High-strength polymethyl methacrylate photo-thermal nanofiber membrane, preparation method and application thereof

Abstract

The application provides a high-strength hydrophilic polymethyl methacrylate photo-thermal nanofiber membrane and a preparation method and application thereof, and particularly relates to the technical field of nanofiber membranes, and the preparation method is as follows: polymethyl methacrylate, dopamine hydrochloride and polyethylene imine with mass fractions of 8-20%wt, 0.1-0.6%wt and 0.25-1.2%wt respectively are added into an organic solvent, and heating and stirring are conducted to obtain an electrostatic spinning solution; the electrostatic spinning solution is electrostatically spun, and a polymethyl methacrylate photo-thermal nanofiber membrane is obtained after drying, wherein the positive voltage of electrostatic spinning is 12-20kV, the flow rate is 0.08-0.1mL / h, and the electrostatic spinning receiving distance is 14-20cm. The polymethyl methacrylate nanofiber membrane prepared by the application has high tensile strength, good hydrophilicity and photo-thermal function, and can be applied to the fields of indoor heating, military and civilian outdoor camping facilities, new solar self-heating thermal insulation clothes and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanofiber membranes, in particular to a high-strength hydrophilic polymethyl methacrylate photothermal nanofiber membrane and a preparation method and application thereof. BACKGROUND

[0002] In recent years, the industrialization of fibers has developed rapidly with the increasing international competition. Ordinary fibers have been unable to meet people's expectations and pursuit of higher quality of life, and people's attention to fibers has gradually shifted from ordinary fibers to new fibers with comfort functions, high added value and intelligence. Photothermal conversion fibers are a kind of functional fibers that can absorb certain light, especially near-infrared light, and generate heat through plasmonic resonance or energy transition to achieve local heating. Because they can convert near-infrared light into heat, they are very popular, and have broad application prospects in biological applications, external treatments and clothing, etc. It is of great significance to develop high-performance photothermal conversion fiber membrane materials. However, most photothermal fibers are prepared by using dry-wet spinning or electrospinning method, which is complicated, involves high-voltage electricity, has low safety factor and small production capacity. There is an urgent need for a method for preparing large-scale photothermal fibers with high conversion efficiency, which is simple and controllable in preparation process, has high tensile strength and is safer.

[0003] Polymethyl methacrylate (PMMA) has the advantages of easy solubility in organic solvents, non-toxicity, environmental protection, light weight, low cost, good chemical stability and excellent weather resistance, making it have a wide application prospect in medicine and health, building materials, mechanical processing, etc. Electrospinning is a special fiber manufacturing process in which polymer solution or melt is jetted in a strong electric field. The diameter of nanofibers prepared by electrospinning is usually between tens of nanometers and several microns, with a large specific surface area and porosity. The preparation process is efficient, fast and economical. With the rise and development of electrospinning technology, various natural polymers and synthetic polymers have been studied. As a synthetic polymer, polymethyl methacrylate has the characteristics of low toxicity, environmental protection and good biocompatibility. Polymethyl methacrylate nanofibers prepared by electrospinning have a wide application prospect. However, the hydrophilic performance and mechanical properties of polymethyl methacrylate composites are poor, so improving the hydrophilic performance and mechanical properties of nanofibers is a major problem faced by the application of polymethyl methacrylate electrospinning.

[0004] Polydopamine (PDA) is a kind of mussel-inspired biomimetic material, which has excellent adhesion, hydrophilicity and biocompatibility. It is widely used in many fields, including photothermal therapy, biological imaging and material surface functionalization carrier, and has attracted widespread attention. Polydopamine has high light absorption characteristics in the near-infrared spectrum, similar to the polymerization mechanism of natural melanin. Due to its unique photothermal properties, polydopamine has gradually become a hot material in the study of photothermal conversion.

[0005] By combining the excellent photothermal conversion performance of polydopamine with high polymer fibers, photothermal fibers can be prepared. In addition, PDA itself is a rigid polymer rich in benzene rings, which can be used as a reinforcing agent to fill the polymer, while also imparting the polymer with UV resistance, oxidation resistance, antibacterial properties, etc. However, there is still relatively little research on PDA-filled polymers, mainly because PDA's surface is rich in polar groups, which can easily agglomerate and not disperse well in the polymer matrix.

[0006] Patent CN115536887A discloses the use of dopamine hydrochloride and polyethyleneimine to form a super-hydrophilic coating on the surface of PMMA and other materials to improve the hydrophilicity of PMMA. This method is simple and easy to operate, but it has the defects of poor adhesion between the coating and the substrate, easy peeling off, and inability to improve the hardness of PMMA, limiting its application. SUMMARY

[0007] To solve the above technical problems, the present application provides a method for preparing a high-strength hydrophilic polymethyl methacrylate photothermal nanofiber membrane.

[0008] The technical solution of the present application is as follows:

[0009] A method for preparing a high-strength polymethyl methacrylate photothermal nanofiber membrane, comprising the following steps:

[0010] (1) Spinning solution preparation:

[0011] The polymethyl methacrylate raw material is placed in an oven and dried at a temperature of 50-70℃ for 6-8 hours. The dried polymethyl methacrylate, dopamine hydrochloride and polyethyleneimine are added to N-N dimethylformamide (DMF) and stirred at 57-60℃ for 6-10h to obtain an electrospinning solution. The mass fraction of polymethyl methacrylate is 8-16%, the mass fraction of dopamine hydrochloride is 0.1%-0.5%, and the mass fraction of polyethyleneimine is 0.25%-1%. In this process, due to the alkaline environment provided by polyethyleneimine, dopamine hydrochloride polymerizes in situ into polydopamine in the spinning solution.

[0012] (2) Electrospinning:

[0013] The electrospinning solution obtained in step (1) is transferred to a syringe for electrospinning to obtain a nanofiber membrane; then the obtained nanofiber membrane is transferred to a blast constant-temperature oven for drying at 40-60 DEG C for 6-12 h to remove the solvent. The electrospinning conditions are as follows: the electrospinning positive voltage is 12-20 kV, the flow rate is 0.08-0.1 mL / h, the electrospinning receiving distance is 10-20 cm, the indoor environmental humidity is 25-40%, and aluminum foil is used as the receiving substrate, to obtain a preparation method of the high-strength polymethyl methacrylate photo-thermal nanofiber membrane.

[0014] The high-strength polymethyl methacrylate photo-thermal nanofiber membrane is prepared by the above method.

[0015] The tensile strength of the high-strength polymethyl methacrylate photo-thermal nanofiber membrane is 0.28-0.48 MPa, and the temperature is increased from about 30 DEG C to 55-76 DEG C within 20 s under the irradiation of 1 solar light.

[0016] The contact angle of the high-strength polymethyl methacrylate photo-thermal nanofiber membrane is 65-76 DEG.

[0017] Preferably, the high-strength polymethyl methacrylate photo-thermal nanofiber membrane is applied to indoor heating, military and civilian outdoor camping facilities, and new solar self-heating thermal insulation clothing.

[0018] The present application has the following beneficial effects:

[0019] 1. The present application provides a method for preparing a high-strength hydrophilic polymethyl methacrylate nanofiber membrane with photo-thermal function by synergistic modification of polyethyleneimine and polydopamine. In the preparation process of the polymethyl methacrylate spinning solution, polyethyleneimine with hydrophilic hydroxyl groups and hydrochloric acid dopamine are added. The alkaline environment provided by polyethyleneimine is used to polymerize hydrochloric acid dopamine in situ to polydopamine in the spinning solution. Then the spinning stock solution is electrospun to prepare a high-strength hydrophilic polymethyl methacrylate nanofiber membrane with photo-thermal function, realizing one-step preparation of the spinning solution containing polydopamine and polyethyleneimine. Both polyethyleneimine and polydopamine contain a large number of hydrophilic groups, which can effectively improve the hydrophilicity of the polymethyl methacrylate nanofiber membrane, and at the same time, the strength of the polymethyl methacrylate nanofiber membrane with photo-thermal function is also improved.

[0020] 2. The scheme provided by the present application realizes the hydrophilization, strengthening and photo-thermal function of the polymethyl methacrylate nanofiber membrane in the preparation process of the spinning solution, avoids the complex reaction condition control requirements and the secondary influence on the structure of the nanofiber membrane of the surface grafting and other modification methods, and can greatly shorten the preparation process of the high-strength hydrophilic membrane.

[0021] 3.The application is prepared by compounding polydopamine with photo-thermal performance and general polymer nanofiber, and a photo-thermal nanofiber cloth capable of directly converting sunlight into heat energy with high efficiency is prepared, which can be used in indoor heating, military and civilian outdoor camping facilities, new solar self-heating thermal insulation clothing and other fields, saves energy consumption for winter heating, improves environmental comfort, and has great application prospect in the new generation of solar heating facilities.

[0022] 4.The application has the advantages of environmental friendliness, mild reaction conditions, simple preparation method, one-step modification and preparation, and good repeatability. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0024] Figure 1 The photos are of spinning solutions, wherein Figure A is the photo of the spinning solution of Example 1, Figure B is the photo of the spinning solution of Comparative Example 1, and Figure C is the photo of the spinning solution of Comparative Example 2.

[0025] Figure 2 The photos are of nanofiber membranes, wherein Figure a is the photo of the nanofiber membrane of Example 1, Figure b is the photo of the nanofiber membrane of Comparative Example 1, and Figure c is the photo of the nanofiber membrane of Comparative Example 2.

[0026] Figure 3 The photos are of contact angles of nanofiber membranes, wherein Figure A is the photo of the contact angle of the nanofiber membrane of Example 1, Figure B is the photo of the contact angle of the nanofiber membrane of Comparative Example 1, and Figure C is the photo of the contact angle of the nanofiber membrane of Comparative Example 2.

[0027] Figure 4 The photos are of temperature rising curves of nanofiber membranes under simulated sunlight (intensity of 1 sun).

[0028] Figure 5 The photos are of scanning electron microscope (SEM) images of the nanofiber membrane obtained in Example 1, wherein a is the SEM image with a magnification of 1000 times, and b is the SEM image with a magnification of 5000 times. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] Example 1

[0031] This embodiment provides a method for preparing a high-strength polymethyl methacrylate photothermal nanofiber membrane as follows:

[0032] Polymethyl methacrylate (PMMA) raw material was placed in an oven and dried at 70°C for 6 hours. 16 g of the dried PMMA, 0.5 g of dopamine hydrochloride, and 1 g of polyethyleneimine were added to 82.5 g of DMF and stirred at 60°C for 6 hours to obtain an electrospinning solution (e.g., ...). Figure 1 As shown in Figure A), during this process, due to the alkaline environment provided by polyethyleneimine, dopamine hydrochloride polymerizes in situ in the spinning solution to form polydopamine. The resulting electrospinning solution is transferred to a syringe for electrospinning to obtain nanofiber membranes (such as...). Figure 2 (As shown in Figure A). The obtained nanofiber membrane was then transferred to a blower oven and dried at 40°C for 12 hours to remove the solvent. The electrospinning conditions were: positive voltage of 20 kV, flow rate of 0.08 mL / h, receiving distance of 20 cm, indoor humidity of 40%, and aluminum foil as the receiving substrate.

[0033] The scanning electron microscope image of the hydrophilic polymethyl methacrylate nanofiber membrane obtained in this embodiment is as follows: Figure 5 As shown in the figures, Figure a is magnified 1000 times and Figure b is magnified 5000 times. The figures show that the fiber structure is relatively uniform, indicating good spinnability.

[0034] Example 2

[0035] This embodiment provides a method for preparing a high-strength polymethyl methacrylate photothermal nanofiber membrane as follows:

[0036] Polymethyl methacrylate (PMMA) raw material was placed in an oven and dried at 50°C for 8 hours. 8 g of the dried PMMA, 0.1 g of dopamine hydrochloride, and 0.25 g of polyethyleneimine were added to 91.65 g of DMF and stirred at 60°C for 10 hours to obtain an electrospinning solution. During this process, due to the alkaline environment provided by polyethyleneimine, dopamine hydrochloride polymerized in situ in the spinning solution to form polydopamine.

[0037] The obtained electrospinning solution was transferred to a syringe for electrospinning to obtain a nanofiber membrane. The obtained nanofiber membrane was then transferred to a forced-air constant-temperature oven and dried at 60°C for 6 hours to remove the solvent. The electrospinning conditions were: positive voltage of 12 kV, flow rate of 0.1 mL / h, receiving distance of 10 cm, ambient humidity of 25%, and aluminum foil as the receiving substrate.

[0038] The sample in Example 2 was tested to have a tensile strength of 0.28 MPa, a contact angle of 70.5°, and a temperature rise to about 56°C within 20 seconds under the irradiation of one sun.

[0039] Example 3

[0040] The preparation method of the high-strength polymethyl methacrylate photothermal nanofiber film provided in this embodiment is as follows:

[0041] The polymethyl methacrylate raw material was placed in an oven and dried at 50°C for 8 hours. 12 g of the dried polymethyl methacrylate, 0.25 g of dopamine hydrochloride, and 0.75 g of polyethyleneimine were added to 87 g of DMF, and stirred at 60°C for 8 hours to obtain an electrospinning solution. In this process, due to the alkaline environment provided by polyethyleneimine, dopamine hydrochloride was polymerized in situ into polydopamine in the spinning solution.

[0042] The obtained electrospinning solution was transferred to a syringe for electrospinning to obtain a nanofiber film. Then, the obtained nanofiber film was transferred to a blast thermostat for drying at 55°C for 9 hours to remove the solvent. The electrospinning conditions were as follows: the positive voltage for electrospinning was 16 kV, the flow rate was 0.09 mL / h, the receiving distance for electrospinning was 14 cm, the indoor environmental humidity was 30%, and aluminum foil was used as the receiving substrate.

[0043] The sample in Example 3 was tested to have a tensile strength of 0.35 MPa, a contact angle of 75.5°, and a temperature rise to about 65°C within 20 seconds under the irradiation of one sun.

[0044] Example 4

[0045] The preparation method of the high-strength polymethyl methacrylate photothermal nanofiber film provided in this embodiment is as follows:

[0046] The polymethyl methacrylate raw material was placed in an oven and dried at 65°C for 7.5 hours. 15 g of the dried polymethyl methacrylate, 0.4 g of dopamine hydrochloride, and 0.6 g of polyethyleneimine were added to 87 g of DMF, and stirred at 60°C for 9 hours to obtain an electrospinning solution. In this process, due to the alkaline environment provided by polyethyleneimine, dopamine hydrochloride was polymerized in situ into polydopamine in the spinning solution.

[0047] The obtained electrospinning solution was transferred to a syringe for electrospinning to obtain a nanofiber film. Then, the obtained nanofiber film was transferred to a blast thermostat for drying at 45°C for 11 hours to remove the solvent. The electrospinning conditions were as follows: the positive voltage for electrospinning was 18 kV, the flow rate was 0.095 mL / h, the receiving distance for electrospinning was 16 cm, the indoor environmental humidity was 35%, and aluminum foil was used as the receiving substrate.

[0048] The tensile strength of the sample in Example 4 was 0.37 MPa, the contact angle was 70.6°, and the temperature rose to about 71°C within 20 seconds under the irradiation of one sun.

[0049] Example 5

[0050] The preparation method of the high-strength polymethyl methacrylate photo-thermal nanofiber film provided in this embodiment is as follows:

[0051] The polymethyl methacrylate raw material was placed in an oven and dried at 65°C for 7.5 hours. 13 g of the dried polymethyl methacrylate, 0.45 g of dopamine hydrochloride and 0.95 g of polyethyleneimine were added to 86.6 g of DMF, and stirred at 57°C for 8 h to obtain an electrospinning solution. In this process, due to the alkaline environment provided by polyethyleneimine, dopamine hydrochloride was polymerized in situ into polydopamine in the spinning solution.

[0052] The obtained electrospinning solution was transferred to a syringe for electrospinning to obtain a nanofiber film. Then the obtained nanofiber film was transferred to a blast thermostat, and dried at 51°C for 10 h to remove the solvent. The electrospinning conditions were as follows: the positive voltage for electrospinning was 17 kV, the flow rate was 0.085 mL / h, the electrospinning receiving distance was 17 cm, the indoor environmental humidity was 30%, and aluminum foil was used as the receiving substrate.

[0053] The tensile strength of the sample in Example 5 was 0.35 MPa, the contact angle was 73.1°, and the temperature rose to about 62°C within 20 seconds under the irradiation of one sun.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that the film-forming material is a pure polymethyl methacrylate nanofiber film, and the specific preparation method is as follows:

[0056] The polymethyl methacrylate raw material was placed in an oven and dried at 70°C for 6 hours. 16 g of the dried polymethyl methacrylate was added to 84 g of DMF, and stirred at 60°C for 6 h to obtain an electrospinning solution (as shown in FIG. B of Figure 1 ). The obtained electrospinning solution was transferred to a syringe for electrospinning to obtain a nanofiber film (as shown in FIG. b of Figure 2 ). Then the obtained nanofiber film was transferred to a blast thermostat, and dried at 40°C for 12 h to remove the solvent. The electrospinning conditions were as follows: the positive voltage for electrospinning was 20 kV, the flow rate was 0.08 mL / h, the electrospinning receiving distance was 20 cm, the indoor environmental humidity was 40%, and aluminum foil was used as the receiving substrate.

[0057] Comparative Example 2

[0058] The difference between the present comparative example and Example 1 is that the film-forming material is polyethylene imine modified polymethyl methacrylate nanofiber film, and the specific preparation method is as follows:

[0059] The polymethyl methacrylate raw material was placed in an oven and dried at 70°C for 6 hours. 16 grams of dried polymethyl methacrylate and 1 gram of polyethylene imine were added to 83 grams of DMF and stirred at 60°C for 6 hours to obtain an electrospinning solution (as shown in FIG. C). Figure 1 The obtained electrospinning solution was transferred to a syringe for electrospinning to obtain a nanofiber film (as shown in FIG. c). Then the obtained nanofiber film was transferred to a blast constant temperature oven for 40°C drying for 12 hours to remove the solvent. The electrospinning conditions were as follows: the positive voltage of electrospinning was 20 kV, the flow rate was 0.08 mL / h, the electrospinning receiving distance was 20 cm, the indoor environmental humidity was 40%, and aluminum foil was used as the receiving substrate. Figure 2

[0060] To further illustrate the preparation method of the high-strength polymethyl methacrylate photothermal nanofiber film disclosed in the present application, the performance of the examples and comparative examples was measured.

[0061] Photothermal performance test: simulated sunlight (intensity of 1 sun) was used to irradiate the fiber, and an infrared thermal imager was used to record the fiber temperature rise curve.

[0062] Contact angle test: the contact angle of the nanofiber film surface was measured by an SDC-200S contact angle measuring instrument.

[0063] Mechanical property test of nanofiber film: AI-7000S1 universal tensile testing machine was used for testing, the sample length was 5 cm, the width was 2 cm, each time the stretching was carried out at a constant elongation rate of 50 mm / min, 5 samples were measured for each film, and the average value was taken.

[0064] Wherein Figure 1 is the spinning solution photo, picture A is Example 1, picture B is Comparative Example 1, and picture C is Comparative Example 2. As can be seen from the figure, the spinning solutions of Comparative Examples 1 and 2 are light transparent solutions, and Example 1 is black, indicating that polydopamine is formed in the spinning solution of Example 1.

[0065] Figure 2 is the nanofiber film photo, picture a is Example 1, picture b is Comparative Example 1, and picture c is Comparative Example 2. As can be seen from the figure, the nanofiber film obtained in Example 1 is black, and the nanofiber films obtained in Comparative Examples 1 and 2 are white.

[0066] After testing, the tensile strength of the sample in Example 1 was 0.48 MPa, and the contact angle was 67.8° (as shown in FIG.​Figure 3 As shown in Figure A), under sunlight, the temperature rises to approximately 76°C within 20 seconds (as shown in Figure A). Figure 4 (As shown).

[0067] The tensile strength of the specimen in Comparative Example 1 was 0.18 MPa, and the contact angle was 123.6° (e.g., ...). Figure 3 As shown in Figure B), under sunlight, the temperature only rises to about 36°C within 20 seconds (as shown in Figure B). Figure 4 (As shown).

[0068] In Comparative Example 2, the tensile strength was 0.19 MPa and the contact angle was 94.1° (e.g., ...). Figure 3 As shown in Figure C), under sunlight, the temperature only rises to about 36°C within 20 seconds (as shown in Figure C). Figure 4 (As shown).

[0069] Comparative test results show that the strength, hydrophilicity, and photothermal properties of the sample in Example 1 are significantly better than those in Comparative Example 1 and Comparative Example 2. The high tensile strength of Example 1 is due to the fact that polydopamine itself is rich in benzene rings and has a rigid molecule, which can be used as a reinforcing agent to fill the polymer. Example 1 has a smaller contact angle because polyethyleneimine and polydopamine containing a large number of hydrophilic groups are introduced into the PMMA spinning solution, which greatly improves the hydrophilicity of the prepared electrospun nanofiber membrane. The nanofiber membrane of Example 1 has better photothermal properties, firstly because its dark color has a heat-absorbing effect, and secondly because polydopamine has a similar polymerization mechanism to natural melanin and has high light absorption characteristics in the near-infrared spectrum, which makes the high-strength polypropylene fiber membrane prepared by this patent have good photothermal effects.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-strength polymethyl methacrylate photo-thermal nanofiber membranes, characterized by, It comprises the following steps: (1) Spinning solution preparation: Poly (methyl methacrylate) is dried and then added into N-N dimethyl formamide together with dopamine hydrochloride and polyethyleneimine, and heated and stirred to obtain an electrospinning solution; wherein the mass fraction of poly (methyl methacrylate), dopamine hydrochloride and polyethyleneimine in the electrospinning solution is 8-16%wt, 0.1-0.5%wt and 0.25-1%wt respectively; (2) Electrospinning: The electrospinning solution of step (1) is electrospun to obtain a nanofiber membrane, and the solvent is removed by drying to obtain a high-strength poly (methyl methacrylate) photothermal nanofiber membrane.

2. The method for preparing the high-strength polymethyl methacrylate photothermal nanofiber membrane according to claim 1, characterized in that: In step (1), the drying temperature of poly (methyl methacrylate) is 50-70℃, and the time is 6-8h.

3. The method for preparing the high-strength polymethyl methacrylate photothermal nanofiber membrane according to claim 2, characterized in that: In step (1), the temperature of heating and stirring is 57-60℃, and the time is 6-10h.

4. The method for preparing the high-strength polymethyl methacrylate photothermal nanofiber membrane according to claim 3, characterized in that: In step (2), the electrospinning parameters are as follows: positive voltage is 12-20kV, flow rate is 0.08-0.1mL / h, electrospinning receiving distance is 10-20cm, indoor environmental humidity is 25-40%, and aluminum foil is used as the receiving substrate.

5. The method for preparing the high-strength polymethyl methacrylate photothermal nanofiber membrane according to claim 4, characterized in that: In step (2), the drying temperature after electrospinning is 40-60℃, and the time is 6-12h.

6. The high-strength poly (methyl methacrylate) photothermal nanofiber membrane prepared by the method of any one of claims 1-5.

7. The high strength polymethyl methacrylate photothermal nanofiber membrane according to claim 6, characterized by: The tensile strength of the high-strength poly (methyl methacrylate) photothermal nanofiber membrane is 0.28-0.48MPa; under the intensity of 1 solar light, the temperature rises from room temperature 30℃ to 55-76℃ within 20s.

8. The high-strength polymethyl methacrylate photothermal nanofiber membrane according to claim 7, characterized by: The contact angle of the poly (methyl methacrylate) photothermal nanofiber membrane is 65-76°.

9. The application of the high-strength poly (methyl methacrylate) photothermal nanofiber membrane of claim 7 or 8 in indoor heating, military and civilian outdoor camping facilities, solar self-produced heat insulation clothing.

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