CN114606763A - Electromagnetic shielding film based on carbon nanotube composite waterborne polyurethane - Google Patents
Electromagnetic shielding film based on carbon nanotube composite waterborne polyurethane Download PDFInfo
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- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 43
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- UPMLOUAZCHDJJD-UHFFFAOYSA-N 4,4'-Diphenylmethane Diisocyanate Chemical compound C1=CC(N=C=O)=CC=C1CC1=CC=C(N=C=O)C=C1 UPMLOUAZCHDJJD-UHFFFAOYSA-N 0.000 description 2
- -1 aromatic isocyanate Chemical class 0.000 description 2
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Classifications
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- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M11/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising
- D06M11/73—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with carbon or compounds thereof
- D06M11/74—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with carbon or compounds thereof with carbon or graphite; with carbides; with graphitic acids or their salts
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/0083—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising electro-conductive non-fibrous particles embedded in an electrically insulating supporting structure, e.g. powder, flakes, whiskers
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M2101/00—Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
- D06M2101/16—Synthetic fibres, other than mineral fibres
- D06M2101/30—Synthetic polymers consisting of macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- D06M2101/38—Polyurethanes
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Textile Engineering (AREA)
- Carbon And Carbon Compounds (AREA)
- Artificial Filaments (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
The invention relates to the field of membrane materials, and discloses an electromagnetic shielding film based on carbon nano tube composite waterborne polyurethane. According to the invention, the waterborne polyurethane prepolymer is prepared by a prepolymer mixing method, then is directly emulsified in water and is subjected to chain growth to prepare stable waterborne polyurethane, waterborne polyurethane emulsion (WPU) is used as a spinning solution, and the WPU nanofiber film prepared by electrostatic spinning has higher conductivity, good mechanical property and excellent electromagnetic interference shielding property; and then loading CNTs on the surface of the WPU nanofiber film by utilizing vacuum impregnation and ultrasonic assistance to form a conductive composite film for electromagnetic interference shielding.
Description
Technical Field
The invention relates to the field of membrane materials, in particular to an electromagnetic shielding film based on carbon nano tube composite waterborne polyurethane.
Background
Carbon nanotubes are tubular nano-scale graphite crystals formed by bending one or more layers of graphene sheets around a central axis at a certain helical angle. Carbon nanotubes can be classified into single-walled carbon nanotubes and multi-walled carbon nanotubes according to the number of graphene layers thereof. The diameter of the single-walled carbon nanotube is generally 0.4-3nm, the multi-walled carbon nanotube is a coaxial tube rolled by a plurality of graphene sheets, the interval between each sheet layer is 0.34nm, the stability of the structure is kept by the attraction of van der waals force, and the total diameter can reach 100 nm. The carbon nanotubes have a large length-diameter ratio of 1000-10000: 1, are true one-dimensional materials, can form a network structure in a matrix material, can resist tensile load, enhance the mechanical strength of the composite material, and can endow the composite material with special physical properties, such as change of insulativity, heat insulation and the like of the matrix material.
In the preparation of composite materials, the addition of one material as a filler to another material system is one of the most common means. Depending on the size of the filler, it can be classified into macroscopic fillers and nanofillers. The macro filler can destroy the continuity of the matrix material due to its large size, and has very adverse effect on the mechanical properties and the processability of the composite material. In this case, it is necessary to reduce the size of the filler. Once the diameter of the filler is changed to the nanometer level, the properties of the composite material are changed significantly, and even in the case of a small amount of the filler (less than 5%), the mechanical and physical properties of the composite material can be improved to a great extent. Carbon Nanotubes (CNTs), as a novel one-dimensional carbon allotrope, have low density, large aspect ratio, good mechanical strength and high electrical conductivity, and are excellent functional fillers for shielding materials.
Polyurethane was first synthesized by Otto Bayer, a German scientist, in the last 40 th century, and through the development of decades, polyurethane is widely applied to the fields of buildings, aviation, leather and the like by virtue of excellent properties such as flexibility, wear resistance, corrosion resistance, strong adhesion and the like. The polyurethane is formed by repeated urethane bonds (-NHCOO-) formed by polyisocyanate and polymer polyol (including polyether polyol and polyester polyol) with the aid of a dispersing agent and other additives, and the reaction raw materials of the polyurethane are not unique, and in the case of isocyanate, tens of types such as Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and the like exist. It is worth mentioning that the monomers of the polyurethane can be simplified to polyisocyanates and polyols, which generally have longer chain lengths, which promote the flowability of the polyurethane; polyisocyanates are generally very short, exhibit higher crystallinity, and produce dense and stacked segments, so that the ratio of polyol and polyisocyanate can be controlled to produce both soft elastomers and hard metal-like products, so that polyurethane products are widely varied and used in a wide range of applications, and polyol and polyisocyanate are also visually referred to as soft and hard segments of polyurethane. The WPU emulsion is adopted as a polymer matrix, and has environmental protection and excellent elastic property. WPU is selected as the polymer matrix, and a film with a certain thickness can be obtained in consideration of the advantages of environmental protection and easy processing. The fiber film can recover quickly after being unloaded, has the characteristics of high elongation at break, high elasticity and low modulus, and has higher heat conduction/electric conductivity, good mechanical property and excellent electromagnetic interference shielding property. The elastic property of the WPU enables the WPU to have excellent flexibility and stretchability, and the WPU is expected to become a composite material for commercial electromagnetic interference shielding.
Disclosure of Invention
The invention provides an electromagnetic shielding film based on carbon nano tube composite waterborne polyurethane. The invention prepares the waterborne polyurethane prepolymer by a prepolymer mixing method, then directly emulsifies the waterborne polyurethane prepolymer in water and simultaneously carries out chain growth to prepare stable waterborne polyurethane, and the waterborne polyurethane emulsion (WPU) is used as spinning solution, and the WPU nano-fiber film prepared by electrostatic spinning has higher conductivity, good mechanical property and excellent electromagnetic interference shielding property; then, the CNTs are loaded on the surface of the WPU nanofiber film by utilizing vacuum impregnation and ultrasonic assistance, so that a conductive composite film for shielding electromagnetic interference is formed.
The specific technical scheme of the invention is as follows: an electromagnetic shielding film based on carbon nanotube composite waterborne polyurethane is prepared by the following steps:
(1) preparation of WPU solution: placing polyether 3050 in a container, dehydrating at high temperature in vacuum, cooling after water is completely removed, adding 2, 2-dimethylolpropionic acid (DMPA) and Toluene Diisocyanate (TDI) into the system while stirring, and carrying out prepolymerization reaction by vigorously stirring in an inert atmosphere to obtain a prepolymer; cooling, adding triethylamine for neutralization reaction to neutralize carboxylic acid group in prepolymer, and then adding Na2SO3And emulsifying with water under vigorous stirring to obtain WPU solution.
According to the invention, Toluene Diisocyanate (TDI) and polyether are selected as initial synthetic raw materials, and the synthesized polyurethane has good film-forming property and can be firmly combined with fiber molecules.
TDI as the aromatic isocyanate has the advantages of difficult oxidation, high activity ratio and reaction activity far greater than that of aliphatic isocyanates. the-NCO groups in the aromatic diisocyanate mutually generate an induction effect to promote the reaction activity of the diisocyanate to be increased.
The polyether contains three functional groups, has a good space structure, and can be well combined with fiber molecules to form a membrane. The polyether polyurethane has better flexibility and excellent low-temperature performance because the ether group of the soft segment is easier to rotate, and the hydrolysis resistance of the polyether polyurethane is better than that of polyester type because the polyether does not have an ester group which is relatively easy to hydrolyze. Since the polymeric polyols generally contain a small amount of moisture, the presence of moisture causes TDI to undergo side reactions, consuming-NCO groups in the system, forming ureido compounds, increasing the degree of branching of the product and possibly causing gelation. Therefore, the polyhydric alcohol must be dehydrated before the prepolymerization reaction to reduce the occurrence of side reactions.
-NCO group and H2O and Na2SO3The rate ratio of the reaction was 1:500000, indicating Na2SO3Ratio of H to H2O has a greater nucleophilicity. The polyurethane prepolymer is processed by Na2SO3After end capping, it becomes an anionic polymer, so that it has good water contentAnd (4) dissolving.
The stability of the synthesized anionic waterborne polyurethane has a great relationship with the neutralization degree. When the neutralization degree is increased to 100 percent, the-COOH in the 2, 2-dimethylolpropionic acid (DMPA) is completely neutralized to form an ion center, and the function of stabilizing the latex is achieved. If the degree of neutralization exceeds the above range, the thickness of the adsorbent layer increases, the hydrodynamic volume of the particles increases, and the particle diameter increases, and the viscosity increases. Triethylamine is also an aggregating agent, free triethylamine molecules can be aggregated with polyurethane molecules, and the particle size of the polyurethane macromolecules is increased.
(2) Preparation of WPU nanofiber membrane: loading the WPU solution into an injector to be used as a spinning solution, and preparing the WPU nano-fiber film by an electrostatic spinning technology.
The electrostatic spinning technology has the advantages of simple device, controllable process, low cost and the like, and can prepare the nanofiber membrane with large specific surface area and high porosity.
(3) Preparation of CNTs dispersion: adding CNTs and sodium dodecyl benzene sulfonate into water, and performing ultrasonic treatment to obtain a uniformly dispersed CNTs dispersion liquid.
Sodium dodecyl benzene sulfonate is a commonly used anionic surfactant, is readily soluble in water, and dissolves in water to form a translucent solution. Stable chemical properties to alkali, dilute acid and hard water. Carbon Nanotubes (CNTs), as a novel one-dimensional carbon allotrope, have low density, large aspect ratio, good mechanical strength and high electrical conductivity, and are excellent functional fillers for shielding materials. The ultrasonic dispersion equipment is suitable for dispersing the carbon nanotubes in a low-viscosity medium in a laboratory scale, so that the CNTs dispersion liquid with good dispersity can be prepared by using the ultrasonic dispersion equipment.
(4) Preparing an electromagnetic shielding film: putting the WPU nanofiber film into a container, vacuumizing, injecting the CNTs dispersion liquid into the container, dipping the WPU nanofiber film in a vacuum environment, taking out, drying and curing, taking out, putting the WPU nanofiber film into another container filled with water, enhancing the bonding firmness of the CNTs on the fiber surface through ultrasonic assistance, finally cleaning with water, and drying to obtain the electromagnetic shielding film.
According to the invention, an impregnation method is adopted, so that on one hand, when pores of the WPU film are contacted with the CNTs dispersion liquid, capillary pressure is generated due to the action of surface tension, and liquid can permeate into the capillary; on the other hand, the active components of the CNTs dispersion can be effectively adsorbed on the surface of the WPU film. And the air in the carrier is pre-pumped, so that the impregnation amount or the impregnation depth can be increased. In conclusion, the impregnation method has high utilization rate, small using amount and low cost.
Preferably, in step (1):
the temperature of the high-temperature vacuum dehydration is 110-130 ℃, and the time is 2-3 h; the temperature of the prepolymerization reaction is 75-85 ℃, and the time is 2-8 h; the temperature of the neutralization reaction is 1-10 ℃ and the time is 5-15 min.
Calculated by g, the using amount of the polyether 3050 is 30-50g, the using amount of the 2, 2-dimethylolpropionic acid (DMPA) is 30-40g, the using amount of the Toluene Diisocyanate (TDI) is 3-8g, the using amount of the triethylamine is 1-5g, and Na2SO3The dosage of the composition is 2-5 g.
The R value is 1.5 and the consumption of the chain extender is 6 percent under the prepolymerization condition, the polyether 3050 and the Toluene Diisocyanate (TDI) are prepolymerized for 2 to 8 hours at the temperature of 75 to 85 ℃, and the prepolymer fully synthesized by the reaction under the condition has small viscosity and moderate molecular weight. The temperature of the end capping reaction is selected to be about 1-10 ℃, and the end capping agent is Na2SO3The blocking rate is highest. The temperature is increased, and side reactions are increased; the main reaction can not be protected for too long time, and the final end-capping rate is not greatly influenced.
Preferably, in step (1), the WPU solution has a solids content of from 35 to 45 wt%.
Preferably, in the step (2), the conditions of electrostatic spinning are as follows: the temperature is 20-30 ℃, the relative humidity is 20-30%, and the voltage is 15-20 kv; the specification of the metal needle tip for electrostatic spinning is 25-18G, the inner diameter is 0.3-0.4mm, and the outer diameter is 0.70-0.75 mm; the flux level of the spinning solution is 2-4 ml/h.
Preferably, in the step (3), the CNTs are used in an amount of 20-30mg, the sodium dialkylbenzenesulfonate is used in an amount of 100-150mg, and the water is used in an amount of 10-15ml, in terms of mg and ml.
Preferably, in the step (3), the ultrasonic power is 20-30% and the ultrasonic time is 20-30 min.
Preferably, in the step (4), the CNTs dispersion is injected in an amount of 20-30mg in mg, and the dipping time is 5-15 min.
Preferably, in the step (4), the drying conditions are as follows: 60-75 ℃ for 10-13 h; the ultrasonic treatment time is 10-15 min.
Compared with the prior art, the invention has the beneficial effects that:
the invention prepares the waterborne polyurethane prepolymer by a prepolymer mixing method, then directly emulsifies the waterborne polyurethane prepolymer in water and simultaneously carries out chain growth to prepare stable waterborne polyurethane, and the waterborne polyurethane emulsion (WPU) is used as spinning solution, and the WPU nano-fiber film prepared by electrostatic spinning has higher conductivity, good mechanical property and excellent electromagnetic interference shielding property; and then loading CNTs on the surface of the WPU nanofiber film by utilizing vacuum impregnation and ultrasonic assistance to form a conductive composite film for electromagnetic interference shielding. The composite film not only has good conductivity, but also can effectively shield electromagnetic interference, solve the problem of electromagnetic radiation to a great extent and reduce the electromagnetic pollution of electromagnetic waves to the surrounding environment and human bodies.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
1) Preparation of WPU solution: 30g of polyether 3050 was weighed and placed in a four-necked flask, vacuum dehydration was carried out at a high temperature of 110 ℃ for 2 hours, after the water was completely removed, a thermometer, a stirrer and a reflux condenser were installed on the flask, and when the temperature of the system was cooled to 75 ℃, 30g of 2, 2-dimethylolpropionic acid (DMPA) and 5g of Toluene Diisocyanate (TDI) were added to the system while stirring. By means of a magnetic stirring device in N2And violently stirring the mixture for reaction for 4 hours under the atmosphere to obtain a prepolymer. The change in NCO value during the reaction was determined by standard dibutylamine titration. The stoichiometric amount of BD was added dropwise and dissolved in 30ml of acetone C according to the NCO value determined in this way3H6O until the theoretical NCO content is reached. Using vacuum circulation coolingCooling the system, adding 3g triethylamine to react for 5min to neutralize the carboxylic acid group in the prepolymer at 3 deg.C for 5min, and adding 2g Na2SO3And vigorously stirring the mixture and pure distilled water, and performing an emulsification reaction to obtain a WPU solution with the solid content of 35 wt%.
2) Preparation of WPU nanofiber membrane: electrospinning of nanofibers was carried out on a magnetic field assisted electrospinning apparatus known as magneto-electrospinning (MES). A medical syringe was used to hold the WPU spinning solution, a temperature of 25 ℃ and a relative humidity of 25% were set at an electrospinning voltage of 15kv, and a metal needle tip connected to the positive electrode of a power source was used as a spinning tip. The metal tip for electrospinning had a gauge of 25G, an inner diameter of 0.3mm and an outer diameter of 0.70 mm. A piece of flat aluminum foil, connected to the negative pole of the power supply, was used as a collector for the electrospun fibers and was glued to the surface of the permanent magnet. The rotation distance is controlled by fixing a permanent magnet and a grounded aluminum foil to the distance adjuster. To avoid the droplets hanging vertically from the needle and the covering of spun nanofibers, the needle and collector were placed on the same horizontal line so that the droplets could move horizontally and parabolically under the action of gravity and they were separated from the electrospun nanofibers. The spinning solution reached the needle tip through a syringe, maintaining a spinning solution throughput of 2 ml/h. When the high voltage dc power supply is turned on, the droplet hanging on the needle tip is stretched by a combination of electricity and magnetic force. In the space between the tip and the aluminum foil, the droplets are stretched and refined, the solution evaporates, and the fibers are solidified. Finally, the nano-fiber WPU film with a certain thickness is deposited on the aluminum foil.
3) Preparation of CNTs dispersion: 20mg of CNTs are taken, 100mg of sodium dodecyl benzene sulfonate is weighed and added into 10ml of deionized water. And (2) carrying out ultrasonic treatment on the CNTs by using a cell crusher, setting the power to be 20%, and carrying out ultrasonic treatment for 20min to obtain a uniformly dispersed CNTs dispersion liquid.
4) Preparing a CNTs/WPU film: putting the WPU film into a vacuum bottle, pumping air by using a vacuum pump, injecting the CNTs dispersion liquid obtained in the step 3) into the vacuum bottle by using an injector, dipping the WPU film for 5min in a vacuum environment, taking out, putting into a blast oven, and putting the vacuum bottle into the blast oven for 70 minDrying and curing for 10h at the temperature of below zero, taking out the fiber, putting the fiber into a container filled with deionized water, performing ultrasonic assistance for 10min to enhance the firmness of the conductive substance on the surface of the fiber, finally cleaning the fiber with deionized water for several times, and drying the fiber to obtain the conductive CNTs/WPU film with the conductivity of 367.4 Sm−1The electromagnetic interference (EMI) Shielding Efficiency (SE) was 23.2dB and the elongation at break was 60%.
Example 2
1) Preparation of WPU solution: 40g of polyether 3050 was weighed and placed in a four-necked flask, and vacuum dehydration was performed at a high temperature of 120 ℃ for 2.5 hours until the water was completely removed, a thermometer, a stirrer and a reflux condenser were installed on the flask, and 35g of 2, 2-dimethylolpropionic acid (DMPA) and 6g of Toluene Diisocyanate (TDI) were added to the system while stirring when the temperature of the system was cooled to 80 ℃. By means of a magnetic stirring device in N2And (3) violently stirring and reacting for 6 hours under the atmosphere to obtain a prepolymer. The change in NCO value during the reaction was determined by standard dibutylamine titration. The stoichiometric amount of BD was added dropwise and dissolved in 35ml of acetone C according to the NCO value determined in this way3H6O until the theoretical NCO content is reached. Cooling by a vacuum circulating cooling system, adding 4g of triethylamine to react for 10min to neutralize carboxylic acid groups in the prepolymer, wherein the temperature of the neutralization reaction is 6 ℃, the time is 10min, and then adding 3g of Na2SO3And stirring with pure distilled water vigorously, and carrying out an emulsification reaction to obtain a WPU solution with the solid content of 40 wt%.
2) Preparation of WPU nanofiber membrane: electrospinning of nanofibers was carried out on a magnetic field assisted electrospinning apparatus known as magneto-electrospinning (MES). A medical syringe was used to hold the WPU spinning solution, a temperature of 20 ℃ and a relative humidity of 20% were set at an electrospinning voltage of 17kv, and a metal needle tip connected to the positive electrode of a power source was used as a spinning tip. The metal tip for electrospinning had a gauge of 22G, an inner diameter of 0.35mm and an outer diameter of 0.725 mm. A piece of flat aluminum foil, connected to the negative pole of the power supply, was used as a collector for the electrospun fibers and was glued to the surface of the permanent magnet. The rotation distance is controlled by fixing a permanent magnet and a grounded aluminum foil to the distance adjuster. To avoid the droplets hanging vertically from the needle and the covering of spun nanofibers, the needle and collector were placed on the same horizontal line so that the droplets could move horizontally and parabolically under the action of gravity and they were separated from the electrospun nanofibers. The spinning solution reached the needle tip through a syringe, maintaining a spinning solution throughput of 3 ml/h. When the high voltage dc power supply is turned on, the droplet suspended from the needle tip is stretched by a combination of electricity and magnetic force. In the space between the tip and the aluminum foil, the droplets are stretched and refined, the solution is evaporated, and the fibers are solidified. Finally, the nano-fiber WPU film with a certain thickness is deposited on the aluminum foil.
3) Preparation of CNTs dispersion liquid: 25mg of CNTs are taken, 125mg of sodium dodecyl benzene sulfonate is weighed and added into 12ml of deionized water. And (2) carrying out ultrasonic treatment on the CNTs by using a cell crusher, setting the power to be 25%, and carrying out ultrasonic treatment for 25min to obtain a uniformly dispersed CNTs dispersion liquid.
4) Preparing a CNTs/WPU film: putting the WPU film into a vacuum bottle, pumping air by using a vacuum pump, injecting the CNTs dispersion liquid obtained in the step 3) into the vacuum bottle by using an injector, dipping the WPU film in the vacuum environment for 10min, taking out, putting the WPU film into a blast oven, drying and curing at 60 ℃ for 10h, taking out, putting the WPU film into a container filled with deionized water, ultrasonically assisting for 11min, enhancing the firmness of conductive substances on the surface of fibers, finally washing the fiber surface for several times by using deionized water, and drying to obtain the conductive CNTs/WPU film, wherein the conductivity is 374.8 Sm−1Electromagnetic interference (EMI) Shielding Efficiency (SE) was 23.9dB, and elongation at break was 61%. .
Example 3
1) Preparation of WPU solution: 50g of polyether 3050 was weighed and placed in a four-necked flask, and vacuum dehydration was carried out at a high temperature of 130 ℃ for 3 hours until the water was completely removed, a thermometer, a stirrer and a reflux condenser were attached to the flask, and 40g of 2, 2-dimethylolpropionic acid (DMPA) and 7g of Toluene Diisocyanate (TDI) were added to the system while stirring when the temperature of the system was cooled to 85 ℃. By means of a magnetic stirring device in N2And violently stirring and reacting for 8 hours under the atmosphere to obtain a prepolymer. The change in NCO value during the reaction was determined by standard dibutylamine titration. The stoichiometric amount of BD was added dropwise and dissolved at 40m according to the NCO value determined by this methodl acetone C3H6O until the theoretical NCO content is reached. Cooling by a vacuum circulating cooling system, adding 5g of triethylamine for reaction for 15min to neutralize carboxylic acid groups in the prepolymer, wherein the temperature of the neutralization reaction is 9 ℃, the time is 15min, and then adding 4g of Na2SO3And vigorously stirring with pure distilled water, and carrying out an emulsification reaction to obtain a WPU solution with the solid content of 45 wt%.
2) Preparing a WPU nanofiber film: electrospinning of nanofibers was performed on a magnetic field assisted electrospinning apparatus, called a magneto-electrospinning (MES). A medical syringe was used to hold the WPU spinning solution, a temperature of 30 ℃ and a relative humidity of 30% were set at an electrospinning voltage of 19kv, and a metal needle tip connected to the positive electrode of a power source was used as a spinning tip. The metal tip for electrospinning had a gauge of 19G, an inner diameter of 0.4mm and an outer diameter of 0.75 mm. A piece of flat aluminum foil, connected to the negative pole of the power supply, was used as a collector for the electrospun fibers and was glued to the surface of the permanent magnet. The rotation distance is controlled by fixing a permanent magnet and a grounded aluminum foil to the distance adjuster. To avoid the droplets hanging vertically from the needle and the covering of spun nanofibers, the needle and collector were placed on the same horizontal line so that the droplets could move horizontally and parabolically under the action of gravity and they were separated from the electrospun nanofibers. The spinning solution reached the needle tip through a syringe, maintaining a spinning solution throughput of 4 ml/h. When the high voltage dc power supply is turned on, the droplet suspended from the needle tip is stretched by a combination of electricity and magnetic force. In the space between the tip and the aluminum foil, the droplets are stretched and refined, the solution is evaporated, and the fibers are solidified. Finally, depositing a nano-fiber WPU film with a certain thickness on the aluminum foil.
3) Preparation of CNTs dispersion: 30mgCNTs is taken, 150mg of sodium dodecyl benzene sulfonate is weighed and added into 14ml of deionized water. And (2) carrying out ultrasonic treatment on the CNTs by using a cell crusher, setting the power to be 30%, and carrying out ultrasonic treatment for 30min to obtain a uniformly dispersed CNTs dispersion liquid.
4) Preparing a CNTs/WPU film: putting the WPU film into a vacuum bottle, pumping air by using a vacuum pump, and injecting the CNTs dispersion liquid obtained in the step 3) into vacuum by using an injectorSoaking the WPU film in a vacuum environment for 15min, taking out, putting into a blast oven, drying at 75 ℃ and curing for 12h, taking out, putting into a container filled with deionized water, performing ultrasonic assistance for 10min, enhancing firmness of conductive substances on the surface of the fiber, finally cleaning with deionized water for several times, and drying to obtain the conductive CNTs/WPU film with the conductivity of 372.6 Sm−1The electromagnetic interference (EMI) Shielding Efficiency (SE) was 24.7dB and the elongation at break was 62%.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modifications, alterations and equivalent changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.
Claims (9)
1. An electromagnetic shielding film based on carbon nanotube composite waterborne polyurethane is characterized in that: the preparation method comprises the following steps:
(1) preparation of WPU solution: placing polyether 3050 in a container, dehydrating at high temperature in vacuum, cooling after water is completely removed, adding 2, 2-dimethylolpropionic acid and toluene diisocyanate into the system while stirring, and carrying out prepolymerization reaction under vigorous stirring in an inert atmosphere to obtain a prepolymer; cooling, adding triethylamine for neutralization reaction to neutralize carboxylic acid group in prepolymer, and then adding Na2SO3Stirring and emulsifying with water vigorously to obtain WPU solution;
(2) preparation of WPU nanofiber membrane: loading the WPU solution into an injector to be used as a spinning solution, and preparing the WPU nano-fiber film by an electrostatic spinning technology;
(3) preparation of CNTs dispersion: adding CNTs and sodium dodecyl benzene sulfonate into water, and performing ultrasonic treatment to obtain a uniformly dispersed CNTs dispersion liquid;
(4) preparing an electromagnetic shielding film: putting the WPU nanofiber film into a container, vacuumizing, injecting the CNTs dispersion liquid into the container, dipping the WPU nanofiber film in a vacuum environment, taking out, drying and curing, taking out, putting the WPU nanofiber film into another container filled with water, enhancing the bonding firmness of the CNTs on the fiber surface through ultrasonic assistance, finally cleaning with water, and drying to obtain the electromagnetic shielding film.
2. The electromagnetic shielding film according to claim 1, wherein: in the step (1), the temperature of the high-temperature vacuum dehydration is 110-; the temperature of the prepolymerization reaction is 75-85 ℃, and the time is 2-8 h; the temperature of the neutralization reaction is 1-10 ℃ and the time is 5-15 min.
3. The electromagnetic shielding film according to claim 1 or 2, wherein: in the step (1), the using amount of the polyether 3050 is 30-50g, the using amount of the 2, 2-dimethylolpropionic acid is 30-40g, the using amount of the toluene diisocyanate is 3-8g, the using amount of the triethylamine is 1-5g, and the Na is calculated by g2SO3The dosage of the composition is 2-5 g.
4. The electromagnetic shielding film according to claim 3, wherein: in the step (1), the solid content of the WPU solution is 35-45 wt%.
5. The electromagnetic shielding film according to claim 1, wherein: in the step (2), the electrostatic spinning conditions are as follows: the temperature is 20-30 ℃, the relative humidity is 20-30%, and the voltage is 15-20 kv; the specification of the metal needle tip for electrostatic spinning is 25-18G, the inner diameter is 0.3-0.4mm, and the outer diameter is 0.70-0.75 mm; the flux level of the spinning solution is 2-4 ml/h.
6. The electromagnetic shielding film according to claim 3, wherein: in the step (3), the amount of CNTs is 20-30mg, the amount of sodium dialkylbenzenesulfonate is 100-150mg, and the amount of water is 10-15ml, calculated as mg and ml.
7. The electromagnetic shielding film according to claim 1, wherein: in the step (3), the ultrasonic power is 20-30%, and the ultrasonic time is 20-30 min.
8. The electromagnetic shielding film according to claim 6, wherein: in the step (4), the injection amount of the CNTs dispersion liquid is 20-30mg in terms of mg, and the dipping time is 5-15 min.
9. The electromagnetic shielding film according to claim 1, wherein: in the step (4), the drying conditions are as follows: 60-75 ℃ for 10-13 h; the ultrasonic treatment time is 10-15 min.
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| CN104774339A (en) * | 2015-04-02 | 2015-07-15 | 北京市射线应用研究中心 | Polyether-type water-based polyurethane emulsion and preparation method thereof |
| CN112921414A (en) * | 2021-01-22 | 2021-06-08 | 齐鲁工业大学 | Preparation method of green environment-friendly waterborne polyurethane nanofiber |
| CN113981670A (en) * | 2021-09-10 | 2022-01-28 | 西安交通大学 | Flexible and stretchable electromagnetic shielding fiber film and preparation method thereof |
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| CN104774339A (en) * | 2015-04-02 | 2015-07-15 | 北京市射线应用研究中心 | Polyether-type water-based polyurethane emulsion and preparation method thereof |
| CN112921414A (en) * | 2021-01-22 | 2021-06-08 | 齐鲁工业大学 | Preparation method of green environment-friendly waterborne polyurethane nanofiber |
| CN113981670A (en) * | 2021-09-10 | 2022-01-28 | 西安交通大学 | Flexible and stretchable electromagnetic shielding fiber film and preparation method thereof |
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