阅读说明：本技术 一种用于智能窗的热致变色复合材料 (Thermochromic composite material for intelligent window ) 是由 李建国 刘洋 苗庆显 陈礼辉 黄六莲 于 2021-09-23 设计创作，主要内容包括：本发明公开了一种用于智能窗的热致变色复合材料及其制备方法,把水溶性的CMC引入到PNIPAM或HPC的水分散液中,利用CMC的亲水性,降低PNIPAM或HPC的相变温度；利用CMC在水中形成的分子骨架,增加PNIPAM或HPC的散射中心数量,提升太阳能调制能力,增强热致变色材料的热稳定性。方法简单有效,应用前景广阔。(The invention discloses a thermochromic composite material for an intelligent window and a preparation method thereof, wherein water-soluble CMC is introduced into a PNIPAM or HPC aqueous dispersion, and the hydrophilicity of the CMC is utilized to reduce the phase transition temperature of the PNIPAM or HPC; the molecular skeleton formed by CMC in water is utilized to increase the number of scattering centers of PNIPAM or HPC, improve the solar energy modulation capability and enhance the thermal stability of the thermochromic material. The method is simple and effective, and has wide application prospect.)

1. A preparation method of a thermochromic composite material is characterized by comprising the following steps: and uniformly mixing the thermochromic material with the sodium carboxymethyl cellulose solution to obtain the thermochromic composite material.

2. The method of claim 1, wherein: the thermochromic material is 0.1-5% of poly isopropyl acrylamide solution or 0.5-1.5% of hydroxypropyl cellulose solution by mass fraction.

3. The method of claim 1, wherein: the degree of substitution of the sodium carboxymethylcellulose is 0.5 to 1.5.

4. The method of claim 1, wherein: the molar mass of the sodium carboxymethylcellulose is 90,000-1000,000 g/mol.

5. The method of claim 1, wherein: the mass fraction of the sodium carboxymethylcellulose in the thermochromic composite material is 0.005-3%.

6. Use of the thermochromic composite made according to claim 1 in a smart window.

7. Use according to claim 7, characterized in that: and filling the thermochromic composite material into the laminated glass, and sealing to obtain the thermochromic intelligent window.

8. The method of claim 8, wherein: the thickness of the glass interlayer is 0.5 mm-5 mm.

Technical Field

The invention belongs to the technical field of intelligent materials and responsive polymers, and particularly relates to a thermochromic composite material for an intelligent window and a preparation method thereof.

Background

Excessive consumption of global energy is considered to be a significant challenge for human development and progress, and buildings account for about 40% -50% of global energy consumption. It is worth noting that in a building, a window accounts for about 40% of the total energy consumption, and is the most serious part of the energy consumption in the building. Specifically, the sunlight with energy passes through the windows of the building and enters the room to be converted into heat energy, thereby causing the interior of the building to heat up. Especially in hot seasons, sufficient solar radiation causes the indoor temperature to rise rapidly. Due to the higher indoor temperature, the air conditioner will consume more power to maintain a relatively lower, comfortable indoor temperature. In order to block the high energy consumption problem caused by solar radiation passing through windows to directly heat rooms, smart windows were born and developed to date.

The intelligent window can change the transparent state of the intelligent window according to the requirement, so that the quantity of sunlight entering the room can be regulated and controlled. In the transparent state, sunlight can pass through the smart window like ordinary glass for daylighting and heating indoor temperature. In the semitransparent or opaque state, partial or even all light can be blocked, so that heat in a room is prevented from being obtained, the effect of inhibiting the temperature in the room from rising is achieved, and the energy consumption caused by refrigeration needs is reduced. Common smart windows are thermochromic, electrochromic and photochromic windows. The photochromic window is expensive, external equipment needs to be matched with the electrochromic window, electric energy is consumed, the thermochromic window is simple to manufacture, the cost is low, and the shading effect is relatively excellent.

Poly isopropyl acrylamide (PNIPAM) and hydroxypropyl cellulose (HPC) are two cheap thermochromic materials, can respectively perform phase transition at the temperature of 32 ℃ and 42 ℃, enable aqueous dispersion to change from a transparent state to a milky color, and can effectively block solar radiation. PNIPAM is environmentally friendly and is commonly used in medicine for drug delivery. HPC is non-toxic and harmless and is commonly used in the food industry as stabilizers and thickeners. Although the research on PNIPAM and HPC has been extensive, there still exist some problems, such as high phase transition temperature of the PNIPAM and HPC thermochromic window, poor solar modulation ability, and poor stability. Because the phase transition temperature of the single PNIPAM and HPC aqueous dispersion is higher, the phase transition can not happen in time to form timely and effective blocking to solar radiation. Under the high temperature state, the gel microspheres formed by PNIPAM or HPC can agglomerate, so that the quantity of scattering centers of the product is reduced, and the solar energy modulation capability of the product is poor. In addition, the PNIPAM and HPC aqueous dispersion are unstable, on the one hand, they are rich in moisture, which is easily volatilized; on the other hand, PNIPAM and HPC are precipitated when they are kept at a high temperature for a long time, resulting in a decrease in light-shielding performance. Therefore, a green and economic means is found to solve the problems of high phase transition temperature and unstable aqueous dispersion of PNIPAM and HPC, which is of great significance to the practical application of PNIPAM and HPC-based thermochromic windows.

Sodium carboxymethyl cellulose (CMC) is a cellulose obtained by carboxymethylation of natural cellulose, and the aqueous solution of the CMC has the functions of thickening, water retention, suspension and the like, is usually used in the food and drug industry, and is a product with cheap pigment. The abundant hydroxyl and carboxyl of CMC have extremely strong hydrophilic acting force, and the static CMC solution has a three-dimensional network skeleton, can play a role in supporting suspended matters and ensuring the dispersion stability of the dispersed matters in the solution.

Disclosure of Invention

The invention aims to provide a thermochromic composite material for an intelligent window and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a thermochromic composite material comprises the following steps: and uniformly mixing the thermochromic material dispersion liquid and the sodium carboxymethyl cellulose solution to obtain the thermochromic composite material.

The thermochromic material dispersion liquid is 0.1-5% of poly isopropyl acrylamide (PNIPAM) dispersion liquid or 0.5-1.5% of hydroxypropyl cellulose (HPC) dispersion liquid in mass concentration and mass fraction, and the solvent is water.

The substitution degree of sodium carboxymethylcellulose (CMC) in the thermochromic composite material is 0.5-1.5.

The molar mass of the sodium carboxymethylcellulose in the thermochromic composite material is 90,000-1000,000 g/mol.

The mass fraction of the sodium carboxymethylcellulose in the thermochromic composite material is 0.005-3%.

The application of the thermochromic composite material prepared by the method on the intelligent window comprises the following steps: and filling the thermochromic composite material into the laminated glass, and sealing to obtain the thermochromic intelligent window. The thickness of the glass interlayer is 0.5 mm-5 mm.

The invention has the beneficial effects that: the invention provides a preparation method of a cellulose-reinforced thermochromic window, which can obviously reduce the phase change temperature of PNIPAM and HPC-based thermochromic windows and enable the solar energy modulation capability effect of an intelligent window to be more obvious; the supporting effect of the CMC molecular skeleton not only improves the number of PNIPAM and HPC scattering centers, but also improves the thermal stability of the PNIPAM and HPC-based thermochromic window, so that the PNIPAM and HPC-based thermochromic window can play a role stably for a long time, and the service life of the PNIPAM and HPC-based thermochromic window is greatly prolonged.

Detailed Description

In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.

Example 1: preparation of cellulose-reinforced PNIPAM-based thermochromic windows

(1) With N, N^＇-dipropylacrylamide is used as a cross-linking agent, ammonium persulfate is used as a catalyst, and PNIPAM is synthesized by a soap-free emulsion polymerization method; preparing PNIPAM aqueous dispersion;

(2) preparing 0.04 g/mL CMC solution with the substitution degree of 0.5 and the molecular weight of 90,000 g/mol;

(3) mixing the PNIPAM aqueous dispersion, the CMC solution and water to obtain the CMC/PNIPAM thermochromic composite material with the mass fraction of 0.005% of CMC and 0.1% of PNIPAM.

(4) And injecting the CMC/PNIPAM thermochromic composite material between double-layer glass with the interlayer thickness of 0.5mm, and sealing to obtain the thermochromic window.

The phase transition temperature of the CMC/PNIPAM is measured to be 32.3 ℃ by a differential scanning calorimeter, and at the temperature of 32.3 ℃, the solar modulation capacity of the thermochromic window is measured and calculated to be about 53% by an ultraviolet/visible light/near infrared spectrophotometer; by the constant-temperature heating method, it was observed that the dispersion stability of CMC/PNIPAM slightly decreased after being left at 60 ℃ for 7 days.

Example 2: preparation of cellulose-reinforced PNIPAM-based thermochromic windows

(1) With N, N^＇-dipropylacrylamide is used as a cross-linking agent, ammonium persulfate is used as a catalyst, and PNIPAM is synthesized by a soap-free emulsion polymerization method; preparing PNIPAM aqueous dispersion;

(2) preparing 0.04 g/mL CMC solution with the substitution degree of 1 and the molecular weight of 100,000 g/mol;

(3) mixing the PNIPAM aqueous dispersion, the CMC solution and water to obtain the CMC/PNIPAM thermochromic composite material with the mass fraction of 1.5 percent of CMC and 2.5 percent of PNIPAM.

(4) And injecting the CMC/PNIPAM thermochromic composite material between double-layer glass with the interlayer thickness of 4.5 mm, and sealing to obtain the thermochromic window.

The phase transition temperature of the CMC/PNIPAM is measured by a differential scanning calorimeter to be 30.8 ℃, and the solar modulation capacity of the thermochromic window is measured and calculated to be about 60% by an ultraviolet/visible light/near infrared spectrophotometer at the temperature of 30.8 ℃; by constant temperature heating, CMC/PNIPAM was observed to maintain dispersion stability after being placed in an environment of 60 deg.C for 7 days.

Example 3: preparation of cellulose-reinforced PNIPAM-based thermochromic windows

(1) With N, N^＇-dipropylacrylamide is used as a cross-linking agent, ammonium persulfate is used as a catalyst, and PNIPAM is synthesized by a soap-free emulsion polymerization method; preparing PNIPAM aqueous dispersion;

(2) preparing 0.04 g/mL CMC solution with the substitution degree of 1.5 and the molecular weight of 1000,000 g/mol;

(3) mixing the PNIPAM aqueous dispersion, the CMC solution and water to obtain the CMC/PNIPAM thermochromic composite material with the mass fraction of the CMC being 3% and the mass fraction of the PNIPAM being 5%.

(4) And injecting the CMC/PNIPAM thermochromic composite material between double-layer glass with the interlayer thickness of 3mm, and sealing to obtain the thermochromic window.

The phase change temperature of the CMC/PNIPAM is measured to be 30 ℃ by a differential scanning calorimeter, and at the temperature of 30 ℃, the solar modulation capacity of the thermochromic window is measured and calculated to be about 80% by an ultraviolet/visible light/near infrared spectrophotometer; by constant temperature heating, CMC/PNIPAM was observed to maintain dispersion stability after being placed in an environment of 60 deg.C for 7 days.

Example 4: preparation of cellulose-reinforced HPC-based thermochromic windows

(1) Preparing HPC into an aqueous dispersion;

(2) preparing 0.04 g/mL CMC solution with the substitution degree of 1 and the molecular weight of 90,000 g/mol;

(3) and mixing the HPC aqueous dispersion, the CMC solution and water to obtain the CMC/HPC thermochromic composite material with the mass fraction of 0.005% of CMC and 0.5% of HPC.

(4) And injecting the CMC/HPC thermochromic composite material between double-layer glass with the thickness of an interlayer of 0.9mm, and sealing to obtain the thermochromic window.

Measuring the phase change temperature of the CMC/HPC by using a thermocouple to be 39 ℃, and measuring and calculating the solar modulation capacity of the thermochromic window to be 41% by using an ultraviolet/visible light/near infrared spectrophotometer at 39 ℃; by the constant-temperature heating method, it was observed that the dispersion stability of CMC/PNIPAM slightly decreased after being left at 60 ℃ for 7 days.

Example 5: preparation of cellulose-reinforced HPC-based thermochromic windows

(1) Preparing HPC into an aqueous dispersion;

(2) preparing 0.04 g/mL CMC solution with the substitution degree of 0.8 and the molecular weight of 100,000 g/mol;

(3) and mixing the HPC aqueous dispersion, the CMC solution and water to obtain the CMC/HPC thermochromic composite material with 1% of CMC and 1% of HPC by mass.

(4) And injecting the CMC/HPC thermochromic composite material between double-layer glass with the interlayer thickness of 2mm, and sealing to obtain the thermochromic window.

Measuring the phase change temperature of the CMC/HPC by using a thermocouple to be 37 ℃, and measuring and calculating the solar modulation capacity of the thermochromic window to be about 52% by using an ultraviolet/visible light/near infrared spectrophotometer at the temperature of 33 ℃; by constant temperature heating, CMC/PNIPAM was observed to maintain dispersion stability after being placed in an environment of 60 deg.C for 7 days.

Example 6: preparation of cellulose-reinforced HPC-based thermochromic windows

(1) Preparing HPC into an aqueous dispersion;

(2) preparing 0.04 g/mL CMC solution with the substitution degree of 1.5 and the molecular weight of 1000,000 g/mol;

(3) and mixing the HPC aqueous dispersion, the CMC solution and water to obtain the CMC/HPC thermochromic composite material with the mass fraction of 3 percent of CMC and 1.5 percent of HPC.

(4) And injecting the CMC/HPC thermochromic composite material between double-layer glass with the thickness of an interlayer of 5mm, and sealing to obtain the thermochromic window.

Measuring the phase change temperature of the CMC/HPC by using a thermocouple to be 33 ℃, and measuring and calculating the solar modulation capacity of the thermochromic window to be about 57% by using an ultraviolet/visible light/near infrared spectrophotometer at the temperature of 33 ℃; by constant temperature heating, CMC/PNIPAM was observed to maintain dispersion stability after being placed in an environment of 60 deg.C for 7 days.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.