CN111662475A

CN111662475A - Intelligent early warning flame-retardant material prepared from modified high-molecular polymer, and preparation method and application thereof

Info

Publication number: CN111662475A
Application number: CN202010554693.4A
Authority: CN
Inventors: 邹超; 侯昭升; 祝敬妥; 景臣; 钟文; 滕金伟; 徐钧; 刘辉; 王赛
Original assignee: Nanjing Training Team Of Fire Rescue Bureau Of Emergency Management Department; Shandong Normal University
Current assignee: Nanjing Training Team Of Fire Rescue Bureau Of Emergency Management Department; Shandong Normal University
Priority date: 2020-06-17
Filing date: 2020-06-17
Publication date: 2020-09-15
Anticipated expiration: 2040-06-17
Also published as: CN111662475B

Abstract

The invention discloses an intelligent early warning flame retardant material prepared from a modified high molecular polymer, a method and application thereof, wherein the method comprises the following steps: the preparation method comprises the steps of modifying a high molecular polymer by using diisocyanate, grafting an isocyanate group on the surface of the high molecular polymer, adding graphene oxide to react with the isocyanate group on the surface of the high molecular polymer, forming a graphene layer on the surface of the high molecular polymer, adding aminopropyltriethoxysilane to react, adding tetraethoxysilane and tetramethylammonium hydroxide, and synthesizing octa tetramethylammonium polyhedral oligomeric silsesquioxane on the graphene layer by a sol-gel method. The material prepared by the invention integrates the self flame-retardant characteristic and signal induction, so that the manufacturing cost of a security system can be reduced, and the fire detection precision can be further improved.

Description

Intelligent early warning flame-retardant material prepared from modified high-molecular polymer, and preparation method and application thereof

Technical Field

The invention belongs to the technical field of polymer chemistry and functional materials, and relates to an intelligent early warning flame retardant material prepared from a modified high molecular polymer, a method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

The polymer material has the advantages of light weight, easy processing and forming and the like, and is widely applied to the fields of production, life and the like. However, most of high molecular materials are easy to burn, and the burning process is accompanied by the generation of toxic and harmful smoke, so that the fire hazard is serious. Therefore, the flame retardant modification of the polymer material becomes an important means for expanding the application field of the polymer material, and is one of the important points of the polymer material research. Benzoxazine is a new thermosetting phenolic resin polymer, and has been increasingly researched and paid attention to its excellent properties. The polybenzoxazine resin has the advantages of low cost and wide source of raw materials, simple synthesis process and the like, overcomes some defects on the basis of keeping the advantages of the traditional thermosetting resin, has the possibility of replacing phenolic benzoxazine resin as a high-performance material due to the advantages, and is expected to be widely applied to the aspects of mould pressing and injection molding products, adhesives, novel high-performance coatings, high-temperature-resistant electric insulating materials, high-performance structural materials and the like; polyurethane is an organic high molecular material which is prepared by reacting polyisocyanate and polyol and has a plurality of urethane chain segments. Polyurethane materials have many advantages such as excellent flexibility, adhesion, wear resistance, and low temperature resistance. Due to these properties, polyurethane materials have a very important role in the new material industry, and are widely used in the fields of aerospace, automobiles, buildings, coatings, textiles, leather, furniture, home appliances, packaging, military industry and the like. However, the polyurethane material which is not subjected to flame retardant treatment can be combusted and decomposed when meeting fire, and a large amount of toxic and harmful gas is released, so that certain potential safety hazard exists.

Patent CN208118611U discloses an organopolysiloxane environment-friendly flame retardant board. This patent is through setting up polysiloxane material layer, decorative layer, back up coat, sound absorbing layer, the connection between the environmental protection board material layer at fire-retardant board body and being bonded by fire-retardant adhesive, can prepare the fire-retardant board of organopolysiloxane environmental protection, but plays fire-retardant effect through the physics polysiloxane material layer that adds, and fire-retardant mechanism is single.

Patent CN208077359U discloses an electronic sensor for early warning of fire. According to the method for setting the temperature sensors, when an abnormal heat source is detected, the feedback information of the system is triggered to achieve the early warning effect. But the interference to the ambient living heat source is easy to cause the false alarm of the alarm condition.

In summary, the present inventors have found that the existing flame retardant polymer material has a single flame retardant mechanism, and achieves a flame retardant effect only by introducing molecules with non-flammable materials or flame retardancy. Most of modified materials can only meet basic physical properties such as flame retardance, corrosion resistance and the like, and the application value is single.

Disclosure of Invention

In order to solve the defects of the prior art, the invention aims to provide an intelligent early warning flame retardant material prepared from a modified high molecular polymer, a method and application thereof.

In order to achieve the purpose, the technical scheme of the invention is as follows:

on the one hand, the method for preparing the intelligent early warning flame retardant material by using the modified high molecular polymer is characterized in that diisocyanate is adopted to modify the high molecular polymer, so that an isocyanate group is grafted on the surface of the high molecular polymer, graphene oxide is added to react with the isocyanate group on the surface of the high molecular polymer, a graphene layer is formed on the surface of the high molecular polymer, aminopropyltriethoxysilane is added to react, tetraethoxysilane and tetramethylammonium hydroxide are added, and octa-tetramethylammonium polyhedral oligomeric silsesquioxane is synthesized on the graphene layer by a sol-gel method.

According to the invention, the graphene oxide layer is linked on the surface of the high molecular polymer through diisocyanate, the graphene oxide can improve the thermal stability, delay the ignition time of the polymer and inhibit the spread of flame, and the graphene oxide can change the heat absorption, viscosity and dripping property of the polymer in the combustion process. Meanwhile, the graphene oxide contains a large number of oxygen-containing functional groups and can be connected to the surface of the high molecular polymer through chemical bonds, so that the graphene layer is more compact, and the graphene layer can better separate the high molecular polymer; and the oxygen-containing functional group of the graphene oxide can be used for connecting octa-tetramethyl ammonium group cage type silsesquioxane to the surface of the graphene layer through aminopropyl triethoxysilane reaction, and the cage type silsesquioxane (POSS) can be used for remarkably improving the heat resistance and the combustion performance of the polymer. The two have synergistic effect, so that a complete and compact carbon layer can be formed during combustion, the physical barrier effect is exerted, and heat and oxygen can be insulated; meanwhile, the condensed phase flame retardant effect can be exerted, so that the intensity of matrix combustion is effectively reduced, and the flame retardant property of the material is further improved.

On the other hand, the intelligent early warning flame retardant material prepared from the modified high molecular polymer is prepared by the method.

In a third aspect, the intelligent early warning flame retardant material prepared from the modified high molecular polymer is applied to the fields of fire-fighting equipment, chemical building materials, automobile industry, ship industry, aerospace, electronic devices and the like.

The invention has the beneficial effects that:

1. compared with the common high-molecular flame-retardant material, the intelligent early-warning flame-retardant material prepared from the high-molecular polymer has the characteristics of easiness in processing, wide application range and the like.

2. The intelligent early warning flame retardant material prepared from the high molecular polymer has the excellent performance shown in the step 1, and is determined by the structure of the modified polymer, and the graphene and the polysilsesquioxane are grafted to the polymer, so that partial characteristics of the graphene and the polysiloxane are added to the modified high molecular material; the flame-retardant polyhedral oligomeric silsesquioxane (POSS) and Graphene Oxide (GO) have thermal stability and flame-retardant potential, a relatively complete and relatively compact carbon layer is formed in the combustion process through the synergistic effect of the POSS and the GO, and the flame-retardant property is more excellent.

3. The intelligent early warning flame retardant material prepared from the high molecular polymer provided by the invention has conductivity due to the introduction of the graphene, and can be used as an electronic device, so that a common high molecular material can be widely applied; when the material is applied as a flame retardant material, the material can also be used as a fire detection sensor, the material structure is changed due to factors such as high temperature, the resistivity is changed, the response of a security system is triggered, the purpose of early warning is achieved, and the detection and alarm precision is further improved.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In view of the defects of poor flame retardant effect, single performance and the like of the conventional flame retardant high polymer material, the invention provides an intelligent early warning flame retardant material prepared from a modified high polymer, and a method and application thereof.

The invention provides a typical implementation mode of a method for preparing an intelligent early-warning flame-retardant material by modifying a high-molecular polymer by using diisocyanate, so that an isocyanate group is grafted on the surface of the high-molecular polymer, graphene oxide is added to react with the isocyanate group on the surface of the high-molecular polymer, a graphene layer is formed on the surface of the high-molecular polymer, aminopropyltriethoxysilane is added to react, tetraethoxysilane and tetramethylammonium hydroxide are added, and octa-tetramethylammonium polyhedral oligomeric silsesquioxane is synthesized on the graphene layer by a sol-gel method.

According to the invention, the graphene oxide layer is linked on the surface of the high-molecular polymer through diisocyanate, meanwhile, the cage-type silsesquioxane is connected on the surface of the graphene oxide layer through the aminopropyl triethoxysilane reaction, and through the synergistic effect of the graphene oxide layer and the cage-type silsesquioxane, a relatively complete and compact carbon layer is formed during combustion, so that the physical barrier effect is exerted, and the thermal insulation and oxygen isolation can be realized; meanwhile, the condensed phase flame retardant effect can be exerted, so that the intensity of matrix combustion is effectively reduced, and the flame retardant property of the material is further improved.

The diisocyanate of the present invention is a compound having two isocyanate groups (-N ═ C ═ O), such as Toluene Diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), Hexamethylene Diisocyanate (HDI), Lysine Diisocyanate (LDI), and the like. When hexamethylene diisocyanate is used, the effect is better. In the examples the HDI purity was > 97.0%.

The high molecular polymer of the invention refers to the existing high molecular materials such as polyurethane, benzoxazine polymer and the like.

In one or more embodiments of this embodiment, the process of modifying with a diisocyanate is: adding high molecular polymer into diisocyanate solution, and adding catalyst for reaction. In this series of examples, the catalyst was stannous octoate or dibutyltin dilaurate. The purity of the stannous octoate is 92.5-100.0%; or dibutyltin dilaurate (DBTDL) with a purity of 95%. The solvent of the diisocyanate solution used in the examples of the present invention was dry toluene, which was further purified by distillation from toluene (analytically pure AR grade, purity > 99.5%).

In one or more embodiments of the embodiment, the reaction temperature for modification by diisocyanate is 35-80 ℃, and the reaction time is 2-8 h.

The high molecular polymer of the invention is a block or sheet structure, and in one or more examples of the embodiment, the addition amount of diisocyanate is as follows: per cm²10-15 mL of diisocyanate is added to the high molecular polymer.

The graphene oxide can be a product sold in the market and can also be prepared by self. The preparation method of the graphene oxide comprises the following steps: the Brodie method, Staudenmier method or Hummers method. In one or more embodiments of this embodiment, the graphene oxide is prepared by: mixing graphite flake powder, potassium nitrate and concentrated sulfuric acid in ice bath, and mixingAdding potassium permanganate, reacting at 40-60 ℃, and then adding hydrogen peroxide for treatment. The purity of the flake graphite powder is more than or equal to 99.9 percent, and the specific surface area (m)²The/g) can be 5 μm, 1nm and 50nm, wherein the same unit-level similar-sized flake graphene is contained.

In the series of embodiments, after the hydrogen peroxide treatment, the materials are dispersed in water, subjected to ultrasonic centrifugation, and freeze-dried. The obtained graphene oxide is purer. Wherein the freeze drying time is 18-30 h.

In this series of examples, potassium nitrate abundance: 10 atom% or 90 atom%, chemical purity: more than or equal to 98.5 percent; the concentration of sulfuric acid is more than or equal to 98 percent; potassium permanganate AR is more than or equal to 99.5 percent; h₂O₂Purity 30% or 35%.

In the series of embodiments, the addition molar ratio of potassium nitrate, potassium permanganate and concentrated sulfuric acid is 1: 2-5: 50 to 100.

In one or more embodiments of the present invention, a high molecular polymer modified with diisocyanate is added to a dispersion of graphene oxide, and the reaction is performed under shaking conditions. The solvent in the dispersion of graphene oxide is N, N-dimethylformamide. N, N-Dimethylformamide (DMF) with a purity of > 99.5% (GC) was anhydrous.

In the series of embodiments, the reaction time is 20-30 h.

In one or more embodiments of the present invention, a polymer reacted with graphene oxide and N, N' -Dicyclohexylcarbodiimide (DCC) are dispersed in a solution of propyltriethoxysilane, and heated to 60 to 80 ℃ to react.

In the series of embodiments, the reaction time is 18-30 h.

In one or more examples of this embodiment, two different silanes are added to the polymer after reaction with aminopropyltriethoxysilane, the reaction is carried out at room temperature for a set time, hydrochloric acid is added dropwise and the reaction is continued for a set time by heating. The two silanes comprise dimethyldiethoxysilane (purity is more than or equal to 98 percent) and phenyltriethoxysilane (purity is more than or equal to 97 percent), also can be diethoxymethylphenylsilane (purity is more than or equal to 98 percent) and phenyltriethoxysilane, also can be dimethyldiethoxysilane (purity is more than or equal to 98 percent) and phenyltri (trimethylsiloxy) silane which are more than 98.0 percent, and also can be diethoxymethylphenylsilane (purity is more than or equal to 98 percent) and phenyltri (trimethylsiloxy) silane which are more than 98.0 percent. The room temperature refers to the temperature of an indoor environment, and is generally 15-30 ℃. The effect is better when the two different silanes are respectively dimethyldiethoxysilane and phenyltriethoxysilane. The effect is particularly best when the molar ratio of dimethyldiethoxysilane to phenyltriethoxysilane is 0.8-1.6: 1.

In this series of examples, the concentration of hydrochloric acid was 40. + -. 5 wt%.

In the series of embodiments, after the hydrochloric acid is dripped, the reaction time is 6-10 h, and the reaction temperature is 50-70 ℃.

The invention further provides an intelligent early warning flame retardant material prepared from the modified high molecular polymer, and the material is prepared by the method.

The third embodiment of the invention provides an application of the intelligent early warning flame retardant material prepared from the modified high molecular polymer in the fields of fire-fighting equipment, chemical building materials, automobile industry, ship industry, aerospace, electronic devices and the like.

In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the technical solution of the present invention will be described in detail below with reference to specific examples and comparative examples.

Example 1

141g of hexamethylene diisocyanate HDI (0.84mol) are placed in a three-neck flask, mechanical stirring is turned on under the protection of nitrogen, 12.68g of 1, 4-butanediol BDO (0.14mol) are reacted for 5h under the protection of nitrogen at 80 ℃, 200mL of n-hexane is added after cooling to room temperature, and after stirring, suction filtration is carried out to obtain white solid HBH. And (3) mixing metered caprolactone (-CL) and 1, 4-Butanediol (BDO) under the protection of nitrogen, dropwise adding a drop of stannous octoate, slowly heating to 140 ℃, stirring for reacting for 24 hours, cooling to room temperature, performing suction filtration and vacuum drying to obtain the PCL product. At 80 ℃, dropwise adding HBH DMSO solution (20 g HBH dissolved in each 100mL DMSO) into PCL prepolymer under the protection of nitrogen, reacting for 5 hours, adding a proper amount of dioxane solvent to reduce viscosity, settling, drying to constant weight to obtain polyurethane PEU, dissolving PEU in chloroform (3g/80mL), pouring into a Polytetrafluoroethylene (PTFE) mold, and naturally volatilizing to obtain the polyurethane PEU film.

Example 2

(1) Adding a certain amount of Hexamethylene Diisocyanate (HDI) into 50mL of anhydrous toluene, washing the polyurethane PEU film prepared in the embodiment 1 with the anhydrous toluene until the surface is clean, putting the washed polyurethane PEU film into the anhydrous toluene solution, dropwise adding a drop of stannous octoate, oscillating the solution at 50 ℃ for reaction for 6 hours, taking out the film after the reaction is finished, and repeatedly washing the film for three times with the anhydrous toluene to remove the unreacted HDI;

(2) 60mg of flake graphite powder was used as a starting material, and was mixed with 3g of potassium nitrate in 100ml of concentrated sulfuric acid (98 wt%), followed by stirring and cooling in an ice bath. 12g of potassium permanganate was slowly added to the mixture and vigorously stirred to improve mixing with the graphite and to maintain the temperature below 20 ℃. The mixture was then heated in a water bath at a temperature of 50 ℃ for 3h to form a thick paste. 150ml of water are gradually added to the paste, stirring is continued for 15 minutes at 90 ℃ and then 150ml of water are added in the same manner. Finally, 15ml of H is used₂O₂(30 wt.%) the mixture was treated to change the solution color from dark brown to yellow. Centrifugation was repeated and washing with dimer acid diisocyanate (DDI) water was carried out until the pH of the solution became neutral. Drying the generated graphite oxide in air, then dispersing in water to form suspension, and removing the non-oxidized graphite by ultrasonic treatment for 25min at 8000 rpm/separation for 30 min. And then, freeze-drying for 20 hours to obtain pure graphene oxide powder. The treated graphene oxide powder was dispersed in DMF at room temperature, followed by exfoliation under ultrasound for several hours and resulted in a homogeneous suspension. Adding the material prepared in the step (1) into the suspension at room temperature, carrying out violent oscillation reaction for 20 hours, washing with DMF, and drying in a vacuum oven for 6 hours;

(3) 10ml Aminopropyltriethoxysilane (APTES) and 50ml toluene were mixed. Then, the material obtained in step (2) and 60mg of N, N' -Dicyclohexylcarbodiimide (DCC) were dispersed in the mixture by ultrasonic waves and shaken for 1 hour. After shaking reaction at 70 ℃ for 24h, washing the modified polyurethane PEU film with ethanol, and drying in a vacuum oven for 6 h;

(4) and (3) dispersing the polyurethane PEU film obtained in the step (3) in a mixed solution of 60ml of ethanol/water (volume ratio of 1:1), then carrying out ultrasonic treatment for 50min, and then adding a mixed solution of two kinds of silanes, including 15mg of dimethyldiethoxysilane and 24mg of phenyltriethoxysilane, into the mixed solution. After the reaction was vigorously shaken at room temperature for 10min, hydrochloric acid (18 wt%) was slowly added dropwise. After the dropwise addition, the shaking reaction is continued for 8 hours (60 ℃), the surface is in a faint yellow sticky state, ethyl acetate and ice-cold deionized water are added, and the leaching is repeated for three times.

Example 3

In N₂Under protection, polytetrahydrofuran ether PTMG (3g, 0.003mol) and hexamethylene diisocyanate HDI (1.33g, 0.006mol) are mixed and stirred for reaction, 1-2 drops of stannous octoate are dripped to be used as a catalyst, and the temperature is kept at 85 ℃ for reaction to prepare a prepolymer. Dissolving aniline methyl POSS with different contents in 10mL of N, N-Dimethylacetamide (DMAC) solvent, slowly dripping prepolymer into the prepolymer, fully stirring, keeping the temperature at 95 ℃ to uniformly mix the solution, continuously dripping 1, 4-Butanediol (BDO) N, N-Dimethylacetamide (DMAC) solution, pouring the solution into a polytetrafluoroethylene mold, and naturally volatilizing to obtain the modified polyurethane film.

Example 4

(1) In N₂Under protection, polytetrahydrofuran ether PTMG (3g, 0.003mol) and hexamethylene diisocyanate HDI (1.33g, 0.006mol) are mixed and stirred for reaction, 1-2 drops of stannous octoate are dripped to be used as a catalyst, and the temperature is kept at 85 ℃ for reaction to prepare a prepolymer. Dissolving aniline methyl POSS with different contents in 10mL of N, N-Dimethylacetamide (DMAC) solvent, slowly dripping prepolymer into the prepolymer, fully stirring the mixture, keeping the temperature at 95 ℃ to uniformly mix the solution, continuously dripping 1, 4-Butanediol (BDO) N, N-Dimethylacetamide (DMAC) solution, pouring the solution into a polytetrafluoroethylene mold, and naturally volatilizing to obtain a modified polyurethane film;

(2) adding a certain amount of HDI into 80mL of anhydrous toluene, washing the modified polyurethane film prepared in example 4(1) with anhydrous toluene until the surface is clean, adding the film into the anhydrous toluene solution, dropwise adding a drop of catalyst, oscillating and reacting at 60 ℃ for 8h, taking out the film after the reaction is finished, and repeatedly washing the film for three times with anhydrous toluene to remove the unreacted HDI;

(3) 70mg of flake graphite powder was used as a starting material, and was mixed with 3g of potassium nitrate in 100ml of sulfuric acid under stirring, followed by cooling in an ice bath. 12g of potassium permanganate was slowly added to the mixture and vigorously stirred to improve mixing with the graphite and to maintain the temperature below 20 ℃. The mixture was then heated in a water bath at a temperature of 50 ℃ for 3h to form a thick paste. 150ml of water are gradually added to the paste, stirring is continued for 20 minutes at 90 ℃ and then 150ml of water are added in the same manner. Finally, 20ml of H is used₂O₂(30 wt.%) the mixture was treated to change the solution color from dark brown to yellow. Centrifugation was repeated and washing with dimer acid diisocyanate (DDI) water was carried out until the pH of the solution became neutral. Drying the generated graphite oxide in air, then dispersing in water to form suspension, and removing the non-oxidized graphite by ultrasonic treatment for 25min at 8000 rpm/separation for 30 min. And then, freeze-drying for 24 hours to obtain pure graphene oxide powder. The treated graphene oxide powder was dispersed in DMF at room temperature, followed by exfoliation under ultrasound for several hours and resulted in a homogeneous suspension. Adding the material prepared in the step (1) into the suspension at room temperature, carrying out violent oscillation reaction for 20 hours, washing with DMF, and drying in a vacuum oven for 10 hours;

(4) 15ml Aminopropyltriethoxysilane (APTES) and 60ml toluene were mixed. Then, the material obtained in step (3) and 60mg of N, N' -Dicyclohexylcarbodiimide (DCC) were dispersed in the mixture by ultrasonic wave and shaken for 1 hour. After shaking reaction at 70 ℃ for 24h, the modified POSS-polyurethane film is washed by ethanol and then dried in a vacuum oven for 8 h.

(5) And (3) dispersing the modified POSS-polyurethane film obtained in the step (4) in a mixed solution of 60ml of ethanol/water (volume ratio of 1:1), then carrying out ultrasonic treatment for 50min, and then adding a mixed solution of two kinds of silanes, including 15mg of diethoxymethylphenylsilane and 35mg of phenyltris (trimethylsiloxy) silane, into the mixed solution. After the reaction was vigorously shaken at room temperature for 20min, a 40 wt% hydrochloric acid solution was slowly added dropwise. After the dropwise addition, the shaking reaction is continued for 6h (60 ℃), ethyl acetate and ice-cold deionized water are added, and the leaching is repeated for three times.

Example 5

Mixing and stirring 15.0mL of 1, 4-dioxane and 7.8mL (0.11mol) of formaldehyde solution in a beaker, then dropwise adding KOH solution to adjust the pH to 8, dropwise adding 3.0mL (0.05mol) of ethanolamine in ice bath, maintaining the temperature at 25 ℃, mechanically stirring for 30min, then adding 5.7g (0.25 mol 1) of bisphenol A, reacting for 3.5h at 70 ℃, washing and drying the product, and concentrating under reduced pressure to obtain a yellow-green transparent solid. 0.40g of the above solid was taken and put into 6.0mL of anhydrous CH₂C1₂And 0.17mL of TDI, dripping 1-2 drops of dibutyltin dilaurate into the flask, heating and refluxing for reaction for 1h, adding the solution into a tetrahydrofuran mold, volatilizing the solvent to obtain a hard transparent film, and putting the prepared film into an electrothermal constant-temperature drying oven for segmented curing to obtain the polybenzoxazine film.

Example 6

(1) 2mL of HDI was added to 80mL of anhydrous toluene, and 2 × 2cm was taken²And (3) flushing the polybenzoxazine resin film with anhydrous toluene until the surface is clean, then putting the polybenzoxazine resin film into the anhydrous toluene solution, dropwise adding a drop of catalyst, oscillating and reacting for 8h at 60 ℃, taking out the film after the reaction is finished, and repeatedly washing the film for three times with the anhydrous toluene to remove unreacted HDI.

(3) 70mg of flake graphite powder was used as a starting material, and mixed with 6g of potassium nitrate in 100ml of 98% sulfuric acid under stirring, followed by cooling in an ice bath. 12g of potassium permanganate was slowly added to the mixture and vigorously stirred to improve mixing with the graphite and to maintain the temperature below 20 ℃. The mixture was then heated in a water bath at a temperature of 50 ℃ for 3h to form a thick paste. 150ml of water are gradually added to the paste, stirring is continued for 20 minutes at 90 ℃ and then 150ml of water are added in the same manner. Finally, 20ml of H is used₂O₂(30 wt.%) the mixture was treated to change the solution color from dark brown to yellow. Repeatedly centrifuging, and using dimer acidThe isocyanate (DDI) was washed with water until the solution pH became neutral. And drying the generated graphite oxide in air, dispersing the graphite oxide in water to form a suspension, and removing the unoxidized graphene by ultrasonic treatment for 25min at 8000 rpm/separation for 30 min. And then, freeze-drying for 24 hours to obtain pure graphene oxide powder. The treated graphene oxide powder was dispersed in DMF at room temperature, followed by exfoliation under ultrasound for several hours and resulted in a homogeneous suspension. Adding the material prepared in the step (1) into the suspension at room temperature, carrying out violent shaking reaction for 20 hours, washing with DMF, and drying in a vacuum oven for 10 hours.

(4) 15ml Aminopropyltriethoxysilane (APTES) and 60ml toluene were mixed. Then, the material obtained in step (2) and 60mg of N, N' -Dicyclohexylcarbodiimide (DCC) were dispersed in the mixture by ultrasonic waves and shaken for 1 hour. After shaking reaction at 70 ℃ for 24h, washing the modified polybenzoxazine film with ethanol, and drying in a vacuum oven for 8 h;

(5) dispersing the modified polybenzoxazine film obtained in the step (4) in a mixed solution of 60ml of ethanol/water (volume ratio 1:1), then carrying out ultrasonic treatment for 50min, and then adding a mixed solution of two kinds of silanes, including 15mg of diethoxymethylphenylsilane and 35mg of phenyltris (trimethylsiloxy) silane, to the above mixed solution. After the reaction was vigorously shaken at room temperature for 20min, a 40 wt% hydrochloric acid solution was slowly added dropwise. After the dropwise addition, the shaking reaction is continued for 6h (60 ℃), the surface is in a faint yellow sticky state, ethyl acetate and ice-cold deionized water are added, and the leaching is repeated for three times.

Comprehensive analysis shows that the method for preparing the intelligent early warning flame retardant material by using the modified high molecular polymer improves the thermal stability and the flame retardant property of the polymer on a molecular level. Meanwhile, the modified material has the characteristic of conductivity, and can be used as a fire detection sensor.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an intelligent early warning flame retardant material from a modified high molecular polymer is characterized in that diisocyanate is used for modifying the high molecular polymer, isocyanate groups are grafted on the surface of the high molecular polymer, graphene oxide is added to react with the isocyanate groups on the surface of the high molecular polymer, a graphene layer is formed on the surface of the high molecular polymer, aminopropyltriethoxysilane is added to react, tetraethoxysilane and tetramethylammonium hydroxide are added, and octa-tetramethylammonium polyhedral oligomeric silsesquioxane is synthesized on the graphene layer through a sol-gel method.

2. The method for preparing the intelligent early warning flame retardant material by the modified high molecular polymer as claimed in claim 1, wherein the process of modifying by the diisocyanate comprises the following steps: adding high molecular polymer into diisocyanate solution, and adding catalyst for reaction.

3. The method for preparing the intelligent early warning flame retardant material by using the modified high molecular polymer as claimed in claim 1, wherein the reaction temperature for modification by using the diisocyanate is 35-80 ℃, and the reaction time is 2-8 h.

4. The method for preparing the intelligent early warning flame retardant material by using the modified high molecular polymer as claimed in claim 1, wherein the addition amount of diisocyanate is as follows: per cm²10-15 mL of diisocyanate is added to the high molecular polymer.

5. The method for preparing the intelligent early warning flame retardant material by the modified high molecular polymer as claimed in claim 1, wherein after the hydrogen peroxide treatment, the material is dispersed into water, subjected to ultrasonic centrifugation and freeze drying;

or the addition ratio of potassium nitrate, potassium permanganate and sulfuric acid is 1: 1-1.5: 100 to 150.

6. The method for preparing the intelligent early-warning flame-retardant material by using the modified high-molecular polymer as claimed in claim 1, wherein the high-molecular polymer modified by diisocyanate is added into the dispersion liquid of the graphene oxide, and the reaction is carried out under the shaking condition.

7. The method for preparing the intelligent early warning flame retardant material by using the modified high molecular polymer as claimed in claim 1, wherein the high molecular polymer reacted with the graphene oxide and N, N' -dicyclohexylcarbodiimide are dispersed into a solution of propyltriethoxysilane, and the solution is heated to 60-80 ℃ for reaction.

8. The method for preparing the intelligent early warning flame retardant material by the modified high molecular polymer as claimed in claim 1, wherein two different silanes are added into the high molecular polymer reacted with the aminopropyltriethoxysilane, the reaction is carried out for a set time at room temperature, hydrochloric acid is dripped, and then the heating is carried out for a continued reaction for a set time;

preferably, the concentration of hydrochloric acid is 40 + -5 wt%;

preferably, after the hydrochloric acid is dripped, the reaction time is 6-10 h, and the reaction temperature is 50-70 ℃.

9. An intelligent early warning flame retardant material prepared from a modified high molecular polymer, which is characterized by being prepared by the method of any one of claims 1 to 8.

10. An application of the modified high molecular polymer of claim 9 in preparing intelligent early warning flame retardant materials in the fields of fire-fighting equipment, chemical building materials, automobile industry, ship industry, aerospace or electronic devices.