Refractory thermal insulation material based on cement-based material as well as preparation method and application of refractory thermal insulation material

Abstract

The invention belongs to the technical field of building thermal insulation materials, and particularly relates to a refractory thermal insulation material based on a cement-based material as well as a preparation method and application thereof. Through synergistic modification of PANF and PVA and combination of a vacuum freeze-drying process, the prepared material has the dry density of less than or equal to 80kg / m < 3 >, the compressive strength of more than or equal to 60MPa and the heat conductivity coefficient of less than or equal to 0.07 W / (m.K) and has excellent fire resistance, and the method is simple in process, easy in raw material obtaining and suitable for the field of building thermal insulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of building thermal insulation materials, and particularly relates to a refractory thermal insulation material based on cementitious materials, a preparation method thereof, and an application thereof. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] In recent years, with the increasing global emphasis on green and low-carbon buildings, the importance of building thermal insulation materials in energy conservation and emission reduction has become increasingly prominent. However, there are still many drawbacks in the currently widely used building thermal insulation materials. For example, although organic thermal insulation materials are lightweight and have good thermal insulation effects, their fire resistance is poor, and they are prone to combustion and release harmful gases; although inorganic thermal insulation materials are fire-resistant, they have a large density and poor mechanical properties, which limits their application in the building field.

[0004] Due to its good fire resistance, mechanical strength, and durability, cementitious materials have become an ideal choice for studying new thermal insulation materials. However, the application of single cementitious materials is limited by problems such as high brittleness and insufficient toughness. In the prior art, fibers are added to enhance toughness, but problems such as poor fiber-matrix bonding and easy carbonization at high temperatures still need to be solved, and fiber selection and dispersion effects still need to be optimized.

[0005] Para-aramid nanofibers (PANF) have high tensile strength, thermal stability, and chemical resistance, but their dispersion in the cement matrix and interface bonding with the matrix still need to be improved. Therefore, finding a suitable fiber to improve the toughness and crack resistance of cementitious materials while enhancing the overall fire resistance of the materials is an urgent problem to be solved. Summary of the Invention

[0006] In view of the needs of the prior art, the object of the present invention is to provide a refractory thermal insulation material based on cementitious materials, a preparation method thereof, and an application thereof. The present invention uses a nano-calcium silicate hydrate-polycarboxylic ether composite material (CSH-PCE) nano-composite material as the cement matrix, introduces para-aramid nanofibers (PANF) and polyvinyl alcohol (PVA) for reinforcement and modification, and combines the vacuum freeze-drying process to simultaneously achieve lightweight, high strength, low thermal conductivity, and excellent fire resistance of the material.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] In the first aspect of the present invention, a refractory thermal insulation material based on a cementitious material is provided. By weight, its raw materials include: 0.1 - 2 parts of para-aramid nanofibers, 4.5 - 5.5 parts of polyvinyl alcohol, and 1 - 20 parts of nano-hydrated calcium silicate-polycarboxylic ether composite material.

[0009] Preferably, for the refractory thermal insulation material based on a cementitious material, by weight, its raw materials include: 0.5 part of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 10 parts of nano-hydrated calcium silicate-polycarboxylic ether composite material.

[0010] Preferably, the length of the para-aramid nanofibers is 1 - 5 μm, the diameter is 10 - 100 nm, and the aspect ratio is 2900 - 3000.

[0011] Preferably, the molecular weight of the polyvinyl alcohol is 1700 - 1800.

[0012] Preferably, the mass ratio of the para-aramid nanofibers, polyvinyl alcohol, and nano-hydrated calcium silicate-polycarboxylic ether composite material is (0.1 - 2):(4.5 - 5.5):(1 - 20).

[0013] In the second aspect of the present invention, a preparation method of the above-mentioned refractory thermal insulation material based on a cementitious material is provided. Specifically: Add the para-aramid nanofibers, polyvinyl alcohol, and nano-hydrated calcium silicate-polycarboxylic ether composite material to deionized water respectively for stirring treatment. Then add the para-aramid nanofiber dispersion liquid after suction filtration and redispersion to the polyvinyl alcohol aqueous solution for stirring. Subsequently, add the aqueous solution of the nano-hydrated calcium silicate-polycarboxylic ether composite material to the obtained mixed solution. The obtained slurry is placed in a mold for low-temperature freezing, and then obtained after vacuum freeze-drying treatment.

[0014] Preferably, the temperature for stirring the para-aramid nanofibers and deionized water is 55 - 65 °C, and the time is 2.5 - 3.5 h to fully disperse the agglomerated para-aramid nanofibers.

[0015] Preferably, the raw material of the polyvinyl alcohol is selected from one of powder and granule.

[0016] Preferably, the temperature for stirring the polyvinyl alcohol and deionized water is 90 - 100 °C, and the time is 50 - 60 min. Intermittent stirring is carried out every 10 - 15 min during this period to prevent agglomeration into blocks.

[0017] Preferably, the temperature for stirring the nano-hydrated calcium silicate-polycarboxylic ether composite material and deionized water is 50 °C, and the time is 50 - 60 min.

[0018] Preferably, the mold is selected from one of a silicone mold and a polytetrafluoroethylene mold.

[0019] Preferably, the low-temperature freezing method is one of refrigerator freezing or liquid nitrogen freezing.

[0020] Preferably, the temperature of the vacuum freeze-drying is -80 to -85 °C, the time is 36 to 78 h, and the vacuum pressure is 0.5 Pa.

[0021] In the sixth aspect of the present invention, there is provided an application of the refractory thermal insulation material based on cement-based material described in the first aspect in building thermal insulation materials.

[0022] The beneficial effects obtained by the above one or more technical solutions of the present invention are as follows:

[0023] (1) In the present invention, para-aramid nanofibers are introduced into the cement-based material, and their uniform dispersion in the cement matrix can form a microporous structure, significantly reducing the dry density of the material by up to 61.57%. The high modulus and fiber network structure of PANF can effectively inhibit the shrinkage deformation of the cement matrix and reduce the generation of microcracks. When the PANF content is 0.5%, the compressive strength reaches 61.93 MPa, an increase of 77.45%, showing high mechanical properties.

[0024] Generally, the dry density of thermal insulation materials is positively correlated with the compressive strength and thermal conductivity. The material prepared in the present invention takes into account the advantages of light weight, heat preservation and high strength at the same time. The interaction between CSH / PCE, PVA and PANF forms a multi-scale reinforcement network, making up for the mechanical shortcoming of low density and avoiding a significant increase in solid-phase heat conduction. The nano-scale pores inhibit gas / solid heat transfer and ensure the continuity of the skeleton to maintain strength, successfully achieving the synergy of low density (78.66 kg / m3), high strength (72.91 MPa) and low thermal conductivity (0.063 W / (m·K)), providing a model for the design of high-performance thermal insulation materials.

[0025] (2) In the present invention, by using the interaction between CSH / PCE, PVA and PANF, a relatively stable structural system is constructed, further hindering heat transfer, thus significantly reducing the thermal conductivity of the material to as low as 0.063 W / (m·K).

[0026] (3) The cement-based thermal insulation and fireproof material prepared in the present invention shows excellent advantages far beyond traditional thermal insulation materials in terms of fire resistance. Its outstanding performance is that it has the characteristics of being difficult to burn, being difficult to be ignited under the action of a fire source; there is no dripping phenomenon during combustion, avoiding the risk of secondary fire caused by dripping; it can withstand high-temperature environments, and its structure is stable at high temperatures and is not prone to deformation and collapse; the overall stability is strong and it can maintain a good fire-resistant state for a long time. Description of the Drawings

[0027] The attached drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0028] Figure 1 Scanning electron microscope images of the thermal insulation materials prepared in Comparative Example 1, Example 3, and Example 5 of the present invention;

[0029] Figure 2 Scanning electron microscope images of the thermal insulation materials prepared in Examples 6-8 of the present invention;

[0030] Figure 3 Scanning electron microscope and EDS images of the vertical cross-section of the thermal insulation material prepared in Example 7 of the present invention;

[0031] Figure 4 Vertical burning test diagrams of the refractory thermal insulation material and the traditional thermal insulation material prepared in Example 7 of the present invention;

[0032] Figure 5 Horizontal burning test diagrams of the refractory thermal insulation material and the traditional thermal insulation material prepared in Example 7 of the present invention. Detailed Description of the Invention

[0033] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0034] It should be noted that the raw materials purchased for the present invention include:

[0035] The nano-hydrated calcium silicate-polycarboxylate ether composite material CSH / PCE was purchased from Jiangsu Bote New Materials Co., Ltd., with a solid content of 10% and a water reduction rate of 28%;

[0036] Para-aramid nanofibers were purchased from Shandong Polyarylene New Materials Co., Ltd., with a diameter between 10-100 nm, a length-to-diameter ratio of 2900-3000, a specific viscosity of 2.0-5.0 dL / g, and a solid content of 3%;

[0037] Polyvinyl alcohol was purchased from Sinopharm Chemical Reagent Co., Ltd., in the form of white or milky white particles with a molecular weight of 1750±50;

[0038] The traditional thermal insulation material involved in the present invention was purchased from Wuhan Nuanxiaowu Thermal Insulation Board Factory in Hubei Province, and it is an EPS foam thermal insulation board made of expandable polystyrene beads with a density of 10 kg / m 3 .

[0039] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0040] In the following embodiments, 0.1 part by mass represents 0.1 g.

[0041] Example 1 : This embodiment provides a refractory thermal insulation material based on cement-based materials and a preparation method

[0042] In this embodiment, the raw materials of the refractory thermal insulation material based on cement-based materials include: 0.1 part of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 1 part of nano-hydrated calcium silicate-polycarboxylic ether composite material.

[0043] The specific preparation method is as follows:

[0044] (1) Pretreat the raw materials. Heat 95 parts by mass of deionized water in a water bath to 95 °C, and slowly add 5 parts by mass of polyvinyl alcohol particles to the deionized water. After sealing and heating with stirring at 95 °C for 1 h, cool to room temperature for later use.

[0045] (2) Add 0.1 part by mass of para-aramid nanofibers (the initial raw material added is 3.33 parts by mass, corresponding to 0.1 g of para-aramid nanofibers) to 200 parts by mass of deionized water, heat in a water bath at 60 °C with stirring for 3 h, and then filter with a circulating vacuum pump until the remaining sample mass is 100 parts by mass (if too much water is filtered out, add deionized water to the aramid dispersion remaining on the filter paper and adjust to a mass of 100 parts by mass, and then mechanically stir for 30 min).

[0046] (3) After mechanically stirring the 100 parts by mass of para-aramid nanofiber dispersion in a water bath at 50 °C for 30 min, add 100 parts by mass of polyvinyl alcohol solution thereto, and mechanically stir again in a water bath at 50 °C for 30 min. Add 1 part by mass of CSH / PCE and mechanically stir in a water bath at 50 °C for 1 h. After stirring is completed, pour the slurry into a mold, shake to remove air bubbles. Subsequently, use a directional freezing device with liquid nitrogen at the bottom to freeze directionally for 30 min, and then place it in a vacuum freeze-drying oven to dry for 48 h to obtain the final thermal insulation and fireproof material.

[0047] Example 2 : This embodiment provides a refractory thermal insulation material based on cement-based materials and a preparation method

[0048] In this embodiment, the specific composition of the refractory thermal insulation material based on cement-based materials is changed, and the other method steps are the same as those in Embodiment 1.

[0049] In this embodiment, the raw materials of the refractory insulation material based on cementitious materials include: 0.3 parts of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 1 part of nano-hydrated calcium silicate-polycarboxylate ether composite material.

[0050] Example 3 This embodiment provides a refractory insulation material based on cementitious materials and a preparation method.

[0051] In this embodiment, the specific composition of the refractory insulation material based on cementitious materials is changed, and the other method steps are the same as those in Embodiment 1.

[0052] In this embodiment, the raw materials of the refractory insulation material based on cementitious materials include: 0.5 parts of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 1 part of nano-hydrated calcium silicate-polycarboxylate ether composite material.

[0053] Example 4 This embodiment provides a refractory insulation material based on cementitious materials and a preparation method.

[0054] In this embodiment, the specific composition of the refractory insulation material based on cementitious materials is changed, and the other method steps are the same as those in Embodiment 1.

[0055] In this embodiment, the raw materials of the refractory insulation material based on cementitious materials include: 1 part of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 1 part of nano-hydrated calcium silicate-polycarboxylate ether composite material.

[0056] Example 5 This embodiment provides a refractory insulation material based on cementitious materials and a preparation method.

[0057] In this embodiment, the specific composition of the refractory insulation material based on cementitious materials is changed, and the other method steps are the same as those in Embodiment 1.

[0058] In this embodiment, the raw materials of the refractory insulation material based on cementitious materials include: 2 parts of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 1 part of nano-hydrated calcium silicate-polycarboxylate ether composite material.

[0059] Example 6 This embodiment provides a refractory insulation material based on cementitious materials and a preparation method.

[0060] In this embodiment, the specific composition of the refractory insulation material based on cementitious materials is changed, and the other method steps are the same as those in Embodiment 1.

[0061] In this embodiment, the raw materials of the refractory insulation material based on cementitious materials include: 0.5 parts of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 5 parts of nano-hydrated calcium silicate-polycarboxylate ether composite material.

[0062] Example 7 : This embodiment provides a refractory insulation material based on a cementitious material and a preparation method thereof.

[0063] In this embodiment, the specific composition of the refractory insulation material based on the cementitious material is changed, and the other method steps are the same as those in Embodiment 1.

[0064] In this embodiment, the raw materials of the refractory insulation material based on the cementitious material include: 0.5 parts of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 10 parts of nano-hydrated calcium silicate-polycarboxylic ether composite material.

[0065] Example 8 : This embodiment provides a refractory insulation material based on a cementitious material and a preparation method thereof.

[0066] In this embodiment, the specific composition of the refractory insulation material based on the cementitious material is changed, and the other method steps are the same as those in Embodiment 1.

[0067] In this embodiment, the raw materials of the refractory insulation material based on the cementitious material include: 0.5 parts of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 20 parts of nano-hydrated calcium silicate-polycarboxylic ether composite material.

[0068] Comparative Example 1 :

[0069] Compared with Embodiments 1 to 5, the difference in this comparative example is that para-aramid nanofibers are not added, and the other method steps are the same as those in Embodiments 1 to 5.

[0070] In this embodiment, the raw materials of the refractory insulation material based on the cementitious material include: 5 parts of polyvinyl alcohol and 1 part of nano-hydrated calcium silicate-polycarboxylic ether composite material.

[0071] Comparative Example 2 :

[0072] Compared with Embodiment 7, the difference in this comparative example is that the nano-hydrated calcium silicate-polycarboxylic ether composite material (CSH-PCE) is not added, and the other component method steps are the same as those in Embodiment 7.

[0073] Comparative Example 3 :

[0074] Compared with Embodiment 7, the difference in this comparative example is that the fiber type is aqueous nanocellulose, and the other components and method steps are the same as those in Embodiment 7.

[0075] Comparative Example 4 : Compared with Embodiment 7, the difference in this comparative example is that the specific composition of the refractory insulation material based on the cementitious material is changed, and the other method steps are the same as those in Embodiment 7.

[0076] In this embodiment, the raw materials of the refractory insulation material based on cement-based materials include: 5 parts of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 10 parts of nano-hydrated calcium silicate-polycarboxylic ether composite material.

[0077] Comparative Example 5 : In this comparative example, compared with Example 7, the difference lies in that the specific components of the refractory insulation material based on cement-based materials are changed, and other method steps are the same as those in Example 7.

[0078] In this embodiment, the raw materials of the refractory insulation material based on cement-based materials include: 0.05 parts of para-aramid nanofibers, 5 parts of polyvinyl alcohol, and 10 parts of nano-hydrated calcium silicate-polycarboxylic ether composite material.

[0079] Test Example 1 : In this test example, the dry density, mechanical properties, and thermal conductivity of the refractory insulation materials prepared in Examples 1-5 and Comparative Example 1 are tested.

[0080] (1) Dry density test:

[0081] Experimental process: Prepare each insulation material into cubic specimens with dimensions of 20mm×20mm×20mm, and dry them in a vacuum freeze-drying oven until the mass is constant. Subsequently, use a high-precision electronic balance to weigh and record the mass data to calculate the dry density of the material.

[0082] The experimental results are shown in Table 1: As the PANF content increases, the dry density of the material shows a significant downward trend. Among them, when PANF is not added, the dry density of the material is the highest, reaching 204.71 kg / m3; when the PANF content increases to 0.5 parts, the dry density drops to 78.66 kg / m3, which is 61.57% lower than the sample without PANF. On this basis, continuing to increase the PANF content, although the dry density still decreases, the decline rate tends to slow down. This result shows that the addition of PANF helps to reduce the bulk density of the material, make the overall structure more porous, and thus effectively reduce the dry density. This characteristic is of great significance for enhancing the lightweight advantage of the material and optimizing the thermal insulation performance.

[0083] (2) Mechanical property test:

[0084] Since the overall strength of the insulation material is relatively low, a high-precision universal testing machine is required for testing. In this test example, GB / T5486 is used to apply a vertical pressure to the specimen until the deformation reaches 10% or rupture, and the maximum load is recorded.

[0085] By selecting an MTS electronic universal testing machine, compressive tests are carried out on different types of insulation materials, and the sample specifications used are 20mm×20mm×20mm (compressive test).

[0086] The experimental results are shown in Table 1: From the compressive strength test results, it can be seen that with the increase of PANF dosage, the compressive strength of the thermal insulation material shows a significant upward trend. When the dosage is 0.1%, the compressive strength of the thermal insulation material is 34.9MPa, and when it increases to 0.5%, the compressive strength of the thermal insulation material increases to 61.93MPa, an increase of 77.45%, which indicates that the increase of PANF can enhance the internal connection of the material and thus improve its compressive performance. When the PANF dosage increases, the compressive strength decreases slightly. Compared with Example 3, the compressive strength of the comparative example decreases.

[0087] (3) Thermal conductivity test:

[0088] This test refers to GB / T 10295. A stable temperature gradient is established on both sides of the sample. The heat flux density is measured by a heat flux sensor, and the thermal conductivity is calculated based on the sample thickness and temperature difference.

[0089] The experimental results are shown in Table 1: When the PANF content is 0.1 parts, the thermal conductivity of the material is relatively high, which is 0.08065W / (m·K). As the PANF content gradually increases to 0.3 parts, the thermal conductivity decreases. When the content is further increased to 0.5 parts, the thermal conductivity drops to 0.074W / (m·K), and the thermal insulation performance is further enhanced. When the content increases to 1 and 2 parts, the thermal conductivity does not continue to decrease, but increases. The results show that increasing the PANF content within a certain range can optimize the microstructure of the thermal insulation material, form a more effective thermal insulation network, and inhibit the conduction of heat. However, when the content exceeds a certain value, it may cause problems such as fiber agglomeration, destroy the uniformity inside the material, thereby increasing the thermal conductivity path, increasing the thermal conductivity, and reducing the thermal insulation performance.

[0090] Based on the performance test of the above-mentioned Experimental Example 1, it is determined that the optimal dosage of the para-aramid nanofibers in Examples 1 to 5 is 0.5 parts.

[0091] Table 1 Performance test of Examples 1 to 5 and Comparative Example 1

[0092]

[0093]

[0094] Test Example 2 :This test case is based on exploring the influence of the addition amount of CSH / PCE on the dry density, mechanical properties and thermal conductivity of refractory insulation materials.

[0095] (1) Dry density test:

[0096] The experimental results are shown in Table 2: With the increase of CSH / PCE content, the dry density of the material shows a trend of gradual increase. When the content of CSH / PCE is 5 parts, the dry density of the material is 81.15kg / m 3 When the content of CSH / PCE is 10 parts, the dry density of the material is 82.05kg / m 3 When the content of CSH / PCE is 20 parts, the dry density of the material is 115.23 kg / m 3

[0097] (2) Mechanical properties test:

[0098] The experimental results are shown in Table 2: With the increase of CSH / PCE dosage, the compressive strength of the material shows a stable increasing trend. When the CSH / PCE dosage is 5 parts, its compressive strength is 62.13MPa, and when the dosage increases to 10 parts, its compressive strength reaches 72.91MPa. When the dosage is further increased to 20 parts, its strength reaches a maximum of 73.71MPa. This is because, on the one hand, CSH / PCE plays a filling role, greatly improving the density of the material, so that its structure can more efficiently transmit and withstand external forces, thereby improving the compressive strength; on the other hand, CSH / PCE forms a strong interface bonding force with PVA and PANF. The interface bonding enables the various components of the material to work together when subjected to force, effectively dispersing stress and avoiding stress concentration leading to premature damage of the material.

[0099] (3) Thermal conductivity test:

[0100] As shown in Table 2, when the CSH / PCE dosage is 1 part, the thermal conductivity of the material is 0.0749W / m·K. As the dosage increases to 5%, the coefficient decreases to 0.0715W / m·K, indicating that the appropriate addition of CSH / PCE helps to reduce the thermal conductivity of the material. When the dosage is further increased to 10 parts, the thermal conductivity drops to the lowest, 0.063W / m·K, and when the dosage is further increased to 20 parts, the thermal conductivity rises to 0.075W / m·K. The test results show that at the low dosage stage, CSH / PCE reduces the flow channel of the air heat conduction medium by filling the internal pores of the material with nano-scale size. At the same time, it forms a relatively stable structure with PVA and PANF, effectively hindering heat transfer and thus reducing the thermal conductivity. When the dosage is further increased, excessive CSH / PCE may agglomerate, destroying the original pore structure and forming a new heat transfer channel, resulting in improved heat transfer efficiency and increased thermal conductivity. Therefore, the dosage of CSH / PCE has a key influence on the thermal conductivity of the insulation material, and there is an optimal dosage that minimizes the thermal conductivity. Therefore, reasonable control of its dosage is crucial to optimize the thermal insulation performance of the insulation material.

[0101] Performance tests of Examples 6 - 8 in Table 2

[0102]

[0103] Based on the performance tests of Test Example 2 above, although the mechanical properties are relatively high when the CSH / PCE dosage in Example 8 is 20 parts, the increase is small, and the thermal conductivity and dry density are high. Therefore, the optimal dosage of CSH / PCE in Examples 6 - 8 is determined to be 10 parts.

[0104] In addition, as Figure 1 shown, Figure 1 Figures a - c in [reference] are the scanning electron microscope images of the thermal insulation materials formed in Comparative Example 1, Example 3, and Example 5 respectively. It can be observed from the figures that the microstructure of the thermal insulation material without PANF (Figure a) shows a loose and irregular state, with large pores and uneven structure distribution. This structure results in a lack of effective support when the material is subjected to external impacts, leading to poor impact resistance. At the same time, the large pores provide more channels for heat transfer, deteriorating the thermal insulation performance.

[0105] When 0.5% PANF is added (Figure b), the microstructure of the material is significantly improved. The uniform dispersion of the fibers forms an intertwined network structure, which can enhance the internal connection degree of the material, enabling it to effectively disperse energy when subjected to impact forces and improving the impact resistance. In addition, the fiber reinforcement effect can withstand greater pressure, significantly enhancing the compressive performance, and this network structure effectively blocks the heat transfer, improving the thermal insulation performance.

[0106] When the PANF dosage gradually increases to 2% (Figure c), agglomeration occurs, which destroys the uniformity of the network structure, reducing the energy dissipation efficiency when the material is subjected to impact. And the agglomerated fibers also cause stress concentration, decreasing the compressive performance. Since the agglomerated fibers also increase the heat conduction channels, the thermal insulation performance decreases.

[0107] As Figure 2As shown, the SEM image can clearly observe that there are a large number of independent pore structures inside the cement-based lightweight thermal insulation flame retardant material prepared in Example 7, and the pore size distribution is relatively uniform and surrounded by a dense skeleton. This microstructure has multiple effects on the various properties of the material: the dense skeleton structure inside the material provides effective support, just like the frame of a building can disperse stress when subjected to external force, avoiding stress concentration and causing rapid destruction of the material; the independent pore structure reduces the convection of air inside the material, enhances the thermal insulation effect, and the large number of distributed pores inhibits the conduction of heat, so that the heat transfer in the material requires a longer and tortuous path; in terms of fire resistance, the microstructure of the material also plays an important role, and the dense skeleton can remain relatively stable in a high temperature environment, not easy to melt or collapse, and provides a certain structural support for the material. At the same time, the internal pore structure can slow down the transfer speed of heat in the material and reduce the material heating rate. This structure is not formed when CSH / PCE is too low or too high.

[0108] like Figure 3 As shown in the figure, Ca and Si elements are evenly distributed in the thermal insulation material, which strongly proves the uniform dispersion state of CSH / PCE in the system; and the distribution of C and N elements fully demonstrates the uniformity of the dispersion of para-aramid nanofibers in the material, which further promotes the mutual cross-linking between the components of the material and strengthens the material structure and performance.

[0109] Based on this, the present invention explores the performance of Example 7 and Comparative Examples 2 to 5, as shown in Table 3 below:

[0110] Table 3 Performance test of Example 7 and Comparative Examples 2 to 5

[0111]

[0112] As shown in the data of Table 3, compared with Example 7, Comparative Example 2 does not incorporate CSH-PCE, and the compressive strength is significantly reduced compared with Example 7. Its absence will lead to an increase in material microstructure defects, weakened interface bonding and decreased stress transfer efficiency, which ultimately manifests as a significant reduction in compressive strength. CSH-PCE can evenly disperse external loads and delay crack propagation. Without CSH-PCE, stress is concentrated in the weak area of the PANF / PVA network, and cracks expand rapidly, leading to brittle fracture.

[0113] Comparative Example 3 replaced the fiber type. Compared with Example 7, the compressive strength was reduced and the thermal conductivity was increased. This was due to the insufficient mechanical properties, weakened interface bonding, poor dispersibility and low thermal stability of the nanocellulose fibers, which led to a decrease in the strength of the material and an increase in the thermal conductivity.

[0114] Too much or too little addition of para-aramid nanofibers in Comparative Examples 4-5 will lead to a decrease in strength if excessive, or a significant increase in the dry density of the material if insufficient.

[0115] Test Example 3 Based on the above Test Example 2, the optimal dosage of CSH / PCE in Example 7 was thus determined. Based on this, the fire resistance performance of this example and traditional thermal insulation materials was explored in this test example.

[0116] As Figure 4 shown, compared with traditional thermal insulation materials (as shown in (b) of Figure 4 ), the cement-based lightweight thermal insulation material prepared by the present invention (as shown in (a) of Figure 4 ) did not show melting and dripping or obvious combustion on the surface after being ignited for 1 minute, 3 minutes, and 5 minutes, only slight carbonization occurred, and the overall structure remained stable, indicating that the material has excellent flame retardancy and fire resistance performance.

[0117] As Figure 5 shown, the horizontal burning test simulates the flame retardant behavior of a horizontally placed building thermal insulation layer or floor material, mainly examining the burning speed and self-extinguishing performance of the material. The test results show that traditional thermal insulation materials (EPS foam thermal insulation board, made of expandable polystyrene beads) exhibit obvious defects. In only 2 seconds, the flame spread to 20 mm (as shown in (b) of Figure 5 ), while for the cement-based lightweight thermal insulation material, the flame reached the same position after 10 minutes, and its flame burning speed was reduced by 300 times compared with traditional thermal insulation materials (as shown in (a) of Figure 5 ).

[0118] In addition, the cement-based lightweight thermal insulation material did not show melting and dripping during the combustion process and has the characteristic of self-extinguishing, with extremely excellent fire resistance performance. While traditional thermal insulation materials, during combustion, the fire spread rapidly within 5 seconds, accompanied by intense combustion and a large amount of black smoke release, and continued to burn even after removing the heat source, fully demonstrating the deficiency of their flame retardant performance.

[0119] From the above test results, it can be seen that the prepared cement-based lightweight thermal insulation material is far superior to traditional thermal insulation materials in terms of fire resistance performance, mainly manifested as being flame retardant, non-melting and dripping, high temperature resistant, and having strong stability. This is mainly because the cement-based material CSH / PCE has a relatively high fire resistance temperature, can maintain a stable structure in a high-temperature environment, and during the combustion process, a dense carbonized layer is formed on the surface of the cement-based material, which can effectively prevent oxygen from entering and reduce the further decomposition of combustibles. In addition, the porous structure inside the material can form a heat insulation barrier under the action of the flame, reducing the heat transfer to the inside, thereby improving the fire resistance performance of the material.

[0120] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A refractory and heat-insulating material based on cementitious materials, characterized in that, By weight parts, its raw materials include: 0.1 - 2 parts of para - aramid nanofibers, 4.5 - 5.5 parts of polyvinyl alcohol, and 1 - 20 parts of nano - hydrated calcium silicate - polycarboxylic ether composite material.

2. The refractory thermal insulation material according to claim 1, characterized in that, By weight parts, its raw materials include: 0.5 part of para - aramid nanofibers, 5 parts of polyvinyl alcohol, and 10 parts of nano - hydrated calcium silicate - polycarboxylic ether composite material.

3. The refractory thermal insulation material according to claim 1, characterized in that, The length of the para - aramid nanofibers is 1 - 5 μm, the diameter is 10 - 100 nm, and the aspect ratio is 2900 - 3000; Preferably, the molecular weight of the polyvinyl alcohol is 1700 - 1800.

4. A method for preparing a refractory and heat-insulating material based on a cementitious material according to any one of claims 1 to 3, characterized in that, Specifically: The para - aramid nanofibers, polyvinyl alcohol, and nano - hydrated calcium silicate - polycarboxylic ether composite material are respectively added to deionized water for stirring treatment. Then, the para - aramid nanofiber dispersion liquid after filtration and redispersion is added to the polyvinyl alcohol aqueous solution for stirring. Subsequently, the aqueous solution of the nano - hydrated calcium silicate - polycarboxylic ether composite material is added to the obtained mixed solution. The obtained slurry is placed in a mold for low - temperature freezing, and then obtained after vacuum freeze - drying treatment.

5. The preparation method according to claim 4, characterized in that, The temperature for the stirring treatment of the para - aramid nanofibers and deionized water is 55 - 65 °C, and the time is 2.5 - 3.5 h to fully disperse the agglomerated para - aramid nanofibers.

6. The preparation method according to claim 4, wherein, The raw material of the polyvinyl alcohol is selected from one of powder and granule; Preferably, the temperature for the stirring treatment of the polyvinyl alcohol and deionized water is 90 - 100 °C, and the time is 50 - 60 min. During this period, intermittent stirring is carried out every 10 - 15 min to prevent agglomeration into blocks.

7. The preparation method according to claim 4, characterized in that, The temperature for the stirring treatment of the nano - hydrated calcium silicate - polycarboxylic ether composite material and deionized water is 50 °C, and the time is 50 - 60 min.

8. The preparation method according to claim 4, characterized in that, The mold is selected from one of a silica gel mold and a polytetrafluoroethylene mold.

9. The preparation method according to claim 4, characterized in that, The low - temperature freezing method is one of refrigerator freezing or liquid nitrogen freezing; Preferably, the temperature of the vacuum freeze - drying is - 80 - 85 °C, the time is 36 - 78 h, and the vacuum pressure is 0.5 Pa.

10. Application of the refractory thermal insulation material based on cement - based material according to any one of claims 1 - 3 in building thermal insulation materials.

Images