A method for preparing explosion-proof glass

Abstract

The present invention discloses a preparation method of explosion-proof glass, which includes arranging a first layer of glass, a second layer of glass and a polyurethane layer. The first layer of glass is used as the inner layer of the laminated glass, and the polyurethane layer is modified and set as an impact dispersion layer to disperse stress. Through the self-assembly grid and honeycomb foaming structure of Fe3O4 nanoparticles induced by a magnetic field, multi-level energy dissipation is achieved, local stress concentration is reduced, and the overall brittle fracture of the glass is prevented, so that the glass can still maintain integrity after fracture and prevent fragment scattering. The second layer of glass is introduced with an asymmetric prestress distribution and stress concentration design to concentrate the impact energy to a preset point, so that the glass fragments can further generate impact force to crush the polyurethane layer and the first layer of glass, enabling the external impact to quickly penetrate the laminated glass and cause the fragments to fall, providing a rapid access channel for rescue personnel and improving the rescue efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of glass preparation, and particularly to a preparation method of explosion-proof glass. Background Art

[0002] With the development of society, glass, as a widely used material in fields such as architecture, transportation, and household appliances, its safety issues have attracted increasing attention. Although traditional glass performs excellently in terms of transparency, strength, etc., when subjected to external impact or pressure, it is prone to breakage, generating a large number of sharp glass fragments. The scattering of these fragments not only poses serious safety hazards but may also cause harm to the human body or surrounding objects. Especially in application scenarios such as high-rise buildings, vehicle windows, airplane windows, and transportation, the harm of broken glass to personnel and the environment is more prominent.

[0003] Existing explosion-proof glass technologies mostly improve the impact resistance and anti-fragmentation performance of glass by means such as sandwich design, toughening treatment, and toughening materials. Common explosion-proof glasses include tempered glass and laminated glass. Tempered glass increases its surface stress through special heating and rapid cooling treatment, so that when it is subjected to external force impact, it can break into small particles, reducing harm. However, once tempered glass breaks, the entire glass will break quickly, resulting in larger fragments, making it difficult to effectively prevent the scattering of fragments. Laminated glass, on the other hand, sandwiches a plastic film (such as PVB film, EVA film, etc.) between two layers of glass, so that the glass can still maintain integrity after breaking, preventing the scattering of fragments. Although laminated glass performs excellently in preventing the scattering of fragments, its impact resistance is still limited. Especially when subjected to strong impact, the glass layer may break, and the sandwich film may not be able to effectively withstand the strong impact, resulting in the glass fragments still falling.

[0004] In order to prevent the glass from breaking and falling due to internal personnel colliding with the glass at high altitude, the high-altitude glass needs to ensure that the glass still maintains integrity after breaking. And in some special cases (such as fires), during high-altitude rescue by rescue personnel, it is necessary to crush the glass from the outside so that the glass completely breaks and falls. If the glass still maintains integrity when broken outside, it will affect the rescue speed.

[0005] Therefore, it is necessary to design a preparation method of explosion-proof glass on how to improve the impact resistance of glass, enhance the fragment control ability after glass breakage, and maintain good protection effects under different impact directions. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a preparation method of explosion-proof glass.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A preparation method of explosion-proof glass, comprising the following steps:

[0008] Step S1: Mix silicon dioxide, sodium oxide, calcium oxide, aluminum oxide, and potassium carbonate evenly in proportion, and heat until in a molten state to obtain a liquid glass matrix.

[0009] Step S2: Divide the liquid glass matrix into two parts, perform a shaping process on one part of the liquid glass matrix to obtain the first layer of glass.

[0010] Step S3: Apply a directional stress to the other part of the liquid glass matrix to form a stress concentration layer and obtain the second layer of glass.

[0011] Step S4: Prepare a polyurethane layer as an impact dispersion layer, and press the first layer of glass and the second layer of glass together with the polyurethane layer to prepare laminated glass.

[0012] In a preferred embodiment of the present invention, in the step S1, glass substrate raw materials are selected, including 100 parts by weight of quartz sand, 15 - 20 parts of sodium oxide, 10 - 15 parts of calcium oxide, 5 - 12 parts of potassium carbonate, and 1.5 - 5.5 parts of aluminum oxide.

[0013] In a preferred embodiment of the present invention, in the step S1, 0.1 - 0.2 parts of sodium nitrate and 0.5 - 1 part of carbon powder are added to the glass substrate raw materials and mixed evenly, and melted at 1550 - 1600 °C for 4 - 6 h to obtain a liquid glass matrix.

[0014] In a preferred embodiment of the present invention, in the step S2, the shaping process includes the following steps:

[0015] Step S21: Introduce the liquid glass matrix into a shaping mold and flatten it by gravity to form a flat glass.

[0016] Step S22: Cool the flat glass at a rate of 3 °C / min to 300 - 350 °C.

[0017] Step S23: Immerse the flat glass in a KNO3 molten salt bath at 400 - 450 °C for 6 - 8 h for ion exchange.

[0018] Step S24: Cool the flat glass with completed ion exchange to room temperature at a rate of 10 °C / min, and ultrasonically clean it with deionized water to remove surface salt residues to obtain the first layer of glass.

[0019] In a preferred embodiment of the present invention, in the step S23, the KNO3 molten salt composition includes: KNO3 and NaNO3; and the mass ratio between KNO3 and NaNO3 is 95 - 97:3 - 5.

[0020] In a preferred embodiment of the present invention, in the step S3, it includes the following sub - steps:

[0021] Step S31: Introduce the liquid glass matrix into the forming mold and flatten it by gravity to form flat glass;

[0022] Step S32: Immerse side A of the flat glass into a KNO3 molten salt bath at 450°C - 480°C for 6 - 8 hours to form a deep high potassium ion concentration gradient of 65 - 80 μm;

[0023] Step S33: Immerse side B of the flat glass into a KNO3 molten salt bath with a mass ratio of KNO3 to NaNO3 of 95:3 between 350°C - 380°C for 2 - 2.5 hours to form a shallow and uniform potassium ion penetration layer of 15 - 20 μm;

[0024] Step S34: Position the center of side A of the flat glass after ion exchange at the preset stress concentration point;

[0025] Step S35: Cool side A of the flat glass after completing step S34 by high - speed nitrogen jet with a wind speed of 25 - 30 m / s and a cooling rate of 100 - 120°C / s, and cool side B by natural convection with a cooling rate of 40 - 50°C / s to form an asymmetric stress distribution layer, obtaining the second - layer glass.

[0026] In a preferred embodiment of the present invention, in the step S34, the setting of the stress concentration point includes: etching an array of micro - holes in the central region of side A of the flat glass with femtosecond laser at a wavelength of 1030 nm. Among them, each micro - hole is a conical structure with a diameter of 45 - 50 μm and a depth of 95 - 100 μm, and is uniformly arranged in a hexagonal symmetric distribution pattern, and the center - to - center distance between adjacent micro - holes is 480 - 500 μm.

[0027] In a preferred embodiment of the present invention, in the step S4, preparing the polyurethane layer includes the following steps:

[0028] Step S41: Mix polyether polyol and isocyanate in a mass ratio of 1 - 2:1.5 - 4 and react at 50 - 65°C to generate a polyurethane prepolymer containing dynamic bonds;

[0029] Step S42: Add an amphiphilic block copolymer, nanocrystalline cellulose whiskers and Fe3O4 particles to the polyurethane prepolymer and mix at a rotation speed of 2000 rpm for 30 - 35 minutes to obtain a mixed slurry;

[0030] Step S43: Inject the mixed slurry into the mold, place it in a uniform magnetic field of 0.5 - 0.8 T, drive the Fe3O4 particles to align along the magnetic induction lines, and drive the nanocrystalline cellulose whiskers to form a grid - like structure;

[0031] Step S44, adding azodicarbonamide and raising the temperature to 75-85° C. to generate honeycomb holes, inducing the amphiphilic copolymer to self-assemble at the gas-liquid interface to form a three-dimensional interpenetrating network and an impact dispersion layer;

[0032] Step S45, adjusting the ultraviolet intensity by region, curing at 110-125° C. for 1.5-2 h, and annealing for 24 h to obtain a polyurethane layer.

[0033] In a preferred embodiment of the present invention, the thickness of the first layer of glass is 5.8-6.2 mm, the thickness of the second layer of glass is 5.8-6.2 mm, and the thickness of the polyurethane layer is 0.7-1.2 mm.

[0034] In a preferred embodiment of the present invention, in step S4, a polyurethane layer is placed between a first layer of glass and a second layer of glass, and laminated glass is prepared by vacuum hot pressing.

[0035] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0036] (1) The present invention provides a method for preparing explosion-proof glass, which uses ion exchange strengthening treatment to introduce potassium ions into the surface layer of the glass to form a high surface compressive stress layer, thereby improving the impact resistance and preventing slight impact from causing breakage. Through asymmetric prestress distribution, ion penetration layers of different depths are formed on both sides of the glass, and differential cooling is used to form a stress gradient inside the glass. When impacted, the cracks can be guided to expand in a directional manner to prevent overall breakage. At the same time, an impact dispersion layer is added to quickly absorb and diffuse stress, prevent glass fragments from splashing, and maintain the integrity of the glass. The nano-enhanced network in the impact dispersion layer further enhances the adhesion and avoids the risk of broken glass falling.

[0037] (2) The present invention provides a method for preparing explosion-proof glass, comprising arranging a first layer of glass, a second layer of glass and a polyurethane layer, wherein the first layer of glass is used as the inner layer of the laminated glass, and the polyurethane layer is modified and arranged as an impact dispersion layer and a diffusion stress layer, and a magnetic field is induced to induce a self-assembled grid of Fe3O4 nanoparticles and a honeycomb foaming structure to achieve multi-level energy dissipation, reduce local stress concentration, and prevent the overall brittle fracture of the glass, and significantly improve the adhesion and toughness of the dispersion layer, so that the glass can still maintain its integrity after fracture, and prevent the fragments from flying, and introduce an asymmetric prestress distribution into the second layer of glass, and form a shallow high-pressure stress gradient through short-term ion exchange at low temperature on the A side, and form a deep uniform compressive stress on the B side through long-term treatment at high temperature, and combine with laser etching to preset a micropore array, so as to concentrate the impact energy to a preset point, so that the glass fragments can further generate impact force, crush the polyurethane layer and the first layer of glass, so that the external impact can quickly penetrate the laminated glass, causing the fragments to fall, providing a quick access channel for rescue personnel, and improving the rescue efficiency.

[0038] (3) In the present invention, under the induction of a magnetic field, Fe3O4 particles are driven to drive the alignment of nanocrystalline cellulose whiskers along the direction of magnetic induction lines, thereby forming a grid-like structure inside the material. When impacted, the external force can be quickly dispersed, and the impact energy is conducted along the chain-like path between the nanofibers and Fe3O4 particles, effectively reducing local stress concentration, thereby enhancing the overall impact resistance and dispersion performance. At the same time, by introducing azodicarbonamide foaming agent, micron-sized honeycomb pores are generated during the heating and foaming stage, enabling the amphiphilic block copolymer to self-assemble at the gas-liquid interface to form a three-dimensional interpenetrating network, firmly locking the glass fragments when the glass breaks, endowing the polyurethane layer with strong adhesion ability, and effectively preventing the fragments from falling off.

[0039] (4) In the present invention, through the design of asymmetric prestress distribution and stress concentration for the second layer of glass, a stress gradient structure is formed. When externally impacted, the prestress distribution can transfer the external force inward and concentrate it at specific stress concentration points of the glass, inducing a strong local stress concentration effect when the glass breaks. This breaking point will further transmit stress in the direction of the impact, thereby triggering a larger range of glass breakage, effectively enhancing the overall destructive force, driving the entire interlayer to break and causing the glass fragments to fall off, thus ensuring the smooth opening of the rescue passage. At the same time, the impact direction of the glass fragments is controlled to avoid the danger caused by the high-altitude fall of the fragments. Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0041] Figure 1 It is a flowchart of a preparation method for an explosion-proof glass of the present invention. Detailed Embodiments

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0043] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0044] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the protection scope of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more than two.

[0045] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific situations.

[0046] As Figure 1 shown, a method for preparing explosion-proof glass includes the following steps:

[0047] Step S1: Mix silica, sodium oxide, calcium oxide, alumina, and potassium carbonate evenly in proportion and heat until in a molten state to obtain a liquid glass matrix.

[0048] Step S2: Divide the liquid glass matrix into two parts, and perform a shaping process on one part of the liquid glass matrix to obtain the first layer of glass.

[0049] Step S3: Apply a directional stress to the other part of the liquid glass matrix to form a stress concentration layer to obtain the second layer of glass.

[0050] Step S4: Prepare a polyurethane layer as an impact dispersion layer, and press the first layer of glass and the second layer of glass with the polyurethane layer to prepare laminated glass.

[0051] In the present invention, the thickness of the first layer of glass is 5.8 - 6.2 mm, the thickness of the second layer of glass is 5.8 - 6.2 mm, and the thickness of the polyurethane layer is 0.7 - 1.2 mm.

[0052] In the step S1, raw materials for the glass substrate are selected, which include 100 parts by weight of quartz sand, 15 - 20 parts of sodium oxide, 10 - 15 parts of calcium oxide, 5 - 12 parts of potassium carbonate, and 1.5 - 5.5 parts of aluminum oxide. Add 0.1 - 0.2 parts of sodium nitrate and 0.5 - 1 part of carbon powder to the raw materials for the glass substrate and mix them evenly. Melt at 1550 - 1600 °C for 4 - 6 h to obtain a liquid glass matrix. During the melting stage, sodium nitrate and carbon powder can be added. The role of sodium nitrate is to help improve the fluidity of the glass matrix, while carbon powder helps reduce the viscosity of the glass during melting and is beneficial to improving the surface flatness of the glass.

[0053] Silicon dioxide: sourced from Jiangsu Lianrui New Materials Co., Ltd., with a purity of ≥99.5%

[0054] Sodium oxide: sourced from Jiangsu Bost Chemical Technology Co., Ltd., with a purity of 80%

[0055] Calcium oxide: sourced from Anhui Conch Cement Co., Ltd., with a purity of ≥98%

[0056] Aluminum oxide: sourced from Aluminum Corporation of China Limited, with a purity of ≥99.9%

[0057] Potassium carbonate: sourced from Qinghai Salt Lake Industry Co., Ltd., with a purity of ≥99% and a Cl⁻ content of ≤0.01%

[0058] Carbon powder: sourced from Shanghai Haoyue Electric Furnace Technology Co., Ltd., HY - CP200 (high - purity carbon powder, ash content ≤0.5%)

[0059] Sodium nitrate: sourced from Shanghai Merck Chemical Technology Co., Ltd., with a purity of ≥98.5%.

[0060] In the step S2, divide the liquid glass matrix obtained in the step S1 into two equal parts and carry out forming by different forming processes on the two parts of the liquid glass matrix. Perform forming treatment on one part of the liquid glass matrix to obtain the first - layer glass. Among them, the forming treatment of the first - layer glass includes the following steps:

[0061] Step S21: Introduce the liquid glass matrix into a forming mold and form a flat glass by gravity spreading.

[0062] Step S22: Cool the flat glass at a rate of 3 °C / min to 300 - 350 °C to slowly release the internal stress of the glass evenly and avoid residual stress concentration.

[0063] Step S23: Immerse the flat glass in a KNO3 molten salt bath at 400 - 450 °C for 6 - 8 h for ion exchange.

[0064] By immersing flat glass in a KNO₃ molten salt bath at 400°C - 450°C, the surface strength of the glass is enhanced. Through ion exchange with potassium ions in the molten salt, a high-pressure stress layer will form on the glass surface, thereby improving its impact resistance and crack resistance. The ion exchange process lasts for 6 - 8 hours to ensure that potassium ions can fully penetrate the glass surface and form a relatively deep potassium ion enrichment layer;

[0065] Step S24: The flat glass after ion exchange treatment needs to be slowly cooled again to avoid thermal stress caused by excessive temperature difference. The flat glass after ion exchange is cooled to room temperature at a rate of 10°C / min. After ion exchange, a certain amount of salts will adhere to the glass surface, especially unreacted KNO₃ or its by-products. To remove these residual salts, ultrasonic cleaning with deionized water is used, which can effectively remove the salt stains on the glass surface and prevent them from affecting subsequent processes.

[0066] The composition of the KNO₃ molten salt includes: KNO₃ and NaNO₃; and the mass ratio between KNO₃ and NaNO₃ is 95 - 97:3 - 5.

[0067] In the present invention, in the said step S3, it includes the following sub-steps:

[0068] Step S31: Pour the liquid glass matrix into a forming mold and flatten it by gravity to form flat glass;

[0069] Step S32: Immerse side A of the flat glass in a KNO₃ molten salt bath at 450°C - 480°C for 6 - 8 h. Through ion exchange with potassium ions in the molten salt, a deep high-potassium ion concentration gradient will form on the glass surface and last for 6 - 8 hours to ensure that potassium ions penetrate deep enough on the surface of side A of the glass to form a relatively strong compressive stress layer, which helps the glass maintain structural stability during subsequent cooling and avoid cracks on the surface. Among them, the main purpose of the shallow high-potassium ion concentration gradient is to introduce compressive stress on the glass surface and enhance the impact resistance and crack resistance of the glass. The introduction of potassium ions will cause compressive stress on the glass surface, thereby improving its crack resistance;

[0070] Step S33: Different from the treatment of side A, a deeper ion exchange treatment is carried out on side B (i.e., the other side of the glass). Immerse side B of the flat glass in a KNO₃ molten salt bath at 350°C - 380°C with a mass ratio of KNO₃ to NaNO₃ of 95:3 for 2 - 2.5 h to form a 15 - 20 μm shallow and uniform potassium ion penetration layer. This process aims to enable side B of the glass to deeply penetrate potassium ions, make the compressive stress layer on side B of the glass deeper and more uniform, thereby greatly improving the overall compressive resistance and crack resistance of the glass. The deep high-potassium ion concentration helps guide cracks to expand along the stress gradient when the glass is impacted, rather than having a sudden breakthrough of cracks;

[0071] Step S34: Position the center of side A of the flat glass after ion exchange at the preset stress concentration point to help guide the impact energy to a specific preset point, so that the glass is more likely to break along the predetermined path under the action of external force;

[0072] Step S35: Cool the side A of the flat glass that has completed step S34 by high-speed nitrogen injection with a wind speed of 30 m / s and a cooling rate of 120 °C / s to ensure that the surface of side A cools rapidly and forms a high surface stress. The side B is cooled by natural convection at a cooling rate of 50 °C / s, so that different depths of stress layers are generated on side A and side B, thereby forming an asymmetric stress distribution of the glass and forming an asymmetric stress distribution layer to obtain the second-layer glass;

[0073] Among them, the rapid cooling of side A will form a surface compressive stress layer, while the slow cooling of side B will form a deeper tensile stress layer. The asymmetric stress distribution can guide the impact force to the preset stress concentration point when the glass is externally impacted, thereby achieving the effect of positioning and breaking, and further generating a further impact force to crush the polyurethane layer and the first-layer glass, so that the external impact can quickly penetrate the laminated glass and make the fragments fall, providing a fast entry channel for rescue personnel and improving the rescue efficiency.

[0074] In the present invention, in the step S34, the setting of the stress concentration point includes: etching an array of microholes in the central region of side A of the flat glass with femtosecond laser of 1030 nm wavelength. Among them, each microhole is a conical structure with a diameter of 45 - 50 μm and a depth of 95 - 100 μm, and is uniformly arranged in a hexagonal symmetric distribution pattern, and the center distance between adjacent microholes is 480 - 500 μm.

[0075] The setting of the microhole array plays a role in guiding the cracking path. When the glass is impacted, the crack usually expands along the position of the microholes. As the stress concentration point, the microholes can concentrate the external impact energy on the microholes, so that the crack spreads along these microholes, effectively preventing the glass from having disordered crack expansion, ensuring that the crack expands along the predetermined path, thereby avoiding the generation of irregular cracks in the glass under the action of external force, and further being able to generate a greater impact force when broken;

[0076] When it is not necessary to break the glass, but the glass is impacted due to external factors, the setting and arrangement of the microholes can not only guide the expansion of the crack, but also absorb the external impact energy to a certain extent and slow down the energy transfer speed, thereby improving the impact resistance of the glass. Under the action of external force, the crack will first expand from the microholes and will not directly penetrate the entire glass surface, avoiding the glass from instantly shattering under external impact and ensuring the toughness of the glass.

[0077] It should be noted that by controlling the arrangement and depth of the micro-holes, when the glass breaks, it can exhibit a certain predetermined fracture pattern. Therefore, when it breaks, the fragments can spread along the path of the impact direction, avoiding the fragments flying around or falling, and causing harm to the surrounding environment and personnel. Moreover, the design of the micro-holes can make the glass break into smaller fragments under the action of external force instead of large pieces, ensuring that the broken glass is easier to control.

[0078] In the present invention, in the step S4, preparing the polyurethane layer includes the following steps:

[0079] Step S41: Mix polyether polyol and isocyanate in a mass ratio of 1 - 2:1.5 - 4, and react at 50 - 65 °C to generate a polyurethane prepolymer containing dynamic bonds. Specifically, the dynamic bond is that the hydroxyl group in the polyether polyol reacts with the isocyanate group in the isocyanate to form a urethane bond. This prepolymer has certain elasticity and adhesiveness and can better bond with the glass layer;

[0080] Step S42: Add an amphiphilic block copolymer, nanocrystalline cellulose whiskers and Fe3O4 particles into the polyurethane prepolymer, and mix at a rotation speed of 2000 rpm for 30 - 35 min to obtain a mixed slurry;

[0081] Nanocrystalline cellulose whiskers can improve the toughness and adhesiveness of the polyurethane layer and enhance the strength of the overall structure; by introducing Fe3O4 particles, the Fe3O4 particles are induced to arrange in the prepolymer under the magnetic field to form a grid-like structure, which can enhance the conductivity and magnetism of the polyurethane layer and also play a positive role in absorbing impact energy;

[0082] Step S43: Inject the mixed slurry into a mold, place it in a uniform magnetic field of 0.5 - 0.8 T, drive the Fe3O4 particles to arrange along the magnetic induction lines, and drive the nanocrystalline cellulose whiskers to form a quasi-grid structure, which can effectively disperse the impact force and enhance the overall toughness of the material;

[0083] Step S44: Add azodicarbonamide and raise the temperature to 75 - 85 °C to generate honeycomb pores, induce the amphiphilic copolymer to self-assemble at the gas-liquid interface to form a three-dimensional interpenetrating network, and form an impact dispersion layer;

[0084] Step S45: Regionally regulate the ultraviolet intensity, cure at 110 - 125 °C for 1.5 - 2 h, and anneal for 24 h to obtain the polyurethane layer.

[0085] Polyether polyol: Select polyoxypropylene glycol, sourced from Wanhua Chemical Group Co., Ltd. (model: PPG - 2000);

[0086] Isocyanate: Select toluene diisocyanate, sourced from Cangzhou Dahua Co., Ltd. (model: TDI - 80);

[0087] The amphiphilic block copolymer is specifically: polyethylene glycol-b-polypropylene glycol-b-polyethylene glycol, sourced from Beijing Research Institute of Chemical Industry, Sinopec (model: F127);

[0088] The size of the nanocellulose whiskers is 20 ± 5 nm in diameter and 1.2 ± 0.3 μm in length, sourced from Shandong Quanlin Paper Co., Ltd.;

[0089] Fe3O4 particles: sourced from Shanghai Aladdin Biochemical Technology Co., Ltd., with a particle size of 50 - 100 nm and a purity of ≥99.9%.

[0090] Among them, the polyurethane layer, as the intermediate layer in the laminated glass, has extremely strong impact dispersion ability. When the glass is impacted by external factors without being broken, the polyurethane layer can quickly absorb the impact energy and spread it throughout the layer, thereby reducing the local impact force on the glass surface and enabling the overall structure of the glass to maintain a high impact resistance. Even when encountering a large impact, the glass will break locally rather than shatter as a whole, thus ensuring that when the glass inside a high-rise building is impacted and broken, through the adhesive property of the polyurethane layer, the whole glass can still remain intact, effectively maintaining the adhesion of the glass fragments, preventing the fragments from flying, and avoiding the fragments falling from a height and causing harm to the people on the ground.

[0091] Regarding the impact dispersion performance of the polyurethane layer, the honeycomb hole structure inside can not only enhance the lightweight characteristics of the material but also further improve its impact energy absorption effect. The micron-sized holes can absorb part of the impact energy through the compression effect when being impacted and reduce the local stress concentration when the glass breaks.

[0092] During the preparation process, the Fe3O4 particles in the polyurethane layer are placed in a magnetic field, making the Fe3O4 particles arrange along the magnetic induction line direction, and at the same time driving the nanocellulose whiskers to arrange directionally to form a grid-like structure, which improves the mechanical properties of the polyurethane layer, mainly reflected in:

[0093] The grid structure improves the toughness of the material: The directionally arranged nanocellulose whiskers and Fe3O4 particles form a grid structure with enhanced mechanical properties. When being impacted, this structure can effectively disperse the external force and conduct the energy through the chain-like path between the nanocellulose and Fe3O4 particles, thereby reducing the stress concentration;

[0094] Prevent crack propagation: The grid structure has high toughness and can effectively prevent crack propagation. When microcracks occur in the glass, the grid structure will play a constraining role, restricting the crack from spreading to a wider area and preventing large-area fragment scattering when the glass breaks.

[0095] It should be noted that the amphiphilic block copolymer added to the polyurethane layer can self-assemble at the gas-liquid interface to form a three-dimensional interpenetrating network structure, which improves the impact dispersion performance in the following ways:

[0096] Relieve local stress concentration: The three-dimensional network structure can distribute energy when subjected to stress to avoid stress concentration. Each node and channel in the structure can effectively disperse the impact force to prevent excessive stress concentration in local areas of the glass, which may lead to cracking.

[0097] Multi-level energy dissipation: The three-dimensional interpenetrating network structure has a multi-level energy dissipation effect. When impacted, the external force is first relieved through the honeycomb structure and grid structure of the polyurethane layer, and then further dispersed in the three-dimensional network structure, thereby gradually reducing the intensity of the impact force. The multi-level energy dissipation mechanism enables the polyurethane layer to effectively reduce the transmission of impact force, thereby protecting the glass layer from brittle fracture.

[0098] In summary, the polyurethane layer forms a multi-level impact dispersion and absorption mechanism through the honeycomb pores, magnetic field induced grids, three-dimensional interpenetrating networks and reinforcing materials nanocellulose whiskers and Fe3O4 particles. Through the coordinated work of these mechanisms, the polyurethane layer can effectively absorb and disperse external impact energy, reduce the direct effect of impact on the glass; prevent fragments from flying when the glass breaks, maintain the integrity of the glass; and improve the impact resistance of the glass so that it will not suffer brittle fracture when encountering impact.

[0099] In the present invention, in step S4, a polyurethane layer is placed between a first layer of glass and a second layer of glass, and laminated glass is prepared by vacuum hot pressing;

[0100] In the process of preparing laminated glass by vacuum hot pressing, after the preparation of the polyurethane layer is completed, it serves as the core layer in the laminated glass to provide additional impact resistance, anti-shattering and impact relief functions, and integrates the first layer of glass, the polyurethane layer and the second layer of glass into a three-layer structure. At this time, the polyurethane layer serves as an intermediate layer to completely separate the first layer of glass from the second layer of glass, and the contact surface of the two layers of glass needs to be tightly and evenly covered with the polyurethane layer.

[0101] In a vacuum environment, the three-layer structure of the laminated glass (including the polyurethane layer) will be heated to between 80-120°C. During this process, the polyurethane layer will be heated to a softened state to facilitate better bonding with the glass layer;

[0102] During the heating process, vacuum is required to remove bubbles and impurities in the laminated glass structure to ensure close contact between the layers without gaps. The vacuum environment helps to improve the pressing quality, avoid air residue or bubble formation, and avoid affecting the transparency and resistance of the glass layer.

[0103] When the polyurethane layer reaches a certain softening state, pressure is applied to ensure that the first layer of glass, the polyurethane layer and the second layer of glass are more tightly bonded, thereby avoiding gaps or local poor contact.

[0104] After the vacuum hot pressing is completed, the temperature is gradually lowered to allow the polyurethane layer to harden again, solidify and maintain its structural properties. At this time, the first layer of glass, the polyurethane layer and the second layer of glass have been firmly combined together to form a stable laminated glass.

[0105] During this vacuum hot pressing process, the polyurethane layer is in full contact with the glass surface in a softened state. Through the effects of vacuum and hot pressing, a strong adhesion force can be formed between the polyurethane layer and the glass layer to avoid separation or falling off between the layers. Vacuum hot pressing can also ensure that the contact surface between the polyurethane layer and the two layers of glass is smooth and uniform without bubbles, cracks or unevenness, making the overall structure of the glass stable and greatly improving the impact resistance.

[0106] Among them, the polyurethane layer, as the core layer of the laminated glass, can effectively absorb and disperse external impacts. The vacuum hot pressing ensures the close bonding between the polyurethane layer and the glass layer, which enhances the energy dispersion and absorption capacity of the polyurethane layer when it is impacted, thereby improving the impact resistance of the laminated glass. Due to the energy absorption and dispersion of the polyurethane layer, even if the glass is subjected to severe impact, it can prevent the glass from brittle fracture or fragments from flying.

[0107] In summary, the present invention can effectively prevent glass from bursting by preparing a laminated glass with bidirectional breaking characteristics. When the laminated glass is used on the curtain wall of a high-rise building, the first layer of glass is facing the inside of the high-rise building, and the second layer of glass is facing the outside of the building. Due to the uniform and stable stress distribution formed in the ion exchange of the first layer of glass, the anti-burst performance of the first layer of glass is improved, and the polyurethane layer bonded to the first layer of glass has a high-efficiency impact dispersion performance. After the first layer of glass is directly impacted, the impact force can be further dispersed by the polyurethane layer, thereby ensuring the safety of people in the building. If the first layer of glass is broken by a greater impact force, the glass can be broken locally instead of being broken as a whole due to the adhesion of the polyurethane, thereby ensuring that the glass inside the high-rise building is broken after being impacted. The adhesion of the polyurethane layer can make the glass as a whole still intact, effectively maintaining the adhesion of glass fragments, preventing the fragments from flying, and preventing the fragments from falling from a high altitude from causing harm to people on the bottom.

[0108] When a fire or other dangerous situation occurs in a high-rise building and high-altitude rescue is required, it is necessary to impact the second-layer glass so that the entire laminated glass is shattered and the fragments are dispersed. Therefore, an asymmetric prestress distribution and stress concentration design are introduced in the preparation of the second-layer glass to form a stress gradient structure. When an external impact occurs, the prestress distribution can transfer the external force inward and concentrate it at specific stress concentration points of the glass, inducing a strong local stress concentration effect when the glass breaks. This breaking point will further transfer stress in the direction of the impact, triggering a larger range of glass breakage, effectively enhancing the overall destructive force, driving the entire laminated glass to break and causing the glass fragments to fall off, thus ensuring the smooth opening of the rescue passage. At the same time, the impact direction of the glass fragments is controlled to avoid danger caused by the fragments falling from a high altitude.

[0109] Example 1:

[0110] I. Experimental preparation

[0111] Experimental group 1: Select 100 parts by weight of quartz sand, 20 parts of sodium oxide, 15 parts of calcium oxide, 12 parts of potassium carbonate, and 5.5 parts of aluminum oxide, mix them evenly, and melt them at 1600 °C for 6 h to obtain a liquid glass matrix;

[0112] Pour the liquid glass matrix into a molding die, form a flat glass by gravity spreading, immerse side A of the flat glass in a KNO3 molten salt bath with a mass ratio of 95:3 between KNO3 and NaNO3 at 480 °C for 8 h to form a 70 ± 2 μm deep high-potassium ion concentration gradient, immerse side B of the flat glass in a KNO3 molten salt bath with a mass ratio of 95:3 between KNO3 and NaNO3 at 380 °C for 2.5 h to form an 18 ± 2 μm shallow and uniform potassium ion penetration layer. Place the center of side A of the flat glass after ion exchange at a preset stress concentration point, and cool side A of the flat glass by high-speed nitrogen injection with a wind speed of 30 m / s and a cooling rate of 120 °C / s, and cool side B by natural convection with a cooling rate of 50 °C / s to form an asymmetric stress distribution layer, obtaining a second-layer glass with a thickness of 6 mm.

[0113] Experimental group 2: Select 100 parts by weight of quartz sand, 20 parts of sodium oxide, 15 parts of calcium oxide, 12 parts of potassium carbonate, and 5.5 parts of aluminum oxide, mix them evenly, and melt them at 1600 °C for 6 h to obtain a liquid glass matrix;

[0114] The liquid glass matrix is introduced into a forming mold and flattened by gravity to form flat glass. Both sides A and B of the flat glass are immersed in a KNO3 molten salt bath at 480 °C for 8 h to form a deep high potassium ion concentration gradient of 70 μm ± 2. The A side of the flat glass is cooled by high-speed nitrogen injection with a wind speed of 30 m / s and a cooling rate of 120 °C / s, and the B side is cooled by natural convection with a cooling rate of 50 °C / s to form an asymmetric stress distribution layer, obtaining a second-layer glass with a thickness of 6 mm.

[0115] Experimental group three: 100 parts by weight of quartz sand, 20 parts of sodium oxide, 15 parts of calcium oxide, 12 parts of potassium carbonate, and 5.5 parts of aluminum oxide are mixed evenly and melted at 1600 °C for 6 h to obtain a liquid glass matrix;

[0116] The liquid glass matrix is introduced into a forming mold and flattened by gravity to form flat glass. Both sides A and B of the flat glass are immersed in a KNO3 molten salt bath with a mass ratio of KNO3 to NaNO3 of 95:3 between 380 °C for 2.5 h to form a shallow and uniform potassium ion penetration layer of 18 ± 2 μm. The A side of the flat glass is cooled by high-speed nitrogen injection with a wind speed of 30 m / s and a cooling rate of 120 °C / s, and the B side is cooled by natural convection with a cooling rate of 50 °C / s to form an asymmetric stress distribution layer, obtaining a second-layer glass with a thickness of 6 mm.

[0117] II. Quantitative test of fragment impact force

[0118] 1. Preparation of experimental equipment

[0119] Drop ball impact machine: equipped with a 227 g ± 1 g quenched steel ball (HRC60 - 62);

[0120] Height adjustment range: 0.5 - 6 m (accuracy ± 0.1 cm);

[0121] Ballistic gelatin: 10% concentration (density 1.04 g / cm 3 , simulating human soft tissue);

[0122] Standard aluminum plate: 2024 - T3 aluminum alloy, thickness 2 mm (simulating a rigid surface);

[0123] High-speed camera: Phantom V2512 (1280×800@100,000 fps);

[0124] Dynamic pressure sensor: PCB 113B21 (range 0 - 50 MPa, response time 1 μs);

[0125] Three-dimensional laser velocimeter: Dantec Dynamics BSA P60.

[0126] 2. Performance test steps

[0127] Fix the glass samples (300×300×5 mm) of Experimental Group 1, Experimental Group 2, and Experimental Group 3 in special fixtures respectively, ensuring that the free margin around is ≥15 mm, and spray titanium dioxide speckles (diameter 50 μm, for digital image correlation method DIC analysis) on the sample surface;

[0128] The release height of the steel ball is 4 m, corresponding to an impact energy of 98 J. Locate the geometric center of the sample through the laser crosshair (error < ±1 mm);

[0129] Pour 10% gelatin solution into a 40×40×40 cm mold, cure it at a constant temperature of 25 °C for 24 hours to obtain gelatin with a surface hardness of Bloom 250±5, and embed a pressure sensor array in the gelatin in a grid pattern with a spacing of 50 mm. Attach strain gauges (range ±5000 με, sampling rate 1 MHz) to the aluminum plate surface.

[0130] Test both sides of samples A and B in the above Experimental Group 1, Experimental Group 2, and Experimental Group 3, and obtain experimental data, as shown in Table 1.

[0131] Table 1:

[0132]

[0133] Based on Table 1, it can be concluded that the second-layer glass prepared by the present invention has high impact resistance and high explosion-proof performance. After being impacted and broken on side A, the impact force of the glass fragments generated by the breakage is the largest and concentrated and dispersed towards side B.

[0134] Example 2:

[0135] Polyurethane Interlayer Energy Absorption and Fragment Adhesion

[0136] I. Experimental Preparation

[0137] Experimental Group 4:

[0138] A. Select 100 parts by weight of quartz sand, 20 parts of sodium oxide, 15 parts of calcium oxide, 12 parts of potassium carbonate, and 5.5 parts of aluminum oxide, mix them evenly, and melt them at 1600 °C for 6 h to obtain a liquid glass matrix;

[0139] B. Divide the liquid glass matrix into two parts. Pour one part of the liquid glass matrix into a forming mold, flatten it by gravity to form flat glass, cool it at a rate of 3 °C / min to 350 °C, and immerse it in a KNO3 molten salt bath with a mass ratio of KNO3 to NaNO3 of 95:3 at 450 °C for 8 h for ion exchange, and then cool it to room temperature at a rate of 10 °C / min to obtain the first-layer glass;

[0140] C. Introduce another liquid glass matrix into the forming mold, flatten it by gravity to form flat glass. Immerse side A of the flat glass in a KNO₃ molten salt bath with a mass ratio of KNO₃ to NaNO₃ of 95:3 at 480 °C for 8 h to form a deep potassium ion concentration gradient of 70 ± 2 μm. Immerse side B of the flat glass in a KNO₃ molten salt bath with a mass ratio of KNO₃ to NaNO₃ of 95:3 at 380 °C for 2.5 h to form a shallow and uniform potassium ion permeation layer of 18 ± 2 μm. Place the center of side A of the flat glass after ion exchange at the preset stress concentration point, and cool side A of the flat glass by high-speed nitrogen jet with a wind speed of 30 m / s and a cooling rate of 120 °C / s, while side B is cooled by natural convection with a cooling rate of 50 °C / s to form an asymmetric stress distribution layer, obtaining the second layer of glass with a thickness of 6 mm.

[0141] D. Mix polyether polyol and isocyanate in a mass ratio of 1:1.5, react at 65 °C to generate a polyurethane prepolymer containing dynamic bonds. Add an amphiphilic block copolymer, nanocrystalline cellulose whiskers, and Fe₃O₄ particles to the polyurethane prepolymer, mix at a rotation speed of 2000 rpm for 35 min to obtain a mixed slurry. Inject the mixed slurry into the mold, place it in a uniform magnetic field of 0.8 T, drive the Fe₃O₄ particles to align along the magnetic induction lines, drive the nanocrystalline cellulose whiskers to form a grid-like structure, add azodicarbonamide and raise the temperature to 85 °C to generate honeycomb pores, induce the amphiphilic copolymer to self-assemble at the gas-liquid interface to form a three-dimensional interpenetrating network, forming an impact dispersion layer. Regulate the ultraviolet intensity in different regions, cure at 125 °C for 1.5 h, and anneal for 24 h to obtain a polyurethane layer with a thickness of 0.76 mm.

[0142] E. Using the polyurethane layer as the intermediate layer, attach the first layer of glass and the second layer of glass to both sides of the polyurethane layer respectively in a vacuum environment, and heat to 80 - 120 °C to prepare laminated glass.

[0143] Experimental Group Five: It is roughly the same as Experimental Group Four, except that the intermediate layer uses a 0.76 mm PVB film sourced from Beijing Haiyang Shunda Glass Co., Ltd.

[0144] 2. Test methods:

[0145] Conduct a notched impact test according to ASTM D256 standard to measure the energy absorption density; test the fragment retention rate according to ANSI Z97.1;

[0146] Record the surface morphology of the intermediate film after impact, mark the boundary of the complete area, and calculate the proportion of the remaining area: Retention rate = (Complete area / Total intermediate film area) × 100%;

[0147] Demolish the intermediate film with a standard hook claw or needle-nose pliers, and record the time from applying force to complete tearing; as shown in Table 2.

[0148] Table 2:

[0149]

[0150] In summary, the polyurethane layer prepared by the present invention has efficient impact dispersion performance and adhesiveness. The main reason is that during the preparation process, under the induction of a magnetic field, the Fe3O4 particles are driven to drive the nano-cellulose whiskers to align along the magnetic induction lines, thereby forming a grid-like structure inside the material. When subjected to an impact, the external force can be quickly dispersed, and the impact energy is conducted along the chain-like path between the nano-fibers and the Fe3O4 particles, effectively reducing local stress concentration, thereby enhancing the overall impact dispersion performance. At the same time, by introducing azodicarbonamide blowing agent, micron-sized honeycomb pores are generated during the heating and foaming stage, enabling the amphiphilic block copolymer to self-assemble at the gas-liquid interface to form a three-dimensional interpenetrating network, firmly locking the glass fragments when the glass breaks, endowing the polyurethane layer with strong adhesion ability, and effectively preventing the fragments from falling off;

[0151] Moreover, the laminated glass prepared by the present invention has the characteristic of bidirectional fragmentation and is suitable for high-altitude operations.

[0152] Based on the ideal embodiments of the present invention as an inspiration, through the above description, relevant personnel can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing explosion-proof glass, characterized in that, It includes the following steps: Step S1: Mix silicon dioxide, sodium oxide, calcium oxide, aluminum oxide, and potassium carbonate evenly in proportion, and heat until in a molten state to obtain a liquid glass matrix; Step S2: Divide the liquid glass matrix into two parts, perform a forming process on one part of the liquid glass matrix to obtain the first layer of glass; Step S3: Apply a directional stress to the other part of the liquid glass matrix to form a stress concentration layer to obtain the second layer of glass; Step S4: Synthesize a polyurethane prepolymer from polyether polyol and isocyanate, place it in a uniform magnetic field of 0.5 - 0.8 T, arrange it in the magnetic field directionally, drive Fe3O4 particles to align along the magnetic induction lines, drive nanocrystalline cellulose whiskers to form a grid-like structure, add azodicarbonamide and heat up to 75 - 85 °C to generate honeycomb pores, induce the self-assembly of amphiphilic copolymers at the gas-liquid interface, and regulate the ultraviolet intensity in different regions, cure at 110 - 125 °C for 1.5 - 2 h, and perform a gradient curing process of annealing for 24 h to form a polyurethane layer with a honeycomb-grid interpenetrating structure as an impact dispersion layer, and press the first layer of glass and the second layer of glass with the polyurethane layer to prepare laminated glass; In the said step S3, it includes: Step S31: Introduce the liquid glass matrix into a forming mold and flatten it by gravity to form a flat glass; Step S32: Immerse side A of the flat glass in a KNO3 molten salt bath at 450 °C - 480 °C for 6 - 8 h to form a deep high potassium ion concentration gradient of 65 - 80 μm; Step S33: Immerse side B of the flat glass in a KNO3 molten salt bath with a mass ratio of KNO3 to NaNO3 of 95:3 between 350 °C - 380 °C for 2 - 2.5 h to form a shallow uniform potassium ion penetration layer of 15 - 20 μm; Step S34: Locate the center of side A of the flat glass after ion exchange at a preset stress concentration point; Step S35: Spray and cool side A of the flat glass after completing step S34 with high-speed nitrogen at a wind speed of 25 - 30 m / s and a cooling rate of 100 - 120 °C / s, and cool side B by natural convection at a cooling rate of 40 - 50 °C / s to form an asymmetric stress distribution layer to obtain the second layer of glass.

2. The preparation method of an explosion-proof glass according to claim 1, wherein: In the said step S1, select glass substrate raw materials, which are 100 parts by weight of quartz sand, 15 - 20 parts of sodium oxide, 10 - 15 parts of calcium oxide, 5 - 12 parts of potassium carbonate, and 1.5 - 5.5 parts of aluminum oxide.

3. The preparation method of an explosion-proof glass according to claim 2, characterized in that: In the said step S1, add 0.1 - 0.2 parts of sodium nitrate and 0.5 - 1 part of carbon powder to the glass substrate raw materials and mix evenly, and melt at 1550 - 1600 °C for 4 - 6 h to obtain a liquid glass matrix.

4. The preparation method of an explosion-proof glass according to claim 1, wherein: In the said step S2, the forming process includes the following steps: Step S21: Introduce the liquid glass matrix into a forming mold and flatten it by gravity to form a flat glass; Step S22: Cool the flat glass at a rate of 3 °C / min to 300 °C - 350 °C; Step S23: Immerse the flat glass in a KNO3 molten salt bath at 400 °C - 450 °C for 6 - 8 h for ion exchange; Step S24: Cool the flat glass after ion exchange to room temperature at a rate of 10 °C / min, and ultrasonically clean it with deionized water to remove the surface salt residue, obtaining the first layer of glass.

5. The preparation method of an explosion-proof glass according to claim 4, characterized in that: In the step S23, the KNO3 molten salt composition includes: KNO3 and NaNO3; and the mass ratio between KNO3 and NaNO3 is 95 - 97:3 - 5.

6. The preparation method of an explosion-proof glass according to claim 1, characterized in that: In the step S34, the setting of the stress concentration points includes: etching an array of microholes in the central region on the A side of the flat glass with a femtosecond laser at a wavelength of 1030 nm. Among them, each microhole is a conical structure with a diameter of 45 - 50 μm and a depth of 95 - 100 μm, and is uniformly arranged in a hexagonal symmetric distribution pattern, and the center - to - center distance between adjacent microholes is 480 - 500 μm.

7. The preparation method of an explosion-proof glass according to claim 1, characterized in that: In the step S4, prepare the polyurethane layer, including the following steps: Step S41: Mix polyether polyol and isocyanate in a mass ratio of 1 - 2:1.5 - 4, and react at 50 - 65 °C to generate a polyurethane prepolymer containing dynamic bonds; Step S42: Add an amphiphilic block copolymer, nanocrystalline cellulose whiskers, and Fe3O4 particles to the polyurethane prepolymer, and mix at a rotation speed of 2000 rpm for 30 - 35 min to obtain a mixed slurry; Step S43: Inject the mixed slurry into a mold, place it in a uniform magnetic field of 0.5 - 0.8 T, drive the Fe3O4 particles to align along the magnetic induction lines, and drive the nanocrystalline cellulose whiskers to form a grid - like structure; Step S44: Add azodicarbonamide and heat up to 75 - 85 °C to generate honeycomb pores, induce the amphiphilic copolymer to self - assemble at the gas - liquid interface, and form a three - dimensional interpenetrating network to form an impact - dispersive layer; Step S45: Regulate the ultraviolet intensity in different regions, cure at 110 - 125 °C for 1.5 - 2 h, and anneal for 24 h to obtain the polyurethane layer.

8. The preparation method of an explosion-proof glass according to claim 1, wherein: The thickness of the first layer of glass is 5.8 - 6.2 mm, the thickness of the second layer of glass is 5.8 - 6.2 mm, and the thickness of the polyurethane layer is 0.7 - 1.2 mm.

9. The preparation method of an explosion-proof glass according to claim 1, characterized in that: In the step S4, place the polyurethane layer between the first layer of glass and the second layer of glass, and prepare the laminated glass by means of vacuum hot pressing.

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