Preparation method of anionic polymerization nylon 6-based flexible solid-solid phase change material

Abstract

The invention discloses a preparation method of an anionic polymerization nylon 6-based flexible solid-solid phase change material, which is characterized in that caprolactam is used as a reaction monomer, and a macromolecular activator containing an isocyanate-terminated group is prepared by utilizing addition reaction of an active terminal hydroxyl group on a polyethylene glycol molecular chain and an isocyanate group at room temperature; the macromolecular activator has an electrophilic characteristic, can be subjected to nucleophilic reaction with caprolactam anions to become a chain-initiated active center, and initiates ring opening polymerization of the caprolactam anions to form nylon 6, so that a phase change component polyethylene glycol molecular chain is introduced into a nylon 6 molecular system to prepare a nylon 6-polyethylene glycol copolymer, namely a flexible solid-solid phase change material. The polyethylene glycol-isocyanate macromolecular activator can properly reduce the anionic polymerization reaction process and prolong the safe operation time of polymerization, the crystallization capacity and crystallinity of nylon 6 are reduced by introducing polyethylene glycol, and meanwhile, the nylon 6 is endowed with good flexibility by a large number of polyether chain segments with flexible structures on a polyethylene glycol molecular chain.

Description

Technical Field

[0001] The invention belongs to the field of polymer material synthesis, and in particular relates to a method for preparing a flexible solid-solid phase change material. Background Art

[0002] As the global energy crisis intensifies, phase change materials (PCMs) have attracted much attention in the field of energy conservation and thermal management due to their efficient latent heat storage / release capabilities. Organic PCMs can store and release thermal energy at a higher storage density by liquefying and solidifying within a small temperature difference, which is very attractive in thermal energy storage and thermal protection. In addition, they can also be used as thermal interface materials for thermal management. Among different types of PCMs, solid-liquid phase change materials such as paraffin, fatty acids and polyethylene glycol have attracted attention due to their effective energy storage capabilities. However, problems such as liquid leakage and volume expansion during phase change limit their application. The stability of solid-liquid PCMs has been improved by physically encapsulating them into core-shell structures, 3D aerogel networks and cross-linked skeletons, but the leakage risk at high temperatures remains a major challenge due to their liquid properties.

[0003] A variety of materials are used as carriers for encapsulating phase change materials to form relatively stable composite phase change materials. Zhao et al., Energy & Buildings, 2018, 158, 1049-1062, used bioporous carbon (BPC) to encapsulate polyethylene glycol (PEG) to prepare a shaped composite phase change material. PEG was evenly distributed in the matrix material and its mass fraction was about 85%. After heating at 80°C for 40 hours, it could still maintain its morphological stability; Ding Ze et al., Polymer Materials Science and Engineering, 2019, 35(2):176-179, used an emulsification method to emulsify EPDM rubber and paraffin, and then prepared a shaped phase change material by vulcanization and hot pressing. Solid-solid phase change exhibited by solid-solid phase change materials (SSPCMs) during heating and cooling cycles has become a promising alternative to fundamentally solve these problems. In recent years, related research aimed at discovering shape-stable polymer composites has attracted much attention. Wang et al., Advanced Functional Materials, 2024, 2420042, used a synergistic catalytic strategy to synthesize PEG-PVEG copolymers with different vinyl contents, and generated new cross-linked PEG-based SSPCMs through thiol photocrosslinking reaction. These PCMs have excellent shape stability and significant energy storage capacity, with a latent heat of up to 128.3 J / g. Wang et al., Advanced Materials, 2024, 36, 2309723, used a multiple hydrogen bonding strategy to synthesize supramolecular solid-solid phase change materials with polyethylene glycol (PEG) as a phase change energy storage functional segment and reacted with isocyanate for thermal energy storage and lithium-ion battery thermal management research, with a phase change enthalpy of 142.5 J / g. Chinese patent CN202211522637.8 discloses a cuttable solid-solid phase change material and a preparation method thereof. A polyurethane polymer is prepared by chemical synthesis, and the polymer is combined with a delignified wood skeleton by vacuum impregnation and chemical crosslinking. The obtained composite material is subjected to solvent evaporation and drying, and finally a cuttable solid-solid phase change material is obtained. Chinese patent CN202311516226.2 discloses a highly thermally conductive and flexible solid-solid phase change material and a preparation method thereof. By adding hexamethylene diisocyanate as a hard chain, the grafted polyethylene glycol can be stabilized, and the phase change morphology of the phase change component is changed from solid-liquid phase change to solid-solid phase change. At present, the method for preparing polyethylene glycol solid-solid phase change material is basically based on the polyurethane synthesis method. There is little research on the synthesis of solid-solid phase change materials using a new polymer reaction system, and further research is needed.

[0004] Anionic polymerization of nylon 6 is formed by reaction using isocyanate as an activator. Therefore, we can start with the molecular design of the activator and introduce the phase change component polyethylene glycol into the nylon system. By utilizing the characteristics of rapid reaction of terminal hydroxyl groups with isocyanate groups, we can prepare macromolecular activators with different structures, and initiate the polymerization of caprolactam monomers to prepare nylon 6-polyethylene glycol copolymers, while achieving the preparation of flexible solid-solid phase change materials and the toughening of nylon 6. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing an anionic polymerization nylon 6-based flexible solid-solid phase change material in view of the deficiencies of the prior art. The method is characterized in that caprolactam is used as a reaction monomer, and a macromolecular activator containing a terminal isocyanate group is prepared by the addition reaction of the active terminal hydroxyl group on the polyethylene glycol molecular chain and the isocyanate group at room temperature, and the macromolecular activator reacts with the caprolactam anion to become the active center of chain initiation, and initiates the ring-opening polymerization of the caprolactam anion to form nylon 6, thereby introducing the phase change component polyethylene glycol molecular chain into the nylon 6 molecular system to prepare a nylon 6-polyethylene glycol copolymer, i.e., a flexible solid-solid phase change material. The polyethylene glycol-isocyanate macromolecular activator can appropriately reduce the anionic polymerization process and prolong the safe operation time of polymerization. The introduction of polyethylene glycol reduces the crystallization ability and crystallinity of nylon 6. At the same time, a large number of polyether segments with flexible structures on the polyethylene glycol molecular chain give nylon 6 good flexibility. In the nylon 6-polyethylene glycol copolymer, polyethylene glycol is grafted onto the nylon 6 molecular chain. On the other hand, the entanglement between the molecules of the copolymer system jointly restricts the polyethylene glycol phase change component to the molecular chain. When the phase change occurs, the polyethylene glycol remains non-leaking, realizing the solid-solid phase change characteristics. By changing the molecular weight and dosage of polyethylene glycol, the structure of the macromolecular activator is changed, and finally the molecular structure of the polymerized nylon 6 is affected, realizing the mechanical strength, toughness and phase change enthalpy regulation of the solid-solid phase change material.

[0006] The object of the present invention is achieved by the following technical scheme, wherein the raw material fractions are all mass fractions unless otherwise specified.

[0007] A method for preparing anionic polymerized nylon 6-based flexible solid-solid phase change material, characterized in that the main raw materials of the phase change material are composed of the following components, calculated by mass fraction: Caprolactam 85 parts 8-35 parts of polyethylene glycol Isocyanate compound 0.1-2.5 parts Catalyst 0.04-5 parts Wherein, the molecular weight of the polyethylene glycol is 4000-20000 g / mol; The catalyst is any one of sodium hydroxide, potassium hydroxide, sodium ethoxide, and sodium sulfide; The isocyanate compound is any one of 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4',4''-triphenylmethane triisocyanate, and hexamethylene diisocyanate; The preparation method of the anionic polymerized nylon 6-based flexible solid-solid phase change material comprises the following steps: Synthesis of Polyethylene Glycol-Isocyanate Macromolecular Activator At room temperature, take 0.1-2.5 parts of isocyanate compound and put it into a reaction bottle, dissolve 8-35 parts of polyethylene glycol with a molecular weight of 4000-20000 g / mol in toluene at a concentration of 30wt%, add it into a constant pressure funnel, slowly add dropwise to react, continue stirring for 0.5-3 h after the addition is completed to complete the reaction, and obtain a polyethylene glycol-isocyanate macromolecular activator for standby use.

[0008] Preparation of nylon 6-based flexible solid-solid phase change materials 85 parts of caprolactam monomer are put into a reaction kettle, heated to 125-140°C to melt the monomer, the glass bottle mouth is completely sealed with vacuum silicone grease and then vacuumed, the vacuum is maintained to remove water for 10-30 minutes, and then the vacuum is released. After the temperature in the kettle rises, 0.04-5 parts of catalyst are added, and the reaction system is quickly re-distilled under reduced pressure for 10-30 minutes, and then the exhaust is stopped, the temperature is raised to 130-160°C, and polyethylene glycol-isocyanate macromolecular activator is added. After stirring evenly, vacuum is applied for 2-10 minutes, the toluene solvent is removed, and the mixture is poured into a preheated mold and anion polymerized for 40-200 minutes. The mold is opened and the sample is taken out to obtain a nylon 6-polyethylene glycol copolymer, that is, a nylon 6-based flexible solid-solid phase change material.

[0009] The present invention has the following advantages: In the reaction process of anionic polymerization of nylon 6, polyethylene glycol is used as a phase change component and a modifier at the same time, and reacts with isocyanate to generate a macromolecular activator to participate in polymerization, thereby grafting polyethylene glycol on the nylon 6 molecular chain. The macromolecular activator is a macromolecular compound with an isocyanate group as the active center, with a longer molecular chain and a larger molecular weight. Its long chain effect and steric hindrance effect reduce its initiation reaction activity, which is conducive to appropriately extending the safe operation time of the anionic polymerization reaction and avoiding the disadvantage of immediate polymerization after adding the isocyanate co-catalyst; the introduction of polyethylene glycol chain segments increases the entanglement of the molecular chains of the copolymer system, and consumes and absorbs the impact energy through the movement of the flexible chain segments of polyethylene glycol itself and the destruction of a large number of entanglement points on the molecular chain, and simultaneously realizes a significant toughening effect on nylon 6. By changing the molecular weight and dosage of polyethylene glycol, the structure of the macromolecular activator is changed, and the mechanical strength, toughness and phase change enthalpy regulation of the solid-solid phase change material are finally realized. The preparation method of the present invention is simple, and solid-solid phase change and toughening of nylon 6 are realized at the same time, which has certain advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is the reaction structure of polyethylene glycol-isocyanate macromolecular activator and nylon 6-based solid-solid phase change material. DETAILED DESCRIPTION

[0011] The present invention is further described below through specific examples. It should be noted that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make non-essential improvements and adjustments to the present invention based on the contents of the present invention described above. Example

[0012] Synthesis of Polyethylene Glycol-Isocyanate Macromolecular Activator At room temperature, take 2.5 parts of 2,4-toluene diisocyanate and put it into a reaction bottle, dissolve 8 parts of polyethylene glycol with a molecular weight of 4000g / mol in toluene at a concentration of 30wt%, add it into a constant pressure funnel, and slowly add it dropwise to react. After the addition is completed, continue stirring for 0.5 h to complete the reaction to obtain a polyethylene glycol-isocyanate macromolecular activator for standby use.

[0013] Preparation of nylon 6-based flexible solid-solid phase change materials 85 parts of caprolactam monomer were put into a reaction kettle and heated to 130°C to melt the monomer. The glass bottle mouth was completely sealed with vacuum silicone grease and then evacuated. The vacuum was maintained to remove water for 20 minutes, and then the vacuum was released. After the temperature in the kettle rose, 0.1 parts of sodium hydroxide were added, and the reaction system was quickly distilled under reduced pressure for 10 minutes again. Then the exhaust was stopped, the temperature was raised to 135°C, and polyethylene glycol-isocyanate macromolecular activator was added. After stirring evenly, the vacuum was evacuated for 5 minutes, the toluene solvent was removed, and the mixture was poured into a preheated mold. Anionic polymerization was carried out for 50 minutes, and the mold was opened to take out the sample to obtain nylon 6-polyethylene glycol copolymer, that is, nylon 6-based flexible solid-solid phase change material.

[0014] The nylon 6-based flexible solid-solid phase change material has a tensile strength of 52 MPa, an elongation at break of 580%, and an impact strength of 38 kJ / m 2 , a phase change enthalpy of 73 J / g, excellent thermal stability above the phase change temperature, no leakage, and maintaining its energy storage capacity after 300 heating-cooling cycles. Example

[0015] At room temperature, take 2 parts of 2,4-toluene diisocyanate and put it into a reaction bottle, dissolve 12 parts of polyethylene glycol with a molecular weight of 6000 g / mol in toluene at a concentration of 30wt%, add it into a constant pressure funnel, and slowly add it dropwise to react. After the addition is completed, continue stirring for 1 hour to complete the reaction to obtain a polyethylene glycol-isocyanate macromolecular activator for standby use.

[0016] Preparation of nylon 6-based flexible solid-solid phase change materials 85 parts of caprolactam monomer were put into a reaction kettle and heated to 130°C to melt the monomer. The mouth of the glass bottle was completely sealed with vacuum silicone grease and then evacuated. The vacuum was maintained to remove water for 30 minutes, and then the vacuum was released. After the temperature in the kettle rose, 0.15 parts of potassium hydroxide were added, and the reaction system was quickly distilled under reduced pressure for 20 minutes again. Then the exhaust was stopped, the temperature was raised to 140°C, and polyethylene glycol-isocyanate macromolecular activator was added. After stirring evenly, the vacuum was evacuated for 6 minutes, the toluene solvent was removed, and the mixture was poured into a preheated mold and anion polymerized for 60 minutes. The mold was opened and the sample was taken out to obtain nylon 6-polyethylene glycol copolymer, that is, nylon 6-based flexible solid-solid phase change material.

[0017] The tensile strength of the nylon 6-based flexible solid-solid phase change material is 41 MPa, the elongation at break is 649%, and the impact strength is 43 kJ / m 2 , a phase change enthalpy of 82 J / g, excellent thermal stability above the phase change temperature, no leakage, and maintaining its energy storage capacity after 300 heating-cooling cycles. Example

[0018] At room temperature, take 1.6 parts of 4,4'-diphenylmethane diisocyanate and put it into a reaction bottle, dissolve 18 parts of polyethylene glycol with a molecular weight of 10000 g / mol in toluene at a concentration of 30wt%, add it into a constant pressure funnel, and slowly add dropwise to react. After the addition is completed, continue stirring for 1.5 hours to complete the reaction to obtain a polyethylene glycol-isocyanate macromolecular activator for standby use.

[0019] Preparation of nylon 6-based flexible solid-solid phase change materials 85 parts of caprolactam monomer were put into a reaction kettle and heated to 135°C to melt the monomer. The glass bottle mouth was completely sealed with vacuum silicone grease and then evacuated. The vacuum was maintained to remove water for 30 minutes, and then the vacuum was released. After the temperature in the kettle rose, 1 part of sodium ethoxide was added, and the reaction system was quickly re-distilled under reduced pressure for 18 minutes. Then the exhaust was stopped, the temperature was raised to 135°C, and polyethylene glycol-isocyanate macromolecular activator was added. After stirring evenly, vacuum was evacuated for 8 minutes, the toluene solvent was removed, and the mixture was poured into a preheated mold. Anionic polymerization was carried out for 90 minutes, and the mold was opened to take out the sample to obtain nylon 6-polyethylene glycol copolymer, that is, nylon 6-based flexible solid-solid phase change material.

[0020] The tensile strength of the nylon 6-based flexible solid-solid phase change material is 32 MPa, the elongation at break is 744%, and the impact strength is 51 kJ / m 2 , a phase change enthalpy of 101 J / g, excellent thermal stability above the phase change temperature, no leakage, and maintaining its energy storage capacity after 300 heating-cooling cycles. Example

[0021] At room temperature, take 2 parts of 4,4',4''-triphenylmethane triisocyanate and put it into a reaction bottle, dissolve 20 parts of polyethylene glycol with a molecular weight of 6000 g / mol in toluene at a concentration of 30wt%, add it into a constant pressure funnel, and slowly add dropwise to react. After the addition is completed, continue stirring for 2 hours to complete the reaction to obtain a polyethylene glycol-isocyanate macromolecular activator for standby use.

[0022] Preparation of nylon 6-based flexible solid-solid phase change materials 85 parts of caprolactam monomer were put into a reaction kettle and heated to 140°C to melt the monomer. The mouth of the glass bottle was completely sealed with vacuum silicone grease and then evacuated. The vacuum was maintained to remove water for 30 minutes, and then the vacuum was released. After the temperature in the kettle rose, 1.5 parts of sodium hydroxide were added, and the reaction system was quickly distilled under reduced pressure for 30 minutes again. Then the exhaust was stopped, the temperature was raised to 140°C, and polyethylene glycol-isocyanate macromolecular activator was added. After stirring evenly, the evacuation was carried out for 10 minutes, the toluene solvent was removed, and the mixture was poured into a preheated mold. Anionic polymerization was carried out for 100 minutes, and the mold was opened to take out the sample to obtain nylon 6-polyethylene glycol copolymer, that is, nylon 6-based flexible solid-solid phase change material.

[0023] The tensile strength of the nylon 6-based flexible solid-solid phase change material is 27 MPa, the elongation at break is 826%, and the impact strength is 58 kJ / m 2 , a phase change enthalpy of 132 J / g, excellent thermal stability above the phase change temperature, no leakage, and maintaining its energy storage capacity after 300 heating-cooling cycles. Example

[0024] At room temperature, take 2 parts of hexamethylene diisocyanate and put it into a reaction bottle, dissolve 30 parts of polyethylene glycol with a molecular weight of 20,000 g / mol in toluene at a concentration of 30wt%, add it into a constant pressure funnel, and slowly add dropwise to react. After the addition is completed, continue stirring for 3 hours to complete the reaction to obtain a polyethylene glycol-isocyanate macromolecular activator for standby use.

[0025] Preparation of nylon 6-based flexible solid-solid phase change materials 85 parts of caprolactam monomer were put into a reaction kettle and heated to 140°C to melt the monomer. The glass bottle mouth was completely sealed with vacuum silicone grease and then evacuated. The vacuum was maintained to remove water for 30 minutes, and then the vacuum was released. After the temperature in the kettle rose, 2 parts of sodium sulfide were added, and the reaction system was quickly distilled under reduced pressure for 30 minutes again. Then the exhaust was stopped, the temperature was raised to 150°C, and polyethylene glycol-isocyanate macromolecular activator was added. After stirring evenly, the vacuum was evacuated for 10 minutes, the toluene solvent was removed, and the mixture was poured into a preheated mold. Anionic polymerization was carried out for 120 minutes, and the mold was opened to take out the sample to obtain nylon 6-polyethylene glycol copolymer, that is, nylon 6-based flexible solid-solid phase change material.

[0026] The tensile strength of the nylon 6-based flexible solid-solid phase change material is 22 MPa, the elongation at break is 844%, and the impact strength is 63 kJ / m 2 , a phase change enthalpy of 146 J / g, excellent thermal stability above the phase change temperature, no leakage, and maintaining its energy storage capacity after 300 heating-cooling cycles.

[0027] In summary, after the polyethylene glycol-isocyanate macromolecular activator is introduced into the embodiment of the present invention, the nylon 6-based solid-solid phase change material has higher tensile strength, elongation at break and impact strength, as well as higher phase change enthalpy, excellent thermal stability above the melting point of polyethylene glycol, and no leakage occurs.

[0028] The above embodiments describe the specific contents of the present invention in detail, but the present invention is not limited to the embodiments, and those skilled in the art can make equivalent substitutions, which should be included in the protection scope of the present invention.

Claims

1. A method for preparing anionic polymerized nylon 6-based flexible solid-solid phase change material, characterized in that The main raw materials of the phase change material are composed of the following components, calculated by mass: Caprolactam 85 parts 8-35 parts of polyethylene glycol Isocyanate compound 0.1-2.5 parts Catalyst 0.04-5 parts Wherein, the molecular weight of the polyethylene glycol is 4000-20000 g / mol; The catalyst is any one of sodium hydroxide, potassium hydroxide, sodium ethoxide, and sodium sulfide; The isocyanate compound is any one of 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4',4''-triphenylmethane triisocyanate, and hexamethylene diisocyanate; The preparation method of the anionic polymerized nylon 6-based flexible solid-solid phase change material comprises the following steps: Synthesis of Polyethylene Glycol-Isocyanate Macromolecular Activator At room temperature, 0.1-2.5 parts of an isocyanate compound are put into a reaction bottle, 8-35 parts of polyethylene glycol with a molecular weight of 4000-20000 g / mol are dissolved in toluene at a concentration of 30wt%, added to a constant pressure funnel, and slowly added dropwise to react. After the addition is completed, stirring is continued for 0.5-3 h to complete the reaction, to obtain a polyethylene glycol-isocyanate macromolecular activator for standby use; Preparation of nylon 6-based flexible solid-solid phase change materials 85 parts of caprolactam monomer are put into a reaction kettle, heated to 125-140°C to melt the monomer, the glass bottle mouth is completely sealed with vacuum silicone grease and then vacuumed, the vacuum is maintained to remove water for 10-30 minutes, and then the vacuum is released. After the temperature in the kettle rises, 0.04-5 parts of catalyst are added, and the reaction system is quickly re-distilled under reduced pressure for 10-30 minutes, and then the exhaust is stopped, the temperature is raised to 130-160°C, and polyethylene glycol-isocyanate macromolecular activator is added. After stirring evenly, vacuum is applied for 2-10 minutes, the toluene solvent is removed, and the mixture is poured into a preheated mold and anion polymerized for 40-200 minutes. The mold is opened and the sample is taken out to obtain a nylon 6-polyethylene glycol copolymer, that is, a nylon 6-based flexible solid-solid phase change material.

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