Polyethylene fiber aerogel and its preparation process

Abstract

The present invention provides a polyethylene fiber aerogel and a method for preparing the same. The preparation method comprises: preheating: heating and melting high-density polyethylene to obtain a polyethylene melt; electrospinning: electrospinning the polyethylene melt and freeze-drying the resulting polyethylene fibers to obtain a polyethylene fiber aerogel precursor; and heat treatment: heat-treating the polyethylene fiber aerogel precursor to melt-weld the fibers to obtain the polyethylene fiber aerogel. The polyethylene fiber aerogel has a high specific surface area and elastic modulus, providing a wider range of applications for polyethylene.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer aerogels, and in particular to a polyethylene fiber aerogel and a preparation method thereof. Background Art

[0002] High-density polyethylene (HDPE) materials, due to their resistance to acids, alkalis, organic solvents, and excellent insulation, maintain a certain degree of toughness even at low temperatures. Their mechanical strengths, including surface hardness, tensile strength, and rigidity, are higher than those of low-density polyethylene (LDPE) and closer to those of polypropylene (PP). Their nanofiber structure offers a wide range of application possibilities. Polyethylene fiber aerogels, with their ultra-lightweight properties, high elastic modulus, high porosity, and large specific surface area, hold promise for applications in ultra-light elastic filling materials, catalytic supports, and sound-absorbing materials.

[0003] CN104032381A discloses an electrospinning method for preparing a hyperbranched polyethylene material. However, the preparation conditions of the hyperbranched polyethylene material are harsh, the material is scarce and the cost is high, which is not conducive to the promotion and application of polyethylene products.

[0004] CN110184664A discloses a method for preparing ultra-high molecular weight polyethylene fibers. Ultra-high molecular weight polyethylene powder is melted, passed through a spinneret, drawn, and cooled to form gel fibers. The gel fibers are then sequentially extracted, dried, and heat-stretched to obtain the ultra-high molecular weight polyethylene fibers. This method, through melt spinning followed by heat stretching, produces high-strength polyethylene fibers, which are single fibers and do not have an aerogel structure. The single fibers produced in this patent have a diameter of 70 mm, a very low specific surface area, and a high density. This product primarily emphasizes its high-strength mechanical properties, making it difficult to apply in the field of ultra-lightweight, high-specific surface area, and elastic aerogels. Therefore, developing a polyethylene fiber aerogel with a simple and rapid process, a high specific surface area, and an elastic, ultra-lightweight aerogel structure is of great significance and practical value. Summary of the Invention

[0005] In order to solve at least one of the above problems, the present invention provides a polyethylene fiber aerogel and a preparation method thereof.

[0006] The present invention is made by the inventor based on the following cognition:

[0007] Compared to existing polyethylene fiber materials, polyethylene nanofiber aerogels have advantages such as high specific surface area, ultra-lightness, high elastic modulus, and high porosity. This nanostructured aerogel offers more application possibilities for polyethylene. The polyethylene fiber aerogel structure obtained by the currently reported preparation process has low porosity, poor elastic modulus, and low specific surface area, which limits the widespread application of aerogels. For this reason, the inventors first heat and melt high-density polyethylene to obtain a polyethylene melt; then electrospin the polyethylene melt, and freeze-dry the polyethylene fibers obtained by spinning to obtain a polyethylene fiber aerogel precursor; finally, heat-treat the polyethylene fiber aerogel precursor to transform the fibers from "overlapping" to "melt welding", resulting in a flexible, self-supporting polyethylene fiber aerogel with a high specific surface area and high elastic modulus.

[0008] Specifically, the present invention provides the following technical solutions:

[0009] In one aspect, the present invention provides a polyethylene fiber aerogel, wherein the diameter of the nanofiber inside the aerogel is 50-1000 nm; the elastic modulus of the aerogel is 30-120 MPa; the specific surface area of ​​the aerogel is 389-1068 m 2 / g.

[0010] According to some embodiments of the present invention, the diameter of the nanofibers inside the aerogel is 50-130 nm.

[0011] According to other embodiments of the present invention, the diameter of the nanofibers inside the aerogel is 400-1000 nm.

[0012] In the present invention, the diameter of the nanofibers inside the aerogel may also be 130-400 nm.

[0013] According to some embodiments of the present invention, the polyethylene fiber aerogel has an elastic modulus of 30-60 MPa.

[0014] According to some other embodiments of the present invention, the elastic modulus of the polyethylene fiber aerogel is 60-120 MPa. According to some embodiments of the present invention, the specific surface area of ​​the polyethylene fiber aerogel is 389-650 m 2 / g.

[0015] According to some other embodiments of the present invention, the polyethylene fiber aerogel has a specific surface area of ​​890-1068m 2 / g.

[0016] In the present invention, the specific surface area of ​​the polyethylene fiber aerogel can also be 650-890m 2 / g.

[0017] In another aspect, the present invention provides a method for preparing the polyethylene fiber aerogel, comprising:

[0018] Preheating: heating and melting high-density polyethylene to obtain polyethylene melt;

[0019] Electrospinning: The polyethylene melt is electrospun, and the spun polyethylene fibers are freeze-dried to obtain a polyethylene fiber aerogel precursor;

[0020] Heat treatment: The polyethylene fiber aerogel precursor is heat treated to melt and weld the fibers to obtain the polyethylene fiber aerogel.

[0021] Specifically, the polyethylene fiber aerogel precursor fibers obtained by electrospinning are only in overlapping contact with each other. After heat treatment, the fibers change from "overlapping" to "melt welding".

[0022] According to some embodiments of the present invention, the high-density polyethylene is heated and melted at a temperature of 300-500°C, for example, 300°C, 350°C, 400°C, 450°C, 500°C, and the like.

[0023] According to some embodiments of the present invention, during the electrospinning, the positive voltage is 10-50 kV, for example: 10 kV, 15 kV, 20 kV, 25 kV, 30 kV, 35 kV, 40 kV, 45 kV, 50 kV, and the like.

[0024] In some embodiments, during the electrospinning, the positive voltage is 20-50 kV.

[0025] According to some embodiments of the present invention, during the electrospinning, the spinning distance is 10-30 cm, for example, 10 cm, 12 cm, 15 cm, 18 cm, 20 cm, 22 cm, 25 cm, 28 cm, 30 cm, and the like.

[0026] In some embodiments, during the electrospinning, the spinning distance is 20 cm.

[0027] According to some embodiments of the present invention, during the electrospinning, the melt extrusion rate is 1-5 mL / h, for example: 1 mL / h, 2 mL / h, 3 mL / h, 4 mL / h, 5 mL / h, and the like.

[0028] Melt temperature, spinning voltage, and solution extrusion rate are three primary factors that influence the diameter of nanofibers, and thus the density of the aerogel. Furnace temperature determines melt viscosity and is the primary determinant of diameter. Higher furnace temperatures increase melt fluidity and result in finer fiber diameters. Spinning voltage and melt extrusion rate also have a certain influence on diameter: higher voltage and lower extrusion rates result in finer fiber diameters. Under these defined parameters, a good balance of polyethylene fiber properties can be achieved, yielding polyethylene fiber aerogels with excellent overall performance.

[0029] According to some embodiments of the present invention, the freeze-drying is performed in a liquid nitrogen tank, and the liquid nitrogen tank is placed on the ground.

[0030] The polyethylene fiber aerogel precursor is heat-treated to obtain polyethylene fiber aerogel, in which the fibers are "welded" instead of "overlapped", and the overall aerogel is in a fluffy, elastic and self-supporting state.

[0031] According to some embodiments of the present invention, the heat treatment temperature is 60-120°C, for example: 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, and the like.

[0032] In some embodiments, the heat treatment temperature is 60-90°C.

[0033] In other embodiments, the heat treatment temperature is 90-120°C.

[0034] According to some embodiments of the present invention, the heat treatment time is 1-5 hours, for example: 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, and the like.

[0035] The heat treatment temperature affects the bonding method between fibers. Normally, the bonding method between fibers without heat treatment is overlap. After heat treatment, the bonding between fibers changes from overlap to fusion welding, making the structure more stable and the application range wider.

[0036] The polyethylene fiber aerogel obtained by the above preparation method is particularly suitable for use as a catalytic carrier, an ultra-light elastic filling material and a sound-absorbing material.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) Polyethylene nanofibers were obtained by melt electrospinning technology and freeze-dried to form aerogels. Finally, through heat treatment, the connection between the fibers was changed from "lap joint" to "melt welding", which enhanced the mechanical stability of the material.

[0039] (2) The traditional aerogel preparation method uses other processes such as catalyst reaction or gas reaction to obtain porous aerogel using the pores remaining from the reaction. The present invention changes the traditional method by bridging fibers into a three-dimensional network structure, thereby constructing a large number of pore structures, and enhancing the mechanical properties of the aerogel through subsequent heat treatment.

[0040] (3) The polyethylene fiber aerogel obtained by the preparation method of the present invention has a high specific surface area and elastic modulus, which provides more possibilities for the application of polyethylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The following is a flow chart showing the preparation process of polyethylene fiber provided by an embodiment of the present invention:

[0042] Figure 2 shows an SEM image of a polyethylene fiber aerogel provided by an embodiment of the present invention;

[0043] Figure 3 An SEM image showing the connection between fibers in the polyethylene fiber aerogel precursor before heat treatment of the present invention; and

[0044] Figure 4 The SEM image shows the connection mode between fibers in the polyethylene fiber aerogel after heat treatment of the present invention. DETAILED DESCRIPTION

[0045] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but are not to be construed as limiting the present invention. Unless otherwise specified, all scientific and technological terms used in the present invention have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. All patents and publications to which the present invention relates are incorporated herein by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, i.e., include the contents specified in the present invention, but do not exclude contents of other aspects.

[0046] The method for preparing the medium and high voltage anode foil provided by the present invention is as follows Figure 1 Specifically, according to an embodiment of the present invention, the method for preparing the polyethylene fiber includes:

[0047] Preheating: Heat high-density polyethylene at 300-500°C to melt to obtain polyethylene melt;

[0048] Electrospinning: The polyethylene melt is electrospun, and the resulting polyethylene fibers are freeze-dried in a liquid nitrogen tank to obtain a polyethylene fiber aerogel precursor. The spinning conditions are: positive voltage 10-50 kV, spinning distance 10-30 cm, and melt extrusion rate 1-5 mL / h;

[0049] Heat treatment: The polyethylene fiber aerogel precursor is heat treated at 60-120° C. for 1-5 hours to melt and weld the fibers to obtain polyethylene fiber aerogel.

[0050] The surface morphology of the polyethylene fiber aerogel obtained by the present invention is shown in FIG. Figure 2 As shown, the fibers are "melted and welded" together. The diameter of the nanofibers inside the aerogel is 50-1000nm; the elastic modulus of the aerogel is 30-120MPa; the specific surface area of ​​the aerogel is 389-1068m 2 / g.

[0051] Figure 3 and Figure 4 It shows the changing state of polyethylene fiber during the preparation process. Figure 3 This is an SEM image of the polyethylene fiber aerogel fiber precursor obtained after freeze-drying in liquid nitrogen. The fibers are only in contact with each other, which is the "overlap" mentioned in the present invention. After heat treatment, the fibers change from "overlap" to "melt welding", obtaining polyethylene fiber aerogel.

[0052] The embodiments of the present invention will be described in detail below with reference to the examples, but those skilled in the art will appreciate that the following examples are intended only to illustrate the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0053] Example 1:

[0054] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps:

[0055] First, 50g of high-density polyethylene powder was weighed and placed in the furnace of the electrospinning equipment. The furnace temperature was set to 300℃, and heated and stirred for 10 minutes to obtain a uniform and stable polyethylene melt. Then, a positive voltage of 20kV was applied to the nozzle end of the furnace, the square trough was grounded, the spinning distance was 20cm, the melt extrusion rate was 1mL / h, and the electrospun fibers were collected in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers were quickly condensed into blocks in the liquid nitrogen, which were polyethylene fiber precursors. Finally, the polyethylene fiber precursors were transferred to a drying oven for heat treatment at a temperature of 90℃ and a holding time of 1h. After constant temperature treatment, the nodes of the fibers changed from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel was obtained. The diameter of the aerogel fiber is about 750nm and the specific surface area is 530m 2 / g, and the elastic modulus is 98Mpa.

[0056] Example 2:

[0057] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps:

[0058] First, 50g of high-density polyethylene powder was weighed and placed in the furnace of the electrospinning equipment. The furnace temperature was set to 300℃, and heated and stirred for 10 minutes to obtain a uniform and stable polyethylene melt. Then, a positive voltage of 20kV was applied to the nozzle end of the furnace, the square trough was grounded, the spinning distance was 20cm, the melt extrusion rate was 3mL / h, and the electrospun fibers were collected in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers were quickly condensed into blocks in the liquid nitrogen, which were polyethylene fiber precursors. Finally, the polyethylene fiber precursor was transferred to a drying oven for heat treatment at a temperature of 90℃ and a holding time of 1h. After constant temperature treatment, the nodes at the fiber changed from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel was obtained. The diameter of the aerogel fiber is about 890nm, and the specific surface area is 427m 2 / g, and the elastic modulus is 95Mpa.

[0059] Example 3:

[0060] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps:

[0061] First, 50g of high-density polyethylene powder was weighed and placed in the furnace of the electrospinning equipment. The furnace temperature was set to 300℃, and heated and stirred for 10 minutes to obtain a uniform and stable polyethylene melt. Then, a positive voltage of 20kV was applied to the nozzle end of the furnace, the square trough was grounded, the spinning distance was 20cm, the melt extrusion rate was 5mL / h, and the electrospun fibers were collected in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers were quickly condensed into blocks in the liquid nitrogen, which were polyethylene fiber precursors. Finally, the polyethylene fiber precursors were transferred to a drying oven for heat treatment at a temperature of 90℃ and a holding time of 1h. After constant temperature treatment, the nodes of the fibers changed from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel was obtained. The diameter of the aerogel fiber is about 1000nm, and the specific surface area is 389m 2 / g, and the elastic modulus is 96Mpa.

[0062] Example 4:

[0063] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps:

[0064] First, 50g of high-density polyethylene powder was weighed and placed in the furnace of the electrospinning equipment. The furnace temperature was set to 400℃, and heated and stirred for 10 minutes to obtain a uniform and stable polyethylene melt; then, a positive voltage of 20kV was applied to the nozzle end of the furnace, the square trough was grounded, the spinning distance was 20cm, the melt extrusion rate was 1mL / h, and the electrospun fibers were collected in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers were quickly condensed into blocks in the liquid nitrogen. Finally, the condensed nanofiber blocks were transferred to a drying oven for heat treatment at a temperature of 90℃ and a holding time of 1h. After constant temperature treatment, the nodes of the fibers changed from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel was obtained. The diameter of the aerogel fiber is about 400nm, and the specific surface area is 621m 2 / g, and the elastic modulus is 53Mpa.

[0065] Example 5:

[0066] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps:

[0067] First, 50g of high-density polyethylene powder was weighed and placed in the furnace of the electrospinning equipment. The furnace temperature was set to 500℃, and heated and stirred for 10 minutes to obtain a uniform and stable polyethylene melt. Then, a positive voltage of 20kV was applied to the nozzle end of the furnace, the square trough was grounded, the spinning distance was 20cm, the melt extrusion rate was 1mL / h, and the electrospun fibers were collected in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers were quickly condensed into blocks in the liquid nitrogen, which were polyethylene fiber precursors. Finally, the polyethylene fiber precursors were transferred to a drying oven for heat treatment at a temperature of 90℃ and a holding time of 1h. After constant temperature treatment, the nodes at the fibers changed from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel was obtained. The diameter of the aerogel fiber is about 130nm, and the specific surface area is 908m 2 / g, and the elastic modulus is 89Mpa.

[0068] Example 6:

[0069] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps:

[0070] First, 50g of high-density polyethylene powder was weighed and placed in the furnace of the electrospinning equipment. The furnace temperature was set to 500℃, and heated and stirred for 10 minutes to obtain a uniform and stable polyethylene melt. Then, a positive voltage of 35kV was applied to the nozzle end of the furnace, the square trough was grounded, the spinning distance was 20cm, the melt extrusion rate was 1mL / h, and the electrospun fibers were collected in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers were quickly condensed into blocks in the liquid nitrogen, which were polyethylene fiber precursors. Finally, the polyethylene fiber precursors were transferred to a drying oven for heat treatment at a temperature of 90℃ and a holding time of 1h. After constant temperature treatment, the nodes of the fibers changed from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel was obtained. The diameter of the aerogel fiber is about 85nm, and the specific surface area is 943m 2 / g, and the elastic modulus is 87Mpa.

[0071] Example 7:

[0072] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps: First, weigh 50g of high-density polyethylene powder and place it in the furnace of the electrospinning equipment, set the furnace temperature to 500℃, heat and stir for 10 minutes to obtain a uniform and stable polyethylene melt; then, apply a positive voltage of 50kV to the nozzle end of the furnace, ground the square trough, spin at a distance of 20cm, and extrusion rate of melt 1mL / h. Collect the electrospun fibers in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers are quickly condensed into blocks in the liquid nitrogen, which are polyethylene fiber precursors; finally, transfer the polyethylene fiber precursor to a drying oven for heat treatment at a temperature of 90℃ and a holding time of 1h. After constant temperature treatment, the nodes of the fibers change from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel is obtained. The diameter of the aerogel fiber is about 50nm and the specific surface area is 1089m 2 / g, and the elastic modulus is 82Mpa.

[0073] Example 8:

[0074] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps: First, weigh 50g of high-density polyethylene powder and place it in the furnace of the electrospinning equipment, set the furnace temperature to 500℃, heat and stir for 10 minutes to obtain a uniform and stable polyethylene melt; then, apply a positive voltage of 50kV to the nozzle end of the furnace, ground the square trough, spin at a distance of 20cm, and extrusion rate of melt 1mL / h. Collect the electrospun fibers in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers are quickly condensed into blocks in the liquid nitrogen, which are polyethylene fiber precursors; finally, transfer the polyethylene fiber precursor to a drying oven for heat treatment at a temperature of 60℃ and a holding time of 1h. After constant temperature treatment, the nodes of the fibers change from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel is obtained. The diameter of the aerogel fiber is about 50nm and the specific surface area is 1089m 2 / g, and the elastic modulus is 30Mpa.

[0075] Example 9:

[0076] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps: First, weigh 50g of high-density polyethylene powder and place it in the furnace of the electrospinning equipment, set the furnace temperature to 500℃, heat and stir for 10 minutes to obtain a uniform and stable polyethylene melt; then, apply a positive voltage of 50kV to the nozzle end of the furnace, ground the square trough, spin at a distance of 20cm, and extrusion rate of melt 1mL / h. Collect the electrospun fibers in a square trough (40cm*40cm*8cm) filled with liquid nitrogen, and the electrospun fibers are quickly condensed into blocks in the liquid nitrogen. Finally, the condensed nanofiber blocks are transferred to a drying oven for heat treatment. The parameters are set as follows: heat treatment temperature of 120℃ and holding time of 1h. After constant temperature treatment, the nodes of the fibers change from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel is obtained. The diameter of the aerogel fiber is about 50nm and the specific surface area is 1089m 2 / g, and the elastic modulus is 98Mpa.

[0077] Example 10:

[0078] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps: First, weigh 50g of high-density polyethylene powder and place it in the furnace of the electrospinning equipment, set the furnace temperature to 500℃, heat and stir for 10 minutes to obtain a uniform and stable polyethylene melt; then, apply a positive voltage of 50kV to the nozzle end of the furnace, ground the square trough, spin at a distance of 20cm, and extrusion rate of 1mL / h. Collect the electrospun fibers in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers are quickly condensed into blocks in the liquid nitrogen, which are polyethylene fiber precursors; finally, transfer the polyethylene fiber precursor to a drying oven for heat treatment. The parameters are set as follows: heat treatment temperature is 120℃, and holding time is 3h. After constant temperature treatment, the nodes of the fibers change from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel is obtained. The diameter of the aerogel fiber is about 50nm, and the specific surface area is 1089m 2 / g, and the elastic modulus is 113Mpa.

[0079] Example 11:

[0080] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps: First, weigh 50g of high-density polyethylene powder and place it in the furnace of the electrospinning equipment, set the furnace temperature to 500℃, heat and stir for 10 minutes to obtain a uniform and stable polyethylene melt; then, apply a positive voltage of 50kV to the nozzle end of the furnace, ground the square trough, spin at a distance of 20cm, and extrusion rate of 1mL / h. Collect the electrospun fibers in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers are quickly condensed into blocks in the liquid nitrogen, which are polyethylene fiber precursors; finally, transfer the polyethylene fiber precursor to a drying oven for heat treatment at a temperature of 120℃ and a holding time of 5h. After constant temperature treatment, the nodes of the fibers change from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel is obtained. The diameter of the aerogel fiber is about 50nm and the specific surface area is 1089m 2 / g, and the elastic modulus is 120Mpa.

[0081] Comparative Example 1: (No heat treatment)

[0082] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps:

[0083] First, 50g of high-density polyethylene powder was weighed and placed in the furnace of the electrospinning equipment. The furnace temperature was set to 500℃, and heated and stirred for 10 minutes to obtain a uniform and stable polyethylene melt. Then, a positive voltage of 50kV was applied to the nozzle end of the furnace, the square trough was grounded, the spinning distance was 20cm, the melt extrusion rate was 1mL / h, and the electrospun fibers were collected in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers were quickly condensed into blocks in the liquid nitrogen, which were polyethylene fiber precursors. Finally, the polyethylene fiber precursor was air-dried at room temperature (25℃) and the insulation time was 5h. After constant temperature treatment, a self-supporting flexible aerogel was obtained. The aerogel fiber diameter was about 50nm and the specific surface area was 1089m 2 During the elastic modulus test, since the fibers are still in an "overlap" state, the aerogel undergoes irreversible deformation in the tensile and compressive structures, thus terminating the test.

[0084] Comparative Example 2: (heat treatment temperature is not 60-120)

[0085] The preparation process of high-density polyethylene fiber aerogel mainly includes the following steps:

[0086] First, 50g of high-density polyethylene powder was weighed and placed in the furnace of the electrospinning equipment. The furnace temperature was set to 500℃ and heated and stirred for 10 minutes to obtain a uniform and stable polyethylene melt. Then, a positive voltage of 50kV was applied to the nozzle end of the furnace, the square trough was grounded, the spinning distance was 20cm, the melt extrusion rate was 1mL / h, and the electrospun fibers were collected in a square trough (40cm*40cm*8cm) filled with liquid nitrogen. The electrospun fibers were quickly condensed into blocks in the liquid nitrogen, which were polyethylene fiber precursors. Finally, the polyethylene fiber precursors were transferred to a drying oven for heat treatment at a temperature of 150℃ and a holding time of 5h. After constant temperature treatment, the nodes of the fibers changed from simple "lap joints" to "melt welding" after being heated. After returning to room temperature, a self-supporting flexible aerogel was obtained. The diameter of the aerogel fiber was about 50nm. Due to the high specific surface area of ​​the nanofibers, the fiber network structure melted and collapsed in the overheated environment, causing its specific surface area to drop sharply to 134m 2 / g, and the elastic modulus is 15 MPa. This irreversible damage seriously limits the application range of polyethylene fiber aerogel.

[0087] In the description of this specification, the reference terms "some embodiments", "embodiments", "examples", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0088] Although the embodiments and examples of the present invention have been shown and described above, it will be understood that the above embodiments and examples are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments and examples within the scope of the present invention.

Claims

1. A method for preparing polyethylene fiber aerogel, characterized in that: include: Preheating: heating and melting high-density polyethylene to obtain polyethylene melt; Electrospinning: The polyethylene melt is electrospun, and the spun polyethylene fibers are freeze-dried to obtain a polyethylene fiber aerogel precursor; Heat treatment: heat-treating the polyethylene fiber aerogel precursor to melt and weld the fibers to obtain polyethylene fiber aerogel; the heat treatment temperature is 60-120°C and the heat treatment time is 1-5 hours; The diameter of the nanofibers inside the aerogel is 50-1000nm; the elastic modulus of the aerogel is 30-120MPa; the specific surface area of ​​the aerogel is 389-1068m 2 / g.

2. The method for preparing polyethylene fiber aerogel according to claim 1, characterized in that: The high-density polyethylene is heated and melted at a temperature of 300-500°C.

3. The method for preparing polyethylene fiber aerogel according to claim 1, characterized in that: During the electrospinning, the positive voltage is 10-50 kV.

4. The method for preparing polyethylene fiber aerogel according to claim 1, characterized in that: During the electrostatic spinning, the spinning distance is 10-30 cm.

5. The method for preparing polyethylene fiber aerogel according to claim 1, characterized in that: During the electrospinning, the melt extrusion rate is 1-5 mL / h.

6. The method for preparing polyethylene fiber aerogel according to claim 1, characterized in that: The freeze drying is performed in a liquid nitrogen tank, which is grounded.

7. Application of the polyethylene fiber aerogel obtained by the preparation method according to any one of claims 1 to 6 in the fields of catalytic carriers, ultra-light elastic filling materials and sound-absorbing materials.

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