4.9-5.5 ppm represents the –CH=CH– olefin proton signal on the C15 side chain of cashew nutshell oil (integrated area A(vi) = 1.00). Both the phenolic unit and the cashew nutshell oil unit have 5 protons in the phenolic ring, and the average number of protons in the C15 side chain of cashew nutshell oil is 2. Assuming the molar ratio of phenolic units to cashew nutshell oil units is n(P):n(C), then A(Ar) / A(vi) = 5(n(P) + n(C)) / 2n(C). Substituting the measured integral ratio of 12.40, we obtain n(P):n(C) ≈ 2.92:1. Converting the mass ratio to molar mass (phenol 94 g / mol, cashew nut shell oil approximately 300 g / mol), the ratio is approximately 75.6:24.4, meaning the measured substitution rate is approximately 24.4%. This deviation from the designed feed rate of 25% is within ±1%, proving the accuracy and reliability of the feed control method. FTIR semi-quantitative verification: Comparison of 3010 cm⁻¹... - ¹(=CH)and 3400 cm - The relative intensity of the (phenolic hydroxyl) absorption peak is consistent with that of ¹H-NMR.

[0072] Substitution rate test method: ¹H-NMR (400 MHz, DMSO-d6) was used to determine the substitution rate of phenol by comparing the integrated area ratio of the aromatic proton signal (δ6.5-7.5 ppm) on the phenol ring with the olefin proton signal (δ4.9-5.5 ppm, -CH=CH-) on the C15 side chain. Combined with the characteristic proton assignments of phenol and cashew nut shell oil, the mass substitution rate of cashew nut shell oil for phenol was calculated. Alternatively, FTIR comparison of the characteristic absorption peak of the phenolic hydroxyl group (~3400 cm⁻¹) could be used. - ¹) with C15 side chain = CH stretching vibration (~3010 cm) - The relative intensity of ¹) was semi-quantitatively verified.

[0073] Preparation Example 2 (Preparation method of cashew nut shell oil modified phenolic resin, substitution rate 35%) 97.5 g (1.04 mol) of phenol and 52.5 g of cashew nut shell oil (containing approximately 0.15 mol of phenolic hydroxyl groups) were added to a four-necked flask equipped with a stirrer, thermometer, and condenser, and the mixture was heated to 70-80°C. 153 g of 37% formaldehyde solution (F / P = 1.6) and 2 g of sodium hydroxide (10% aqueous solution) were added as catalysts, and the mixture was heated to 80-85°C and reacted for 2.5 hours. The mixture was then heated to 95-100°C for dehydration and polycondensation for 2 hours, followed by vacuum dehydration. GPC analysis showed Mn = 1250, softening point 108°C (ring and ring method), and hydroxyl value 260 mgKOH / g. The substitution rate was 52.5 / (97.5 + 52.5) ​​= 35%.

[0074] Preparation Example 3 (LDH-1 grafting rate 8%, interlayer spacing 2.2 nm) 1. Experimental Methods 50 g of a magnesium-aluminum layered double hydroxide (Mg / Al molar ratio 3:1, initial interlayer spacing 0.78 nm, specific surface area approximately 45 m² / g) was dispersed in 500 mL of an ethanol / water mixed solvent (ethanol:water volume ratio = 5:1, LDH solid content 10%) and ultrasonically dispersed for 30 minutes. 5 g of γ-aminopropyltriethoxysilane (KH-550) (10% of the LDH mass) was added, and the mixture was refluxed at 75°C for 5 hours. During the reaction, the amino groups of the aminosilane formed hydrogen bonds with the hydroxyl groups on the LDH layers, and the silanol groups underwent condensation reactions with the interlayer hydroxyl groups to achieve chemical grafting. After the reaction, the mixture was filtered, washed three times with anhydrous ethanol to remove unreacted silane, dried under vacuum at 70°C for 18 hours, and then ground through a 200-mesh sieve.

[0075] The specific chemical processes involved include: (1) Silane hydrolysis: The ethoxy group of KH-550 hydrolyzes in ethanol / water solvent to generate silanol: H2N(CH2)3Si(OC2H5)3+ 3H2O → H2N(CH2)3Si(OH)3+ 3C2H5OH (2) Condensation grafting: The silanol groups undergo a condensation reaction with the Mg-OH / Al-OH on the surface of the LDH layer to form Si-OM (M=Mg / Al) covalent bonds: H2N(CH2)3Si(OH)3+ HO-M (lamella)→ H2N(CH2)3Si(OH)2-OM (lamella)+ H2O (3) Interlayer self-polymerization: Some silanols further condense to form a Si-O-Si network: ≡Si-OH + HO-Si≡ → ​​≡Si-O-Si≡ + H2O 2. Experimental Results XRD analysis (Cu Kα rays, scanning speed 2° / min) showed that the diffraction peak of the (003) crystal plane shifted from 2θ=11.3° to 5.0°, and the interlayer spacing was calculated to be 2.22 nm according to the Bragg equation. TGA analysis (N2 atmosphere, heating rate 10℃ / min) showed that the organosilicon grafting rate was 8.1%.

[0076] (1) X-ray diffraction (XRD): Cu Kα rays (λ=1.5406 Å) were used, with a scanning range of 2θ=2°-30° and a scanning speed of 2° / min. The (003) crystal plane diffraction peak of the unmodified LDH was located at 2θ=11.3°, corresponding to an interlayer spacing of d=0.78 nm (Bragg equation: d=λ / 2sinθ). After organosilicon modification, the (003) diffraction peak shifted to a lower angle to 2θ=5.0° (LDH-1), corresponding to an interlayer spacing of d=2.22 nm, and the interlayer spacing increased by 1.44 nm, proving that the aminosilane molecule had been successfully inserted into the LDH interlayer.

[0077] (2) Fourier transform infrared spectroscopy (FTIR): KBr pellet method was used, with a scanning range of 4000-400 cm⁻¹. - ¹. Organosilicon-modified LDH at 2920 cm⁻¹ - ¹ and 2850 cm - A new peak of CH stretching vibration appears at ¹, at 1120 cm⁻¹. - The appearance of the Si-O-Si asymmetric stretching vibration peak at position ¹ proves that the silane coupling agent has been chemically grafted onto the LDH surface.

[0078] (3) Thermogravimetric analysis (TGA): N2 atmosphere, heating rate 10℃ / min, from room temperature to 800℃. The mass loss of organosilicon-modified LDH in the 200-600℃ range was 12.5% ​​(LDH-1), while the mass loss of unmodified LDH due to interlayer water desorption was only 5.2%. The difference of 7.3% corresponds to the thermal decomposition of the organosilicon graft. Based on this, the organosilicon grafting rate was calculated to be 8.1%.

[0079] (4) Transmission electron microscopy (TEM): accelerating voltage 200 kV, the sample was ultrasonically dispersed in ethanol and dropped onto a copper grid. The organosilicon-modified LDH showed a typical layered morphology with an interlayer spacing of about 2.2 nm, consistent with the XRD results, and organosilicon grafted layers were visible at the edges of the layers (dark contrast).

[0080] refer to Figure 6 The attached figure shows the Mg-Al layer, the interlayer inserted aminosilane molecular chains, the Si-O-Si condensation network on the surface of the layer, and the enlarged interlayer spacing (1.5-3.0 nm).

[0081] Preparation Example 4 (LDH-2 grafting rate 12%, interlayer spacing 2.8 nm) Similar to Preparation Example 3, the amount of KH-550 was increased to 7.5 g (15% of the LDH mass), the reaction temperature was 80 °C, and the reaction time was 6 hours. XRD analysis showed an interlayer spacing of 2.85 nm, and TGA analysis showed a grafting rate of 12.3%.

[0082] Preparation Example 5 (LDH-3 grafting rate 5%, interlayer spacing 1.8 nm) Similar to Preparation Example 3, the amount of KH-550 was reduced to 4 g (8% of the LDH mass), the reaction temperature was 70 °C, and the reaction time was 4 hours. XRD analysis showed an interlayer spacing of 1.76 nm, and TGA analysis showed a grafting rate of 5.2%.

[0083] The three types of organosilicon-modified LDH were used in the formulation of Example 1 (with a substitution amount of 3.5 parts for each). Comparative tests showed that: when the grafting rate was 8% (LDH-1), Ds(max) was 120; when the grafting rate was 12% (LDH-2), Ds(max) decreased to 95; and when the grafting rate was 5% (LDH-3), Ds(max) increased to 145. This indicates that the increased grafting rate makes the Si-O-Si ceramic barrier more dense and complete, resulting in better smoke suppression.

[0084] Unless otherwise explicitly stated, the control group for all comparative experiments in this invention is uniformly set as Example 1, and will not be individually labeled thereafter.

[0085] Comparative Example 1 (Traditional phenolic molding compound + brominated flame retardant) 100 parts of ordinary thermoplastic phenolic resin (number average molecular weight 900, softening point 110℃) were added to a kneader and heated to 80℃. 20 parts of decabromodiphenyl ether (DBDPE) and 8 parts of antimony trioxide (Sb₂O₃) were added, and kneaded for 20 minutes. 35 parts of alkali-free glass fiber (fiber length 4.5 mm, diameter 12 micrometers) and a release agent (0.8 parts of calcium stearate) were added, and kneaded at 60℃ for 25 minutes. 7 parts of hexamethylenetetramine were added, and the mixture was rapidly kneaded for 8 minutes before being discharged. The mixture was then plasticized and pelletized using a twin-screw extruder.

[0086] This formulation represents a traditional bromine-antimony synergistic flame-retardant phenolic molding compound system. It is important to note that this comparative example uses a decabromodiphenyl ether + Sb₂O₃ system to illustrate the environmental regulatory risks of traditional bromine-antimony flame-retardant solutions (decabromodiphenyl ether has been banned under the EU REACH regulation), rather than to compare its performance with that of this invention. The halogen-free design of this invention is another technological advantage independent of flame-retardant efficiency.

[0087] Comparative Example 2 (Refer to the high-temperature resistant phenolic molding compound in CN101665613B) 100 parts of thermoplastic phenolic resin (number average molecular weight 850, softening point 105℃) were added to a kneader and heated to 80℃. 12 parts of phosphoric anhydride, 5 parts of acrylate nanoparticles (core-shell structure, average particle size 80 nm), and mineral fillers (15 parts talc and 10 parts calcium carbonate) were added, and kneaded for 20 minutes. 20 parts of wood flour were added, and kneaded at 60℃ for 25 minutes. 7.5 parts of hexamethylenetetramine were added, and the mixture was rapidly kneaded for 8 minutes before being discharged. The mixture was then plasticized and pelletized using a twin-screw extruder.

[0088] This formulation represents a phenolic molding compound system containing nano-toughening particles and phosphoric anhydride flame retardants in the prior art. The acrylate nanoparticles are produced using an emulsion pre-dispersion process: first, the nanoparticle emulsion (30% solids content) is mixed and pre-dispersed with an equal mass of cashew nutshell oil-modified phenolic resin at 60°C for 30 minutes; then, it is mixed with fillers such as wood flour in a kneader to ensure uniform dispersion of the nanoparticles in the resin matrix.

[0089] Comparative Example 3 (refer to cashew nut shell oil modified phenolic resin in CN103073690A) 100 parts of cashew nutshell oil-modified phenolic resin (50% cashew nutshell oil substitution for phenol, number average molecular weight 600, softening point 75℃) were added to a kneader and heated to 70℃. 30 parts of alkali-free glass fiber (4.5 mm length, 12 μm diameter) and a release agent (0.8 parts calcium stearate) were added, and kneading was performed at 60℃ for 25 minutes. 6 parts of hexamethylenetetramine were added, and the mixture was rapidly kneaded for 8 minutes before discharge. The mixture was then extruded, plasticized, and pelletized using a twin-screw extruder. This formulation represents a high-substitution-rate cashew nutshell oil-modified phenolic resin system without the addition of any flame retardants.

[0090] Using the test method of Preparation Example 1, its number-average molecular weight Mn was determined to be 600 and its softening point to be 75℃.

[0091] Comparative Example 4 (organosilicon-free modified magnesium-aluminum layered double hydroxide) The same resin formulation and preparation process as in Example 1 were used, namely 42 parts cashew nut shell oil modified phenolic resin, 12 parts aluminum diethylphosphinate, 8 parts type II ammonium polyphosphate, 5 parts melamine cyanurate, 32 parts glass fiber, 0.5 parts release agent (calcium stearate, 0.8 parts polyethylene wax), and 6.7 parts hexamethylenetetramine. The only difference was the absence of organosilicon-modified magnesium aluminum layered double hydroxide. The remaining preparation process was identical to that of Example 1. This comparative example retained the NP binary flame retardant system but removed the Si-based ceramic barrier component.

[0092] Without LDH, Ds(max) increased from 120 to 210 (an increase of 75%), proving that the Si-O-Si ceramic barrier is irreplaceable for smoke suppression.

[0093] Comparative Example 5 (Modified without cashew nut shell oil) The same flame-retardant system, reinforcement system, and preparation process as Example 1 were used, namely 12 parts aluminum diethylphosphinate, 8 parts ammonium type II polyphosphate, 5 parts melamine cyanurate, 3.5 parts organosilicon-modified magnesium aluminum layered double hydroxide, 32 parts glass fiber, a release agent, and hexamethylenetetramine. The only difference was that 42 parts of ordinary thermoplastic phenolic resin (number average molecular weight 900, softening point 110℃, not modified with cashew nut shell oil) were used instead of cashew nut shell oil-modified phenolic resin. The rest of the preparation process was completely consistent with Example 1. This comparative example retained the complete NP-Si ternary flame-retardant system and glass fiber reinforcement system, but removed the cashew nut shell oil toughening component.

[0094] Using the test method of Preparation Example 1, the number-average molecular weight (Mn) was determined to be 900, and the softening point was 110℃. Without cashew nut shell oil, the impact strength decreased from 42 to 28 kJ / m² (a decrease of 33%), while the Tg increased from 155 to 168℃, demonstrating that cashew nut shell oil achieves a balance between toughening and heat resistance within a 20-35% substitution rate window.

[0095] Comparative Example 6 (Replacing the NP-Si ternary system with a single APP) The same matrix resin, reinforcing system, and preparation process as in Example 1 were used, namely 42 parts cashew nut shell oil-modified phenolic resin, 32 parts glass fiber, release agent, and 6.7 parts hexamethylenetetramine. The only difference was that aluminum diethylphosphonate, ammonium polyphosphate, melamine cyanurate, and silicone-modified LDH were not added; instead, ammonium polyphosphate (Type II, 25 parts) was used as the sole flame retardant in the same total amount. The rest of the preparation process was completely consistent with Example 1.

[0096] When using a single APP, the LOI is only 30.5%, UL94 V-1 rating, and Ds(max) 340, while the NP-Si ternary system achieves LOI of 35.1-38.2%, UL94 V-0 rating, and Ds(max) of 95-145, proving that the flame retardant efficiency of the ternary synergy is far superior to that of the single component.

[0097] Comparative Example 7 (Cashew Shell Oil Modified Phenolic Resin with Low Substitution Rate – 10% Substitution Rate) 42 parts of cashew nut shell oil-modified phenolic resin (10% substitution rate) were used as the matrix resin, and the same other components and preparation process as in Example 1 were used.

[0098] Using the test method of Preparation Example 1, its number-average molecular weight Mn was determined to be 800 and its softening point to be 118℃.

[0099] Comparative Example 8 (LDH grafting rate 12%) Using the exact same formulation and process as in Example 1, except that the organosilicon-modified LDH was replaced with LDH-2 (grafting rate 12.3%, interlayer spacing 2.85 nm), and the amount was still 3.5 parts. The measured Ds(max) was 95 and the spiral flow was 215 mm.

[0100] Comparative Example 9 (LDH grafting rate 5%) Using the exact same formulation and process as in Example 1, except that the organosilicon-modified LDH was replaced with LDH-3 (grafting rate 5.2%, interlayer spacing 1.76 nm), and the amount was still 3.5 parts.

[0101] Test results show that the maximum value of Ds(max) in Example 1 (LDH-1, grafting rate 8.1%) is 120, while the maximum value of Ds(max) in Comparative Example 9 is 145. When the grafting rate is low, the Si-O-Si ceramic barrier is not dense and the smoke suppression effect decreases.

[0102] Comparative Example 10 (organosilicon-modified LDH less than 2 parts - dosage 1 part) Using the exact same formulation and process as Example 1, only the amount of organosilicon-modified LDH was reduced from 3.5 parts to 1 part. This comparative example was used to demonstrate that when the amount of LDH is less than 2 parts, the Si-O-Si ceramic barrier is incomplete and the smoke suppression effect is insufficient.

[0103] Test results show that, compared to the control group 10, Ds(max) increased to 185, LOI decreased to 32.5%, UL94 decreased to V-1 level, the Si-O-Si ceramic barrier was incomplete, and both smoke suppression and flame retardancy were insufficient.

[0104] Combining the experimental results of Comparative Examples 8 and 9: Example 1 (LDH-1, grafting rate 8.1%) had a Ds(max) of 120; Comparative Example 8 (LDH-2, grafting rate 12.3%) had a Ds(max) reduced to 95, achieving optimal smoke suppression, but the spiral flow length slightly decreased to 215 mm; Comparative Example 9 (LDH-3, grafting rate 5.2%) had a Ds(max) increased to 145, indicating that the Si-O-Si barrier was not dense enough and smoke suppression was insufficient. This shows that within the grafting rate range of 5-12%, a higher grafting rate results in a denser Si-O-Si ceramicized barrier and a better smoke suppression effect; a grafting rate of 8-12% can balance smoke suppression and processing flowability.

[0105] Comparative Example 11 (organosilicon-modified LDH higher than 5 parts - dosage 7 parts) Using the exact same formulation and process as in Example 1, except that the amount of silicone-modified LDH was increased from 3.5 parts to 7 parts. This comparative example was used to demonstrate that when the amount of LDH exceeds 5 parts, the processing fluidity decreases (spiral flow length <180 mm), and that excessive LDH tends to agglomerate during molding, leading to deterioration of mechanical properties.

[0106] Comparative Example 12 (High Substitution Rate Cashew Shell Oil Modified Phenolic Resin - 45% Substitution Rate) Using the exact same formulation and process as in Example 1, except that the matrix resin was replaced with cashew nutshell oil-modified phenolic resin at a substitution rate of 45%. Using the testing method of Preparation Example 1, its number-average molecular weight (Mn) was determined to be 700, and its softening point was 72°C.

[0107] Test results: LOI 31.5%, UL94 V-1 rating, Ds(max) 180, flexural strength 320 MPa, impact strength 46 kJ / m², Tg 112℃, helical flow length 245 mm. This comparative example shows that when the substitution rate is higher than 35%, excessive flexible segments lead to a decrease in crosslinking density, a drop in Tg to 112℃ (below the long-term service temperature requirement for aerospace interior parts), and a drop in LOI to 31.5% (approaching the lower limit of FAR 25.853 and UL94 only V-1), demonstrating the necessity of a substitution rate upper limit of 35%.

[0108] Comparative Example 13 (AlPi dosage: 6 parts, less than 8 parts) Similar to Example 1, except that the AlPi content was reduced from 12 parts to 6 parts. Test results: LOI 32.8%, UL94 V-1 rating, Ds(max) 165, pHRR 230 kW / m². This indicates that when the AlPi content is less than 8 parts, the char formation catalysis of the condensed phase is insufficient, the char layer is not dense, and the flame retardant rating decreases.

[0109] Comparative Example 14 (AlPi dosage 18 parts, higher than 15 parts) Similar to Example 1, except that the amount of AlPi was increased from 12 parts to 18 parts. Test results: LOI 36.9% (basically the same as Example 1), UL94 V-0 rating, but flexural strength decreased to 340 MPa, impact strength decreased to 35 kJ / m² (reaching the lower limit), and spiral flow length was 205 mm. This indicates that the flame retardant performance no longer improves when the amount of AlPi exceeds 15 parts, and powder agglomeration leads to deterioration of mechanical properties.

[0110] Comparative Example 15 (N / P imbalance – 8 MCA samples, 3 APP samples) Similar to Example 1, only the MCA was increased from 5 parts to 8 parts and the APP was reduced from 8 parts to 3 parts, while the total amount of flame retardant remained unchanged. The P / N molar ratio deviated from the optimal window (approximately 1:1.9). Test results: LOI 33.5%, UL94 V-1 rating, Ds(max) 190, pHRR 215 kW / m². This indicates that when the gas phase component is excessive and the char formation in the condensed phase is insufficient, the char layer is loose. Even with the same total amount of flame retardant, the synergistic efficiency still decreases significantly, proving the existence of the optimal N / P ratio window.

[0111] Performance test results The molding compounds prepared in Examples 1-3 and Comparative Examples 1-15 were molded into standard samples at 170°C and 15 MPa, and their performance was tested. The results are listed in Table 1.

[0112]

[0113]

[0114] The following conclusions can be drawn from the data in Table 1: (1) Flame retardant and smoke suppressant properties.

[0115] Examples 1-3 have an LOI of 35.1-38.2%, all meet UL94 V-0 rating, Ds(max) of 95-145, and pHRR of 160-200 kW / m², all satisfying the design objectives (LOI ≥ 35%, Ds(max) ≤ 150) and the requirements of FAR 25.853 for aerospace interior materials. Compared with existing technologies: Comparative Example 1 (traditional bromine-antimony system) has an LOI of 31.2% and a Ds(max) as high as 280, and faces environmental regulatory risks related to halogens; Comparative Example 2 (refer to CN101665613B) has an LOI of only 28.5% and meets UL94 V-1 rating; Comparative Example 3 (50% replacement rate, no flame retardant) has an LOI of only 24.8% and meets UL94 V-2 rating, all failing to meet aerospace interior material requirements.

[0116] (2) Necessity of ternary synergy.

[0117] Comparative Example 4 (without silicone-modified LDH) showed an increase in Ds(max) from 120 in Example 1 to 210 (an increase of 75%), and a pHRR of 220 kW / m². Comparative Example 6 (using a single APP to replace the ternary system, with the same total amount of flame retardant) had an LOI of only 30.5%, a UL94 V-1 rating, and a Ds(max) as high as 340. This demonstrates that the NP-Si ternary synergistic system is irreplaceable in terms of flame retardant efficiency and smoke suppression.

[0118] (3) Verification of the substitution rate window (20-35%) of claim 2.

[0119] Comparative Example 7 (10% replacement rate) showed an impact strength of only 32 kJ / m², indicating insufficient toughening. Comparative Example 12 (45% replacement rate) showed a Tg of only 112℃, a LOI of 31.5%, and a UL94 rating of V-1, indicating deterioration in heat resistance and flame retardancy. Combined with Examples 1-3 (25-35% replacement rate, impact strength 38-48 kJ / m², Tg 148-162℃), it is demonstrated that a 20-35% replacement rate window is the necessary range to balance toughening, heat resistance, and flame retardancy.

[0120] (4) Verification of the grafting rate range (5-12%) of claim 4.

[0121] Comparative Example 8 (grafting rate 12.3%) had a Ds(max) of 95, which was the best for smoke suppression, but the spiral flow length was slightly reduced to 215 mm; Comparative Example 9 (grafting rate 5.2%) had a Ds(max) of 145; Example 1 (grafting rate 8.1%) had a Ds(max) of 120 and a spiral flow of 225 mm, which balanced smoke suppression and processing fluidity.

[0122] (5) Verification of the amount of organosilicon-modified LDH used in claim 1 (2-5 parts).

[0123] Comparative Example 10 (1 part): Ds(max) increased to 185, LOI decreased to 32.5%, UL94 V-1 level, and the ceramic barrier was incomplete; Comparative Example 11 (7 parts): the spiral flow length decreased to 172 mm, which did not meet the processability requirements of precision molding, and excessive LDH was prone to agglomeration, leading to deterioration of mechanical properties.

[0124] (6) Verification of the amount of AlPi used in claim 1 (8-15 parts).

[0125] Comparative Example 13 (6 parts AlPi) had a LOI of 32.8% and a UL94 V-1 rating, indicating insufficient catalysis for char formation in the condensed phase. Comparative Example 14 (18 parts AlPi) had a LOI of 36.9% (basically the same as the example), but its flexural strength decreased to 340 MPa, impact strength decreased to 35 kJ / m², and spiral flow length decreased to 205 mm. Powder agglomeration led to deterioration in mechanical and processing properties, and flame retardancy was no longer improved.

[0126] (7) Verification of the optimal N / P ratio window.

[0127] Comparative Example 15, with the total amount of flame retardant unchanged, only changed the N / P ratio (8 parts MCA, 3 parts APP), resulting in a decrease in LOI from 36.5% to 33.5%, a drop in UL94 rating to V-1, and an increase in Ds(max) to 190, demonstrating the objective existence of an optimal window for the P / N molar ratio. Coefficient of thermal expansion (CTE): Tested according to ASTM E831 using a thermomechanical analyzer (TMA Q400, TA Instruments, USA). The test specimens were standard specimens from Examples 1-3 that were molded at 170°C and 15 MPa. The test temperature range was -55°C to +85°C, the heating rate was 5°C / min, and the atmosphere was nitrogen.

[0128] The CTE values ​​for Examples 1-3 were measured to be 2.5 × 10⁻⁶ in the range of -55°C to +85°C. -6 / ℃, 2.3×10 -6 / ℃ and 2.8×10 -6 / ℃, all meet the dimensional stability requirements of aerospace interior structural components under alternating high and low temperature environments.

[0129] The dielectric constant and dielectric loss were measured using the sample from Example 1 according to the ASTM D2520 resonant cavity method (10 GHz): dielectric constant 3.5, dielectric loss tangent 0.006. The above-mentioned low CTE and low dielectric properties are derived from the material composition of this invention (low polarity cashew nut shell oil segments, high volume fraction glass fiber, and low dielectric loss characteristics of silicone-modified LDH), which can be stably achieved through the formulation design of Examples 1-3.

[0130] Figure 1 This is a schematic diagram illustrating the NP-Si ternary synergistic flame-retardant mechanism of the flame-retardant phenolic resin molding compound composition of the present invention. The diagram demonstrates the synergistic effect of the triple flame-retardant mechanism: nitrogen-based (MCA+APP) gas-phase flame retardancy, phosphorus-based (AlPi+APP) condensed-phase char formation, and silicon-based (organosilicon-modified LDH) high-temperature ceramic barrier. In Example 1, this ternary synergistic system achieved an LOI of 36.5%, a UL94 V-0 rating, and a Ds(max) of 120.

[0131] Figure 2 The graph shows a comparison of the heat release rate (HRR) curves of the cone calorimeter for Examples 1-3 and Comparative Examples 1-15. In example (a), Examples 1-3 are compared with Comparative Examples 1-7, and (b), Examples 1-3 are compared with Comparative Examples 8-15. Solid lines are used to represent examples, and dashed lines are used to represent comparative examples. For example, EX1 represents Example 1 and CE1 represents Comparative Example 1. As shown in the figure, the pHRR of Examples 1-3 were 180, 160, and 200 kW / m², respectively, which were significantly lower than those of Comparative Example 1 (bromine-antimony system, 250 kW / m²), Comparative Example 2 (refer to CN101665613B, 320 kW / m²), Comparative Example 3 (no flame retardant, 350 kW / m²), and Comparative Example 6 (single APP, 280 kW / m²). The pHRR of Comparative Example 13 (6 parts AlPi, 230 kW / m²) and Comparative Example 15 (N / P imbalance, 215 kW / m²) were also significantly higher than those of the Examples, demonstrating the high flame retardancy of the NP-Si ternary synergistic system and its optimal ratio window.

[0132] Figure 3The figures show a comparison of the mechanical properties (flexural strength and impact strength) of Examples 1-3 and Comparative Examples 1-15. As can be seen from the figures, the flexural strength of Examples 1-3 is 350-410 MPa, and the impact strength is 38-48 kJ / m², significantly better than Comparative Example 2 (280 MPa, 22 kJ / m²) and Comparative Example 5 (295 MPa, 28 kJ / m²). Although the impact strength of Comparative Example 3 reaches 45 kJ / m², its Tg is only 115℃, lacking practical heat resistance. The impact strength of Comparative Example 7 (10% substitution rate) is only 32 kJ / m², indicating insufficient toughening. The impact strength of Comparative Example 14 (18 parts AlPi) drops to 35 kJ / m², and the flexural strength drops to 340 MPa. These results demonstrate the synergistic necessity of cashew nut shell oil toughening, glass fiber reinforcement, and the appropriate dosage window for the flame-retardant system.

[0133] Figure 4 The figure shows a comparison of the flame retardant and smoke suppression performance (LOI and smoke density Ds(max)) of Examples 1-3 and Comparative Examples 1-15. The dashed lines in the figure represent the design targets (LOI ≥ 35%, Ds(max) ≤ 150). As can be seen from the figure, the LOI of Examples 1-3 is 35.1-38.2% and Ds(max) is 95-145, which simultaneously meets both design targets; Comparative Example 4 (without LDH) has a Ds(max) of 210, which is 75% higher than that of Example 1 (120); Comparative Example 6 (single APP) has a Ds(max) of 340 and an LOI of only 30.5% (V-1 level); Comparative Example 12 (replacement rate 45%) has a LOI that has decreased to 31.5%, and Comparative Example 13 (6 parts of AlPi) has a LOI that has decreased to 32.8%, which proves the necessity of ternary synergy and each dosage window.

[0134] Based on the test results of Comparative Examples 3-15, the following synergistic effect conclusions can be drawn: A significant synergistic effect exists among the five components of this invention: cashew nutshell oil-modified phenolic resin, aluminum diethylphosphinate, ammonium polyphosphate, melamine cyanurate, and organosilicon-modified magnesium-aluminum layered double hydroxide. Organosilicon-modified LDH is responsible for constructing a Si-O-Si ceramic barrier to suppress smoke release and subsequent heat release; cashew nutshell oil-modified phenolic resin provides high toughness; and the NP-Si ternary synergistic system collectively achieves highly efficient halogen-free flame retardancy, which cannot be replaced by a single flame retardant. All five components are indispensable and together constitute a comprehensive performance system that meets the FAR 25.853 aerospace interior material standard.

[0135] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of this disclosure is defined by the appended claims.

Claims

1. A flame-retardant phenolic resin molding compound composition, characterized in that, By weight, including: Cashew shell oil modified phenolic resin 35-50 parts; 8-15 parts of aluminum diethylphosphinate; 5-10 parts of ammonium polyphosphate; 3-6 parts of melamine cyanurate; 25-40 parts glass fiber; Organosilicon-modified magnesium-aluminum layered double hydroxide, 2-5 parts; 5-8 parts of curing agent.

2. The flame-retardant phenolic resin molding compound composition according to claim 1, characterized in that, The cashew nut shell oil modified phenolic resin is prepared by polycondensation of phenol, cashew nut shell oil and formaldehyde under an alkaline catalyst. The mass substitution rate of cashew nut shell oil for phenol is 20-35%, the number average molecular weight is 800-1500, and the softening point is 85-110℃.

3. The flame-retardant phenolic resin molding compound composition according to claim 1, characterized in that, The aluminum diethylphosphonate has an average particle size of 10-50 micrometers; and / or the ammonium polyphosphate is type II ammonium polyphosphate with a degree of polymerization greater than 1000 and a solubility of less than 0.5 g / 100 mL water; and / or the melamine cyanurate has a particle size of 5-30 micrometers.

4. The flame-retardant phenolic resin molding compound composition according to claim 1, characterized in that, The interlayer spacing of the organosilicon-modified magnesium-aluminum layered double hydroxide is 1.5-3.0 nm, and the organosilicon grafting rate is 5-12%.

5. The flame-retardant phenolic resin molding compound composition according to claim 4, characterized in that, The preparation method of the organosilicon-modified magnesium-aluminum layered double hydroxide includes dispersing the magnesium-aluminum layered double hydroxide in an ethanol / water mixed solvent, adding an aminosilane coupling agent, and reacting at 70-80℃ for 4-6 h; wherein, the Mg / Al molar ratio is 2:1-3:1, and the mass ratio of magnesium-aluminum layered double hydroxide to aminosilane coupling agent is (92-85%): (8-15%).

6. The flame-retardant phenolic resin molding compound composition according to claim 1, characterized in that, The glass fiber is alkali-free glass fiber with a fiber length of 3-6 mm and a fiber diameter of 10-14 micrometers.

7. The flame-retardant phenolic resin molding compound composition according to claim 1, characterized in that, The curing agent is hexamethylenetetramine, and its content is 14-18% of the mass of cashew nut shell oil-modified phenolic resin.

8. The flame-retardant phenolic resin molding compound composition according to claim 1, characterized in that, The composition further includes 0.5-1.5 parts of a release agent, which is a mixture of calcium stearate and polyethylene wax in a mass ratio of 1:(1-2).

9. A method for preparing a flame-retardant phenolic resin molding compound composition according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Add cashew shell oil-modified phenolic resin to a kneader, heat to 70-90℃, add aluminum diethylphosphonate, ammonium polyphosphate and melamine cyanurate, and knead for 15-25 minutes. S2. Add organosilicon-modified magnesium-aluminum layered double hydroxide and release agent, and continue kneading for 10-15 minutes; S3. Add glass fiber and knead at 50-70℃ for 20-30 minutes to ensure uniform fiber impregnation. S4. Add curing agent, knead quickly for 5-10 minutes, and discharge and cool to room temperature; S5. The mixture is plasticized and extruded through a twin-screw extruder. The sections from the feed port to the die head are sequentially divided into a feeding section, a plasticizing section, a metering section, and a die head section. The temperature of each section of the barrel from the feed port to the die head section is 90-95℃→100-110℃→110-120℃→100-115℃, the screw length-to-diameter ratio is 28-35:1, the material residence time in the barrel is 45-90 seconds, the screw speed is 30-60 rpm, and the mixture is pelletized or crushed to obtain the flame-retardant phenolic resin molding compound composition.

10. The preparation method according to claim 9, characterized in that, In step S5, the length-to-diameter ratio of the twin-screw extruder is 28-35:1, and the die temperature is 100-115℃.

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