Preparation method for preparing heat-insulating SiO2 aerogel plastic through in-situ crosslinking

Abstract

The invention discloses a method for preparing heat-insulating SiO2 aerogel plastic through in-situ crosslinking, and belongs to the field of heat-insulating materials. Organic estersil and a silane coupling agent are used as precursors for preparing SiO2 aerogel, the SiO2 aerogel precursor and a PMMA monomer are co-dissolved in the hydrolytic polycondensation process, and the polymerization rates of the SiO2 aerogel precursor and the PMMA monomer are matched under the condition that the temperature and the catalyst are controlled, so that an interpenetrating double-network structure is formed; according to the structure, the strength of the composite material is greatly improved while low heat conductivity and low density of aerogel are reserved, the problems that a traditional prepared aerogel material is too high in brittleness, prone to powder falling and the like are solved, and meanwhile the composite material has the advantages of high mechanical performance and transparency of plastic due to plastic compounding.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology, and in particular to a method for preparing thermal insulation SiO2 aerogel plastic through in-situ crosslinking. Background Technology

[0002] Driven by the global "dual-carbon" strategy and the upgrading of high-end manufacturing, materials science is rapidly evolving towards "lightweight, high-performance, and multifunctional" applications. Traditional single materials are no longer sufficient to meet the complex requirements of "thermal insulation, mechanical properties, and processability" in fields such as aerospace, new energy vehicles, and building energy conservation. Metals have high density and poor thermal insulation, pure ceramics are brittle and difficult to mold, and ordinary plastics have defects such as high thermal conductivity and insufficient high-temperature stability. Aerogel, as the "lightest solid in the world," possesses an ultra-low thermal conductivity (as low as 0.013 W / (m·K)) due to its nanoporous structure (porosity >90%), but the high brittleness, fragility, and high processing cost of pure aerogel limit its large-scale application. Plastics, on the other hand, have become one of the most widely used polymer materials due to their good mechanical toughness, ease of molding, and cost advantages, but their thermal insulation performance (thermal conductivity typically 0.2-0.5 W / (m·K)) is insufficient to meet the needs of high-end applications. Aerogel plastics formed by combining the two not only retain the ultra-low thermal insulation properties of aerogel, but also solve the mechanical and processing bottlenecks of aerogel by relying on the plastic matrix. At the same time, it expands the functional boundaries of plastics and has important practical significance for promoting energy conservation and emission reduction and upgrading of high-end equipment. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for preparing thermally insulating SiO2 aerogel plastic through in-situ crosslinking. This method features high processability, high toughness, and excellent thermal insulation properties, solving the problems of high brittleness, difficulty in processing, and severe powder shedding associated with traditional aerogel preparation.

[0004] This invention provides a method for preparing thermally insulating SiO2 aerogel plastic through in-situ crosslinking, comprising the following steps: S1: Mix and stir ethanol, organosilicon ester, water, alkylsiloxane and silane coupling agent to obtain a homogeneous mixed solution 1; S2: Add MMA monomer and thermal initiator to the mixed solution 1, stir, then add catalyst, and continue stirring to obtain mixed sol 2; S3: The mixed sol 2 is placed in a heating environment to carry out a polymerization reaction to obtain a composite wet gel block; S4: The composite wet gel block is aged in an ethanol solution and then dried to obtain a composite aerogel plastic.

[0005] Preferably, in step S1, the mass ratio of ethanol, organosilicon ester, and alkylsiloxane is 50:18-30:10-15.

[0006] Preferably, in step S1, the organosilicon ester is one or more of tetraethyl orthosilicate and polyethyl orthosilicate.

[0007] Preferably, in step S1, the alkoxysilane is one or more of polydimethylsiloxane, dimethyldiethoxysilane, and methyltrimethoxysilane.

[0008] Preferably, in step S2, the ratio of MMA monomer to silicone ester is 0.5-2:1.

[0009] Preferably, in step S2, the thermal initiator is selected from one or more of azobisisobutyronitrile (AIBN), azobisisobutyronitrile (VBVN), and benzoyl peroxide (BPO).

[0010] Preferably, in step S4, the volume ratio of ethanol aging solution to wet gel is 0.3-1:1.

[0011] Preferably, in step S2, the catalyst is one or more of an alkaline catalyst and an acidic catalyst.

[0012] Preferably, in step S4, the drying method is supercritical drying.

[0013] Preferably, in step S1, the stirring speed is 200-400 r / min and the stirring time is 5-15 min; in step S2, the stirring time before adding the catalyst is 10-20 min and the stirring time after adding the catalyst is 5-15 min; in step S3, the polymerization reaction temperature is 60℃-120℃; and in step S4, the aging time is 48-96 h.

[0014] Compared with related technologies, the in-situ crosslinking method for preparing thermally insulating SiO2 aerogel plastics provided by this invention has the following advantages: This invention provides a method for preparing thermal insulation SiO2 aerogel plastic through in-situ crosslinking. The method uses in-situ crosslinking to prepare the composite material, which avoids the problems of easy agglomeration of aerogel powder and easy cracking in local areas that occur when traditional aerogel particles are used as fillers. This method achieves uniform dispersion of aerogel in the composite material.

[0015] This invention adds a small amount of alkylsiloxane as a silicon source reaction, which can effectively modify the gel network. At the same time, the introduction of alkyl-modified framework can make the SiO2 aerogel framework have excellent toughness and hydrophobicity, reduce preparation time and cost, and make the alkylsiloxane structure more miscible with organic MMA monomers, avoiding the problem of phase separation before the silane coupling agent has established a structure when miscible.

[0016] This invention incorporates a silane coupling agent, which can build molecular bridges between polar and nonpolar structures, enabling them to form a more stable structure and avoiding the phase separation problem caused by the traditional method of preparing mixtures of different polarities using co-precursors.

[0017] The present invention conducts the reaction in a heated environment. When preparing the co-precursor in situ crosslinking reaction, this environment can ensure that the crosslinking rate of MMA monomer is coordinated with the hydrolysis and condensation rate of silicone ester, thus avoiding the problems of phase separation or uneven polymerization caused by the incoordination of rates in traditional preparation.

[0018] The present invention selects supercritical drying as the drying method. Supercritical drying can minimize the stress generated during drying and avoid the collapse of the skeleton due to phase transformation stress during drying. Attached Figure Description

[0019] Figure 1 The flowchart illustrates the preparation method of the in-situ crosslinking method for preparing thermally insulating SiO2 aerogel plastic provided by this invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments. Example

[0022] like Figure 1 As shown, a method for preparing thermally insulating SiO2 aerogel plastic through in-situ crosslinking includes the following preparation steps: S1: Mix 50 parts ethanol, 10 parts TEOS, 5 parts polyethyl silicate, 6 parts water, 5 parts alkylsiloxane, and 5 parts silane coupling agent at 300 r / min for 10 min to obtain a homogeneous mixed solution 1. S2: Add 15 parts of MMA monomer and 2 parts of thermal initiator to mixed solution 1 and stir for 15 min. Then add catalyst and continue stirring for 10 min to obtain mixed sol 2. S3: Place the mixed sol 2 in an environment of 60℃ to carry out a polymerization reaction to obtain a composite wet gel block.

[0023] S4: The composite wet gel block is aged in an ethanol solution for 72 hours and then dried to obtain the composite aerogel plastic. Example

[0024] A method for preparing thermally insulating SiO2 aerogel plastic through in-situ crosslinking includes the following preparation steps: S1: Mix 50 parts ethanol, 10 parts TEOS, 5 parts polyethyl silicate, 6 parts water, 5 parts alkylsiloxane, and 5 parts silane coupling agent at 300 r / min for 10 min to obtain a homogeneous mixed solution 1. S2: Add 20 parts of MMA monomer and 2 parts of thermal initiator to mixed solution 1 and stir for 15 min. Then add catalyst and continue stirring for 10 min to obtain mixed sol 2. S3: Place the mixed sol 2 in an environment of 120℃ to carry out a polymerization reaction to obtain a composite wet gel block.

[0025] S4: The composite wet gel block is aged in an ethanol solution for 72 hours and then dried to obtain the composite aerogel plastic. Example

[0026] A method for preparing thermally insulating SiO2 aerogel plastic through in-situ crosslinking includes the following preparation steps: S1: Mix 50 parts ethanol, 10 parts TEOS, 5 parts polyethyl silicate, 6 parts water, 5 parts alkylsiloxane, and 8 parts silane coupling agent at 300 r / min for 10 min to obtain a homogeneous mixed solution 1. S2: Add 15 parts of MMA monomer and 7 parts of thermal initiator to mixed solution 1 and stir for 15 min. Then add catalyst and continue stirring for 10 min to obtain mixed sol 2. S3: Place the mixed sol 2 in an environment of 100℃ to carry out a polymerization reaction to obtain a composite wet gel block.

[0027] S4: The composite wet gel block is aged in an ethanol solution for 72 hours and then dried to obtain the composite aerogel plastic.

[0028] Comparative Example 1 A traditional aerogel fiber felt material is presented as a comparison with the method of the present invention.

[0029] The preparation steps are as follows: Prepare commercially available or conventionally prepared silica (SiO2) aerogel fiber felt samples. The samples are physically mixed or simply composite thermal insulation materials. Their inorganic fiber skeleton and organic components do not form a chemically bonded network interpenetrating structure through the in-situ crosslinking process described in this invention.

[0030] Comparative Example 2 A method for preparing aerogel plastics by physical particle mixing is provided as a comparison with the in-situ crosslinking method of the present invention.

[0031] The preparation steps are as follows: S1: Prepare or obtain polymethyl methacrylate (PMMA) plastic particles and silica (SiO2) aerogel particles respectively.

[0032] S2: The PMMA plastic particles and SiO2 aerogel particles are physically and mechanically mixed.

[0033] S3: The mixed particles are prepared into composite block materials by hot pressing or molding.

[0034] The PMMA phase and the SiO2 aerogel phase are only macroscopically physically mixed, and no chemical cross-linking and network interpenetration structure as described in this invention is formed at the interface between the two phases.

[0035] Comparative Example 3 A comparative method for preparing composite materials by in-situ crosslinking, which differs from Example 3 in that it uses a single silicon source.

[0036] The preparation steps are as follows: S1: Mix 50 parts ethanol, 15 parts TEOS, 6 parts water, 5 parts alkylsiloxane, and 8 parts silane coupling agent at 300 r / min for 10 min to obtain a homogeneous mixed solution 1.

[0037] S2: Add 15 parts of MMA monomer and 7 parts of thermal initiator to mixed solution 1 and stir for 15 min. Then add catalyst and continue stirring for 10 min to obtain mixed sol 2.

[0038] S3: Place the mixed sol 2 in an environment of 80℃ to carry out a polymerization reaction to obtain a composite wet gel block.

[0039] S4: The composite wet gel block was aged in an ethanol solution for 72 hours and then dried to obtain the composite material.

[0040] Comparative Example 4 A comparative method for preparing composite materials by in-situ crosslinking, which differs from Example 3 in that it uses a single silicon source, polyethyl silicate.

[0041] The preparation steps are as follows: S1: Mix 50 parts ethanol, 15 parts polyethyl silicate, 6 parts water, 5 parts alkylsiloxane, and 8 parts silane coupling agent at 300 r / min for 10 min to obtain a homogeneous mixed solution 1.

[0042] S2: Add 15 parts of MMA monomer and 7 parts of thermal initiator to mixed solution 1 and stir for 15 min. Then add catalyst and continue stirring for 10 min to obtain mixed sol 2.

[0043] S3: Place the mixed sol 2 in an environment of 70°C to carry out a polymerization reaction to obtain a composite wet gel block.

[0044] S4: The composite wet gel block was aged in an ethanol solution for 72 hours and then dried to obtain the composite material.

[0045] Comparative Example 5 A comparative method for preparing composite materials by in-situ crosslinking, which differs from Example 3 in that no silane coupling agent is added.

[0046] The preparation steps are as follows: S1: Mix 50 parts ethanol, 10 parts TEOS, 5 parts polyethyl silicate, 6 parts water, and 5 parts alkylsiloxane at 300 r / min for 10 min to obtain a homogeneous mixed solution 1.

[0047] S2: Add 15 parts of MMA monomer and 7 parts of thermal initiator to mixed solution 1 and stir for 15 min. Then add catalyst and continue stirring for 10 min to obtain mixed sol 2.

[0048] S3: When the mixed sol 2 was placed in an environment of 80°C for polymerization, it was observed that the solution separated into layers and failed to form a uniform and complete composite wet gel block.

[0049] Comparative Example 6 A comparative method for preparing composite materials by in-situ crosslinking differs from Example 3 in that the polymerization reaction is carried out at room temperature.

[0050] The preparation steps are as follows: S1: Mix 50 parts ethanol, 10 parts TEOS, 5 parts polyethyl silicate, 6 parts water, 5 parts alkylsiloxane, and 8 parts silane coupling agent at 300 r / min for 10 min to obtain a homogeneous mixed solution 1.

[0051] S2: Add 15 parts of MMA monomer and 7 parts of thermal initiator to mixed solution 1 and stir for 15 min. Then add catalyst and continue stirring for 10 min to obtain mixed sol 2.

[0052] S3: The mixed sol 2 was placed in a room temperature (about 25°C) environment for polymerization reaction. The reaction rate was slow, and after a time much longer than in Example 3, a composite wet gel block with poor structural strength was obtained.

[0053] S4: The composite wet gel block was aged in an ethanol solution for 72 hours and then dried to obtain the composite material; According to GB / T10295-2018 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Heat Flow Meter Method" and GB / T8813-2020 "Determination of Compressibility of Rigid Foamed Plastics", the thermal conductivity and compressibility of the composite materials prepared in Examples 1-3 and Comparative Examples 1-6 were tested. The experimental results are shown in Table 1:

[0054] Table 1 The results show that the composite method, the type of silicon source, the addition of silane coupling agent, and temperature conditions have a significant impact on the thermal conductivity and mechanical properties of aerogel plastics. Therefore, using mixed silicone esters and alkyl siloxanes as silicon sources and in-situ crosslinking with MMA monomers can prepare aerogel composite materials with excellent thermal insulation properties. Moreover, the crosslinking of the PMMA skeleton with the SiO2 skeleton also gives it good mechanical properties, improving the problems of severe powder shedding and high brittleness of aerogel materials.

[0055] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., variations in parameter values ​​(e.g., temperature, pressure, etc.), the use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "apparatus plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the invention is not limited to the particular embodiments but extends to a variety of modifications that still fall within the scope of the appended claims.

[0056] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing thermally insulating SiO2 aerogel plastic through in-situ crosslinking, characterized in that, Includes the following steps: S1: Mix and stir ethanol, organosilicon ester, water, alkylsiloxane and silane coupling agent to obtain a homogeneous mixed solution 1; S2: Add MMA monomer and thermal initiator to the mixed solution 1, stir, then add catalyst, and continue stirring to obtain mixed sol 2; S3: The mixed sol 2 is placed in a heating environment to carry out a polymerization reaction to obtain a composite wet gel block; S4: The composite wet gel block is aged in an ethanol solution and then dried to obtain a composite aerogel plastic.

2. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S1, the mass ratio of ethanol, organosilicon ester, and alkylsiloxane is 50:18-30:10-15.

3. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S1, the organosilicon ester is one or more of tetraethyl orthosilicate and polyethyl orthosilicate.

4. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S1, the alkoxysilane is one or more of polydimethylsiloxane, dimethyldiethoxysilane, and methyltrimethoxysilane.

5. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S2, the ratio of MMA monomer to silicone ester is 0.5-2:

1.

6. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S2, the thermal initiator is selected from one or more of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (VBVN), and benzoyl peroxide (BPO).

7. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S4, the volume ratio of ethanol aging solution to wet gel is 0.3-1:

1.

8. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S2, the catalyst is one or more of an alkaline catalyst and an acidic catalyst.

9. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S4, the drying method is supercritical drying.

10. The method for preparing thermally insulating SiO2 aerogel plastic by in-situ crosslinking according to claim 1, characterized in that: In step S1, the stirring speed is 200-400 r / min and the stirring time is 5-15 min; in step S2, the stirring time before adding the catalyst is 10-20 min and the stirring time after adding the catalyst is 5-15 min; in step S3, the polymerization reaction temperature is 60℃-120℃; and in step S4, the aging time is 48-96 h.

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