A method for preparing a double-layer film with heat-curling and healing properties

Abstract

The application relates to a preparation method of a double-layer film with heat-curling and healing characteristics, characterized in that water-soluble micro-nano particles and a polymer with a high thermal expansion coefficient are uniformly mixed to form a colloidal mixture I, a polymer hard film I is formed by silk screen printing and heating curing; polycaprolactone with low thermal expansion coefficient and low melting point is heated and melted, and thermochromic particles with low phase transition temperature are added to form a colloidal mixture II, a double-layer polymer hard film is formed on the surface of the polymer hard film I by silk screen printing and room temperature curing, and the prepared double-layer polymer hard film is soaked in hot water to form a double-layer polymer hard film with a porous structure in the lower layer. The application creates a preparation method of a double-layer film with heat-curling and healing characteristics, which not only provides a preparation method of an intelligent shrinkage double-layer film, but also endows the double-layer film with excellent self-healing performance, and guarantees the heat insulation and heat preservation characteristics of the double-layer film.

Description

Technical Field

[0001] This invention relates to a method for preparing a bilayer film, and more particularly to a method for preparing a bilayer film that combines heat-induced curling and healing properties, belonging to the field of composite material preparation technology. Background Technology

[0002] In agricultural greenhouses, unstable weather conditions significantly reduce the productivity of traditional farming and affect plant growth cycles. Double-layered greenhouses address this challenge by combining two layers of covering material: the outer layer protects the structure from extreme weather, while the inner layer focuses on retaining heat, thus maintaining a constant temperature within the greenhouse and creating an ideal microenvironment for plant growth. At night, the inner insulating covering plays a crucial role, retaining heat and protecting plants from cold. Because seedlings are extremely sensitive to temperature changes, both excessively high and low temperatures can adversely affect their growth. Therefore, the inner insulating covering in double-roofed greenhouses needs to be opened promptly during the day when temperatures rise to prevent overheating and damage to seedlings; and then covered again at night when temperatures drop to maintain a suitable growth temperature. Currently, the opening and closing of the inner insulating covering in large double-layered greenhouses is mainly done manually. This method is not only labor-intensive but also slow, especially during sudden climate changes. Delayed operation can lead to film damage and temperature imbalances within the greenhouse, affecting the healthy growth of plants. Therefore, the agricultural sector urgently needs a composite film capable of intelligently monitoring temperature changes within greenhouses and automatically healing and adjusting the insulating covering to achieve precise temperature control, ensure plants grow in optimal conditions, and simultaneously reduce labor costs and improve agricultural productivity. Although the insulation effect and planting potential of double-layer greenhouses have been proven, existing technologies still need improvement in intelligent control of shrinkage and healing insulation. Summary of the Invention

[0003] This invention aims to create a green, energy-saving, and heat-insulating double-layer film material to solve the problem that unstable climate conditions significantly reduce the production efficiency of traditional farming and affect the healthy growth of plants. It provides a method for preparing a double-layer film that has both heat-induced curling and healing properties.

[0004] The specific technical solution of the present invention is as follows.

[0005] A method for preparing a bilayer membrane with both heat-sensitive curling and healing properties includes the following steps:

[0006] (1) A colloidal mixture is formed by uniformly mixing water-soluble micro-nano particles and a polymer with a high coefficient of thermal expansion.

[0007] (2) The colloidal mixture obtained in (1) is screen printed to form a uniform polymer soft film, which is then heated and cured to form a polymer hard film.

[0008] (3) Polycaprolactone, which has both a low coefficient of thermal expansion and a low melting point, is heated and melted;

[0009] (4) Add thermochromic particles with low phase transition temperature to the melt obtained in (3) and mix them evenly to form colloidal mixture II;

[0010] (5) The colloidal mixture II obtained in (4) is screen printed on the surface of the polymer hard film I obtained in (2) to form a uniform polymer soft film II. Then, it is cured at room temperature for 30 min to form a double-layer polymer hard film with polymer hard film I as the lower layer and polymer hard film II as the upper layer.

[0011] (6) The double-layer polymer hard membrane prepared in (5) is immersed in hot water. The water-soluble micro-nano particles in polymer hard membrane 1 dissolve in hot water, and polymer hard membrane 1 becomes a porous structure, thus forming a double-layer polymer hard membrane with a porous structure polymer hard membrane 1 on the bottom and a polymer hard membrane 2 on the top.

[0012] The photothermal effect caused by the transformation of the polymer hard film II to black upon heating accelerates the difference in thermal expansion between the upper and lower polymer hard films, causing the double film to shrink and curl. When the polymer hard film II cools down and becomes transparent again, the photothermal effect disappears, reducing the difference in thermal expansion between the upper and lower polymer hard films and causing the double film to return to flatness. Under the accelerated melting of the low-melting-point polycaprolactone component in the polymer hard film II by photothermal effect and the extrusion pressure of the double film shrinking and curling, the damaged double polymer hard film heals rapidly.

[0013] The water-soluble micro / nano particles are sodium chloride particles or glucose particles at the micrometer or nanometer scale.

[0014] The polymer with a high coefficient of thermal expansion is polydimethylsiloxane or ethylene-vinyl acetate copolymer.

[0015] The mass ratio of the water-soluble micro / nano particles to the polymer with a high coefficient of thermal expansion is 1.25:1.

[0016] The heating and curing temperature is 80 ℃-120 ℃, and the heating and curing time is 30 min.

[0017] The heating and melting temperature is 60 ℃-70 ℃, and the heating and melting time is 10 min.

[0018] The thermochromic particles with low phase transition temperature are commercially available reversible thermochromic PP / PE particles with a phase transition temperature of 10 ℃-30 ℃. They are transparent below the phase transition temperature and black above the phase transition temperature.

[0019] The mass ratio of polycaprolactone, which has both a low coefficient of thermal expansion and a low melting point, to thermochromic particles with a low phase transition temperature is 5:1.

[0020] The double-layer polymer hard membrane is immersed in hot water at a temperature of 40 ℃-50 ℃ for 60 h-72 h.

[0021] To better understand this technical solution, its core principles will now be explained in detail:

[0022] When the bilayer polymer hard film is heated to above the phase transition temperature of the thermochromic particles (low phase transition temperature), the second polymer hard film turns black. The photothermal effect caused by the black color causes the second polymer hard film to continue to heat up under light. At the same time, since the upper polymer hard film contains a low coefficient of thermal expansion polycaprolactone component and the lower polymer hard film contains a high coefficient of thermal expansion polymer component, the difference in thermal expansion between the two polymer hard films increases, causing the bilayer polymer hard film to shrink and curl towards the polymer hard film containing the low coefficient of thermal expansion polycaprolactone component. When the temperature of the bilayer polymer hard film drops below the phase transition temperature of the thermochromic particles (low phase transition temperature), the second polymer hard film returns to its transparent color, causing the photothermal effect to disappear. The difference in thermal expansion between the upper and lower polymer hard films decreases, causing the bilayer polymer hard film to return to its flatness. When the upper part of the double-layer polymer hard film, namely the second polymer hard film, is damaged, the second polymer hard film can turn black when heated to a temperature above the phase transition temperature of the thermochromic particles. The photothermal effect caused by the black color causes the second polymer hard film to continue to heat up under light. When the temperature of the second polymer hard film is higher than the melting point of the low-melting-point polycaprolactone component in the second polymer hard film, the low-melting-point polycaprolactone component in the damaged part of the second polymer hard film melts and fills the damaged part. At the same time, due to the increase in the difference in the degree of thermal expansion between the upper and lower polymer hard films, the double polymer hard film shrinks and curls and is squeezed towards the second polymer hard film. Therefore, the damaged part of the second polymer hard film can heal quickly.

[0023] The beneficial effects of this invention are as follows: (1) Energy-free photothermal effect regulates the contraction and expansion of the double-layer film. When the temperature rises, the polymer hard film layer containing low phase change temperature thermochromic particle components can quickly sense the rise in external temperature and turn black, generating photothermal effect to accelerate the temperature rise of the film layer. The difference in thermal expansion coefficient between the two polymer hard films causes the double-layer film to contract and curl. When the temperature drops, the polymer hard film layer containing low phase change temperature thermochromic particle components can quickly sense the drop in external temperature and turn transparent, causing the photothermal effect to disappear. The difference in thermal expansion coefficient between the two polymer hard films induces asymmetric contraction, causing the double-layer film to return to a flat state, thus realizing green and intelligent contraction and expansion without energy consumption. (2) Photothermal effect and contraction and curling pressure jointly drive the damaged parts of the double-layer film to quickly self-heal. When the upper part of the double-layer polymer hard film is damaged and exposed to sunlight, the thermochromic particles turn black and convert light energy into heat energy, rapidly heating the upper polymer hard film and melting its low-melting-point polycaprolactone component to fill the damaged area. At the same time, under the action of the shrinkage and curling extrusion pressure of the double-layer polymer hard film, the damaged area is rapidly fused together, which greatly improves the service life of the double-layer film. (3) The double-layer film blocks the outdoor cold air and retains the indoor heat. In low-temperature environments or at night, the dense upper film of the double-layer polymer hard film blocks the entry of cold air, while the porous inner film plays the inherent heat insulation role of the porous structure, which helps to retain heat in the greenhouse and protects plants from cold. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the preparation process and operation of a bilayer membrane that combines heat-induced curling and healing properties. Detailed Implementation

[0025] Example 1: A method for preparing a bilayer film with both heat-sensitive curling and healing properties, such as... Figure 1 As shown, it includes the following steps:

[0026] Step 1: Water-soluble micron-sized sodium chloride particles and polydimethylsiloxane with a high coefficient of thermal expansion are uniformly mixed at a mass ratio of 1.25:1 to form a colloidal mixture.

[0027] Step 2: The colloidal mixture obtained in Step 1 is screen printed to form a uniform polymer soft film, which is then heated to 80 ℃ and kept at that temperature for 30 min to form a polymer hard film.

[0028] Step 3: Heat polycaprolactone, which has both a low coefficient of thermal expansion and a low melting point, to 60 °C and hold for 10 min to melt it.

[0029] Step 4: Add commercially available reversible thermochromic PP / PE particles with a phase change temperature of 10 °C to the melt obtained in step 3 at a mass ratio of polycaprolactone to thermochromic particles of 5:1 and mix them evenly to form colloidal mixture 2.

[0030] Step 5: The colloidal mixture 2 obtained in step 4 is screen-printed onto the surface of the polymer hard film 1 obtained in step 2 to form a uniform polymer soft film 2. Then, it is cured at room temperature for 30 minutes to form a double-layer polymer hard film with polymer hard film 1 as the lower layer and polymer hard film 2 as the upper layer.

[0031] Step six: Immerse the double-layer polymer hard membrane obtained in step five in hot water at 40 °C for 72 h. The water-soluble sodium chloride particles in polymer hard membrane one dissolve in the hot water, and polymer hard membrane one becomes a porous structure, thus forming a double-layer polymer hard membrane with a porous structure polymer hard membrane one on the bottom and polymer hard membrane two on the top. When the bilayer polymer hard film is heated to above 10 °C, the second polymer hard film turns black. The photothermal effect caused by the black color causes the second polymer hard film to continue to heat up under light conditions. At the same time, since the upper polymer hard film contains a low coefficient of thermal expansion polycaprolactone component and the lower polymer hard film contains a high coefficient of thermal expansion polydimethylsiloxane component, the difference in thermal expansion between the two polymer hard films increases, causing the bilayer polymer hard film to shrink and curl towards the polymer hard film containing the low coefficient of thermal expansion polycaprolactone component. When the temperature of the bilayer polymer hard film drops below 10 °C, the second polymer hard film returns to its transparent color, causing the photothermal effect to disappear. The difference in thermal expansion between the upper and lower polymer hard films decreases, causing the bilayer polymer hard film to return to its flatness. When the upper part of the double-layer polymer hard film, namely the second polymer hard film, is damaged, the second polymer hard film can turn black when heated to above 10 ℃. The photothermal effect caused by the black color causes the second polymer hard film to continue to heat up under light. When the temperature of the second polymer hard film is higher than 60 ℃, the low melting point polycaprolactone component of the damaged part of the second polymer hard film melts and fills the damaged part. At the same time, due to the increase in the difference in the degree of thermal expansion between the upper and lower polymer hard films, the double-layer polymer hard film shrinks and curls and is squeezed towards the second polymer hard film. Therefore, the damaged part of the second polymer hard film can be quickly fused together.

[0032] Example 2: A method for preparing a bilayer film with both heat-sensitive curling and healing properties, such as... Figure 1 As shown, it includes the following steps:

[0033] Step 1: Water-soluble nanoscale glucose particles and ethylene-vinyl acetate copolymer with a high coefficient of thermal expansion are uniformly mixed at a mass ratio of 1.25:1 to form a colloidal mixture.

[0034] Step 2: The colloidal mixture obtained in Step 1 is screen-printed to form a uniform polymer soft film, which is then heated and cured at 120 °C for 30 min to form a polymer hard film.

[0035] Step 3: Heat polycaprolactone, which has both a low coefficient of thermal expansion and a low melting point, at 70 °C for 10 min to melt it.

[0036] Step 4: Add commercially available reversible thermochromic PP / PE particles with a phase change temperature of 30 °C to the melt obtained in step 3 at a mass ratio of polycaprolactone to thermochromic particles of 5:1 and mix them evenly to form colloidal mixture 2.

[0037] Step 5: The colloidal mixture 2 obtained in step 4 is screen-printed onto the surface of the polymer hard film 1 obtained in step 2 to form a uniform polymer soft film 2. Then, it is cured at room temperature for 30 minutes to form a double-layer polymer hard film with polymer hard film 1 as the lower layer and polymer hard film 2 as the upper layer.

[0038] Step six: Immerse the double-layer polymer hard membrane obtained in step five in hot water at 50 °C for 60 h. The water-soluble glucose particles in polymer hard membrane one dissolve in the hot water, and polymer hard membrane one becomes a porous structure, thus forming a double-layer polymer hard membrane with a porous structure polymer hard membrane one on the bottom and polymer hard membrane two on the top. When the bilayer polymer hard film is heated to above 30 ℃, the second polymer hard film turns black. The photothermal effect caused by the black color causes the second polymer hard film to continue to heat up under light conditions. At the same time, since the upper polymer hard film contains a polycaprolactone component with a low coefficient of thermal expansion and the lower polymer hard film contains an ethylene-vinyl acetate copolymer component with a high coefficient of thermal expansion, the difference in thermal expansion between the upper and lower polymer hard films increases, causing the bilayer polymer hard film to shrink and curl towards the polymer hard film containing the polycaprolactone component with a low coefficient of thermal expansion. When the temperature of the bilayer polymer hard film drops below 30 ℃, the second polymer hard film returns to its transparent color, causing the photothermal effect to disappear. The difference in thermal expansion between the upper and lower polymer hard films decreases, causing the bilayer polymer hard film to return to its flatness. When the upper part of the double-layer polymer hard film, namely the second polymer hard film, is damaged, the second polymer hard film can turn black when heated to above 30 ℃. The photothermal effect caused by the black color causes the second polymer hard film to continue to heat up under light. When the temperature of the second polymer hard film is higher than 70 ℃, the low melting point polycaprolactone component of the damaged part of the second polymer hard film melts and fills the damaged part. At the same time, due to the increase in the difference in the degree of thermal expansion between the upper and lower polymer hard films, the double-layer polymer hard film shrinks and curls and is squeezed towards the second polymer hard film. Therefore, the damaged part of the second polymer hard film can be quickly fused together.

[0039] Example 3: A method for preparing a bilayer film with both heat-sensitive curling and healing properties, such as... Figure 1 As shown, it includes the following steps:

[0040] Step 1: Water-soluble nanoscale glucose particles and polydimethylsiloxane copolymer with a high coefficient of thermal expansion are uniformly mixed at a mass ratio of 1.25:1 to form a colloidal mixture.

[0041] Step 2: The colloidal mixture obtained in Step 1 is screen printed to form a uniform polymer soft film, which is then heated to 100 ℃ and kept at that temperature for 30 min to form a polymer hard film.

[0042] Step 3: Melt polycaprolactone, which has both a low coefficient of thermal expansion and a low melting point, at 65 °C for 10 min;

[0043] Step 4: Add commercially available reversible thermochromic PP / PE particles with a phase change temperature of 20 °C to the melt obtained in step 3 at a mass ratio of polycaprolactone to thermochromic particles of 5:1 and mix them evenly to form colloidal mixture 2.

[0044] Step 5: The colloidal mixture 2 obtained in step 4 is screen-printed onto the surface of the polymer hard film 1 obtained in step 2 to form a uniform polymer soft film 2. Then, it is cured at room temperature for 30 minutes to form a double-layer polymer hard film with polymer hard film 1 as the lower layer and polymer hard film 2 as the upper layer.

[0045] Step six: Immerse the double-layer polymer hard membrane obtained in step five in hot water at 45 ℃ for 66 h. The water-soluble glucose particles in polymer hard membrane one dissolve in the hot water, and polymer hard membrane one becomes a porous structure, thus forming a double-layer polymer hard membrane with a porous structure polymer hard membrane one on the bottom and polymer hard membrane two on the top. When the bilayer polymer hard film is heated to above 20 °C, the second polymer hard film turns black. The photothermal effect caused by the black color causes the second polymer hard film to continue to heat up under light. At the same time, since the upper polymer hard film contains a low coefficient of thermal expansion polycaprolactone component and the lower polymer hard film contains a high coefficient of thermal expansion polydimethylsiloxane component, the difference in thermal expansion between the two polymer hard films increases, causing the bilayer polymer hard film to shrink and curl towards the polymer hard film containing the low coefficient of thermal expansion polycaprolactone component. When the temperature of the bilayer polymer hard film drops below 20 °C, the second polymer hard film returns to its transparent color, causing the photothermal effect to disappear. The difference in thermal expansion between the upper and lower polymer hard films decreases, causing the bilayer polymer hard film to return to its flatness. When the upper part of the double-layer polymer hard membrane, namely the second polymer hard membrane, is damaged, the second polymer hard membrane turns black when heated to above 20 ℃. The photothermal effect caused by the black color causes the second polymer hard membrane to continue to heat up under light. When the temperature of the second polymer hard membrane is higher than 65 ℃, the low-melting-point polycaprolactone component of the damaged part of the second polymer hard membrane melts and fills the damaged part. At the same time, due to the increase in the difference in the degree of thermal expansion between the upper and lower polymer hard membranes, the double-layer polymer hard membrane shrinks and curls and is squeezed towards the second polymer hard membrane. Therefore, the damaged part of the second polymer hard membrane can heal quickly.

[0046] The foregoing has described in detail representative embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a bilayer film possessing both heat-sensitive curling and healing properties, characterized in that, Includes the following steps: (1) A colloidal mixture is formed by uniformly mixing water-soluble micro-nano particles and a polymer with a high coefficient of thermal expansion. (2) The colloidal mixture obtained in (1) is screen printed to form a uniform polymer soft film, which is then heated and cured to form a polymer hard film. (3) Heating and melting polycaprolactone, which has both a low coefficient of thermal expansion and a low melting point; (4) Add thermochromic particles with low phase transition temperature to the melt obtained in (3) and mix them evenly to form colloidal mixture II; (5) The colloidal mixture II obtained in (4) is screen printed on the surface of the polymer hard film I obtained in (2) to form a uniform polymer soft film II. Then, it is cured at room temperature for 30 min to form a double-layer polymer hard film with polymer hard film I as the lower layer and polymer hard film II as the upper layer. (6) The double-layer polymer hard membrane prepared in (5) is immersed in hot water. The water-soluble micro-nano particles in polymer hard membrane 1 dissolve in hot water, and polymer hard membrane 1 becomes a porous structure, thus forming a double-layer polymer hard membrane with a porous structure polymer hard membrane 1 on the bottom and a polymer hard membrane 2 on the top. The photothermal effect caused by the transformation of the polymer hard film II to black upon heating accelerates the difference in thermal expansion between the upper and lower polymer hard films, causing the double film to shrink and curl. When the polymer hard film II cools down and becomes transparent again, the photothermal effect disappears, reducing the difference in thermal expansion between the upper and lower polymer hard films and causing the double film to return to flatness. Under the accelerated melting of the low-melting-point polycaprolactone component in the polymer hard film II by photothermal effect and the extrusion pressure of the double film shrinking and curling, the damaged double polymer hard film heals rapidly.

2. The method for preparing a bilayer film with both heat-sensitive curling and healing properties according to claim 1, characterized in that, The water-soluble micro / nano particles are sodium chloride particles or glucose particles at the micrometer or nanometer scale.

3. The method for preparing a bilayer film with both heat-sensitive curling and healing properties according to claim 1, characterized in that, The polymer with a high coefficient of thermal expansion is polydimethylsiloxane or ethylene-vinyl acetate copolymer.

4. The method for preparing a bilayer film with both heat-sensitive curling and healing properties according to claim 1, characterized in that, The mass ratio of the water-soluble micro / nano particles to the polymer with a high coefficient of thermal expansion is 1.25:

1.

5. The method for preparing a bilayer film with both heat-sensitive curling and healing properties according to claim 1, characterized in that, The heating and curing temperature is 80 ℃-120 ℃, and the heating and curing time is 30 min.

6. The method for preparing a bilayer film with both heat-sensitive curling and healing properties according to claim 1, characterized in that, The heating and melting temperature is 60 ℃-70 ℃, and the heating and melting time is 10 min.

7. The method for preparing a bilayer film with both heat-sensitive curling and healing properties according to claim 1, characterized in that, The thermochromic particles with low phase transition temperature are commercially available reversible thermochromic PP / PE particles with a phase transition temperature of 10℃-30℃. They are transparent below the phase transition temperature and black above the phase transition temperature.

8. The method for preparing a bilayer film with both heat-sensitive curling and healing properties according to claim 1, characterized in that, The mass ratio of polycaprolactone, which has both a low coefficient of thermal expansion and a low melting point, to thermochromic particles with a low phase transition temperature is 5:

1.

9. The method for preparing a bilayer film with both heat-sensitive curling and healing properties according to claim 1, characterized in that, The double-layer polymer hard membrane is immersed in hot water at a temperature of 40 ℃-50 ℃ for 60 h-72 h.

Images