Phase change microcapsule modification method and high-efficiency PCM-UHPC preparation method

Abstract

The invention discloses a phase change microcapsule modification method which comprises the following steps: S1, selecting a paraffin phase change material or a hydrated salt phase change material, and adding 0.5-1.5 wt% of a chemical stabilizer to modify the thermal stability of the phase change material; s2, compounding a microcapsule wall material by using polyurethane (PU) and nano silicon dioxide (SiO2), and adding 1wt% of carbon nanotubes (CNT) and 0.5-2wt% of nano silicon dioxide (SiO2); s3, the microcapsule wall material is subjected to surface hydrophobic coating treatment, polymethyl methacrylate (PMMA) is sprayed to form a waterproof isolation layer, the modified microcapsule phase change material is obtained, and in the step S1, 0.5-1.5 wt% of graphene oxide (GO) is added for modification when the paraffin phase change material is selected. The preparation method is reasonable in design, energy storage, heat preservation and mechanical properties of PCM-UHPC are remarkably improved through multi-layer composite modification of the PCM microcapsules and the nano-enhancement technology of the UHPC matrix, and the preparation method is suitable for the fields of energy-saving buildings, temperature control infrastructures and the like and has wide application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of building energy-saving materials and composite materials, and in particular to a phase change microcapsule modification method and a high-efficiency PCM-UHPC preparation method. Background Art

[0002] Currently, building materials are developing in the direction of energy conservation and multifunctionality. Ultra-high performance cement-based materials (UHPC) have high strength, low porosity and high durability, but they lack thermal insulation properties. Phase change materials (PCM) can store and release heat energy through phase change during temperature changes, and are suitable for building energy-saving applications. However, the direct application of phase change materials (PCM) in cement-based materials (UHPC) has problems such as fluidity, leakage and chemical aging, and needs to be modified through effective microencapsulation technology.

[0003] In addition, in order to achieve efficient composite of phase change material (PCM) and cement-based material (UHPC), it is necessary to modify the wall material of phase change material (PCM) microcapsules, the thermal stability of phase change material (PCM), the strength and interface bonding force of cement-based material (UHPC) matrix, etc. To this end, the present invention proposes a multi-layer composite modification method for PCM microcapsules, and combines it with a cement-based material (UHPC) matrix with optimized performance to form a high-performance and long-life PCM-UHPC composite material. Summary of the invention

[0004] The purpose of the present invention is to solve the problems existing in the prior art, and to propose a phase change microcapsule modification method and a high-efficiency PCM-UHPC preparation method, which significantly improves the energy storage and thermal insulation and mechanical properties of PCM-UHPC through multi-layer composite modification of PCM microcapsules and nano-enhancement technology of UHPC matrix, and is suitable for energy-saving buildings and temperature control infrastructure and other fields, and has broad application prospects.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The phase change microcapsule modification method comprises the following steps:

[0007] S1. Select a paraffin phase change material or a hydrated salt phase change material, and add 0.5-1.5wt% of a chemical stabilizer to modify the thermal stability of the phase change material;

[0008] S2, using polyurethane (PU) and nano-silicon dioxide (SiO2) composite microcapsule wall material, and adding 1wt% carbon nanotubes (CNT) and 0.5-2wt% nano-silicon dioxide (SiO2);

[0009] S3, performing a surface hydrophobic coating treatment on the microcapsule wall material, and spraying polymethyl methacrylate (PMMA) to form a waterproof isolation layer to obtain a modified microcapsule phase change material.

[0010] Preferably, in S1, when paraffin phase change material is selected, 0.5-1.5 wt % of graphene oxide (GO) is added for modification.

[0011] Preferably, in S1, when a hydrated salt phase change material is selected, 0.5-1 wt% of sodium chloride (NaCl) or a borate chemical stabilizer is added for modification.

[0012] Preferably, in S2, the inner wall material is a composite of polyurethane (PU) and nano silicon dioxide (SiO2).

[0013] Preferably, in S2, the interface of the microcapsule wall material surface is modified by coupling agent KH-570.

[0014] The high-efficiency PCM-UHPC preparation method is prepared using a modified microcapsule phase change material prepared by a phase change microcapsule modification method, and comprises the following steps:

[0015] S1. The modified microcapsule phase change material (PCM) is added to the ultra-high performance cement-based material (UHPC) at 3-5wt% of the total weight of the cement-based material (UHPC), in which the silicate cement accounts for 35-40wt%, the silica fume accounts for 8-10wt%, the fly ash accounts for 10-15wt%, and 2-3wt% of nano-silicon dioxide (SiO2) or nano-aluminum (Al2O3) is added to enhance the filling density of the matrix and improve the compressive and flexural strength of the ultra-high performance cement-based material (UHPC);

[0016] S2. Add water reducing agent and toughening fiber, mix well, cast into shape and perform standard curing to obtain high-efficiency PCM-UHPC composite material.

[0017] Preferably, in S2, the water reducing agent added is 1.5 wt% of polycarboxylic acid, and the toughening fiber is 2 wt% of polypropylene fiber.

[0018] Preferably, in S2, the material is poured into a mold for forming, cured in a humid environment for 24 hours, and then removed from the mold and cured for 28 days at 20° C. and 95% humidity.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] In the present invention, the thermal stability and anti-leakage property of PCM microcapsules are improved by adopting technologies such as multi-layer composite wall materials, nanomaterial reinforcement, and chemical stabilizers. At the same time, the modified PCM microcapsules and the performance-optimized UHPC matrix are combined to form a PCM-UHPC composite material with high energy storage efficiency and strong durability. The material can achieve temperature control in an environment with large temperature fluctuations, has excellent thermal stability and mechanical properties, and is suitable for energy-saving infrastructure projects such as buildings, bridges, and tunnels. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0022] The phase change microcapsule modification method comprises the following steps:

[0023] S1. Select paraffin phase change material or hydrated salt phase change material. Paraffin phase change material and hydrated salt phase change material have high thermal stability and long life. Pre-treat the phase change material. Heat the paraffin phase change material to 35-60°C and the hydrated salt phase change material to 5-10°C above its melting point. Add 0.5-1.5wt% of chemical stabilizer to modify the thermal stability of the phase change material to improve thermal cycle stability and prevent phase separation or chemical aging. Among them, when selecting paraffin phase change material, add 0.5-1.5wt% of graphene oxide (GO) for modification to enhance phase change stability. When selecting hydrated salt phase change material, such as calcium chloride hexahydrate, add 0.5-1wt% of sodium chloride (NaCl) or borate chemical stabilizer for modification to prevent phase separation and extend service life;

[0024] S2, the microcapsule wall material is a composite of polyurethane (PU) and nano-silicon dioxide (SiO2), and hydrophobic polymethyl methacrylate (PMMA) is added to the outer layer to form a multi-layer composite structure. Specifically, polyurethane (PU) and nano-silicon dioxide (SiO2) are used to composite microcapsule wall materials, and 1wt% of carbon nanotubes (CNT) are added to the polyurethane (PU) wall material to enhance the toughness and strength of the wall material and prevent the microcapsules from breaking during stirring. At the same time, the interface of the microcapsule wall material surface is modified by coupling agent KH-570 to improve the bonding force between the microcapsules and the cement matrix. The inner wall material is a composite of polyurethane (PU) and nano-silicon dioxide (SiO2), and the nano-silicon dioxide (SiO2) content is 0.5-2wt%, which improves the mechanical strength and high temperature resistance.

[0025] S3, performing a surface hydrophobic coating treatment on the microcapsule wall material, spraying polymethyl methacrylate (PMMA) on the outer wall material to form a waterproof isolation layer, effectively preventing the phase change material (PCM) from leaking, and obtaining a modified microcapsule phase change material.

[0026] Specifically, the preparation of microcapsule phase change material includes the following steps:

[0027] Preparation of wall material solution: prepare 5-10wt% polyurethane solution, add 1wt% carbon nanotubes and 0.5-2wt% nano silicon dioxide (SiO2), and disperse by ultrasonic for 15-30 minutes.

[0028] Emulsion polymerization: Phase change material (PCM) is gradually added to the wall material solution, stirred at a high speed of 500-1500rpm to form a stable emulsion, 0.1-0.5wt% crosslinking agent is added, the reaction temperature is 40-60°C, and the reaction time is 30-60 minutes.

[0029] Hydrophobic outer layer coating: Spray a hydrophobic polymethyl methacrylate (PMMA) solution on the outer layer of the formed microcapsules to form a hydrophobic layer, which is dried for later use.

[0030] The high-efficiency PCM-UHPC preparation method comprises the following steps:

[0031] S1. Add the modified microcapsule phase change material (PCM) to the ultra-high performance cement-based material (UHPC) at 3-5wt% of the total weight of the cement-based material (UHPC), and mix at a low speed of 200-400rpm for 5-10 minutes. In the ultra-high performance cement-based material (UHPC), the reasonable ratio of silicate cement, silica fume, and fly ash can effectively improve the density of the matrix, wherein silicate cement accounts for 35-40wt%, silica fume accounts for 8-10wt%, and fly ash accounts for 10-15wt%, and 2-3wt% of nano-silicon dioxide (SiO2) or nano-aluminum (Al2O3) is added to enhance the filling density of the matrix and improve the compressive and flexural strength of the ultra-high performance cement-based material (UHPC);

[0032] S2, add water reducer and toughening fiber, continue stirring for 5-10 minutes to make the slurry uniform, mix evenly, cast into shape and standard curing to obtain high-performance PCM-UHPC composite material. Among them, the water reducer added is 1.5wt% polycarboxylic acid to improve the fluidity of the material, and the toughening fiber added is 2wt% polypropylene fiber to improve the crack resistance and toughness of the material. Pour into the mold for molding, cure in a humid environment for 24 hours, and after demolding, cure for 28 days at 20°C and 95% humidity.

[0033] The present application is further described below through specific examples.

[0034] Example 1: Unmodified PCM-UHPC composite material

[0035] Raw material ratio:

[0036] UHPC matrix: Portland cement 35wt%, silica fume 8wt%, fly ash 12wt%, quartz powder 25wt%, quartz sand 17wt%, water reducer 1.5wt%.

[0037] PCM microcapsules: unmodified paraffin microcapsules 3wt%.

[0038] Preparation method: Prepare unmodified PCM-UHPC material according to the above ratio and process method, and perform standard curing.

[0039] Test results:

[0040] Compressive strength: 120MPa.

[0041] Flexural strength: 12MPa.

[0042] Thermal cycle stability: After 50 thermal cycles, the microcapsule breakage rate reaches 20%, and the phase change latent heat decays by 15%.

[0043] Example 2 (modified example): PCM-UHPC composite material using modified microcapsule PCM and UHPC matrix

[0044] Raw material ratio:

[0045] UHPC matrix: Portland cement 38wt%, silica fume 9wt%, fly ash 10wt%, quartz powder 25wt%, quartz sand 15wt%, water reducer 1.5wt%, nano-SiO2 content 2wt%.

[0046] Modified microcapsule PCM: 3wt%, paraffin is used as phase change material, 1wt% graphene oxide is added as stabilizer, the wall material is a composite of polyurethane and nano-silicon dioxide, and the outer layer is coated with PMMA.

[0047] Preparation method: Prepare the modified PCM-UHPC composite material according to the proportion and process method of the modification technical scheme, and carry out standard curing.

[0048] Test results:

[0049] Compressive strength: 135MPa (increased by 12.5%).

[0050] Flexural strength: 15MPa (increased by 25%).

[0051] Thermal cycle stability: After 100 thermal cycles, the breakage rate of microcapsules is only 5%, and there is no obvious attenuation of the latent heat of phase change.

[0052] Combining the test results of Example 1 and Example 2, it can be seen that the present invention significantly improves the energy storage and thermal insulation and mechanical properties of PCM-UHPC through the multi-layer composite modification of PCM microcapsules and the nano-enhancement technology of the UHPC matrix, and is suitable for energy-saving buildings and temperature control infrastructure and other fields, and has broad application prospects.

[0053] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A phase change microcapsule modification method, characterized in that: The following steps are involved: S1. Select a paraffin phase change material or a hydrated salt phase change material, and add 0.5-1.5wt% of a chemical stabilizer to modify the thermal stability of the phase change material; S2, using polyurethane (PU) and nano-silicon dioxide (SiO2) composite microcapsule wall material, and adding 1wt% carbon nanotubes (CNT) and 0.5-2wt% nano-silicon dioxide (SiO2); S3, performing a surface hydrophobic coating treatment on the microcapsule wall material, and spraying polymethyl methacrylate (PMMA) to form a waterproof isolation layer to obtain a modified microcapsule phase change material.

2. The phase change microcapsule modification method according to claim 1, characterized in that: In S1, when paraffin phase change material is selected, 0.5-1.5 wt % of graphene oxide (GO) is added for modification.

3. The phase change microcapsule modification method according to claim 1, characterized in that: In S1, when a hydrated salt phase change material is selected, 0.5-1 wt% of sodium chloride (NaCl) or a borate chemical stabilizer is added for modification.

4. The phase change microcapsule modification method according to claim 1, characterized in that: In the S2, the inner wall material is a composite of polyurethane (PU) and nano silicon dioxide (SiO2).

5. The phase change microcapsule modification method according to claim 1, characterized in that: In the above-mentioned S2, the interface of the microcapsule wall material surface is modified by coupling agent KH-570.

6. A method for preparing high-performance PCM-UHPC, using the modified microcapsule phase change material prepared by the phase change microcapsule modification method according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. The modified microcapsule phase change material (PCM) is added to the ultra-high performance cement-based material (UHPC) at 3-5wt% of the total weight of the cement-based material (UHPC), in which the silicate cement accounts for 35-40wt%, the silica fume accounts for 8-10wt%, the fly ash accounts for 10-15wt%, and 2-3wt% of nano-silicon dioxide (SiO2) or nano-aluminum (Al2O3) is added to enhance the filling density of the matrix and improve the compressive and flexural strength of the ultra-high performance cement-based material (UHPC); S2. Add water reducing agent and toughening fiber, mix well, cast into shape and perform standard curing to obtain high-efficiency PCM-UHPC composite material.

7. The high-performance PCM-UHPC preparation method according to claim 6, characterized in that: In the S2, the water reducing agent added is 1.5 wt% of polycarboxylic acid, and the toughening fiber is 2 wt% of polypropylene fiber.

8. The high-performance PCM-UHPC preparation method according to claim 6, characterized in that: In S2, the material is poured into a mold for forming, cured in a humid environment for 24 hours, and then removed from the mold and cured for 28 days at 20° C. and 95% humidity.