Preparation of flame-retardant high-toughness PMI foam

Abstract

The invention discloses preparation of flame-retardant high-toughness PMI foam, and relates to the technical field of high-performance materials. Methacrylic acid, methacrylonitrile, an initiator, a modifier, a foaming agent, a cross-linking agent and a nucleating agent are adopted as main raw materials, a reaction solution is obtained after thickening treatment, then the reaction solution is injected into a mold, and water bath polymerization reaction and heating foaming are performed to prepare the foaming agent. The PMI foam material prepared by the method has excellent flame retardance and high toughness, and is suitable for the fields of aerospace, rail transit and high-end structural materials.

Description

Technical Field

[0001] The invention relates to the technical field of high-performance materials, in particular to the preparation of flame-retardant high-toughness PMI foam. Background Art

[0002] PMI (polymethacrylimide) foam is a closed-cell high-performance foam material with excellent physical and chemical properties, including high specific strength, high specific stiffness, excellent heat resistance and chemical corrosion resistance. Therefore, it is widely used in aerospace, rail transportation, wind turbine blades and sandwich core materials of high-end structural composite materials. However, with the continuous improvement of modern industry's requirements for material performance, the shortcomings of traditional PMI foam are gradually emerging.

[0003] Insufficient toughness: Although traditional PMI foam has high strength and stiffness, its toughness is low, which is manifested in poor elongation at break and impact resistance. In actual use, especially in complex mechanical environments (such as vibration and impact loading of aerospace structures), foam materials are prone to brittle fracture, affecting the safety and durability of the structure. Therefore, improving the toughness of PMI foam is a technical problem that needs to be solved urgently.

[0004] Limited flame retardancy: As a polymer material, PMI foam is inherently flammable, which poses a major safety hazard in certain special fields (such as aerospace and rail transit). Although traditional methods can improve flame retardancy by adding flame retardants or modifying the surface by coating, these methods often have certain limitations: adding flame retardants may reduce the mechanical properties of the foam; surface modification can only improve local flame retardancy, but cannot completely solve the flammability problem inside the material. Therefore, how to achieve the intrinsic flame retardancy of PMI foam while ensuring mechanical properties has become a hot topic in current research.

[0005] With the widespread application of composite materials in the fields of aerospace, rail transportation and clean energy, the comprehensive performance of PMI foam as a lightweight core material directly affects the overall performance of composite materials. For example, the demand for lightweight materials in modern aircraft requires that the foam not only has low density and high strength, but also needs to remain stable in high temperature environments and have excellent flame retardant properties; high-speed trains and subway systems have extremely high safety requirements, and the flame retardancy and toughness of the material are particularly critical. Therefore, the market demand for high-performance PMI foam is becoming more and more urgent. Summary of the invention

[0006] In order to solve the technical problems in the above-mentioned background technology, the present invention optimizes the raw material ratio and the preparation process, adopts methacrylic acid and methacrylonitrile as main monomers, introduces a flame retardant modifier and a special thickener, and combines specific polymerization and foaming conditions to prepare a flame retardant high-toughness PMI foam.

[0007] In order to achieve the above-mentioned invention object, this method proposes the following solution: A flame retardant high-toughness PMI foam preparation method, characterized by comprising the following steps: Mix the following components in parts by mass: Methacrylic acid 40-60 parts; Methacrylonitrile 40-60 parts; Initiator 0.1-1.0 part; Flame retardant 5-15 parts; 5-15 parts of foaming agent; Cross-linking agent 0.1-1.0 part; Nucleating agent 0.1-2.0 parts Thickener 0.5-3.0 parts; The mixture is mixed and thickened by mechanical stirring to obtain a material mixture; the obtained material mixture is injected into a mold, and a polymerization reaction is carried out in a water bath environment to obtain a solidified polymer material; the polymer material is foamed in a heating environment, cooled, and then demolded to obtain a flame-retardant high-toughness PMI foam.

[0008] Furthermore, the initiator is one or more of ammonium persulfate, potassium persulfate, benzoyl peroxide or azobisisobutyronitrile.

[0009] Furthermore, the preparation method of the flame retardant is: 1) Raw material preparation: accurately weigh the raw materials according to the formula ratio, 15-25 parts of 2-amino-1,3,5-triazine, CAS number: 4122-04-7; 2-6 parts of allyl (cyclopentadienyl) nickel, CAS: 12107-46-9; 30-60 parts of allyl triphenylphosphine, CAS number: 15935-94-1; 3-6 parts of sodium ethoxide; 200-260 parts of dichloromethane, to ensure that the purity of the raw materials meets the requirements; 2) Dissolving and mixing: Add 2-amino-1,3,5-triazine, allyl(cyclopentadienyl)nickel, allyl triphenylphosphine and sodium ethoxide into dichloromethane solvent, place the reaction solution in a temperature-controlled reactor, set the temperature between 72-85°C, and control the reaction time within the range of 0.5-10 hours; 3) Reaction process monitoring: During the reaction process, regular sampling and analysis are performed to monitor the reaction progress and product generation; 4) Post-treatment and purification: After the reaction is completed, the chloroform is distilled off, and the washing and drying steps are performed to obtain a high-purity flame retardant.

[0010] Furthermore, the foaming agent is one or more of isobutane, n-pentane, isopentane or carbon dioxide.

[0011] Furthermore, the cross-linking agent is one or more of bisacrylamide, ethylene glycol dimethacrylate, divinylbenzene and isophthalic acid dienyl ester.

[0012] Furthermore, the nucleating agent is one or more of calcium silicate, silicon dioxide, calcium carbonate or barium sulfate.

[0013] Furthermore, the thickener is carboxymethyl cellulose, polyvinyl alcohol or gelatin.

[0014] Furthermore, the polymerization reaction temperature is controlled at 25-120° C., and the reaction time is 100-350 minutes.

[0015] Furthermore, the temperature of the heating foaming treatment is controlled at 140-250° C., and the time is 0.5-10 hours.

[0016] Technical effect: The present invention successfully prepared a PMI foam material with both high toughness and flame retardant properties by optimizing the formula and process conditions. Systematic testing shows that the material has significant advantages in mechanical properties and flame retardant properties, which are specifically manifested as follows: 1) Significantly improved mechanical properties: Improved tensile strength: The material's bearing capacity under external force is significantly enhanced, showing a higher strength grade, which can meet the use requirements of high-load structural parts; Improved elongation at break: The toughness is significantly improved, and the material's deformation ability under high strain conditions is enhanced, which can better resist external impact or vibration loads.

[0017] 2) Excellent flame retardant performance A) Enhanced carbonization effect: The introduction of triazine-based compounds significantly enhances the carbonization ability of PMI foam, making the carbon layer formed after combustion denser and more continuous, effectively isolating the transfer of oxygen and heat.

[0018] B) Improved compatibility: Through molecular design, the flame retardant has good compatibility with the PMI foam matrix, avoiding the problem of material performance degradation caused by large additions of traditional flame retardants.

[0019] C) Improve thermal stability and durability: Triazine-based compounds themselves have excellent thermal stability and durability, and can maintain stable performance for a long time at high temperatures, thereby improving the overall thermal stability and service life of PMI foam.

[0020] D) Synergistic flame retardant effect: The synergistic effect between the three functional groups of triazine, nickelocene and triphenylphosphine further enhances the flame retardant effect, so that PMI foam can still maintain good flame retardant properties when facing higher temperatures and more complex environments. The triazine ring is one of the core structures of the flame retardant, which has high thermal and chemical stability and can maintain structural integrity at high temperatures. Nickelocene, as a transition metal complex, has good catalytic activity and coordination ability, which can promote the decomposition and carbonization process of triazine compounds. Triphenylphosphine is an efficient phosphorus-based flame retardant. The phosphorus free radicals produced by its decomposition can effectively quench hydrogen free radicals in the flame and interrupt the combustion chain reaction. The synergistic effect between the three functional groups enables the flame retardant to simultaneously exert multiple flame retardant mechanisms such as heat absorption, release of non-combustible gas, formation of carbon layer and quenching of free radicals during the combustion process, thereby achieving efficient flame retardant effect. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0022] Detection method: 1) Tensile strength and elongation at break: According to ASTM D638 standard, the tensile strength and elongation at break were tested at room temperature with a test speed of 10 mm / min; 2) Oxygen Index (LOI): Tested according to ISO 4589 standard, recording the minimum oxygen concentration required to maintain sample combustion; 3) Flame retardancy (UL 94 grade): vertical burning performance is tested according to UL 94 standard.

[0023] Example 1: PMI foam was prepared according to the following ratio: 50 g methacrylic acid, 50 g methacrylonitrile, 0.5 g ammonium persulfate as an initiator, 5 g flame retardant, 10 g isobutane as a foaming agent, 0.5 g bisacrylamide as a crosslinking agent, 1 g calcium silicate as a nucleating agent and 2 g carboxymethyl cellulose as a thickener were mixed in parts by mass and thickened by mechanical stirring. Subsequently, the mixture was injected into a mold and polymerized in a 60°C water bath for 200 minutes to obtain a cured polymer material. The polymer material was foamed in a 180°C heating environment for 4 hours, and demolded after cooling to obtain the flame-retardant high-toughness PMI foam.

[0024] The preparation method of the flame retardant is as follows: 15g of 2-amino-1,3,5-triazine (CAS No.: 4122-04-7), 2g of allyl (cyclopentadienyl) nickel (CAS: 12107-46-9), 30g of allyl triphenylphosphine (CAS No.: 15935-94-1) and 3g of sodium ethoxide are added into 200g of dichloromethane solvent, the reaction liquid is placed in a temperature-controlled reactor, the temperature is set at 72°C, the reaction time is controlled within 2 hours, after the reaction is completed, the chloroform is removed by distillation, and washing and drying steps are performed to obtain a high-purity flame retardant.

[0025] Example 2: PMI foam was prepared according to the following ratio: 45g methacrylic acid, 55g methacrylonitrile, 0.8g benzoyl peroxide as an initiator, 10g flame retardant, 12g n-pentane as a foaming agent, 0.7g ethylene glycol dimethacrylate as a crosslinking agent, 0.5g silica as a nucleating agent and 1.5g polyvinyl alcohol as a thickener were mixed in parts by mass. The mixture was injected into a mold after mechanical stirring and polymerized in a 90°C water bath for 250 minutes. Then, the foaming treatment was carried out at 200°C for 6 hours, and after cooling and demolding, the flame-retardant high-toughness PMI foam was obtained.

[0026] The preparation method of the flame retardant is as follows: 20g of 2-amino-1,3,5-triazine (CAS No.: 4122-04-7), 4g of allyl (cyclopentadienyl) nickel (CAS: 12107-46-9), 40g of allyl triphenylphosphine (CAS No.: 15935-94-1) and 4g of sodium ethoxide are added into 220g of dichloromethane solvent, the reaction liquid is placed in a temperature-controlled reactor, the temperature is set at 76°C, the reaction time is controlled at 5 hours, after the reaction is completed, the chloroform is removed by distillation, and washing and drying steps are performed to obtain a high-purity flame retardant.

[0027] Example 3: PMI foam is prepared according to the following ratio: 60g methacrylic acid, 40g methacrylonitrile, 0.3g azobisisobutyronitrile as initiator, 10g flame retardant, 8g isopentane as foaming agent, 0.3g divinylbenzene as crosslinking agent, 1.5g calcium carbonate as nucleating agent and 2.5g gelatin as thickener are mixed in parts by mass. After the mixture is thickened by mechanical stirring, it is injected into the mold and polymerized in a water bath at 110°C for 150 minutes. Then, the polymer material is foamed in a heating environment at 160°C for 2 hours, cooled and demolded to obtain the flame retardant high-toughness PMI foam.

[0028] The preparation method of the flame retardant is as follows: 20g of 2-amino-1,3,5-triazine (CAS No.: 4122-04-7), 4g of allyl (cyclopentadienyl) nickel (CAS: 12107-46-9), 50g of allyl triphenylphosphine (CAS No.: 15935-94-1) and 5g of sodium ethoxide are added into 240g of dichloromethane solvent, the reaction liquid is placed in a temperature-controlled reactor, the temperature is set at 80°C, the reaction time is controlled at 8 hours, after the reaction is completed, the chloroform is removed by distillation, and washing and drying steps are performed to obtain a high-purity flame retardant.

[0029] Example 4: PMI foam was prepared according to the following ratio: 40g methacrylic acid, 60g methacrylonitrile, 1.0g potassium persulfate as an initiator, 15g flame retardant, 15g carbon dioxide as a foaming agent, 1.0g isophthalic acid diene ester as a crosslinking agent, 2.0g barium sulfate as a nucleating agent and 3.0g carboxymethyl cellulose as a thickener were mixed in parts by mass. After uniform mixing, the mixture was injected into a mold and polymerized in a 25°C water bath for 350 minutes. Afterwards, the mixture was foamed in a 250°C heating environment for 0.5 hours, cooled and demolded to obtain the flame-retardant high-toughness PMI foam.

[0030] The preparation method of the flame retardant is as follows: 25g of 2-amino-1,3,5-triazine (CAS No.: 4122-04-7), 6g of allyl (cyclopentadienyl) nickel (CAS: 12107-46-9), 60g of allyl triphenylphosphine (CAS No.: 15935-94-1) and 6g of sodium ethoxide are added into 260g of dichloromethane solvent, the reaction liquid is placed in a temperature-controlled reactor, the temperature is set at 85°C, the reaction time is controlled at 10 hours, after the reaction is completed, the chloroform is removed by distillation, and washing and drying steps are performed to obtain a high-purity flame retardant.

[0031] Comparative Example 1 In this example, except that no flame retardant is added, the rest is the same as in Example 1.

[0032] Comparative Example 2 This example is the same as Example 1 except that allyl(cyclopentadienyl)nickel is not added during the preparation of the flame retardant.

[0033] Comparative Example 3 This example is the same as Example 1 except that 2-amino-1,3,5-triazine is not added during the preparation of the flame retardant.

[0034] The PMI test results prepared in the above specific implementation method are shown in Table 1.

[0035] Table 1 Density Kg / m3 Tensile strength MPa Elongation at break % Oxygen index% Flame retardant grade Example 1 51.1 2.21 4.5 32.2 UL 94 V-1 rating Example 2 52.3 2.28 4.9 33.0 UL 94 V-1 rating Example 3 52.5 2.34 5.1 33.5 UL 94 V-0 rating Example 4 53.0 2.41 5.7 34.4 UL 94 V-0 rating Comparative Example 1 44.7 1.67 2.5 10.8 / Comparative Example 2 48.4 1.94 3.4 24.7 UL 94 HB grade Comparative Example 3 47.5 1.85 3.1 23.2 UL 94 HB grade The above test methods and results fully demonstrate that the method of the present invention can significantly improve the mechanical properties and flame retardant properties of PMI foam and has wide application value.

[0036] The above embodiments describe the present invention in detail, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A flame retardant high toughness PMI foam preparation, characterized in that: The following steps are involved: Mix the following components in parts by mass: Methacrylic acid 40-60 parts; Methacrylonitrile 40-60 parts; Initiator 0.1-1.0 part; Flame retardant 5-15 parts; 5-15 parts of foaming agent; Cross-linking agent 0.1-1.0 part; Nucleating agent 0.1-2.0 parts; Thickener 0.5-3.0 parts; The mixture is mixed and thickened by mechanical stirring to obtain a material mixture; the obtained material mixture is injected into a mold, and a polymerization reaction is carried out in a water bath environment to obtain a solidified polymer material; the polymer material is foamed in a heating environment, cooled, and then demolded to obtain a flame-retardant high-toughness PMI foam; The flame retardant is prepared by reacting 2-amino-1,3,5-triazine, allyl (cyclopentadienyl) nickel and allyl triphenylphosphine.

2. The method for preparing a flame retardant high toughness PMI foam according to claim 1, characterized in that: The initiator is one or more of ammonium persulfate, potassium persulfate, benzoyl peroxide or azobisisobutyronitrile.

3. The method for preparing a flame retardant high toughness PMI foam according to claim 1, characterized in that: The preparation method of the flame retardant is: 1) Raw material preparation: accurately weigh the raw materials according to the formula ratio, 15-25 parts of 2-amino-1,3,5-triazine, 2-6 parts of allyl (cyclopentadienyl) nickel, 30-60 parts of allyl triphenylphosphine, 3-6 parts of sodium ethoxide, 200-260 parts of dichloromethane, and ensure that the purity of the raw materials meets the requirements; 2) Dissolving and mixing: Add 2-amino-1,3,5-triazine, allyl(cyclopentadienyl)nickel, allyl triphenylphosphine and sodium ethoxide into dichloromethane solvent, place the reaction solution in a temperature-controlled reactor, set the temperature between 72-85°C, and control the reaction time within the range of 0.5-10 hours; 3) Reaction process monitoring: During the reaction process, regular sampling and analysis are performed to monitor the reaction progress and product generation; 4) Post-treatment and purification: After the reaction is completed, the chloroform is distilled off, and the washing and drying steps are performed to obtain a high-purity flame retardant.

4. The preparation of a flame retardant high toughness PMI foam according to claim 1, characterized in that: The foaming agent is one or more of isobutane, n-pentane, isopentane or carbon dioxide.

5. The preparation of a flame retardant high toughness PMI foam according to claim 1, characterized in that: The crosslinking agent is one or more of bisacrylamide, ethylene glycol dimethacrylate, divinylbenzene and isophthalic acid dienyl ester.

6. The flame retardant high toughness PMI foam preparation according to claim 1, characterized in that: The nucleating agent is one or more of calcium silicate, silicon dioxide, calcium carbonate or barium sulfate.

7. The flame retardant high toughness PMI foam preparation according to claim 1, characterized in that: The thickener is carboxymethyl cellulose, polyvinyl alcohol or gelatin.

8. The flame retardant high toughness PMI foam preparation according to claim 1, characterized in that: The polymerization reaction temperature is controlled at 25-120° C. and the reaction time is 100-350 minutes.

9. The flame retardant high toughness PMI foam preparation according to claim 1, characterized in that: The temperature of the heating foaming treatment is controlled at 140-250° C. and the time is 0.5-10 hours.