CN115785593B - Simple preparation method of high-plasticity superhydrophobic low-thermal-conductivity PVDF aerogel - Google Patents
Simple preparation method of high-plasticity superhydrophobic low-thermal-conductivity PVDF aerogel Download PDFInfo
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- 239000002033 PVDF binder Substances 0.000 title claims abstract description 186
- 229920002981 polyvinylidene fluoride Polymers 0.000 title claims abstract description 186
- 239000004964 aerogel Substances 0.000 title claims abstract description 89
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 230000003075 superhydrophobic effect Effects 0.000 title claims abstract description 20
- 239000007788 liquid Substances 0.000 claims abstract description 64
- 239000011240 wet gel Substances 0.000 claims abstract description 61
- 238000003756 stirring Methods 0.000 claims abstract description 39
- 239000000411 inducer Substances 0.000 claims abstract description 27
- 239000002904 solvent Substances 0.000 claims abstract description 27
- 239000000843 powder Substances 0.000 claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229920000642 polymer Polymers 0.000 claims abstract description 18
- 239000008367 deionised water Substances 0.000 claims abstract description 15
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 15
- 238000002210 supercritical carbon dioxide drying Methods 0.000 claims abstract description 4
- 238000001035 drying Methods 0.000 claims description 57
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 18
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 12
- DQWPFSLDHJDLRL-UHFFFAOYSA-N triethyl phosphate Chemical compound CCOP(=O)(OCC)OCC DQWPFSLDHJDLRL-UHFFFAOYSA-N 0.000 claims description 11
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical group CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 9
- 238000010572 single replacement reaction Methods 0.000 claims description 8
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 4
- 229920006373 Solef Polymers 0.000 claims description 2
- 238000004090 dissolution Methods 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 9
- 239000007864 aqueous solution Substances 0.000 abstract description 3
- 238000006243 chemical reaction Methods 0.000 abstract description 3
- 229920002521 macromolecule Polymers 0.000 abstract description 3
- 239000000126 substance Substances 0.000 abstract description 3
- 230000007613 environmental effect Effects 0.000 abstract 1
- 238000006073 displacement reaction Methods 0.000 description 24
- 239000011148 porous material Substances 0.000 description 13
- 230000002209 hydrophobic effect Effects 0.000 description 12
- 238000009413 insulation Methods 0.000 description 12
- 239000000853 adhesive Substances 0.000 description 10
- 230000001070 adhesive effect Effects 0.000 description 10
- 238000001878 scanning electron micrograph Methods 0.000 description 10
- 238000000352 supercritical drying Methods 0.000 description 10
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 238000010298 pulverizing process Methods 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000000499 gel Substances 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000007783 nanoporous material Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000010189 synthetic method Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P20/00—Technologies relating to chemical industry
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Abstract
The invention discloses a simple preparation method of high-plasticity superhydrophobic low-heat-conductivity PVDF aerogel, which comprises the following steps: s1, dissolving PVDF polymer powder in a solvent under rapid stirring to form highly viscous liquid; s2, dispersing deionized water in the same solvent as that in the S1 to prepare a PVDF bonding inducer; s3, uniformly and rapidly dripping the PVDF bonding inducer into the viscous liquid under rapid stirring in the S1, and immediately stopping stirring when the dripping is finished; s4, after PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement; s5, intermittent supercritical CO 2 drying is carried out on PVDF wet gel after the replacement is finished for a plurality of cycles. The invention uses diluted aqueous solution to induce the mutual connection between PVDF macromolecules with high adhesiveness to construct the skeleton structure of PVDF aerogel, does not contain any chemical reaction, effectively avoids the pollution to the environment caused by the release of small molecular substances, has higher environmental friendly degree, simple process steps, short preparation period and low requirement on equipment platforms.
Description
Technical Field
The invention belongs to the technical field of synthesis of multifunctional nano porous materials, and particularly relates to a simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel.
Background
Aerogel is a nano porous solid material formed by random cross-linking of nano particles or high polymer molecules in three-dimensional space, and is a product obtained by substituting air for liquid in pores on the premise of keeping the integrity of the pore structure. Compared with other types of macroscopic or nanometer materials, the aerogel generally has the structural characteristics of high specific surface area, large pore volume, low density, high porosity and the like, so that the aerogel has wide application prospects in the fields of optics, acoustics, medical treatment, heat insulation, catalysis, aerospace and the like.
Because of the existence of the special nano porous skeleton structure, the aerogel has good heat insulation capacity of a heat insulator, and the heat conductivity coefficient of the aerogel is comparable to or even lower than that of air, so the aerogel is expected by people in the heat insulation field. However, due to the structural characteristics of high porosity and the fragile skeleton connection mode, the most widely studied such as SiO 2 aerogel, al 2O3 aerogel, C aerogel and the like always have the limitations of large brittleness, easy pulverization, poor processability and the like, and cannot be applied in practical occasions, and can only be compounded with other materials for use by various means, but the modes cannot truly exert the performance advantages of the aerogel due to the unique structure. Moreover, the aerogel also has water absorption characteristics after being manufactured by certain processes, and can be continuously influenced by water vapor in the air to cause structural collapse under the conventional preservation or application, which further reduces the possibility of practical application.
Therefore, in order to achieve the goal of coexistence of performances such as strong heat insulation, superhydrophobicity and deformability of the aerogel, researchers have conducted intensive research on synthesis and structural design of the organic aerogel, and aerogel formation processes of at least organic matters are gradually developed, but few reports of PVDF aerogel appear. PVDF has the advantages of superhydrophobicity, fatigue resistance, dissolubility, plasticization and the like, and is hopeful to become the aerogel with high plasticity superhydrophobicity and low heat conduction by combining the structural characteristics of the aerogel. From the application point of thermal insulation, only pure PVDF aerogel (Jiayue Zhang, yong Kong, xiaodong Screen. Materials Letters,259, 2020:126890) was successfully synthesized in 2020 by Nanjing university at present. The aerogel has low heat conductivity coefficient of 0.03602W/(m.K) and hydrophobic angle of 126 degrees under the low density of 0.078g/cm 3, and preliminarily proves the application potential of the PVDF aerogel as the super-hydrophobic low heat conductivity aerogel. However, the PVDF powder of U.S. solef6020,605,20 selected for this study was extremely sensitive to water and formed a lump-like precipitate upon wetting. Thus, the sol-gel process induced by the phase (PVDF powder is mixed with water before PVDF precipitation in solid form induced by water evaporation) is an uncontrollable process and often difficult to perform case reproduction. Therefore, the synthetic thought of phase-change induced sol-gel is avoided, and a novel synthetic method for building the PVDF aerogel skeleton structure by relying on high adhesion among PVDF high polymer powders of different types is innovatively adopted.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a simple preparation method of high-plasticity superhydrophobic low-heat-conductivity PVDF aerogel, which is formed by inducing the interconnection between PVDF macromolecules with high adhesiveness by using a diluted aqueous solution, wherein the skeleton structure does not contain any chemical reaction, so that the pollution to the environment caused by the release of small molecular substances is effectively avoided, and the environment friendliness is higher.
The aim of the invention is realized by the following technical scheme: a simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving PVDF polymer powder in a solvent under rapid stirring to form highly viscous liquid; the PVDF polymer powder is of the type of Amara HSV, of the type of Suwei solef or of the type of Shanghai Sanai Fu FR, the relative molecular mass is 60-100 ten thousand, the dissolution temperature is 80-120 ℃, and the dosage ratio of the PVDF polymer powder to the solvent is 1g: (8-12) ml; the solvent is N-methylpyrrolidone, triethyl phosphate or dimethyl sulfoxide.
S2, dispersing deionized water in the same solvent as that in the S1 to prepare a PVDF bonding inducer; the solvent is N-methyl pyrrolidone, triethyl phosphate or dimethyl sulfoxide, and the volume ratio of deionized water to the solvent is (0.8-1.3): (10-15).
S3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at the dripping speed of 1-3 ml/min, and stopping stirring immediately after the dripping is finished.
S4, after PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement; the replacement liquid is methanol, ethanol or acetone, the volume of the replacement liquid is 6-10 times of that of PVDF wet gel, the replacement times are 3-5 times, and the single replacement time is 5-10 hours.
S5, performing intermittent supercritical CO 2 drying for a plurality of cycles on the PVDF wet gel after the replacement is finished, and preparing PVDF aerogel; taking air exhaust for 0.8-1.5 h and pressure maintaining for 0.5-1.2 h as a drying cycle, and totally drying for 5-7 cycles, wherein the drying temperature is 60-80 ℃, the drying pressure is 12-16 MPa, and the air exhaust rate is 1.6-2.8L/min.
The beneficial effects of the invention are as follows: the PVDF aerogel synthesized by the method has an ultra-light three-dimensional nano ultra-porous structure (density of 0.064-0.107 g/cm < 3 >, porosity of 97.5-99.2%), integrates excellent performances of high plasticity (80% strain can be generated without damage), low heat conduction (0.02916-0.03527W/(m.K), super-hydrophobicity (hydrophobic angle of 138.2-144.6 ℃) and the like, effectively overcomes the bottleneck that the aerogel is difficult to directly apply due to structural and performance limitations such as high brittleness, easy pulverization, easy water absorption and the like, and is suitable for wide application in the heat preservation and insulation field. In addition, the preparation process designed by the invention is to induce the interconnection between PVDF macromolecules with high adhesiveness by using a diluted aqueous solution to construct a skeleton structure of PVDF aerogel, wherein the skeleton structure does not contain any chemical reaction, the pollution to the environment caused by the release of small molecular substances is effectively avoided, the environment-friendly degree is higher, the whole process can be completed by only one step, the process steps are simple, the preparation period is short, the requirements on equipment platforms are low, and a new thought and a new method which are suitable for laboratory research and industrial production are provided for the synthesis of PVDF aerogel. In addition, the invention has the advantages that the raw materials are few, the selected PVDF polymer powder and the like belong to industrial products, the cost is low, the sources are wide, the designed intermittent supercritical CO 2 drying can ensure that enough solvent is extracted when CO 2 is discharged, and the waste caused by the conventional continuous emission of CO 2 is avoided.
Drawings
FIG. 1 is an SEM image of PVDF aerogel of example 1 and a compressive stress strain curve;
FIG. 2 is an SEM image of PVDF aerogel of example 2 and a compressive stress strain curve;
FIG. 3 is an SEM image of PVDF aerogel of example 3 and a compressive stress strain curve;
FIG. 4 is an SEM image of PVDF aerogel of example 4 and a compressive stress strain curve;
fig. 5 is an SEM image of PVDF aerogel in example 5 and a compressive stress strain curve.
Detailed Description
Aiming at the problem that inorganic matters such as SiO 2 aerogel, al 2O3 aerogel and C aerogel are difficult to apply due to the limitations of large brittleness, easy pulverization, poor processing performance and the like, the invention also provides a novel method for synthesizing the PVDF aerogel with high heat insulation, superhydrophobicity, deformability and other performances by utilizing the characteristic of strong adhesiveness among PVDF polymer powder in order to expand the synthetic thought of the PVDF aerogel. The technical scheme of the invention is further described below with reference to the attached drawings and specific embodiments.
Example 1
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving PVDF polymer powder with the relative molecular mass of 2gHSV to 100 ten thousand in 20ml of N-methylpyrrolidone under rapid stirring at 90 ℃ to form highly viscous liquid;
S2, dispersing 2ml of deionized water in 20ml of N-methylpyrrolidone to prepare a PVDF bonding inducer;
S3, uniformly and rapidly dripping the PVDF bonding inducer into the viscous liquid under the rapid stirring in the S1 at the dripping speed of 1.5ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement, wherein the replacement liquid is methanol, the volume of the replacement liquid is 8 times of that of the PVDF wet gel, the replacement times are 4 times, and the single replacement time is 6 hours;
s5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking the air exhaust for 1h and the pressure maintaining for 0.8h as a drying cycle, and totally drying for 5 cycles, wherein the drying temperature is 60 ℃, the drying pressure is 13MPa, and the air exhaust rate is 2.4L/min.
Structurally, the PVDF aerogel obtained in this example has the structural characteristics of a three-dimensional nanoporous structure, a density of 0.075g/cm 3, a porosity of 98.2%, a specific surface area of 76m 2/g and an average pore size of 28.3nm. From the analysis of performance, the PVDF aerogel has good plastic deformation capability, thermal insulation performance and hydrophobicity, the deformation amount is up to 82.7%, the corresponding ultimate strength is 566kPa, the heat conductivity coefficient is 0.2772W/(m.K) and the hydrophobic angle is 138.9 degrees. SEM images of PVDF aerogel and compressive stress strain curves are shown in fig. 1.
Example 2
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
s1, dissolving 2g of PVDF high molecular powder with 80 ten thousand relative molecular mass of a soft6015 type in 16ml of triethyl phosphate under rapid stirring at 105 ℃ to form highly viscous liquid;
S2, dispersing 1.5ml of deionized water in 15ml of triethyl phosphate to prepare a PVDF bonding inducer;
S3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at the dripping speed of 2.5ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a displacement liquid for solvent displacement, wherein the displacement liquid is ethanol, the volume of the displacement liquid is 10 times of that of the PVDF wet gel, the displacement times are 3 times, and the single displacement time is 8 hours;
S5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking the pressure maintaining for 1h after exhausting for 1.5h as a drying cycle, and drying for 6 cycles, wherein the drying temperature is 70 ℃, the drying pressure is 12MPa, and the exhausting rate is 2.0L/min.
Structurally, the resulting PVDF aerogel has the aerogel structural characteristics of a three-dimensional nanoporous structure, a density of 0.101g/cm 3, a porosity of 95.6%, a specific surface area of 91m 2/g and an average pore size of 21.7nm. From the analysis of performance, the PVDF aerogel has good plastic deformation capability, thermal insulation performance and hydrophobicity, the deformation amount is as high as 85.8%, the corresponding ultimate strength is 854kPa, the heat conductivity coefficient is 0.3288/(m.K) and the hydrophobic angle is 139.8 degrees. SEM images of PVDF aerogel and compressive stress strain curves are shown in fig. 2.
Example 3
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving 2g PVDF polymer powder with the relative molecular mass of 60 ten thousand in 18ml dimethyl sulfoxide under rapid stirring at 120 ℃ to form highly viscous liquid;
s2, dispersing 3ml of deionized water in 35ml of dimethyl sulfoxide to prepare a PVDF bonding inducer;
s3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at a dripping rate of 3.0ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement, wherein the replacement liquid is isopropanol, the volume of the replacement liquid is 6 times of that of the PVDF wet gel, the replacement times are 5 times, and the single replacement time is 5 hours;
S5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking air exhaust for 0.9h and pressure maintaining for 0.6h as a drying cycle, and totally drying for 7 cycles, wherein the drying temperature is 60 ℃, the drying pressure is 14MPa, and the air exhaust rate is 1.6L/min.
Structurally, the PVDF aerogel obtained in this example has the structural characteristics of a three-dimensional nanoporous structure, a density of 0.061g/cm 3, a porosity of 99.0%, a specific surface area of 57m 2/g and an average pore size of 38.2nm. From the analysis of performance, the PVDF aerogel has good plastic deformation capability, thermal insulation performance and hydrophobicity, the deformation amount is 79.3%, the corresponding ultimate strength is 259kPa, the heat conductivity is 0.2966/(m.K) and the hydrophobic angle is 128.3 degrees. SEM images of PVDF aerogel and compressive stress strain curves are shown in fig. 3.
Example 4
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving 2g of a PVDF polymer powder with a relative molecular mass of 80 ten thousand of a type of soft6010 in 16ml of triethyl phosphate under rapid stirring at 95 ℃ to form highly viscous liquid;
s2, dispersing 1ml of deionized water in 10ml of triethyl phosphate to prepare a PVDF bonding inducer;
S3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at the dripping speed of 1.0ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a displacement liquid for solvent displacement, wherein the displacement liquid is ethanol, the volume of the displacement liquid is 9 times of that of the PVDF wet gel, the displacement times are 4 times, and the single displacement time is 7 hours;
S5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking the pressure maintaining for 1.2 hours after exhausting for 1.2 hours as a drying cycle, and totally drying for 5 cycles, wherein the drying temperature is 75 ℃, the drying pressure is 15MPa, and the exhausting rate is 2.6L/min.
Structurally, the PVDF aerogel obtained in this example has the structural characteristics of a three-dimensional nanoporous structure, a density of 0.113g/cm 3, a porosity of 94.8%, a specific surface area of 78m 2/g and an average pore size of 19.6nm. From the analysis of performance, the PVDF aerogel has good plastic deformation capability, thermal insulation performance and hydrophobicity, the deformation amount is up to 84.5%, the corresponding ultimate strength is 873kPa, the heat conductivity is 0.3745/(m.K) and the hydrophobic angle is 136.8 degrees. SEM images of PVDF aerogel and compressive stress strain curves are shown in fig. 4.
Example 5
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving 2g of PVDF polymer powder with the relative molecular mass of 100 ten thousand of HS7611A in 22ml of dimethyl sulfoxide under the condition of rapid stirring at 100 ℃ to form highly viscous liquid;
s2, dispersing 1.8ml of deionized water in 20ml of dimethyl sulfoxide to prepare a PVDF bonding inducer;
S3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at the dripping speed of 2.5ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement, wherein the replacement liquid is methanol, the volume of the replacement liquid is 10 times of that of the PVDF wet gel, the replacement times are 4 times, and the single replacement time is 6 hours;
s5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking air exhaust for 0.8h and pressure maintaining for 0.8h as a drying cycle, and totally drying for 6 cycles, wherein the drying temperature is 70 ℃, the drying pressure is 12MPa, and the air exhaust rate is 2.8L/min.
Structurally, the PVDF aerogel obtained in this example has the structural characteristics of a three-dimensional nanoporous structure, a density of 0.079g/cm 3, a porosity of 97.8%, a specific surface area of 74m 2/g and an average pore size of 29.6nm. From the analysis of performance, the PVDF aerogel has good plastic deformation capability, thermal insulation performance and hydrophobicity, the deformation amount is up to 82.4%, the corresponding ultimate strength is 529kPa, the heat conductivity is 0.2843/(m.K) and the hydrophobic angle is 129.3 degrees. SEM images of PVDF aerogel and compressive stress strain curves are shown in fig. 5.
Example 6
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving PVDF polymer powder with the relative molecular mass of 2gHSV to 100 ten thousand in 24ml of N-methylpyrrolidone under rapid stirring at 80 ℃ to form highly viscous liquid;
s2, dispersing 2ml of deionized water in 24ml of N-methylpyrrolidone to prepare a PVDF bonding inducer;
S3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at a dripping rate of 2ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement, wherein the replacement liquid is methanol, the volume of the replacement liquid is 8 times of that of the PVDF wet gel, the replacement times are 5 times, and the single replacement time is 6 hours;
S5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking the air exhaust for 1h and the pressure maintaining for 0.8h as a drying cycle, and totally drying for 5 cycles, wherein the drying temperature is 70 ℃, the drying pressure is 15MPa, and the air exhaust rate is 2.4L/min.
Structurally, the PVDF aerogel obtained in this example has a density of 0.069g/cm 3, a porosity of 98.8%, a specific surface area of 71m 2/g and an average pore size of 30.8nm. From the analysis of performance, the gas deformation amount of the PVDF is up to 80.6%, the corresponding ultimate strength is 517kPa, the heat conductivity is 0.2968/(m.K) and the hydrophobic angle is 131.4 degrees.
Example 7
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
s1, dissolving 2g of PVDF high molecular powder with 80 ten thousand relative molecular mass of a soft6015 type into 16ml of triethyl phosphate under rapid stirring at 115 ℃ to form highly viscous liquid;
S2, dispersing 1.5ml of deionized water in 15ml of triethyl phosphate to prepare a PVDF bonding inducer;
S3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under rapid stirring in the S1 at a dripping rate of 3ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a displacement liquid for solvent displacement, wherein the displacement liquid is ethanol, the volume of the displacement liquid is 8 times of that of the PVDF wet gel, the displacement times are 4 times, and the single displacement time is 8 hours;
S5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking the air exhaust for 1h and the pressure maintaining for 1h as a drying cycle, and totally drying for 6 cycles, wherein the drying temperature is 65 ℃, the drying pressure is 12MPa, and the air exhaust rate is 2.5L/min.
Structurally, the PVDF aerogel obtained in this example has a density of 0.099g/cm 3, a porosity of 95.9%, a specific surface area of 89m 2/g and an average pore size of 22.2nm. From the analysis of performance, the PVDF has a gas deformation amount up to 84.3%, a corresponding ultimate strength of 817kPa, a thermal conductivity of 0.3369/(mK) and a hydrophobic angle of 136.2 °.
Example 8
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving 2g PVDF polymer powder with the relative molecular mass of 60 ten thousand in 18ml dimethyl sulfoxide under rapid stirring at 120 ℃ to form highly viscous liquid;
S2, dispersing 2.8ml of deionized water in 32ml of dimethyl sulfoxide to prepare a PVDF bonding inducer;
S3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at the dripping speed of 1.0ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement, wherein the replacement liquid is isopropanol, the volume of the replacement liquid is 6 times of that of the PVDF wet gel, the replacement times are 5 times, and the single replacement time is 5 hours;
S5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking the pressure maintaining for 1h and 1.2h as a drying cycle, and totally drying for 5 cycles, wherein the drying temperature is 75 ℃, the drying pressure is 16MPa, and the exhaust rate is 2.5L/min.
Structurally, the PVDF aerogel obtained in this example has a density of 0.067g/cm 3, a porosity of 98.2%, a specific surface area of 59m 2/g and an average pore size of 37.1nm. From the analysis of performance, the gas deformation amount of the PVDF is up to 80.2%, the corresponding ultimate strength is 266kPa, the heat conductivity is 0.3031/(m.K) and the hydrophobic angle is 127.5 degrees.
Example 9
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving 2g of a PVDF polymer powder with a relative molecular mass of 80 ten thousand of a type of soft6010 in 16ml of triethyl phosphate under rapid stirring at 95 ℃ to form highly viscous liquid;
S2, dispersing 0.8ml of deionized water in 15ml of triethyl phosphate to prepare a PVDF bonding inducer;
S3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at the dripping speed of 1.0ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a displacement liquid for solvent displacement, wherein the displacement liquid is ethanol, the volume of the displacement liquid is 7 times of that of the PVDF wet gel, the displacement times are 5 times, and the single displacement time is 9 hours;
S5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking the pressure maintaining for 0.8h and 1.2h as a drying cycle, and totally drying for 5 cycles, wherein the drying temperature is 80 ℃, the drying pressure is 15MPa, and the exhaust rate is 2.6L/min.
Structurally, the PVDF aerogel obtained had a density of 0.091g/cm 3, a porosity of 95.7%, a specific surface area of 72m 2/g and an average pore size of 21.4nm. From the analysis of performance, the gas deformation amount of the PVDF is up to 82.7%, the corresponding ultimate strength is 813kPa, the heat conductivity is 0.3685/(m.K) and the hydrophobic angle is 132.2 degrees.
Example 10
A simple preparation method of high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel comprises the following steps:
S1, dissolving 2g of PVDF high molecular powder with the relative molecular mass of 100 ten thousand of HS7611A into 24ml of N-methylpyrrolidone under rapid stirring at 80 ℃ to form highly viscous liquid;
s2, dispersing 1.3ml of deionized water in 10ml of N-methylpyrrolidone to prepare a PVDF bonding inducer;
s3, uniformly and rapidly dripping the PVDF adhesive inducer into the viscous liquid under the rapid stirring in the S1 at the dripping speed of 2.8ml/min, and stopping stirring immediately after the dripping is finished to form PVDF wet gel;
S4, after the PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement, wherein the replacement liquid is methanol, the volume of the replacement liquid is 10 times of that of the PVDF wet gel, the replacement times are 4 times, and the single replacement time is 10 hours;
s5, placing the PVDF wet gel after the replacement in a supercritical drying kettle, and performing intermittent CO 2 drying for a plurality of cycles to prepare PVDF aerogel; and (3) taking the pressure maintaining for 1.5 hours and the pressure maintaining for 0.5 hour as a drying cycle, and totally drying for 7 cycles, wherein the drying temperature is 70 ℃, the drying pressure is 12MPa, and the exhaust rate is 2.5L/min.
Structurally, the PVDF aerogel obtained in this example has a density of 0.074g/cm 3, a porosity of 97.7%, a specific surface area of 71m 2/g and an average pore size of 28.8nm. From the analysis of performance, the gas deformation amount of the PVDF is as high as 83.5%, the corresponding ultimate strength is 526kPa, the heat conductivity is 0.3031/(m.K) and the hydrophobic angle is 130.1 degrees.
Those of ordinary skill in the art will recognize that the embodiments described herein are for the purpose of aiding the reader in understanding the principles of the present invention and should be understood that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit thereof, and such modifications and combinations remain within the scope of the present disclosure.
Claims (3)
1. The simple preparation method of the high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel is characterized by comprising the following steps of:
S1, dissolving PVDF polymer powder in a solvent under rapid stirring to form highly viscous liquid; the solvent is N-methyl pyrrolidone, triethyl phosphate or dimethyl sulfoxide; the dosage ratio of PVDF polymer powder to solvent is 1g: (8-12) ml; the PVDF high polymer powder is of an Akema HSV type, solef type or Shanghai Sanai Fu FR type, the relative molecular mass is 60-100 ten thousand, and the dissolution temperature is 80-120 ℃;
s2, dispersing deionized water in the same solvent as that in the S1 to prepare a PVDF bonding inducer; the volume ratio of deionized water to solvent is (0.8-1.3): (10-15);
S3, uniformly and rapidly dripping the PVDF bonding inducer into the viscous liquid under rapid stirring in the S1, and immediately stopping stirring when the dripping is finished; the dropping speed of the PVDF bonding inducer is 1-3 ml/min;
s4, after PVDF wet gel is formed, placing the PVDF wet gel into a replacement liquid for solvent replacement;
s5, intermittent supercritical CO 2 drying of a plurality of cycles is carried out on the PVDF wet gel after the replacement is finished, and the PVDF aerogel is prepared.
2. The simple preparation method of the high-plasticity superhydrophobic low-heat-conductivity PVDF aerogel according to claim 1, wherein the replacement liquid in the step S4 is methanol, ethanol or acetone, the volume of the replacement liquid is 6-10 times of that of PVDF wet gel, the replacement times are 3-5 times, and the single replacement time is 5-10 hours.
3. The simple preparation method of the high-plasticity super-hydrophobic low-heat-conductivity PVDF aerogel according to claim 1, wherein in the step S5, the exhaust time is 0.8-1.5 h and the pressure maintaining time is 0.5-1.2 h, the total drying time is 5-7 cycles, the drying temperature is 60-80 ℃, the drying pressure is 12-16 MPa, and the exhaust rate is 1.6-2.8L/min.
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