Polyurethane elastomer with flame-retardant and strong electromagnetic shielding effects and preparation method thereof

Abstract

The invention belongs to the technical field of polymer composite materials, and relates to a polyurethane elastomer with flame-retardant and strong electromagnetic shielding effects, which is prepared by the following steps: carrying out in-situ chain extension reaction on a functional complex formed by coordination reaction of an erbium (III)-containing compound and a phosphoric acid compound and an isocyanate-terminated polyurethane prepolymer, and adding a magnetic substance into the system to obtain the flame-retardant and strong electromagnetic shielding polyurethane elastomer. And then carrying out magnetic orientation treatment. The mass ratio of the functional complex to the isocyanate-terminated polyurethane prepolymer is (1-10): 100. The polyurethane elastomer prepared by the invention has excellent flame retardant property and strong electromagnetic shielding property, and is better in mechanical property, that is, synergistic improvement of the mechanical property, the electromagnetic shielding property and the flame retardant property is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer composites, and particularly relates to a polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect and a preparation method thereof. Background Art

[0002] With the development of industries, medical, electronic products, military and aerospace fields, the demand for electromagnetic shielding materials has increased sharply, and higher requirements have been put forward for the performance of electromagnetic shielding materials. Compared with metal-based and concrete-based electromagnetic shielding materials, polymer-based electromagnetic shielding materials have the advantages of light weight, easy processing, corrosion resistance, etc., and have a wider application in fields such as electronics, electrical engineering, and aerospace. Among them, polyurethane elastomers have received more attention as the matrix of electromagnetic shielding materials due to their excellent physical and chemical properties such as high strength, high toughness, corrosion resistance, heat resistance, and wear resistance. At present, the main method for preparing polymer-based electromagnetic shielding materials is to fill polymers with conductive particles. Commonly used conductive particles include metals, carbon black, graphite, graphene, and carbon nanotubes, etc.; and whether the conductive network constructed by the interaction between the conductive particles and the matrix material is perfect and the conductive performance of the conductive particles are the key factors affecting the electromagnetic shielding performance. In the prior art, conductive particles are generally filled by blending, and the conductive particles are easily unevenly dispersed in the matrix, resulting in an imperfect conductive network, so that the electromagnetic shielding performance needs to be further improved; in addition, filling conductive particles by blending will also affect the mechanical properties of the matrix. For example, Chinese Patent CN116535843A discloses a preparation method of a polyurethane composite material with flame retardancy and electromagnetic shielding performance. The preparation method includes the following steps: adding 0.01-100 parts of polyurethane, 0.01-20 parts of magnetic response two-dimensional material aerogel microspheres, 0.01-100 parts of filler, 0.01-10 parts of antioxidant, 0.01-10 parts of anti-aging agent, 0.01-40 parts of plasticizer, and 0.01-10 parts of catalyst into a twin-screw extruder, and carrying out melt blending at a temperature of 120-220 °C for 1-60 minutes, and extruding to obtain a polyurethane composite material with flame retardancy and electromagnetic shielding performance. The invention prepares a polyurethane-based electromagnetic shielding material by melt blending, and its electromagnetic shielding performance and mechanical properties still need to be further improved.

[0003] As a protective material, electromagnetic shielding materials are widely used in daily life. Therefore, in addition to its electromagnetic shielding ability, there are also high requirements for its flame retardant performance. The limiting oxygen index (LOI) of polyurethane (TPU) is only about 18%, which belongs to a flammable polymer material. Moreover, polyurethane will produce a large amount of molten droplets after ignition, which will spread and propagate the flame and cause secondary combustion. Therefore, improving the flame retardant performance of polyurethane elastomers is also a great challenge. However, the traditional flame retardant method is physical addition, although it will have a good flame retardant effect, but it will reduce the mechanical properties of the material.

[0004] Therefore, it is still a huge challenge to make polyurethane shielding materials have excellent electromagnetic shielding performance, flame retardancy and good mechanical properties at present. Summary of the Invention

[0005] In view of the problem that polymer-based electromagnetic shielding materials in the prior art cannot balance electromagnetic shielding performance, flame retardancy and mechanical properties, the present invention provides a polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect and a preparation method thereof. Using Er 3+ as a metal coordination site, a coordination reaction is carried out with a phosphoric acid compound to prepare a functional complex containing active functional groups. Then, the functional complex is introduced into the polyurethane molecular chain in a way of in-situ reaction, so that the polyurethane elastomer has the functions of both flame retardancy and electromagnetic shielding effect. Since it is in-situ introduced into the polyurethane molecular chain, the prepared polyurethane elastomer has good mechanical properties. At the same time, magnetic substances are introduced into the polyurethane during the preparation process, and they are regularly arranged in the polyurethane through magnetic orientation, further enhancing the electromagnetic shielding performance of the polyurethane elastomer. The combined action of the functional complex and the oriented arrangement of magnetic substances finally realizes the synergistic improvement of the mechanical properties, electromagnetic shielding performance and flame retardancy of the polyurethane elastomer.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect is obtained by in-situ chain extension reaction of a functional complex formed by the coordination reaction of an erbium(III) compound and a phosphoric acid compound with a terminal isocyanate group polyurethane prepolymer, adding magnetic substances to the system, and then performing magnetic orientation treatment; the mass ratio of the functional complex to the terminal isocyanate group polyurethane prepolymer is (1-10):100.

[0008] Preferably, the mass ratio of the functional complex, magnetic substances and the terminal isocyanate group polyurethane prepolymer is (3-7):(1-5):100. Excessive use of the functional complex will increase the cost and cause a decrease in the toughness and strength of the polyurethane.

[0009] Furthermore, the number average molecular weight of the terminal isocyanate group polyurethane prepolymer is 2000-5000; the terminal isocyanate group polyurethane prepolymer is obtained by reacting 4,4'-diphenylmethane diisocyanate (MDI) and polytetrahydrofuran ether glycol (PTMG) at a mass ratio of 1:(2.5-4.5) at 75-85 °C for 1-2 h; the number average molecular weight of the polytetrahydrofuran ether glycol is 1000-2000, and the water content is 10-50 ppm. The terminal isocyanate group polyurethane prepolymer means that the end of the polyurethane prepolymer molecular chain is an NCO group. In the present invention, the end is controlled to be an NCO group and the molecular weight size by controlling the dosage ratio of MDI and PTMG and the reaction conditions.

[0010] Further, the magnetic material is at least one of magnetite, neodymium iron boron alloy, aluminum nickel cobalt alloy, and samarium cobalt alloy, and the average particle size of the magnetic material is 40 to 80 nm.

[0011] Further, the molar ratio of the erbium(III) compound to the phosphoric acid compound is 1:(2 - 3).

[0012] Further, the erbium(III) compound is at least one of Er(NO3)3, ErCl3, and their hydrates, and the hydrates are Er(NO3)3·xH2O and ErCl3·xH2O, where x is an integer between 1 and 6.

[0013] Further, the phosphoric acid compound is at least one of phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, phenylphosphonic acid, aminotrimethylenephosphonic acid, aminomethylphosphonic acid, alendronic acid (4-amino-1-hydroxybutylidene-1,1-diphosphonic acid), and pamidronic acid (3-amino-1-hydroxypropylidene-1,1-diphosphonic acid); preferably at least one of aminotrimethylenephosphonic acid, aminomethylphosphonic acid, alendronic acid, and pamidronic acid. The preferred phosphoric acid compounds contain both a phosphoric acid group and an amino group at the same time. The nitrogen element in the amino group can dilute the concentrations of oxygen and combustible gases in gas-phase flame retardancy and inhibit the combustion chain reaction; meanwhile, from the condensed-phase aspect, the nitrogen element and the phosphorus element can synergistically promote the formation of a carbon layer; that is, the nitrogen element can cooperate with the phosphorus element to achieve a better flame retardant effect. In addition, the amino group can also participate in the subsequent chain extension reaction.

[0014] Further, the functional complex is prepared by a preparation method including the following steps: adding the erbium(III) compound and the phosphoric acid compound into a solvent, reacting at 60 - 90 °C within a pH range of 3 - 6 for 4 - 6 h, filtering, washing, and drying after the reaction to obtain the functional complex. The functional complex with a multidentate coordination structure obtained through the coordination reaction contains both erbium metal element, phosphorus flame retardant element, and active groups.

[0015] Furthermore, the solvent is ethanol or propanol; the washing is with pure water; the drying is vacuum drying at 80 - 100 °C for 12 - 24 h.

[0016] Taking Er(NO3)3·6H2O and alendronic acid with a molar ratio of 1:2 as an example, the reaction formula for preparing the functional complex is as follows:

[0017]

[0018] Taking Er(NO3)3·6H2O and alendronic acid with a molar ratio of 1:3 as an example, the reaction formula for preparing the functional complex is as follows:

[0019]

[0020] Further, the conditions for the in-situ chain extension reaction are as follows: reacting at 75-85°C for 2-3 h. Under these reaction conditions, the active groups, namely hydroxyl and amino groups, in the functional complex will react with the NCO groups of the terminal isocyanate-based polyurethane prepolymer to carry out a chain extension reaction, thereby introducing the functional complex into the polyurethane in-situ.

[0021] Further, the magnetic field strength for the magnetic orientation treatment is 2000-3000 Gauss. In the present invention, the magnetic orientation treatment refers to the process of using magnetic force to perform directional movement and treatment on magnetic substances. After the magnetic orientation treatment, the magnetic substances are arranged in a specific direction in the material to form an ordered magnetic domain structure, which can effectively guide the propagation path of electromagnetic waves, reduce their scattering and reflection, thereby improving the shielding effect.

[0022] In a second aspect, the present invention also provides a method for preparing the above-mentioned polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effects, comprising the following steps:

[0023] 1) Heating 4,4'-diphenylmethane diisocyanate to melt it, adding dried polytetrahydrofuran ether glycol, and raising the temperature for reaction under the protection of an inert atmosphere. After the reaction is completed, a terminal isocyanate-based polyurethane prepolymer is obtained;

[0024] 2) Dissolving the functional complex in a solvent to form a functional complex solution, and then adding the functional polymer solution to the terminal isocyanate-based polyurethane prepolymer for an in-situ chain extension reaction. After the reaction is completed, a polyurethane elastomer solution is obtained;

[0025] 3) Adding magnetic substances to the polyurethane elastomer solution to form a mixture, placing the mixture on a plastic substrate, and then placing the plastic substrate on a magnet plate with a magnetic field strength of 2000-3000 Gauss. By controlling the direction of the plastic substrate, the magnetic substances in the mixture are regularly arranged; then keeping the relative positions of the plastic substrate containing the mixture and the magnet plate unchanged, and removing the solvent by rotary evaporation to obtain a polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effects.

[0026] Further, in step 1), the drying conditions are as follows: dehydrating under vacuum at 105-115°C for 2-3 h; the temperature-raising reaction is carried out at 75-85°C for 1-2 h; the inert atmosphere is nitrogen and / or argon.

[0027] Further, the solvent in step 2) is at least one of N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA).

[0028] Further, the plastic substrate in step 3) is a polytetrafluoroethylene plate; the conditions for rotary evaporation are as follows: vacuum degree 0.01-0.08 Mpa, temperature 60-70°C, and time 2-3 h.

[0029] In the present invention, an erbium(III) compound and a phosphoric acid compound form a functional complex through a coordination reaction. The functional complex contains metal erbium element, phosphorus flame-retardant element, active groups of hydroxyl and amino groups. Reacting the functional complex with a terminal isocyanate group polyurethane prepolymer, the active groups of hydroxyl and amino groups will undergo a chain extension reaction with the NCO groups of the terminal isocyanate group polyurethane prepolymer, thereby introducing the functional complex into the polyurethane in the form of chemical bonds. The phosphorus flame-retardant element in the introduced functional complex can play a flame-retardant effect; metal erbium has a good electromagnetic shielding effect. At the same time, the inventors found through research that during the combustion process of polyurethane, metal erbium can effectively promote the formation of a carbon layer, and the carbon layer will wrap the molten droplets and prevent them from dripping, thereby inhibiting combustion, that is, metal erbium has a synergistic flame-retardant effect while exerting its electromagnetic shielding function. In addition, since the functional polymer is introduced by an in-situ chain extension reaction method, the mechanical properties of the polyurethane system are also improved. In addition, in the present invention, magnetic substances are filled in the polyurethane system and are regularly arranged through orientation treatment, thereby enhancing the electromagnetic shielding performance and also being beneficial to the improvement of the mechanical properties. Through the above technical solutions, the polyurethane elastomer finally prepared in the present invention realizes the synergistic improvement of mechanical properties, electromagnetic shielding performance and flame-retardant performance.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The polyurethane elastomer prepared in the present invention has both excellent flame-retardant performance and strong electromagnetic shielding performance, and has good mechanical properties, that is, it realizes the synergistic improvement of mechanical properties, electromagnetic shielding performance and flame-retardant performance.

[0032] 2. The preparation method of the present invention is simple and efficient, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The infrared spectra of the functional complex P-Er and Er(NO3)3·6H2O prepared in Preparation Example 1.

[0034] Figure 2 The infrared spectrum of the polyurethane elastomer (P-Er)-co-PU prepared in Step 2) of Example 1.

[0035] Figure 3 The heat release rate diagrams of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame-retardant and strong electromagnetic shielding effects prepared in Example 1 and the polyurethane elastomer TPU prepared in Comparative Example 4.

[0036] Figure 4Total heat release curve of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effects prepared in Example 1 and the polyurethane elastomer TPU prepared in Comparative Example 4.

[0037] Figure 5 Total smoke release curve of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effects prepared in Example 1 and the polyurethane elastomer TPU prepared in Comparative Example 4.

[0038] Figure 6 Electromagnetic shielding performance diagram of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effects prepared in Example 1.

[0039] Figure 7 Electromagnetic shielding performance diagram of the polyurethane elastomer TPU prepared in Comparative Example 4.

[0040] Figure 8 Stress-strain curve of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effects prepared in Example 1 and the polyurethane elastomer TPU prepared in Comparative Example 4. Detailed implementation mode

[0041] The present invention will be described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0042] In the following examples, the experimental methods are all conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0043] Polytetrahydrofuran glycol (PTMG), selected from Macklin Biochemical Technology Co., Ltd., with a number average molecular weight of 1500.

[0044] Preparation of functional complexes

[0045] Preparation Example 1

[0046] Add erbium nitrate hexahydrate (Er(NO3)3·6H2O) to ethanol, heat to 50 °C and stir to dissolve. After complete dissolution, add alendronic acid according to the molar ratio of Er(NO3)3·6H2O to alendronic acid of 1:2, adjust the pH value to 4.5, react at 75 °C for 5 h at a stirring speed of 150 rpm. After the reaction, filter, wash with pure water 3 times, and dry in vacuum at 90 °C for 12 h to obtain a white solid powder, that is, the functional complex, denoted as P-Er.

[0047] Preparation Example 2

[0048] The rest was the same as Preparation Example 1, except that the molar ratio of Er(NO3)3·6H2O to alendronic acid was 1:3.

[0049] Preparation Example 3

[0050] The rest was the same as Preparation Example 1, except that erbium chloride (ErCl3) was used to replace Er(NO3)3·6H2O, and phenylphosphonic acid was used to replace alendronic acid.

[0051] Comparative Preparation Example 1

[0052] The rest was the same as Preparation Example 1, except that nickel nitrate was used to replace Er(NO3)3·6H2O.

[0053] Example 1

[0054] A polyurethane elastomer with both flame retardant and strong electromagnetic shielding effects was prepared by the following preparation method:

[0055] 1) Add 10 g of 4,4′-diphenylmethane diisocyanate (MDI) to a 250 mL three-necked flask equipped with a thermometer and an electric stirrer paddle, and heat to 45 °C to completely melt the MDI; vacuum dehydrate polytetrahydrofuran ether glycol (PTMG) at 105 °C for 3 h, cool to room temperature to obtain dried PTMG, then add 40 g of dried PTMG to the above MDI, and stir and react at 80 °C for 1 h under nitrogen protection to obtain a terminal isocyanate group polyurethane prepolymer; tested by GPC, its number average molecular weight is about 2500, and the content of NCO measured according to HG / T 2409 is 3.36 wt%;

[0056] 2) Dissolve 1.2 g of the functional complex P-Er (prepared in Preparation Example 1) in 50 mL of DMF to form a functional complex solution, and then add the functional polymer solution to 40 g of the terminal isocyanate group polyurethane prepolymer, and carry out an in-situ chain extension reaction at 80 °C for 2 h. After the reaction, a polyurethane elastomer solution is obtained, denoted as (P-Er)-co-PU solution;

[0057] 3) Add 0.4 g of iron oxide to the polyurethane elastomer solution to form a mixture. Place the mixture on a polytetrafluoroethylene plate, and then place the polytetrafluoroethylene plate on a magnet plate with a magnetic field strength of 2500 gauss. Control the direction of the polytetrafluoroethylene plate to make the magnetic substances in the mixture arrange regularly; then keep the relative positions of the polytetrafluoroethylene plate containing the mixture and the magnet plate unchanged, and rotary evaporate for 2 h at 0.05 Mpa and 60 °C to remove the solvent, obtaining a polyurethane elastomer with both flame retardant and strong electromagnetic shielding effects, denoted as (P-Er)-co-PU / Fe.

[0058] Examples 2-3

[0059] The rest is the same as in Example 1, except that: the functional complexes in step 2) are respectively prepared according to Preparation Examples 2-3.

[0060] Example 4

[0061] The rest is the same as in Example 1, except that: the amount of the functional complex used in step 2) is 0.4 g.

[0062] Example 5

[0063] The rest is the same as in Example 1, except that: the amount of the functional complex used in step 2) is 2.0 g, and the amount of ferric oxide used in step 3) is 1.2 g.

[0064] Example 6

[0065] The rest is the same as in Example 1, except that: the amount of the functional complex used in step 2) is 2.8 g, and the amount of ferric oxide used in step 3) is 1.2 g.

[0066] Example 7

[0067] The rest is the same as in Example 1, except that: the amount of the functional complex used in step 2) is 4.0 g, and the amount of ferric oxide used in step 3) is 2.0 g.

[0068] Comparative Example 1

[0069] The rest is the same as in Example 1, except that: the functional complex in step 2) is prepared according to Comparative Preparation Example 1.

[0070] Comparative Example 2

[0071] The rest is the same as in Example 1, except that: the functional complex is not prepared, alendronic acid is directly added to the terminal isocyanate group polyurethane prepolymer for chain extension reaction, and erbium powder is added to the polyurethane in a blending manner, specifically:

[0072] 1) The same as in Example 1;

[0073] 2) 0.70 g of alendronic acid (close to the phosphorus element content in 1.2 g of the functional complex in Example 1) is mixed with 50 mL of DMF to form a mixed solution, and then the mixed solution is added to 40 g of the terminal isocyanate group polyurethane prepolymer, and in-situ chain extension reaction is carried out at 80 °C for 2 h, and after the reaction ends, a polyurethane elastomer solution is obtained;

[0074] 3) Add 0.23 g of erbium powder (close to the erbium element content in 1.2 g of the functional complex in Example 1) and 0.4 g of iron tetroxide to the polyurethane elastomer solution to form a mixture. Place it on a polytetrafluoroethylene plate, and then place the polytetrafluoroethylene plate on a magnet plate. Control the direction of the polytetrafluoroethylene plate to make the magnetic substances in the mixture arrange regularly; then keep the relative positions of the polytetrafluoroethylene plate containing the mixture and the magnet plate unchanged, and rotary evaporate to remove the solvent to obtain a polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect.

[0075] Comparative Example 3

[0076] The rest is the same as in Example 1, the difference is that: in step 3), magnetic orientation treatment is not carried out, specifically:

[0077] 1) The same as in Example 1;

[0078] 2) The same as in Example 1;

[0079] 3) Add 0.4 g of iron tetroxide to the polyurethane elastomer solution to form a mixture. Rotary evaporate the mixture at 0.05 Mpa and 60 °C for 2 h to remove the solvent to obtain an electromagnetic shielding and flame retardant polyurethane elastomer.

[0080] Comparative Example 4

[0081] The polyurethane is not modified at all, and a polyurethane elastomer is prepared using the conventional chain extender 1,4-butanediol, specifically:

[0082] 1) The same as in Example 1;

[0083] 2) Add 1.5 g (about 5% in excess, that is, completely react the NCO groups in the prepolymer) of 1,4-butanediol to 40 g of the terminal isocyanate group polyurethane prepolymer prepared in step 1), and carry out a chain extension reaction at 80 °C for 2 h. After the reaction is completed, a polyurethane elastomer is obtained, denoted as TPU.

[0084] Results and Analysis

[0085] 1. Structural Analysis

[0086] The infrared spectra of the functional complex P-Er and Er(NO3)3·6H2O prepared in Preparation Example 1 are as Figure 1 shown. It can be seen from Figure 1 that there is a peak of NO3 - (1480 cm -1 ) in Er(NO3)3·6H2O, while the peak of NO3 - (1480 cm -1 ) of P-Er disappears, and a peak of O-Er-O appears, indicating that Er(NO3)3·6H2O reacts with alendronic acid to form a complex.

[0087] The infrared spectrum of the polyurethane elastomer (P-Er)-co-PU prepared in step 2) of Example 1 is as follows Figure 2 shown. It can be seen from Figure 2 that in the infrared spectrum of (P-Er)-co-PU, the peak of NCO (2250 cm -1 ) disappears, proving that P-Er has been successfully introduced into the polyurethane molecular chain in the form of chemical bonds.

[0088] 2. Performance testing

[0089] ① Flame retardancy performance testing: The polyurethane elastomers prepared in the above-mentioned examples and comparative examples were subjected to flame retardancy performance testing. According to ISO 5660-1, a cone calorimeter was used to test the heat release rate, total heat release, and total smoke release. The specific test results are shown in Table 1. Among them, the heat release rate diagrams of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effects prepared in Example 1 and the polyurethane elastomer TPU prepared in Comparative Example 4 are as follows Figure 3 shown; the total heat release quantity curve diagrams of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effects prepared in Example 1 and the polyurethane elastomer TPU prepared in Comparative Example 4 are as follows Figure 4 shown; the total smoke release quantity curve diagrams of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effects prepared in Example 1 and the polyurethane elastomer TPU prepared in Comparative Example 4 are as follows Figure 5 shown.

[0090] It can be seen from Figure 3 that the maximum heat release rate of TPU prepared in Comparative Example 4 is 870 KW / m 2 , and the maximum heat release rate of (P-Er)-co-PU / Fe prepared in Example 1 is 621 KW / m 2 , which is about 30% lower than that of TPU prepared in Comparative Example 4. It can be seen from Figure 4 that the total heat release of TPU in Comparative Example 4 is 116 MJ / m 2 , and the total heat release of (P-Er)-co-PU / Fe prepared in Example 1 is 60 MJ / m 2 , which is about 50% lower than that of TPU in Comparative Example 4. It can be seen from Figure 5 that the total smoke release rate of TPU prepared in Comparative Example 4 is 9.5 m 2 , and the total smoke release of (P-Er)-co-PU / Fe prepared in Example 1 is 5.7 m 2 , which is about 40% lower than that of TPU in Comparative Example 4. The above data show that the polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effects prepared in Example 1 has good flame retardancy and smoke suppression effects.

[0091] ② Electromagnetic shielding performance test: The vector network analyzer coaxial method was used to test the electromagnetic shielding performance of the polyurethane elastomers prepared in each example and comparative example. The specific test results of electromagnetic reflection damage are shown in Table 1. The greater the absolute value of the reflection loss, the better the electromagnetic shielding performance. Among them, the electromagnetic shielding performance diagram of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effect prepared in Example 1 is as Figure 6 shown, and the electromagnetic shielding performance diagram of the polyurethane elastomer TPU prepared in Comparative Example 4 is as Figure 7 shown.

[0092] ③ Mechanical property test: A universal tensile testing machine was used to test the mechanical properties of the polyurethane elastomers prepared in each example and comparative example. The test results are shown in Table 1. Among them, the stress-strain curve diagrams of the polyurethane elastomer (P-Er)-co-PU / Fe with both flame retardancy and strong electromagnetic shielding effect prepared in Example 1 and the polyurethane elastomer TPU prepared in Comparative Example 4 are as Figure 8 shown. It can be seen from Figure 8 that the tensile strength of (P-Er)-co-PU / Fe prepared in Example 1 is significantly higher than that of TPU in Comparative Example 1.

[0093] Table 1 Comparison of mechanical properties, electromagnetic shielding properties and flame retardancy properties of each example

[0094]

[0095] It can be seen from Table 1 that the polyurethane elastomers prepared in each example of the present invention all have good flame retardancy and smoke suppression effects and electromagnetic shielding performance, and also have good mechanical properties. From the comparison data of Example 1 and Examples 4-7, it can be seen that with the increase of the dosage of the functional complex and the magnetic substance, the flame retardancy and electromagnetic shielding performance gradually increase, but the increase is not obvious after reaching a certain level; with the increase of the dosage of the functional complex and the magnetic substance, the mechanical properties increase to a certain extent and then decrease. Considering the economic cost and comprehensive performance, Example 1, Example 2, Example 5 and Example 6 are more excellent.

[0096] For the electromagnetic shielding and flame retardant polyurethane elastomer prepared by reacting the functional complex formed by coordinating nickel nitrate and alendronic acid used in Comparative Example 1 with the polyurethane prepolymer, although its mechanical properties are good, its flame retardancy and electromagnetic shielding performance are worse than those of the examples. The possible reason is that metal Er can catalyze the decomposition of the polymer at high temperature and promote the formation of a dense carbon layer, which can effectively isolate heat and oxygen, thus inhibiting combustion; while nickel can change the combustion path through catalytic action (such as promoting the oxidation of CO to CO2), but its carbon-forming ability is weak, and the flame retardant effect depends on other synergists; at the same time, compared with metal Ni, the electromagnetic shielding effect of metal Er is better.

[0097] Comparative Example 2 is an electromagnetic shielding and flame-retardant polyurethane elastomer prepared by directly adding alendronic acid to a polyurethane prepolymer for chain extension reaction and adding erbium powder to the system in a blending manner. It has good flame-retardant performance and electromagnetic shielding performance, but poor mechanical properties. The magnetic substance in Comparative Example 3 was not directionally arranged. The prepared electromagnetic shielding and flame-retardant polyurethane elastomer has good flame-retardant performance, but poor electromagnetic shielding performance, and its mechanical properties are also slightly worse than those of the examples. Comparative Example 4 is a conventional polyurethane elastomer prepared using a conventional chain extender and without any modification, and it has poor flame-retardant performance, electromagnetic shielding performance and mechanical properties.

[0098] In summary, the polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect prepared in the examples of the present invention realizes the synergistic improvement of mechanical properties, electromagnetic shielding performance and flame-retardant performance.

Claims

1. A polyurethane elastomer with both flame retardant and strong electromagnetic shielding effects, characterized in that, It is obtained by the in-situ chain extension reaction of a functional complex formed by the coordination reaction of an erbium(III) compound and a phosphoric acid compound with a terminal isocyanate group polyurethane prepolymer, adding a magnetic substance to the system, and then performing magnetic orientation treatment; the mass ratio of the functional complex to the terminal isocyanate group polyurethane prepolymer is (1-10):

100.

2. The polyurethane elastomer with both flame retardant and strong electromagnetic shielding effects according to claim 1, wherein The mass ratio of the functional complex, the magnetic substance, and the terminal isocyanate group polyurethane prepolymer is (3-7):(1-5):

100.

3. The polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect according to claim 1, characterized in that, The number average molecular weight of the terminal isocyanate group polyurethane prepolymer is 2000-5000; the terminal isocyanate group polyurethane prepolymer is obtained by reacting 4,4'-diphenylmethane diisocyanate (MDI) and polytetrahydrofuran ether glycol (PTMG) at a mass ratio of 1:(2.5-4.5) at 75-85 °C for 1-2 h; the number average molecular weight of the polytetrahydrofuran ether glycol is 1000-2000, and the water content is 10-50 ppm.

4. The polyurethane elastomer with both flame retardant and strong electromagnetic shielding effects according to claim 1, wherein The magnetic substance is at least one of iron tetroxide, neodymium iron boron alloy, aluminum nickel cobalt alloy, and samarium cobalt alloy, and the average particle size of the magnetic substance is 40-80 nm.

5. The polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect according to claim 1, characterized in that The molar ratio of the erbium(III) compound to the phosphoric acid compound is 1:(2-3).

6. The polyurethane elastomer with both flame retardant and strong electromagnetic shielding effects according to claim 1, wherein The erbium(III) compound is at least one of Er(NO3)3, ErCl3, and their hydrates, and the hydrates are Er(NO3)3·xH2O, ErCl3·xH2O, where x is an integer between 1 and 6; and / or The phosphoric acid compound is at least one of phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, phenylphosphoric acid, aminotrimethylenephosphonic acid, aminomethylphosphonic acid, alendronic acid, and pamidronic acid; preferably at least one of aminotrimethylenephosphonic acid, aminomethylphosphonic acid, alendronic acid, and pamidronic acid.

7. The polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect according to claim 1, characterized in that, The functional complex is prepared by a preparation method including the following steps: adding the erbium(III) compound and the phosphoric acid compound to a solvent, reacting at 60-90 °C within a pH range of 3-6 for 4-6 h, filtering, washing, and drying after the reaction to obtain the functional complex; Preferably, the solvent is ethanol or propanol; the washing is with pure water; the drying is vacuum drying at 80-100 °C for 12-24 h.

8. The polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect according to claim 1, wherein The conditions for the in-situ chain extension reaction are: reacting at 75-85 °C for 2-3 h.

9. The polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect according to claim 1, characterized in that, The magnetic field strength for the magnetic orientation treatment is 2000-3000 gauss.

10. The preparation method of the polyurethane elastomer having both flame retardant and strong electromagnetic shielding effects according to any one of claims 1-9, characterized in that, Including the following steps: 1) Heating and melting 4,4'-diphenylmethane diisocyanate, adding the dried polytetrahydrofuran ether glycol, and reacting by heating under an inert atmosphere protection. After the reaction, a terminal isocyanate group polyurethane prepolymer is obtained; 2) Dissolving the functional complex in a solvent to form a functional complex solution, and then adding the functional polymer solution to the terminal isocyanate group polyurethane prepolymer for in-situ chain extension reaction. After the reaction, a polyurethane elastomer solution is obtained; 3) Add magnetic substances to the polyurethane elastomer solution to form a mixture. Place the mixture on a plastic substrate, and then place the plastic substrate on a magnet plate with a magnetic field strength of 2000 - 3000 Gauss. Within the range of magnetic field strength of 2000 - 3000 Gauss, control the direction of the plastic substrate to make the magnetic substances in the mixture arrange regularly; then keep the relative positions of the plastic substrate with the mixture and the magnet plate unchanged, and rotary evaporate to remove the solvent to obtain a polyurethane elastomer with both flame retardancy and strong electromagnetic shielding effect; Preferably, in step 1), the drying conditions are: dehydrating at 105 - 115 °C under vacuum for 2 - 3 h; the temperature-rising reaction is carried out at 75 - 85 °C for 1 - 2 h; the inert atmosphere is nitrogen and / or argon; Preferably, in step 2), the solvent is at least one of N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA); Preferably, in step 3), the plastic substrate is a polytetrafluoroethylene plate; the conditions of rotary evaporation are: vacuum degree 0.01 - 0.08 Mpa, temperature 60 - 70 °C, time 2 - 3 h.

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