CN115850970A - Preparation method of 3D printing polyimide-silicon oxide hybrid aerogel - Google Patents
Preparation method of 3D printing polyimide-silicon oxide hybrid aerogel Download PDFInfo
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Abstract
The invention discloses a preparation method of 3D printing polyimide-silicon oxide hybrid aerogel, aiming at enabling the 3D printing polyimide-silicon oxide hybrid aerogel to meet the index requirements of low density, high specific surface area, high compressive strength, low thermal conductivity and the like, and realizing flexible custom molding of aerogel structure and shape according to a heat insulation application scene. The main components of the 3D printing polyimide-silicon oxide hybrid aerogel are polyimide and silicon oxide, and the preparation method comprises the following steps: preparing a polyamic acid solution, synthesizing ink of the component A and the component B, performing double-channel co-extrusion 3D printing, solvent replacement and supercritical drying to obtain the 3D printing polyimide-silicon oxide hybrid aerogel. By adopting the method, the 3D printing polyimide-silicon oxide hybrid aerogel with a typical nano-pore structure and a customized geometric shape can be obtained, and the hybrid aerogel can be applied to heat insulation application dominated by a specific scene.
Description
Technical Field
The invention relates to the technical field of additive manufacturing of organic-inorganic hybrid aerogels, in particular to a preparation method of 3D printing polyimide-silicon oxide hybrid aerogel.
Background
The aerogel is a porous solid material formed by assembling a nano structure and a large amount of air, has typical characteristics of nano pores, such as low density, high porosity and high surface area, and has wide application prospects in various fields. Among the various aerogel classes, silica aerogels and their ancillary products have been used in large quantities due to their advantages of low cost, abundant raw materials and mature manufacturing techniques. However, silica aerogels have intrinsic ceramic brittleness, are very prone to structural fragmentation and release fine dust, and are difficult to apply directly. Organic polymers are desirable reinforcing materials for improving the mechanical properties of silica aerogels, and typical polymers include epoxy, isocyanate, polystyrene, polyurethane, and polyoxyethylene. The enhancement mechanism of the polymers is that the polymers form a nano coating with high crosslinking strength on the surfaces of silica particles by virtue of carbon-carbon covalent bonds, so that the overall specific stiffness and specific strength of the hybrid aerogel are effectively improved, and the mechanical strength requirement of the aerogel in an actual application scene is met.
Although the polymer can effectively improve the mechanical strength of the silica aerogel and enable the silica aerogel to meet certain machining requirements, the preparation process relying on traditional material reduction manufacturing still has the defects of time consumption, material waste, high cost, mold assistance and the like, and the customized structure and shape of the polymer crosslinked silica aerogel are difficult to endow. Compared with material reduction manufacturing, 3D printing (also called additive manufacturing) is known as a main driver of the fourth industrial revolution, and is a new technology that relies on computer aided design, and accumulates materials layer by layer from bottom to top to realize conversion from a 3D model to a physical object, and the advancement of the technology is low cost, low time consumption, and no need of mold assistance. To date, there are mainly three 3D printing techniques applied to the manufacture of aerogels, which include extrusion 3D printing, inkjet 3D printing, and photo-curing 3D printing. Among them, the extrusion 3D printing technology has been applied to additive manufacturing of silica aerogel due to its good ink compatibility advantage. For example, [ Nature,2020,584 (7821): 387-392] reported a method for the preparation of ammonia vapor induced extrusion 3D printed silica aerogels; [ Small Methods, (2022): 2200045] reported a method for the preparation of a heat-cured extruded 3D printed multi-component silica-based ceramic aerogel. The above documents are limited to the preparation of brittle 3D printed silica aerogels, and do not provide technical strategies for 3D printing of organic-inorganic hybrid aerogels, in particular, methods for the preparation of polyimide-silica hybrid aerogels suitable for 3D printing.
Therefore, the preparation method of the 3D printing polyimide-silicon oxide hybrid aerogel is developed and designed, the 3D printing polyimide-silicon oxide hybrid aerogel is endowed with customized structural shape (high size precision and shape fidelity), excellent nanopore performance (low density and high specific surface area), high compressive strength and low thermal conductivity, and the preparation method has important practical significance for meeting the high-efficiency heat insulation requirement of the actual application scene.
Disclosure of Invention
The invention aims to solve the technical problem of providing a preparation method of 3D printed polyimide-silicon oxide hybrid aerogel, so that the 3D printed polyimide-silicon oxide hybrid aerogel meets the index requirements of low density, high specific surface area, high compressive strength, low thermal conductivity and the like, and flexible custom molding of aerogel structure and shape is realized according to a heat insulation application scene.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention relates to a 3D printing polyimide-silicon oxide hybrid aerogel, which mainly comprises polyimide and silicon oxide. Wherein the mass fraction of the polyimide in the 3D printed polyimide-silicon oxide hybrid aerogel is 16.7-65.2 wt%, and the mass fraction of the silicon oxide in the 3D printed polyimide-silicon oxide hybrid aerogel is 34.8-83.3 wt%.
The preparation method of the 3D printing polyimide-silicon oxide hybrid aerogel mainly comprises the following steps: preparing a polyamic acid solution, synthesizing ink with component A and ink with component B, double-channel co-extrusion 3D printing, solvent replacement and supercritical drying.
The method comprises the following specific steps:
firstly, preparing a polyamic acid solution by the following steps:
dissolving diamine monomer in N-methyl pyrrolidone (mass concentration is more than or equal to 99%), magnetically stirring for 5-10 minutes for full dissolution, adding dianhydride monomer, controlling the chemical molar ratio of the diamine monomer to the dianhydride monomer to be 1.050 or 1.033 or 1.025, continuously stirring for 1-2 hours to enable the diamine monomer and the dianhydride monomer to fully react to obtain polyamic acid oligomers with different polymerization degrees, then adding a chemical cross-linking agent (1,3,5-benzene tricarbochloride) with a certain stoichiometric ratio, and continuously stirring for 1-2 hours to obtain a polyamic acid solution with the chemical polymerization degree of n =20 or 30 or 40.
The diamine monomer is 4,4 '-diaminodiphenyl ether (ODA) or 4,4' -diamino-2,2 '-dimethyl-1,1' -biphenyl (DMBZ);
the dianhydride monomer is 3,3',4,4' -biphenyl tetracarboxylic dianhydride (BPDA) or pyromellitic dianhydride (PMDA);
the polyamic acid refers to four polyamic acids of ODA-BPDA type or DMBZ-PMDA type or ODA-PMDA type or DMBZ-BPDA type obtained by chemically polymerizing different types of diamine and dianhydride monomers, and can be further subjected to chemical amidation reaction under the catalysis of an organic base catalyst to generate polyimide of ODA-BPDA type or DMBZ-PMDA type or ODA-PMDA type or DMBZ-BPDA type;
the organic base catalyst refers to liquid triethylamine or pyridine;
and step two, synthesizing the component A ink and the component B ink, wherein the method comprises the following steps:
2.1, synthesizing the component A ink: and (3) adding the nano silicon oxide powder with high specific surface area and acetic anhydride (mass concentration is more than or equal to 98.5%) into the polyamic acid solution prepared in the first step, and performing centrifugal defoaming and stirring for 1-30 minutes to obtain the component A ink which is free of bubbles and uniformly distributed in materials. In the component A ink, the nano silicon oxide powder mainly comprises gas-phase silicon oxide powder in a nano particle form and hydrophobic silicon oxide aerogel powder in a micron particle form, and the mass ratio of the gas-phase silicon oxide powder to the hydrophobic silicon oxide aerogel powder is controlled to be 4:1. wherein, hydrogen bond crosslinking action exists between the gas-phase silicon oxide powder and the polyamic acid, so that the viscosity of the polyamic acid can be obviously improved; the hydrophobic silica aerogel powder has high volume ratio in the component A ink, and can obviously adjust the pseudoplastic rheological property of the ink. In the component A ink composition, the mass ranges of the nano silicon oxide powder, the polyamic acid, the acetic anhydride and the N-methyl pyrrolidone are 8-15 wt%, 3-15 wt%, 10-20 wt% and 51-78 wt%;
the nano silicon oxide with high specific surface area refers to gas-phase silicon oxide powder with nano particle form and hydrophobic silicon oxide aerogel powder with micron particle form, and the specific surface areas of the two kinds of powder are both 100-800 m 2 ·g -1 Within the range;
the centrifugal defoaming stirring means that the revolution speed of a stirrer is controlled to be 400-1000 rpm and the rotation speed is controlled to be 100-800 rpm in the ink preparation process;
2.2, synthesizing B component ink: dissolving the organic base catalyst in a N-methyl pyrrolidone solution, and magnetically stirring for 5-10 minutes to obtain the B component ink. In the ink composition of the component B, the mass ranges of the organic base catalyst and the N-methyl pyrrolidone are 50-99.9 wt% and 0.1-50 wt%;
and thirdly, co-extruding the gel by two channels for 3D printing to obtain the 3D printing gel, wherein the method comprises the following steps:
3.1, designing and storing the structure and the shape of the 3D printing aerogel into a modeling file by means of three-dimensional modeling software (Solidworks, version number of 2013 and above), and identifying, reading and converting the modeling file by means of slicing software (Smart Slicer, version number of 2020 and above) to obtain a numerical control programming language (Gcode) for commanding the movement of a nozzle of the 3D printer.
And 3.2, respectively packaging the component A ink and the component B ink in a 3D printer bin, and performing double-in and one-out double-channel co-extrusion ink, wherein the component A ink and the component B ink are respectively injected into a mixer through separate channels at a certain extrusion speed, and after mixing in the mixer, jointly extruding a nozzle of the 3D printer to obtain mixed ink tows.
The certain extrusion speed refers to the volume flow rate of the component A ink and the component B ink, wherein the flow rate of the component A ink is controlled to be 5-40 mm 3 ·s -1 The flow rate of the B component ink is controlled to be 0.5-5 mm 3 ·s -1 ；
The mixer is a metal mixing device consisting of a first inlet, a second inlet and a zigzag structure channel, the first inlet and the second inlet are cylindrical, the diameter requirement is more than 0.2mm, the first inlet and the second inlet are converged at the inlet of the zigzag structure channel, and the outlet of the zigzag structure channel is the outlet of the mixer; the zigzag structure passageway is that the inside wall welding has the drum of baffle, zigzag structure passageway length L is greater than 5cm, diameter D control is within 10mm, the baffle is crisscross interval distribution in zigzag structure passageway, the terminal surface of baffle is less than the cross section of zigzag structure passageway, the baffle is perpendicular with the axial of zigzag structure passageway, baffle thickness is 1mm, baffle interval H is greater than 1mm, the baffle number is greater than 2, the baffle is used for changing the ink flow direction, slow down the flow velocity, it flows to make the ink take place the bending curve, reach better mixed effect.
And 3.3, planning a printing path according to a numerical control programming language, depositing mixed ink tows at a certain printing speed, and accumulating layer by layer to obtain the 3D printing gel. In the printing process, the A component ink and the B component ink sequentially undergo the mixing, extruding and curing process sequence in the time dimension, and when the A component ink and the B component ink are respectively extruded into the mixer through separate channels, the two inks begin to generate fluid flowing mixing; fully mixing to obtain mixed ink, and in the mixed ink, polyamide acid starts to perform slow chemical imidization reaction under the catalysis of organic base; after the mixed ink flows out of a nozzle of a 3D printer, polyamic acid is completely imidized and converted into polyimide after 5-30 minutes, and the ink which macroscopically shows pseudoplastic fluid behavior in the process is converted into completely cured solid gel (namely 3D printing gel);
the diameter of a discharge port of a nozzle of the 3D printer is required to be within the range of 0.8-3.0 mm;
the certain printing speed refers to the movement speed of the 3D printer nozzle in the directions of the x axis and the y axis being 0.2-30 mm.s -1 Within the range;
and fourthly, solvent replacement and supercritical drying are carried out to obtain the 3D printing polyimide-silicon oxide hybrid aerogel, and the method comprises the following steps:
4.1, solvent replacement, the method comprises the following steps: soaking the 3D printing gel prepared in the third step in a closed container filled with absolute ethyl alcohol (the mass concentration is more than or equal to 98 percent), and requiring that the absolute ethyl alcohol is completely soaked in the 3D printing gel; and heating the 3D printing gel in a constant temperature range for 24-48 hours to accelerate the rate of replacing the nitrogen methyl pyrrolidone solvent by the ethanol solvent. And continuously soaking the 3D printing gel in absolute ethyl alcohol at room temperature (10-30 ℃) to remove residual impurities, and replacing the ethyl alcohol solvent once after 6-36 hours, wherein the number of times of replacing the ethyl alcohol solvent is 2-8. The constant temperature range means that the external heating temperature is controlled to be 40-60 ℃;
4.2 placing the 3D printing gel after solvent replacement in CO 2 In supercritical fluid environment, supercritical CO 2 The fluid fully replaces ethanol in the 3D printing gel to obtain the 3D printing polyimide-silicon oxide hybrid aerogel;
said CO 2 The supercritical fluid is CO at 35-70 deg.C and 8-15 MPa 2 The gas state is changed into the supercritical fluid state.
Compared with the prior art, the invention has the following beneficial effects:
(1) The polyamic acid solution prepared in the first step of the invention is the key point for realizing the mechanical enhancement of the polyimide-silicon oxide hybrid aerogel in 3D printing. The polyamic acid with long molecular weight chain can be adsorbed on the surface of silicon oxide particles and form a polymer-silicon oxide network by virtue of the cross-linking action of hydroxyl hydrogen bonds, and then an organic-inorganic phase coexisting aerogel network framework is formed by virtue of an imidization reaction, so that the intrinsic brittleness of the silicon oxide aerogel is fundamentally improved, the 3D printing polyimide-silicon oxide hybrid aerogel is endowed with high compressive strength, and the compressive strength distribution range of a 5% strain part is 0.04-1.56 MPa.
(2) The rheological property of the ink can be effectively adjusted by adding the nano silicon oxide powder into the component A ink in the second step of the invention, because the hydrophobic silicon oxide aerogel has high specific surface area and high pore volume, the hydrophobic silicon oxide aerogel presents high volume ratio in an ink system, and the rheological property of the pseudoplastic ink can be obviously adjusted; a dynamic hydrogen bond crosslinking network is formed between the gas-phase silicon oxide powder and the polyamic acid, so that the viscosity of the polyamic acid solution can be remarkably improved, and the condition that the micron-grade silicon oxide aerogel particles are settled in the A-component ink due to gravity to cause the blockage of a printer nozzle and cannot be extruded and printed is prevented.
(3) The 3D printing polyimide-silicon oxide hybrid aerogel prepared by the method has the characteristics of low density, high surface area and low thermal conductivity. The 3D printing gel in the fourth step can pass through supercritical CO 2 Drying and converting into 3D printing polyimide-silicon oxide hybrid aerogel with density distribution range of 0.11-0.39 g cm -3 The specific surface area is in the range of 354 to 556m 2 ·g -1 The thermal conductivity is in the range of 0.020-0.045 W.m -1 ·K -1 。
(4) The 3D printing polyimide-silicon oxide hybrid aerogel with high dimensional accuracy and high shape fidelity can be obtained by adopting the method. In the third step of the double-channel co-extrusion 3D printing process, the nozzle caliber of different printers directly influences the surface precision of the 3D printing piece, and the smaller the nozzle caliber is, the more beneficial the 3D printing polyimide-silicon oxide hybrid aerogel with high dimensional precision can be obtained. In the printing process, A, B component inks are mixed with each other, and polyamide acid is subjected to amidation reaction after contacting with an organic base catalyst to generate polyimide, which macroscopically shows that the ink is slowly cured automatically after being extruded out of a 3D printer nozzle, so that the 3D printed polyimide-silicon oxide hybrid aerogel can effectively keep a printing structure and shape and has high shape fidelity.
(5) The 3D printing polyimide-silicon oxide hybrid aerogel has the advantages of rich raw material types, low price, simple double-channel co-extrusion 3D printing method and strong technical implementation, and has certain practical significance for additive manufacturing of mechanically enhanced organic-inorganic hybrid aerogel.
Drawings
Fig. 1 is a flow chart of a preparation method of 3D printed polyimide-silica hybrid aerogel according to the present invention.
Fig. 2 is a diagram showing a two-channel co-extrusion 3D printing ink process (fig. 2 (a)) in the third step of example 1 of the present invention, and an internal structure diagram of a mixer having zigzag type meandering channels (fig. 2 (b)).
FIG. 3 is a 3D printing gel with ink tows stacked layer by layer to form a complex open grid structure when the nozzle is 1.35mm in diameter using the present invention.
Fig. 4 is a 3D printed polyimide-silica hybrid aerogel obtained after the 3D printed gel of fig. 3 goes through the fourth step (example 1).
Detailed Description
The invention is further illustrated by the following figures and examples. The 3D printed polyimide-silica hybrid aerogel density, thermal conductivity, specific surface area, and compressive strength, to which the present invention is focused, were mainly studied in the examples. In the embodiment, the density of the 3D printed polyimide-silica hybrid aerogel is obtained by calculating a volume and a mass method, the thermal conductivity is measured by using a thermal conductivity constant instrument (FOX 200), the specific surface area is obtained by calculating a nitrogen adsorption-desorption isotherm collected by a nitrogen adsorption device (Quantachrome) by using a BET theory, and the compressive strength is obtained by testing with a universal mechanical experiment machine (XBD-4000).
In the process of preparing the 3D printing polyimide-silicon oxide hybrid aerogel, the type, polymerization degree and dosage of the polyamic acid and the dosage of the nano silicon oxide powder have obvious influence on the density, thermal conductivity, specific surface area and compressive strength of the 3D printing polyimide-silicon oxide hybrid aerogel, and other factors have almost no influence on the density, thermal conductivity, specific surface area and compressive strength of the 3D printing polyimide-silicon oxide hybrid aerogel concerned by the invention. The following discussion about the influence of 4 critical parameters, i.e., the type, polymerization degree, amount and amount of the polyamic acid on the density, thermal conductivity, specific surface area and compressive strength of the 3D-printed polyimide-silica hybrid aerogel, is made, and the present invention is further illustrated by examples, and the scope of the present invention should not be construed as being limited to these examples.
Example 1:
as shown in fig. 1, preparative example 1 included the following steps:
firstly, preparing a polyamic acid solution by the following steps:
4,4' -diaminodiphenyl ether (ODA) diamine monomer is dissolved in nitrogen methyl pyrrolidone (99% by mass), after the diamine monomer is fully dissolved by magnetic stirring for 5 minutes, 3,3',4,4' -biphenyl tetracarboxylic dianhydride (BPDA) dianhydride monomer is added, the chemical molar ratio of diamine to dianhydride monomer is controlled to be 1.033, the stirring is continued for 1 hour, a chemical cross-linking agent (1,3,5-trimesoyl chloride) with a fixed stoichiometric ratio is added, and the stirring is continued for 1 hour to obtain an ODA-BPDA type polyamic acid solution with the chemical polymerization degree of n = 30.
And a second step of synthesizing A, B component ink, which comprises the following steps:
2.1 Synthesis of ink of component A: adding nanometer silica powder (specific surface area 300 m) into the ODA-BPDA type polyamic acid solution with the chemical polymerization degree of n =30 prepared in the first step 2 ·g -1 The hydrophobic silica aerogel powder has a specific surface area of 200m 2 ·g -1 Gas-phase silicon oxide powder, wherein the mass ratio of the gas-phase silicon oxide powder to the gas-phase silicon oxide powder is 4: 1) The ink comprises a component A and acetic anhydride (the mass concentration is 98.5%), and is prepared by stirring the mixture for 20 minutes in a centrifugal defoaming manner under the conditions of a revolution speed of 800rpm and a rotation speed of 400rpm, wherein the component A has no air bubbles and is uniformly distributed in materials, and the mass ranges of the nano silicon oxide powder, the polyamic acid, the acetic anhydride and the azomethyl pyrrolidone are 12wt%, 8wt%, 15wt% and 65wt%;
2.2 Synthesis of ink of component B: and dissolving triethylamine in the N-methyl pyrrolidone solution, and magnetically stirring for 10 minutes to obtain the B component ink. Wherein, the mass ranges of the triethylamine and the N-methyl pyrrolidone are 75wt% and 25wt%;
and thirdly, co-extruding the gel by two channels for 3D printing to obtain the 3D printing gel, wherein the method comprises the following steps:
3.1, designing and storing the structure and the appearance of the 3D printing aerogel into a modeling file by means of three-dimensional modeling software (Solidworks, version number 2013), and identifying, reading and converting the modeling file by means of slicing software (Smart Slicer, version number 2020) to obtain a numerical control programming language (Gcode) for commanding the movement of a nozzle of the 3D printer.
3.2, respectively packaging the component A ink and the component B ink in a 3D printer bin, and performing double-in and one-out double-channel co-extrusion ink, wherein the component A ink is 20mm in size as shown in figure 2 (a) 3 ·s -1 Flows through the first channel 1, and the B component ink flows by 5mm 3 ·s -1 The extrusion speed flows through the second channel 2, and the two are injected into the mixer 3 together, as shown in fig. 2 (b), the mixer 3 is a metal mixing device consisting of a first inlet 3-1, a second inlet 3-2 and a zigzag structure channel 3-4, the first inlet 3-1 and the second inlet 3-2 are both cylindrical, the diameter is required to be more than 0.2mm, the first inlet 3-1 and the second inlet 3-2 are converged at the inlet of the zigzag structure channel 3-4, and the outlet of the zigzag structure channel 3-4 is the outlet 3-3 of the mixer 3; the zigzag structure channel 3-4 is a cylinder with partition boards 3-5 welded on the inner side wall, the length L of the zigzag structure channel 3-4 is 6cm, the diameter D is 5mm, the partition boards 3-5 are distributed in the zigzag structure channel 3-4 at staggered intervals, the end face of the partition board 3-5 is smaller than the cross section of the zigzag structure channel 3-4, the partition boards 3-5 are perpendicular to the axial direction of the zigzag structure channel 3-4 (namely, alpha is 90 degrees in 2 (b)), the thickness of the partition boards is 1mm, the space H between the partition boards is 4mm, the number of the partition boards is 4, and the partition boards 3-5 are used for changing the ink flow direction and slowing down the flow speed, so that the ink flows in a bending curve, and a better mixing effect is achieved. After flowing through the zigzag-structured channels 3-4 inside the mixer 3, the mixed ink filament bundle was co-extruded from the 3D printer nozzle 4 (the diameter of the 3D printer nozzle 4 is 1.35mm, as shown in fig. 2 (a)). Wherein, in the mixer 3, the component A ink enters from a first inlet 3-1 with the diameter of 4mm, the component B ink enters from a second inlet 3-2 with the diameter of 4mm, and flows through the first inlet with the length L of 6cm and the diameter D of 5mm at an interval of adjacentThe space H between the plates 3-5 is 4mm, the number of the partition plates 3-5 is 4, and mixed ink is obtained after the stainless steel zigzag structure channels 3-4, and the mixed ink enters the printer nozzle 4 through the outlet 3-3 with the diameter of 4 mm.
3.3, planning a printing path according to a numerical control programming language and setting the printing path to be 15 mm.s -1 Depositing mixed ink on a two-dimensional plane at the moving speed of the ink, and accumulating layer by layer to obtain 3D printing gel; as shown in fig. 3, the 3D printing gel with the hollow structure is formed by cumulatively stacking a plurality of printing layers, and the interior of a single printing layer is spliced by orthogonal tows to form a regular grid;
and fourthly, solvent replacement and supercritical drying are carried out to obtain the 3D printing polyimide-silicon oxide hybrid aerogel, and the method comprises the following steps:
4.1, soaking the 3D printing gel prepared in the third step in a closed container of absolute ethyl alcohol (mass concentration is more than or equal to 98%), heating the 3D printing gel at 60 ℃ for 48 hours, and accelerating the rate of replacing the nitrogen methyl pyrrolidone solvent by the ethanol solvent. And continuously soaking the 3D printing gel in absolute ethyl alcohol (the mass concentration is more than or equal to 98%) to remove impurities, and replacing the ethyl alcohol solvent once after 24 hours, wherein the number of times of replacing the ethyl alcohol solvent is 5.
4.2 placing the 3D printing gel after solvent replacement in CO generated at the temperature of 55 ℃ and the pressure of 13MPa 2 In supercritical fluid environment, supercritical CO 2 And (3) fully replacing ethanol in the 3D printing gel with the fluid to obtain the 3D printing polyimide-silica hybrid aerogel. Fig. 4 is a 3D printed polyimide-silica hybrid aerogel obtained after the fourth step of the 3D printed gel of fig. 3, the 3D printed aerogel can maintain the same shape and structure as the 3D printed gel, and exhibits good shape fidelity. The density of the 3D printed polyimide-silicon oxide hybrid aerogel is 0.22g cm -3 The specific surface area is 506m 2 ·g -1 The thermal conductivity is 0.022 W.m -1 ·K -1 The compressive strength at 5% strain was 0.55MPa.
Example 2:
preparative example 2 comprises the following steps:
firstly, preparing a polyamic acid solution by the following steps:
4,4' -diamino-2,2 ' -dimethyl-1,1 ' -biphenyl (DMBZ) diamine monomer is dissolved in nitrogen methyl pyrrolidone (99% by mass), after the monomer is fully dissolved by magnetic stirring for 5 minutes, pyromellitic dianhydride (PMDA) dianhydride monomer is added, the chemical molar ratio of diamine to dianhydride monomer is controlled to be 1.033, the stirring is continued for 1 hour, a chemical cross-linking agent (1,3,5-benzene tricarbochloride) with a stoichiometric ratio is added, and the stirring is continued for 1 hour to obtain the DMBZ-PMDA type polyamide acid solution with the chemical polymerization degree of n = 30.
And a second step of synthesizing A, B component ink, which comprises the following steps:
2.1 Synthesis of ink of component A: taking the DMBZ-PMDA type polyamide acid solution with the chemical polymerization degree of n =30 prepared in the first step, adding nano silicon oxide powder (the specific surface area is 300 m) 2 ·g -1 The hydrophobic silica aerogel powder has a specific surface area of 200m 2 ·g -1 Gas-phase silicon oxide powder, wherein the mass ratio of the gas-phase silicon oxide powder to the gas-phase silicon oxide powder is 4: 1) The ink comprises a component A and acetic anhydride (the mass concentration is 98.5%), and is prepared by stirring the mixture for 15 minutes in a centrifugal defoaming manner under the conditions of a revolution speed of 800rpm and a rotation speed of 400rpm, wherein the component A has no air bubbles and is uniformly distributed in materials, and the mass ranges of the nano silicon oxide powder, the polyamic acid, the acetic anhydride and the azomethyl pyrrolidone are 12wt%, 8wt%, 15wt% and 65wt%;
2.2 Synthesis of ink of component B: and dissolving pyridine in a N-methyl pyrrolidone solution, and magnetically stirring for 10 minutes to obtain the B component ink. Wherein, the mass ranges of the pyridine and the azomethyl pyrrolidone are 75wt% and 25wt%;
and thirdly, co-extruding the gel by two channels for 3D printing to obtain the 3D printing gel, wherein the method comprises the following steps:
3.1, designing and storing the structure and the appearance of the 3D printing aerogel into a modeling file by means of three-dimensional modeling software (Solidworks, version number 2013), and identifying, reading and converting the modeling file by means of slicing software (Smart Slicer, version number 2020) to obtain a numerical control programming language (Gcode) for commanding the movement of a nozzle of the 3D printer.
3.2, respectively packaging the component A ink and the component B ink in a 3D printer bin, and performing double-channel co-extrusion ink of 'two inlets and one outlet', wherein the component A is shown in figure 2 (a)Ink with a thickness of 20mm 3 ·s -1 Flows through the first channel 1, and the B component ink flows by 5mm 3 ·s -1 The extrusion speed flows through the second channel 2, and the two are injected into the mixer 3 together, and after flowing through the zigzag structure channels 3-4 inside the mixer 3, the mixed ink filament bundle is obtained by extruding the 3D printer nozzle 4 (figure 2 a) with the diameter of 1.35mm together, as shown in figure 2 (b). In the mixer 3, the ink of the component A enters from a first inlet 3-1 with the diameter of 4mm, the ink of the component B enters from a second inlet 3-2 with the diameter of 4mm, mixed ink is obtained after flowing through stainless steel zigzag structure channels 3-4 with the length L of 6cm, the diameter D of 5mm, the distance H between partition plates of 4mm and the number of partition plates 3-5 of 4, and the mixed ink enters the printer nozzle 4 through an outlet 3-3 with the diameter of 4 mm.
3.3, planning a printing path according to a numerical control programming language and setting the printing path to be 15 mm.s -1 The mixed ink is deposited on a two-dimensional plane at the movement speed, 3D printing gel is obtained through layer-by-layer accumulation, the 3D printing gel with the hollow structure is formed by accumulating and accumulating a plurality of printing layers, and a regular grid is formed by splicing orthogonal tows in a single printing layer;
and fourthly, solvent replacement and supercritical drying are carried out to obtain the 3D printing polyimide-silicon oxide hybrid aerogel, and the method comprises the following steps:
4.1, soaking the 3D printing gel prepared in the third step in a closed container of absolute ethyl alcohol (mass concentration is more than or equal to 98%), heating the 3D printing gel at 60 ℃ for 48 hours, and accelerating the rate of replacing the nitrogen methyl pyrrolidone solvent by the ethanol solvent. And continuously soaking the 3D printing gel in absolute ethyl alcohol (the mass concentration is more than or equal to 98%) to remove impurities, and replacing the ethyl alcohol solvent once after 24 hours, wherein the number of times of replacing the ethyl alcohol solvent is 5.
4.2 placing the 3D printing gel after solvent replacement in CO generated at the temperature of 55 ℃ and the pressure of 13MPa 2 In supercritical fluid environment, supercritical CO 2 After the fluid fully replaces ethanol in the 3D printing gel, the 3D printing polyimide-silicon oxide hybrid aerogel is obtained, the 3D printing aerogel can keep the same shape and structure as the 3D printing gel, and good shape fidelity is shown. The density of the 3D printed polyimide-silicon oxide hybrid aerogel is 0.21g cm -3 Specific surface area of 487m 2 ·g -1 Thermal conductivity of 0.023 W.m -1 ·K -1 The compressive strength at 5% strain was 0.52MPa.
Example 3:
preparative example 3 comprises the following steps:
firstly, preparing a polyamic acid solution by the following steps:
4,4' -diaminodiphenyl ether (ODA) diamine monomer is dissolved in nitrogen methyl pyrrolidone (with the mass concentration of 99%), after magnetic stirring is carried out for 5 minutes to fully dissolve the diamine monomer, pyromellitic anhydride (PMDA) dianhydride monomer is added, the chemical molar ratio of diamine to dianhydride monomer is controlled to be 1.033, stirring is continued for 1 hour, a chemical cross-linking agent (1,3,5-benzene tricarboxy chloride) with a fixed stoichiometric ratio is added, and stirring is continued for 1 hour to obtain the ODA-PMDA type polyamide acid solution with the chemical polymerization degree of n = 30.
And a second step of synthesizing A, B component ink, which comprises the following steps:
2.1 Synthesis of ink of component A: adding nanometer silica powder (specific surface area 300 m) into the ODA-PMDA type polyamide acid solution with the chemical polymerization degree of n =30 prepared in the first step 2 ·g -1 The hydrophobic silica aerogel powder has a specific surface area of 200m 2 ·g -1 Gas-phase silicon oxide powder, wherein the mass ratio of the gas-phase silicon oxide powder to the gas-phase silicon oxide powder is 4: 1) The ink comprises a component A and acetic anhydride (the mass concentration is 98.5%), and is prepared by stirring the mixture for 15 minutes in a centrifugal defoaming manner under the conditions of a revolution speed of 800rpm and a rotation speed of 400rpm, wherein the component A has no air bubbles and is uniformly distributed in materials, and the mass ranges of the nano silicon oxide powder, the polyamic acid, the acetic anhydride and the azomethyl pyrrolidone are 12wt%, 8wt%, 15wt% and 65wt%;
2.2 Synthesis of ink of component B: and dissolving pyridine in a N-methyl pyrrolidone solution, and magnetically stirring for 10 minutes to obtain the B component ink. Wherein, the mass ranges of the pyridine and the azomethyl pyrrolidone are 75wt% and 25wt%;
and thirdly, co-extruding the gel by two channels for 3D printing to obtain the 3D printing gel, wherein the method comprises the following steps:
3.1, designing and storing the structure and the appearance of the 3D printing aerogel into a modeling file by means of three-dimensional modeling software (Solidworks, version number 2013), and identifying, reading and converting the modeling file by means of slicing software (Smart Slicer, version number 2020) to obtain a numerical control programming language (Gcode) for commanding the movement of a nozzle of the 3D printer.
3.2, respectively packaging the component A ink and the component B ink in a 3D printer bin, and performing double-in and one-out double-channel co-extrusion ink, wherein the component A ink is 20mm in size as shown in figure 2 (a) 3 ·s -1 Flows through the first channel 1, and the B component ink flows by 5mm 3 ·s -1 The extrusion speed flows through the second channel 2, and the two are injected into the mixer 3 together, and after flowing through the zigzag structure channels 3-4 inside the mixer 3, the mixed ink filament bundle is obtained by extruding the 3D printer nozzle 4 (figure 2 a) with the diameter of 1.35mm together, as shown in figure 2 (b). In the mixer 3, the ink of the component A enters from a first inlet 3-1 with the diameter of 4mm, the ink of the component B enters from a second inlet 3-2 with the diameter of 4mm, mixed ink is obtained after flowing through stainless steel zigzag structure channels 3-4 with the length L of 6cm, the diameter D of 5mm, the distance H between partition plates of 4mm and the number of partition plates 3-5 of 4, and the mixed ink enters the printer nozzle 4 through an outlet 3-3 with the diameter of 4 mm.
3.3, planning a printing path according to a numerical control programming language and setting the printing path to be 15 mm.s -1 The mixed ink is deposited on a two-dimensional plane at the movement speed, 3D printing gel is obtained through layer-by-layer accumulation, the 3D printing gel with the hollow structure is formed by accumulating and accumulating a plurality of printing layers, and a regular grid is formed by splicing orthogonal tows in a single printing layer;
and fourthly, solvent replacement and supercritical drying are carried out to obtain the 3D printing polyimide-silicon oxide hybrid aerogel, and the method comprises the following steps:
4.1, soaking the 3D printing gel prepared in the third step in a closed container of absolute ethyl alcohol (mass concentration is more than or equal to 98%), heating the 3D printing gel at 60 ℃ for 48 hours, and accelerating the rate of replacing the nitrogen methyl pyrrolidone solvent by the ethanol solvent. And continuously soaking the 3D printing gel in absolute ethyl alcohol (the mass concentration is more than or equal to 98%) to remove impurities, and replacing the ethyl alcohol solvent once after 24 hours, wherein the number of times of replacing the ethyl alcohol solvent is 5.
4.2, placing the 3D printing gel after the solvent replacement at the temperature of 55 ℃ and the pressure of 13MPa to generateFormed CO 2 In supercritical fluid environment, by supercritical CO 2 After the fluid fully replaces ethanol in the 3D printing gel, the 3D printing polyimide-silicon oxide hybrid aerogel is obtained, the 3D printing aerogel can keep the same shape and structure as the 3D printing gel, and good shape fidelity is shown. The density of the 3D printing polyimide-silicon oxide hybrid aerogel is 0.22g cm -3 The specific surface area is 516m 2 ·g -1 The thermal conductivity is 0.022 W.m -1 ·K -1 The compressive strength at 5% strain was 0.55MPa.
Example 4:
preparative example 4 included the following steps:
firstly, preparing a polyamic acid solution by the following steps:
4,4' -diamino-2,2 ' -dimethyl-1,1 ' -biphenyl (DMBZ) diamine monomer is dissolved in nitrogen methyl pyrrolidone (99% by mass), after the monomer is fully dissolved by magnetic stirring for 5 minutes, 3,3',4,4' -biphenyl tetracarboxylic dianhydride (BPDA) dianhydride monomer is added, the chemical molar ratio of diamine to dianhydride monomer is controlled to be 1.033, the stirring is continued for 1 hour, a chemical cross-linking agent (1,3,5-benzene tricarbochloride) with a fixed stoichiometric ratio is added, and the stirring is continued for 1 hour to obtain the DMBZ-PMDA type polyamic acid solution with the chemical polymerization degree of n = 30.
And a second step of synthesizing A, B component ink, which comprises the following steps:
2.1 Synthesis of ink of component A: taking the DMBZ-PMDA type polyamide acid solution with the chemical polymerization degree of n =30 prepared in the first step, adding nano silicon oxide powder (the specific surface area is 300 m) 2 ·g -1 The hydrophobic silica aerogel powder has a specific surface area of 200m 2 ·g -1 Gas-phase silicon oxide powder, wherein the mass ratio of the gas-phase silicon oxide powder to the gas-phase silicon oxide powder is 4: 1) The ink comprises a component A and acetic anhydride (the mass concentration is 98.5%), and is prepared by stirring the mixture for 15 minutes in a centrifugal defoaming manner under the conditions of a revolution speed of 800rpm and a rotation speed of 400rpm, wherein the component A has no air bubbles and is uniformly distributed in materials, and the mass ranges of the nano silicon oxide powder, the polyamic acid, the acetic anhydride and the azomethyl pyrrolidone are 12wt%, 8wt%, 15wt% and 65wt%;
2.2 Synthesis of ink of component B: and dissolving triethylamine in the N-methyl pyrrolidone solution, and magnetically stirring for 10 minutes to obtain the B component ink. Wherein, the mass ranges of the triethylamine and the N-methyl pyrrolidone are 75wt% and 25wt%;
thirdly, double-channel coextrusion 3D printing is carried out to obtain 3D printing gel, and the method comprises the following steps:
3.1, designing and storing the structure and the appearance of the 3D printing aerogel into a modeling file by means of three-dimensional modeling software (Solidworks, version number 2013), and identifying, reading and converting the modeling file by means of slicing software (Smart Slicer, version number 2020) to obtain a numerical control programming language (Gcode) for commanding the movement of a nozzle of the 3D printer.
3.2, respectively packaging the component A ink and the component B ink in a 3D printer bin, and performing double-in and one-out double-channel co-extrusion ink, wherein the component A ink is 20mm in size as shown in figure 2 (a) 3 ·s -1 Flows through the first channel 1, and the B component ink flows by 5mm 3 ·s -1 The extrusion speed flows through the second channel 2, and the two are injected into the mixer 3 together, and after flowing through the zigzag structure channels 3-4 inside the mixer 3, the mixed ink filament bundle is obtained by extruding the 3D printer nozzle 4 (figure 2 a) with the diameter of 1.35mm together, as shown in figure 2 (b). In the mixer 3, the ink of the component A enters from a first inlet 3-1 with the diameter of 4mm, the ink of the component B enters from a second inlet 3-2 with the diameter of 4mm, mixed ink is obtained after flowing through stainless steel zigzag structure channels 3-4 with the length L of 6cm, the diameter D of 5mm, the distance H between partition plates of 4mm and the number of partition plates 3-5 of 4, and the mixed ink enters the printer nozzle 4 through an outlet 3-3 with the diameter of 4 mm.
3.3, planning a printing path according to a numerical control programming language and setting the printing path to be 15 mm.s -1 Depositing mixed ink on a two-dimensional plane at the movement speed, and accumulating layer by layer to obtain 3D printing gel, wherein the 3D printing gel with a hollow structure is formed by accumulating and accumulating a plurality of printing layers, and the interior of each printing layer is spliced by orthogonal tows to form a regular grid;
and fourthly, carrying out solvent replacement and supercritical drying to obtain the 3D printing polyimide-silicon oxide hybrid aerogel, wherein the method comprises the following steps:
4.1, soaking the 3D printing gel prepared in the third step in a closed container of absolute ethyl alcohol (mass concentration is more than or equal to 98%), heating the 3D printing gel at 60 ℃ for 48 hours, and accelerating the rate of replacing the nitrogen methyl pyrrolidone solvent by the ethanol solvent. And continuously soaking the 3D printing gel in absolute ethyl alcohol (the mass concentration is more than or equal to 98%) to remove impurities, and replacing the ethyl alcohol solvent once after 24 hours, wherein the number of times of replacing the ethyl alcohol solvent is 5.
4.2 placing the 3D printing gel after solvent replacement in CO generated at the temperature of 55 ℃ and the pressure of 13MPa 2 In supercritical fluid environment, supercritical CO 2 After the fluid fully replaces ethanol in the 3D printing gel, the 3D printing polyimide-silicon oxide hybrid aerogel is obtained, the 3D printing aerogel can keep the same shape and structure as the 3D printing gel, and good shape fidelity is shown. The density of the 3D printed polyimide-silicon oxide hybrid aerogel is 0.22g cm -3 Specific surface area of 421m 2 ·g -1 Thermal conductivity of 0.024 W.m -1 ·K -1 The compressive strength at 5% strain was 0.54MPa.
In the second step of the present invention, in the component a ink, changing the amount of acetic anhydride has no effect on the density, thermal conductivity, specific surface area and compressive strength of the 3D printed polyimide-silica hybrid aerogel contemplated by the present invention; the specific surface area of gas-phase silica powder and hydrophobic aerogel powder in the nano silica powder has a remarkable influence on the solvent adsorption capacity, the density, the heat conductivity and the compression strength of the 3D printed polyimide-silica hybrid aerogel are hardly influenced, and the influence on the specific surface area performance of the 3D printed polyimide-silica hybrid aerogel is small and can be basically ignored; the stirring time and the stirring speed of the centrifugal defoaming stirrer have no influence on the density, the thermal conductivity, the specific surface area and the compressive strength of the 3D printing polyimide-silicon oxide hybrid aerogel concerned by the invention, and only the defoaming degree of the ink is influenced by the stirring time and the stirring speed. In the B component ink, the type and the dosage of the organic base catalyst have no influence on the density, the thermal conductivity, the specific surface area and the compressive strength of the 3D printing polyimide-silicon oxide hybrid aerogel. In the third step, the caliber size of a nozzle of the 3D printer only influences the precision of 3D printing of the polyimide-silicon oxide hybrid aerogel, the extrusion speed of A, B component ink and the movement speed of the nozzle of the 3D printer only influence the speed of the 3D printing process, and the density, the thermal conductivity, the specific surface area and the compression strength of the 3D printing polyimide-silicon oxide hybrid aerogel concerned by the invention are not influenced. In the fourth step, the solvent displacement and drying conditions had no effect on the 3D printed polyimide-silica hybrid aerogel density, thermal conductivity, specific surface area, and compressive strength of interest for the present invention. Therefore, the above conditions have no influence on the density, thermal conductivity, specific surface area and compressive strength of the 3D printed polyimide-silica hybrid aerogel, and a 3D printed polyimide-silica hybrid aerogel with good performance can be obtained if selected within the ranges described in the summary of the invention.
The process parameters used for examples 3 to 54 are shown in Table 1. Observing the data in table 1, the density range of 3D printed polyimide-silica hybrid aerogels was 0.11 to 0.39 g-cm -3 The thermal conductivity is in the range of 0.020-0.045 W.m -1 ·K -1 The specific surface area is in the range of 354 to 556m 2 ·g -1 And the compressive strength range of 5% strain is 0.04-1.56 MPa, which shows that the 3D printed polyimide-silicon oxide hybrid aerogel still maintains the typical nano-pore structural characteristics and shows excellent mechanical properties and heat insulation performance. The 3D printed polyimide-silica hybrid aerogel prepared from different kinds of polyamic acid solutions has similar property change rules, and the specific change rules are as follows: the density is increased along with the increase of the consumption of the polyamic acid and the consumption of the nano silicon oxide powder, and the influence of the change of the polymerization degree on the density is relatively small; the specific surface area is increased along with the increase of the consumption of the polyamic acid and is reduced along with the increase of the polymerization degree, and the influence of changing the nano silicon oxide powder on the specific surface area is small; the compressive strength is increased along with the increase of the dosage of the polyamic acid and the dosage of the nano silicon oxide powder and is reduced along with the increase of the polymerization degree; the thermal conductivity is increased along with the increase of the dosage of the polyamic acid and the dosage of the nano silicon oxide powder, and is slightly reduced along with the increase of the polymerization degree.
According to the results of the embodiment of the invention, the 3D printing polyimide-silicon oxide hybrid aerogel prepared by the method has the advantages of low density, high specific surface area, low thermal conductivity and high compressive strength, and can realize the design and flexible manufacturing of the customized aerogel structure shape. In addition, the ultraviolet-assisted direct-writing 3D printing scheme can construct a specific aerogel structure according to the requirements of practical application scenes, and has important practical significance for efficient heat insulation application.
The above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, but all changes that can be made by applying the principles of the present invention and performing non-inventive work on the basis of the principles shall fall within the scope of the present invention.
TABLE 1 preparation Process parameters and associated Properties of 3D printed polyimide-silica hybrid aerogels
Claims (13)
1. A preparation method of 3D printing polyimide-silicon oxide hybrid aerogel is characterized by comprising the following steps:
firstly, preparing a polyamic acid solution by the following steps: dissolving a diamine monomer in N-methyl pyrrolidone, adding a dianhydride monomer after magnetic stirring and sufficient dissolution, controlling the chemical molar ratio of the diamine monomer to the dianhydride monomer to be 1.050 or 1.033 or 1.025, continuously stirring to enable the diamine monomer and the dianhydride monomer to fully react to obtain polyamic acid oligomers with different polymerization degrees, then adding a chemical cross-linking agent with a certain stoichiometric ratio, and continuously stirring to obtain a polyamic acid solution with the chemical polymerization degree of n =20 or 30 or 40;
the diamine monomer is 4,4 '-diaminodiphenyl ether namely ODA or 4,4' -diamino-2,2 '-dimethyl-1,1' -biphenyl namely DMBZ;
the dianhydride monomer is 3,3',4,4' -biphenyl tetracarboxylic dianhydride, namely BPDA or pyromellitic dianhydride, namely PMDA;
the polyamic acid refers to four polyamic acids of ODA-BPDA type or DMBZ-PMDA type or ODA-PMDA type or DMBZ-BPDA type obtained by chemically polymerizing different types of diamine monomers and dianhydride monomers;
and step two, synthesizing the component A ink and the component B ink, wherein the method comprises the following steps:
2.1, synthesizing ink of the component A: adding nano silicon oxide powder with high specific surface area and acetic anhydride into the polyamic acid solution prepared in the first step, and performing centrifugal defoaming and stirring to obtain the component A ink without bubbles and with uniformly distributed materials; the nano silicon oxide powder is gas phase silicon oxide powder in a nano particle form and hydrophobic silicon oxide aerogel powder in a micron particle form, and the mass ratio of the gas phase silicon oxide powder to the hydrophobic silicon oxide aerogel powder is controlled to be 4:1; wherein, hydrogen bond crosslinking action exists between the gas-phase silicon oxide powder and the polyamic acid, so that the viscosity of the polyamic acid is improved; the hydrophobic silica aerogel powder has high volume ratio in the component A ink, and the pseudoplastic rheological property of the ink is adjusted; in the component A ink composition, the mass ranges of the nano silicon oxide powder, the polyamic acid, the acetic anhydride and the N-methyl pyrrolidone are 8-15 wt%, 3-15 wt%, 10-20 wt% and 51-78 wt%;
2.2, synthesizing B component ink: dissolving an organic base catalyst in a N-methyl pyrrolidone solution, and magnetically stirring to obtain B component ink; in the ink composition of the component B, the mass ranges of the organic base catalyst and the N-methyl pyrrolidone are 50-99.9 wt% and 0.1-50 wt%;
and thirdly, co-extruding the gel by two channels for 3D printing to obtain the 3D printing gel, wherein the method comprises the following steps:
3.1, designing and storing the structure and the shape of the 3D printing aerogel into a modeling file by depending on three-dimensional modeling software, and identifying, reading and converting the modeling file by slicing software to obtain a numerical control programming language Gcode commanding the movement of a 3D printer nozzle (4);
3.2, respectively packaging the component A ink and the component B ink in a bin of a 3D printer, and performing double-inlet and one-outlet double-channel co-extrusion ink, wherein the component A ink and the component B ink are respectively injected into a mixer (3) through separate channels at a certain extrusion speed, and after mixing in the mixer (3), jointly extruding a nozzle (4) of the 3D printer to obtain mixed ink tows; the component A ink and the component B ink respectively pass through the first channel (3-1) and the second channel (3-2) through the independent channels;
3.3, planning a printing path according to a numerical control programming language, depositing mixed ink tows at a certain printing speed, and accumulating layer by layer to obtain 3D printing gel; in the printing process, the A-component ink and the B-component ink sequentially undergo mixing, extruding and curing process sequences in a time dimension, and when the A-component ink and the B-component ink are respectively extruded into the mixer (3) through separate channels, fluid flow mixing of the two inks begins to occur; fully mixing to obtain mixed ink, and in the mixed ink, polyamide acid starts to perform slow chemical imidization reaction under the catalysis of organic base; after the mixed ink flows out of a nozzle (4) of the 3D printer, the polyamic acid is converted into polyimide through imidization reaction, and the process is that the ink with pseudoplastic fluid behavior is converted into completely cured solid gel, namely 3D printing gel;
and fourthly, solvent replacement and supercritical drying are carried out to obtain the 3D printing polyimide-silicon oxide hybrid aerogel, and the method comprises the following steps:
4.1, solvent replacement, the method comprises the following steps: soaking the 3D printing gel prepared in the third step in a closed container filled with absolute ethyl alcohol, and requiring the absolute ethyl alcohol to be completely soaked in the 3D printing gel; heating the 3D printing gel in a constant temperature range to accelerate the rate of replacing the nitrogen methyl pyrrolidone solvent by the ethanol solvent; continuously soaking the 3D printing gel in absolute ethyl alcohol at room temperature to remove residual impurities;
4.2 placing the 3D printing gel after solvent replacement in CO 2 In supercritical fluid environment, supercritical CO 2 And the fluid fully replaces ethanol in the 3D printing gel to obtain the 3D printing polyimide-silicon oxide hybrid aerogel.
2. The preparation method of the 3D printed polyimide-silica hybrid aerogel according to claim 1, wherein the mass concentration of the N-methylpyrrolidone in the first step is not less than 99%; the magnetic stirring time is 5 to 10 minutes before the dianhydride monomer is added; adding dianhydride monomer, stirring for 1-2 hr, the continuous stirring time after the chemical cross-linking agent is added is 1 to 2 hours.
3. The method for preparing 3D printed polyimide-silica hybrid aerogel according to claim 1, wherein the chemical cross-linking agent in the first step is 1,3,5-benzenetricarboxychloride.
4. The method for preparing 3D printing polyimide-silica hybrid aerogel according to claim 1, wherein the polyamic acid solution in the first step is further subjected to chemical amidation reaction under the catalysis of organic base catalyst to generate polyimide of ODA-BPDA type or DMBZ-PMDA type or ODA-PMDA type or DMBZ-BPDA type.
5. The preparation method of the polyimide-silica hybrid aerogel for 3D printing according to claim 1, wherein the mass concentration of the acetic anhydride in the 2.1 steps is not less than 98.5%, and the time for centrifugal defoaming and stirring is 1-30 minutes; the nano silicon oxide with high specific surface area refers to gas-phase silicon oxide powder with nano particle form and hydrophobic silicon oxide aerogel powder with micron particle form, and the specific surface areas of the two kinds of powder are both 100-800 m 2 ·g -1 Within the range; the above-mentionedThe centrifugal defoaming stirring means that the revolution speed of the stirrer is controlled to be 400-1000 rpm and the rotation speed is controlled to be 100-800 rpm in the ink preparation process.
6. The preparation method of the 3D printed polyimide-silica hybrid aerogel according to claim 1, wherein the magnetic stirring time in the 2.2 steps is 5-10 minutes.
7. The method for preparing 3D printed polyimide-silica hybrid aerogel according to claim 1 or 4, wherein the organic base catalyst is triethylamine or pyridine.
8. The preparation method of 3D printed polyimide-silica hybrid aerogel according to claim 1, wherein 3.1 steps of the three-dimensional modeling software Solidworks requires version number 2013 and above; the slicing software Smart Slicer requires version number 2020 and above.
9. The method for preparing 3D printed polyimide-silica hybrid aerogel according to claim 1, wherein the certain extrusion speed in 3.2 steps is the volume flow rate of the component A ink and the component B ink, and the flow rate of the component A ink is controlled to be 5-40 mm 3 ·s -1 The flow rate of the B component ink is controlled to be 0.5-5 mm 3 ·s -1 。
10. The 3D printing polyimide-silica hybrid aerogel preparation method according to claim 1, characterized in that 3.2 steps of the mixer (3) is a metal mixing device consisting of a first inlet (3-1), a second inlet (3-2) and a zigzag structure channel (3-4), the first inlet (3-1) and the second inlet (3-2) are both cylindrical, the diameter is required to be greater than 0.2mm, the first inlet (3-1) and the second inlet (3-2) are merged at the inlet of the zigzag structure channel (3-4), and the outlet of the zigzag structure channel (3-4) is the outlet (3-3) of the mixer (3); the zigzag structure channel (3-4) is a cylinder with partition boards (3-5) welded on the inner side wall, the length L of the zigzag structure channel (3-4) is larger than 5cm, the diameter D is controlled within 10mm, the partition boards (3-5) are distributed in the zigzag structure channel (3-4) at intervals in a staggered mode, the end face of each partition board (3-5) is smaller than the cross section of the zigzag structure channel (3-4), the partition boards (3-5) are perpendicular to the axial direction of the zigzag structure channel (3-4), the thickness of each partition board is 1mm, the space H between the partition boards is larger than 1mm, the number of the partition boards is larger than 2, and the partition boards (3-5) are used for changing the ink flow direction and slowing down the flow speed to enable ink to flow in a bending curve mode.
11. The preparation method of 3D printed polyimide-silica hybrid aerogel according to claim 10, wherein the diameter of the first inlet (3-1) and the second inlet (3-2) is required to be greater than 0.2mm, the length L of the zigzag structure channel (3-4) is greater than 5cm, the diameter D is controlled within 10mm, the thickness of the partition plate (3-5) is 1mm, the distance H between adjacent partition plates (3-5) is greater than 1mm, and the number of partition plates (3-5) is greater than 2.
12. The method for preparing 3D printed polyimide-silica hybrid aerogel according to claim 1, wherein the certain printing speed in 3.3 steps means that the moving speed of the 3D printer nozzle (4) in the directions of the x axis and the y axis is 0.2-30 mm-s -1 Within the range; the diameter of a discharge hole of the 3D printer nozzle (4) is required to be within the range of 0.8-3.0 mm; the time for the polyamic acid to be converted into polyimide through imidization reaction is as long as 5 to 30 minutes.
13. The preparation method of the 3D printing polyimide-silica hybrid aerogel according to claim 1, wherein the mass concentration of the absolute ethyl alcohol in the fourth step is not less than 98%, and the time for heating the 3D printing gel in a constant temperature range is 24-48 hours; continuously soaking the 3D printing gel in absolute ethyl alcohol at room temperature to remove residual impurities, and replacing the ethyl alcohol solvent once after 6-36 hours, wherein the number of times of replacing the ethyl alcohol solvent is 2-8; the room temperature is 10-30 ℃; the constant temperature range means that the external heating temperature is controlled to be 40-60 ℃; the CO is 2 The supercritical fluid is CO at 35-70 deg.C and 8-15 MPa 2 From gaseous state to supercritical fluid state。
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| CN107936685A (en) * | 2017-11-17 | 2018-04-20 | 同济大学 | A kind of preparation method of polyimides ink available for 3D printing |
| CN111234297A (en) * | 2020-01-10 | 2020-06-05 | 东华大学 | 3D printing polyimide aerogel and preparation method thereof |
| KR20220041287A (en) * | 2020-09-24 | 2022-04-01 | 연세대학교 원주산학협력단 | Polyimide aerogel using SLA-3D printer and its manufacturing method |
| CN115124756A (en) * | 2022-07-14 | 2022-09-30 | 中国人民解放军国防科技大学 | Preparation method of ultraviolet-assisted 3D printing polymer crosslinked silica aerogel |
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| CN107936685A (en) * | 2017-11-17 | 2018-04-20 | 同济大学 | A kind of preparation method of polyimides ink available for 3D printing |
| CN111234297A (en) * | 2020-01-10 | 2020-06-05 | 东华大学 | 3D printing polyimide aerogel and preparation method thereof |
| KR20220041287A (en) * | 2020-09-24 | 2022-04-01 | 연세대학교 원주산학협력단 | Polyimide aerogel using SLA-3D printer and its manufacturing method |
| CN115124756A (en) * | 2022-07-14 | 2022-09-30 | 中国人民解放军国防科技大学 | Preparation method of ultraviolet-assisted 3D printing polymer crosslinked silica aerogel |
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