CN114854062A - Preparation method of regenerated cellulose/graphene nanosheet membrane - Google Patents
Preparation method of regenerated cellulose/graphene nanosheet membrane Download PDFInfo
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- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 96
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 94
- 239000004627 regenerated cellulose Substances 0.000 title claims abstract description 82
- 239000002135 nanosheet Substances 0.000 title claims abstract description 77
- 239000012528 membrane Substances 0.000 title claims abstract description 16
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims abstract description 46
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000004202 carbamide Substances 0.000 claims abstract description 29
- IMQLKJBTEOYOSI-GPIVLXJGSA-N Inositol-hexakisphosphate Chemical compound OP(O)(=O)O[C@H]1[C@H](OP(O)(O)=O)[C@@H](OP(O)(O)=O)[C@H](OP(O)(O)=O)[C@H](OP(O)(O)=O)[C@@H]1OP(O)(O)=O IMQLKJBTEOYOSI-GPIVLXJGSA-N 0.000 claims abstract description 22
- IMQLKJBTEOYOSI-UHFFFAOYSA-N Phytic acid Natural products OP(O)(=O)OC1C(OP(O)(O)=O)C(OP(O)(O)=O)C(OP(O)(O)=O)C(OP(O)(O)=O)C1OP(O)(O)=O IMQLKJBTEOYOSI-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229940068041 phytic acid Drugs 0.000 claims abstract description 22
- 235000002949 phytic acid Nutrition 0.000 claims abstract description 22
- 239000000467 phytic acid Substances 0.000 claims abstract description 22
- 238000000034 method Methods 0.000 claims abstract description 17
- 238000002156 mixing Methods 0.000 claims abstract description 15
- 239000000126 substance Substances 0.000 claims abstract description 15
- 238000002791 soaking Methods 0.000 claims abstract description 13
- 238000004132 cross linking Methods 0.000 claims abstract description 11
- LRWZZZWJMFNZIK-UHFFFAOYSA-N 2-chloro-3-methyloxirane Chemical compound CC1OC1Cl LRWZZZWJMFNZIK-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000000498 ball milling Methods 0.000 claims abstract description 8
- 230000015271 coagulation Effects 0.000 claims abstract description 4
- 238000005345 coagulation Methods 0.000 claims abstract description 4
- 238000010382 chemical cross-linking Methods 0.000 claims abstract description 3
- 239000000243 solution Substances 0.000 claims description 71
- 238000003756 stirring Methods 0.000 claims description 35
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- 239000002064 nanoplatelet Substances 0.000 claims description 16
- 238000007710 freezing Methods 0.000 claims description 14
- 230000008014 freezing Effects 0.000 claims description 14
- 239000000499 gel Substances 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 230000001112 coagulating effect Effects 0.000 claims description 8
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 8
- 229920000742 Cotton Polymers 0.000 claims description 7
- 239000000017 hydrogel Substances 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 2
- 239000011259 mixed solution Substances 0.000 claims description 2
- 238000007789 sealing Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 229920000875 Dissolving pulp Polymers 0.000 abstract 1
- 239000002131 composite material Substances 0.000 description 16
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 8
- 239000000463 material Substances 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 229920002678 cellulose Polymers 0.000 description 4
- 239000001913 cellulose Substances 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- BRLQWZUYTZBJKN-UHFFFAOYSA-N Epichlorohydrin Chemical compound ClCC1CO1 BRLQWZUYTZBJKN-UHFFFAOYSA-N 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 239000002121 nanofiber Substances 0.000 description 3
- 239000000725 suspension Substances 0.000 description 2
- 238000003828 vacuum filtration Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000002113 nanodiamond Substances 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000001338 self-assembly Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
- C08J3/243—Two or more independent types of crosslinking for one or more polymers
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- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/04—Oxycellulose; Hydrocellulose
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
- C08K3/042—Graphene or derivatives, e.g. graphene oxides
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a preparation method of a regenerated cellulose/graphene nanosheet membrane. The method comprises the steps of firstly dissolving cellulose in urea/LiOH solution at low temperature to prepare regenerated cellulose solution, preparing graphene nanosheet solution by wet ball milling, then blending the regenerated cellulose solution and the graphene nanosheet solution, adding epoxy chloropropane for chemical crosslinking, then stretching chemical gel, and soaking in phytic acid coagulation bath for physical crosslinking to finally obtain the regenerated cellulose/graphene nanosheet membrane. The method adopts a physical and chemical double-crosslinking strategy and combines stretching to orient the graphene nanosheets, so that the prepared regenerated cellulose/graphene nanosheet film has high thermal conductivity, mechanical strength and toughnessDouble cross-linking and anisotropy, the product can be folded for 10000 times and the thermal conductivity can be improved to 33.145W m ‑1 K ‑1 。
Description
Technical Field
The invention relates to the technical field of heat management materials, and relates to a preparation method of a regenerated cellulose/graphene nanosheet film.
Background
With the high integration and the increasing miniaturization of electronic devices, a large amount of heat generated by electronic components inevitably affects the stability and the service life of the devices, and how to dissipate heat becomes an urgent problem to be solved. Thermal management materials generally have good thermal conductivity as well as processability. Compared with other heat-conducting composite materials, the film has higher in-plane heat conductivity and flexibility, can transmit heat out along a plane quickly, avoids heat accumulation of devices in the vertical direction, and provides a solution for heat dissipation of flexible electronic devices and wearable equipment due to good flexibility.
On one hand, under a certain content, the heat conducting performance of the composite material can be gradually improved along with the increase of the filling content of the heat conducting filler. On the other hand, the tensile strength and also the mechanical flexibility of the composite material are also deteriorated, which results in deterioration of the processability of the material. Cui SQ et al, which prepares a high thermal conductivity nanofibrillated cellulose mixed film based on nanodiamonds and graphene sheets by constructing a zero-dimensional, two-dimensional and one-dimensional layered structure through a vacuum filtration self-assembly process, can meet the mechanical requirements of flexible electronic devices, but the thermal conductivity is only 14.35 W.m -1 ·K -1 Cannot meet the heat conduction requirements of today' S highly integrated electronic devices (Cui S Q, Song N, Shi L Y, et al. enhanced Thermal Conductivity of biologically adsorbed Nanofibrated Cellulose fabrics and Nanodiams [ J. enhanced Thermal Conductivity of biologically adsorbed membranes on Graphene Sheets and nanotubes [ ]]ACS Sustainable chem. Eng.2020,8,16, 6363-. Therefore, a composite film with good thermal conductivity and excellent mechanical properties is urgently needed to be developed.
Disclosure of Invention
The present invention aims to provide a method for preparing a double-crosslinked and anisotropic Regenerated Cellulose (RC)/Graphene Nanoplatelet (GNP) film having high thermal conductivity, mechanical strength and toughness.
The technical solution for realizing the purpose of the invention is as follows:
the preparation method of the regenerated cellulose/graphene nanosheet membrane comprises the following steps:
step 1, preparing a regenerated cellulose solution and a graphene nanosheet solution:
(1) immersing cotton linter pulp into a urea/LiOH solution precooled to below-4 ℃, stirring until the temperature is 0 +/-2 ℃, then placing the solution in liquid nitrogen for quick freezing, and repeating the stirring and freezing procedures until the solution is clear and viscous to obtain a regenerated cellulose solution;
(2) under the condition of stirring, immersing the graphene nanosheets into a urea/LiOH solution, carrying out ball milling, and then freezing in liquid nitrogen to obtain a solidified graphene nanosheet solution;
according to the mass ratio of the phytic acid to the lithium chloride of 1-15: 1, mixing and dissolving phytic acid and lithium chloride in water to prepare 5 wt% phytic acid coagulating bath;
step 3, mixing the regenerated cellulose solution and the graphene nanosheet solution:
adding a graphene nanosheet solution into a regenerated cellulose solution, and stirring at 0-5 ℃ until the graphene nanosheet solution is uniformly mixed to obtain a regenerated cellulose/graphene nanosheet solution, wherein the mass of the graphene nanosheet is 30-50% of the total mass of the regenerated cellulose and the graphene nanosheet;
step 4, chemical crosslinking pre-stretching:
under stirring, adding Epoxy Chloropropane (ECH) into a regenerated cellulose/graphene nanosheet solution, stirring and mixing at 950 +/-50 rpm for 1-3 min, defoaming for 1-2 min, then extruding the mixed solution to form a film, sealing and isolating air, standing at 5-8 ℃ for 30 +/-6 h, and stretching the obtained chemical gel to be more than 100% of the original length;
and 5, physical crosslinking:
soaking the stretched chemical gel in 5 wt% phytic acid coagulating bath to obtain double-crosslinking regenerated cellulose/graphene nanosheet hydrogel;
and 6, removing impurities and drying:
soaking the double-crosslinked regenerated cellulose/graphene nanosheet hydrogel in water, removing redundant urea and phytic acid, and completely drying at room temperature to obtain the regenerated cellulose/graphene nanosheet membrane.
Preferably, in step 1(1), the concentration of the regenerated cellulose in the regenerated cellulose solution is 6 wt%.
Preferably, in step 1(1), the stirring speed is 950. + -. 50 rpm.
Preferably, in the step 1(2), the stirring speed is 500 +/-20 rpm, and the ball milling time is 2 +/-1 h.
Preferably, in step 1, the concentration of urea and the concentration of LiOH in the urea/LiOH solution are 4.6 wt% and 15 wt%.
Preferably, in step 3, the stirring speed is 950 ± 50 rpm.
Preferably, in step 3, the mass of the graphene nanoplatelets is 40% of the total mass of the regenerated cellulose and the graphene nanoplatelets.
Preferably, in step 4, the resulting chemical gel is stretched to 2 times its original length.
Because the heat conduction of the graphene nanosheets of the two-dimensional heat conduction material along the plane direction is far higher than that of the graphene nanosheets along the vertical direction, the graphene nanosheets are coated in the regenerated cellulose nanofiber crosslinking process, and the graphene nanosheets are forced to be arranged along the plane of the composite film under uniaxial stretching, so that high heat conduction is obtained, and meanwhile, the regenerated cellulose nanofiber can eliminate stress energy through the intermolecular hydrogen bond effect, so that high mechanical strength and toughness of the high-graphene nanosheets under load are ensured.
Compared with the prior art, the invention has the following advantages:
(1) the composite film matrix is constructed by simply physically dissolving renewable cellulose, and a fibrous structure is regenerated under the condition of not consuming a large amount of chemical reagents, so that the composite film matrix is a sustainable choice for the conformation of the heat-conducting paper-like material;
(2) compared with the conventional vacuum filtration strategy of assembling the nano-cellulose only through intermolecular hydrogen bond interaction, the double-crosslinking strategy of non-covalently bonding the adjacent regenerated cellulose by the regenerated cellulose nano-fibers through hydrogen bonds can not only effectively dredge the fibers and prevent any mechanical fracture through the interaction of partial chemical bonds, but also eliminate stress energy through the sacrifice bond of the non-covalent hydrogen bond interaction, thereby ensuring higher mechanical strength and toughness under the load of the high-graphene nano-sheets;
(3) the graphene subjected to uniaxial stretching is oriented more completely in the plane, and the heat conducting property of the composite film is improved.
Drawings
Fig. 1 is a graph of results of rheological tests on regenerated cellulose, regenerated cellulose/graphene nanoplatelets, and regenerated cellulose/graphene nanoplatelets/epichlorohydrin suspensions.
Fig. 2 shows the thermal conductivity of a regenerated cellulose/graphene nanosheet film having a graphene nanosheet content of 20 wt% at different stretch ratios.
Fig. 3 is the stress strain at 200% tension for regenerated cellulose/graphene nanoplatelet films of different graphene nanoplatelet content.
Fig. 4 is the thermal conductivity at 200% stretch of regenerated cellulose/graphene nanoplatelet films of different graphene nanoplatelet content.
Detailed Description
The present invention will be described in more detail with reference to the following examples and the accompanying drawings.
In the present invention, reference is made to the preparation of regenerated cellulose solutions [ Wang S, Lu A, Zhang L N Recent Advances in regenerated cellulose materials [ J ]. Progress in Polymer science.2016,2,169-206 ].
Example 1
(1) Under the stirring condition of 500rpm, 4.42g of graphene nanosheet is immersed in 30g of urea/LiOH solution, ball-milled in a zirconia container for 2 hours, and the obtained graphene nanosheet solution is frozen to 0 ℃.
(2) 1.2g of cotton linter pulp was immersed in 20g of urea/LiOH solution (urea 4.6 wt%, LiOH 15 wt%) pre-cooled to-12 ℃ and stirred at 950rpm until the temperature reached 5 ℃, then it was flash frozen in liquid nitrogen and diluted to 6 wt%. The stirring and freezing procedure was repeated until the solution was clear and viscous, yielding a regenerated cellulose solution.
(3) Uniformly blending the graphene nanosheet solution and the regenerated cellulose solution at 950rpm, adding 0.222g of epoxy chloropropane, uniformly stirring, stirring and mixing at 950rpm for 2min, defoaming for 2min, pouring into a mold frame with the thickness of 1mm, and refrigerating at 5-8 ℃ for 30 h. The resulting chemical gel was stretched 2-fold.
(4) And soaking the stretched chemical gel in a 5 wt% phytic acid coagulating bath for 30min, taking out, soaking in deionized water for 48h (changing water every 12 h), removing residual urea and phytic acid, taking out, drying at room temperature for 2 days, and completely drying in an oven at 80 ℃ for 3h to obtain the regenerated cellulose/graphene nanosheet membrane.
The prepared regenerated cellulose/graphene nanosheet membrane has excellent mechanical flexibility, and can be folded for 10000 times and still be intact. The in-plane and out-of-plane thermal diffusivity of the sample, as measured by a flash thermal conductivity analyzer (Netzsch LFA 467) at 250V voltage and 300 μ s pulsewidth, was 33.145W m for its in-plane thermal conductivity -1 K -1 。
Comparative example 1
Preparing a pure physical crosslinking and prestretching-free composite film:
(1) under the stirring condition of 500rpm, ball-milling 4.42g of graphene nanosheet and 30g of urea/LiOH solution in a zirconia container for 2 hours to obtain a graphene nanosheet solution, and freezing to 0 ℃.
(2) 1.2g of cotton linter pulp was immersed in 20g of urea/LiOH solution (urea 4.6 wt%, LiOH 15 wt%) pre-cooled to-12 ℃ and stirred at 950rpm until the temperature reached 5 ℃, then it was flash frozen in liquid nitrogen and diluted to 6 wt%. The stirring and freezing procedure was repeated until the solution was clear and viscous, yielding a regenerated cellulose solution.
(3) Uniformly blending the graphene nanosheet solution and the regenerated cellulose solution at 950rpm, forming a film from the blended solution under a film scraper with the height of 1mm, soaking in a 5 wt% phytic acid coagulating bath for 30min, taking out, soaking in deionized water for 48h (changing water every 12 h) to remove residual urea and phytic acid, taking out, drying at room temperature for 2 days, and then putting in an oven with the temperature of 80 ℃ for 3h for complete drying to obtain the regenerated cellulose/graphene nanosheet composite film.
The prepared regenerated cellulose/graphene nanosheet composite film cannot be folded. The in-plane and out-of-plane thermal diffusivity of the sample, as measured by a flash thermal conductivity analyzer (Netzsch LFA 467) at 250V voltage and 300 μ s pulsewidth, was 4.325W m for its in-plane thermal conductivity -1 K -1 。
Comparing example 1 with comparative example 1, it can be seen that compared with the regenerated cellulose/graphene nanosheet composite film which is merely physically crosslinked and has no pre-stretching, the thermal conductivity of the regenerated cellulose/graphene nanosheet film which is doubly crosslinked and has 200% stretching is improved by more than 7 times, and the regenerated cellulose/graphene nanosheet composite film is still intact after being repeatedly folded for 10000 times and has excellent mechanical flexibility.
Example 2
(1) Under the stirring condition of 500rpm, ball-milling 4.42g of graphene nanosheet and 30g of urea/LiOH solution in a zirconia container for 2 hours to obtain a graphene nanosheet solution, and freezing to 0 ℃.
(2) 1.2g of cotton linter pulp was immersed in 20g of urea/LiOH solution (urea 4.6 wt%, LiOH 15 wt%) pre-cooled to-12 ℃ and stirred at 950rpm until the temperature reached 5 ℃, then it was flash frozen in liquid nitrogen and diluted to 6 wt%. The stirring and freezing procedure was repeated until the solution was clear and viscous, yielding a regenerated cellulose solution.
(3) Uniformly blending the graphene nanosheet solution and the regenerated cellulose solution at 950rpm, adding 0.222g of epoxy chloropropane, uniformly stirring, stirring and mixing at 950rpm for 2min, defoaming for 2min, pouring into a mold frame with the thickness of 1mm, and refrigerating at 5-8 ℃ for 30 h. The resulting chemical gel was stretched 1-fold.
(4) And soaking the stretched chemical gel in a 5 wt% phytic acid coagulating bath for 30min, taking out, soaking in deionized water for 48h (changing water every 12 h) to remove residual urea and phytic acid, taking out, drying at room temperature for 2 days, and putting in an oven at 80 ℃ for 3h for complete drying to obtain the regenerated cellulose/graphene nanosheet membrane.
The prepared regenerated cellulose/graphene nanosheet membrane has excellent mechanical flexibility, and can be folded for 10000 times and still be intact. The in-plane and out-of-plane thermal diffusivity of the sample was measured by a scintillation thermal conductivity analyzer (Netzsch LFA 467) at 250V voltage and 300 μ s pulsewidth and tested to have a thermal conductivity of 15.423W m along the plane -1 K -1 。
Comparative example 2
Preparation of pure regenerated cellulose membrane:
(1) 0.9g of cotton linter pulp was immersed in 20g of urea/LiOH solution (urea 4.6 wt%, LiOH 15 wt%) pre-cooled to-12 ℃ and stirred at 950rpm until the temperature reached 5 ℃, then it was flash frozen in liquid nitrogen and diluted to 4.5 wt%. The stirring and freezing procedure was repeated until the solution was clear and viscous, yielding a regenerated cellulose solution.
(2) Adding 0.166g of epoxy chloropropane into the regenerated cellulose solution, uniformly stirring, stirring and mixing at 950rpm for 2min, defoaming for 2min, pouring into a mold frame with the thickness of 1mm, and refrigerating at 5-8 ℃ for 30 hours. The resulting chemical gel was stretched 2 times.
(3) And soaking the stretched chemical gel in a 5 wt% phytic acid coagulating bath for 30min, taking out, soaking in deionized water for 48h (changing water every 12 h) to remove residual urea and phytic acid, taking out, drying at room temperature for 2 days, and putting in an 80 ℃ oven for 3h for complete drying to obtain the pure regenerated cellulose membrane.
The prepared pure regenerated cellulose membrane has excellent mechanical flexibility, and can be folded for 10000 times and still be intact. The in-plane and out-of-plane thermal diffusivity of the sample, as measured by a flash thermal conductivity analyzer (Netzsch LFA 467) at 250V voltage and 300 μ s pulsewidth, was 1.914W m for its in-plane thermal conductivity -1 K -1 。
As can be seen from the comparison of the examples and comparative example 2, the regenerated cellulose/graphene nanosheet film, which is chemically crosslinked with epichlorohydrin and physically crosslinked with a phytic acid coagulation bath and stretched by 200%, has significantly improved thermal conductivity as compared to a pure regenerated cellulose film.
Comparative example 3
(1) Under the stirring condition of 500rpm, ball-milling 4.42g of graphene nanosheet and 30g of urea/LiOH solution in a zirconia container for 2 hours to obtain a graphene nanosheet solution, and freezing to 0 ℃.
(2) 1.2g of cotton linter pulp was immersed in 20g of urea/LiOH solution (urea 4.6 wt%, LiOH 15 wt%) pre-cooled to-12 ℃ and stirred at 950rpm until the temperature reached 5 ℃, then it was flash frozen in liquid nitrogen and diluted to 6 wt%. The stirring and freezing procedure was repeated until the solution was clear and viscous, yielding a regenerated cellulose solution.
(3) Uniformly blending the graphene nanosheet solution and the regenerated cellulose solution at 950rpm, adding 0.222g of epoxy chloropropane, uniformly stirring, stirring and mixing at 950rpm for 4min, defoaming for 2min, and forming a gel state due to the increase of crosslinking time, so that the film cannot be extruded to form.
As can be seen from fig. 1, with the increase of the oscillation strain, the loss modulus of the regenerated cellulose solution and the regenerated cellulose/graphene nanosheet suspension is higher than the storage modulus and is in a liquid-like state, while the regenerated cellulose/graphene nanosheet/epichlorohydrin composite material is opposite in performance and is in a gel-like state, further proving the formation of the chemically crosslinked gel.
As can be seen from fig. 2, for the graphene nanoplatelets based thermal conductive material, the orientation arrangement of the graphene nanoplatelets in the matrix has a great influence on the thermal conductivity. Therefore, as the pre-stretching is increased, the thermal conductivity of the double-crosslinked regenerated cellulose/graphene nano sheet film is from 4.325W m -1 K -1 Increased to 33.145W m -1 K -1 Is 6 times higher than the film without pre-stretching.
As can be seen from fig. 3, the strength of the 10 wt% regenerated cellulose/graphene nanosheet film is 113MPa, the strength of the 30 wt% regenerated cellulose/graphene nanosheet film is reduced to 65MPa, and the strength of the 50 wt% regenerated cellulose/graphene nanosheet film is further reduced to 42MPa, the increase of the content of the graphene nanosheets is negatively related to the mechanical property of the composite film, and the loading amount of the graphene nanosheets is reduced when the mechanical property of the composite film is increased.
As can be seen from fig. 4, the thermal conductivities of the regenerated cellulose/graphene nanosheet films with 0 wt%, 10 wt%, 20 w%, 30 wt%, 40 wt%, and 50 wt% graphene nanosheet contents are 1.914W m respectively -1 K -1 、8.745W m -1 K -1 、17.376W m -1 K -1 、28.142W m -1 K -1 、33.145W m -1 K -1 、27.785W m -1 K -1 The thermal conductivity increases with increasing loading of the graphene nanoplatelets, but a downward trend occurs at 50 wt% because the degree of orientation begins to decrease with increasing loading of the graphene nanoplatelets, so the higher the loading of the graphene nanoplatelets is not the better.
Claims (8)
1. The preparation method of the regenerated cellulose/graphene nanosheet membrane is characterized by comprising the following steps:
step 1, preparing a regenerated cellulose solution and a graphene nanosheet solution:
(1) immersing cotton linter pulp into a urea/LiOH solution precooled to below-4 ℃, stirring until the temperature is 0 +/-2 ℃, then placing the solution in liquid nitrogen for quick freezing, and repeating the stirring and freezing procedures until the solution is clear and viscous to obtain a regenerated cellulose solution;
(2) under the condition of stirring, immersing the graphene nanosheets into a urea/LiOH solution, carrying out ball milling, and then freezing in liquid nitrogen to obtain a solidified graphene nanosheet solution;
step 2, preparation of phytic acid coagulation bath:
according to the mass ratio of the phytic acid to the lithium chloride of 1-15: 1, mixing and dissolving phytic acid and lithium chloride in water to prepare 5 wt% phytic acid coagulating bath;
step 3, mixing the regenerated cellulose solution and the graphene nanosheet solution:
adding a graphene nanosheet solution into a regenerated cellulose solution, and stirring at 0-5 ℃ until the graphene nanosheet solution is uniformly mixed to obtain a regenerated cellulose/graphene nanosheet solution, wherein the mass of the graphene nanosheet is 30-50% of the total mass of the regenerated cellulose and the graphene nanosheet;
step 4, chemical crosslinking pre-stretching:
under stirring, adding Epoxy Chloropropane (ECH) into a regenerated cellulose/graphene nanosheet solution, stirring and mixing at 950 +/-50 rpm for 1-3 min, defoaming for 1-2 min, then extruding the mixed solution to form a film, sealing and isolating air, standing at 5-8 ℃ for 30 +/-6 h, and stretching the obtained chemical gel to be more than 100% of the original length;
and 5, physical crosslinking:
soaking the stretched chemical gel in 5 wt% phytic acid coagulating bath to obtain double-crosslinking regenerated cellulose/graphene nanosheet hydrogel;
and 6, removing impurities and drying:
soaking the double-crosslinked regenerated cellulose/graphene nanosheet hydrogel in water, removing redundant urea and phytic acid, and completely drying at room temperature to obtain the regenerated cellulose/graphene nanosheet membrane.
2. The method according to claim 1, wherein in step 1(1), the concentration of the regenerated cellulose in the regenerated cellulose solution is 6 wt%.
3. The method according to claim 1, wherein in step 1(1), the stirring speed is 950 ± 50 rpm.
4. The preparation method according to claim 1, wherein in the step 1(2), the stirring speed is 500 plus or minus 20rpm, and the ball milling time is 2 plus or minus 1 h.
5. The method according to claim 1, wherein in step 1, the concentration of urea is 4.6 wt% and the concentration of LiOH is 15 wt% in the urea/LiOH solution.
6. The method according to claim 1, wherein the stirring speed in step 3 is 950 ± 50 rpm.
7. The production method according to claim 1, wherein in step 3, the mass of the graphene nanoplatelets is 40% of the total mass of the regenerated cellulose and the graphene nanoplatelets.
8. The method of claim 1, wherein in step 4, the resulting chemical gel is stretched to 2 times its original length.
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