Multifunctional composite energy-saving material for building envelope and preparation method thereof

Abstract

The application relates to the technical field of building energy-saving materials, in particular to a multifunctional composite energy-saving material for building envelope structures and a preparation method thereof, which comprises 90-110 parts of lightweight aggregate, 15-30 parts of a cement-based binder and 15-30 parts of a microcapsule phase change unit according to weight parts; the microcapsule phase change unit has a particle size of 50-200 mu m; the microcapsule phase change unit is composed of a core-shell structure, the core is an organic phase change substance with a phase change temperature of 20-30 DEG C, and the shell is a crosslinked polymer layer doped with modified nano-Fe3O4. The application effectively suppresses indoor temperature fluctuation and reduces air conditioner energy consumption, and can be widely applied to building outer walls, inner walls, roofs and floors and the like, and provides an efficient energy-saving solution for modern buildings.

Description

Technical Field

[0001] This invention belongs to the field of building materials and energy-saving technology, specifically a multifunctional composite energy-saving material for building envelope and its preparation method. Background Technology

[0002] With the increasing demands for building energy conservation, the application of multifunctional composite energy-saving materials in building envelopes has gradually become a research hotspot. These materials not only need excellent thermal insulation performance but also need to meet multiple requirements such as phase change temperature regulation, sound insulation and noise reduction, environmental friendliness, ease of construction, and long-term durability to satisfy the demands of modern buildings for high-efficiency energy saving and intelligent development. However, existing building materials still have significant shortcomings in achieving multifunctional composite performance. Patent CN104773985B proposes a lightweight composite building energy-saving insulation material composed of various raw materials including ordinary silicate 42.5R cement, fiber magnesia, magnesium silicate fiber, wood fiber, lightweight magnesium oxide, and polypropylene fiber. It features thermal insulation, energy saving, fire resistance, non-combustibility, environmental friendliness, and waterproofing, and is suitable for thermal insulation of building exterior walls, interior walls, and roofs. However, this technical solution mainly focuses on improving thermal insulation performance and does not involve phase change temperature regulation. It cannot utilize the characteristic of phase change materials to absorb or release a large amount of latent heat at the phase change temperature point to smooth indoor temperature fluctuations, thereby improving thermal comfort and reducing air conditioning energy consumption. Furthermore, this material uses a mechanical spraying method, which, while convenient, requires high-quality substrate preparation, and its long-term durability and stability need further verification. Patent CN107002404B proposes a building material installed between the floor partition layer and the ground floor. Through optimized design of supporting components and multiple damping components, it can effectively block or suppress noise transmission between building floors. However, this technical solution mainly focuses on optimizing sound insulation performance, lacking comprehensive consideration of energy-saving performance and failing to integrate phase change temperature regulation or other multifunctional composite characteristics. At the same time, its structural design is relatively complex, installation is difficult, and its impact on the overall building load needs further evaluation. In addition, the single function of this material limits its widespread application in modern building envelopes.

[0003] The above problems indicate that existing building materials still have significant shortcomings in achieving multifunctional composite performance. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a multifunctional composite energy-saving material for building envelopes and its preparation method. This material effectively mitigates indoor temperature fluctuations and reduces air conditioning energy consumption. It can be widely applied to exterior walls, interior walls, roofs, and floors of buildings, providing a highly efficient energy-saving solution for modern buildings.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A multifunctional composite energy-saving material for building envelope, comprising, by weight, 90-110 parts of lightweight aggregate, 15-30 parts of cement-based binder and 15-30 parts of microcapsule phase change unit;

[0007] The microcapsule phase change unit has a particle size of 50-200 μm and is composed of a core-shell structure. Its core is an organic phase change material with a phase change temperature of 20-30℃, and its shell is a cross-linked polymer layer doped with modified nano-ferric oxide.

[0008] The core energy-saving mechanism of the multifunctional composite energy-saving material for the building envelope in this solution lies in the synergistic effect of lightweight aggregates and microcapsule phase change units: the lightweight aggregates, through their porous structure forming a low thermal conductivity layer, passively hinder the conduction of external heat to the interior (in summer) or indoor heat to the exterior (in winter), providing basic thermal insulation; while the core of the microcapsule phase change unit—an organic phase change substance with a phase change temperature of 20-30℃ (the human comfort temperature range)—actively undergoes phase change (melting absorbs heat / solidification releases heat) when the ambient temperature changes, dynamically absorbing or releasing a large amount of heat using the latent heat of phase change, thereby effectively buffering indoor temperature fluctuations (absorbing heat to suppress temperature rise during high-temperature periods and releasing heat to delay temperature drop during low-temperature periods), significantly reducing the peak load and energy consumption of the air conditioning and heating systems; the cross-linked polymer shell of the microcapsules ensures that the phase change substance does not leak during repeated phase change cycles, remains compatible with the matrix, and maintains structural stability. The combination of these two elements gives the building envelope excellent dynamic thermal inertia and temperature adaptive regulation capabilities, achieving intelligent control of the building's thermal environment and year-round energy saving.

[0009] Preferably, the organic phase change substance is one or more of paraffin, fatty acids, or alcohol compounds.

[0010] Preferably, the crosslinked polymer layer is formed by in-situ polymerization of a prepolymer monomer composed of silane-modified nano-ferric oxide or styrene with divinylbenzene or triethyl citrate.

[0011] Preferably, the lightweight aggregate is one or more of expanded perlite, ceramsite, or foam glass.

[0012] Preferably, the cement-based binder is silicate cement or sulfoaluminate cement.

[0013] This solution also discloses a method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope, including the following steps:

[0014] By weight:

[0015] Step (1): Heat 100 parts of organic phase change material to a molten state, add 2-4 parts of emulsifier and perform high-speed shear emulsification to obtain an emulsion with a particle size of 50-200 μm;

[0016] Step (2): Add 100-120 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 3-5 parts of crosslinking agent to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0017] The preparation process of the prepolymer monomer of silane-modified nano-ferric oxide is as follows:

[0018] Step (2.1): Disperse 100 parts of nano-Fe3O4 in 180-220 parts of ethanol-water mixed solution with a volume ratio of 2-3:1, add 15-17 parts of silane coupling agent KH550, and sonicate at 60℃ for 30 min to obtain silanized modified nano-Fe3O4 dispersion.

[0019] Step (2.2): 100-140 parts of melamine and 300 parts of 37% formaldehyde solution (molar ratio 1:2.8) are reacted at pH 8-9 (adjusted with ammonia) and 70-90℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0020] Step (2.3): Add the dispersion obtained in step (2.1) to the prepolymer in step (2.2) and stir at a constant temperature of 60-70℃ for 90 min to form a prepolymer monomer of silane modified nano iron oxide composite.

[0021] Step (3): Mix 90-110 parts of lightweight aggregate, 15-30 parts of cement-based binder and 15-30 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0022] Step (4): Pour the slurry obtained in step (3) into the mold, vibrate it to make it dense, cure it, and then demold it to obtain the composite energy-saving material.

[0023] By selecting alkali-resistant and robust cross-linked polymers as the outer shell and optimizing their particle size and surface properties, microcapsule phase change units can be successfully composited with cement-based binders to form a stable and durable structure. This excellent compatibility allows the phase change function to remain stable in the cement matrix for a long time, providing a fundamental guarantee for achieving high performance and energy saving in composite materials.

[0024] Molten organic phase change material (PCM) is subjected to high-speed shearing under the action of an emulsifier, utilizing mechanical energy to overcome the PCM's inherent aggregation tendency and interfacial tension between the two phases. Emulsifier molecules are directionally adsorbed at the oil-water interface, forming a stable interfacial film, reducing interfacial energy and generating steric hindrance / electrostatic repulsion, thereby inhibiting droplet coalescence and achieving uniform dispersion of the PCM at the target particle size in the aqueous phase, forming a kinetically stable emulsion. Water-soluble prepolymer monomers and crosslinking agents are added to the emulsion. The prepolymers are enriched on the surface of the PCM droplets and undergo interfacial polymerization. During the reaction, the monomers gradually polymerize at the droplet interface to form linear polymer chains, and subsequently, the crosslinking agent initiates interchain crosslinking reactions, forming a three-dimensional network structure. This network structure continues to grow and solidify on the droplet surface, ultimately forming a dense and mechanically strong crosslinked polymer shell, completely encapsulating the PCM core within microcapsules, achieving physical isolation and chemical protection of the solid-liquid PCM. Lightweight aggregates form the main framework, providing the foundation for the porous structure. Cement particles fill the voids between the aggregates and encapsulate microcapsules, initially wetting all particles through surface adsorption. The addition of water induces surface wetting and initial hydration reactions of the cement particles, forming a viscous cement paste. Through viscosity and capillary action, the paste forms a continuous transition phase between particles, adhering and temporarily stabilizing the components in a dispersed state, forming a plastic homogeneous composite paste system. After the paste is compacted in a mold, the moisture further optimizes the particle arrangement (reducing porosity) and triggers a deep hydration reaction of the cement: cement minerals dissolve to generate calcium and silicate ions, reacting to form hydrated calcium silicate (CSH) gel and calcium hydroxide (CH) crystals. The CSH gel is a nano-sized cementitious material that tightly binds to the aggregate and microcapsule surfaces, forming a three-dimensional network bonding phase. The pores of the lightweight aggregates and the shell of the microcapsules act as rigid support phases during the curing process, working synergistically with the cement gel to form an integrated composite structure, endowing the material with final mechanical strength and permanent fixation of functional units (phase change capsules).

[0025] In this scheme, nano-Fe3O4, after being modified by the silane coupling agent KH550, forms Fe-O-Si covalent bonds with melamine-formaldehyde resin to construct a percolation thermally conductive network, which significantly accelerates the heat storage / release response speed of the phase change material. At the same time, it strengthens the mechanical strength and impermeability of the microcapsule shell, and reduces the temperature fluctuation of the building envelope through magnetic heat absorption and uniform heat transfer characteristics, thereby comprehensively improving energy efficiency.

[0026] Preferably, in step (1), the emulsifier is a nonionic surfactant and the emulsification time is 10-30 min.

[0027] Preferably, in step (2), the crosslinking agent is triethyl citrate.

[0028] Preferably, in step (4), the curing conditions are a temperature of 20-30℃, a humidity of 80%-95%, and a curing time of 7-14 days.

[0029] Preferably, in step (1), the organic phase change substance is one or more of paraffin, fatty acids, or alcohol compounds.

[0030] Preferably, the lightweight aggregate is one or more of expanded perlite, ceramsite, or foam glass.

[0031] Preferably, the cement-based binder is silicate cement or sulfoaluminate cement.

[0032] Compared to existing technologies, the advantages of this solution are:

[0033] 1. This solution uses core-shell structured microcapsule phase change units to replace traditional directly doped phase change materials. The cross-linked polymer outer shell effectively isolates the organic phase change material from contact with the alkaline cement matrix, fundamentally solving the problems of leakage, migration, and chemical corrosion of phase change components. At the same time, the lightweight aggregate, cement matrix, and capsule phase change unit are synergistically composited at a gradient scale (aggregate macropores / cement micron filling / capsule functional regulation), avoiding inorganic-organic interface failure and achieving independent optimization and integrated integration of thermal insulation and thermal storage functions.

[0034] 2. In-situ polymerization at the emulsion interface directly constructs a cross-linked polymer shell on the surface of phase change droplets in one step, simplifying the complex process of separation and drying required by traditional microcapsules and avoiding capsule breakage. The lightweight aggregate, dry cement powder and solid microcapsules are mixed first, and then water is added and stirred to minimize the risk of swelling / erosion of the capsule shell by the high water content slurry, ensuring the integrity and dispersion uniformity of functional units and strong process controllability. Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0038] By weight:

[0039] Step (1): Heat 100 parts of organic phase change material to a molten state, add 3 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 15 min to obtain an emulsion with a particle size of 80-100 μm;

[0040] Step (2): Add 100 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0041] Step (2.1): Disperse 100 parts of nano-iron oxide (particle size 20nm) in 200 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0042] Step (2.2): 120 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0043] Step (2.3): Add the dispersion obtained in step (2.1) to the melamine-formaldehyde prepolymer obtained in step (2.2), and stir at 65°C for 90 min to form a silane-modified nano-iron oxide composite prepolymer monomer.

[0044] Step (3): Mix 90 parts of expanded perlite, 25 parts of silicate cement and 25 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0045] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 10 days at a temperature of 25℃ and a humidity of 85%. After demolding, the composite energy-saving material is obtained.

[0046] Example 2

[0047] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0048] By weight:

[0049] Step (1): Heat 100 parts of paraffin wax to a molten state, add 3 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 20 minutes to obtain an emulsion with a particle size of 80-120μm;

[0050] Step (2): Add 100 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0051] Step (2.1): Disperse 100 parts of nano-iron oxide (particle size 20nm) in 180 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0052] Step (2.2): 130 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0053] Step (2.3): Add the dispersion obtained in step (2.1) to the melamine-formaldehyde prepolymer obtained in step (2.2), and stir at 65°C for 90 min to form a silane-modified nano-iron oxide composite prepolymer monomer.

[0054] Step (3): Mix 95 parts of expanded perlite, 20 parts of silicate cement and 25 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0055] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 12 days at a temperature of 22℃ and a humidity of 90%. After demolding, the composite energy-saving material is obtained.

[0056] Example 3

[0057] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0058] By weight:

[0059] Step (1): Heat 100 parts of paraffin wax to a molten state, add 4 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 25 minutes to obtain an emulsion with a particle size of 120-150 μm;

[0060] Step (2): Add 110 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0061] Step (2.1): Disperse 100 parts of nano-iron oxide (particle size 20nm) in 200 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0062] Step (2.2): 120 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0063] Step (2.3): Add the dispersion obtained in step (2.1) to the melamine-formaldehyde prepolymer obtained in step (2.2), and stir at 65°C for 90 min to form a silane-modified nano-iron oxide composite prepolymer monomer.

[0064] Step (3): Mix 100 parts of expanded perlite, 25 parts of silicate cement and 20 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0065] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 14 days at a temperature of 28℃ and a humidity of 82%. After demolding, the composite energy-saving material is obtained.

[0066] Example 4

[0067] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0068] By weight:

[0069] Step (1): Heat 100 parts of paraffin wax to a molten state, add 2 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 10 min to obtain an emulsion with a particle size of 150-180 μm;

[0070] Step (2): Add 100 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 5 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0071] Step (2.1): Disperse 100 parts of nano-iron oxide (particle size 20nm) in 200 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0072] Step (2.2): 120 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0073] Step (2.3): Add the dispersion obtained in step (2.1) to the melamine-formaldehyde prepolymer obtained in step (2.2), and stir at 65°C for 90 min to form a silane-modified nano-iron oxide composite prepolymer monomer.

[0074] Step (3): Mix 105 parts of expanded perlite, 18 parts of silicate cement and 26 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0075] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 7 days at a temperature of 30℃ and a humidity of 95%. After demolding, the composite energy-saving material is obtained.

[0076] Example 5

[0077] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0078] By weight:

[0079] Step (1): Heat 100 parts of paraffin wax to a molten state, add 3 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 30 minutes to obtain an emulsion with a particle size of 180-200μm;

[0080] Step (2): Add 100 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0081] Step (2.1): Disperse 100 parts of nano-iron oxide (particle size 20nm) in 200 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0082] Step (2.2): 120 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0083] Step (2.3): Add the dispersion obtained in step (2.1) to the melamine-formaldehyde prepolymer obtained in step (2.2), and stir at 65°C for 90 min to form a silane-modified nano-iron oxide composite prepolymer monomer.

[0084] Step (3): Mix 110 parts of expanded perlite, 22 parts of silicate cement and 28 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0085] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 9 days at a temperature of 20℃ and a humidity of 88%. After demolding, the composite energy-saving material is obtained.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that no microcapsule phase change unit was added:

[0088] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0089] By weight:

[0090] Mix 90 parts expanded perlite and 25 parts silicate cement evenly, add an appropriate amount of water and stir to form a slurry; pour the slurry into a mold, vibrate to compact it, and then cure it for 10 days at a temperature of 25℃ and a humidity of 85%. After demolding, the composite energy-saving material is obtained.

[0091] Comparative Example 2

[0092] The difference from Example 1 is that silane-modified nano-iron oxide was not added:

[0093] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0094] By weight:

[0095] Step (1): Heat 100 parts of organic phase change material to a molten state, add 3 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 15 min to obtain an emulsion with a particle size of 80-100 μm;

[0096] Step (2): Add 100 parts of prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0097] Step (3): Mix 90 parts of expanded perlite, 25 parts of silicate cement and 25 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0098] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 10 days at a temperature of 25℃ and a humidity of 85%. After demolding, the composite energy-saving material is obtained.

[0099] Comparative Example 3

[0100] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0101] By weight:

[0102] The difference from Example 1 is that an excessive amount of modified nano-ferric oxide was added:

[0103] Step (1): Heat 100 parts of organic phase change material to a molten state, add 3 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 15 min to obtain an emulsion with a particle size of 80-100 μm;

[0104] Step (2): Add 100 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0105] Step (2.1): Disperse 150 parts of nano-iron oxide (particle size 20nm) in 200 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0106] Step (2.2): 120 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0107] Step (2.3): Add the dispersion obtained in step (2.1) to the melamine-formaldehyde prepolymer obtained in step (2.2), and stir at 65°C for 90 min to form a silane-modified nano-iron oxide composite prepolymer monomer.

[0108] Step (3): Mix 90 parts of expanded perlite, 25 parts of silicate cement and 25 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0109] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 10 days at a temperature of 25℃ and a humidity of 85%. After demolding, the composite energy-saving material is obtained.

[0110] Comparative Example 4

[0111] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0112] By weight:

[0113] Step (1): Heat 100 parts of organic phase change material to a molten state, add 3 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 15 min to obtain an emulsion with a particle size of 80-100 μm;

[0114] Step (2): Add 100 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0115] Step (2.1): Disperse 100 parts of nano-iron oxide (particle size 20nm) in 200 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0116] Step (2.2): 120 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0117] Step (2.3): Add the dispersion obtained in step (2.1) to the melamine-formaldehyde prepolymer obtained in step (2.2), and stir at 65°C for 90 min to form a silane-modified nano-iron oxide composite prepolymer monomer.

[0118] Step (3): Mix 90 parts of expanded perlite, 25 parts of silicate cement and 25 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0119] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 10 days at a temperature of 25℃ and a humidity of 85%. After demolding, the composite energy-saving material is obtained.

[0120] Comparative Example 5

[0121] The difference from Example 1 is that the microcapsule phase change unit is in excess:

[0122] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0123] By weight:

[0124] Step (1): Heat 100 parts of organic phase change material to a molten state, add 3 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 15 min to obtain an emulsion with a particle size of 80-100 μm;

[0125] Step (2): Add 100 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0126] Step (2.1): Disperse 100 parts of nano-iron oxide (particle size 20nm) in 200 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0127] Step (2.2): 120 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0128] Step (2.3): Add the dispersion obtained in step (2.1) to the melamine-formaldehyde prepolymer obtained in step (2.2), and stir at 65°C for 90 min to form a silane-modified nano-iron oxide composite prepolymer monomer.

[0129] Step (3): Mix 90 parts of expanded perlite, 25 parts of silicate cement and 35 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0130] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 10 days at a temperature of 25℃ and a humidity of 85%. After demolding, the composite energy-saving material is obtained.

[0131] Comparative Example 6

[0132] The difference from Example 1 is that the silane-modified nano-ferric oxide composite prepolymer monomer was not prepared in advance:

[0133] A method for preparing the above-mentioned multifunctional composite energy-saving material for building envelope includes the following steps:

[0134] By weight:

[0135] Step (1): Heat 100 parts of organic phase change material to a molten state, add 3 parts of emulsifier (fatty acid polyoxyethylene ester) and perform high-speed shear emulsification treatment for 15 min to obtain an emulsion with a particle size of 80-100 μm;

[0136] Step (2): Add 50 parts of silane-modified nano iron oxide dispersion, 85 parts of prepolymer monomer and 4 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification.

[0137] Step (2.1): Disperse 100 parts of nano-iron oxide (particle size 20nm) in 200 parts of ethanol-water mixed solution with a volume ratio of 3:1, add 15 parts of silane coupling agent KH550, and sonicate at 60℃ for 30min with a power of 300W to obtain silanized modified nano-iron oxide dispersion.

[0138] Step (2.2): 120 parts of melamine and 300 parts of 37% formaldehyde solution were reacted at pH=8.5 and 75℃ for 40 min to generate melamine-formaldehyde prepolymer;

[0139] Step (3): Mix 90 parts of expanded perlite, 25 parts of silicate cement and 25 parts of microcapsule phase change unit evenly, add an appropriate amount of water and stir into a slurry;

[0140] Step (4): Pour the slurry into the mold, vibrate it to make it compact, and then cure it for 10 days at a temperature of 25℃ and a humidity of 85%. After demolding, the composite energy-saving material is obtained.

[0141] Material parameter testing methods:

[0142] 1. Thermal conductivity: According to GB / T 10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method" or GB / T 10295-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - heat flow meter method".

[0143] 2. Density: According to GB / T 5486-2008 "Test Methods for Inorganic Rigid Thermal Insulation Products", the mass and volume of the sample were measured after drying.

[0144] 3. Compressive strength: Tested using a pressure testing machine in accordance with GB / T 5486-2008 "Test Methods for Inorganic Rigid Thermal Insulation Products";

[0145] 4. GB / T 34477-2017 Acetone extraction weight loss method after hot and cold cycling.

[0146] Performance requirements: The thermal conductivity of the composite energy-saving material should be 0.03-0.05 W / (m·K), and the density should be 300-500 kg / m³. 3 The compressive strength is 0.5-1.2 MPa.

[0147] The performance results are shown in Table 1.

[0148] Table 1

[0149] Example 1 380±10 0.038 0.82 2.8 Example 2 360±15 0.04 0.75 3.1 Example 3 345±8 0.041 0.68 3.5 Example 4 400±12 0.036 0.93 2.5 Example 5 420±15 0.042 0.95 3.8 Comparative Example 1 290±10 0.068 1.2 - Comparative Example 2 365±8 0.061 0.73 19.3 Comparative Example 3 465±20 0.048 0.32 37.5 Comparative Example 4 380±10 0.038 0.82 2.8 Comparative Example 5 275±5 0.031 0.25 8.9 Comparative Example 6 370±12 0.059 0.57 31.7

[0150] Examples 1-5 utilize a pre-compounding process to form a chemically bonded thermally conductive network of silanized nano-Fe3O4 within a resin matrix: the hydrolyzed groups of the silane coupling agent KH550 undergo dehydration condensation with the hydroxyl groups on the surface of Fe3O4, forming Fe-O-Si covalent bonds; simultaneously, the alkane chains crosslink with the hydroxymethyl groups of the melamine-formaldehyde resin, constructing an integrated nanoparticle-resin framework. This structure produces a triple synergistic effect:

[0151] 1. Enhanced heat transfer: The iron oxide nuclei are directly coupled to the resin matrix through chemical bonds, eliminating interfacial phonon scattering and increasing the mean free path of phonons to the lattice scale.

[0152] 2. Phase transition regulation enhancement: The nanoparticle surface forms atomic-level roughness, which acts as nucleation sites for paraffin heterogeneous phases, thereby reducing the activation energy barrier of phase transition;

[0153] 3. Structural stability assurance: The chemical cross-linked network resists thermal stress deformation and inhibits the initiation of microcracks during phase transformation cycles.

[0154] In contrast, Comparative Example 1 exhibited sluggish thermal response due to the lack of phase change units; Comparative Example 2, with its unmodified iron oxide, created a thermal barrier at the physical adsorption interface; Comparative Example 3, with its excessive iron oxide, caused agglomeration that damaged the cement matrix; Comparative Example 5, with its excessive phase change units, hindered cement hydration; and Comparative Example 6, with its stepwise addition, resulted in iron oxide-resin debonding and a high leakage rate. The essential difference lies in the fact that the chemically bonded network simultaneously achieves directional heat transfer and coordinated mechanical strain, while the comparative examples lost this synergistic mechanism due to interface defects or component imbalances, leading to decreased thermal conductivity, structural damage, or functional failure.

Claims

1. A multifunctional composite energy-saving material for building envelope, characterized in that, By weight, it comprises 90-110 parts of lightweight aggregate, 15-30 parts of cement-based binder and 15-30 parts of microcapsule phase change unit; The microcapsule phase change unit has a particle size of 50-200μm and is composed of a core-shell structure. Its core is an organic phase change material with a phase change temperature of 20-30℃, and its shell is a cross-linked polymer layer doped with modified nano-ferric oxide. The preparation scheme of the microcapsule phase change unit is as follows: By weight: Step (1): Heat 100 parts of organic phase change material to a molten state, add 2-4 parts of emulsifier and perform high-speed shear emulsification to obtain an emulsion; Step (2): Add 100-120 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 3-5 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification. The preparation process of the silane-modified nano-ferric oxide composite prepolymer monomer is as follows: Step (2.1): Disperse 100 parts of nano-Fe3O4 in 180-220 parts of ethanol-water mixed solution with a volume ratio of 2-3:1, add 15-17 parts of silane coupling agent KH550, and sonicate at 60℃ for 30 min to obtain silanized modified nano-Fe3O4 dispersion. Step (2.2): React 100-140 parts of melamine with 300 parts of 37% formaldehyde solution at pH=8-9 and 70-90℃ for 40 min to generate melamine-formaldehyde prepolymer; Step (2.3): Add the dispersion obtained in step (2.1) to the prepolymer in step (2.2) and stir at a constant temperature of 60-70℃ for 90 min to form a prepolymer monomer of silane modified nano iron oxide composite.

2. The multifunctional composite energy-saving material for building envelope as described in claim 1, characterized in that, The organic phase change substance is one or more of paraffin, fatty acids, or alcohol compounds; the cross-linked polymer layer is formed by in-situ polymerization of melamine-formaldehyde prepolymer compounded with silane-modified nano-Fe3O4 and triethyl citrate; the lightweight aggregate is one or more of expanded perlite, ceramsite, or foam glass; and the cement-based binder is silicate cement or sulfoaluminate cement.

3. A method for preparing a multifunctional composite energy-saving material for building envelope as described in any one of claims 1-2, characterized in that, Includes the following steps: By weight: Step (1): Heat 100 parts of organic phase change material to a molten state, add 2-4 parts of emulsifier and perform high-speed shear emulsification to obtain an emulsion; Step (2): Add 100-120 parts of silane-modified nano-Fe3O4 composite prepolymer monomer and 3-5 parts of triethyl citrate to the emulsion obtained in step (1), stir evenly and carry out in-situ polymerization reaction, and obtain microcapsule phase change unit after cooling and solidification. Step (3): Mix 90-110 parts of lightweight aggregate, 15-30 parts of cement-based binder and 15-30 parts of microcapsule phase change unit evenly, add water and stir into a slurry; Step (4): Pour the slurry obtained in step (3) into the mold, vibrate it to make it dense, cure it, and then demold it to obtain the composite energy-saving material.

4. The preparation method of the multifunctional composite energy-saving material for building envelope as described in claim 3, characterized in that, In step (1), the emulsifier is a nonionic surfactant, and the emulsification time is 10-30 min.

5. The preparation method of the multifunctional composite energy-saving material for building envelope as described in claim 3, characterized in that, In step (4), the curing conditions are a temperature of 20-30℃, a humidity of 80%-95%, and a curing time of 7-14 days.

6. The preparation method of the multifunctional composite energy-saving material for building envelope as described in claim 3, characterized in that, The organic phase change substance is one or more of paraffin, fatty acids, or alcohol compounds; the lightweight aggregate is one or more of expanded perlite, ceramsite, or foam glass; and the cement-based binder is silicate cement or sulfoaluminate cement.