Preparation method of ultraviolet-shielding thermochromic intelligent window

Abstract

The invention discloses a preparation method of an ultraviolet-shielding thermochromic intelligent window, and belongs to the field of intelligent windows. The problems that an existing HPC-based thermochromic intelligent window is high in response temperature and poor in ultraviolet shielding performance are solved. The method comprises the following steps: 1, preparing HPC hydrogel by an ultraviolet induced polymerization method; 2, preparing iron ion doped HPC hydrogel by an impregnation method; and 3, constructing the thermochromic intelligent window. The preparation method is used for preparing the thermochromic intelligent window with the ultraviolet shielding function.

Description

Technical Field

[0001] This invention belongs to the field of smart windows. Background Technology

[0002] Smart windows, acting as the "intelligent skin" of building envelopes, can dynamically manage solar radiation, thereby significantly reducing heating and cooling energy consumption. Among various smart window technologies, thermochromic smart windows demonstrate enormous application potential due to their core advantages of automatically responding to changes in ambient temperature and requiring no additional energy supply. Furthermore, ultraviolet light (wavelength range of 200-400nm) is a major factor causing aging and fading of indoor furniture, decorations, and artwork; long-term exposure also affects human health. Therefore, constructing smart windows with ultraviolet shielding capabilities is crucial for a comfortable living environment.

[0003] Hydroxypropyl cellulose (HPC) is a bio-based polymer. HPC hydrogels exhibit unique thermochromic properties: at lower temperatures, HPC molecular chains form hydrogen bonds with water molecules and hydrate and dissolve, resulting in a transparent, homogeneous system with high transmittance of visible light. When the temperature rises above its lowest critical eutectic temperature (LCST), the hydrogen bonds are broken, the molecular chains dehydrate and shrink, leading to phase separation and a cloudy system that strongly scatters visible light. This reversible "low-temperature transparency - high-temperature turbidity" property makes it suitable for constructing thermochromic smart windows. When summer temperatures reach the phase transition temperature of the HPC hydrogel, the visible light transmittance of the smart window decreases, inhibiting a continuous rise in indoor temperature. However, the LCST value of HPC hydrogel is approximately 45°C, resulting in an excessively high response temperature for the smart window, severely limiting its application scenarios. Furthermore, HPC hydrogel has poor shielding ability against ultraviolet light, further restricting its development and application. Summary of the Invention

[0004] This invention aims to address the problems of high response temperature and poor ultraviolet shielding performance of existing HPC-based thermochromic smart windows, and thus provides a method for preparing an ultraviolet-shielded thermochromic smart window.

[0005] A method for preparing a thermochromic smart window with ultraviolet shielding, comprising the following steps:

[0006] I. Preparation of HPC hydrogels by UV-induced polymerization:

[0007] Hydroxypropyl cellulose was added to deionized water and stirred until completely dissolved to obtain a precursor solution. Polyacrylamide, N,N'-methylenebisacrylamide and UV photoinitiator were added to the precursor solution and stirred evenly at room temperature. Then, the solution was allowed to stand to defoam and finally placed in a mold and subjected to UV polymerization to obtain HPC hydrogel.

[0008] II. Preparation of iron-doped HPC hydrogels by impregnation method:

[0009] HPC hydrogel was immersed in a FeCl3 / FeCl2 mixed solution and allowed to stand at low temperature, then washed to obtain iron ion-doped HPC hydrogel.

[0010] III. Construction of Thermochromic Smart Window:

[0011] Iron-doped HPC hydrogel was placed between two pieces of indium tin oxide conductive glass to construct a sandwich structure, and then the sides were sealed to obtain a thermochromic smart window with UV shielding.

[0012] The beneficial effects of this invention are:

[0013] (1) This invention proposes a method for preparing a thermochromic smart window with ultraviolet shielding. When ultraviolet light irradiates the smart window, the electrons of iron ions will absorb photon energy and undergo a transition, converting the ultraviolet light energy into the excitation energy of their own electrons, thereby reducing the transmittance of ultraviolet light. Therefore, the smart window achieves a 100% blocking rate for ultraviolet light.

[0014] (2) FeCl3 and FeCl2 ionize in water to form Fe 3+ Fe 2+ Cl - Equally hydrated ions compete with HPC for water molecules, disrupting the hydrogen bond network of HPC and making the HPC molecular chains more prone to dehydration and shrinkage, thus causing a phase transition at a lower temperature and reducing the color-changing temperature of the thermochromic smart window to the range of 30℃~35℃. Attached Figure Description

[0015] Figure 1 The transmittance spectrum of the ultraviolet-shielded thermochromic smart window prepared in Example 1 in the wavelength range of 200nm~800nm;

[0016] Figure 2 Optical photographs of the thermochromic smart window prepared in the comparative experiment at low and high temperatures;

[0017] Figure 3 Optical photographs of the UV-shielded thermochromic smart window prepared in Example 1 at low and high temperatures;

[0018] Figure 4 The visible light transmission spectra of the ultraviolet-shielded thermochromic smart window prepared in Example 1 at low and high temperatures. Detailed Implementation

[0019] Specific Implementation Method 1: This implementation method describes a method for preparing a thermochromic smart window with ultraviolet shielding, which is carried out according to the following steps:

[0020] I. Preparation of HPC hydrogels by UV-induced polymerization:

[0021] Hydroxypropyl cellulose was added to deionized water and stirred until completely dissolved to obtain a precursor solution. Polyacrylamide, N,N'-methylenebisacrylamide and UV photoinitiator were added to the precursor solution and stirred evenly at room temperature. Then, the solution was allowed to stand to defoam and finally placed in a mold and subjected to UV polymerization to obtain HPC hydrogel.

[0022] II. Preparation of iron-doped HPC hydrogels by impregnation method:

[0023] HPC hydrogel was immersed in a FeCl3 / FeCl2 mixed solution and allowed to stand at low temperature, then washed to obtain iron ion-doped HPC hydrogel.

[0024] III. Construction of Thermochromic Smart Window:

[0025] Iron-doped HPC hydrogel was placed between two pieces of indium tin oxide conductive glass to construct a sandwich structure, and then the sides were sealed to obtain a thermochromic smart window with UV shielding.

[0026] The beneficial effects of this embodiment are:

[0027] (1) This embodiment proposes a method for preparing a thermochromic smart window with ultraviolet shielding. When ultraviolet light irradiates the smart window, the electrons of the iron ions will absorb the photon energy and undergo a transition, converting the ultraviolet light energy into the excitation energy of their own electrons, thereby reducing the transmittance of ultraviolet light. Therefore, the blocking rate of the smart window against ultraviolet light reaches 100%.

[0028] (2) FeCl3 and FeCl2 ionize in water to form Fe 3+ Fe 2+ Cl - Equally hydrated ions compete with HPC for water molecules, disrupting the hydrogen bond network of HPC and making the HPC molecular chains more prone to dehydration and shrinkage, thus causing a phase transition at a lower temperature and reducing the color-changing temperature of the thermochromic smart window to the range of 30℃~35℃.

[0029] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the degree of substitution of hydroxypropoxy groups in the hydroxypropyl cellulose mentioned in step one is >16%; and the ultraviolet photoinitiator mentioned in step one is ultraviolet photoinitiator 2959. Everything else is the same as in Specific Implementation Method One.

[0030] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in the following ways: the mass ratio of hydroxypropyl cellulose to deionized water in step one is 1:(15~20); the mass ratio of hydroxypropyl cellulose to polyacrylamide in step one is 1:(1~2); the mass ratio of hydroxypropyl cellulose to N,N'-methylenebisacrylamide in step one is 1:(0.004~0.01); and the mass ratio of hydroxypropyl cellulose to ultraviolet photoinitiator in step one is 1:(0.005~0.01). Everything else is the same as in Specific Implementation Method One or Two.

[0031] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: in step one, hydroxypropyl cellulose is added to deionized water and stirred at a stirring speed of 400 r / min to 500 r / min for 2 to 3 hours until completely dissolved to obtain a precursor solution. Polyacrylamide, N,N'-methylenebisacrylamide, and a UV photoinitiator are added to the precursor solution and stirred at room temperature for 4 to 6 hours. Then, the solution is allowed to stand for defoaming for 2 to 5 hours. Finally, the solution is placed in a mold and irradiated with UV light at a power of 100 W to 200 W for 3 to 5 minutes to obtain the HPC hydrogel. Everything else is the same as in Specific Implementation Methods One to Three.

[0032] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the molar ratio of FeCl3 to FeCl2 in the FeCl3 / FeCl2 mixed solution described in step two is 1:(1~1.5). Everything else is the same as in Specific Implementation Methods One to Four.

[0033] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the concentration of FeCl3 in the FeCl3 / FeCl2 mixed solution described in step two is 0.1 mol / L to 0.6 mol / L. Everything else is the same as in Specific Implementation Methods One to Five.

[0034] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: in step two, the HPC hydrogel is immersed in a FeCl3 / FeCl2 mixed solution and allowed to stand at a low temperature of -4℃ to -8℃ for 20 to 40 minutes, followed by washing with deionized water to obtain an iron-doped HPC hydrogel. Everything else is the same as in Specific Implementation Methods One to Six.

[0035] Specific Implementation Method Eight: This implementation method differs from one of Specific Implementation Methods One to Seven in that the resistance of the indium tin oxide conductive glass described in step three is 10Ω to 50Ω. Everything else is the same as in Specific Implementation Methods One to Seven.

[0036] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the side sealing in step three specifically involves using 3M tape placed between two pieces of indium tin oxide conductive glass for side sealing. The thickness of the tape is 1mm to 3mm. Everything else is the same as in Specific Implementation Methods One to Eight.

[0037] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the thickness of the iron-doped HPC hydrogel in the UV-shielded thermochromic smart window described in step three is the same as the thickness of the adhesive tape. Everything else is the same as in Specific Implementation Methods One to Nine.

[0038] The beneficial effects of the present invention are verified using the following embodiments:

[0039] Example 1:

[0040] A method for preparing a thermochromic smart window with ultraviolet shielding, comprising the following steps:

[0041] I. Preparation of HPC hydrogels by UV-induced polymerization:

[0042] Hydroxypropyl cellulose was added to deionized water and stirred for 3 hours at a stirring speed of 500 r / min until completely dissolved to obtain a precursor solution. Polyacrylamide, N,N'-methylenebisacrylamide and UV photoinitiator were added to the precursor solution and stirred at room temperature for 5 hours. Then, the mixture was allowed to stand for 4 hours to defoam. Finally, it was placed in a mold and irradiated with UV light at a power of 150W for 3 minutes to obtain HPC hydrogel.

[0043] The degree of substitution of hydroxypropoxy groups in the hydroxypropyl cellulose is 80%; the ultraviolet photoinitiator is ultraviolet photoinitiator 2959;

[0044] The mass ratio of hydroxypropyl cellulose to deionized water is 1:15; the mass ratio of hydroxypropyl cellulose to polyacrylamide is 1:1.5; the mass ratio of hydroxypropyl cellulose to N,N'-methylenebisacrylamide is 1:0.008; and the mass ratio of hydroxypropyl cellulose to ultraviolet photoinitiator is 1:0.009.

[0045] II. Preparation of iron-doped HPC hydrogels by impregnation method:

[0046] HPC hydrogel was immersed in a FeCl3 / FeCl2 mixed solution, allowed to stand at -4℃ for 30 min, and then washed with deionized water to obtain iron ion-doped HPC hydrogel.

[0047] The molar ratio of FeCl3 to FeCl2 in the FeCl3 / FeCl2 mixed solution is 1:1; the concentration of FeCl3 in the FeCl3 / FeCl2 mixed solution is 0.5 mol / L.

[0048] III. Construction of Thermochromic Smart Window:

[0049] Iron-doped HPC hydrogel was placed between two pieces of indium tin oxide conductive glass to construct a sandwich structure. Then, 3M tape was placed between the two pieces of indium tin oxide conductive glass to seal the sides, resulting in a UV-shielded thermochromic smart window.

[0050] The resistance of the indium tin oxide conductive glass is 20Ω;

[0051] The thickness of the tape is 2mm;

[0052] The thickness of the iron-doped HPC hydrogel in the ultraviolet-shielded thermochromic smart window is 2 mm.

[0053] Comparative Experiment: This comparative experiment differs from Example 1 in that step two is omitted. Everything else is the same as in Example 1.

[0054] Figure 1 The transmittance spectrum of the thermochromic smart window for ultraviolet shielding prepared in Example 1 is shown in the wavelength range of 200nm to 800nm. As can be seen from the figure, at room temperature, the smart window can completely shield ultraviolet light in the wavelength range of 200nm to 400nm, with a shielding efficiency of up to 100%.

[0055] Figure 2 Optical photographs of the thermochromic smart window prepared in the comparative experiment at low and high temperatures are shown in the figure. As can be seen from the figure, the smart window changes from a transparent state (10℃) to an opaque state at 45℃.

[0056] Figure 3 The images show optical photographs of the UV-shielded thermochromic smart window prepared in Example 1 at low and high temperatures. As can be seen from the images, the smart window changes color at 32°C, changing from a transparent state (10°C) to an opaque state. At the same time, the presence of iron ions makes the smart window appear yellow.

[0057] Figure 4 The visible light transmittance spectra of the UV-shielded thermochromic smart window prepared in Example 1 at low and high temperatures are shown in the figure. As can be seen from the figure, in the wavelength range of 400nm~800nm, the visible light transmittance of the smart window is 75% at low temperature (10℃) and 9% at high temperature (32℃), with a visible light transmittance modulation amplitude of 66%.

Claims

1. A method for preparing a thermochromic smart window with ultraviolet shielding, characterized in that... It is done in the following steps: I. Preparation of HPC hydrogels by UV-induced polymerization: Hydroxypropyl cellulose was added to deionized water and stirred until completely dissolved to obtain a precursor solution. Polyacrylamide, N,N'-methylenebisacrylamide and UV photoinitiator were added to the precursor solution and stirred evenly at room temperature. Then, the solution was allowed to stand to defoam and finally placed in a mold and subjected to UV polymerization to obtain HPC hydrogel. II. Preparation of iron-doped HPC hydrogels by impregnation method: HPC hydrogel was immersed in a FeCl3 / FeCl2 mixed solution and allowed to stand at low temperature, then washed to obtain iron ion-doped HPC hydrogel. III. Construction of Thermochromic Smart Window: Iron-doped HPC hydrogel was placed between two pieces of indium tin oxide conductive glass to construct a sandwich structure, and then the sides were sealed to obtain a thermochromic smart window with UV shielding.

2. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 1, characterized in that... The degree of substitution of hydroxypropoxy groups in the hydroxypropyl cellulose mentioned in step one is >16%; the ultraviolet photoinitiator mentioned in step one is ultraviolet photoinitiator 2959.

3. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 1, characterized in that... The mass ratio of hydroxypropyl cellulose to deionized water in step one is 1:(15~20); the mass ratio of hydroxypropyl cellulose to polyacrylamide in step one is 1:(1~2); the mass ratio of hydroxypropyl cellulose to N,N'-methylenebisacrylamide in step one is 1:(0.004~0.01); and the mass ratio of hydroxypropyl cellulose to ultraviolet photoinitiator in step one is 1:(0.005~0.01).

4. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 1, characterized in that... In step one, hydroxypropyl cellulose is added to deionized water and stirred for 2-3 hours at a stirring speed of 400-500 rpm until completely dissolved to obtain a precursor solution. Polyacrylamide, N,N'-methylenebisacrylamide and UV photoinitiator are added to the precursor solution and stirred at room temperature for 4-6 hours. Then, the mixture is allowed to stand for 2-5 hours to defoam. Finally, it is placed in a mold and irradiated with UV light for 3-5 minutes at a power of 100-200W to obtain HPC hydrogel.

5. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 1, characterized in that... In step two, the molar ratio of FeCl3 to FeCl2 in the FeCl3 / FeCl2 mixed solution is 1:(1~1.5).

6. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 1, characterized in that... The concentration of FeCl3 in the FeCl3 / FeCl2 mixed solution mentioned in step two is 0.1 mol / L to 0.6 mol / L.

7. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 1, characterized in that... In step two, the HPC hydrogel is immersed in a FeCl3 / FeCl2 mixed solution and allowed to stand at a low temperature of -4℃ to -8℃ for 20 to 40 minutes. Then it is washed with deionized water to obtain iron ion-doped HPC hydrogel.

8. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 1, characterized in that... The resistance of the indium tin oxide conductive glass mentioned in step three is 10Ω~50Ω.

9. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 1, characterized in that... The side sealing mentioned in step three specifically involves using 3M tape placed between two pieces of indium tin oxide conductive glass for side sealing. The thickness of the tape is 1mm to 3mm.

10. The method for preparing a thermochromic smart window with ultraviolet shielding according to claim 9, characterized in that... In step three, the thickness of the iron-doped HPC hydrogel in the UV-shielded thermochromic smart window is the same as the thickness of the tape.

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