Bionic gradient flame-retardant polyester material and preparation method thereof

Abstract

The invention provides a bionic gradient flame-retardant polyester material and a preparation method thereof. The preparation method comprises the following steps: S1, preparing raw materials: preparing an outer layer from PET, maleic anhydride grafted PET, nano clay and ammonium polyphosphate, preparing a middle layer from PET, maleic anhydride grafted PET, microencapsulated red phosphorus and polytetrafluoroethylene, and preparing an inner layer from PET, maleic anhydride grafted PET and short carbon fibers; s2, carrying out extrusion granulation by adopting a three-layer co-extrusion granulator, and carrying out vacuum drying to obtain gradient master batches; s3, the gradient master batches are subjected to injection molding through a multi-layer injection molding machine; and S4, performing hot press molding in a hot press to obtain the product. According to the invention, nano clay and ammonium polyphosphate are intensively distributed on the outer layer to form a compact carbon layer barrier; microencapsulated red phosphorus in the middle layer is heated to release active phosphorus free radicals, the gas phase-solid phase synergistic flame retardant effect is achieved, the material passes the UL94V-0 level, and the LOI is improved; the chopped carbon fiber reinforced matrix is added to the inner layer, and the interlayer interface bonding force is improved by combining with maleic anhydride grafted PET, so that the effect of high mechanical property is achieved.

Description

Technical Field

[0001] This invention relates to the field of polyester materials, specifically to biomimetic gradient flame-retardant polyester materials and their preparation methods. Background Technology

[0002] Polyester is a well-rounded material with good transparency and high gloss; it also possesses excellent airtightness and aroma retention. Compared to general materials, polyester has relatively better mechanical properties, with superior tensile strength and impact resistance. Polyester also exhibits excellent resistance to weak acids and oils, and is non-toxic and has good chemical stability. Due to these numerous advantages, polyester is widely used as a high-end packaging material for various textiles, precision instruments, and electrical components. However, with the development of society and economy, the functional requirements for polyester materials are getting higher and higher, and flame retardancy is one of them. At present, the flame retardant modification of polyester materials mainly relies on the following methods, but all of them have significant defects: (1) Halogenated flame retardants (such as decabromodiphenyl ether): Although the flame retardant efficiency is high (LOI>30%), it releases toxic gases (dioxins) when burning; (2) Halogen-free flame retardant system: Phosphorus flame retardants: The amount added needs to be >15wt% to achieve V-0 level, which leads to material embrittlement; (3) Nano flame retardants (layered silicates): Although they can improve char formation, the dispersion is poor and stress concentration is easy to occur; (4) Homogeneous blending process: The flame retardant is randomly distributed in the matrix, and it cannot quickly form a continuous protective layer when burning. Excessive addition is required to pass the UL94 test. Therefore, high flame retardancy requires a large amount of flame retardant, but it will sacrifice mechanical properties; traditional materials cannot meet the additional requirements of low smoke and antibacterial properties at the same time. Therefore, it is urgent to develop a PET composite material with good flame retardancy without sacrificing mechanical properties. Summary of the Invention

[0003] The technical problem to be solved: The purpose of this invention is to provide a biomimetic gradient flame-retardant polyester material and its preparation method. By concentrating nano-clay and ammonium polyphosphate in the outer layer, a dense carbon layer barrier is formed; combined with the release of active phosphorus free radicals from microcapsule red phosphorus in the middle layer upon heating, a gas-phase-solid phase synergistic flame-retardant effect is achieved, enabling the material to pass the UL94 V-0 rating and improve the LOI; short-cut carbon fiber is added to the inner layer to reinforce the matrix, and maleic anhydride-grafted PET is combined to improve the interlayer interface bonding force, achieving a high mechanical performance effect.

[0004] Technical solution: Biomimetic gradient flame-retardant polyester material, comprising a three-layer structure from the outside to the inside, namely: outer layer: a highly flame-retardant layer containing nano-clay and ammonium polyphosphate; middle layer: a responsive layer containing microencapsulated red phosphorus; and inner layer: a carbon fiber reinforced mechanical support layer. The preparation method of the above-mentioned biomimetic gradient flame-retardant polyester material includes the following steps: S1. Preparation of raw materials: Outer layer: By weight, it comprises 80 parts PET, 0.5 parts maleic anhydride-grafted PET, 5-10 parts nano-clay, and 5-10 parts ammonium polyphosphate. Intermediate layer: By weight, it comprises 85 parts PET, 0.5 parts maleic anhydride-grafted PET, 5-10 parts microencapsulated red phosphorus, and 5 parts polytetrafluoroethylene. Inner layer: by weight, it contains 90 parts PET, 0.5 parts maleic anhydride-grafted PET, and 5-10 parts chopped carbon fiber; S2. Preparation of gradient masterbatch: Gradient masterbatch was obtained by extrusion granulation using a three-layer co-extrusion granulator and vacuum drying at 120℃ for 4 hours. S3. Inject the gradient masterbatch into shape using a multi-layer injection molding machine; S4. Place the injection-molded preform in a hot press and hot press to form the final product. Furthermore, the preparation method of the microcapsule red phosphorus in S1 is as follows: S11. Disperse red phosphorus powder in an aqueous solution containing 1 wt% polyvinyl alcohol and sonicate for 30 min; S12. Add methyl methacrylate monomer and 0.5 wt% potassium persulfate, and react at 70°C for 4 h; S13. Filter, wash and dry to obtain microcapsule red phosphorus. Furthermore, the particle size of the red phosphorus powder in S11 is ≤10μm. Furthermore, the mass ratio of the red phosphorus powder to methyl methacrylate is 1:3. Furthermore, the length of the short-cut carbon fiber in S1 is 2-3 mm. Furthermore, the extrusion granulation conditions in S2 are as follows: screw length-to-diameter ratio is 40:1; extrusion temperature is: outer layer: 250-260℃, middle layer: 245-255℃, inner layer: 255-265℃; screw speed is 200 rpm. Furthermore, the thickness ratio of the outer layer:middle layer:inner layer in S2 is 3:(1.5-2):5. Furthermore, the injection molding conditions in S3 are: melt temperature of 250-260℃, mold temperature of 75-85℃, and injection pressure of 80-100MPa. Furthermore, the hot pressing conditions in S4 are: temperature 225-235℃, pressure 9.5-10.5MPa, holding time 10min, followed by cooling to room temperature at a rate of 20℃ / min. Beneficial effects: 1. This invention forms a dense carbon layer barrier by concentrating nano-clay and ammonium polyphosphate in the outer layer; combined with the release of active phosphorus free radicals from microcapsule red phosphorus in the middle layer upon heating, it achieves a gas-solid phase synergistic flame retardant effect, enabling the material to pass UL94V-0 level and improve LOI. 2. This invention achieves high mechanical properties by adding short-cut carbon fiber to the inner layer to reinforce the matrix and combining it with maleic anhydride-grafted PET to improve the interlayer bonding force. 3. This invention suppresses the oxidation and smoke production during the combustion of red phosphorus by coating the microcapsule red phosphorus with a PMMA shell (coating rate > 90%); combined with the densification of the carbon layer by nano-clay catalysis, the smoke density is reduced. 4. This invention precisely controls melt flow through a three-layer co-extrusion process (outer layer 255℃ / middle layer 250℃ / inner layer 260℃), combined with a screw speed of 200 rpm and vacuum drying (120℃×4h), achieving no delamination at the gradient masterbatch interface and a high injection molding yield. 5. This invention achieves no dripping or sparking during combustion by adding polytetrafluoroethylene as an anti-dripping agent in the intermediate layer, combined with the phased release characteristics of microencapsulated red phosphorus (thermal decomposition temperature 317℃), while also expanding the smoke suppression function. 6. This invention stabilizes the carbon layer through the layered structure of nano-clay (interlayer spacing ≥ 2nm), and improves the LOI retention rate by combining the damp heat resistance of microcapsules; moreover, the material can be recycled three times and has a high mechanical property retention rate. Detailed Implementation This invention proposes a biomimetic gradient flame-retardant polyester material and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following will provide a more detailed description of the invention with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Example 1 The preparation method of microencapsulated red phosphorus is as follows: S11. Disperse 1 kg of red phosphorus powder with a particle size of 1-10 μm in 20 L of an aqueous solution containing 1 wt% polyvinyl alcohol, and sonicate for 30 min. S12. Add 3 kg of methyl methacrylate monomer and 0.015 kg of potassium persulfate, and react at 70 °C for 4 h; S13. Filter, wash and dry to obtain microcapsule red phosphorus. The particle size of the microencapsulated red phosphorus was determined to be 20-50 μm, with a coating rate of >90% and a thermal decomposition temperature of 317℃. Example 2 A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 5kg of nano-clay and 10kg of ammonium polyphosphate; Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 8kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Example 3 A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of nano-clay and 7kg of ammonium polyphosphate; Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 8kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Example 4 A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 10kg of nano-clay and 5kg of ammonium polyphosphate; Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 8kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Example 5 A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of nano-clay and 7kg of ammonium polyphosphate; Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 5kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 8kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Example 6 A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of nano-clay and 7kg of ammonium polyphosphate; Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 10kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 8kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Example 7 A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of nano-clay and 7kg of ammonium polyphosphate; Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 5kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Example 8 A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of nano-clay and 7kg of ammonium polyphosphate; Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 10kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Example 9 A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of nano-clay and 7kg of ammonium polyphosphate; Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 8kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, and inner layer: 260℃; screw speed of 200 rpm; and vacuum drying at 120℃ for 4 hours to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:1.5:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Comparative Example 1 The difference between this embodiment and embodiment 3 is that it does not use 3 layers. Specifically: A method for preparing flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: 85kg PET, 0.5kg maleic anhydride-grafted PET, 8kg nano clay, 7kg ammonium polyphosphate, 8kg microencapsulated red phosphorus, 5kg polytetrafluoroethylene and 8kg short-cut carbon fibers with a length of 2-3mm; S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using an extrusion granulator. The extrusion granulation conditions were: screw length-to-diameter ratio of 40:1; extrusion temperature of 255℃; screw speed of 200 rpm; and vacuum drying at 120℃ for 4 hours to obtain masterbatch. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Comparative Example 2 The difference between this embodiment and Embodiment 3 is that microencapsulated red phosphorus is not used. Specifically: A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: Contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of nano-clay, and 7kg of ammonium polyphosphate; Middle layer: Contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, and 5kg of polytetrafluoroethylene. Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET, and 8kg of short-cut carbon fibers with a length of 2-3mm; S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. Comparative Example 3 The difference between this embodiment and Embodiment 3 is that it does not use nano-free clay. Specifically: A method for preparing biomimetic gradient flame-retardant polyester materials includes the following steps: S1. Preparation of raw materials: Outer layer: Contains 80kg of PET, 0.5kg of maleic anhydride-grafted PET, and 7kg of ammonium polyphosphate. Middle layer: contains 85kg of PET, 0.5kg of maleic anhydride-grafted PET, 8kg of microencapsulated red phosphorus and 5kg of polytetrafluoroethylene; Inner layer: contains 90kg of PET, 0.5kg of maleic anhydride-grafted PET and 8kg of short-cut carbon fibers with a length of 2-3mm. S2. Preparation of gradient masterbatch: Extrusion granulation was carried out using a three-layer co-extrusion granulator. The extrusion granulation conditions were as follows: screw length-to-diameter ratio of 40:1; extrusion temperature of outer layer: 255℃, middle layer: 250℃, inner layer: 260℃; screw speed of 200 rpm; vacuum drying at 120℃ for 4 h to obtain gradient masterbatch with an outer layer:middle layer:inner layer thickness ratio of 3:2:5. S3. The gradient masterbatch is injection molded using a multi-layer injection molding machine. The injection conditions are: melt temperature 255℃, mold temperature 80℃, and injection pressure 90MPa. S4. Place the injection-molded preform in a hot press for hot pressing at a temperature of 230°C, a pressure of 10MPa, and a holding time of 10min. Then cool it to room temperature at a rate of 20°C / min to obtain the final product. According to national standards, the mechanical properties of the above embodiments and comparative examples were measured, and the results are shown in Table 1 below: Table 1 Characterization of the mechanical properties of materials in each embodiment Tensile strength (MPa) Elongation at break (%) Bending strength (MPa) <![CDATA[Impact strength (kJ / m 2 )]]> Example 2 68 12 85 8.5 Example 3 70 15 88 9.0 Example 4 72 14 90 9.2 Example 5 65 13 82 8.0 Example 6 75 16 92 9.5 Example 7 62 10 78 7.5 Example 8 78 18 95 10.0 Example 9 66 12 84 8.3 Comparative Example 1 55 8 60 5.0 Comparative Example 2 58 9 65 5.5 Comparative Example 3 50 7 55 4.5 The flame retardant properties of the above embodiments were measured, and the results are shown in Table 2 below: Table 2 Characterization of the flame retardant properties of the materials in each embodiment

Claims

1. A biomimetic gradient flame-retardant polyester material, characterized in that, It consists of a three-layer structure from the outside to the inside: an outer layer containing nano-clay and ammonium polyphosphate, a middle layer containing microencapsulated red phosphorus, and an inner layer reinforced with carbon fiber for mechanical support.

2. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 1, characterized in that, Includes the following steps: S1. Preparation of raw materials: Outer layer: By weight, it comprises 80 parts PET, 0.5 parts maleic anhydride-grafted PET, 5-10 parts nano-clay, and 5-10 parts ammonium polyphosphate. Intermediate layer: By weight, it comprises 85 parts PET, 0.5 parts maleic anhydride-grafted PET, 5-10 parts microencapsulated red phosphorus, and 5 parts polytetrafluoroethylene. Inner layer: by weight, it contains 90 parts PET, 0.5 parts maleic anhydride-grafted PET, and 5-10 parts chopped carbon fiber; S2. Preparation of gradient masterbatch: Gradient masterbatch was obtained by extrusion granulation using a three-layer co-extrusion granulator and vacuum drying at 120℃ for 4 hours. S3. Inject the gradient masterbatch into shape using a multi-layer injection molding machine; S4. Place the injection-molded preform in a hot press and hot press to form the final product.

3. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 2, characterized in that, The preparation method of the microcapsule red phosphorus in S1 is as follows: S11. Disperse red phosphorus powder in an aqueous solution containing 1 wt% polyvinyl alcohol and sonicate for 30 min; S12. Add methyl methacrylate monomer and 0.5 wt% potassium persulfate, and react at 70°C for 4 h; S13. Filter, wash and dry to obtain microcapsule red phosphorus.

4. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 3, characterized in that, The particle size of the red phosphorus powder in S11 is ≤10μm.

5. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 3, characterized in that, The mass ratio of red phosphorus powder to methyl methacrylate is 1:

3.

6. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 2, characterized in that, The short-cut carbon fiber in S1 has a length of 2-3 mm.

7. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 2, characterized in that, The extrusion granulation conditions in S2 are as follows: screw length-to-diameter ratio is 40:1; extrusion temperature is: outer layer: 250-260℃, middle layer: 245-255℃, inner layer: 255-265℃; screw speed is 200rpm.

8. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 2, characterized in that, The outer layer of S2: The thickness ratio of the intermediate layer to the inner layer is 3:(1.5-2):

5.

9. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 2, characterized in that, The injection molding conditions in S3 are: melt temperature 250-260℃, mold temperature 75-85℃, and injection pressure 80-100MPa.

10. The method for preparing the biomimetic gradient flame-retardant polyester material according to claim 2, characterized in that, The hot pressing conditions in S4 are: temperature 225-235℃, pressure 9.5-10.5MPa, holding time 10min, followed by cooling to room temperature at a rate of 20℃ / min.

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