A heat-insulating safety material and a preparation method thereof

Abstract

The present application discloses a heat-insulating safety material and a preparation method thereof, relating to the technical field of heat-insulating materials, including a filling material for blocking heat resistance. The filling material includes 20-50 parts by weight of silica, 10-30 parts of calcium silicate, 100-180 parts of polypropylene fiber, 20-50 parts of an adhesive, 10-25 parts of diatomaceous earth, 5-10 parts of an iron-based oxygen absorber, and 0.6-1.5 parts of tea polyphenols. The present application combines tea polyphenols through amino groups to achieve the coating of tea polyphenols, thereby reducing the consumption of tea polyphenols, and transports reactant molecules to the surface active sites of the iron-based oxygen absorber through the porous structure on the diatomaceous earth for enriching reactant molecules, so that while the iron-based oxygen absorber protects the stability of tea polyphenol molecules, it synergistically realizes an effective antioxidant effect with tea polyphenols, and significantly improves the ability to withstand high temperature and high pressure by enhancing the structural stability of the composite system.

Description

Technical Field

[0001] This application relates to the technical field of thermal insulation materials, and particularly relates to a thermal insulation safety material and a preparation method thereof. Background Art

[0002] Thermal insulation materials are widely used in various fields such as industry, construction, and daily life. In various field scenarios, the thermal insulation effect of thermal insulation materials has received much attention. Common thermal insulation materials include three categories: porous materials, heat-reflective materials, and vacuum materials. The former uses the pores contained in the material itself for heat insulation because the thermal conductivity of the air or inert gas in the pores is very low, such as foam materials, fiber materials, etc.; heat-reflective materials have a very high reflection coefficient and can reflect heat, such as gold, silver, nickel, aluminum foil, or polyester and polyimide films coated with metal. Vacuum insulation materials use the internal vacuum of the material to block convection for heat insulation.

[0003] The Chinese patent application document with the publication number CN118530536A discloses a thermal insulation safety material and a preparation method thereof. The thermal insulation safety material includes an outer polyurethane layer and a filler located inside the polyurethane layer. The filler includes the following components in parts by weight: 20 - 80 parts of microporous silica particles; 10 - 40 parts of microporous calcium silicate particles; 5 - 20 parts of an oxygen absorber; 100 - 180 parts of polypropylene fibers; 20 - 60 parts of an adhesive; and part or all of the oxygen absorber is distributed in the micropores of the microporous silica particles and the microporous calcium silicate particles.

[0004] However, when this thermal insulation safety material uses tea polyphenols as a component of the oxygen absorber, above 100 °C, and under long-term high-temperature conditions, and due to the high pressure caused by the high temperature, it will greatly promote the decomposition of tea polyphenols, thus affecting the use and reuse effects of the oxygen absorber and the use safety performance of the thermal insulation safety material, and there is room for improvement. Summary of the Invention

[0005] In view of this, the first object of this application is to provide a thermal insulation safety material to achieve the purpose of improving thermal insulation performance and extending service life. The specific scheme is as follows:

[0006] A thermal insulation safety material includes a filler material for blocking and resisting heat. The filler material includes 20 - 50 parts by weight of silica, 10 - 30 parts of calcium silicate, 100 - 180 parts of polypropylene fibers, 20 - 50 parts of an adhesive, 10 - 25 parts of diatomaceous earth, 5 - 10 parts of an iron-based oxygen absorber, and 0.6 - 1.5 parts of tea polyphenols.

[0007] Preferably: The iron-based oxygen absorber is zinc ferrite @ZnFe2O4.

[0008] Preferably, the diatomaceous earth, iron-based oxygen absorber and tea polyphenols are prepared to obtain an oxygen-absorbing and heat-resistant agent.

[0009] Preferably, the preparation of the oxygen-absorbing and heat-resistant agent includes an iron-based oxygen absorber composite diatomaceous earth part and a tea polyphenol composite grafting part; the iron-based oxygen absorber composite diatomaceous earth part includes surface modification of the iron-based oxygen absorber, activation of the diatomaceous earth, and a mixing cross-linking reaction to obtain an iron-based oxygen absorber composite diatomaceous earth; the tea polyphenol composite grafting part includes putting the iron-based oxygen absorber composite diatomaceous earth into a tea polyphenol solution, stirring and reacting to obtain an oxygen-absorbing and heat-resistant agent grafted with tea polyphenols.

[0010] Preferably, the surface modification of the iron-based oxygen absorber is as follows: putting the iron-based oxygen absorber into a γ-aminopropyltriethoxysilane solution, controlling the temperature of the γ-aminopropyltriethoxysilane solution to be 50-70 °C, stirring and reacting for 2-4 h, then washing with ethanol and drying at 60-80 °C to obtain a modified iron-based oxygen absorber; the activation of the diatomaceous earth is to obtain activated diatomaceous earth after crushing, washing and drying at 100-120 °C or after crushing, acid leaching, washing and drying at 50-80 °C; the mixing cross-linking reaction is: putting the modified iron-based oxygen absorber and the activated diatomaceous earth into an organic solvent, adding a cross-linking agent with a mass percentage of 1-1.5%, stirring and reacting for 1-2 h, and then washing with the organic solvent and drying to obtain an iron-based oxygen absorber composite diatomaceous earth.

[0011] Preferably, the concentration of tea polyphenols in the tea polyphenol solution is 0.5-2 mg / mL, the temperature is 40-60 °C, and after stirring and reacting for 2-4 h, the precipitate is washed with deionized water and dried to obtain an oxygen-absorbing and heat-resistant agent.

[0012] Preferably, the particle size of the silica is 50-200 μm, and the particle size of the calcium silicate is 300-800 μm.

[0013] Preferably, the diameter of the polypropylene fiber is 200-300 μm.

[0014] The second object of the present invention is to provide a preparation method of a heat-insulating and safe material for preparing the heat-insulating and safe material as described above, including the following steps:

[0015] Step 1, material preparation: Prepare silica, calcium silicate, polypropylene fiber, binder, diatomaceous earth, iron-based oxygen absorber and tea polyphenols according to parts by weight;

[0016] Step 2, prepare an oxygen-absorbing and heat-resistant agent: perform a composite reaction on diatomaceous earth, iron-based oxygen absorber and tea polyphenols to obtain an oxygen-absorbing and heat-resistant agent;

[0017] Step 3: Prepare the filling material: Mix the oxygen-absorbing heat-resistant agent with silica, calcium silicate, and polypropylene fibers evenly and compact them to obtain a blank. Then immerse the blank in the adhesive solution, take it out after impregnation, volatilize easily and bond to obtain the filling material;

[0018] Step 4: Prepare the molding: Wrap a layer of polyurethane layer on the surface of the filling material.

[0019] Preferably: The thermal conductivity of the polyurethane layer is 0.02 - 0.03 W / (m·K).

[0020] Through the above solutions, this application provides a heat-insulating safety material and its preparation method. The preparation method of this heat-insulating safety material has the effects of convenient process and low operation difficulty. While the iron-based oxygen absorber in this heat-insulating safety material catalyzes and promotes the antioxidant effect of tea polyphenols, it combines with tea polyphenols through amino groups to achieve the coating of tea polyphenols, thereby reducing the consumption of tea polyphenols; at the same time, the iron-based oxygen absorber first combines with diatomaceous earth to increase the specific surface area and adsorption capacity, and then transports the reactant molecules to the surface active sites of the iron-based oxygen absorber through the porous structure on the diatomaceous earth for enriching reactant molecules, so that while protecting the molecular stability of tea polyphenols, the iron-based oxygen absorber synergistically with tea polyphenols achieves an effective antioxidant effect, and by improving the structural stability of the composite system, significantly improves the high temperature and high pressure resistance. Due to the porous structure of diatomaceous earth effectively supporting and fixing zinc ferrite, it can effectively prevent the agglomeration or sintering of zinc ferrite during use, while keeping the zinc ferrite combined with tea polyphenols in a good dispersion state and structural stability. Specific Embodiments

[0021] The technical solutions in the embodiments of this application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0022] It should be mentioned that the adhesive in the embodiments of this application is an aqueous polyurethane adhesive purchased from 3M Company. The organic solvent is toluene, and the cross-linking agent is diisocyanate MDI, all of which are commercially available. The particle size of silica is 50 - 200 μm, the particle size of calcium silicate is 300 - 800 μm. And the diameter of the polypropylene fiber is 200 - 300 μm.

[0023] The following will specifically describe a heat-insulating safety material and its preparation method of this application.

[0024] A heat-insulating safety material, comprising a filling material for heat resistance, the filling material including 20-50 parts by weight of silica, 10-30 parts of calcium silicate, 100-180 parts of polypropylene fiber, 20-50 parts of adhesive, 10-25 parts of diatomaceous earth, 5-10 parts of iron-based oxygen absorber and 0.6-1.5 parts of tea polyphenols.

[0025] In the embodiment of the present application, the iron-based oxygen absorber is zinc ferrite @ZnFe2O4.

[0026] And after preparing the oxygen-absorbing and heat-resistant agent by compounding diatomaceous earth, iron-based oxygen absorber and tea polyphenols, and then mixing with other components, the antioxidant performance and oxygen-absorbing performance are effectively improved, and at the same time, the structural stability of the iron-based oxygen absorber and tea polyphenols is improved, so as to achieve the purpose of improving the heat-insulating performance and extending the service life.

[0027] It should be mentioned that the preparation of the oxygen-absorbing and heat-resistant agent includes an iron-based oxygen absorber compounded with diatomaceous earth part and a tea polyphenol compounded grafting part. Among them, the iron-based oxygen absorber compounded with diatomaceous earth part includes surface modification of the iron-based oxygen absorber, activation of diatomaceous earth and mixed cross-linking reaction to obtain an iron-based oxygen absorber compounded with diatomaceous earth. The tea polyphenol compounded grafting part includes putting the iron-based oxygen absorber compounded with diatomaceous earth into a tea polyphenol solution with a concentration of 0.5-2 mg / mL of tea polyphenols and stirring and reacting, controlling the temperature at 40-60 °C, washing the precipitate with deionized water and drying after stirring and reacting for 2-4 h to obtain the oxygen-absorbing and heat-resistant agent.

[0028] The surface modification of the iron-based oxygen absorber is as follows: putting the iron-based oxygen absorber into a γ-aminopropyltriethoxysilane solution, controlling the temperature of the γ-aminopropyltriethoxysilane solution at 50-70 °C, and stirring and reacting for 2-4 h, and then obtaining the modified iron-based oxygen absorber after washing with ethanol and drying at 60-80 °C; the activation of the diatomaceous earth is to obtain activated diatomaceous earth after crushing, washing and drying at 100-120 °C or crushing, acid leaching, washing and drying at 50-80 °C; the mixed cross-linking reaction is: putting the modified iron-based oxygen absorber and activated diatomaceous earth into an organic solvent, adding a cross-linking agent with a mass percentage of 1-1.5% and then stirring and reacting for 1-2 h, and then drying after washing with the organic solvent to obtain an iron-based oxygen absorber compounded with diatomaceous earth.

[0029] A preparation method of a heat-insulating safety material for preparing the heat-insulating safety material as described above, comprising the following steps:

[0030] Step 1, material preparation: Prepare silica, calcium silicate, polypropylene fiber, adhesive, diatomaceous earth, iron-based oxygen absorber and tea polyphenols according to parts by weight;

[0031] Step 2, preparing an oxygen-absorbing and heat-resistant agent: compounding diatomaceous earth, iron-based oxygen absorber and tea polyphenols to obtain an oxygen-absorbing and heat-resistant agent;

[0032] Step 3: Prepare the filling material: Mix the oxygen-absorbing heat-resistant agent with silicon dioxide, calcium silicate, and polypropylene fibers evenly and compact them to obtain a blank. Then immerse the blank in the adhesive solution, take it out after impregnation, and volatilize and bond it to obtain the filling material;

[0033] Step 4: Prepare the molding: Wrap a layer of polyurethane layer on the surface of the filling material, and the thermal conductivity of the polyurethane layer is 0.02 - 0.03 W / (m·K).

[0034] Example 1

[0035] A heat-insulating safety material includes a filling material for blocking heat resistance. The filling material includes 50 parts by weight of silicon dioxide, 30 parts of calcium silicate, 180 parts of polypropylene fibers, 50 parts of adhesive, 25 parts of diatomaceous earth, 10 parts of iron-based oxygen-absorbing agent, and 1.5 parts of tea polyphenols.

[0036] In the embodiment of the present application, the iron-based oxygen-absorbing agent is zinc ferrite @ZnFe2O4.

[0037] And after preparing the oxygen-absorbing heat-resistant agent by preparing diatomaceous earth, iron-based oxygen-absorbing agent, and tea polyphenols, and then mixing it with other components, the antioxidant performance and oxygen-absorbing performance are effectively improved while the structural stability of the iron-based oxygen-absorbing agent and tea polyphenols is improved, so as to achieve the purpose of improving the heat-insulating performance and extending the service life.

[0038] It should be mentioned that the preparation of the oxygen-absorbing heat-resistant agent includes an iron-based oxygen-absorbing agent composite diatomaceous earth part and a tea polyphenol composite grafting part. Among them, the iron-based oxygen-absorbing agent composite diatomaceous earth part includes surface modification of the iron-based oxygen-absorbing agent, activation of diatomaceous earth, and mixed cross-linking reaction to obtain the iron-based oxygen-absorbing agent composite diatomaceous earth. The tea polyphenol composite grafting part includes putting the iron-based oxygen-absorbing agent composite diatomaceous earth into a tea polyphenol solution with a concentration of 1 mg / mL of tea polyphenols, stirring and reacting, controlling the temperature at 50°C, washing the precipitate with deionized water and drying after stirring and reacting for 3 h to obtain the oxygen-absorbing heat-resistant agent.

[0039] The surface modification of the iron-based oxygen-absorbing agent is: Put the iron-based oxygen-absorbing agent into the γ-aminopropyltriethoxysilane solution, control the temperature of the γ-aminopropyltriethoxysilane solution at 60°C, and stir and react for 3 h. Then obtain the modified iron-based oxygen-absorbing agent after washing with ethanol and drying at 70°C; The activation of the diatomaceous earth is to obtain activated diatomaceous earth after crushing, washing, and drying at 108°C or crushing, acid leaching, washing, and drying at 60°C; The mixed cross-linking reaction is: Put the modified iron-based oxygen-absorbing agent and activated diatomaceous earth into an organic solvent, then add a cross-linking agent with a mass percentage of 1% and stir and react for 2 h, and then wash with the organic solvent and dry to obtain the iron-based oxygen-absorbing agent composite diatomaceous earth.

[0040] A preparation method of a heat-insulating safety material for preparing the heat-insulating safety material as described above, comprising the following steps:

[0041] Step 1, material preparation: Prepare silica, calcium silicate, polypropylene fiber, binder, diatomaceous earth, iron-based oxygen absorber, and tea polyphenols according to parts by weight;

[0042] Step 2, preparation of an oxygen-absorbing heat-resistant agent: Carry out a composite reaction on diatomaceous earth, an iron-based oxygen absorber, and tea polyphenols to obtain an oxygen-absorbing heat-resistant agent;

[0043] Step 3, preparation of a filling material: Mix the oxygen-absorbing heat-resistant agent with silica, calcium silicate, and polypropylene fiber evenly and compact them to obtain a blank, and then immerse the blank in a binder solution, take it out and volatilize it easily and bond it to obtain a filling material;

[0044] Step 4, preparation of molding: Wrap a layer of polyurethane layer on the surface of the filling material, and the thermal conductivity of the polyurethane layer is 0.023 W / (m·K).

[0045] Example 2

[0046] The difference between Example 2 and Example 1 is that the filling material in Example 2 includes 20 parts by weight of silica, 10 parts by weight of calcium silicate, 100 parts by weight of polypropylene fiber, 20 parts by weight of binder, 10 parts by weight of diatomaceous earth, 5 parts by weight of iron-based oxygen absorber, and 0.6 parts by weight of tea polyphenols.

[0047] Example 3

[0048] The difference between Example 3 and Example 1 is that the filling material in Example 3 includes 30 parts by weight of silica, 20 parts by weight of calcium silicate, 150 parts by weight of polypropylene fiber, 30 parts by weight of binder, 16 parts by weight of diatomaceous earth, 7 parts by weight of iron-based oxygen absorber, and 0.9 parts by weight of tea polyphenols.

[0049] Comparative Example 1

[0050] The difference between Comparative Example 1 and Example 1 is that the iron-based oxygen absorber and tea polyphenols are not added in Comparative Example 1.

[0051] Comparative Example 2

[0052] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not have a tea polyphenol composite grafting part.

[0053] Comparative Example 3

[0054] The difference between Comparative Example 3 and Example 2 is that Comparative Example 3 does not have an iron-based oxygen absorber composite diatomaceous earth part.

[0055] Heat insulation performance test:

[0056] 1. Place the heat-insulating safety materials in Examples 1 to 3 and Comparative Examples 1 to 3 in a plate-shaped container and seal it. Cover the plate-shaped container on the heat source, with the periphery of the heat source sealed. Control the temperature of the heat source at 500 °C. After 1 h, record the temperature on the side of the plate-shaped container away from the heat source. The temperature ranges from 50 - 500 °C, with each 50 °C as one level, from low to high as levels 1 - 10. The lower the level, the better the heat-insulating performance.

[0057] 2. Repeat the above test, and the interval between two adjacent tests is 6 h.

[0058] The performance test results are shown in Table 1 below.

[0059] Table 1 Performance Test Results

[0060]

[0061] As can be seen from Table 1 above, by adding an iron-based oxygen absorber and tea polyphenols to the filling material, the heat-insulating performance of the heat-insulating safety material can be improved. When the iron-based oxygen absorber is compounded with diatomaceous earth in the iron-based oxygen absorber composite diatomaceous earth part, the diatomaceous earth can promote the heat-insulating performance and catalytic effect of the iron-based oxygen absorber. Furthermore, when the tea polyphenols are compounded with the iron-based oxygen absorber, while extending the antioxidant effect of the tea polyphenols, it can synergistically make the filling material filled with vacuum anaerobic gas, thereby achieving the purpose of significantly reducing the thermal conductivity and making the heat-insulating safety material have an effective heat-insulating effect.

[0062] In summary, the present application provides a heat-insulating safety material and its preparation method. The preparation method of the heat-insulating safety material has the effects of convenient process and low operation difficulty. The heat-insulating safety material, while catalytically promoting the antioxidant effect of tea polyphenols by using an iron-based oxygen absorber, combines with tea polyphenols through amino groups to achieve the coating of tea polyphenols, thereby reducing the consumption of tea polyphenols. At the same time, the iron-based oxygen absorber first combines with diatomaceous earth to increase the specific surface area and adsorption capacity, and then transports the reactant molecules to the surface active sites of the iron-based oxygen absorber through the porous structure on the diatomaceous earth for enriching reactant molecules, so that the iron-based oxygen absorber protects the stability of tea polyphenol molecules while synergistically achieving an effective antioxidant effect with tea polyphenols, and significantly improves the high-temperature and high-pressure resistance by enhancing the structural stability of the composite system. Due to the porous structure of diatomaceous earth effectively supporting and fixing zinc ferrite, it can effectively prevent the agglomeration or sintering of zinc ferrite during use while keeping the zinc ferrite combined with tea polyphenols in a good dispersed state and structural stability.

[0063] The "first", "second", "third", "fourth", etc. (if any) involved in this application are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments described herein can be implemented in an order other than that shown or described. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method or device comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods or devices.

[0064] It should be noted that the descriptions involving "first", "second", etc. in this application are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. Additionally, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0065] Specific examples are used herein to elaborate on the principles and implementation manners of this application. The descriptions of the above embodiments are only for helping to understand the method and its core idea of this application; at the same time, for those of ordinary skill in the art, based on the idea of this application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. A heat-insulating safety material, comprising a filling material for heat-insulating and heat-resistant, characterized in that: The filling material comprises, by weight, 20-50 parts of silicon dioxide, 10-30 parts of calcium silicate, 100-180 parts of polypropylene fiber, 20-50 parts of adhesive, 10-25 parts of diatomaceous earth, 5-10 parts of iron-based oxygen absorber and 0.6-1.5 parts of tea polyphenols; wherein: the diatomaceous earth, the iron-based oxygen absorber and the tea polyphenols are used to prepare an oxygen-absorbing heat-resistant agent; the preparation of the oxygen-absorbing heat-resistant agent comprises an iron-based oxygen absorber composite diatomaceous earth part and a tea polyphenol composite grafting part; the iron-based oxygen absorber composite diatomaceous earth part comprises surface modification of the iron-based oxygen absorber, activation of the diatomaceous earth and mixed cross-linking reaction to obtain the iron-based oxygen absorber composite diatomaceous earth; the tea polyphenol composite grafting part comprises adding the iron-based oxygen absorber composite diatomaceous earth into a tea polyphenol solution and stirring the reaction to obtain the oxygen-absorbing heat-resistant agent grafted with tea polyphenols.

2. A heat-insulating safety material according to claim 1, characterized in that: The iron-based oxygen absorber is zinc ferrite @ZnFe2O4.

3. A heat-insulating safety material according to claim 1, characterized in that: The surface modification of the iron-based oxygen absorber is as follows: the iron-based oxygen absorber is put into a γ-aminopropyltriethoxysilane solution, the temperature of the γ-aminopropyltriethoxysilane solution is controlled to be 50-70°C, and the reaction is stirred for 2-4h, and then the modified iron-based oxygen absorber is obtained after washing with ethanol and drying at 60-80°C; the diatomite activation is as follows: the diatomite is crushed, washed and dried at 100-120°C or crushed, acid-leached, washed and dried at 50-80°C to obtain activated diatomite; the mixed cross-linking reaction is as follows: the modified iron-based oxygen absorber and the activated diatomite are put into an organic solvent, and then a cross-linking agent is added in an amount of 1-1.5% by mass, and the reaction is stirred for 1-2h, and then the iron-based oxygen absorber composite diatomite is obtained after washing with an organic solvent and drying.

4. The heat-insulating safety material according to claim 1, characterized in that: The concentration of tea polyphenols in the tea polyphenol solution is 0.5-2 mg / mL, the temperature is 40-60° C., and after stirring and reacting for 2-4 hours, the precipitate is washed with deionized water and dried to obtain the oxygen-absorbing heat-resistant agent.

5. The heat-insulating safety material according to claim 1, characterized in that: The particle size of the silicon dioxide is 50-200 μm, and the particle size of the calcium silicate is 300-800 μm.

6. The heat-insulating safety material according to claim 1, characterized in that: The diameter of the polypropylene fiber is 200-300 μm.

7. A method for preparing a heat-insulating safety material, used for preparing the heat-insulating safety material according to any one of claims 1 to 6, characterized in that: The steps include: Step 1, material preparation: prepare silicon dioxide, calcium silicate, polypropylene fiber, adhesive, diatomaceous earth, iron-based oxygen absorber and tea polyphenols according to weight parts; Step 2, preparing an oxygen-absorbing heat-resistant agent: compounding diatomaceous earth, an iron-based oxygen-absorbing agent and tea polyphenols to obtain an oxygen-absorbing heat-resistant agent; Step 3, preparing the filling material: mixing the oxygen absorbing heat-resistant agent with silicon dioxide, calcium silicate, and polypropylene fiber evenly and pressing them to obtain a blank, and then immersing the blank in an adhesive solution, taking it out to volatilize easily and bond it to obtain a filling material; Step 4: Preparation and molding: Wrap a layer of polyurethane on the surface of the filling material.

8. The method for preparing a heat-insulating safety material according to claim 7, characterized in that: The thermal conductivity of the polyurethane layer is 0.02-0.03 W / (m·K).

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