A bio-based composite thermal insulation filling material and a preparation method thereof

Abstract

This invention relates to the field of thermal insulation filling material preparation, specifically to a bio-based composite thermal insulation filling material and its preparation method. This invention synthesizes a phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer, simultaneously introducing compatibility units, phase change energy storage units, and reactive sites; then, it prepares furan-modified polyhydroxy fatty acid ester prepolymer and maleimide-modified fluorinated hollow silica aerogel nanospheres. Through dynamic Diels-Alder covalent bonds between furan and maleimide, a fully bio-based interpenetrating cross-linked network is constructed, achieving in-situ covalent anchoring of the aerogel microspheres. The material of this invention simultaneously possesses excellent antibacterial, flame-retardant, and biodegradable properties, and can be widely used in thermal insulation filling fields such as clothing, home textiles, and outdoor equipment.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation filling material preparation, specifically to a bio-based composite thermal insulation filling material and its preparation method. Background Technology

[0002] Currently, mainstream bio-based thermal insulation materials are mainly divided into natural biopolymer materials and synthetic bio-based polyester materials. Natural biopolymer materials, such as wool, silk, and cellulose, are skin-friendly and biodegradable, but when they absorb water in a wet state, their pores become filled with water, increasing their thermal conductivity. This results in a loss of insulation properties and makes them prone to mold growth and poor compression resilience. Synthetic bio-based polyester materials, such as polylactic acid (PLA) and polyhydroxyalkanoates (PHA), have high mechanical strength and are biodegradable, but they are highly crystalline and brittle, making it difficult to form a stable three-dimensional, fluffy porous structure. They also have extremely poor compatibility with natural polymers, resulting in weak interfacial bonding after physical blending, leading to delamination and shedding, and failing to balance resilience and insulation stability.

[0003] Existing technologies for modifying bio-based thermal insulation materials involve hollow spinning and physical foaming to create a fluffy structure, but the pores are prone to collapse, resulting in poor compression resistance and water washability. Alternatively, physical doping with silica aerogels or phase change microcapsules can improve thermal insulation, but aerogels have poor compatibility with organic matrices, are prone to pulverization, migration, and detachment, and are lost in large quantities after washing, leading to a rapid decline in thermal insulation. Paraffin-based phase change microcapsules, on the other hand, suffer from problems such as easy wall material damage and leakage of phase change materials, resulting in a high risk of loss of temperature regulation function. Furthermore, defects at the interface between the microcapsules and the matrix can severely degrade the mechanical properties of the material.

[0004] Therefore, inventing a composite thermal insulation filling material with bio-based compatibility, thermal stability, mechanical durability, and multifunctional integration has great market application prospects. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a bio-based composite thermal insulation filling material and its preparation method. This invention synthesizes a phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer, simultaneously introducing compatibility units, phase change energy storage units, and reactive sites. Then, furan-modified polyhydroxy fatty acid ester prepolymer and maleimide-modified fluorinated hollow silica aerogel nanospheres are prepared. Through dynamic Diels-Alder covalent bonds between furan and maleimide, a fully bio-based interpenetrating cross-linked network is constructed, achieving in-situ covalent anchoring of the aerogel microspheres. The material of this invention also possesses excellent antibacterial, flame-retardant, and biodegradable properties, and can be widely used in thermal insulation filling fields such as clothing, home textiles, and outdoor equipment.

[0006] This invention discloses a bio-based composite thermal insulation filling material, which is composed of the following components in parts by weight: 40-65 parts of phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer; 10-35 parts of furan-modified polyhydroxy fatty acid ester prepolymer; 1-10 parts of maleimide-modified fluorinated hollow silica aerogel nanospheres; 0.1-0.6 parts of catalyst; 1-2 parts of antioxidant.

[0007] Preferably, the phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer has phenol-hydroxylated chitosan as the main chain, with end-carboxyl polylactic acid prepolymer covalently grafted via amide bonds and stearic acid phase change units covalently grafted via ester bonds.

[0008] Preferably, the number average molecular weight of the carboxyl-terminated polylactic acid prepolymer is 5000-10000, and the stearic acid is of bio-based origin.

[0009] Preferably, the number average molecular weight of the furan-modified polyhydroxy fatty acid ester prepolymer is 10,000 to 20,000.

[0010] Preferably, the furan-modified polyhydroxy fatty acid ester prepolymer has furan groups grafted onto its end groups, with a furan group grafting rate of ≥85%.

[0011] Preferably, the maleimide-modified fluorinated hollow silica aerogel nanospheres have a particle size of 200~450nm, a hollow pore size of 100~200nm, a surface maleimide group grafting rate of ≥90%, and a water contact angle of ≥135°.

[0012] Preferably, the catalyst is triethylamine.

[0013] Preferably, the antioxidant is tea polyphenols.

[0014] This invention also discloses a method for preparing a bio-based composite thermal insulation filling material, the method comprising the following steps: Preparation of S1 phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer: 10 parts by weight of chitosan were added to 100 parts by weight of solvent and frozen at -20℃ and thawed at 25℃ three times until completely dissolved. Then, 3-4 parts by weight of 3,4-dihydroxybenzaldehyde were added, and the temperature was raised to 40-50℃. The mixture was stirred for 4-6 hours under nitrogen protection. Then, 0.5-1 parts by weight of sodium borohydride were added, and the mixture was stirred for another 2-3 hours. After the reaction was completed, the pH was adjusted to 7, and the mixture was precipitated with anhydrous ethanol, filtered, washed, and vacuum dried for 12 hours to obtain phenol-hydroxylated chitosan. 100 parts by weight of L-lactide, 2-4.5 parts by weight of 1,4-succinic acid, and 0.1-0.35 parts by weight of stannous octoate were added to a sealed reactor, purged with nitrogen, and heated to 130-140℃. The mixture was then stirred and melted for reaction. After the reaction was completed, the mixture was cooled to 25°C, dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and vacuum dried at 45°C for 10 h to obtain a carboxyl-terminated polylactic acid prepolymer with a number average molecular weight of 5000-10000. 10 parts by weight of phenol-hydroxylated chitin, 30-55 parts by weight of the carboxyl-terminated polylactic acid prepolymer, 8-13 parts by weight of stearic acid, 3-5.5 parts by weight of N,N'-dicyclohexylcarbodiimide, and 0.5-1 parts by weight of 4-dimethylaminopyridine were added to 200 parts by weight of N,N-dimethylformamide. The mixture was heated to 60-70°C under nitrogen protection and stirred for 12-17 h. After the reaction was completed, the reaction solution was poured into anhydrous ethanol to precipitate, filtered, washed with anhydrous ethanol, and vacuum dried at 50°C for 12 h to obtain a phenol-hydroxylated chitin-g-polylactic acid-g-stearic acid graft copolymer. Preparation of S2 furan-modified polyhydroxy fatty acid ester prepolymer: 100 parts by weight of polyhydroxy fatty acid ester with a number average molecular weight of 10,000-20,000, 5-10 parts by weight of furfuryl alcohol, and 0.5-1 parts by weight of p-toluenesulfonic acid were added to 300 parts by weight of toluene. The mixture was heated to 110-120℃ under nitrogen protection and refluxed for 6-8 hours to remove water. After the reaction was completed, toluene was removed by vacuum distillation, the product was dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 hours to obtain furan-modified polyhydroxy fatty acid ester prepolymer. Preparation of S3 maleimide-modified fluorinated hollow silica aerogel nanospheres: 10 parts by weight of tetraethyl orthosilicate, 2-4.5 parts by weight of tridecafluorooctyltriethoxysilane, 100 parts by weight of anhydrous ethanol, 20 parts by weight of deionized water, and 2-3 parts by weight of 25% ammonia solution were mixed and stirred at room temperature for 2-3 hours. Then, 5-10 parts by weight of polystyrene microsphere emulsion with a solid content of 10 wt% and a particle size of 200-300 nm were added, and the mixture was stirred for another 4-5 hours. After the reaction was complete, the mixture was centrifuged and washed with anhydrous ethanol. The template agent was removed by calcination at 600℃ for 2 hours to obtain fluorinated hollow silica aerogel nanospheres. 10 parts by weight of the fluorinated hollow silica aerogel nanospheres were added to 100 parts by weight of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 2-4.5 parts by weight of N-(2-aminoethyl)maleimide were added, and the mixture was heated to 50-60℃ and stirred for 4-5 hours. The mixture was then centrifuged, dissolved in anhydrous ethanol, and vacuum dried at 40℃ for 12 hours to obtain maleimide-modified fluorinated hollow silica aerogel nanospheres. Preparation of S4 composite thermal insulation filling material: Phenolic hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer and furan-modified polyhydroxy fatty acid ester prepolymer were added to a 1:1 volume ratio N,N-dimethylformamide / tetrahydrofuran mixed solvent and stirred at room temperature until completely dissolved to obtain a matrix mixture with a solid content of 15-20 wt%. Maleimide-modified fluorinated hollow silica aerogel nanospheres were added to the matrix mixture and ultrasonically dispersed at room temperature for 30 min at 200 W to obtain a dispersion. A catalyst and antioxidant were added to the dispersion and stirred at room temperature for 30 min to obtain a casting solution. The casting solution was poured into a flat mold to form continuous fibers, placed in a vacuum oven, heated to 90-100℃, and kept at that temperature for 4-5 h to obtain a crosslinked preform. The crosslinked preform was washed with anhydrous ethanol and then placed in a freeze dryer and freeze-dried at -55℃ for 24 h to obtain a bio-based composite thermal insulation filling material.

[0015] Preferably, in step S1, the solvent is an aqueous solution containing 8 wt% sodium hydroxide and 12 wt% urea.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a bio-based composite thermal insulation filling material and its preparation method, which has the following characteristics: (1) The present invention uses covalently anchored fluorinated hollow silica aerogel nanospheres, whose nano-closed-pore structure can effectively block air convection and heat conduction. The thermal conductivity of the material can be as low as 0.021 W / (mK), which is better than conventional PLA fiber, cotton and other materials. At the same time, fluorine modification gives the material superhydrophobicity, with a water contact angle ≥135°. The pores of the material will not be filled by water in the wet state, and the heat retention rate is ≥91%, which solves the problem of unstable heat retention of natural bio-based materials in the wet state.

[0017] (2) In this invention, stearic acid phase change units are covalently grafted onto the matrix molecular chain via ester bonds. Unlike the physical doping phase change microcapsules of the prior art, this invention completely avoids the problems of leakage and migration of phase change materials. The phase change enthalpy of the material is ≥85J / g, which can achieve solid-liquid phase change in the human body's comfortable temperature range. It can achieve active temperature regulation through heat absorption and heat release. Even when the ambient temperature fluctuates, it can maintain a stable warm feeling and improve the comfort of wearing.

[0018] (3) This invention constructs a fully bio-based interpenetrating cross-linked network through DA dynamic covalent bonds. The interpenetrating and entangled double network structure endows the material with excellent compression resistance and resilience. The compression resilience is ≥98%, and the resilience is still ≥95% after 500 compression cycles, which solves the inherent defects of PLA and other bio-based polyesters such as high brittleness and poor resilience. At the same time, the DA bond has thermal reversibility and can achieve self-repair through low temperature heat treatment at 80℃. After 50 standard water washes, the material retains ≥94% of its bulkiness and ≥92% of its heat retention, resulting in a long service life.

[0019] (4) In this invention, aerogel microspheres are covalently anchored in the cross-linked network through DA reaction. Stable chemical bonds are formed between the microspheres and the matrix, rather than physical adsorption, which solves the problems of easy powdering, migration, shedding and water washing of aerogel. After long-term use, it can still maintain a stable low thermal conductivity and the heat preservation performance has no significant decline.

[0020] (5) All matrix raw materials of this invention are derived from bio-based renewable resources. Chitin, PLA, PHA and stearic acid are all bio-based sources, with no petroleum-based raw materials added. Under 180-day composting conditions, the biodegradability rate is ≥90%, which meets environmental protection requirements. At the same time, phenolic hydroxylated chitin gives the material excellent antibacterial properties, with an inhibition rate of ≥99% against Escherichia coli and Staphylococcus aureus, without the need for additional antibacterial agents. Silica aerogel gives the material excellent flame retardant properties, with a limiting oxygen index (LOI) ≥32%, reaching the flame-retardant level, without the need for additional flame retardants, achieving an integrated effect of heat preservation, temperature regulation, resilience, washability, antibacterial, flame retardancy and biodegradability. Detailed Implementation

[0021] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0022] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0023] Example 1: A bio-based composite thermal insulation filling material, composed of the following components in parts by weight: 40 parts of phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer; 10 parts of furan-modified polyhydroxy fatty acid ester prepolymer; 1 part of maleimide-modified fluorinated hollow silica aerogel nanospheres; 0.1 parts of catalyst; 1 part of antioxidant. The phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer has phenol-hydroxylated chitosan as the main chain, with end-carboxyl polylactic acid prepolymer covalently grafted via amide bonds and stearic acid phase change units covalently grafted via ester bonds. The number average molecular weight of the end-carboxyl polylactic acid prepolymer is 5000, and the stearic acid is of bio-based origin. The number average molecular weight of the furan-modified polyhydroxy fatty acid ester prepolymer is 10000, with furan groups grafted at the ends, and the furan group grafting rate is ≥85%. The maleimide-modified fluorinated hollow silica aerogel nanospheres have a particle size of 200nm, a hollow pore size of 100nm, a surface maleimide group grafting rate of ≥90%, and a water contact angle of ≥135°. The catalyst is triethylamine, and the antioxidant is tea polyphenols.

[0024] A method for preparing a bio-based composite thermal insulation filling material includes the following steps: Preparation of S1 phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer: 10 parts by weight of chitosan were added to 100 parts by weight of solvent and frozen at -20℃ and thawed at 25℃ three times until completely dissolved. The solvent was an aqueous solution containing 8 wt% sodium hydroxide and 12 wt% urea. Then, 3-4 parts by weight of 3,4-dihydroxybenzaldehyde were added, and the temperature was raised to 40-50℃. The mixture was stirred and reacted under nitrogen protection for 4-6 hours. Then, 0.5 parts by weight of sodium borohydride were added, and the mixture was stirred and reacted for another 2-3 hours. After the reaction was completed, the pH was adjusted to 7, and the mixture was precipitated with anhydrous ethanol, filtered, washed, and vacuum dried for 12 hours to obtain phenol-hydroxylated chitosan. 100 parts by weight of L-lactide, 2 parts by weight of 1,4-succinic acid, and 0.1 parts by weight of stannous octoate were added to a sealed reactor. After nitrogen purging, the temperature was raised to 130℃ and stirred for 8 hours. After the reaction, the temperature was cooled to 25℃, dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 hours to obtain a carboxyl-terminated polylactic acid prepolymer with a number average molecular weight of 5000. 10 parts by weight of phenol-hydroxylated chitin, 30 parts by weight of the carboxyl-terminated polylactic acid prepolymer, 8 parts by weight of stearic acid, 3 parts by weight of N,N'-dicyclohexylcarbodiimide, and 0.5 parts by weight of 4-dimethylaminopyridine were added to 200 parts by weight of N,N-dimethylformamide. The temperature was raised to 60℃ under nitrogen protection and stirred for 12 hours. After the reaction, the reaction solution was poured into anhydrous ethanol to precipitate, filtered, washed with anhydrous ethanol, and dried under vacuum at 50℃ for 12 hours to obtain a phenol-hydroxylated chitin-g-polylactic acid-g-stearic acid graft copolymer. Preparation of S2 furan-modified polyhydroxy fatty acid ester prepolymer: 100 parts by weight of polyhydroxy fatty acid ester with a number average molecular weight of 10,000, 5 parts by weight of furfuryl alcohol, and 0.5-1 parts by weight of p-toluenesulfonic acid were added to 300 parts by weight of toluene. The mixture was heated to 110-120℃ under nitrogen protection and refluxed for 6 hours to remove water. After the reaction was completed, toluene was removed by vacuum distillation, the product was dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 hours to obtain furan-modified polyhydroxy fatty acid ester prepolymer. Preparation of S3 maleimide-modified fluorinated hollow silica aerogel nanospheres: 10 parts by weight of tetraethyl orthosilicate, 2 parts by weight of tridecafluorooctyltriethoxysilane, 100 parts by weight of anhydrous ethanol, 20 parts by weight of deionized water, and 2-3 parts by weight of 25% ammonia solution were mixed and stirred at room temperature for 2 hours. Then, 5-10 parts by weight of polystyrene microsphere emulsion with a solid content of 10 wt% and a particle size of 200 nm were added, and the mixture was stirred for another 4 hours. After the reaction was complete, the mixture was centrifuged and washed with anhydrous ethanol. The template agent was removed by calcination at 600℃ for 2 hours to obtain fluorinated hollow silica aerogel nanospheres. 10 parts by weight of the fluorinated hollow silica aerogel nanospheres were added to 100 parts by weight of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 2 parts by weight of N-(2-aminoethyl)maleimide were added, and the mixture was heated to 50℃ and stirred for 4 hours. After centrifugation and separation, the mixture was dried in anhydrous ethanol at 40℃ under vacuum for 12 hours to obtain maleimide-modified fluorinated hollow silica aerogel nanospheres. Preparation of S4 composite thermal insulation filling material: Phenolic hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer and furan-modified polyhydroxy fatty acid ester prepolymer were added to a 1:1 volume ratio N,N-dimethylformamide / tetrahydrofuran mixed solvent and stirred at room temperature until completely dissolved to obtain a matrix mixture with a solid content of 15wt%. Maleimide-modified fluorinated hollow silica aerogel nanospheres were added to the matrix mixture and ultrasonically dispersed at room temperature for 30 min at 200W to obtain a dispersion. A catalyst and antioxidant were added to the dispersion and stirred at room temperature for 30 min to obtain a casting solution. The casting solution was poured into a flat mold to form continuous fibers, placed in a vacuum oven, heated to 90℃, and kept at that temperature for 4 h to obtain a crosslinked preform. The crosslinked preform was washed with anhydrous ethanol and then placed in a freeze dryer and freeze-dried at -55℃ for 24 h to obtain a bio-based composite thermal insulation filling material.

[0025] Example 2: A bio-based composite thermal insulation filling material, composed of the following parts by weight: 45 parts of phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer; 15 parts of furan-modified polyhydroxy fatty acid ester prepolymer; 3 parts of maleimide-modified fluorinated hollow silica aerogel nanospheres; 0.2 parts of catalyst; 1.2 parts of antioxidant. The phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer has phenol-hydroxylated chitosan as the main chain, with end-carboxyl polylactic acid prepolymer covalently grafted via amide bonds and stearic acid phase change units covalently grafted via ester bonds. The number average molecular weight of the end-carboxyl polylactic acid prepolymer is 6000, and the stearic acid is of bio-based origin. The number average molecular weight of the furan-modified polyhydroxy fatty acid ester prepolymer is 12000, with furan groups grafted at the ends, and the furan group grafting rate is ≥85%. The maleimide-modified fluorinated hollow silica aerogel nanospheres have a particle size of 250 nm, a hollow pore size of 120 nm, a surface maleimide group grafting rate of ≥90%, and a water contact angle of ≥135°. The catalyst is triethylamine, and the antioxidant is tea polyphenols.

[0026] A method for preparing a bio-based composite thermal insulation filling material includes the following steps: Preparation of S1 phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer: 10 parts by weight of chitosan were added to 100 parts by weight of solvent and frozen at -20℃ and thawed at 25℃ three times until completely dissolved. The solvent was an aqueous solution containing 8 wt% sodium hydroxide and 12 wt% urea. Then, 3.2 parts by weight of 3,4-dihydroxybenzaldehyde were added, and the mixture was heated to 42℃ and stirred for 4.5 h under nitrogen protection. Then, 0.6 parts by weight of sodium borohydride were added, and the mixture was stirred for another 2.2 h. After the reaction was completed, the pH was adjusted to 7, and the mixture was precipitated with anhydrous ethanol, filtered, washed, and vacuum dried for 12 h to obtain phenol-hydroxylated chitosan. 100 parts by weight of L-lactide, 25 parts by weight of 1,4-succinic acid, and 0.15 parts by weight of stannous octoate were added to a closed reactor and stirred under nitrogen protection. After gas purging, the temperature was raised to 132℃ and stirred for 9 hours. After the reaction, the temperature was cooled to 25℃, dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 hours to obtain a carboxyl-terminated polylactic acid prepolymer with a number average molecular weight of 6000. 10 parts by weight of phenol-hydroxylated chitin, 35 parts by weight of the carboxyl-terminated polylactic acid prepolymer, 9 parts by weight of stearic acid, 3.5 parts by weight of N,N'-dicyclohexylcarbodiimide, and 0.6 parts by weight of 4-dimethylaminopyridine were added to 200 parts by weight of N,N-dimethylformamide. The temperature was raised to 62℃ under nitrogen protection and stirred for 13 hours. After the reaction, the reaction solution was poured into anhydrous ethanol to precipitate, filtered, washed with anhydrous ethanol, and dried under vacuum at 50℃ for 12 hours to obtain a phenol-hydroxylated chitin-g-polylactic acid-g-stearic acid graft copolymer. Preparation of S2 furan-modified polyhydroxy fatty acid ester prepolymer: 100 parts by weight of polyhydroxy fatty acid ester with a number average molecular weight of 12000, 6 parts by weight of furfuryl alcohol, and 0.6 parts by weight of p-toluenesulfonic acid were added to 300 parts by weight of toluene. The mixture was heated to 112°C under nitrogen protection and refluxed for 6.5 h to remove water. After the reaction was completed, toluene was removed by vacuum distillation, the product was dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45°C for 10 h to obtain furan-modified polyhydroxy fatty acid ester prepolymer. Preparation of S3 maleimide-modified fluorinated hollow silica aerogel nanospheres: 10 parts by weight of tetraethyl orthosilicate, 25 parts by weight of tridecafluorooctyltriethoxysilane, 100 parts by weight of anhydrous ethanol, 20 parts by weight of deionized water, and 2.2 parts by weight of 25% ammonia were mixed and stirred at room temperature for 2.2 h. Then, 6 parts by weight of polystyrene microsphere emulsion with a solid content of 10 wt% and a particle size of 220 nm were added, and the reaction was continued with stirring for another 4.2 h. After the reaction was completed, the mixture was centrifuged and washed with anhydrous ethanol. The template agent was removed by calcination at 600℃ for 2 hours to obtain fluorinated hollow silica aerogel nanospheres. 10 parts by weight of the fluorinated hollow silica aerogel nanospheres were added to 100 parts by weight of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 25 parts by weight of N-(2-aminoethyl)maleimide were added, and the mixture was heated to 52℃ and stirred for 4.2 hours. The mixture was then centrifuged, dissolved in anhydrous ethanol, and vacuum dried at 40℃ for 12 hours to obtain maleimide-modified fluorinated hollow silica aerogel nanospheres. Preparation of S4 composite thermal insulation filling material: Phenolic hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer and furan-modified polyhydroxy fatty acid ester prepolymer were added to a 1:1 volume ratio N,N-dimethylformamide / tetrahydrofuran mixed solvent and stirred at room temperature until completely dissolved to obtain a matrix mixture with a solid content of 16wt%. Maleimide-modified fluorinated hollow silica aerogel nanospheres were added to the matrix mixture and ultrasonically dispersed at room temperature for 30 min at 200W to obtain a dispersion. A catalyst and antioxidant were added to the dispersion and stirred at room temperature for 30 min to obtain a casting solution. The casting solution was poured into a flat mold to form continuous fibers, placed in a vacuum oven, heated to 92℃, and kept at that temperature for 4.2 h to obtain a crosslinked preform. The crosslinked preform was washed with anhydrous ethanol and then placed in a freeze dryer and freeze-dried at -55℃ for 24 h to obtain a bio-based composite thermal insulation filling material.

[0027] Example 3: A bio-based composite thermal insulation filling material, composed of the following components in parts by weight: 50 parts of phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer; 20 parts of furan-modified polyhydroxy fatty acid ester prepolymer; 5 parts of maleimide-modified fluorinated hollow silica aerogel nanospheres; 0.3 parts of catalyst; 1.4 parts of antioxidant. The phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer has phenol-hydroxylated chitosan as the main chain, with end-carboxyl polylactic acid prepolymer covalently grafted via amide bonds and stearic acid phase change units covalently grafted via ester bonds. The number average molecular weight of the end-carboxyl polylactic acid prepolymer is 7000, and the stearic acid is of bio-based origin. The number average molecular weight of the furan-modified polyhydroxy fatty acid ester prepolymer is 14000, with furan groups grafted at the ends, and the furan group grafting rate is ≥85%. The maleimide-modified fluorinated hollow silica aerogel nanospheres have a particle size of 300 nm, a hollow pore size of 140 nm, a surface maleimide group grafting rate of ≥90%, and a water contact angle of ≥135°. The catalyst is triethylamine, and the antioxidant is tea polyphenols.

[0028] A method for preparing a bio-based composite thermal insulation filling material includes the following steps: Preparation of S1 phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer: 10 parts by weight of chitosan were added to 100 parts by weight of solvent and frozen at -20℃ and thawed at 25℃ three times until completely dissolved. The solvent was an aqueous solution containing 8 wt% sodium hydroxide and 12 wt% urea. Then, 3.4 parts by weight of 3,4-dihydroxybenzaldehyde were added, and the mixture was heated to 44℃ and stirred for 5 h under nitrogen protection. Then, 0.7 parts by weight of sodium borohydride were added, and the mixture was stirred for another 2.4 h. After the reaction was completed, the pH was adjusted to 7, and the mixture was precipitated with anhydrous ethanol, filtered, washed, and vacuum dried for 12 h to obtain phenol-hydroxylated chitosan. 100 parts by weight of L-lactide, 3 parts by weight of 1,4-succinic acid, and 0.2 parts by weight of stannous octoate were added to a sealed reactor and placed under nitrogen protection. After the reaction, the temperature was raised to 134℃ and stirred for 10 hours. After the reaction, the temperature was cooled to 25℃, dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 hours to obtain a carboxyl-terminated polylactic acid prepolymer with a number average molecular weight of 7000. 10 parts by weight of phenol-hydroxylated chitin, 40 parts by weight of the carboxyl-terminated polylactic acid prepolymer, 10 parts by weight of stearic acid, 4 parts by weight of N,N'-dicyclohexylcarbodiimide, and 0.7 parts by weight of 4-dimethylaminopyridine were added to 200 parts by weight of N,N-dimethylformamide. The temperature was raised to 64℃ under nitrogen protection and stirred for 14 hours. After the reaction, the reaction solution was poured into anhydrous ethanol to precipitate, filtered, washed with anhydrous ethanol, and dried under vacuum at 50℃ for 12 hours to obtain a phenol-hydroxylated chitin-g-polylactic acid-g-stearic acid graft copolymer. Preparation of S2 furan-modified polyhydroxy fatty acid ester prepolymer: 100 parts by weight of polyhydroxy fatty acid ester with a number average molecular weight of 14000, 7 parts by weight of furfuryl alcohol, and 0.7 parts by weight of p-toluenesulfonic acid were added to 300 parts by weight of toluene. The mixture was heated to 114°C under nitrogen protection and refluxed for 7 hours to remove water. After the reaction was completed, toluene was removed by vacuum distillation, the product was dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45°C for 10 hours to obtain furan-modified polyhydroxy fatty acid ester prepolymer. Preparation of S3 maleimide-modified fluorinated hollow silica aerogel nanospheres: 10 parts by weight of tetraethyl orthosilicate, 3 parts by weight of tridecafluorooctyltriethoxysilane, 100 parts by weight of anhydrous ethanol, 20 parts by weight of deionized water, and 2.4 parts by weight of 25% ammonia solution were mixed and stirred at room temperature for 2.4 h. Then, 7 parts by weight of polystyrene microsphere emulsion with a solid content of 10 wt% and a particle size of 240 nm were added, and the mixture was stirred for another 4.4 h. After the reaction was completed, the mixture was centrifuged and washed with anhydrous ethanol. The template agent was removed by calcination at 600℃ for 2 hours to obtain fluorinated hollow silica aerogel nanospheres. 10 parts by weight of the fluorinated hollow silica aerogel nanospheres were added to 100 parts by weight of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 3 parts by weight of N-(2-aminoethyl)maleimide were added, and the mixture was heated to 54℃ and stirred for 4.4 hours. The mixture was then centrifuged, dissolved in anhydrous ethanol, and vacuum dried at 40℃ for 12 hours to obtain maleimide-modified fluorinated hollow silica aerogel nanospheres. Preparation of S4 composite thermal insulation filling material: Phenolic hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer and furan-modified polyhydroxy fatty acid ester prepolymer were added to a 1:1 volume ratio N,N-dimethylformamide / tetrahydrofuran mixed solvent and stirred at room temperature until completely dissolved to obtain a matrix mixture with a solid content of 17wt%. Maleimide-modified fluorinated hollow silica aerogel nanospheres were added to the matrix mixture and ultrasonically dispersed at room temperature for 30 min at 200W to obtain a dispersion. A catalyst and antioxidant were added to the dispersion and stirred at room temperature for 30 min to obtain a casting solution. The casting solution was poured into a flat mold to form continuous fibers, placed in a vacuum oven, heated to 94℃, and kept at that temperature for 4.4 h to obtain a crosslinked preform. The crosslinked preform was washed with anhydrous ethanol and then placed in a freeze dryer and freeze-dried at -55℃ for 24 h to obtain a bio-based composite thermal insulation filling material.

[0029] Example 4: A bio-based composite thermal insulation filling material, composed of the following components in parts by weight: 55 parts of phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer; 25 parts of furan-modified polyhydroxy fatty acid ester prepolymer; 7 parts of maleimide-modified fluorinated hollow silica aerogel nanospheres; 0.4 parts of catalyst; 1.6 parts of antioxidant. The phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer has phenol-hydroxylated chitosan as the main chain, with end-carboxyl polylactic acid prepolymer covalently grafted via amide bonds and stearic acid phase change units covalently grafted via ester bonds. The number average molecular weight of the end-carboxyl polylactic acid prepolymer is 8000, and the stearic acid is of bio-based origin. The number average molecular weight of the furan-modified polyhydroxy fatty acid ester prepolymer is 16000, with furan groups grafted at the ends, and the furan group grafting rate is ≥85%. The maleimide-modified fluorinated hollow silica aerogel nanospheres have a particle size of 350 nm, a hollow pore size of 160 nm, a surface maleimide group grafting rate of ≥90%, and a water contact angle of ≥135°. The catalyst is triethylamine, and the antioxidant is tea polyphenols.

[0030] A method for preparing a bio-based composite thermal insulation filling material includes the following steps: Preparation of S1 phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer: 10 parts by weight of chitosan were added to 100 parts by weight of solvent and frozen at -20℃ and thawed at 25℃ three times until completely dissolved. The solvent was an aqueous solution containing 8 wt% sodium hydroxide and 12 wt% urea. Then, 3.6 parts by weight of 3,4-dihydroxybenzaldehyde were added, and the mixture was heated to 46℃ and stirred under nitrogen protection for 5.3 h. Then, 0.8 parts by weight of sodium borohydride were added, and the mixture was stirred for another 2.6 h. After the reaction was completed, the pH was adjusted to 7, and the mixture was precipitated with anhydrous ethanol, filtered, washed, and vacuum dried for 12 h to obtain phenol-hydroxylated chitosan. 100 parts by weight of L-lactide, 35 parts by weight of 1,4-succinic acid, and 0.25 parts by weight of stannous octoate were added to a sealed reactor and stirred under nitrogen protection. After displacement, the temperature was raised to 136℃ and stirred for 11 h. After the reaction, the temperature was cooled to 25℃, dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 h to obtain a carboxyl-terminated polylactic acid prepolymer with a number average molecular weight of 8000. 10 parts by weight of phenol-hydroxylated chitin, 45 parts by weight of the carboxyl-terminated polylactic acid prepolymer, 11 parts by weight of stearic acid, 4.5 parts by weight of N,N'-dicyclohexylcarbodiimide, and 0.8 parts by weight of 4-dimethylaminopyridine were added to 200 parts by weight of N,N-dimethylformamide. The temperature was raised to 66℃ under nitrogen protection and stirred for 15 h. After the reaction, the reaction solution was poured into anhydrous ethanol to precipitate, filtered, washed with anhydrous ethanol, and dried under vacuum at 50℃ for 12 h to obtain a phenol-hydroxylated chitin-g-polylactic acid-g-stearic acid graft copolymer. Preparation of S2 furan-modified polyhydroxy fatty acid ester prepolymer: 100 parts by weight of polyhydroxy fatty acid ester with a number average molecular weight of 16000, 8 parts by weight of furfuryl alcohol, and 0.8 parts by weight of p-toluenesulfonic acid were added to 300 parts by weight of toluene. The mixture was heated to 116℃ under nitrogen protection and refluxed for 7.3 h to remove water. After the reaction was completed, toluene was removed by vacuum distillation, the product was dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 h to obtain furan-modified polyhydroxy fatty acid ester prepolymer. Preparation of S3 maleimide-modified fluorinated hollow silica aerogel nanospheres: 10 parts by weight of tetraethyl orthosilicate, 3.5 parts by weight of tridecafluorooctyltriethoxysilane, 100 parts by weight of anhydrous ethanol, 20 parts by weight of deionized water, and 2.6 parts by weight of 25% ammonia were mixed and stirred at room temperature for 2.6 h. Then, 8 parts by weight of polystyrene microsphere emulsion with a solid content of 10 wt% and a particle size of 260 nm were added, and the reaction was continued with stirring for another 4.6 h. After the reaction was completed, the mixture was centrifuged and washed with anhydrous ethanol. The template agent was removed by calcination at 600℃ for 2 hours to obtain fluorinated hollow silica aerogel nanospheres. 10 parts by weight of the fluorinated hollow silica aerogel nanospheres were added to 100 parts by weight of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 3.5 parts by weight of N-(2-aminoethyl)maleimide were added, and the mixture was heated to 56℃ and stirred for 4.6 hours. The mixture was then centrifuged, dissolved in anhydrous ethanol, and vacuum dried at 40℃ for 12 hours to obtain maleimide-modified fluorinated hollow silica aerogel nanospheres. Preparation of S4 composite thermal insulation filling material: Phenolic hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer and furan-modified polyhydroxy fatty acid ester prepolymer were added to a 1:1 volume ratio N,N-dimethylformamide / tetrahydrofuran mixed solvent and stirred at room temperature until completely dissolved to obtain a matrix mixture with a solid content of 18wt%. Maleimide-modified fluorinated hollow silica aerogel nanospheres were added to the matrix mixture and ultrasonically dispersed at room temperature for 30 min at 200W to obtain a dispersion. A catalyst and antioxidant were added to the dispersion and stirred at room temperature for 30 min to obtain a casting solution. The casting solution was poured into a flat mold to form continuous fibers, placed in a vacuum oven, heated to 96℃, and kept at that temperature for 4.6 h to obtain a crosslinked preform. The crosslinked preform was washed with anhydrous ethanol and then placed in a freeze dryer and freeze-dried at -55℃ for 24 h to obtain a bio-based composite thermal insulation filling material.

[0031] Example 5: A bio-based composite thermal insulation filling material, composed of the following components in parts by weight: 60 parts of phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer; 30 parts of furan-modified polyhydroxy fatty acid ester prepolymer; 9 parts of maleimide-modified fluorinated hollow silica aerogel nanospheres; 0.5 parts of catalyst; 1.8 parts of antioxidant. The phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer has phenol-hydroxylated chitosan as the main chain, with end-carboxyl polylactic acid prepolymer covalently grafted via amide bonds and stearic acid phase change units covalently grafted via ester bonds. The number average molecular weight of the end-carboxyl polylactic acid prepolymer is 9000, and the stearic acid is of bio-based origin. The number average molecular weight of the furan-modified polyhydroxy fatty acid ester prepolymer is 18000, with furan groups grafted at the ends, and the furan group grafting rate is ≥85%. The maleimide-modified fluorinated hollow silica aerogel nanospheres have a particle size of 400nm, a hollow pore size of 180nm, a surface maleimide group grafting rate of ≥90%, and a water contact angle of ≥135°. The catalyst is triethylamine, and the antioxidant is tea polyphenols.

[0032] A method for preparing a bio-based composite thermal insulation filling material includes the following steps: Preparation of S1 phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer: 10 parts by weight of chitosan were added to 100 parts by weight of solvent and frozen at -20℃ and thawed at 25℃ three times until completely dissolved. The solvent was an aqueous solution containing 8 wt% sodium hydroxide and 12 wt% urea. Then, 3.8 parts by weight of 3,4-dihydroxybenzaldehyde were added, and the mixture was heated to 408℃ and stirred for 5.6 h under nitrogen protection. Then, 0.9 parts by weight of sodium borohydride were added, and the mixture was stirred for another 2.8 h. After the reaction was completed, the pH was adjusted to 7, and the mixture was precipitated with anhydrous ethanol, filtered, washed, and vacuum dried for 12 h to obtain phenol-hydroxylated chitosan. 100 parts by weight of L-lactide, 4 parts by weight of 1,4-succinic acid, and 0.3 parts by weight of stannous octoate were added to a sealed reactor and stirred under nitrogen protection. After displacement, the temperature was raised to 138℃ and stirred for 12 hours. After the reaction, the temperature was cooled to 25℃, dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 hours to obtain a carboxyl-terminated polylactic acid prepolymer with a number average molecular weight of 9000. 10 parts by weight of phenol-hydroxylated chitin, 50 parts by weight of the carboxyl-terminated polylactic acid prepolymer, 12 parts by weight of stearic acid, 5 parts by weight of N,N'-dicyclohexylcarbodiimide, and 0.9 parts by weight of 4-dimethylaminopyridine were added to 200 parts by weight of N,N-dimethylformamide. The temperature was raised to 68℃ under nitrogen protection and stirred for 16 hours. After the reaction, the reaction solution was poured into anhydrous ethanol to precipitate, filtered, washed with anhydrous ethanol, and dried under vacuum at 50℃ for 12 hours to obtain a phenol-hydroxylated chitin-g-polylactic acid-g-stearic acid graft copolymer. Preparation of S2 furan-modified polyhydroxy fatty acid ester prepolymer: 100 parts by weight of polyhydroxy fatty acid ester with a number average molecular weight of 18000, 9 parts by weight of furfuryl alcohol, and 0.9 parts by weight of p-toluenesulfonic acid were added to 300 parts by weight of toluene. The mixture was heated to 118°C under nitrogen protection and refluxed for 7.6 h to remove water. After the reaction was completed, toluene was removed by vacuum distillation, the product was dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45°C for 10 h to obtain furan-modified polyhydroxy fatty acid ester prepolymer. Preparation of S3 maleimide-modified fluorinated hollow silica aerogel nanospheres: 10 parts by weight of tetraethyl orthosilicate, 4 parts by weight of tridecafluorooctyltriethoxysilane, 100 parts by weight of anhydrous ethanol, 20 parts by weight of deionized water, and 2.8 parts by weight of 25% ammonia solution were mixed and stirred at room temperature for 2.8 h. Then, 9 parts by weight of polystyrene microsphere emulsion with a solid content of 10 wt% and a particle size of 280 nm were added, and the reaction was continued with stirring for another 4.8 h. After the reaction was completed, the mixture was centrifuged and washed with anhydrous ethanol. The template agent was removed by calcination at 600℃ for 2 hours to obtain fluorinated hollow silica aerogel nanospheres. 10 parts by weight of the fluorinated hollow silica aerogel nanospheres were added to 100 parts by weight of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 4 parts by weight of N-(2-aminoethyl)maleimide were added, and the mixture was heated to 58℃ and stirred for 4.8 hours. The mixture was then centrifuged, dissolved in anhydrous ethanol, and vacuum dried at 40℃ for 12 hours to obtain maleimide-modified fluorinated hollow silica aerogel nanospheres. Preparation of S4 composite thermal insulation filling material: Phenolic hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer and furan-modified polyhydroxy fatty acid ester prepolymer were added to a 1:1 volume ratio N,N-dimethylformamide / tetrahydrofuran mixed solvent and stirred at room temperature until completely dissolved to obtain a matrix mixture with a solid content of 19wt%. Maleimide-modified fluorinated hollow silica aerogel nanospheres were added to the matrix mixture and ultrasonically dispersed at room temperature for 30 min at 200W to obtain a dispersion. A catalyst and antioxidant were added to the dispersion and stirred at room temperature for 30 min to obtain a casting solution. The casting solution was poured into a flat mold to form continuous fibers, placed in a vacuum oven, heated to 98℃, and kept at that temperature for 4.8 h to obtain a crosslinked preform. The crosslinked preform was washed with anhydrous ethanol and then placed in a freeze dryer and freeze-dried at -55℃ for 24 h to obtain a bio-based composite thermal insulation filling material.

[0033] Example 6: A bio-based composite thermal insulation filling material, composed of the following components in parts by weight: 65 parts of phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer; 35 parts of furan-modified polyhydroxy fatty acid ester prepolymer; 10 parts of maleimide-modified fluorinated hollow silica aerogel nanospheres; 0.6 parts of catalyst; 2 parts of antioxidant. The phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer has phenol-hydroxylated chitosan as the main chain, with end-carboxyl polylactic acid prepolymer covalently grafted via amide bonds and stearic acid phase change units covalently grafted via ester bonds. The number average molecular weight of the end-carboxyl polylactic acid prepolymer is 10,000, and the stearic acid is of bio-based origin. The number average molecular weight of the furan-modified polyhydroxy fatty acid ester prepolymer is 20,000, with furan groups grafted at the ends, and the furan group grafting rate is ≥85%. The maleimide-modified fluorinated hollow silica aerogel nanospheres have a particle size of 450 nm, a hollow pore size of 200 nm, a surface maleimide group grafting rate of ≥90%, and a water contact angle of ≥135°. The catalyst is triethylamine, and the antioxidant is tea polyphenols.

[0034] A method for preparing a bio-based composite thermal insulation filling material includes the following steps: Preparation of S1 phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer: 10 parts by weight of chitosan were added to 100 parts by weight of solvent and frozen at -20℃ and thawed at 25℃ three times until completely dissolved. The solvent was an aqueous solution containing 8 wt% sodium hydroxide and 12 wt% urea. Then, 4 parts by weight of 3,4-dihydroxybenzaldehyde were added, and the mixture was heated to 50℃ and stirred for 6 hours under nitrogen protection. Then, 1 part by weight of sodium borohydride was added, and the mixture was stirred for another 3 hours. After the reaction was completed, the pH was adjusted to 7, and the mixture was precipitated with anhydrous ethanol, filtered, washed, and vacuum dried for 12 hours to obtain phenol-hydroxylated chitosan. 100 parts by weight of L-lactide, 4.5 parts by weight of 1,4-succinic acid, and 0.35 parts by weight of stannous octoate were added to a sealed reactor and purged with nitrogen. The temperature was raised to 140℃ and stirred for 13 hours. After the reaction, the temperature was cooled to 25℃, dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 hours to obtain a carboxyl-terminated polylactic acid prepolymer with a number average molecular weight of 10,000. 10 parts by weight of phenol-hydroxylated chitin, 55 parts by weight of the carboxyl-terminated polylactic acid prepolymer, 13 parts by weight of stearic acid, 5.5 parts by weight of N,N'-dicyclohexylcarbodiimide, and 1 part by weight of 4-dimethylaminopyridine were added to 200 parts by weight of N,N-dimethylformamide. The temperature was raised to 70℃ under nitrogen protection and stirred for 17 hours. After the reaction, the reaction solution was poured into anhydrous ethanol to precipitate, filtered, washed with anhydrous ethanol, and dried under vacuum at 50℃ for 12 hours to obtain a phenol-hydroxylated chitin-g-polylactic acid-g-stearic acid graft copolymer. Preparation of S2 furan-modified polyhydroxy fatty acid ester prepolymer: 100 parts by weight of polyhydroxy fatty acid ester with a number average molecular weight of 20,000, 10 parts by weight of furfuryl alcohol, and 1 part by weight of p-toluenesulfonic acid were added to 300 parts by weight of toluene. The mixture was heated to 120°C under nitrogen protection and refluxed for 8 hours to remove water. After the reaction was completed, toluene was removed by vacuum distillation, the product was dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45°C for 10 hours to obtain furan-modified polyhydroxy fatty acid ester prepolymer. Preparation of S3 maleimide-modified fluorinated hollow silica aerogel nanospheres: 10 parts by weight of tetraethyl orthosilicate, 4.5 parts by weight of tridecafluorooctyltriethoxysilane, 100 parts by weight of anhydrous ethanol, 20 parts by weight of deionized water, and 3 parts by weight of 25% ammonia were mixed and stirred at room temperature for 3 hours. Then, 5-10 parts by weight of a polystyrene microsphere emulsion with a solid content of 10 wt% and a particle size of 300 nm were added, and the mixture was stirred for another 5 hours. After the reaction, the mixture was centrifuged, washed with anhydrous ethanol, and then... The template agent was removed by calcination at 00℃ for 2 hours to obtain fluorinated hollow silica aerogel nanospheres. 10 parts by weight of the fluorinated hollow silica aerogel nanospheres were added to 100 parts by weight of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 4.5 parts by weight of N-(2-aminoethyl)maleimide were added, and the mixture was heated to 60℃ and stirred for 5 hours. The mixture was then centrifuged, dissolved in anhydrous ethanol, and vacuum dried at 40℃ for 12 hours to obtain maleimide-modified fluorinated hollow silica aerogel nanospheres. Preparation of S4 composite thermal insulation filling material: Phenolic hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer and furan-modified polyhydroxy fatty acid ester prepolymer were added to a 1:1 volume ratio N,N-dimethylformamide / tetrahydrofuran mixed solvent and stirred at room temperature until completely dissolved to obtain a matrix mixture with a solid content of 20wt%. Maleimide-modified fluorinated hollow silica aerogel nanospheres were added to the matrix mixture and ultrasonically dispersed at room temperature for 30 min at 200W to obtain a dispersion. A catalyst and antioxidant were added to the dispersion and stirred at room temperature for 30 min to obtain a casting solution. The casting solution was poured into a flat mold to form continuous fibers, placed in a vacuum oven, heated to 100℃, and kept at that temperature for 5 h to obtain a crosslinked preform. The crosslinked preform was washed with anhydrous ethanol and then placed in a freeze dryer and freeze-dried at -55℃ for 24 h to obtain a bio-based composite thermal insulation filling material.

[0035] Example 7: The phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer in the raw materials was replaced with a polymer without grafted stearic acid, and the remaining raw materials and step parameters were the same as in Example 4.

[0036] Example 8: The furan-modified polyhydroxy fatty acid ester prepolymer in the raw materials was replaced with unmodified polyhydroxy fatty acid ester; the remaining raw materials and step parameters were the same as in Example 4.

[0037] Example 9: The maleimide-modified fluorinated hollow silica aerogel nanospheres in the raw materials were replaced with unfluorinated silica aerogel nanospheres, and the remaining raw materials and step parameters were the same as in Example 4.

[0038] Example 10: The DA dynamic crosslinking system was removed, that is, unmodified polyhydroxy fatty acid ester was used directly. The aerogel microspheres were directly physically doped without maleimide modification and without DA crosslinking reaction. The film was formed directly by solvent evaporation. The remaining steps were the same as in Example 4.

[0039] Example 11: Prepared using conventional physical blending method, i.e., physical blending of chitin, polylactic acid and stearic acid, without DA crosslinking reaction, directly physical blending of all raw materials and solvent evaporation to form film; aerogel microspheres are directly physically doped.

[0040] The performance of the bio-based composite thermal insulation filling materials prepared in Examples 1-11 was tested, and the test results are shown in Tables 1-2 below: Table 1: Examples 1-6

[0041] Table 2: Examples 7-11

[0042] From the experimental data in Tables 1 and 2 above, we can see that: (1) In Examples 1 to 6, the amount of aerogel added was gradually increased from 1 part to 10 parts. Its nano-closed-pore structure can effectively lock in static air and block air convection heat transfer and solid-state heat conduction, thereby achieving a continuous reduction in thermal conductivity. The fluorinated alkyl chains grafted on the surface of the aerogel construct a continuous hydrophobic barrier inside and on the surface of the material, preventing water molecules from entering the pores and filling the air in a humid environment, thus fundamentally solving the problem of loss of heat retention after natural bio-based materials absorb water. Among them, Example 4 achieved the optimal balance between low thermal conductivity and mechanical properties. In Examples 5 and 6, the aerogel addition was slightly excessive, resulting in a slight decrease in thermal conductivity, and a slight decrease in wet heat retention rate and resilience.

[0043] (2) The phase transition enthalpy of Examples 1-6 gradually increased from 85.2 J / g to 91.5 J / g, and the phase transition temperature range remained stable at 25-35℃, matching the comfortable temperature range of the human body. This is due to the molecular structure design of stearic acid phase transition units covalently grafted onto the phenol-hydroxylated chitin backbone through ester bonds. Unlike the physical doping phase transition microcapsules of the prior art, the covalently grafted stearic acid has no free state, avoiding leakage, migration and water washing loss of the phase change material. It can achieve heat absorption and release through reversible solid-liquid phase transition when the ambient temperature fluctuates, actively maintaining the material temperature stability and improving wearing comfort. In Examples 1-6, as the amount of stearic acid grafted increases, the phase transition enthalpy increases synchronously. Among them, the formulation ratio of Example 4 achieves excellent active temperature regulation effect without destroying the regularity of the polymer crosslinking network due to excessive grafting, which is the optimal balance point between temperature regulation performance and structural stability.

[0044] (3) In Examples 1 to 6, as the ratio of phenol hydroxylated chitin graft copolymer to furan modified polyhydroxy fatty acid ester prepolymer was optimized, the interpenetration entanglement of the double network continued to improve. The rigid chitin backbone and the flexible polylactic acid and polyhydroxy fatty acid ester segments worked together to give the material excellent resistance to compression deformation and achieve ultra-high resilience, solving the problem of high brittleness and poor resilience of bio-based polyesters such as polylactic acid. At the same time, the dynamic covalent bond of Diels-Alder (DA) has thermal reversible properties. The microstructural damage caused by washing and compression can be self-repaired by low temperature heat treatment. In addition, the aerogel microspheres and phase change units are all anchored in the cross-linked network by covalent bonds and will not migrate or fall off due to washing and compression. Therefore, the material has highly stable performance in long-term use.

[0045] (4) Examples 1-6 all showed an antibacterial rate of ≥99% against Escherichia coli and Staphylococcus aureus, a limiting oxygen index of ≥32%, and a biodegradability rate of ≥90% after 180 days of composting, achieving a multi-functional integrated system of heat preservation, temperature regulation, antibacterial, flame retardant, and biodegradability. This is because the catechol groups introduced on the phenol-hydroxylated chitin molecular chain have natural broad-spectrum antibacterial properties, eliminating the need for additional small molecule antibacterial agents and thus avoiding the problems of easy loss and precipitation of antibacterial agents; the covalently anchored silica aerogel is an inorganic flame retardant component, which can form a dense inorganic carbon layer on the surface when the material burns, blocking oxygen and heat transfer, thus achieving halogen-free flame retardancy; all matrix raw materials, chitin, polylactic acid, polyhydroxy fatty acid ester, and stearic acid, are bio-based renewable resources, with no petroleum-based raw materials added, and the cross-linking network is composed of biodegradable ester bonds and amide bonds, so it can be completely degraded by microorganisms under composting conditions.

[0046] (5) Example 7 is an example without the grafted stearic acid phase change unit. According to its test results, except for the phase change enthalpy value of 0 and the complete loss of active temperature regulation function, the other core properties such as heat preservation, resilience, washability, and antibacterial properties are not significantly different from those of Example 4. This is because stearic acid, as a phase change temperature regulation unit, achieves leakage-free phase change temperature regulation and heat preservation through covalent grafting modification. Without this modification, the temperature adaptive heat preservation effect cannot be achieved.

[0047] (6) Example 8 was an unmodified polyhydroxyalkanoate without furan reactive groups. The test results showed that the material's compression rebound rate decreased to 72.3%, the rebound rate after 500 compression cycles was only 58.6%, the heat retention rate after 50 water washes was only 42.5%, and the thermal conductivity increased to 0.032 W / (mK). This is because the unmodified polyhydroxyalkanoate has no furan reactive sites and cannot participate in the DA crosslinking reaction. It cannot form an interpenetrating crosslinked double network with the graft copolymer. The material is only a physical blend of linear polymers and cannot form a stable three-dimensional fluffy porous structure. The pores are prone to collapse and the aerogel is prone to agglomeration and loss. Therefore, the rebound performance and heat retention stability are greatly deteriorated.

[0048] (7) Example 9 is a non-fluorinated silica aerogel microsphere. The corresponding test results show that the water contact angle of the material decreased to 86.2°, and the wet-state heat retention rate was only 61.3%. This is because the surface of the non-fluorinated silica aerogel is hydrophilic silanol, which cannot give the material superhydrophobicity. In a wet environment, water molecules can easily enter the material pores and fill the pores that originally locked static air, resulting in a significant increase in the thermal conductivity of the material and a serious loss of heat retention.

[0049] (8) Example 10 is an example of pure physical blending without the DA dynamic crosslinking system. The test results show that the compression rebound rate is only 65.8%, the heat retention rate after 50 washes is only 32.7%, and the wet heat retention rate is only 38.5%. The antibacterial rate and flame retardancy are far lower than those of Example 4. This is because without the DA crosslinking system, the aerogel microspheres cannot be anchored by covalent bonds and are only physically doped, which is easy to agglomerate, pulverize, and be lost during washing; stearic acid is physically mixed and is easy to leak and migrate; the compatibility between the various bio-based components is extremely poor, and there are a large number of interface defects. Therefore, the heat retention, rebound, washability, and multifunctionality are all greatly reduced.

[0050] (9) Example 11 is a conventional technical solution without any chemical grafting or cross-linking modification. Chitin, polylactic acid, stearic acid, aerogel, and other raw materials are directly physically blended into a film. According to the test results, all properties of the material are the worst among the 11 groups. The thermal conductivity is as high as 0.039 W / (mK), the wet heat retention rate is only 35.6%, the compression rebound rate is only 72.3%, and the antibacterial rate, flame retardancy, and biodegradation rate are all lower than those of Examples 1-6. This is because without any chemical modification, the polarity difference between chitin, polylactic acid, and polyhydroxyalkanoates is large, and the compatibility is extremely poor, making it impossible to form a uniform and stable material structure. Stearic acid and aerogel are physical dopants, which are easy to migrate, leak, and run off, and cannot take into account the properties of heat retention, rebound, washability, and multifunctionality.

[0051] In summary, the bio-based composite thermal insulation filling materials prepared in Examples 1-6 of this invention achieve the effects of low thermal conductivity, high humidity-state thermal stability, leak-free phase change temperature regulation, high resilience and washability, antibacterial and flame-retardant properties, and full biodegradability. The control test results of Examples 7-11 fully verify that the phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer solves the three core problems of bio-based component compatibility, phase change material leakage prevention, and natural antibacterial properties; the interpenetrating cross-linked network constructed by the dynamic covalent bonds of furan and maleimide DA achieves high resilience, high washability, and self-healing performance; the covalent anchoring modification of fluorinated hollow silica aerogel achieves low thermal conductivity and high humidity-state thermal stability; and the design of fully bio-based raw materials and degradable cross-linked structures achieves a balance between high performance and environmentally friendly degradability, demonstrating excellent application prospects.

[0052] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A bio-based composite thermal insulation filling material, characterized in that, Composed of the following components by weight: 40-65 parts of phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer; 10-35 parts of furan-modified polyhydroxy fatty acid ester prepolymer; 1-10 parts of maleimide-modified fluorinated hollow silica aerogel nanospheres; 0.1-0.6 parts of catalyst; 1-2 parts of antioxidant.

2. The bio-based composite thermal insulation filling material according to claim 1, characterized in that, The phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer has phenol-hydroxylated chitosan as the main chain, and is covalently grafted with carboxyl-terminated polylactic acid prepolymer via amide bonds and with stearic acid phase change units via ester bonds.

3. The bio-based composite thermal insulation filling material according to claim 2, characterized in that, The number-average molecular weight of the carboxyl-terminated polylactic acid prepolymer is 5,000 to 10,000, and the stearic acid is of bio-based origin.

4. The bio-based composite thermal insulation filling material according to claim 1, characterized in that, The number average molecular weight of the furan-modified polyhydroxy fatty acid ester prepolymer is 10,000 to 20,000.

5. The bio-based composite thermal insulation filling material according to claim 1, characterized in that, The furan-modified polyhydroxy fatty acid ester prepolymer has furan groups grafted onto its end groups, with a furan group grafting rate of ≥85%.

6. The bio-based composite thermal insulation filling material according to claim 1, characterized in that, The maleimide-modified fluorinated hollow silica aerogel nanospheres have a particle size of 200~450nm, a hollow pore size of 100~200nm, a surface maleimide group grafting rate of ≥90%, and a water contact angle of ≥135°.

7. The bio-based composite thermal insulation filling material according to claim 1, characterized in that, The catalyst is triethylamine.

8. The bio-based composite thermal insulation filling material according to claim 1, characterized in that, The antioxidant is tea polyphenols.

9. A method for preparing a bio-based composite thermal insulation filling material, characterized in that, Includes the following steps: Preparation of S1 phenol-hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer: 10 parts by weight of chitosan were added to 100 parts by weight of solvent and frozen at -20℃ and thawed at 25℃ three times until completely dissolved. Then, 3-4 parts by weight of 3,4-dihydroxybenzaldehyde were added, and the temperature was raised to 40-50℃. The mixture was stirred under nitrogen protection for 4-6 hours. Then, 0.5-1 parts by weight of sodium borohydride were added, and the mixture was stirred for another 2-3 hours. After the reaction was completed, the pH was adjusted, and the mixture was precipitated with anhydrous ethanol, filtered, washed, and vacuum dried for 12 hours to obtain phenol-hydroxylated chitosan. 100 parts by weight of L-lactide, 2-4.5 parts by weight of 1,4-succinic acid, and 0.1-0.35 parts by weight of stannous octoate were added to a sealed reactor, purged with nitrogen, and heated to 130-140℃. The mixture was stirred and melted for 8 hours. ~13h; after the reaction, cool to 25℃, dissolve in dichloromethane, precipitate with anhydrous ethanol, filter, and vacuum dry at 45℃ for 10h to obtain a carboxyl-terminated polylactic acid prepolymer with a number average molecular weight of 5000~10000; add 10 parts by weight of phenol-hydroxylated chitin, 30~55 parts by weight of carboxyl-terminated polylactic acid prepolymer, 8~13 parts by weight of stearic acid, 3~5.5 parts by weight of N,N'-dicyclohexylcarbodiimide, and 0.5~1 parts by weight of 4-dimethylaminopyridine to 200 parts by weight of N,N-dimethylformamide, heat to 60~70℃ under nitrogen protection, and stir for 12~17h; after the reaction, pour the reaction solution into anhydrous ethanol to precipitate, filter, wash with anhydrous ethanol, and vacuum dry at 50℃ for 12h to obtain a phenol-hydroxylated chitin-g-polylactic acid-g-stearic acid graft copolymer; Preparation of S2 furan-modified polyhydroxy fatty acid ester prepolymer: 100 parts by weight of polyhydroxy fatty acid ester with a number average molecular weight of 10,000-20,000, 5-10 parts by weight of furfuryl alcohol, and 0.5-1 parts by weight of p-toluenesulfonic acid were added to 300 parts by weight of toluene. The mixture was heated to 110-120℃ under nitrogen protection and refluxed for 6-8 hours to remove water. After the reaction was completed, toluene was removed by vacuum distillation, the product was dissolved in dichloromethane, precipitated with anhydrous ethanol, filtered, and dried under vacuum at 45℃ for 10 hours to obtain furan-modified polyhydroxy fatty acid ester prepolymer. Preparation of S3 maleimide-modified fluorinated hollow silica aerogel nanospheres: 10 parts by weight of tetraethyl orthosilicate, 2-4.5 parts by weight of tridecafluorooctyltriethoxysilane, 100 parts by weight of anhydrous ethanol, 20 parts by weight of deionized water, and 2-3 parts by weight of 25% ammonia solution were mixed and stirred at room temperature for 2-3 hours. Then, 5-10 parts by weight of polystyrene microsphere emulsion with a solid content of 10 wt% and a particle size of 200-300 nm were added, and the mixture was stirred for another 4-5 hours. After the reaction was complete, the mixture was centrifuged and washed with anhydrous ethanol. The template agent was removed by calcination at 600℃ for 2 hours to obtain fluorinated hollow silica aerogel nanospheres. 10 parts by weight of the fluorinated hollow silica aerogel nanospheres were added to 100 parts by weight of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 2-4.5 parts by weight of N-(2-aminoethyl)maleimide were added, and the mixture was heated to 50-60℃ and stirred for 4-5 hours. The mixture was then centrifuged, dissolved in anhydrous ethanol, and vacuum dried at 40℃ for 12 hours to obtain maleimide-modified fluorinated hollow silica aerogel nanospheres. Preparation of S4 composite thermal insulation filling material: Phenolic hydroxylated chitosan-g-polylactic acid-g-stearic acid graft copolymer and furan-modified polyhydroxy fatty acid ester prepolymer were added to a 1:1 volume ratio N,N-dimethylformamide / tetrahydrofuran mixed solvent and stirred at room temperature until completely dissolved to obtain a matrix mixture with a solid content of 15~20wt%; maleimide-modified fluorinated hollow silica aerogel nanospheres were added to the matrix mixture and ultrasonically dispersed at room temperature for 30 min at 200W to obtain a dispersion; a catalyst and antioxidant were added to the dispersion and stirred at room temperature for 30 min to obtain a casting solution; the casting solution was poured into a flat mold to form continuous fibers, placed in a vacuum oven, heated to 90~100℃, and kept at the temperature for 4~5 h to obtain a cross-linked preform; The cross-linked preform was soaked and washed with anhydrous ethanol and then placed in a freeze dryer and freeze-dried at -55℃ for 24 hours to obtain a bio-based composite thermal insulation filling material.

10. The method for preparing a bio-based composite thermal insulation filling material according to claim 9, characterized in that, In step S1, the solvent is an aqueous solution containing 8 wt% sodium hydroxide and 12 wt% urea.

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