Polyethersulfone-based graded functional integrated foamed board and its preparation method

Abstract

This invention belongs to the field of polymer foamed board technology, specifically relating to polyethersulfone-based gradient functional integrated foamed board and its preparation method. The board has an integrated three-layer structure without significant boundaries along its thickness direction, consisting of layers A, B, and C from top to bottom. Layer A is made of polyethersulfone and polyacrylonitrile-based carbon fiber; layer B is made of polyethersulfone; and layer C is made of polyethersulfone and hydrophobic fumed silica. Using three twin-screw extruders, the raw materials for layers A, B (polyethersulfone), and C are stacked in three independent channels within a multi-layer gradient distributor die and moved forward to form a composite melt with a gradient in composition and viscosity within the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity, and the mixture is then extruded through a slit-shaped die to obtain the polyethersulfone-based gradient functional integrated foamed board. This invention overcomes the problems of traditional boards having a uniform structure, single function, and difficulty in simultaneously meeting mechanical and thermal performance requirements.

Description

Technical Field

[0001] This invention belongs to the field of polymer foamed board technology, specifically relating to polyethersulfone-based gradient functional integrated foamed board and its preparation method. Background Technology

[0002] With the rapid development of aerospace, high-speed rail transportation, and high-end electronics, increasingly stringent requirements are being placed on lightweight structural-functional integrated materials used in these fields. These materials not only need to possess extremely high specific strength and specific modulus to achieve effective weight reduction, but also often need to maintain excellent thermal insulation, flame retardancy, and weather resistance properties under extreme environments such as high temperature, vibration, and corrosion.

[0003] The industry uses high-performance engineering plastics such as polyimide (PI) and polyethersulfone (PES) to prepare foamed materials. These materials inherently possess excellent properties such as high temperature resistance and intrinsic flame retardancy. To impart specific functions to the materials, existing technologies typically involve simple mechanical blending of functional fillers (such as flame retardants and conductive fillers) with the polymer matrix followed by foaming. However, the structure and properties of homogeneous foamed materials are uniform, making it difficult to simultaneously meet the different requirements of the material's surface and core in various application scenarios. For example, the surface requires high density and high hardness for wear resistance and impact resistance, while the core requires extremely low density to achieve efficient thermal insulation.

[0004] Patent CN101616967A discloses a polymer foam with nanopores and a method for producing the polymer foam with nanopores. The method includes: contacting the polymer with a foaming agent to form a homogeneous material. The homogeneous structure forces the material to compromise on performance, either with insufficient surface properties or poor thermal insulation, making it impossible to achieve "functional integration".

[0005] Patent CN109177352A discloses a high-strength thermoplastic lightweight composite board and its preparation method, including a core material, an intermediate layer disposed on both sides of the core material, and an outer layer disposed on both sides of the intermediate layer; the core material, intermediate layer, and outer layer are composited by heating and pressurizing to form a board; the core material is a foamed core material; the outer layer is a flame-retardant polymer material layer with low heat release characteristics; the intermediate layer is a fiber-reinforced high-strength flame-retardant polymer material layer; and the foamed core material is a flame-retardant foamed polymer material. This patent fuses the core material, intermediate layer, and outer layer together by hot pressing. Although the materials are all thermoplastic and can be fused, there are clear interface bonds between the different layers. When these interfaces are subjected to long-term thermal cycling, vibration, or impact, due to the inconsistency in the coefficients of thermal expansion and modulus of the materials in each layer, they are prone to become stress concentration points, leading to the risk of delamination and peeling. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a polyethersulfone-based gradient functional integrated foam board. One board can simultaneously replace the structural layer, insulation layer, and functional layer, achieving lightweight, high strength, and thermal insulation integration for long-term use in high-temperature environments. At the same time, it inherits the inherent flame retardant (UL94 V-0), low smoke, and non-toxic properties of PES, and the interlayer is gradient bonded, eliminating the risk of delamination.

[0007] This invention also provides a preparation method for it. Supercritical CO2 foaming is a green physical process. The continuous production line is highly efficient, cost-controllable, and easy to promote.

[0008] The polyethersulfone-based gradient functional integrated foamed board of the present invention has an integrated three-layer structure without significant boundaries along the thickness direction of the board, consisting of layer A, layer B and layer C from top to bottom, with a gradient transition zone between the layers where the cell morphology and density change continuously.

[0009] Layer A is made of polyethersulfone and polyacrylonitrile-based carbon fiber (CF);

[0010] Layer B is made of polyethersulfone;

[0011] Layer C is made of polyethersulfone and hydrophobic fumed silica.

[0012] The polyacrylonitrile-based carbon fibers are 80-120 μm in length and 7 μm in diameter, and their surfaces are not sized.

[0013] The method for preparing the polyethersulfone-based gradient functional integrated foamed board of the present invention comprises the following steps:

[0014] Step 1: Using a twin-screw extruder, the premix of polyethersulfone and polyacrylonitrile-based carbon fiber is extruded, water-cooled, and pelletized to obtain a polyethersulfone / polyacrylonitrile-based carbon fiber masterbatch with a polyacrylonitrile-based carbon fiber content of 18wt.%-22wt.%. The polyethersulfone / polyacrylonitrile-based carbon fiber masterbatch is then mixed with polyethersulfone again to make the polyacrylonitrile-based carbon fiber content 8wt.%-12wt.%. A second melt blending is performed using a twin-screw extruder to ensure the final uniform distribution of fibers in the matrix. The polyethersulfone / polyacrylonitrile-based carbon fiber composite material is obtained again through extrusion, water cooling, and pelletizing, which serves as the raw material for layer A.

[0015] Step 2: Using a twin-screw extruder, polyethersulfone and hydrophobic fumed silica are premixed. Through extrusion, water cooling, and pelletizing processes, a polyethersulfone / hydrophobic fumed silica composite material with a hydrophobic fumed silica content of 1wt.%-3wt.% is obtained as the C-layer raw material.

[0016] Step 3: Using three twin-screw extruders, pass the A-layer material, B-layer material (polyethersulfone), and C-layer material through a multi-layer gradient distributor die. A schematic diagram of the multi-layer gradient distributor die is shown below. Figure 1 As shown, the multi-layer gradient distributor die head consists of three parallel independent flow channels along the raw material movement direction, a fused composite melt cavity, and a slit-shaped die. The three melt streams overlap in the three independent flow channels within the multi-layer gradient distributor die head at their respective flow rates and temperatures, and continue to move forward under shear and diffusion effects to form a composite melt with gradient composition and viscosity within the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt, and then extruded through a slit-shaped die to obtain a polyethersulfone-based gradient functional integrated foamed board.

[0017] When each layer of melt passes through the slit-shaped die, the differences in viscosity and solubility of supercritical fluid (SCF) between the layers of melt are utilized to achieve simultaneous but different foaming rates, thereby spontaneously forming a preset gradient cell structure.

[0018] Layer A, a high-density microporous structure, is located on one side of the board surface. Polyacrylonitrile-based carbon fiber (CF) prevents microcrack propagation, forcing them to change direction, consuming more energy, and improving toughness. Simultaneously, it provides numerous nucleation sites, significantly refining the pores. The finer pore structure reduces stress concentration, thereby increasing strength. Layer B is a transitional support layer, situated between layers A and C. The pore size and density exhibit a continuous gradient. From the side closer to layer A to the side closer to layer C, it achieves a smooth transition in mechanical properties, effectively transferring and dispersing stress, preventing interlayer delamination, and serving as the primary load-bearing structure. Layer C is a lightweight thermal insulation core layer. Nano-SiO2 itself is an excellent thermal insulation material, effectively scattering phonons (the main carriers of heat conduction). Doped into the pore walls, it further reduces the thermal conductivity of the foam. Simultaneously, SiO2 promotes the formation of a more stable and denser char layer during combustion, acting as a physical barrier, slowing heat and mass transfer, and improving flame retardant performance.

[0019] The twin-screw extruder described in step one is set to the following temperatures for each section: feeding zone 270-290℃, melting zone 300-320℃, mixing zone 310-330℃, and die head zone 310-330℃. Polyethersulfone is added through the main feed port, and polyacrylonitrile-based carbon fiber is added through the side feeder in the middle section of the melting zone. The screw speed of the twin-screw extruder described in step one is 200-300 rpm.

[0020] The secondary melt blending temperature in step one is 320-330℃.

[0021] After the polyethersulfone, polyacrylonitrile-based carbon fiber, and hydrophobic fumed silica described in steps one, two, and three are dried and dehydrated, they are then fed into a twin-screw extruder.

[0022] In step one, the polyacrylonitrile-based carbon fiber needs to be dried in a vacuum oven at 120°C for at least 8 hours to completely remove moisture.

[0023] In step two, the PES must be dried in a vacuum or air-circulating oven at 120-140℃ for 4-6 hours to remove moisture from the particles.

[0024] The hydrophobic fumed silica described in step two is dried at 80-100℃ for 2-4 hours to remove adsorbed water and improve compatibility.

[0025] The twin-screw extruder described in step two has the following temperature settings: feeding zone 270-290℃, melting zone 300-320℃, mixing zone 310-330℃, and die head zone 310-330℃. The screw speed of the twin-screw extruder described in step two is 250-400 rpm.

[0026] The three independent flow channels in the multi-layer gradient distributor head described in step three gradually become the required thickness after they merge at the confluence point, pre-compressing and accelerating the melt to ensure a smooth transition.

[0027] The parameter settings for the three twin-screw extruders mentioned in step three are as follows: Layer A: Feeding zone: 290-310℃, Compression zone: 310-330℃, Die head zone: 330-335℃; Layer B: Feeding zone: 290-300℃, Compression zone: 310-320℃, Die head zone: 325-330℃; Layer C: Feeding zone: 290-310℃, Compression zone: 310-330℃, Die head zone: 320-340℃.

[0028] The temperature of the multi-layer gradient distributor head described in step three is 325-330℃ to balance the flowability of each layer.

[0029] The supercritical CO2 injection pressure in step three is 10-20 MPa, and the injection temperature is 310-330℃.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) The plate of the present invention has an integrated three-layer structure without significant boundaries along the thickness direction. The layers are combined through a gradient transition zone, which avoids the stress concentration and delamination risk caused by the clear interface of traditional multilayer materials, and improves the long-term reliability of the material under extreme environments such as high temperature and vibration.

[0032] (2) The A layer of the board described in this invention is made of polyacrylonitrile-based carbon fiber, which gives the surface high strength, high toughness and wear resistance; the B layer is made of pure polyethersulfone as a transition support layer to achieve a smooth transfer of mechanical properties; the C layer is made of hydrophobic fumed silica, which significantly improves the thermal insulation and flame retardant properties. A single board meets the structural, thermal insulation and functional requirements at the same time, realizing the integration of lightweight, high strength and thermal insulation.

[0033] (3) The present invention adopts supercritical CO2 foaming technology, which is a physical foaming process with no chemical residue and is environmentally friendly; the continuous production line is highly efficient and cost-controllable, which is conducive to large-scale promotion.

[0034] (4) The sheet material of the present invention inherits the inherent flame retardancy (UL94 V-0), low smoke and non-toxicity, and high temperature resistance of polyethersulfone. At the same time, through the optimization of gradient cell structure and functional filler, the thermal insulation, mechanical and durability properties are further improved, making it suitable for aerospace, high-speed rail transportation, high-end electronic appliances and other fields. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a multi-layer gradient distributor head. Detailed Implementation

[0036] The present invention will be further described below with reference to the embodiments.

[0037] Unless otherwise specified, all raw materials used in the examples were commercially available.

[0038] Polyethersulfone: BASF E3010 injection molding grade;

[0039] Polyacrylonitrile-based carbon fiber: Hangzhou Gaoke Composite Materials Co., Ltd. CFP-200, polyacrylonitrile-based carbon fiber with a length of 80-120μm (200 mesh) and a diameter of 7μm;

[0040] Hydrophobic fumed silica: HB-139 from Hubei Huifu Nanomaterials Co., Ltd.

[0041] Example 1

[0042] The preparation method of the polyethersulfone-based gradient functional integrated foamed board comprises the following steps:

[0043] Step 1: Dry polyacrylonitrile-based carbon fibers in a vacuum oven at 120℃ for 8 hours to remove moisture. Use a twin-screw extruder with the following temperatures set: feeding zone 270℃, melting zone 300℃, mixing zone 310℃, and die head zone 310℃. After drying PES in a vacuum oven at 130℃ for 6 hours, add it through the main feed port. After drying polyacrylonitrile-based carbon fibers in a vacuum oven at 120℃ for 8 hours, add them through a side feeder in the middle of the melting zone. The screw speed is 300 rpm. Through extrusion, water cooling, and pelletizing, obtain a PES / CF mixture with a polyacrylonitrile-based carbon fiber content of 18 wt.%. Perform a secondary melt blend at 320℃, and through extrusion, water cooling, and pelletizing, obtain a PES / CF mixture with a polyacrylonitrile-based carbon fiber content of 8 wt.% as layer A.

[0044] Step 2: Dry the PES in a vacuum oven at 130℃ for 6 hours to remove moisture from the particles. Then, dry the hydrophobic fumed silica at 90℃ for 4 hours to remove adsorbed water. The twin-screw extruder is set to the following temperatures: feeding zone 270℃, melting zone 300℃, mixing zone 310℃, die head zone 310℃, and screw speed 250 rpm. After water cooling and pelletizing, a PES / SiO2 composite material with a SiO2 content of 1 wt.% is obtained as the C layer.

[0045] Step 3: The parameters for the three twin-screw extruders are set as follows: Layer A: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 330℃. Layer B: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 325℃. Layer C: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 320℃. The raw materials for Layer A, Layer B (polyethersulfone), and Layer C pass through a multi-layer gradient distributor die. A schematic diagram of the multi-layer gradient distributor die is shown below. Figure 1 As shown, the multi-layer gradient distributor die head consists of three parallel independent flow channels, a fused composite melt cavity, and a slit-shaped die along the raw material movement direction. The three melt streams overlap in the three independent flow channels within the multi-layer gradient distributor die head and continue to move forward under shearing and diffusion, forming a composite melt with gradient composition and viscosity within the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt. The die head temperature is set at 325°C, the supercritical CO2 injection pressure is 10MPa, and the injection temperature is 310°C. The product is then extruded through a slit-shaped die to obtain a polyethersulfone-based gradient functional integrated foamed board.

[0046] Example 2

[0047] The preparation method of the polyethersulfone-based gradient functional integrated foamed board comprises the following steps:

[0048] Step 1: Dry polyacrylonitrile-based carbon fiber in a vacuum oven at 120℃ for 8 hours to remove moisture. Use a twin-screw extruder and set the temperatures of each section as follows: feeding zone 290℃, melting zone 320℃, mixing zone 330℃, and die head zone 330℃. After drying PES in a vacuum oven at 130℃ for 6 hours, add it through the main feed port. After drying polyacrylonitrile-based carbon fiber in a vacuum oven at 120℃ for 8 hours, add it through a side feeder in the middle of the melting zone. The screw speed is 300 rpm. Through extrusion, water cooling, and pelletizing, obtain a PES / CF with a fiber content of 22 wt.%. Perform a secondary melt blend at 330℃, and through extrusion, water cooling, and pelletizing, obtain a PES / CF with a fiber content of 12 wt.% as layer A.

[0049] Step 2: Dry the PES in a vacuum oven at 130℃ for 6 hours to remove moisture from the particles. Then, dry the hydrophobic fumed silica at 90℃ for 4 hours to remove adsorbed water. The twin-screw extruder is set to the following temperatures: feeding zone 290℃, melting zone 320℃, mixing zone 330℃, die head zone 330℃, and screw speed 400 rpm. After water cooling and pelletizing, a PES / SiO2 composite material with a SiO2 content of 2 wt.% is obtained as the C layer.

[0050] Step 3: The parameters for the three twin-screw extruders are set as follows: Layer A: Feeding zone: 310℃, Compression zone: 330℃, Die head zone: 335℃. Layer B: Feeding zone: 300℃, Compression zone: 320℃, Die head zone: 330℃. Layer C: Feeding zone: 310℃, Compression zone: 330℃, Die head zone: 340℃. The raw materials for Layer A, Layer B (polyethersulfone), and Layer C pass through a multi-layer gradient distributor die. A schematic diagram of the multi-layer gradient distributor die is shown below. Figure 1 As shown, the multi-layer gradient distributor die head consists of three parallel independent flow channels along the raw material movement direction, a fused composite melt cavity, and a slit-shaped die. The three melt streams overlap in the three independent flow channels within the multi-layer gradient distributor die head and continue to move forward under shearing and diffusion, forming a composite melt with gradient composition and viscosity within the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt. The die head temperature is set at 330°C, the supercritical CO2 injection pressure is 20MPa, and the injection temperature is 330°C. The product is then extruded through a slit-shaped die to obtain a polyethersulfone-based gradient functional integrated foamed board.

[0051] Example 3

[0052] The preparation method of the polyethersulfone-based gradient functional integrated foamed board comprises the following steps:

[0053] Step 1: Dry polyacrylonitrile-based carbon fiber in a vacuum oven at 120℃ for 8 hours to remove moisture. Use a twin-screw extruder and set the temperatures of each section as follows: feeding zone 280℃, melting zone 310℃, mixing zone 320℃, and die head zone 320℃. After drying PES in a vacuum oven at 130℃ for 6 hours, add it through the main feed port. After drying polyacrylonitrile-based carbon fiber in a vacuum oven at 120℃ for 8 hours, add it through a side feeder in the middle of the melting zone. The screw speed is 300 rpm. Through extrusion, water cooling, and pelletizing, obtain a PES / CF with a fiber content of 20 wt.%. Perform a secondary melt blend at 320℃, and through extrusion, water cooling, and pelletizing, obtain a PES / CF with a fiber content of 10 wt.% as layer A.

[0054] Step 2: Dry the PES in a vacuum oven at 130℃ for 6 hours to remove moisture from the particles. Then, dry the hydrophobic fumed silica at 90℃ for 4 hours to remove adsorbed water. The twin-screw extruder is set to the following temperatures: feeding zone 280℃, melting zone 310℃, mixing zone 320℃, die head zone 320℃, and screw speed 350 rpm. After water cooling and pelletizing, a PES / SiO2 composite material with a SiO2 content of 1 wt.% is obtained as the C layer.

[0055] Step 3: The parameters for the three twin-screw extruders are set as follows: Layer A: Feeding zone: 300℃, Compression zone: 320℃, Die head zone: 330℃. Layer B: Feeding zone: 295℃, Compression zone: 315℃, Die head zone: 325℃. Layer C: Feeding zone: 300℃, Compression zone: 320℃, Die head zone: 330℃. The raw materials for Layer A, Layer B (polyethersulfone), and Layer C pass through a multi-layer gradient distributor die. A schematic diagram of the multi-layer gradient distributor die is shown below. Figure 1 As shown, the multi-layer gradient distributor die head consists of three parallel independent flow channels along the raw material movement direction, a fused composite melt cavity, and a slit-shaped die. The three melt streams overlap in the three independent flow channels within the multi-layer gradient distributor die head and continue to move forward under shearing and diffusion effects, forming a composite melt with gradient composition and viscosity within the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt. The die head temperature is set at 328°C, the supercritical CO2 injection pressure is 15MPa, and the injection temperature is 320°C. The product is then extruded through a slit-shaped die to obtain a polyethersulfone-based gradient functional integrated foamed board.

[0056] Example 4

[0057] The preparation method of the polyethersulfone-based gradient functional integrated foamed board comprises the following steps:

[0058] Step 1: Dry polyacrylonitrile-based carbon fiber in a vacuum oven at 120℃ for 8 hours to remove moisture. Use a twin-screw extruder and set the temperatures of each section as follows: feeding zone 280℃, melting zone 310℃, mixing zone 320℃, and die head zone 320℃. After drying PES in a vacuum oven at 130℃ for 6 hours, add it through the main feed port. After drying polyacrylonitrile-based carbon fiber in a vacuum oven at 120℃ for 8 hours, add it through a side feeder in the middle of the melting zone. The screw speed is 300 rpm. Through extrusion, water cooling, and pelletizing, obtain a PES / CF with a fiber content of 20 wt.%. Perform a secondary melt blend at 320℃, and through extrusion, water cooling, and pelletizing, obtain a PES / CF with a fiber content of 10 wt.% as layer A.

[0059] Step 2: Dry the PES in a vacuum oven at 130℃ for 6 hours to remove moisture from the particles, and dry the SiO2 at 90℃ for 4 hours to remove adsorbed water. The twin-screw extruder is set with the following temperatures for each section: feeding zone 280℃, melting zone 310℃, mixing zone 320℃, and die head zone 320℃, with a screw speed of 400 rpm. After water cooling and pelletizing, a composite material of PES / SiO2 with a SiO2 content of 3 wt.% is obtained as the C layer.

[0060] Step 3: The parameters for the three twin-screw extruders are set as follows: Layer A: Feeding zone: 300℃, Compression zone: 320℃, Die head zone: 330℃. Layer B: Feeding zone: 295℃, Compression zone: 315℃, Die head zone: 325℃. Layer C: Feeding zone: 300℃, Compression zone: 320℃, Die head zone: 330℃. The raw materials for Layer A, Layer B (polyethersulfone), and Layer C pass through a multi-layer gradient distributor die. A schematic diagram of the multi-layer gradient distributor die is shown below. Figure 1 As shown, the multi-layer gradient distributor die head consists of three parallel independent flow channels along the raw material movement direction, a fused composite melt cavity, and a slit-shaped die. The three melt streams overlap in the three independent flow channels within the multi-layer gradient distributor die head and continue to move forward under shearing and diffusion, forming a composite melt with gradient composition and viscosity within the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt. The die head temperature is set at 328°C, the supercritical CO2 injection pressure is 15MPa, and the injection temperature is 320°C. The product is then extruded through a slit-shaped die to obtain a polyethersulfone-based gradient functional integrated foamed board.

[0061] Comparative Example 1

[0062] PES was dried in a vacuum oven at 130℃ for 6 hours to remove moisture from the granules, serving as the same raw material for layers A, B, and C. The parameters for the three extruders were set as follows: Layer A: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 330℃; Layer B: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 325℃; Layer C: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 320℃. The raw materials from layers A, B, and C were passed through a multi-layer gradient distributor die. A schematic diagram of the multi-layer gradient distributor die is shown below. Figure 1 As shown, the die head temperature is set to 325℃, the supercritical CO2 injection pressure is 10MPa, and the injection temperature is 310℃, producing gradient foamed boards.

[0063] Comparative Example 2

[0064] The preparation method of the polyethersulfone-based gradient functional integrated foamed board comprises the following steps:

[0065] Step 1: Dry polyacrylonitrile-based carbon fibers in a vacuum oven at 120℃ for 8 hours to remove moisture. Use a twin-screw extruder with the following temperatures set: feeding zone 270℃, melting zone 300℃, mixing zone 310℃, and die head zone 310℃. After drying PES in a vacuum oven at 130℃ for 6 hours, add it through the main feed port. After drying polyacrylonitrile-based carbon fibers in a vacuum oven at 120℃ for 8 hours, add them through a side feeder in the middle of the melting zone. The screw speed is 300 rpm. Through extrusion, water cooling, and pelletizing, obtain a PES / CF with a polyacrylonitrile-based carbon fiber content of 18 wt.%. Perform a secondary melt blend at 320℃, and through extrusion, water cooling, and pelletizing, obtain a PES / CF with a fiber content of 8 wt.% as layer A.

[0066] Step 2: Dry the PES in a vacuum oven at 130℃ for 6 hours to remove moisture from the particles. Then, dry the hydrophobic fumed silica at 90℃ for 4 hours to remove adsorbed water. The twin-screw extruder is set to the following temperatures: feeding zone 270℃, melting zone 300℃, mixing zone 310℃, die head zone 310℃, and screw speed 250 rpm. After water cooling and pelletizing, a PES / SiO2 composite material with a SiO2 content of 1 wt.% is obtained as the C layer.

[0067] Step 3: Set the parameters for the three twin-screw extruders as follows: Layer A: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 330℃. Layer B: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 325℃. Layer C: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 320℃. Layer A and Layer B materials: polyethersulfone and Layer C materials are passed through a non-specially designed blending die (i.e., without three parallel independent flow channels). The size and dimensions of the blending die are the same as in Example 1. The connection between the blending die and the slit-shaped die is the same as in Example 1. The blending die, along the direction of material movement, consists of a blending flow channel, a fused composite melt cavity, and a slit-shaped die. The three melt layers are mixed in the blending die and continue to move forward under shear and diffusion to form a composite melt in the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt. The die temperature is set at 325°C, the supercritical CO2 injection pressure is 10MPa, and the injection temperature is 310°C. The material is then extruded through a slit-shaped die to obtain the foamed board.

[0068] Comparative Example 3

[0069] The preparation method of the polyethersulfone-based gradient functional integrated foamed board comprises the following steps:

[0070] Step 1: Dry the PES in a vacuum oven at 130°C for 6 hours to remove moisture from the particles, forming layers A and B.

[0071] Step 2: Dry the PES in a vacuum oven at 130℃ for 6 hours to remove moisture from the particles. Then, dry the hydrophobic fumed silica at 90℃ for 4 hours to remove adsorbed water. The twin-screw extruder is set with the following temperatures for each section: feeding zone 270℃, melting zone 300℃, mixing zone 300℃, and die head zone 310℃. The screw speed is 250 rpm. After water cooling and pelletizing, a PES / SiO2 composite material with a SiO2 content of 1 wt.% is obtained as the C layer.

[0072] Step 3: The parameters for the three twin-screw extruders are set as follows: Layer A: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 330℃. Layer B: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 325℃. Layer C: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 320℃. The raw materials from layers A, B, and C pass through a multi-layer gradient distributor die. A schematic diagram of the multi-layer gradient distributor die is shown below. Figure 1As shown, the multi-layer gradient distributor die head consists of three parallel independent flow channels, a fused composite melt cavity, and a slit-shaped die along the raw material movement direction. The three melt streams overlap in the three independent flow channels within the multi-layer gradient distributor die head and continue to move forward under shearing and diffusion, forming a composite melt with gradient composition and viscosity within the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt. The die head temperature is set at 325°C, the supercritical CO2 injection pressure is 10MPa, and the injection temperature is 310°C. The product is then extruded through a slit-shaped die to obtain a polyethersulfone-based gradient functional integrated foamed board.

[0073] Comparative Example 4

[0074] The preparation method of the polyethersulfone-based gradient functional integrated foamed board comprises the following steps:

[0075] Step 1: Dry polyacrylonitrile-based carbon fibers in a vacuum oven at 120℃ for 8 hours to remove moisture. Use a twin-screw extruder with the following temperatures set: feeding zone 270℃, melting zone 300℃, mixing zone 310℃, and die head zone 310℃. After drying PES in a vacuum oven at 130℃ for 6 hours, add it through the main feed port. After drying polyacrylonitrile-based carbon fibers in a vacuum oven at 120℃ for 8 hours, add them through a side feeder in the middle of the melting zone. The screw speed is 300 rpm. Through extrusion, water cooling, and pelletizing, obtain a PES / CF with a polyacrylonitrile-based carbon fiber content of 18 wt.%. Perform a secondary melt blend at 320℃, and through extrusion, water cooling, and pelletizing, obtain a PES / CF with a fiber content of 8 wt.% as layer A.

[0076] Step 2: Dry the PES in a vacuum oven at 130°C for 6 hours to remove moisture from the particles, which will form layers B and C.

[0077] Step 3: The parameters for the three twin-screw extruders are set as follows: Layer A: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 330℃. Layer B: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 325℃. Layer C: Feeding zone: 290℃, Compression zone: 310℃, Die head zone: 320℃. The raw materials from layers A, B, and C pass through a multi-layer gradient distributor die. A schematic diagram of the multi-layer gradient distributor die is shown below. Figure 1As shown, the multi-layer gradient distributor die head consists of three parallel independent flow channels, a fused composite melt cavity, and a slit-shaped die along the raw material movement direction. The three melt streams overlap in the three independent flow channels within the multi-layer gradient distributor die head and continue to move forward under shearing and diffusion, forming a composite melt with gradient composition and viscosity within the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt. The die head temperature is set at 325°C, the supercritical CO2 injection pressure is 10MPa, and the injection temperature is 310°C. The product is then extruded through a slit-shaped die to obtain a polyethersulfone-based gradient functional integrated foamed board.

[0078] Product strength and thermal conductivity tests:

[0079] The foamed boards prepared in Examples 1-4 and Comparative Examples 1-4 were cut for different performance tests. The tests included board density, compressive strength, and thermal conductivity. The density was tested according to GB / T6343-2009, the compressive strength according to GB / T 8813-2020, and the thermal conductivity according to GB / T10297-2015. The data are shown in Table 1 below:

[0080] Table 1 Test data of sample compressive strength and thermal conductivity

[0081]

[0082] The foamed boards prepared in Examples 1-4 and Comparative Examples 1-4 were cut and their density in different regions was tested. The data are shown in Table 2 below.

[0083] Table 2. Density test data of each layer of the sample.

[0084]

[0085] The board obtained in Comparative Example 2 has no layered structure after being cut.

[0086] Based on the above data, it can be seen that the polyethersulfone (PES)-based gradient functional integrated foamed board prepared by this invention has significantly superior performance in terms of foam mechanical strength and heat resistance. Its lightweight, high-strength, and heat-insulating integrated functional characteristics have profound research significance for aerospace, high-speed rail transportation, high-end electronic appliances and other fields.

Claims

1. A polyethersulfone-based gradient functional integrated foamed board, characterized in that, The integrated three-layer structure has no significant boundaries along the thickness direction of the plate, consisting of layer A, layer B and layer C from top to bottom; Layer A is made of polyethersulfone and polyacrylonitrile-based carbon fiber; Layer B is made of polyethersulfone; Layer C is made of polyethersulfone and hydrophobic fumed silica; The preparation method of the polyethersulfone-based gradient functional integrated foamed board comprises the following steps: Step 1: Using a twin-screw extruder, the dried and dehydrated polyethersulfone and polyacrylonitrile-based carbon fiber premix is ​​extruded, water-cooled, and pelletized to obtain a polyethersulfone / polyacrylonitrile-based carbon fiber masterbatch with a polyacrylonitrile-based carbon fiber content of 18wt.%-22wt.%. The polyethersulfone / polyacrylonitrile-based carbon fiber masterbatch is then mixed with polyethersulfone again to make the polyacrylonitrile-based carbon fiber content 8wt.%-12wt.%. A second melt blending is performed using a twin-screw extruder, and the polyethersulfone / polyacrylonitrile-based carbon fiber composite is obtained again through extrusion, water cooling, and pelletizing, which serves as the raw material for layer A. Step 2: Using a twin-screw extruder, premix the dried and dehydrated polyethersulfone with hydrophobic fumed silica. Through extrusion, water cooling, and pelletizing processes, a polyethersulfone / hydrophobic fumed silica composite material with a hydrophobic fumed silica content of 1wt.%-3wt.% is obtained as the C-layer raw material. Step 3: Using three twin-screw extruders, the dried and dehydrated A-layer raw material, B-layer raw material (polyethersulfone), and C-layer raw material are passed through a multi-layer gradient distributor die. The multi-layer gradient distributor die consists of three parallel independent flow channels, a fused composite melt cavity, and a slit-shaped die along the direction of raw material movement. Three melts are superimposed in three independent channels within the multi-layer gradient distributor die head, and continue to move forward under shearing and diffusion to form a composite melt with gradient composition and viscosity in the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt, and then extruded through a slit die to obtain polyethersulfone-based gradient functional integrated foamed board. The parameter settings for the three twin-screw extruders mentioned in step three are as follows: Layer A: Feeding zone: 290-310℃, Compression zone: 310-330℃, Die head zone: 330-335℃; Layer B: Feeding zone: 290-300℃, Compression zone: 310-320℃, Die head zone: 325-330℃; Layer C: Feeding zone: 290-310℃, Compression zone: 310-330℃, Die head zone: 320-340℃. The polyacrylonitrile-based carbon fiber has a length of 80-120 μm; The temperature of the multi-layer gradient distributor head described in step three is 325-330℃; The supercritical CO2 injection pressure in step three is 10-20 MPa, and the injection temperature is 310-330℃.

2. The polyethersulfone-based gradient functional integrated foamed board according to claim 1, characterized in that, The polyacrylonitrile-based carbon fibers have a diameter of 7 μm and their surface is not sized.

3. A method for preparing a polyethersulfone-based gradient functional integrated foamed board according to any one of claims 1 to 2, characterized in that, It is prepared by the following steps: Step 1: Using a twin-screw extruder, the dried and dehydrated polyethersulfone and polyacrylonitrile-based carbon fiber premix is ​​extruded, water-cooled, and pelletized to obtain a polyethersulfone / polyacrylonitrile-based carbon fiber masterbatch with a polyacrylonitrile-based carbon fiber content of 18wt.%-22wt.%. The polyethersulfone / polyacrylonitrile-based carbon fiber masterbatch is then mixed with polyethersulfone again to make the polyacrylonitrile-based carbon fiber content 8wt.%-12wt.%. A second melt blending is performed using a twin-screw extruder, and the polyethersulfone / polyacrylonitrile-based carbon fiber composite is obtained again through extrusion, water cooling, and pelletizing, which serves as the raw material for layer A. Step 2: Using a twin-screw extruder, premix the dried and dehydrated polyethersulfone with hydrophobic fumed silica. Through extrusion, water cooling, and pelletizing processes, a polyethersulfone / hydrophobic fumed silica composite material with a hydrophobic fumed silica content of 1wt.%-3wt.% is obtained as the C-layer raw material. Step 3: Using three twin-screw extruders, the dried and dehydrated A-layer raw material, B-layer raw material (polyethersulfone), and C-layer raw material are passed through a multi-layer gradient distributor die. The multi-layer gradient distributor die consists of three parallel independent flow channels, a fused composite melt cavity, and a slit-shaped die along the direction of raw material movement. Three melt streams are superimposed in three independent channels within the multi-layer gradient distributor die head, and continue to move forward under shearing and diffusion to form a composite melt with gradient composition and viscosity in the composite melt cavity. Supercritical CO2 is injected into the composite melt cavity to dissolve it uniformly in the composite melt, and then extruded through a slit-shaped die to obtain a polyethersulfone-based gradient functional integrated foam board.

4. The method for preparing polyethersulfone-based gradient functional integrated foamed board according to claim 3, characterized in that, In step one, the temperature of each section of the twin-screw extruder is set as follows: feeding zone 270-290℃, melting zone 300-320℃, mixing zone 310-330℃, and die head zone 310-330℃. Polyethersulfone is added from the main feed port, and polyacrylonitrile-based carbon fiber is added in the middle section of the melting zone through the side feeder.

5. The method for preparing polyethersulfone-based gradient functional integrated foamed board according to claim 3, characterized in that, The secondary melt blending temperature in step one is 320-330℃.

6. The method for preparing polyethersulfone-based gradient functional integrated foamed board according to claim 3, characterized in that, After the polyethersulfone, polyacrylonitrile-based carbon fiber, and hydrophobic fumed silica described in steps one, two, and three are dried and dehydrated, they are then fed into a twin-screw extruder.

7. The method for preparing polyethersulfone-based gradient functional integrated foamed board according to claim 3, characterized in that, The twin-screw extruder described in step two has the following temperature settings: feeding zone 270-290℃, melting zone 300-320℃, mixing zone 310-330℃, and die head zone 310-330℃. The screw speed of the twin-screw extruder described in step two is 250-400 rpm.

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