Silica aerogel / glass fiber thermal insulation composite board and preparation method thereof

Abstract

This invention belongs to the field of thermal insulation materials and discloses a silica aerogel / glass fiber thermal insulation composite board and its preparation method. This invention uses tetraethyl orthosilicate (TEOS) and water glass as a common silicon source to prepare SiO₂. 2 Aerogels, while reducing production costs, ensure the quality of the prepared glass fiber reinforced SiO2. 2 Aerogel composite panels exhibit low density and low heat transfer coefficient, while also possessing certain mechanical properties. Furthermore, this method has a simple preparation process and can meet the requirements for the production and processing of large-size composite panels, demonstrating promising application prospects for large-scale industrial production.

Description

A silica aerogel / glass fiber thermal insulation composite board and its preparation method Technical Field

[0001] This invention belongs to the field of thermal insulation materials, and relates to a silica aerogel / glass fiber thermal insulation composite board and its preparation method. Background Technology

[0002] SiO2 aerogel, with its fine skeletal particles and nanoscale pores, effectively suppresses both solid-state and gaseous heat conduction, making it a lightweight super-insulating material. However, SiO2 aerogel suffers from poor mechanical properties and is mostly found in powder or small bulk forms, limiting its applications. In recent years, to improve the mechanical properties of SiO2 aerogel, glass fiber has been combined with it. This not only allows for the fabrication of large-size panels that meet application requirements but also enhances the mechanical properties of the aerogel material without compromising its thermal insulation performance, thus achieving a perfect combination of reinforcement, toughening, and insulation.

[0003] Currently, the silicon sources for preparing SiO2 aerogels are mainly divided into two categories. One is inexpensive water glass, which, although inexpensive (about 2-4 yuan / kg), produces aerogel samples with high density. The other is tetraethyl orthosilicate (TEOS) (about 10-35 yuan / kg), which has the advantage of not being affected by other impurities during the preparation process and being able to produce aerogels with a good degree of cross-linking. However, TEOS has the disadvantage of being toxic and expensive. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, further reduce the cost of glass fiber reinforced SiO2 aerogel composite boards, and ensure lightweight application requirements under special conditions, this invention provides a silica aerogel / glass fiber thermal insulation composite board and its preparation method. This method uses water glass / TEOS as a common silicon source to prepare aerogel. The resulting composite board has low thermal conductivity, low density, and low cost. Moreover, the preparation process is simple, which has positive significance for large-scale industrial production.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing a silica aerogel / glass fiber thermal insulation composite board includes the following steps:

[0007] (1) Add TEOS, deionized water, and ethanol (ETOH) to a beaker in a specific molar ratio and stir until homogeneous. Then, add 1 mL of acidic solution (0.1 mol·L⁻¹) dropwise. -1The mixed solution is sealed and placed in a water bath at 35-45℃ and heated while being magnetically stirred for 20-40 minutes to hydrolyze it, to obtain TEOS hydrolysate, wherein the molar ratio of TEOS, deionized water and ETOH is 1:(4-10):(4-8).

[0008] (2) Dilute the water glass with deionized water at a certain volume ratio, wherein the dilution ratio is 1:1 to 1:10. Add the diluted water glass aqueous solution to the exchange column containing the acidified exchange resin and take the sol with a pH between 1 and 3.

[0009] (3) After mixing and stirring the TEOS hydrolysate prepared in step (1) and the water glass hydrolysate prepared in step (2) evenly, add ammonia water to adjust the pH to 6-6.5. Control the gelation time by adjusting the amount of ammonia water added. After the ammonia water is added, stir the sol evenly, add the pretreated glass fiber mat, press out the air bubbles in the material, make the mat completely wet, seal the mold, put it in a water bath at 30-80℃, and let it stand for gelation.

[0010] (4) After complete gelation, add 50 vol% ethanol aqueous solution to the stainless steel mold containing the wet gel, enough to cover the gel, cover the surface with a thin film and age for 18-24 hours.

[0011] (5) The wet gel was hydrophobically modified in a water bath at 30-80℃ using trichloromethylsilane (TMCS), ETOH, and n-hexane, with the volume fraction ratio of the three solvents being (3-5):2:(13-15). When the wet gel was suspended in the modification solution, the modification was complete. The modifier and other reactants on the surface of the modified wet gel were washed away with n-hexane and placed in a blower box to dry at 60-120℃ for 6-12 hours.

[0012] In preferred step (1), the acid is either HCl or oxalic acid.

[0013] In step (2), the acidified cation exchange resin is a strong acid type cation exchange resin (732 strong acid type Na). + The preparation process is as follows: Wash the resin with distilled water, weigh 300-400g of resin, add 20mL of concentrated hydrochloric acid and 300mL of distilled water and stir, then wash with distilled water until neutral and pack into a column for later use.

[0014] In step (3), the molar ratio of the TEOS hydrolysate to the water glass hydrolysate is 1:(0.2-5);

[0015] In step (3), the mass ratio of the aerogel to the glass fiber is 1:(0.5~1.5);

[0016] In step (3), the glass fiber pretreatment scheme is to wash the glass fiber mat with ethanol and deionized water in sequence, dry it at 120°C for 12 hours, and then put it into a fiber carding machine for fluffing treatment.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] Compared to traditional silica aerogel / glass fiber thermal insulation composite panels, the preparation process of this invention is simpler and can meet the needs of large-size composite panels. The prepared composite panels have lower costs while also possessing a low density of 0.12-0.23 g / cm³. 3 It has the advantages of low thermal conductivity (0.02-0.04 W / m·K). Attached Figure Description

[0019] Figure 1 is a morphological diagram of the composite material of the present invention;

[0020] Figure 2 is a scanning electron microscope image of the composite material of the present invention at 100 μm;

[0021] Figure 3 is a scanning electron microscope image of the composite material of the present invention at a depth of 30 μm. Detailed Implementation

[0022] To better understand the content of this invention, specific implementation examples will be used to further illustrate the invention below. The following embodiments are based on the technology of this invention and include detailed implementation methods and operating steps; however, the scope of protection of this invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods used in this invention are all conventional methods, and the experimental equipment, materials, reagents, etc., used are all commercially available.

[0023] Example 1

[0024] 1. Add TEOS, deionized water, and ethanol (ETOH) to a beaker in a molar ratio of 1:10:5 and stir well. Then, add 1 mL of oxalic acid solution (0.1 mol·L⁻¹) dropwise. -1 The mixed solution was sealed and placed in a water bath at 40°C for heating while being magnetically stirred for 30 minutes to hydrolyze it, thus obtaining TEOS hydrolysate.

[0025] 2. Add 732 strong acid type Na + The ion exchange resin was washed with distilled water. 300g of resin was weighed, added to 20mL of concentrated hydrochloric acid and 300mL of distilled water, and stirred. The mixture was then washed with distilled water until neutral and packed into a column for later use. Water glass and deionized water were diluted at a volume ratio of 1:4 and stirred until homogeneous; this mixture was labeled as mixture A. 100mL of this mixture was slowly added to mixture A with high-speed stirring to obtain a clear and transparent hydrolysate. The prepared hydrolysate was added to the acidified ion exchange resin, and a sol with a pH of 2 was prepared.

[0026] 3. Mix TEOS hydrolysate and water glass hydrolysate in a 1:1 molar ratio. Add desiccant to the mixture in a 1:1 molar ratio. Stir well and then add 50 vol% ammonia water to adjust the pH to 7. Before gel formation, add pretreated glass fiber needle-punched felt in a 1:1 mass ratio with the gel. Press out the air bubbles in the material to ensure the felt is completely saturated.

[0027] 4. Seal the mold and place it in a 45℃ water bath to allow it to gel. After gelation, add a 50 vol% ethanol aqueous solution to the stainless steel mold containing the wet gel, ensuring the gel is completely submerged. Cover the surface with a thin film and age it in a 45℃ water bath for 24 hours.

[0028] 5. After 24 hours, the wet gel was placed in a 45°C water bath and hydrophobically modified with a TMCS, ethanol and n-hexane solution with a volume ratio of 2.5:2:5.5. When the wet gel was suspended in the modification solution, the modification was complete. The gel was then repeatedly rinsed with n-hexane and placed in a blower to dry at 70°C for 12 hours.

[0029] 6. Density testing showed that the density of the composite board, using TEOS / water glass as the co-precursor SiO2 aerogel and reinforced with glass fiber, was 0.1883 g / cm³. 3 The sample measures 30 × 30 cm (Figure 1). Scanning electron microscopy (Figure 2) reveals that the glass fibers are randomly distributed in three-dimensional space, with uneven fiber diameter distribution. The internal nanofibers are loosely arranged, exhibiting a fluffy network structure, with significant large-area aggregation and several interlacing glass fibers. The glass fibers form a linear, interwoven network structure, with the largest fiber diameter reaching 200 nm. Bending of the fibers is observed in the figure, demonstrating good toughness. Some aerogel adheres to the fibers. The thermal conductivity at room temperature, measured using the transient planar heat source method, is 0.031 / m·K, and the compressive strength is 0.91 MPa.

[0030] Calculations show that, compared to SiO2 aerogel prepared using water glass as the silicon source, the density of the composite board prepared by this method is reduced by approximately 33% under the premise that the mass ratio of aerogel to glass fiber is 1:1. Compared to SiO2 aerogel composites prepared using TEOS as the silicon source, the cost of the composite board prepared by this method is reduced by 38-48%. The basic parameters selected in the calculation process are shown in Table 1.

[0031] Table 1 Density Calculation

[0032]

[0033] Table 2 Price Calculation

[0034]

[0035] Note: When the molar ratio is 1:1, the mass ratio of TEOS / water glass as co-precursor SiO2 aerogel is 1:1.36. Based on the production cost of 7-14 yuan per kg of water glass SiO2 aerogel, the production cost of the aerogel of this invention is 19-59 yuan per kg of SiO2.

[0036] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a silica aerogel / glass fiber thermal insulation composite board, characterized in that: The steps include: (1) Add TEOS, deionized water, and ethanol ETOH to a beaker in a certain molar ratio and stir well, then add 1 mL of 0.1 mol∙L⁻¹ dropwise. -1 The acidic solution was sealed and placed in a water bath at 35-45°C and heated while being magnetically stirred for 20-40 min to hydrolyze it, to obtain TEOS hydrolysate, wherein the molar ratio of TEOS, deionized water and ETOH was 1:(4-10):(4-8); (2) The water glass was diluted with deionized water at a certain volume ratio, wherein the volume ratio of water glass to deionized water was 1:1 to 1:10, and the diluted mixture was added to the exchange column containing the acidified exchange resin, and the sol with a pH between 1 and 3 was taken; (3) The TEOS hydrolysate and the water glass hydrolysate were mixed and stirred evenly, and then added The pH value was adjusted to 7 with ammonia water. The gelation time was controlled by adjusting the amount of ammonia water added. After the ammonia water was added, the sol was stirred evenly, and the pretreated glass fiber mat was added. Air bubbles in the material were pressed out to ensure the mat was completely saturated. The mold was sealed and placed in a water bath at 30-80℃ for standing to allow gelation. The molar ratio of TEOS hydrolysate to water glass hydrolysate was 1:1, and the mass ratio of gel to glass fiber mat was 1:

1. The pretreatment method involved reflux washing with ethanol and deionized water sequentially, followed by drying at 120℃ for 12 hours. h, and then put it into a fiber carding machine for fluffing treatment; (4) After the gel is completely gelled, add 50 vol% ethanol aqueous solution to a stainless steel mold containing wet gel, enough to cover the gel, cover the surface with a film and age for 18~24h; (5) In a water bath at 30~80℃, the wet gel is hydrophobically modified with chlorotrimethylsilane TMCS, ETOH and n-hexane. The volume ratio of TMCS, ethanol and n-hexane solution is 2.5:2:5.

5. When the wet gel is suspended in the modification solution, the modification is completed. Use n-hexane to wash away the modifier and other reactants on the surface of the modified wet gel, place it in a blower box and dry at 60~120℃ for 6~12h.

2. The method for preparing the silica aerogel / glass fiber thermal insulation composite board according to claim 1, characterized in that: In step (1), the acid is either HCl or oxalic acid.

3. The method for preparing the silica aerogel / glass fiber thermal insulation composite board according to claim 1, characterized in that: In step (2), the acidified cation exchange resin is a strong acid type cation exchange resin 732, a strong acid type Na. + Wash the resin with distilled water, weigh 300-400g of resin, add 20 mL of concentrated hydrochloric acid and 300 mL of distilled water and stir. Wash with distilled water until neutral and then pack into a column for later use.

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