A lightweight flame-retardant and impact-resistant protective material and its preparation method

Abstract

The present invention belongs to the field of materials, specifically relating to a lightweight, flame-retardant, and impact-resistant protective material and its preparation method. The preparation method, based on a lightweight design, utilizes phosphorus-containing organosilane-functionalized hollow glass microspheres composited with shear-hardening gels of varying structures. This improves the severe cold flow properties of the shear-hardening gel while imparting lightweight, flame-retardant, and heat-resistant properties. The particle reinforcement effect and hollow structure of the phosphorus-containing organosilane-functionalized hollow glass microspheres are simultaneously utilized to enhance the shear storage modulus and energy absorption of the shear-hardening gel, resulting in the preparation of an impact-resistant, flame-retardant composite material with comprehensive properties such as strain rate response, impact hardening, energy dissipation, and flame retardancy and heat insulation.

Description

Technical Field

[0001] The present invention belongs to the field of materials, and in particular relates to a lightweight flame-retardant and impact-resistant protective material and a preparation method thereof. Background Art

[0002] Ubiquitous mechanical impact poses a potential risk to safety protection in transportation and sports applications. High-temperature fires, accompanied by thermal mechanical shocks such as building collapse and falling wood, also pose a significant threat to personal safety. Therefore, the development of advanced, high-performance, impact-resistant, flame-retardant protective materials to ensure personal safety is urgent.

[0003] Currently, most commonly used protective materials are based on alloys and ceramics. For example, alloy- or ceramic-based protective materials, such as bulletproof vests, are used to protect soldiers and police officers. However, this rigid armor neither effectively protects movable body parts (such as joints and the neck) nor provides the wearer with sufficient lightness and comfort. Therefore, combining strong impact resistance with comfortable, lightweight flexibility is crucial for protective materials.

[0004] It is based on this that the technical solution of the present invention is proposed. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention designs a lightweight flame-retardant and impact-resistant protective material and a preparation method thereof. By introducing phosphorus-containing organosilane functionalized hollow glass microspheres (HGM) into the impact-resistant shear hardening gel, a lightweight flame-retardant and impact-resistant shear reinforced gel protective material is obtained. While being lightweight, the protective material also has high energy dissipation and impact resistance, as well as flame retardant and heat-insulating properties. At the same time, a synthesis method is provided that is simple and easy to operate, has a short synthesis time, low energy loss, and uses inexpensive and readily available reagents.

[0006] The present invention provides a method for preparing a lightweight flame retardant and impact resistant protective material, the method comprising the following steps:

[0007] (1) mixing the hollow glass microspheres with the alkaline solution, and then filtering and drying to obtain pretreated hollow glass microspheres;

[0008] (2) adding the hollow glass microspheres to an ethanol aqueous solution, adding a silane coupling agent γ-aminopropyltriethoxysilane (KH550) under heating conditions, continuously stirring, centrifuging, washing, and drying in sequence to obtain hollow glass microspheres modified with a silane coupling agent;

[0009] (3) mixing the hollow glass microspheres modified with the silane coupling agent with a solvent, adding a solution of a phosphorus-containing flame retardant, reacting under heating conditions, centrifuging, washing, and drying in sequence to obtain phosphorus-containing organosilane functionalized hollow glass microspheres;

[0010] (4) The organosilicon material and the boric acid material are stirred and mixed, and then the phosphorus-containing organosilane functionalized hollow glass microspheres and methanol are added, and the temperature is raised to react under stirring conditions to obtain a mixture; the mixture is then poured into a mold and placed for molding to obtain a lightweight flame retardant and impact resistant protective material.

[0011] Preferably, in step (1), the particle size of the hollow glass microspheres is 20-100 μm;

[0012] and / or, the concentration of the alkaline solution is 1 to 10 wt %;

[0013] And / or, the alkaline solution is one or a combination of two or more of sodium hydroxide solution, ammonia solution, and sodium carbonate solution.

[0014] Preferably, in step (2), the concentration of ethanol in the ethanol aqueous solution is 10-40 vol%.

[0015] Preferably, in step (3), the phosphorus-containing flame retardant is one or a combination of two or more of ammonium polyphosphate (APP), hexachlorocyclotriphosphazene (HCCP), and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

[0016] Preferably, in step (4), the organosilicon material is hydroxyl-terminated polydimethylsiloxane (PDMS), and the viscosity of the organosilicon material is 20-25000 cst.

[0017] Preferably, in step (4), the boric acid material is one or a combination of two or more of tetrahydroxydiboron (B2H4O4), phenylboric acid (PhB(OH)2), and boric acid (H3BO3).

[0018] Preferably, in step (1), the mixing temperature is 80-85°C, the mixing time is 2-3 hours, and the drying time is 20-24 hours;

[0019] And / or, in step (2), the heating condition is heating to 70-75°C, and the stirring time is continuous for 2-3 hours;

[0020] And / or, in step (3), the heating condition is 60-80°C, and the reaction time is 2-8 h;

[0021] And / or, in step (4), the temperature of the temperature-raising reaction is 85-95°C.

[0022] Based on the same technical concept, the present invention further provides a lightweight flame retardant and impact resistant protective material obtained by the above preparation method.

[0023] The beneficial effects of the present invention are:

[0024] 1. In the modified hollow glass microspheres studied in the present invention, the active sites of Si-OH bonds are increased by alkali leaching treatment of the hollow glass microspheres, and the surface structure of the hollow microspheres is optimized, thereby having better mechanical properties and stability.

[0025] 2. The material prepared by this method is flame retardant and heat-insulating. At the same time, the microspheres are broken under dynamic impact, which is conducive to absorbing more kinetic energy. The flame retardant performance is affected differently. The stronger the interface interaction with the matrix, the higher the flame retardant performance and the better the impact effect.

[0026] 3. This method is applicable to hollow glass microspheres of different particle sizes, and can obtain modified hollow glass microspheres with different energy absorption properties; the shear thickening behavior and relaxation time scale of the outer layer shear-hardening gel with different structures have different effects on the impact performance of the protective material, but its impact resistance essence still lies in the unique BO dynamic bond, which makes its modulus increase significantly with the increase of external strain rate; the preparation method of the composite material by this method is simple and easy to operate, with a short synthesis time, low energy loss, and the reagents used are cheap and easily available. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 For infrared spectrum.

[0029] Figure 2 is the XRD pattern.

[0030] Figure 3 is a scanning electron microscope and elemental distribution map; among them:

[0031] Figure 3 a in the figure is a scanning electron microscope image of HGM after NaOH etching (Mag = 500X, i.e., magnification 500 times);

[0032] Figure 3 b is a scanning electron microscope image of HGM-APP after functional modification with a phosphorus-containing flame retardant (Mag = 500X, i.e., magnification 500 times);

[0033] Figure 3Figure c is a scanning electron microscope image of HGM-APP after functional modification with a phosphorus-containing flame retardant (Mag = 1500X, i.e., magnification 1500 times);

[0034] Figure 3 d in the figure is the distribution of elements on the surface of HGM-APP.

[0035] Figure 4 This is the modulus-frequency sweep curve. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] The present invention provides a method for preparing a lightweight flame-retardant and impact-resistant protective material, the preparation method comprising the following steps:

[0039] (1) 5 g of hollow glass microspheres (HGM) were added to 150 mL of NaOH solution (2 wt%), stirred at 85 °C for 2 h, filtered, and dried at room temperature for 24 h to obtain pretreated hollow glass microspheres;

[0040] (2) 2 g of the pretreated hollow glass microspheres were added to 40 mL of ethanol aqueous solution (30 vol%), 2 mL of KH550 was added at 75 °C, and the mixture was stirred for 2 h, followed by centrifugation, washing, and drying to obtain silane coupling agent-modified hollow glass microspheres (HGM-KH550);

[0041] (3) The HGM-KH550 was mixed and dispersed with water to obtain an HGM-KH550 dispersion (2 g / 40 mL); an ammonium polyphosphate (APP) aqueous solution (0.2 g / mL) was slowly dripped into the HGM-KH550 dispersion, reacted at 60°C for 2 h, and then centrifuged, washed, and dried to obtain HGM-APP;

[0042] (4) A 1:1 mass ratio of high viscosity (17,000-25,000 cSt) hydroxyl-terminated PDMS and a low viscosity (20-80 cSt) hydroxyl-terminated PDMS were added to a reactor, followed by the addition of B2H4O4, HGM-APP, and 40 mL of methanol. The mixture was heated to 90°C for reaction and vacuumed to obtain a mixture. The mixture was then poured into a mold and formed to obtain a lightweight flame-retardant and impact-resistant protective material. Among them, B2H4O4 accounted for 1 wt% of the total amount of PDMS, and HGM-APP accounted for 9 wt% of the total amount of PDMS.

[0043] Example 2

[0044] The present invention provides a method for preparing a lightweight flame-retardant and impact-resistant protective material, the preparation method comprising the following steps:

[0045] (1) 5 g of hollow glass microspheres HGM were added to 150 mL of NaOH solution (2 wt%), stirred at 85 °C for 2 h, filtered, and dried at room temperature for 24 h to obtain pretreated hollow glass microspheres;

[0046] (2) 2 g of the pretreated hollow glass microspheres were added to 40 mL of ethanol aqueous solution (30 vol%), 2 mL of KH550 was added at 75 °C, and the mixture was stirred for 2 h, followed by centrifugation, washing, and drying to obtain silane coupling agent-modified hollow glass microspheres (HGM-KH550);

[0047] (3) 2 g of the HGM-KH550 was mixed and dispersed with 150 mL of tetrahydrofuran (THF), and then 10 mL of triethylamine (TEA) was added and stirred under a nitrogen atmosphere for 1 h to obtain an HGM-KH550 dispersion; a THF solution of hexachlorocyclotriphosphazene (HCCP) (0.04 g / mL) was slowly dripped into the HGM-KH550 dispersion, and the mixture was reacted at 80°C for 8 h, and then centrifuged, washed, and dried to obtain HGM-PZE;

[0048] (4) A 1:1 mass ratio of high viscosity (17,000-25,000 cSt) hydroxyl-terminated PDMS and a low viscosity (20-80 cSt) hydroxyl-terminated PDMS were added to a reactor, followed by the addition of B2H4O4, HGM-PZE, and 40 mL of methanol. The mixture was heated to 90°C for reaction and vacuumed to obtain a mixture. The mixture was then poured into a mold and formed to obtain a lightweight flame-retardant and impact-resistant protective material. B2H4O4 accounted for 1 wt% of the total amount of PDMS, and HGM-PZE accounted for 9 wt% of the total amount of PDMS.

[0049] Example 3

[0050] The present invention provides a method for preparing a lightweight flame-retardant and impact-resistant protective material, the preparation method comprising the following steps:

[0051] (1) 5 g of hollow glass microspheres HGM were added to 150 mL of NaOH solution (2 wt%), stirred at 85 °C for 2 h, filtered, and dried at room temperature for 24 h to obtain pretreated hollow glass microspheres;

[0052] (2) 2 g of the pretreated hollow glass microspheres were added to 40 mL of ethanol aqueous solution (30 vol%), 2 mL of KH550 was added at 75 °C, and the mixture was stirred for 2 h, followed by centrifugation, washing, and drying to obtain silane coupling agent-modified hollow glass microspheres (HGM-KH550);

[0053] (3) The HGM-KH550 was mixed and dispersed with water to obtain an HGM-KH550 dispersion (2 g / 40 mL); an ammonium polyphosphate (APP) aqueous solution (0.2 g / mL) was slowly dripped into the HGM-KH550 dispersion, reacted at 60°C for 2 h, and then centrifuged, washed, and dried at room temperature to obtain HGM-APP;

[0054] (4) Add hydroxyl-terminated PDMS (2500-4000 cSt) to the reactor and heat it to 100°C. Add H3BO3 in small amounts and multiple times at a ratio of 1:1 between the hydroxyl-terminated PDMS and the hydroxyl group of boric acid (H3BO3). Add HGM-APP evenly while stirring. Continue heating to 150°C. After holding the temperature for 45 minutes, pour the mixture into a mold and cool it to obtain a lightweight flame-retardant and impact-resistant protective material. Among them, HGM-APP accounts for 9 wt% of the total PDMS.

[0055] Example 4

[0056] The present invention provides a method for preparing a lightweight flame-retardant and impact-resistant protective material, the preparation method comprising the following steps:

[0057] (1) 5 g of hollow glass microspheres HGM were added to 150 mL of NaOH solution (2 wt%), stirred at 85 °C for 2 h, filtered, and dried at room temperature for 24 h to obtain pretreated hollow glass microspheres;

[0058] (2) 2 g of the pretreated hollow glass microspheres were added to 40 mL of ethanol aqueous solution (30 vol%), 2 mL of KH550 was added at 75 °C, and the mixture was stirred for 2 h, followed by centrifugation, washing, and drying to obtain silane coupling agent-modified hollow glass microspheres (HGM-KH550);

[0059] (3) 2 g of the HGM-KH550 was mixed and dispersed with 150 mL of tetrahydrofuran (THF), and then 10 mL of triethylamine (TEA) was added and stirred under a nitrogen atmosphere for 1 h to obtain an HGM-KH550 dispersion; a THF solution of hexachlorocyclotriphosphazene (HCCP) (0.04 g / mL) was slowly dripped into the HGM-KH550 dispersion, and the mixture was reacted at 80°C for 8 h, and then centrifuged, washed, and dried to obtain HGM-PZE;

[0060] (4) Add hydroxyl-terminated PDMS (2500-4000 cSt) to the reactor and heat it to 100°C. Add H3BO3 in small amounts and multiple times at a ratio of 1:1 between the hydroxyl-terminated PDMS and the hydroxyl group of boric acid (H3BO3). Add HGM-PZE evenly while stirring. Continue heating to 150°C. After holding the temperature for 45 minutes, pour the mixture into a mold and cool it to obtain a lightweight flame-retardant and impact-resistant protective material. HGM-PZE accounts for 9 wt% of the total PDMS.

[0061] Comparative Example 1

[0062] High-viscosity (17,000-25,000 cSt) hydroxyl-terminated PDMS and low-viscosity (20-80 cSt) hydroxyl-terminated PDMS and B2H4O4 in a mass ratio of 1:1 were added to a reactor and stirred. B2H4O4 accounted for 1% of the total PDMS. The temperature was raised to 90°C for reaction, vacuum was applied, and the mixture was then poured into a mold and cooled to obtain a protective material.

[0063] Comparative Example 2

[0064] Add hydroxyl-terminated PDMS (2500-4000 cSt) into the reactor, raise the temperature to 100°C, add H3BO3 in small amounts and multiple times according to the ratio of hydroxyl-terminated PDMS to boric acid (H3BO3) hydroxyl group of 1:1, continue stirring and heat to 150°C, keep warm for 45 minutes, pour the mixture into a mold and cool it to obtain a protective material.

[0065] Verification Example

[0066] The materials of Examples 1 to 4 and Comparative Examples 1 to 2 were tested with a thickness of 1 mm. The test results are shown in Table 1.

[0067] Table 1

[0068]

[0069] To investigate the impact resistance of this protective material, a 4 g drop ball impact test was conducted at heights of 80 and 60 cm using a drop ball test apparatus equipped with a force sensor. A blank test specimen was used in which the drop ball directly contacted the force sensor during the impact test. The remaining test specimens were tested using a 1 mm thick sample sheet placed on the force sensor as a cushioning material. The test results in Table 1 show that when the force sensor is free of cushioning material (i.e., the blank specimen), the detected force increases instantaneously when the steel ball strikes the force sensor. In contrast, when the cushioning material is placed, the maximum force transmitted by the steel ball after impact is significantly reduced. At a height of 60 cm, the maximum force transmitted by Comparative Example 1 (59.51 N) is approximately 74% of that of Comparative Example 2 (80.42 N), indicating that Comparative Example 1 exhibits a higher force attenuation rate when used as a cushioning material. At the same addition level of phosphorus-modified hollow glass microspheres, Examples 1 and 2, which have a more stable diboron-oxygen bond structure, exhibit superior impact resistance compared to Examples 3 and 4, which have a single boron-oxygen bond structure, at different heights. Compared to the blank sample, Example 1 attenuated the maximum force transmitted by 96.4% and 93.6% at heights of 80 cm and 60 cm, respectively. Besides the interfacial interactions between the hollow glass microspheres modified with different phosphorus-containing flame retardants and the substrate, the shear hardening behavior exhibited by the supramolecular network of diboron-oxygen bonds is closer to that of a solid. This is due to the greater electron-deficiency of the boron atoms in the diboron structure, resulting in more coordinated states and higher bond energies for the diboron-oxygen coordination bonds. Microcalorimetric flame retardancy testing revealed that ammonium polyphosphate-modified hollow glass microspheres (Examples 1 and 3) were more effective in reducing the maximum heat release rate of the substrate than polyphosphazene-modified hollow glass microspheres (Examples 2 and 4), likely due to their interfacial interactions with the substrate and the combustion charring mechanism.

[0070] Furthermore, Figure 1 For infrared spectrum, Figure 1 It can be seen that HGM is at 799 and 1069 cm -1 The symmetric and antisymmetric stretching vibration peaks of Si-O-Si appeared at 463 cm -1 The bending vibration peak of Si-O-Si appears at 3471 cm -1 The stretching vibration peak of NH appears at 1035 cm -1 The stretching vibration peak of methoxy group appeared at 1092 cm, which indicated that the silane coupling agent KH550 had been grafted and modified HGM. -1 The newly added peak at is attributed to the POP bond. Infrared testing shows that phosphorus-functionalized hollow glass microspheres have been successfully prepared.

[0071] Figure 2 is the XRD pattern, from which Figure 2 it can be seen that: for the X-ray diffraction (XRD) patterns of HGM and HGM-APP, the broad peaks at 2θ = 15 - 35º belong to amorphous silica. The basic broad peak morphology of the HGM-APP curve after the hollow glass microspheres are functionalized and modified with phosphorus at 2θ = 15 - 35º has not changed significantly, while new diffraction peaks attributed to APP appear at 2θ = 11.58º, 23.2º, 30.52º and 35.34º.

[0072] Figure 3 are the scanning electron microscope and element distribution maps, from which Figure 3 it can be seen that: the surface of HGM after being etched by NaOH is rough, with a small amount of tiny particles attached ( Figure 3 a in). After being functionalized and modified with a phosphorus-containing flame retardant, there are obvious protrusions on the surface of HGM-APP ( Figure 3 b in), and it can be observed under magnification that the surface of a single HGM-APP is non-uniformly covered with layered substances of different thicknesses ( Figure 3 c in), which is the reason for the successful coating of APP. In addition, using an energy dispersive spectrometer (EDS) to test the element distribution on the surface of HGM-APP, it is found that the coating layer on the surface of HGM-APP contains O, P, C and N elements ( Figure 3 d in). Among them, the P element comes from APP, the N element mainly comes from APP and KH550, and the C element comes from KH550. The element distribution indicates that the phosphorus-containing flame retardant APP has been successfully grafted and modified HGM.

[0073] Figure 4 is the modulus-frequency scanning curve graph, specifically the oscillatory frequency scanning of pure PDBS from 0.01 to 100 Hz at different temperatures (0, 20, 40, 60 and 80 °C). The results show that PDBS is a shear-enhanced material with a frequency-dependent viscoelastic modulus. The storage modulus (G′) increases linearly at low frequencies and then reaches a plateau, while the loss modulus (G′′) reaches a maximum near the transition point of G´. There is an angular frequency ω c at the intersection point where G′′ is equal to G'. When ω < ω c , PDBS is in a liquid state (G′ < G′′), and when ω > ω c , PDBS is in a solid state (G′ > G′′). The intersection frequency gradually increases with the increase in temperature, indicating that PDBS gradually changes from an elastic to a viscous property with the increase in temperature.

[0074] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a lightweight flame retardant and impact resistant protective material, characterized in that: The preparation method comprises the following steps: (1) mixing the hollow glass microspheres with the alkaline solution, and then filtering and drying to obtain pretreated hollow glass microspheres; (2) adding the hollow glass microspheres to an ethanol aqueous solution, adding a silane coupling agent γ-aminopropyltriethoxysilane under heating conditions, continuously stirring, centrifuging, washing, and drying in sequence to obtain hollow glass microspheres modified with a silane coupling agent; (3) mixing the hollow glass microspheres modified with the silane coupling agent with a solvent, adding a solution of a phosphorus-containing flame retardant, reacting under heating conditions, centrifuging, washing, and drying in sequence to obtain phosphorus-containing organosilane functionalized hollow glass microspheres; wherein the phosphorus-containing flame retardant is ammonium polyphosphate or hexachlorocyclotriphosphazene; (4) The organosilicon material and the boric acid material are stirred and mixed, and then the phosphorus-containing organosilane functionalized hollow glass microspheres and methanol are added, and the temperature is raised to react under stirring conditions to obtain a mixture; the mixture is then poured into a mold and placed for molding to obtain a lightweight flame retardant and impact resistant protective material; wherein: The organosilicon material is hydroxyl-terminated polydimethylsiloxane, and the viscosity of the organosilicon material is 20-25000 cSt; the organosilicon material is composed of high-viscosity hydroxyl-terminated polydimethylsiloxane and low-viscosity hydroxyl-terminated polydimethylsiloxane in a mass ratio of 1:1; the high viscosity is 17000-25000 cSt, and the low viscosity is 20-80 cSt; The boric acid material is tetrahydroxydiboron.

2. The method for preparing a lightweight flame retardant and impact resistant protective material according to claim 1, characterized in that: In step (1), the particle size of the hollow glass microspheres is 20-100 μm; and / or, the concentration of the alkaline solution is 1-10 wt%; And / or, the alkaline solution is one or a combination of two or more of sodium hydroxide solution, ammonia solution, and sodium carbonate solution.

3. The method for preparing a lightweight flame retardant and impact resistant protective material according to claim 1, characterized in that: In step (2), the concentration of ethanol in the ethanol aqueous solution is 10-40 vol%.

4. The method for preparing a lightweight flame retardant and impact resistant protective material according to claim 1, characterized in that: In step (1), the mixing temperature is 80-85°C, the mixing time is 2-3 hours, and the drying time is 20-24 hours; And / or, in step (2), the heating condition is heating to 70-75°C, and the stirring time is continuous for 2-3 hours; And / or, in step (3), the heating condition is 60-80°C, and the reaction time is 2-8 hours; And / or, in step (4), the temperature of the temperature-raising reaction is 85-95°C.

5. The lightweight flame retardant and impact resistant protective material obtained by the preparation method according to any one of claims 1 to 4.

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