Preparation method and application of solid-solid phase change material

Abstract

The invention relates to the field of phase change materials, in particular to a preparation method of a solid-solid phase change material, which comprises the following steps: step 1, reacting chitosan with acrylamide in an acetic acid solution to obtain a chitosan-acrylamide grafted copolymer; 2, in an ethanol solution, the chitosan-acrylamide grafted copolymer reacts with oleic acid to obtain the solid-solid phase change material. The reaction can endow the material with hydrophobicity and biocompatibility. According to the prepared solid-solid phase change material, the chitosan-acrylamide grafted copolymer serves as a hard segment, oleic acid serves as a soft segment, the high temperature resistance is improved, and meanwhile the high heat storage performance is achieved. The prepared solid-solid phase change material is high in operability, and the phase change temperature can meet the road surface use requirement in winter in the north.

Description

Technical Field

[0001] This invention relates to the field of phase change materials, and particularly to the field of phase change materials that can be used for road paving. Background Technology

[0002] When phase change materials (PCMs) are used in road engineering, their phase change temperature should meet the corresponding application requirements so that the PCMs can effectively reduce temperature-related damage to the road structure through phase change. For example, by adding a certain amount of phase change temperature regulator (PCM) to the pavement material of road engineering, these PCMs will melt and undergo a phase change when the pavement temperature exceeds the phase change temperature, thereby absorbing the surrounding heat and forming a protective layer for the road surface.

[0003] Adding phase change materials (PCMs) to asphalt concrete or cement concrete will alter the composition of the mixture to some extent. Appropriate addition of PCMs can ensure good mechanical properties in cement concrete or asphalt concrete while also enabling it to absorb and release heat. This reduces the required volume of PCMs and minimizes their impact on the mechanical properties of the original mixture. Increasing the specific heat capacity of PCMs will allow them to better regulate the temperature of the mixture during sensible heat absorption and release.

[0004] Patent CN 201610686246.8 reports the preparation and application of a solid-solid phase change material, but its phase change temperature is above 35℃. Patent CN 202010855782.2 reports a geopolymer composite phase change material suitable for roadbeds, which mixes the geopolymer slurry with the phase change material in a specific mold, which is not conducive to road paving operations and limits its application scope. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to provide a phase change material with a phase change temperature in the range of -9 to 20°C, suitable for road paving in northern regions.

[0006] The technical solution adopted in this invention is: a method for preparing a solid-solid phase change material, which is carried out according to the following steps.

[0007] Step 1: Chitosan and acrylamide react in an acetic acid solution to obtain a chitosan-acrylamide graft copolymer. This copolymer combines the natural biocompatibility of chitosan with the flocculating ability of acrylamide polymers. By selecting different initiators and optimizing reaction conditions, the structure and properties of the product can be controlled to meet various application requirements.

[0008] Step 2: In an ethanol solution, the chitosan-acrylamide graft copolymer reacts with oleic acid to obtain a solid-solid phase change material. This reaction imparts hydrophobicity and biocompatibility to the material.

[0009] In step one, before the reaction between chitosan and acrylamide, the mass ratio of acrylamide to chitosan is 3-5; in step two, before the reaction between the chitosan-acrylamide graft copolymer and oleic acid, the mass ratio of the chitosan-acrylamide graft copolymer to oleic acid is 2-4.

[0010] In step one, the mass percentage concentration of the acetic acid solution is 1-3%; in step two, the mass percentage concentration of the ethanol solution is 10-90%.

[0011] In step one, the reaction conditions for chitosan and acrylamide are as follows: under nitrogen protection in a sealed reactor vessel, cerium ammonium nitrate initiator is added, and the reaction is carried out in a constant temperature water bath at 40-50°C for 3-6 hours. The resulting chitosan-acrylamide graft copolymer is a gel-like substance.

[0012] Before the reaction between chitosan and acrylamide, the mass of cerium ammonium nitrate initiator added is 0.2 to 0.4% of the total mass of acrylamide and chitosan.

[0013] In step two, the chitosan-acrylamide graft copolymer used to react with oleic acid is obtained by crushing, purifying with acetone, washing with anhydrous ethanol, and drying the chitosan-acrylamide graft copolymer prepared in step one until the mass is constant.

[0014] In step two, the reaction conditions between the chitosan-acrylamide graft copolymer and oleic acid are as follows: the reaction is stirred at a first temperature, and the product is separated by refrigeration at 4°C; under vacuum conditions, the product is reacted again in an ethanol solution at a second temperature to obtain a solid-solid phase change material.

[0015] The first temperature is 50-70℃, and the reaction time is 8-10h. The second temperature is 80-100℃, and the reaction time is 2-6h.

[0016] An application of a solid-solid phase change material, which is added to asphalt concrete or cement concrete used for road paving.

[0017] The beneficial effects of this invention are: the solid-solid phase change material prepared by this invention uses chitosan-acrylamide graft copolymer as the hard segment and oleic acid as the soft segment, which improves its high-temperature resistance and also has high heat storage performance. The solid-solid phase change material prepared by this invention has strong operability, and its phase change temperature can meet the requirements for road surface use in northern winters. Attached Figure Description

[0018] Figure 1This is the differential scanning calorimetry (DSC) curve in Embodiment 1 of the present invention. Detailed Implementation

[0019] Solid-solid phase change materials (SCTs) are intelligent materials capable of reversible phase transitions between solid and solid states, efficiently absorbing and releasing heat. They are particularly suitable for scenarios requiring high safety and stability. Key features include: Solid-state phase change: Remaining solid during heat absorption and release, eliminating leakage risk and minimizing volume change; High-efficiency energy storage: Phase change enthalpy (energy storage capacity) can reach tens to hundreds of joules per gram, far exceeding that of ordinary materials; Cyclic stability: Reusable with slow performance degradation.

[0020] Example 1: A method for preparing a solid-solid phase change material, comprising the following steps.

[0021] Step 1: In a constant temperature water bath at 40℃, add 5g of chitosan and 25g of acrylamide monomer to 100ml of 2% acetic acid solution, stir thoroughly to dissolve completely, remove oxygen by purging with nitrogen, add 0.12g of cerium ammonium nitrate under nitrogen protection, and react for 6 hours under sealed conditions to obtain a gel-like graft copolymer chitosan-acrylamide graft copolymer.

[0022] The gel-like graft copolymer chitosan-acrylamide graft copolymer was crushed, purified with acetone, washed and dried with anhydrous ethanol, and then dried in a constant temperature drying oven until the quality was constant. Finally, the product was pulverized for later use.

[0023] Step 2: Add 5g of the pulverized chitosan-acrylamide graft copolymer prepared in Step 1 and 1.25g of oleic acid to 100ml of ethanol / water solution (50% by mass). Stir and react at 60℃ for 10h, then refrigerate at 4℃ to separate the lower precipitate. Place the separated product in 100ml of ethanol / water solution (50% by mass) and react at 80℃ for 6h to precipitate and obtain a solid-solid phase change material. After the reaction is complete, wash the solid-solid phase change material with ethanol and then dry it.

[0024] Perform differential scanning calorimetry (DSC) experiments and obtain the differential scanning calorimetry (DSC) curve, such as... Figure 1 As shown.

[0025] As shown in Table 1, the exothermic temperature of this solid-solid phase change material is 18.1℃, the endothermic temperature is -7.4℃, the melting enthalpy is 30.2 J / g, and the solidification enthalpy is 32.3 J / g.

[0026] Example 2: A method for preparing a solid-solid phase change material, comprising the following steps.

[0027] Step 1: In a constant temperature water bath at 50℃, add 5g of chitosan and 15g of acrylamide monomer to 100ml of 2% acetic acid solution, stir thoroughly to dissolve completely, remove oxygen by purging with nitrogen, add 0.04g of cerium ammonium nitrate under nitrogen protection, and react for 3h under sealed conditions to obtain a gel-like graft copolymer chitosan-acrylamide graft copolymer.

[0028] The gel-like graft copolymer chitosan-acrylamide graft copolymer was crushed, purified with acetone, washed and dried with anhydrous ethanol, and then dried in a constant temperature drying oven until the quality was constant. Finally, the product was pulverized for later use.

[0029] Step 2: Add 5g of the pulverized chitosan-acrylamide graft copolymer prepared in Step 1 and 2.5g of oleic acid to 100ml of ethanol / water solution (30% by mass). Stir and react at 60℃ for 10h, then refrigerate at 4℃ to separate the lower precipitate. Place the separated product in 100ml of ethanol / water solution (30% by mass) and react at 100℃ for 2h to precipitate and obtain a solid-solid phase change material. After the reaction is complete, wash the solid-solid phase change material with ethanol and then dry it.

[0030] As shown in the table, the exothermic temperature of this solid-solid phase change material is 17.9℃, the endothermic temperature is -7.9℃, the melting enthalpy is 45.1 J / g, and the solidification enthalpy is 43.8 J / g.

[0031] Example 3: A method for preparing a solid-solid phase change material, comprising the following steps.

[0032] Step 1: In a constant temperature water bath at 40℃, add 5g of chitosan and 15g of acrylamide monomer to 100ml of 2% acetic acid solution, stir thoroughly to dissolve completely, remove oxygen by purging with nitrogen, add 0.06g of cerium ammonium nitrate under nitrogen protection, and react for 5h under sealed conditions to obtain a gel-like graft copolymer chitosan-acrylamide graft copolymer.

[0033] The gel-like graft copolymer chitosan-acrylamide graft copolymer was crushed, purified with acetone, washed and dried with anhydrous ethanol, and then dried in a constant temperature drying oven until the quality was constant. Finally, the product was pulverized for later use.

[0034] Step 2: Add 5g of the pulverized chitosan-acrylamide graft copolymer prepared in Step 1 and 2.5g of oleic acid to 100ml of ethanol / water solution (40% by mass). Stir and react at 60℃ for 10h, then refrigerate at 4℃ to separate the lower precipitate. Place the separated product in 100ml of ethanol / water solution (40% by mass) and react at 95℃ for 4h to precipitate and obtain a solid-solid phase change material. After the reaction is complete, wash the solid-solid phase change material with ethanol and then dry it.

[0035] As shown in the table, the exothermic temperature of this solid-solid phase change material is 18.1℃, the endothermic temperature is -8.1℃, the melting enthalpy is 49.8 J / g, and the solidification enthalpy is 47.6 J / g.

[0036] Example 4: A method for preparing a solid-solid phase change material, comprising the following steps.

[0037] Step 1: In a constant temperature water bath at 40℃, add 5g of chitosan and 15g of acrylamide monomer to 100ml of 2% acetic acid solution, stir thoroughly to dissolve completely, remove oxygen by purging with nitrogen, add 0.06g of cerium ammonium nitrate under nitrogen protection, and react for 5h under sealed conditions to obtain a gel-like graft copolymer chitosan-acrylamide graft copolymer.

[0038] The gel-like graft copolymer chitosan-acrylamide graft copolymer was crushed, purified with acetone, washed and dried with anhydrous ethanol, and then dried in a constant temperature drying oven until the quality was constant. Finally, the product was pulverized for later use.

[0039] Step 2: Add 5g of the pulverized chitosan-acrylamide graft copolymer prepared in Step 1 and 2.5g of oleic acid to 100ml of ethanol / water solution (40% by mass). Stir and react at 60℃ for 10h, then refrigerate at 4℃ to separate the lower precipitate. Place the separated product in 100ml of ethanol / water solution (40% by mass) and react at 90℃ for 5h to precipitate and obtain a solid-solid phase change material. After the reaction is complete, wash the solid-solid phase change material with ethanol and then dry it.

[0040] As shown in the table, the exothermic temperature of this solid-solid phase change material is 18.2℃, the endothermic temperature is -7.9℃, the melting enthalpy is 40.3J / g, and the solidification enthalpy is 38.1 J / g.

[0041] Example Heat release temperature (°C) Heat absorption temperature (°C) Enthalpy of fusion (J / g) Enthalpy of solidification (J / g) 1 18.1 -7.4 30.2 32.3 2 17.9 -7.9 45.1 43.8 3 18.1 -8.1 49.8 47.6 4 18.2 -7.9 40.3 38.1

[0042] The test results of the phase change materials prepared in each embodiment are shown in the table above.

Claims

1. A method for preparing a solid-solid phase change material, characterized in that: Follow these steps Step 1: Chitosan and acrylamide react in an acetic acid solution to obtain a chitosan-acrylamide graft copolymer; Step 2: In an ethanol solution, the chitosan-acrylamide graft copolymer reacts with oleic acid to obtain a solid-solid phase change material.

2. The method for preparing a solid-solid phase change material according to claim 1, characterized in that: In step one, before the reaction between chitosan and acrylamide, the mass ratio of acrylamide to chitosan is 3-5; in step two, before the reaction between the chitosan-acrylamide graft copolymer and oleic acid, the mass ratio of the chitosan-acrylamide graft copolymer to oleic acid is 2-4.

3. The method for preparing a solid-solid phase change material according to claim 1, characterized in that: In step one, the mass percentage concentration of the acetic acid solution is 1-3%; in step two, the mass percentage concentration of the ethanol solution is 10-90%.

4. The method for preparing a solid-solid phase change material according to claim 1, characterized in that: In step one, the reaction conditions for chitosan and acrylamide are as follows: under nitrogen protection in a sealed reactor vessel, cerium ammonium nitrate initiator is added, and the reaction is carried out in a constant temperature water bath at 40-50°C for 3-6 hours. The resulting chitosan-acrylamide graft copolymer is a gel-like substance.

5. The method for preparing a solid-solid phase change material according to claim 4, characterized in that: Before the reaction between chitosan and acrylamide, the mass of cerium ammonium nitrate initiator added is 0.2 to 0.4% of the total mass of acrylamide and chitosan.

6. The method for preparing a solid-solid phase change material according to claim 1, characterized in that: In step two, the chitosan-acrylamide graft copolymer used to react with oleic acid is obtained by crushing, purifying with acetone, washing with anhydrous ethanol, and drying the chitosan-acrylamide graft copolymer prepared in step one until the mass is constant.

7. The method for preparing a solid-solid phase change material according to claim 1, characterized in that: In step two, the reaction conditions between the chitosan-acrylamide graft copolymer and oleic acid are as follows: the reaction is stirred at a first temperature, and the product is separated by refrigeration at 4°C; under vacuum conditions, the product is reacted again in an ethanol solution at a second temperature to obtain a solid-solid phase change material.

8. The method for preparing a solid-solid phase change material according to claim 7, characterized in that: The first temperature is 50-70℃, and the reaction time is 8-10h. The second temperature is 80-100℃, and the reaction time is 2-6h.

9. The application of a solid-solid phase change material prepared by the method described in claim 1, characterized in that: Solid-solid phase change materials are added to asphalt concrete or cement concrete materials used for road paving.

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