Multifunctional polyurethane foam for building materials and process for its preparation

Abstract

The present application relates to the technical field of building materials, and particularly relates to a multifunctional polyurethane foaming material for building materials and a preparation process thereof. The foaming material is prepared by components A and B in a specific ratio. The core is to perform double functional silane modification on hollow glass microbeads, introduce reactive epoxy groups and hydrophobic alkyl groups, and combine with alumina nanoparticles with epoxy groups on the surface, so as to significantly improve the interface compatibility and chemical combination of the filler and the bubble wall, avoid stress concentration and micro void generation. At the same time, the interface stress can be relieved, and the dimensional stability and thermal performance can be improved. The material has low density, high strength, excellent thermal insulation, good dimensional stability and flame retardant performance, and is suitable for multifunctional requirements such as building thermal insulation, and is superior to the traditional system.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a multifunctional polyurethane foam material for building materials and its preparation process. Background Technology

[0002] Polyurethane foam, a type of high-molecular polymer foam, is widely used in the construction industry for thermal insulation panels, wall filling, and roof waterproofing due to its unique closed-cell structure and excellent thermal insulation properties. This material is typically produced from raw materials such as polyether polyols and isocyanates through a chemical foaming reaction. By controlling the ratio of foaming agents, catalysts, and stabilizers, a low-density, high-strength foam structure can be formed. In recent years, with the continuous improvement of building energy efficiency standards, the performance requirements for polyurethane foam materials have become increasingly stringent. They not only need to possess good thermal insulation properties but also need to consider mechanical strength, dimensional stability, and flame retardant characteristics to adapt to complex operating environments, such as long-term durability under high temperature, humidity, or mechanical load conditions.

[0003] In the preparation of traditional polyurethane foam materials, lightweight fillers, such as hollow glass microspheres, are often introduced to reduce density and improve thermal insulation. These fillers have low density and thermal barrier properties, effectively reducing the solid heat conduction path and thus improving the overall thermal conductivity of the material. However, the introduction of fillers often brings interfacial compatibility problems. Because the surface of hollow glass microspheres has an inorganic silicate structure, it has low affinity with the organic polyurethane matrix, which easily leads to uneven dispersion of the filler in the foam matrix, resulting in micro-agglomerates or voids. These defects not only weaken the continuity of the foam wall but may also induce stress concentration points, accelerating crack propagation under external forces and causing an overall decline in the mechanical properties of the material. At the same time, interfacial weakening can also increase the thermal bridging effect, causing the thermal conductivity to increase instead of decrease, which defeats the purpose of introducing fillers.

[0004] On the other hand, the flame retardant properties of polyurethane foam are also a key consideration in building applications. Traditional materials often rely on adding flame retardants to inhibit the spread of combustion, but these additives may interfere with the foaming reaction, leading to uneven foam structure or reduced mechanical properties. Especially after the introduction of lightweight fillers, the weaknesses at the filler / foam wall interface become potential channels for flame propagation, easily causing uneven local charring and accelerated heat release, thereby increasing the combustion rate.

[0005] Furthermore, in practical applications of building materials, polyurethane foam faces multiple environmental challenges, such as expansion and contraction caused by humidity changes or deformation due to external impacts. These factors further highlight the harm of interface weakening: weak interfaces not only reduce load-bearing efficiency but may also promote moisture penetration and accelerate material aging. Although existing literature reports on improving performance through multi-component composites, these are often limited to optimizing a single performance aspect and cannot achieve synergistic improvements in thermal, mechanical, and flame-retardant properties. Especially when pursuing low density, increasing the proportion of lightweight fillers can amplify interface defects, causing inherent contradictions between performance indicators. For example, while lower density should improve thermal insulation, increased interfacial porosity can actually enhance convective heat conduction, creating an irreconcilable conflict.

[0006] In summary, when introducing lightweight fillers to achieve low density and high thermal insulation in existing polyurethane foam materials, the weakening of the interface between the foam wall and the filler has become a core bottleneck restricting performance improvement. This problem not only leads to a decrease in mechanical strength but also causes a contradiction of increased thermal conductivity, urgently requiring innovative interface control strategies to address in order to meet the pressing needs of the construction industry for multifunctional materials. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a multifunctional polyurethane foam material for building materials and its preparation process, so as to solve the problem that when lightweight fillers are introduced into existing polyurethane foam materials, the weakening of the foam wall and filler interface leads to a decrease in mechanical strength and an increase in thermal conductivity.

[0008] To achieve the above objectives, the present invention provides a multifunctional polyurethane foam material for building materials, which is prepared by mixing component A and component B in a weight ratio of 1000-1200:380.

[0009] Component A is prepared from the following raw materials in parts by weight: 450-550 parts of polyether triol A, 350-450 parts of polyether triol B, 205-325 parts of flexible buffer layer additive, 13-17 parts of deionized water, 8-12 parts of organosilicon surfactant, 0.8-1.2 parts of dibutyltin dilaurate, 2-4 parts of ethylenediamine, 2-4 parts of diethylenetriamine, and 1.5-2.5 parts of m-phenylenediamine.

[0010] Component B is polymethylene polyphenyl isocyanate.

[0011] Preferably, the weight-average molecular weight of the polyether triol A is 2000.

[0012] Preferably, the weight-average molecular weight of the polyether triol B is 4800.

[0013] Furthermore, the preparation method of the flexible buffer layer additive is as follows: hydroxyl-terminated polydimethylsiloxane is mixed with triethylamine, bifunctional modified hollow glass microspheres and epoxidized alumina are added, and the mixture is compounded under heating and stirring conditions, kept at the temperature and then cooled to obtain the flexible buffer layer additive.

[0014] Preferably, the weight ratio of the hydroxyl-terminated polydimethylsiloxane, the bifunctional modified hollow glass microspheres, and the epoxidized alumina is 35-70:160-240:6-15.

[0015] Preferably, the weight-average molecular weight of the hydroxyl-terminated polydimethylsiloxane is 1000.

[0016] Furthermore, the bifunctional modified hollow glass microspheres are obtained by introducing 3-glycidoxypropyltrimethoxysilane and octyltrimethoxysilane onto the surface of the hollow glass microspheres.

[0017] Preferably, the weight ratio of the hollow glass microspheres, 3-glycidoxypropyltrimethoxysilane, and octyltrimethoxysilane is 160-240:2-4:0.5-1.5.

[0018] Preferably, the hollow glass microspheres have a median particle size of 40 μm and a density of 0.46 g / cm³. 3 .

[0019] Furthermore, the epoxidized alumina is obtained by reacting nano-alumina with 3-glycidoxypropyltrimethoxysilane.

[0020] Preferably, the weight ratio of the nano-alumina to 3-glycidoxypropyltrimethoxysilane is 6-15:1.

[0021] Preferably, the average particle size of the nano-alumina is 40 nm.

[0022] Furthermore, the present invention also provides a preparation process for a multifunctional polyurethane foam material for use in building materials, comprising the following steps:

[0023] (1) Preparation of m-phenylenediamine solution: Mix ethanol and m-phenylenediamine and stir under heating conditions to obtain m-phenylenediamine solution;

[0024] (2) Preparation of component A: Polyether triol A, polyether triol B, flexible buffer layer additive, deionized water, organosilicon surfactant and dibutyltin dilaurate were mixed and stirred, ethylenediamine and diethylenetriamine were added, the temperature was raised and kept warm, and then m-phenylenediamine solution was added dropwise. Then the solvent was removed under heating and vacuum conditions to obtain component A.

[0025] (3) Foaming and curing: Add component B to component A, stir at high speed and pour into a preheated open mold, cure under heating conditions, demold and mature at room temperature to obtain a multifunctional polyurethane foam material for building materials.

[0026] Preferably, the weight ratio of ethanol to m-phenylenediamine in step (1) is 15:1.5-2.5.

[0027] Preferably, the mixing speed in step (2) is 1500 rpm and the time is 3 min.

[0028] Preferably, in step (2), the heating and holding process involves heating to 30-40℃ and holding for 5 minutes.

[0029] Preferably, in step (2), the solvent removal is carried out at 45°C and a vacuum of 0.08MPa for 8 minutes.

[0030] Preferably, the high-speed stirring speed in step (3) is 1500 rpm and the time is 10 s.

[0031] Preferably, in step (3), the mold is preheated to 60°C.

[0032] Preferably, the curing conditions in step (3) are 60°C for 120 min.

[0033] The beneficial effects of this invention are:

[0034] This invention modifies hollow glass microspheres with bifunctional silanes, simultaneously introducing epoxy reaction sites provided by 3-glycidoxypropyltrimethoxysilane and hydrophobic alkyl segments from octyltrimethoxysilane, achieving synergistic reconstruction of the filler surface. This modification creates a chemically bonded and wetting-compatible composite interface between the filler and the polyurethane foam wall, enhancing the uniform dispersion of the filler in the matrix and avoiding localized agglomeration and micropores that are prone to occur with traditional single modification, thereby improving the overall structural continuity of the material. Simultaneously, the introduction of alumina nanoparticles with epoxy groups on their surface further bridges the filler and the matrix. These particles can undergo ring-opening or addition reactions with amines or hydroxyl groups in the system, forming additional crosslinking points, strengthening the load-bearing network in the foam wall-filler transition zone, reducing stress concentration and crack initiation, and promoting effective load transfer.

[0035] Furthermore, the flexible buffer layer additive constructed in this invention is pre-composite with hydroxyl-terminated polydimethylsiloxane and modified fillers, introducing a strain-releasing mechanism between the rigid filler and the flexible foam wall. This buffer layer alleviates the accumulation of internal stress caused by modulus mismatch through the hysteretic energy dissipation of flexible segments and interfacial shear buffering, maintaining the morphological stability of the foam structure. Especially under hot and humid environments or mechanical loads, it suppresses microscale deformation and pore wall perforation. This not only optimizes the material's dimensional retention capability but also reduces the connectivity of solid heat conduction paths, contributing to the construction of a more uniform closed-cell network and reducing the thermal bridging effect of radiation and convection coupling.

[0036] Regarding flame retardancy, this invention utilizes in-situ polyurea bridging involving m-phenylenediamine to form a highly rigid aromatic network. This network, in conjunction with modified fillers, constructs a protective layer, extending the flame propagation path and promoting char densification. Simultaneously, the hydroxyl-terminated polydimethylsiloxane generates silicon-rich oxygen residues upon thermal decomposition, further enhancing the barrier effect of the inorganic filler, inhibiting oxygen permeation and heat release, and comprehensively improving the material's self-extinguishing ability and flame-retardant durability without relying on additional flame retardants, thus avoiding interference from traditional additives in the foaming reaction.

[0037] In summary, this invention addresses the weakening problem caused by the introduction of fillers by organically integrating bifunctional modified hollow glass microspheres, epoxidized alumina, flexible buffer layer additives, and m-phenylenediamine bridging, starting from the microscopic level of the interface. It achieves comprehensive optimization of thermal properties, mechanical strength, dimensional stability, and flame retardant characteristics, making it suitable for diverse needs in the field of building insulation. Attached Figure Description

[0038] Figure 1 The infrared spectra of the epoxidized alumina, bifunctional modified hollow glass microspheres, and flexible buffer layer additives in Example 2 of this invention are shown. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0040] Example 1:

[0041] (1) Take 950g of anhydrous ethanol, 50g of deionized water and 1g of glacial acetic acid and mix them. Stir at room temperature for 10min. Add 2g of 3-glycidoxypropyltrimethoxysilane and 0.5g of octyltrimethoxysilane and continue stirring for 30min for hydrolysis. Then add 160g of hollow glass microspheres (median particle size 40μm, density 0.46g / cm3). Reflux and stir at 78℃ for 120min. After filtration, wash with deionized water 3 times and dry in an oven at 110℃ for 60min to obtain bifunctional modified hollow glass microspheres.

[0042] (2) Take 190g of anhydrous ethanol, 10g of deionized water and 1g of glacial acetic acid, add 6g of nano alumina powder (average particle size 40nm), ultrasonically disperse for 10min, add 1g of 3-glycidoxypropyltrimethoxysilane, reflux and stir at 70℃ for 120min, filter and wash, and dry at 110℃ for 60min to obtain epoxidized alumina;

[0043] (3) Take 15g of ethanol and 1.5g of m-phenylenediamine, mix them, and stir at 40℃ for 15min to obtain a m-phenylenediamine solution;

[0044] (4) Take 35g of hydroxyl-terminated polydimethylsiloxane with a weight average molecular weight of 1000 and mix it with 0.2g of triethylamine. Stir at room temperature for 5min, then add 160g of bifunctional modified hollow glass microspheres and 6g of epoxidized alumina. Stir at 1000rpm for 30min at 45℃, keep warm at 50℃ for 15min, and cool to room temperature to obtain a flexible buffer layer additive.

[0045] (5) Add 450g of polyether triol with a weight average molecular weight of 2000, 350g of polyether triol with a weight average molecular weight of 4800, 205g of flexible buffer layer additive, 13g of deionized water, 8g of organosilicon surfactant (model Niax L-6900) and 0.8g of dibutyltin dilaurate to a planetary mixer and mix. Stir at 1500rpm for 3min at room temperature, then add 2g of ethylenediamine and 2g of diethylenetriamine. Stir at 25℃ for 1min and then heat to 30℃ and keep warm for 5min. Then add 13.5g of m-phenylenediamine solution. Stir at room temperature for 2min and then remove the solvent at 45℃ and vacuum degree of 0.08MPa for 8min to obtain component A.

[0046] (6) Add 380g of polymethylene polyphenyl isocyanate (model PM-200) to 1000g of component A, stir at 1500rpm for 10s and then quickly pour into an open mold preheated to 60℃. Cure at 60℃ for 120min, demold and place at room temperature for 24h to complete curing, and obtain a multifunctional polyurethane foam material for building materials.

[0047] Example 2:

[0048] (1) Mix 950g of anhydrous ethanol, 50g of deionized water and 1g of glacial acetic acid, stir at room temperature for 10min, add 3g of 3-glycidoxypropyltrimethoxysilane and 1g of octyltrimethoxysilane and continue stirring for 30min for hydrolysis, then add 200g of hollow glass microspheres (median particle size 40μm, density 0.46g / cm³). 3The mixture was refluxed and stirred at 78℃ for 120 min, filtered, washed three times with deionized water, and dried in an oven at 110℃ for 60 min to obtain bifunctional modified hollow glass microspheres.

[0049] (2) Take 190g of anhydrous ethanol, 10g of deionized water and 1g of glacial acetic acid, add 10g of nano alumina powder (average particle size 40nm), ultrasonically disperse for 10min, add 1g of 3-glycidoxypropyltrimethoxysilane, reflux and stir at 70℃ for 120min, filter and wash, and dry at 110℃ for 60min to obtain epoxidized alumina;

[0050] (3) Mix 15g of ethanol and 2g of m-phenylenediamine and stir at 40℃ for 15min to obtain a m-phenylenediamine solution;

[0051] (4) Take 50g of hydroxyl-terminated polydimethylsiloxane with a weight average molecular weight of 1000 and mix it with 0.2g of triethylamine. Stir at room temperature for 5min, then add 200g of bifunctional modified hollow glass microspheres and 10g of epoxidized alumina. Stir at 1000rpm for 30min at 45℃, keep warm at 50℃ for 15min, and cool to room temperature to obtain a flexible buffer layer additive.

[0052] (5) Add 500g of polyether triol with a weight average molecular weight of 2000, 400g of polyether triol with a weight average molecular weight of 4800, 260g of flexible buffer layer additive, 15g of deionized water, 10g of organosilicon surfactant (model Niax L-6900) and 1g of dibutyltin dilaurate to a planetary mixer and mix. Stir at 1500rpm for 3min at room temperature, then add 3g of ethylenediamine and 3g of diethylenetriamine. Stir at 25℃ for 1min and then heat to 35℃ and keep warm for 5min. Then add 17g of m-phenylenediamine solution. Stir at room temperature for 2min and then remove the solvent at 45℃ and vacuum degree of 0.08MPa for 8min to obtain component A.

[0053] (6) Add 380g of polymethylene polyphenyl isocyanate (model PM-200) to 1100g of component A, stir at 1500rpm for 10s and then quickly pour into an open mold preheated to 60℃. Cure at 60℃ for 120min, demold and place at room temperature for 24h to complete curing, and obtain a multifunctional polyurethane foam material for building materials.

[0054] Example 3:

[0055] (1) Take 950g of anhydrous ethanol, 50g of deionized water and 1g of glacial acetic acid and mix them. Stir at room temperature for 10min. Add 4g of 3-glycidoxypropyltrimethoxysilane and 1.5g of octyltrimethoxysilane and continue stirring for 30min for hydrolysis. Then add 240g of hollow glass microspheres (median particle size 40μm, density 0.46g / cm3). Reflux and stir at 78℃ for 120min. After filtration, wash with deionized water 3 times and dry in an oven at 110℃ for 60min to obtain bifunctional modified hollow glass microspheres.

[0056] (2) Take 190g of anhydrous ethanol, 10g of deionized water and 1g of glacial acetic acid, add 15g of nano alumina powder (average particle size 40nm), ultrasonically disperse for 10min, add 1g of 3-glycidoxypropyltrimethoxysilane, reflux and stir at 70℃ for 120min, filter and wash, and dry at 110℃ for 60min to obtain epoxidized alumina;

[0057] (3) Mix 15g of ethanol and 2.5g of m-phenylenediamine and stir at 40℃ for 15min to obtain a m-phenylenediamine solution;

[0058] (4) Take 70g of hydroxyl-terminated polydimethylsiloxane with a weight average molecular weight of 1000 and mix it with 0.2g of triethylamine. Stir at room temperature for 5min, then add 240g of bifunctional modified hollow glass microspheres and 15g of epoxidized alumina. Stir at 1000rpm for 30min at 45℃, keep warm at 50℃ for 15min, and cool to room temperature to obtain a flexible buffer layer additive.

[0059] (5) Add 550g of polyether triol with a weight average molecular weight of 2000, 450g of polyether triol with a weight average molecular weight of 4800, 325g of flexible buffer layer additive, 17g of deionized water, 12g of organosilicon surfactant (model Niax L-6900) and 1.2g of dibutyltin dilaurate to a planetary mixer and mix. Stir at 1500rpm for 3min at room temperature, then add 4g of ethylenediamine and 4g of diethylenetriamine. Stir at 25℃ for 1min and then heat to 40℃ and keep warm for 5min. Then add 22.5g of m-phenylenediamine solution. Stir at room temperature for 2min and then remove the solvent at 45℃ and vacuum degree of 0.08MPa for 8min to obtain component A.

[0060] (6) Add 380g of polymethylene polyphenyl isocyanate (model PM-200) to 1200g of component A, stir at 1500rpm for 10s and then quickly pour into an open mold preheated to 60℃. Cure at 60℃ for 120min, demold and place at room temperature for 24h to complete curing, and obtain a multifunctional polyurethane foam material for building materials.

[0061] Comparative Example 1:

[0062] The difference between Comparative Example 1 and Example 2 is that the hollow glass microspheres were not modified with any silane and were directly added to the system at the same amount, while the other conditions were the same as in Example 2.

[0063] Comparative Example 2:

[0064] The difference between Comparative Example 2 and Example 2 is that the hollow glass microspheres were modified with only 3-glycidoxypropyltrimethoxysilane monosilane without the addition of octyltrimethoxysilane, and the other conditions were the same as in Example 2.

[0065] Comparative Example 3:

[0066] The difference between Comparative Example 3 and Example 2 is that the hollow glass microspheres were modified with only octyltrimethoxysilane, without the addition of 3-glycidoxypropyltrimethoxysilane, while the other conditions were the same as in Example 2.

[0067] Comparative Example 4:

[0068] The difference between Comparative Example 4 and Example 2 is that unmodified nano-alumina was used instead of epoxidized alumina, the amount added remained the same, and the other conditions were the same as in Example 2.

[0069] Comparative Example 5

[0070] The difference between Comparative Example 5 and Example 2 is that aliphatic diamine (hexamethylenediamine) is used instead of m-phenylenediamine, with equivalent molar amounts, while the other conditions are the same as in Example 2.

[0071] Performance testing:

[0072] Apparent density test: The test was conducted according to GB / T 6343-2009. A sample of 50mm×50mm×50mm was cut and conditioned for 48 hours at 23±2℃ and 50±5% relative humidity. The sample was weighed using an electronic balance with an accuracy of 0.01g and the dimensions were measured using a vernier caliper. The apparent density was calculated and the results are shown in Table 1.

[0073] Compression strength test: The test was conducted in accordance with GB / T 8813-2008. A 50mm×50mm×50mm specimen was prepared and a universal testing machine was used to perform a compression strength test with a compression speed of 10mm / min and a deformation of 10%. The results are shown in Table 1.

[0074] Thermal conductivity test: The test was conducted according to GB / T 10295-2008. A sample of 300mm×300mm×25mm was prepared and tested using a thermal conductivity meter with a protective hot plate method under the conditions of an average temperature of 23℃ and a temperature difference of 20℃. The results are shown in Table 1.

[0075] Dimensional stability test: The test was conducted according to GB / T 8811-2008. The 50mm×50mm×25mm sample was treated in a 70℃ oven for 48h. The dimensional changes before and after the treatment were measured, and the dimensional change rates in the length, width and thickness directions were calculated. The results are shown in Table 1.

[0076] Flame retardant performance test: The test was conducted in accordance with GB / T 8332-2008. A 150mm×50mm×13mm sample was prepared, placed horizontally, and the combustion test was carried out. The combustion rate was recorded. The results are shown in Table 1.

[0077] Infrared spectrum: Measured using a Nicolet iS50 Fourier transform infrared spectrometer, the results are as follows: Figure 1 As shown.

[0078] Table 1 Performance Test Results

[0079]

[0080] Data Analysis:

[0081] According to the data from Examples 1-3 in Table 1, the apparent density of the multifunctional polyurethane foam material for building materials prepared by this invention is consistently between 36.8 and 38.5 kg / m³. 3 The compressive strength ranges from 0.29 to 0.34 MPa, the thermal conductivity remains between 0.0216 and 0.0225 W / (m·K), the dimensional change rate is controlled at approximately 0.3% to 1.1% in all three dimensions, and the combustion rate is approximately 18.6 to 22.4 mm / min, demonstrating a relatively balanced synergy between thermal and mechanical properties. It is speculated that the bifunctional silane remodels the surface of the hollow glass microspheres, enabling both chemical bonding and wetting compatibility between the bubble wall and the microspheres. The introduction of alumina nanoparticles with epoxy groups on the surface can undergo ring-opening or addition reactions with amines / hydroxyl groups, superimposed with in-situ polyurea bridging at the interface, forming a continuous load-bearing network of bubble wall-filler-matrix. The flexible transition layer constructed by hydroxyl-terminated polydimethylsiloxane achieves strain buffering and energy dissipation at the rigid-flexible interface, thus, together with process control, contributing to a uniform closed-cell structure and a low solid-radiative composite thermal conductivity channel.

[0082] According to the data from Example 2 and Comparative Example 1 in Table 1, compared with the system without silane modification of the hollow glass microspheres, Example 2 shows an overall trend of increased compressive strength, decreased thermal conductivity, reduced dimensional change rate, and decreased combustion rate. This may be because the hollow glass microspheres without surface reconstruction have insufficient wetting and chemical coupling with the bubble wall, which easily leads to debonding and micropores, resulting in stress concentration and increased thermal bridges. Example 2 introduces reactive and hydrophobic sites on the surface of the microspheres by synergistic grafting of 3-glycidoxypropyltrimethoxysilane and octyltrimethoxysilane, combined with alumina nanoparticles with epoxy groups on the surface and in-situ polyurea bridging at the interface, so that the bubble wall-filler form a more continuous load transfer path, reducing the initiation and propagation of microcracks and inhibiting solid thermal conduction channels; the flexible phase of hydroxyl-terminated polydimethylsiloxane further mitigates interfacial shear strain.

[0083] Based on the data from Example 2 and Comparative Example 2 in Table 1, it can be seen that although using 3-glycidoxypropyltrimethoxysilane alone can bring about a certain degree of interfacial reactivity, compared with Example 2, the compressive strength, thermal conductivity, and dimensional stability are all significantly lower, and the combustion rate is also higher. It is speculated that the absence of octyltrimethoxysilane results in insufficient hydrophobic alkyl coverage on the surface of the microspheres, limiting the wetting, spreading, and dispersion stability during foam formation. Local agglomeration and uneven pore wall formation are more likely to occur. Although reactive sites exist, under conditions of coexistence of water, amines, and isocyanates, without hydrophobic phase regulation, the interfacial region is more prone to forming a defect network, reducing load-bearing continuity and increasing the probability of thermal bridging.

[0084] Based on the data from Example 2 and Comparative Example 3 in Table 1, it can be seen that when only octyltrimethoxysilane is used, the data shows that the compression load, thermal conductivity, dimensional stability, and combustion rate are all inferior to those of Example 2. It is speculated that the hydrophobic alkyl group mainly improves compatibility and dispersion, but lacks the epoxy reaction sites provided by 3-glycidoxypropyltrimethoxysilane. The interaction between the bubble wall and the microspheres relies more on physical interactions rather than covalent anchoring, and the interfacial shear resistance and peel resistance are limited. Under cyclic loading and hot and humid environments, this interface is more likely to undergo microscale slip and void evolution, forming weakened regions and inducing thermal bridges, thereby affecting thermal conductivity and dimensional retention.

[0085] According to the data from Example 2 and Comparative Example 4 in Table 1, when unmodified alumina nanoparticles with epoxy groups on their surface are replaced with unmodified alumina nanoparticles, the compressive strength decreases, the thermal conductivity increases, the dimensional change rate increases, and the combustion rate accelerates. This trend can be attributed to the limited polar interaction between unmodified alumina and the organic phase, making the interface prone to slippage; while the epoxy-coated alumina nanoparticles can chemically react with amines and hydroxyl groups, providing additional crosslinking points, improving load transfer efficiency, constraining bubble wall deformation, reducing the probability of microcracks and pore wall perforation, thereby suppressing thermal bridging and gas exchange; at the same time, the more stable dispersion of nanoparticles can extend the heat and flame transfer path at the microscopic level, and combined with the barrier effect of hollow glass microspheres, it exhibits a combined improvement in thermal conductivity and flame retardancy.

[0086] Based on the data from Example 2 and Comparative Example 5 in Table 1, it can be seen that when aliphatic diamines are used instead of m-phenylenediamine, the compressive load decreases, the thermal conductivity increases, the dimensional change rate increases, and the combustion rate increases. It can be inferred that the polyurea bridging network formed by aromatic diamines has higher rigidity and thermal stability, which is beneficial for establishing high-modulus load-bearing beams in the cell wall-filler transition zone, suppressing interfacial creep and thermal deformation, and making it easier to form a dense carbon layer under thermal excitation. The aliphatic diamine network is relatively soft, with insufficient interfacial constraint and heat resistance, and is more likely to induce microscale slippage and pore wall thinning.

[0087] from Figure 1 It can be seen that the three infrared spectral lines in Example 2 of this invention correspond to epoxidized alumina, bifunctional modified hollow glass microspheres, and flexible buffer layer additives, respectively. A comparison shows that the bifunctional modified hollow glass microspheres have a wavelength range of 2960-2855 cm⁻¹. -1 The presence of -CH3 / -CH2 stretching vibrations indicates the successful introduction of the octylsilane segment; its 1090 cm⁻¹... -1 The Si-O-Si asymmetric stretching peaks on the left and right sides are strong and broadened, indicating the formation of a dense layer by silane condensation on the surface. The epoxidized alumina peaks at approximately 910 cm⁻¹... -1 With 840cm -1 The presence of epoxy ring fingerprint peaks indicates that reactive epoxy end groups are retained on its surface, which is beneficial for subsequent ring-opening reactions with amines / hydroxyl groups. The flexible buffer layer additive exhibits typical PDMS characteristics: 1260 cm⁻¹ -1 (Si-CH3 deformation) and approximately 800 cm -1 (Si-CH3 oscillation) is clearly discernible, and is also visible at 1000-1150 cm. -1 The interval overlaps with the Si-O-Si band of the filler and forms a broad peak / shoulder peak (approximately 1095 / 1010 cm⁻¹). -1 This indicates a significant synergistic effect between the flexible silicon-oxygen segments and the inorganic phase interface. Compared to the individual spectra of epoxide and alumina, the 910 / 840 cm⁻¹ spectra of the composite additive are significantly higher. -1The relatively weakened epoxy peak indicates that an interfacial reaction occurred during the composite process. The above evidence collectively demonstrates that the bifunctional modified hollow glass microspheres and epoxy-coated nano-alumina synergistically construct a reactive and mechanically continuous interfacial layer.

[0088] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A multifunctional polyurethane foam material for use in building materials, characterized in that, It is prepared by mixing component A and component B in a weight ratio of 1000-1200:380; Component A is prepared from the following raw materials in parts by weight: 450-550 parts of polyether triol A, 350-450 parts of polyether triol B, 205-325 parts of flexible buffer layer additive, 13-17 parts of deionized water, 8-12 parts of organosilicon surfactant, 0.8-1.2 parts of dibutyltin dilaurate, 2-4 parts of ethylenediamine, 2-4 parts of diethylenetriamine, and 1.5-2.5 parts of m-phenylenediamine; Component B is polymethylene polyphenyl isocyanate; The preparation method of the flexible buffer layer additive is as follows: hydroxyl-terminated polydimethylsiloxane and triethylamine are mixed, bifunctional modified hollow glass microspheres and epoxidized alumina are added, and the mixture is compounded under heating and stirring conditions, kept at the temperature and then cooled to obtain the flexible buffer layer additive. The weight ratio of the hydroxyl-terminated polydimethylsiloxane, bifunctional modified hollow glass microspheres, and epoxidized alumina is 35-70:160-240:6-15. The bifunctional modified hollow glass microspheres are obtained by introducing 3-glycidoxypropyltrimethoxysilane and octyltrimethoxysilane onto the surface of the hollow glass microspheres; The weight-average molecular weight of the polyether triol A is 2000, and the weight-average molecular weight of the polyether triol B is 4800. The weight ratio of the hollow glass microspheres, 3-glycidoxypropyltrimethoxysilane, and octyltrimethoxysilane is 160-240:2-4:0.5-1.

5.

2. The multifunctional polyurethane foam material for building materials according to claim 1, characterized in that, The weight-average molecular weight of the terminal hydroxyl polydimethylsiloxane is 1000.

3. The multifunctional polyurethane foam material for building materials according to claim 1, characterized in that, The hollow glass microspheres have a median particle size of 40 μm and a density of 0.46 g / cm³. 3 .

4. The multifunctional polyurethane foam material for building materials according to claim 1, characterized in that, The epoxidized alumina is obtained by reacting nano-alumina with 3-glycidoxypropyltrimethoxysilane; the weight ratio of the nano-alumina to 3-glycidoxypropyltrimethoxysilane is 6-15:

1.

5. A preparation process for a multifunctional polyurethane foam material for building materials according to any one of claims 1-4, characterized in that, Including the following steps: (1) Preparation of m-phenylenediamine solution: Mix ethanol and m-phenylenediamine and stir under heating conditions to obtain m-phenylenediamine solution; (2) Preparation of component A: Polyether triol A, polyether triol B, flexible buffer layer additive, deionized water, organosilicon surfactant and dibutyltin dilaurate were mixed and stirred, ethylenediamine and diethylenetriamine were added, the temperature was raised and kept warm, and then m-phenylenediamine solution was added dropwise. Then the solvent was removed under heating and vacuum conditions to obtain component A. (3) Foaming and curing: Add component B to component A, stir at high speed and pour into a preheated open mold, cure under heating conditions, demold and mature at room temperature to obtain a multifunctional polyurethane foam material for building materials.

6. The preparation process of the multifunctional polyurethane foam material for building materials according to claim 5, characterized in that, In step (1), the weight ratio of ethanol to m-phenylenediamine is 15:1.5-2.

5.

7. The preparation process of the multifunctional polyurethane foam material for building materials according to claim 6, characterized in that, The curing conditions in step (3) are 60℃ for 120 minutes.

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