Silica sand-based breathable composite material and preparation method thereof

Abstract

The invention belongs to the technical field of casting materials, and particularly relates to a breathable composite material based on silica sand and a preparation method thereof.The breathable composite material is prepared from, by weight, 55-72 parts of active silica sand, 80 parts of ZnO suspension liquid, 10-30 parts of AgNO3 solution, 12-20 parts of WBPU and 8-12 parts of breathable modifier, through the synergistic strategy of silica sand particle surface modification, Ag (at) ZnO in-situ loading and WBPU bonding network construction, the casting forming quality and the bearing requirement can be effectively improved, the casting can be converted into a water-permeable potted plant for gardening, a water-permeable channel is coupled with a nutrient slow-release network, healthy growth of plant roots is promoted, and high air permeability, high antibacterial property and excellent mechanical strength are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of casting materials, and particularly relates to a breathable composite material based on silica sand and a preparation method thereof. Background Art

[0002] In the casting industry, silica sand-based composite materials are widely used in the preparation of casting molding sand due to their low cost and high temperature resistance. The traditional coated sand technology usually uses phenolic resin to coat silica sand to improve strength. However, the dense structure formed after resin curing severely limits the gas permeability of the material, resulting in a high porosity defect rate of castings. Although existing technologies have tried to improve gas permeability by adding carbonate blowing agents or introducing porous ceramic particles, such methods often lead to a significant decrease in material strength, and the decomposition products of the blowing agents are likely to contaminate the surface of the castings. Some studies have proposed using gradient pore structure design to balance gas permeability and mechanical properties. However, traditional pore-forming processes are difficult to achieve precise cross-scale regulation of pores. Especially during high-temperature pouring, the pore structure is prone to collapse and failure, unable to meet the strict requirements of precision casting for gas permeability stability. In the field of ecological environmental protection, the design of permeable materials mostly focuses on realizing a single water seepage function, such as using macroporous structures to improve the water permeation rate. However, such materials are prone to performance degradation due to particle blockage or structural damage under complex working conditions. Existing cross-field applications attempt to recycle casting waste sand into products such as permeable bricks. However, the inherently low porosity and surface inertness of unmodified silica sand severely restrict its water permeation efficiency, and post-treatment methods such as mechanical crushing and pore-forming significantly increase production costs. More critically, current gas permeability regulation technologies generally lack environmental responsiveness and cannot dynamically adapt the gas permeability performance according to the requirements of application scenarios, resulting in functional disconnection of materials in multi-scenario applications.

[0003] Therefore, to develop a silica sand-based composite material with pore stability, environmentally adaptive gas permeability regulation ability, and cross-scenario compatibility, it is necessary to fundamentally break through the limitations of traditional gas permeability design that relies on physical mixing and pore-forming, and through the synergistic effect of the intrinsic structure and functional components of the material, realize the intelligent construction and performance maintenance of gas permeation channels, so as to solve the core technical bottleneck that it is difficult to be compatible between precision casting and ecological water permeation functions. Summary of the Invention

[0004] In view of the above situation, the present invention provides a breathable composite material based on silica sand and a preparation method thereof. With active silica sand as the core, a multi-level dynamic pore structure is constructed through gradient etching technology. Mesopores adaptively expand in high-temperature casting scenarios to achieve efficient exhaust and impurity adsorption. The reversible cross-linking of the adhesive system can form a high-strength bonding network at high casting temperatures, and it can also be applied to the field of agricultural or horticultural planting to achieve a breakthrough in cross-field performance.

[0005] To achieve the above object, the technical solutions adopted by the present invention are as follows: The present invention provides a breathable composite material based on silica sand. The breathable composite material comprises the following raw materials in parts by weight: 55-72 parts of activated silica sand, 80 parts of ZnO (zinc oxide) suspension, 10-30 parts of AgNO3 (silver nitrate) solution, 12-20 parts of WBPU (waterborne polyurethane), and 8-12 parts of a breathable regulator.

[0006] Further, the activated silica sand is prepared from the following raw materials in parts by weight: 59-76 parts of silica sand and 1 part of KH-550 (silane coupling agent). The preparation method of the activated silica sand is as follows: Weigh 59-76 parts of silica sand, soak it in purified water and ultrasonically clean for 15 min, dry it, transfer it to a high-speed mixer, weigh 1 part of KH-550 and add it thereto, mix at 800 rpm for 10 min, and let it stand to obtain the activated silica sand.

[0007] Further, the ZnO suspension is prepared from the following raw materials in parts by weight: 1 part of nano-silica, 1-4 parts of ZnO, and 95-98 parts of deionized water. The preparation method of the ZnO suspension is as follows: Weigh 1 part of nano-silica and 1-4 parts of ZnO, add them to 95-98 parts of deionized water, ultrasonically crush and disperse at 500 W for 30 min to prepare the ZnO suspension.

[0008] Further, the silica sand is round silica sand particles for casting, with SiO2 content > 96%, mud content < 0.30%, and particle size range of 0.21-0.42 mm.

[0009] Further, the solid content of the WBPU is 40%.

[0010] Further, the molar concentration of the AgNO3 solution is 0.1 mol / L.

[0011] Further, the breathable regulator is selected from one or more of expanded perlite, biochar, and zeolite powder.

[0012] The present invention also provides a preparation method of a breathable composite material based on silica sand, which specifically comprises the following steps: Step 1: Weigh 10-30 parts of AgNO3 solution and 80 parts of ZnO suspension. Drop the AgNO3 solution into the ZnO suspension while stirring. After dropping, continuously stir at 80 rpm under 365 nm ultraviolet light irradiation for 2 h for reaction. After the reaction is completed, centrifuge at 8000 rpm for 10 min, discard the supernatant, and collect the precipitate to obtain Ag@ZnO. Step 2: Weigh 12-20 parts of WBPU. Wash Ag@ZnO with absolute ethanol and disperse it in WBPU, stir at 50 rpm for 1 h to obtain a bonding phase. Step 3: Weigh 8 - 12 parts of the air permeability regulator and 55 - 72 parts of activated silica sand. After activating the air permeability regulator, mix it with the activated silica sand to obtain a preliminary mixture. Step 4: Transfer the preliminary mixture and the binder phase to a stirrer, stir at 200 rpm for 20 min under vacuum conditions, and pre - press and form under a pressure of 0.5 MPa to obtain a pre - pressed green body. Place the pre - pressed green body in a hot press at 200 °C and 2 MPa for 1 h, and cool to obtain the silica - sand - based air - permeable composite material.

[0013] Further, when the air permeability regulator is expanded perlite, the activation process is to pre - expand the expanded perlite at 400 °C for 10 min.

[0014] Further, when the air permeability regulator is biochar, the activation process is to place the biochar in a tubular furnace, heat it to 600 °C at a rate of 5 °C / min under nitrogen protection, and hold for 2 h.

[0015] Further, when the air permeability regulator is zeolite powder, the activation process is to soak the zeolite powder in 0.1 mol / L hydrochloric acid for 1 h, then wash it to neutrality and dry it.

[0016] The beneficial effects obtained by the present invention are as follows: The silica - sand - based air - permeable composite material provided by the present invention uses amphiphilic silica sand as the core carrier, constructs a multi - level dynamic pore network through gradient etching technology, and breaks through the technical bottleneck of insufficient air permeability of traditional silica sand materials; the mesoporous structure of the silica sand matrix expands adaptively in high - temperature casting scenarios, realizing dual regulation of efficient gas discharge and in - situ slag adsorption. The reversible cross - linked network of WBPU endows the material with dual characteristics of high - strength bonding and environmental degradation after being discarded; the synergistic design of nano - silica and Ag@ZnO not only enhances the self - cleaning ability of the material through photocatalytic effect, but also realizes long - term antibacterial across scenarios by using the silver - zinc synergistic antibacterial mechanism. Combining with the directional adsorption and slow - release function of the air permeability regulator, it forms an integrated solution of stable structure - environment - responsive - function regeneration. The prepared composite material forms a dense air - permeable layer at high temperature, avoiding gas - hole defects in castings; it can also be used as a horticultural water - permeable base material, coupling the water - permeable channel and the nutrient slow - release network to promote the healthy growth of plant roots. The in - situ synthesis of Ag@ZnO by the photoreduction method can effectively avoid the residue of chemical reducing agents, and the recycling of natural raw materials such as silica sand and air permeability regulator significantly reduces the environmental load, providing a new direction for the development of green materials. Description of the Drawings

[0017] Figure 1 It is the morphological characterization result of the air - permeable composite material prepared in Example 5; Figure 2 It is the air - permeability performance investigation result of the air - permeable composite materials prepared in Examples 1 - 5 and Comparative Examples 1 - 2; Figure 3 Compressive strength test results of the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2; Figure 4 Antibacterial property test results of the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2; Figure 5 Porosity test results of the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2; Figure 6 Thermal stability investigation results of the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2. Detailed implementation manners

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying 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 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 shall fall within the protection scope of the present invention.

[0019] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are only for illustrative purposes and do not limit the content of this application.

[0020] In the following embodiments, unless otherwise specified, all are conventional methods; the materials used in the following embodiments, unless otherwise specified, the raw materials are newly purchased materials on the market. Among them, the average particle size of the nano-silica used in the following examples and comparative examples is 34 nm, and the specific surface area is 230 m 2 / g; the specification label of the expanded perlite used is No. 150; the biochar used is straw-derived biochar; the zeolite powder used is of 200-mesh specification.

[0021] Example 1: This example provides a silica sand-based breathable composite material, and the breathable composite material includes the following raw materials in parts by weight: 55 parts of activated silica sand, 80 parts of ZnO suspension, 20 parts of AgNO3 solution, 20 parts of WBPU, and 8 parts of expanded perlite; The activated silica sand is prepared from the following raw materials in parts by weight: 59 parts of silica sand and 1 part of KH-550. The preparation method of the activated silica sand is as follows: Weigh 59 parts of silica sand, soak it in purified water and ultrasonically clean it for 15 min, dry it, transfer it to a high-speed mixer, weigh 1 part of KH-550 and add it thereto, mix at 800 rpm for 10 min, and let it stand to obtain activated silica sand; The ZnO suspension is prepared from the following raw materials by weight: 1 part of nano-silica, 1 part of ZnO, and 98 parts of deionized water. The preparation method of the ZnO suspension is as follows: Weigh 1 part of nano-silica and 1 part of ZnO, add them to 98 parts of deionized water, and disperse them by ultrasonic crushing at 500 W for 30 min to prepare the ZnO suspension.

[0022] This embodiment also provides a preparation method of a breathable composite material based on silica sand, which specifically includes the following steps: Step 1: Weigh 20 parts of AgNO3 solution and 80 parts of ZnO suspension. Drop the AgNO3 solution into the ZnO suspension while stirring. After the dropping is completed, continuously stir at 80 rpm under ultraviolet light irradiation at 365 nm for 2 h for the reaction. After the reaction is completed, centrifuge at 8000 rpm for 10 min, discard the supernatant, and collect the precipitate to obtain Ag@ZnO. Step 2: Weigh 20 parts of WBPU. Wash Ag@ZnO with absolute ethanol and disperse it in WBPU, and stir at 50 rpm for 1 h to obtain the bonding phase. Step 3: Weigh 8 parts of expanded perlite and 55 parts of activated silica sand. Pre-expand and activate the expanded perlite at 400 °C for 10 min, and then mix it with the activated silica sand to obtain the preliminary mixture. Step 4: Transfer the preliminary mixture and the bonding phase to a stirrer, stir at 200 rpm for 20 min under vacuum conditions, and pre-press and form at a pressure of 0.5 MPa to obtain a pre-pressed blank. Place the pre-pressed blank in a hot press at 200 °C and 2 MPa for 1 h, and cool to obtain the breathable composite material based on silica sand.

[0023] Example 2: This embodiment provides a breathable composite material based on silica sand. The breathable composite material includes the following raw materials by weight: 64 parts of activated silica sand, 80 parts of ZnO suspension, 10 parts of AgNO3 solution, 14 parts of WBPU, and 12 parts of expanded perlite. The activated silica sand is prepared from the following raw materials by weight: 68 parts of silica sand and 1 part of KH-550. The preparation method of the activated silica sand is as follows: Weigh 68 parts of silica sand, immerse it in purified water and ultrasonically clean it for 15 min, dry it, transfer it to a high-speed mixer, weigh 1 part of KH-550 and add it thereto, mix at 800 rpm for 10 min, and let it stand to obtain the activated silica sand. The ZnO suspension is prepared from the following raw materials by weight: 1 part of nano-silica, 4 parts of ZnO, and 95 parts of deionized water. The preparation method of the ZnO suspension is as follows: Weigh 1 part of nano-silica and 4 parts of ZnO, add them to 95 parts of deionized water, and disperse them by ultrasonic crushing at 500 W for 30 min to prepare the ZnO suspension.

[0024] This embodiment also provides a method for preparing a breathable composite material based on silica sand, which specifically includes the following steps: Step 1: Weigh 10 parts of AgNO3 solution and 80 parts of ZnO suspension. Drop the AgNO3 solution into the ZnO suspension while stirring. After dropping, continuously stir at 80 rpm under 365 nm ultraviolet light irradiation for 2 h for reaction. After the reaction is completed, centrifuge at 8000 rpm for 10 min, discard the supernatant, and collect the precipitate to obtain Ag@ZnO. Step 2: Weigh 14 parts of WBPU. Wash Ag@ZnO with absolute ethanol and disperse it in WBPU, stir at 50 rpm for 1 h to obtain the bonding phase. Step 3: Weigh 12 parts of expanded perlite and 64 parts of activated silica sand. Pre-expand and activate the expanded perlite at 400 °C for 10 min and then mix it evenly with the activated silica sand to obtain the preliminary mixture. Step 4: Transfer the preliminary mixture and the bonding phase to a stirrer, stir at 200 rpm for 20 min under vacuum conditions, pre-press and form under a pressure of 0.5 MPa to obtain a pre-pressed blank. Place the pre-pressed blank in a hot press and hold it at 200 °C and 2 MPa for 1 h, and cool to obtain the breathable composite material based on silica sand.

[0025] Example 3: This example provides a breathable composite material based on silica sand. The breathable composite material includes the following raw materials in parts by weight: 72 parts of activated silica sand, 80 parts of ZnO suspension, 30 parts of AgNO3 solution, 12 parts of WBPU, and 9 parts of expanded perlite. The activated silica sand is prepared from the following raw materials in parts by weight: 76 parts of silica sand and 1 part of KH-550. The preparation method of the activated silica sand is as follows: Weigh 76 parts of silica sand, immerse it in purified water, ultrasonically clean it for 15 min, dry it, and then transfer it to a high-speed mixer. Weigh 1 part of KH-550 and add it thereto, mix at 800 rpm for 10 min, and let it stand to obtain the activated silica sand. The ZnO suspension is prepared from the following raw materials in parts by weight: 1 part of nano-silica, 2 parts of ZnO, and 97 parts of deionized water. The preparation method of the ZnO suspension is as follows: Weigh 1 part of nano-silica and 2 parts of ZnO, add them to 97 parts of deionized water, disperse them by ultrasonic crushing at 500 W for 30 min, and prepare the ZnO suspension.

[0026] This embodiment also provides a method for preparing a breathable composite material based on silica sand, which specifically includes the following steps: Step 1: Weigh 30 parts of AgNO3 solution and 80 parts of ZnO suspension. Drop the AgNO3 solution into the ZnO suspension while stirring. After dropping, keep stirring at 80 rpm under 365 nm ultraviolet light irradiation for 2 h for reaction. After the reaction is completed, centrifuge at 8000 rpm for 10 min, discard the supernatant, and collect the precipitate to obtain Ag@ZnO; Step 2: Weigh 12 parts of WBPU. Wash Ag@ZnO with absolute ethanol and disperse it in WBPU, stir at 50 rpm for 1 h to obtain the bonding phase; Step 3: Weigh 9 parts of expanded perlite and 72 parts of activated silica sand. Pre-expand and activate the expanded perlite at 400 °C for 10 min, and then mix it with the activated silica sand evenly to obtain the preliminary mixture; Step 4: Transfer the preliminary mixture and the bonding phase to a stirrer, stir at 200 rpm for 20 min under vacuum conditions, and pre-press and form at a pressure of 0.5 MPa to obtain a pre-pressed green body. Place the pre-pressed green body in a hot press at 200 °C and 2 MPa for 1 h, and cool to obtain the silica sand-based breathable composite material.

[0027] Example 4: This example provides a silica sand-based breathable composite material, and the breathable composite material includes the following raw materials in parts by weight: 64 parts of activated silica sand, 80 parts of ZnO suspension, 10 parts of AgNO3 solution, 14 parts of WBPU, 8 parts of expanded perlite, and 4 parts of biochar.

[0028] The activated silica sand is prepared from the following raw materials in parts by weight: 68 parts of silica sand and 1 part of KH-550. The preparation method of the activated silica sand is as follows: Weigh 68 parts of silica sand, immerse it in purified water, ultrasonically clean it for 15 min, dry it, transfer it to a high-speed mixer, weigh 1 part of KH-550 and add it thereto, mix at 800 rpm for 10 min, and let it stand to obtain the activated silica sand; The ZnO suspension is prepared from the following raw materials in parts by weight: 1 part of nano-silica, 4 parts of ZnO, and 95 parts of deionized water. The preparation method of the ZnO suspension is as follows: Weigh 1 part of nano-silica and 4 parts of ZnO, add them to 95 parts of deionized water, disperse by ultrasonic crushing at 500 W for 30 min, and prepare the ZnO suspension.

[0029] This example also provides a preparation method of a silica sand-based breathable composite material, which specifically includes the following steps: Step 1: Weigh 10 parts of AgNO3 solution and 80 parts of ZnO suspension. Drop the AgNO3 solution into the ZnO suspension while stirring. After dropping, keep stirring at 80 rpm under 365 nm ultraviolet light irradiation for 2 h for reaction. After the reaction is completed, centrifuge at 8000 rpm for 10 min, discard the supernatant, and collect the precipitate to obtain Ag@ZnO; Step 2: Weigh 14 parts of WBPU. After washing Ag@ZnO with absolute ethanol, disperse it in WBPU and stir at 50 rpm for 1 h to obtain the bonding phase; Step 3: Weigh 8 parts of expanded perlite, 4 parts of biochar and 72 parts of activated silica sand. Pre-expand and activate the expanded perlite at 400 °C for 10 min. Place the biochar in a tubular furnace and heat it to 600 °C at a rate of 5 °C / min under nitrogen protection and hold for 2 h for activation. Mix it with the activated silica sand to obtain the preliminary mixture; Step 4: Transfer the preliminary mixture and the bonding phase to a stirrer, stir at 200 rpm for 20 min under vacuum conditions, and pre-press and form under a pressure of 0.5 MPa to obtain a pre-pressed green body. Place the pre-pressed green body in a hot press and hold at 200 °C and 2 MPa for 1 h, and cool to obtain the silica sand-based breathable composite material.

[0030] Example 5: This example provides a silica sand-based breathable composite material, and the breathable composite material includes the following raw materials in parts by weight: 64 parts of activated silica sand, 80 parts of ZnO suspension, 10 parts of AgNO3 solution, 14 parts of WBPU, 6 parts of expanded perlite and 6 parts of zeolite powder.

[0031] The activated silica sand is prepared from the following raw materials in parts by weight: 68 parts of silica sand and 1 part of KH-550. The preparation method of the activated silica sand is as follows: Weigh 68 parts of silica sand, immerse it in purified water and ultrasonically clean it for 15 min, dry it, transfer it to a high-speed mixer, weigh 1 part of KH-550 and add it thereto, mix at 800 rpm for 10 min, and let it stand to obtain the activated silica sand; The ZnO suspension is prepared from the following raw materials in parts by weight: 1 part of nano-silica, 4 parts of ZnO and 95 parts of deionized water. The preparation method of the ZnO suspension is as follows: Weigh 1 part of nano-silica and 4 parts of ZnO and add them to 95 parts of deionized water, disperse them by ultrasonic crushing at 500 W for 30 min to prepare the ZnO suspension.

[0032] This example also provides a preparation method of a silica sand-based breathable composite material, which specifically includes the following steps: Step 1: Weigh 10 parts of AgNO3 solution and 80 parts of ZnO suspension. Drop the AgNO3 solution into the ZnO suspension, stir while dropping, and continue to stir at 80 rpm under 365 nm ultraviolet light irradiation for 2 h for reaction. After the reaction is completed, centrifuge at 8000 rpm for 10 min, discard the supernatant and collect the precipitate to obtain Ag@ZnO; Step 2: Weigh 14 parts of WBPU. After washing Ag@ZnO with absolute ethanol, disperse it in WBPU and stir at 50 rpm for 1 h to obtain the bonding phase; Step 3: Weigh 6 parts of expanded perlite, 6 parts of zeolite powder, and 72 parts of activated silica sand. Pre-expand the expanded perlite at 400 °C for 10 min for activation, soak the zeolite powder in 0.1 mol / L hydrochloric acid for 1 h, then wash it to neutrality and dry it for activation. Mix them evenly with the activated silica sand to obtain a preliminary mixture. Step 4: Transfer the preliminary mixture and the binder phase to a stirrer, stir at 200 rpm for 20 min under vacuum conditions, and pre-press and form under a pressure of 0.5 MPa to obtain a pre-pressed green body. Place the pre-pressed green body in a hot press and hold it at 200 °C and 2 MPa for 1 h, and then cool it to obtain the silica sand-based breathable composite material.

[0033] The difference between Comparative Example 1 and Example 5 is that KH-550 was not added, and the rest was the same as in Example 5.

[0034] The difference between Comparative Example 2 and Example 5 is that an equal mass of purified water was used instead of WBPU for preparation, and the rest was the same as in Example 5.

[0035] Morphology characterization Take the breathable composite material prepared in Example 5 on a copper mesh, gold-plate it, and use a scanning electron microscope (SEM) to observe its microstructure. The results are shown in Figure 1 .

[0036] Air permeability investigation According to the air permeability measurement method in GB / T 2684-2009 "Test Methods for Foundry Sands and Mixtures", using an air permeability tester (model SAC-01), take the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2. Make the specimens into standard cylinders with a diameter of Φ50×50 mm, place them in the test chamber, adjust the air pressure to 0.1 MPa, record the gas volume passing through the specimens per unit time, and record the air permeability rate (GPU). The results are shown in Figure 2 .

[0037] Compressive strength investigation Take the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2, use a universal material testing machine (Instron5967), the specimen size is Φ25×50 mm, the loading rate is 1 mm / min, record the maximum load when the specimen fails, and calculate the compressive strength. The results are shown in Figure 3 .

[0038] Antibacterial property investigation Using the inhibition zone method, inoculate Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 6538) on an agar plate. Place the specimens (10×10 mm) of the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2 on the surface of the bacterial solution. After culturing at 37 °C for 24 hours, measure the diameter of the inhibition zone and calculate the inhibition rate. The results are shown in Figure 4。

[0039] Porosity Investigation Take the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2, adopt the mercury intrusion method, with a test pressure of 0.1-400 MPa, record the relationship between the volume of mercury injected and the pressure, and calculate the total porosity (%), and the results are shown in Figure 5 。

[0040] Thermal Stability Investigation Take the breathable composite materials prepared in Examples 1-5 and Comparative Examples 1-2, use a thermogravimetric analyzer (TGA 5500), with a heating rate of 10 °C / min under a nitrogen atmosphere, and test the mass loss curve at 300 °C. The results are shown in Figure 6 。

[0041] Figure 1 SEM results show that the surface of the particles of the breathable composite material prepared in Example 5 is rough and there are many pores.

[0042] Figure 2 The air permeability results show that the breathable composite material prepared in Example 5 has better air permeability performance, and the compounding effect of expanded perlite and zeolite powder is better.

[0043] Figure 3 The compressive strength results show that the breathable composite materials prepared in Examples 1-5 have higher compressive strength. In Comparative Example 1, due to the absence of KH-550, the interfacial bonding is weakened and the strength is significantly reduced.

[0044] Figure 4 The antibacterial rate results show that the efficient photocatalysis of Ag@ZnO and the Ag + slow release in the breathable composite materials prepared in Examples 1-5 result in better antibacterial performance.

[0045] Figure 5 The porosity results show that due to the synergy of the micropores of zeolite powder and the mesopores of expanded perlite, the total porosity of the breathable composite materials prepared in Examples 1-5 reaches 42%. In Comparative Example 1, due to the lack of coupling treatment, the pores at the silica sand-binder interface are closed, and the porosity is only 28%.

[0046] Figure 6 The thermogravimetric results show that the breathable composite material prepared in Comparative Example 2 has a large mass loss, mainly due to the lack of heat resistance synergy between WBPU and nano-silica.

[0047] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

[0048] The above description of the present invention and its embodiments is not restrictive. What is shown in the accompanying drawings is only one of the embodiments of the present invention, and the actual application is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and design similar methods and embodiments to this technical solution without departing from the gist of the present invention and without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A breathable composite material based on silica sand, characterized in that: The breathable composite material comprises the following raw materials in parts by weight: 55-72 parts of active silica sand, 80 parts of ZnO suspension, 10-30 parts of AgNO3 solution, 12-20 parts of WBPU and 8-12 parts of breathability regulator; The active silica sand is prepared from the following raw materials in parts by weight: 59-76 parts of silica sand and 1 part of KH-550. The preparation method of the active silica sand is as follows: weigh silica sand, wash it, dry it, and mix it with KH-550 to obtain active silica sand; The ZnO suspension is prepared from the following raw materials in parts by weight: 1 part of nano-silicon dioxide, 1-4 parts of ZnO and 95-98 parts of deionized water. The preparation method of the ZnO suspension is as follows: weigh nano-silicon dioxide and ZnO, add them into deionized water, and ultrasonically disperse them to obtain the ZnO suspension.

2. A breathable composite material based on silica sand according to claim 1, characterized in that: The silica sand is round silica sand particles for casting; The air permeability regulator is selected from one or more of expanded perlite, biochar and zeolite powder.

3. A method for preparing a breathable composite material based on silica sand according to any one of claims 1-2, characterized in that: The specific steps include: Step 1: Weigh the ZnO suspension, then weigh the AgNO3 solution and add it dropwise to the ZnO suspension, irradiate with light, centrifuge, and collect the precipitate, i.e., Ag@ZnO; Step 2: Weigh WBPU and disperse Ag@ZnO in WBPU to obtain a bonding phase; Step 3: Weigh the air permeability regulator to activate it, and then weigh the activated silica sand and add it to mix well to obtain a primary mixture; Step 4: The primary mixture and the binder phase are pre-pressed and hot-pressed to obtain a breathable composite material based on silica sand.

4. The method for preparing a breathable composite material based on silica sand according to claim 3, characterized in that: In step 1, the illumination process uses 365 nm ultraviolet light irradiation; In step 4, the pre-pressing process pressure is 0.5 MPa, and the hot pressing process is hot pressing at 200° C. and 2 MPa for 1 h.

5. The method for preparing a breathable composite material based on silica sand according to claim 3, characterized in that: When the air permeability regulator is expanded perlite, the activation process in step 4 is to pre-expand the expanded perlite at 400° C. for 10 min.

6. The method for preparing a breathable composite material based on silica sand according to claim 3, characterized in that: When the permeability regulator is biochar, the activation process in step 4 is to place the biochar in a tubular furnace, raise the temperature to 600° C. and keep it for 2 h under nitrogen protection.

7. The method for preparing a breathable composite material based on silica sand according to claim 3, characterized in that: When the air permeability regulator is zeolite powder, the activation process in step 4 is to soak the zeolite powder in hydrochloric acid, wash it to neutrality and dry it.

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