A polyphenol compound-modified polyurethane elastomer and a method for preparing the same

Abstract

The application designs a kind of polyphenol compound modified polyurethane elastomer and preparation method thereof, belongs to high-performance polymer technical field.The polyphenol compound modified polyurethane is a new type of high-performance self-repairing polyurethane, and the polyphenol compound in the polyphenol compound modified polyurethane can be crosslinked with high molecular chain, to improve the mechanical properties of polyurethane;It can produce dynamic chemical bond with the specific point of high molecular chain, to improve the self-repairing performance of polyurethane.The method is to efficiently introduce polyphenol substance, to crosslink it with polyurethane segment, specific organic solvent N, N-dimethylformamide, dimethyl sulfoxide or tetrahydrofuran, organic phase is introduced into solid polyurethane by soaking method, at the same time, too little organic solvent cannot completely soak polyurethane base, causing performance loss, too much tetrahydrofuran can cause waste of organic phase, at the same time, pollute the environment, increase production cost.

Description

Technical Field

[0001] This invention designs a polyphenol-modified polyurethane elastomer and its preparation method, belonging to the field of high-performance polymer technology. Background Technology

[0002] Polyurethane is hailed as the "fifth largest plastic" due to its excellent mechanical properties, good deformation ability, strong biocompatibility and solvent resistance, and diverse applications. Polyurethane materials are widely used in many fields, including the coal industry, transportation and construction, mechanical engineering, electronics and electrical engineering, and biomedicine. However, current research in the polyurethane field still faces bottlenecks such as poor repairability, uneven cell size, insufficient aging resistance, and limited material properties that are difficult to adjust through simple methods.

[0003] To extend the service life and improve the mechanical properties of polyurethane, researchers typically modify it using spray coatings or surface film coatings. Spray coatings significantly improve the wear resistance of polyurethane but reduce its hardness adjustment capabilities. Surface coatings protect the polyurethane substrate while increasing its application range, but the limited properties of the coating film reduce the versatility of the polyurethane.

[0004] Existing technologies typically utilize dynamic disulfide bonds in 2-hydroxyethyl disulfide (HEDS), dynamic Diels-Alder bonds, and dynamic borate ester bonds in polyurethane (IPDA-BA) produced using boric acid as a crosslinking agent. However, these dynamic chemical bonds themselves have low bond energies, which can reduce the overall mechanical properties of the material when introduced into the polyurethane system. Furthermore, since most dynamic chemical bonds are highly sensitive to ambient temperature, heating the polyurethane material may disrupt the stability of the overall polymer chain, reducing the polyurethane's mechanical properties and service life. Summary of the Invention

[0005] To address the shortcomings of existing technologies, one objective of this invention is to provide a polyphenol-modified polyurethane elastomer. This polyphenol-modified polyurethane elastomer contains high-bond-energy dynamic chemical bonds, which enhance its mechanical properties under high-temperature conditions. Due to the strong hydrogen bonding between polyphenols and the polar groups within the polymer, its self-healing ability is enhanced while maintaining the inherent mechanical properties of the polyurethane material, thus increasing its service life. Simultaneously, natural polyphenols possess various special functions such as UV resistance and metal chelation, allowing for the expansion of polyurethane applications by selecting different types of polyphenols.

[0006] The second objective of this invention is to provide a method for preparing polyphenolic compound-modified polyurethane elastomers.

[0007] The objective of this invention is achieved through the following technical solutions.

[0008] A polyphenol-modified polyurethane elastomer, wherein the polyurethane elastomer is composed of hard segments and soft segments, and intermolecular hydrogen bonds are formed between the polyphenol compound and the hard and soft segments of the polyurethane elastomer; the structural formula of the polyphenol-modified polyurethane elastomer is as follows:

[0009]

[0010] Wherein, R' and R” are -H, -OH, C3-C5 alkyl, benzene ring, catechol or pyrogallol, respectively; These are intermolecular hydrogen bonds; the value of x ranges from 4 to 30.

[0011] Preferably, the mass fraction of polyphenolic compounds in the polyphenolic compound-modified polyurethane elastomer is 5% to 25%.

[0012] Preferably, the polyurethane elastomer is obtained by curing component A and component B. The total mass of the raw materials used to prepare component A is 100%, and the components and their mass fractions are as follows: diisocyanate substances 44%–46%, polypolyols 54%–56%. The total mass of the raw materials used to prepare component B is 100%, and the components and their mass fractions are as follows: polypolyols 70%–74%, polyether 330N polyol (330N) 18%–22%, and diol chain extenders 4%–8%.

[0013] Preferably, the polypolyol is one or more of polybutanediol (PTMG), polypropylene glycol (PPG), and polyethylene glycol (PEG).

[0014] Preferably, the diisocyanate is one or more of diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI).

[0015] Preferably, the diol chain extender is one or more of 1,4-butanediol (BDO), 1,3-propanediol (PDO), ethylene glycol (EG), and 1,5-pentanediol (PTDO).

[0016] Preferably, the molecular weight of the polyol is 1760-2080, and the molecular weight of the polyether 330N polyol is 4600-4800.

[0017] Preferably, the polyurethane elastomer is prepared by the following method, the steps of which include:

[0018] (1) Under the protection of protective gas, the raw materials of component A, diphenylmethane diisocyanate and polyol, are mixed, heated to 80-85°C, stirred and reacted for 4-5 hours, and then cooled to obtain viscous polyurethane prepolymer;

[0019] (2) Under air-isolated conditions, the viscous polyurethane prepolymer is preheated to 40-50°C, and the polyol, polyether 330N polyol and diol chain extender in component B are preheated to 50-70°C.

[0020] (3) Stir the preheated raw material in step (2) at a speed of 2000 r / min for 10-15 s, pour it into a polytetrafluoroethylene mold, and cure it at 65-75℃ for 2-4 h to obtain polyurethane elastomer.

[0021] Preferably, the isocyanate content of the polyurethane prepolymer is determined by titration: the polyurethane prepolymer is added to isopropanol, heated and stirred at 45-55°C to dissolve, and a titration sample solution is obtained; then, the isocyanate content in the prepolymer is determined by titration using a toluene solution of bromocresol blue and di-n-butylamine as an indicator.

[0022] Preferably, the ratio of the polyurethane prepolymer to isopropanol is 3-4 g: 450-550 mL; the volume ratio of the titration sample solution to the di-n-butylamine toluene solution is 2:1; and the ratio of the bromocresol blue to the titration sample solution is 1 g: 1000 mL.

[0023] Preferably, the mass relationship between the polyurethane prepolymer, the polyol in component B, the polyether 330N polyol, and the diol chain extender satisfies the following formula:

[0024] (m1×a%) / 42=R×((m2 / N1)×2+(m3 / N2)×3+(m4 / N3)×2)

[0025] In the formula, m1, m2, m3, and m4 represent the masses of the polyurethane prepolymer, the polyol in component B, the polyether 330N polyol, and the diol chain extender, respectively; N1, N2, and N3 represent the molecular weights of the polyol in component B, the polyol in component B, the polyether 330N polyol, and the diol chain extender, respectively; a represents the isocyanate content of the polyurethane prepolymer; and R is the ratio of isocyanate to hydroxyl groups in the system, with R values ​​ranging from 1.04 to 1.06.

[0026] A method for preparing polyphenol-modified polyurethane elastomer according to the present invention, comprising the following steps:

[0027] The polyurethane elastomer was immersed and stirred in an organic solution of polyphenolic substances for 18–24 hours. After complete immersion, the solid phase was removed and dried at 25–70°C to obtain polyphenolic compound-modified polyurethane elastomer. The organic solvent was N,N-dimethylformamide, dimethyl sulfoxide, or tetrahydrofuran.

[0028] Preferably, the polyphenolic substance is ellagic acid, punicin, gallic acid, tannic acid, or tea polyphenols.

[0029] Preferably, the ratio of the polyphenolic substance to the organic solvent is 4-5g: 200-250mL; the soaking process is carried out at 25-40℃ with a stirring speed of 200-500r / min.

[0030] Beneficial effects

[0031] This invention provides a polyphenol-modified polyurethane elastomer, which is a novel high-performance self-healing polyurethane. The polyphenols in the polyphenol-modified polyurethane can crosslink with polymer chains to improve the mechanical properties of the polyurethane; and can form dynamic chemical bonds with specific sites on the polymer chains to improve the self-healing properties of the polyurethane.

[0032] This invention provides a polyphenol-modified polyurethane elastomer, which is composed of two components, A and B. Taking the total mass of raw materials A and B as 100%, the components and their mass fractions in raw material A are as follows: diisocyanate 44%–46%, polypolyol 54%–56%; the components and their mass fractions in raw material B are as follows: polypolyol 70%–74%, polyether 330N polyol (330N) 18%–22%, and diol chain extender 4%–8%. The set mass fractions ensure a balance between -NCO and -OH groups in the polyurethane, endowing it with excellent mechanical properties while maintaining its deformation capacity.

[0033] This invention provides a polyphenol-modified polyurethane elastomer. In the preparation of the polyurethane elastomer, the diisocyanate in component A contains isocyanate groups at both ends, and the polyol contains hydroxyl groups at both ends. After initial synthesis of the prepolymer, both can be stored for a long time at room temperature. Subsequently, different types of long-chain polymer segments (PTMG, PPG, etc.), crosslinking agents (such as 330N, etc.), and chain extenders (such as BDO, PDO, etc.) can be added according to different production needs. The above raw materials can polymerize at room temperature to produce polyurethane elastomer. After treatment with a tetrahydrofuran solution of polyphenols and drying, the finished product is obtained. The method is simple, the experimental formula can be modified according to production needs, and it can be industrialized.

[0034] This invention provides a polyphenolic compound-modified polyurethane elastomer, wherein a reaction temperature of 80-85°C is an important condition for the successful prepolymerization during the preparation of the polyurethane elastomer.

[0035] This invention provides a polyphenol-modified polyurethane elastomer. In the preparation of this polyurethane elastomer, maintaining the preheating temperature of the prepolymer at 40–50°C is crucial for its preservation. At temperatures of 50–70°C, the prepolymer will undergo self-polymerization. The prepolymer is end-capped with isocyanate (-NCO) groups. At room temperature, it tends to polymerize with hydroxyl groups in the chain extenders and crosslinking agents of the main raw materials. This polymerization method promotes the forward reaction and accelerates the reaction rate.

[0036] This invention provides a polyphenolic compound-modified polyurethane elastomer. In the preparation of the polyurethane elastomer, it is necessary to control the isocyanate content of the prepolymer. Excessive isocyanate content will make it difficult to form the polyurethane structure and will not be able to obtain the polyurethane elastomer. Excessive hydroxyl groups in the main raw materials will reduce the mechanical properties of the polyurethane.

[0037] This invention provides a method for preparing polyphenol-modified polyurethane. In order to efficiently introduce polyphenolic substances and crosslink them with polyurethane segments, specific organic solvents such as N,N-dimethylformamide, dimethyl sulfoxide, or tetrahydrofuran are used to introduce the organic phase into the solid polyurethane through an immersion method. However, too little organic solvent will not be able to completely penetrate the polyurethane substrate, resulting in performance loss, while too much tetrahydrofuran will waste the organic phase, pollute the environment, and increase production costs. Attached Figure Description

[0038] Figure 1 Infrared spectra of polyurethane blank sample, polyurethane sample treated with tannic acid at room temperature and 70℃, and polyurethane sample treated with tea polyphenols at room temperature and 70℃.

[0039] Figure 2 The mechanical property test results are shown in the figures for the following samples: a blank polyurethane sample, a polyurethane sample treated with tannic acid at room temperature, 50℃ and 70℃, and a polyurethane sample treated with tea polyphenols at room temperature, 50℃ and 70℃.

[0040] Figure 3 The mechanical properties of the polyurethane samples treated with tetrahydrofuran and N,N-dimethylformamide are shown in the figure. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the present invention.

[0042] Example 1

[0043] In this embodiment, the molecular weight of polybutane glycol is 1760, and the molecular weight of polyether 330N polyol is 4600.

[0044] (1) Add 45g of diphenylmethane diisocyanate and 55g of polybutane glycol to a 100mL three-necked flask, heat to 80℃, stir the raw materials at a rate of 200r / min to mix them evenly, and obtain polyurethane prepolymer after reacting for 4h.

[0045] (2) Take 0.3995g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to dissolve it completely. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1036mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 12.89%.

[0046] The ratio of the mass (g) of bromocresol blue in the indicator to the volume (mL) of the solvent sodium hydroxide is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0047] (3) Preheat the prepolymer titrated in step (2) to 50°C, and preheat the main raw materials polybutanediol, polyether 330N polyol and 1,4-butanediol after dehydration to 70°C.

[0048] (4) Add 35.86g of polybutanediol, 9.96g of polyether 330N polyol and 3.76g of 1,4-butanediol from step (3) to the container in sequence, then add 45.17g of prepolymer and stir the solution at a stirring rate of 2000r / min for 12s; pour it into a polytetrafluoroethylene container and place it in an oven at 70℃ for curing for 4h to obtain polyurethane elastomer.

[0049] (5) The polyurethane elastomer obtained in step (4) is immersed in 250 mL of tetrahydrofuran solution of tea polyphenols. At this time, the solution is dark brown. After immersion for 12 hours, the polyurethane is taken out and dried at room temperature for 12 hours to obtain polyurethane elastomer modified with tea polyphenols. The polyurethane modified with tea polyphenols is dark brown, which confirms that tea polyphenols have been successfully introduced into the polyurethane elastomer.

[0050] The ratio of the mass (g) of tea polyphenols to the volume (mL) of tetrahydrofuran is 5:250.

[0051] Samples 1.2132 g and 0.8901 g of the polyurethane elastomer obtained in step (4) were named Sample 1 and Sample 2, respectively. Sample 1 was immersed in 18 ml of tetrahydrofuran solvent containing 0.45 g of tannic acid, and Sample 2 was immersed in 18 ml of tetrahydrofuran solvent. The immersion was carried out for 2 hours with a stirring rate of 600 r / min. The solid phases were then removed, dried at room temperature, and weighed. The mass of Sample 1 was 1.2963 g, and the mass of Sample 2 was 0.9055 g. The calculated mass fraction of tannic acid in the samples was 13.80%.

[0052] The structural formula of the tea polyphenol-modified polyurethane is as follows:

[0053]

[0054] Example 2

[0055] In this embodiment, the molecular weight of polybutanediol is 1760, and the molecular weight of polyether 330N polyol is 4750.

[0056] (1) Add 45g of diphenylmethane diisocyanate and 55g of polybutane glycol to a 100mL three-necked flask, heat to 80℃, stir the raw materials at a rate of 200r / min to mix them evenly, and obtain polyurethane prepolymer after reacting for 4h.

[0057] (2) Take 0.3970g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to dissolve it completely. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1036mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 12.97%.

[0058] The ratio of the mass (g) of bromocresol blue to the volume (mL) of sodium hydroxide solvent in the bromocresol blue indicator is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0059] (3) Preheat the prepolymer titrated in step (2) to 50°C, and preheat the main raw materials polybutanediol, polyether 330N polyol and 1,4-butanediol after dehydration to 70°C.

[0060] (4) Add 36.61g of polybutanediol, 10.37g of polyether 330N polyol and 3.74g of 1,4-butanediol from step (3) to the container in sequence, and then add 46.55g of prepolymer. Stir the solution at a stirring rate of 2000r / min for 12s. Pour it into a polytetrafluoroethylene container and place it in an oven at 70℃ for 4h to cure, thus obtaining polyurethane elastomer.

[0061] (5) The polyurethane elastomer obtained in step (4) is immersed in 250 mL of tetrahydrofuran solution of tea polyphenols. At this time, the solution is dark brown. After immersion for 12 hours, the polyurethane is taken out and dried at room temperature for 12 hours to obtain polyurethane elastomer modified with tea polyphenols. The polyurethane modified with tea polyphenols is dark brown, which confirms that tea polyphenols have been successfully introduced into the polyurethane elastomer.

[0062] The ratio of the mass (g) of tea polyphenols to the volume (mL) of tetrahydrofuran is 5:250.

[0063] Samples of the polyurethane elastomer obtained in step (4), 1.3950 g and 1.0058 g, were named Sample 1 and Sample 2, respectively. Sample 1 was immersed in 18 ml of tetrahydrofuran solvent containing 0.45 g of tannic acid, and Sample 2 was immersed in 18 ml of tetrahydrofuran solvent. The immersion was carried out for 2 hours with a stirring rate of 600 r / min. The solid phases were then removed, dried at room temperature, and weighed. The mass of Sample 1 was 1.4781 g, and the mass of Sample 2 was 1.0351 g. The calculated mass fraction of tannic acid in the samples was 10.62%.

[0064] The structure of the tea polyphenol-modified polyurethane is the same as in Example 1.

[0065] Example 3

[0066] In this embodiment, the molecular weight of polybutanediol is 1760, and the molecular weight of polyether 330N polyol is 4800.

[0067] (1) Add 45g of diphenylmethane diisocyanate and 55g of polybutane glycol to a 100mL three-necked flask, heat to 80℃, stir the raw materials at a rate of 200r / min to mix them evenly, and obtain polyurethane prepolymer after reacting for 4h.

[0068] (2) Take 0.4244g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to fully dissolve it. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1036mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 11.52%.

[0069] The ratio of the mass (g) of bromocresol blue in the indicator to the volume (mL) of the solvent sodium hydroxide is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0070] (3) Preheat the prepolymer titrated in step (2) to 50°C, and preheat the main raw materials polybutanediol, polyether 330N polyol and 1,4-butanediol after dehydration to 70°C.

[0071] (4) Add 36.01g of polybutanediol, 9.91g of polyether 330N polyol and 3.74g of 1,4-butanediol from step (3) to the container in sequence, and then add 46.12g of prepolymer. Stir the solution at a stirring rate of 2000r / min for 12s. Pour it into a polytetrafluoroethylene container and place it in an oven at 70℃ for 4h to cure, thus obtaining polyurethane elastomer.

[0072] (5) The polyurethane elastomer obtained in step (4) is immersed in 250 mL of tetrahydrofuran solution of tea polyphenols. At this time, the solution is dark brown. After immersion for 12 hours, the polyurethane is taken out and dried at room temperature for 12 hours to obtain polyurethane elastomer modified with tea polyphenols. The polyurethane modified with tea polyphenols is dark brown, which confirms that tea polyphenols have been successfully introduced into the polyurethane elastomer.

[0073] The ratio of the mass (g) of tea polyphenols to the volume (mL) of tetrahydrofuran is 5:250.

[0074] Samples of the polyurethane elastomer obtained in step (4), 1.7923 g and 0.8901 g, were named Sample 1 and Sample 2, respectively. Sample 1 was immersed in 18 ml of tetrahydrofuran solvent containing 0.45 g of tannic acid, and Sample 2 was immersed in 18 ml of tetrahydrofuran solvent. The immersion was carried out for 2 hours with a stirring rate of 600 r / min. The solid phases were then removed, dried at room temperature, and weighed. The mass of Sample 1 was 1.8458 g, and the mass of Sample 2 was 0.9055 g. The calculated mass fraction of tannic acid in the samples was 5.01%.

[0075] The structure of the tea polyphenol-modified polyurethane is the same as in Example 1.

[0076] Example 4

[0077] In this embodiment, the molecular weight of polybutane glycol is 2080, and the molecular weight of polyether 330N polyol is 4600.

[0078] (1) Add 45g of diphenylmethane diisocyanate and 55g of polybutane glycol to a 100mL three-necked flask, heat to 80℃, stir the raw materials at a rate of 200r / min to mix them evenly, and obtain polyurethane prepolymer after reacting for 4h.

[0079] (2) Take 0.4036g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to dissolve it completely. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1036mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 10.84%.

[0080] The ratio of the mass (g) of bromocresol blue in the indicator to the volume (mL) of the solvent sodium hydroxide is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0081] (3) Preheat the prepolymer titrated in step (2) to 50°C, and preheat the main raw materials polybutanediol, polyether 330N polyol and 1,4-butanediol after dehydration to 70°C.

[0082] (4) Add 36.06g of polybutanediol, 9.91g of polyether 330N polyol and 3.75g of 1,4-butanediol from step (3) to the container in sequence, and then add 45.91g of prepolymer. Stir the solution at a stirring rate of 2000r / min for 12s. Pour it into a polytetrafluoroethylene container and place it in an oven at 70℃ for 4h to cure, thus obtaining polyurethane elastomer.

[0083] (5) The polyurethane elastomer obtained in step (4) is immersed in 250 mL of tetrahydrofuran solution of tannic acid. The solution is yellow at this time. After immersion for 12 h, the polyurethane is taken out and dried at room temperature for 12 h to obtain tannic acid modified polyurethane elastomer. The tannic acid modified polyurethane obtained at this time is yellow, which confirms that tannic acid has been successfully introduced into the polyurethane elastomer.

[0084] The ratio of the mass (g) of tannic acid to the volume (mL) of tetrahydrofuran is 5:250.

[0085] Samples of the polyurethane elastomer obtained in step (4), weighing 1.1152 g and 1.0058 g respectively, were named Sample 1 and Sample 2. Sample 1 was immersed in 18 ml of tetrahydrofuran solvent containing 0.45 g of tea polyphenols, and Sample 2 was immersed in 18 ml of tetrahydrofuran solvent. The samples were immersed for 2 hours with a stirring rate of 600 r / min. The solid phases were then removed, dried at room temperature, and weighed. The mass of Sample 1 was 1.2380 g, and the mass of Sample 2 was 1.0351 g. The calculated mass fraction of tea polyphenols in the samples was 20.07%.

[0086] The structural formula of the tannic acid-modified polyurethane is as follows:

[0087]

[0088] Example 5

[0089] In this embodiment, the molecular weight of polybutane glycol is 2080, and the molecular weight of polyether 330N polyol is 4750.

[0090] (1) Add 45g of diphenylmethane diisocyanate and 55g of polybutane glycol to a 100mL three-necked flask, heat to 80℃, stir the raw materials at a rate of 200r / min to mix them evenly, and obtain polyurethane prepolymer after reacting for 4h.

[0091] (2) Take 0.4066g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to dissolve it completely. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1036mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 12.76%.

[0092] The ratio of the mass (g) of bromocresol blue in the indicator to the volume (mL) of the solvent sodium hydroxide is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0093] (3) Preheat the prepolymer titrated in step (2) to 50°C, and preheat the main raw materials polybutanediol, polyether 330N polyol and 1,4-butanediol after dehydration to 70°C.

[0094] (4) Add 36.31g of polybutanediol, 10.03g of polyether 330N polyol and 3.74g of 1,4-butanediol from step (3) to the container in sequence, and then add 45.02g of prepolymer. Stir the solution at a stirring rate of 2000r / min for 12s. Pour it into a polytetrafluoroethylene container and place it in an oven at 70℃ for 4h to cure, thus obtaining polyurethane elastomer.

[0095] (5) The polyurethane elastomer obtained in step (4) is immersed in 250 mL of tetrahydrofuran solution of tannic acid. The solution is yellow at this time. After immersion for 12 h, the polyurethane is taken out and dried at room temperature for 12 h to obtain tannic acid modified polyurethane elastomer. The tannic acid modified polyurethane obtained at this time is yellow, which confirms that tannic acid has been successfully introduced into the polyurethane elastomer.

[0096] The ratio of the mass (g) of tannic acid to the volume (mL) of tetrahydrofuran is 5:250.

[0097] Samples of the polyurethane elastomer obtained in step (4), 1.3879 g and 0.8901 g, were named Sample 1 and Sample 2, respectively. Sample 1 was immersed in 18 ml of tetrahydrofuran solvent containing 0.45 g of tea polyphenols, and Sample 2 was immersed in 18 ml of tetrahydrofuran solvent. The immersion was carried out for 2 hours with a stirring rate of 600 r / min. The solid phases were then removed, dried at room temperature, and weighed. The mass of Sample 1 was 1.5107 g, and the mass of Sample 2 was 0.9055 g. The calculated mass fraction of tea polyphenols in the samples was 23.00%.

[0098] The structural formula of the tannic acid-modified polyurethane is the same as that in Example 4.

[0099] Example 6

[0100] In this embodiment, the molecular weight of polybutanediol is 2080, and the molecular weight of polyether 330N polyol is 4800.

[0101] (1) Add 45g of diphenylmethane diisocyanate and 55g of polybutane glycol to a 100mL three-necked flask, heat to 80℃, stir the raw materials at a rate of 200r / min to mix them evenly, and obtain polyurethane prepolymer after reacting for 4h.

[0102] (2) Take 0.3754g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to dissolve it completely. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1036mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 15.34%.

[0103] The ratio of the mass (g) of bromocresol blue in the indicator to the volume (mL) of the solvent sodium hydroxide is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0104] (3) Preheat the prepolymer titrated in step (2) to 50°C, and preheat the main raw materials polybutanediol, polyether 330N polyol and 1,4-butanediol after dehydration to 70°C.

[0105] (4) Add 36.23g of polybutanediol, 10.14g of polyether 330N polyol and 3.75g of 1,4-butanediol from step (3) to the container in sequence, and then add 36.02g of prepolymer. Stir the solution at a stirring rate of 2000r / min for 12s. Pour it into a polytetrafluoroethylene container and place it in an oven at 70℃ for 4h to cure, thus obtaining polyurethane elastomer.

[0106] (5) The polyurethane elastomer obtained in step (4) is immersed in 250 mL of tetrahydrofuran solution of tannic acid. The solution is yellow at this time. After immersion for 12 h, the polyurethane is taken out and dried at room temperature for 12 h to obtain tannic acid modified polyurethane elastomer. The tannic acid modified polyurethane obtained at this time is yellow, which confirms that tannic acid has been successfully introduced into the polyurethane elastomer.

[0107] The ratio of the mass (g) of tannic acid to the volume (mL) of tetrahydrofuran is 5:250.

[0108] Samples 1.0371g and 1.0058g of the polyurethane elastomer obtained in step (4) were named Sample 1 and Sample 2, respectively. Sample 1 was immersed in 18ml of tetrahydrofuran solvent containing 0.45g of tea polyphenols, and Sample 2 was immersed in 18ml of tetrahydrofuran solvent. The samples were immersed for 2 hours with a stirring rate of 600r / min. The solid phases were then removed, dried at room temperature, and weighed. The mass of Sample 1 was 1.1450g, and the mass of Sample 2 was 1.0351g. The calculated mass fraction of tea polyphenols in the samples was 17.27%.

[0109] The structural formula of the tannic acid-modified polyurethane is the same as that in Example 4.

[0110] The final products prepared in Examples 1-6 were subjected to infrared spectroscopy testing, and the results are as follows: Figure 1 As shown, it can be concluded that, compared to polyurethane elastomers, the infrared spectrum of the final product in Example 1 does not contain free-floating hydrogen bonds, and all 1729 cm⁻¹... -1 The unbonded carbonyl group at the 1700 cm⁻¹ flows away from the hydrogen bond. -1 The movement of hydrogen-bonded carbonyl groups indicates that the free carbonyl groups within the polyurethane were completely cross-linked and formed a large number of intermolecular hydrogen bonds after treatment with tea polyphenols. This contributes to the formation of a cross-linked network and improves the mechanical properties of the material. The infrared characterization results of the final products obtained in Examples 2 and 3 are similar to those in Example 1. Furthermore, compared to the polyurethane elastomer, the infrared spectrum of the final product in Example 4 contains only a small number of free hydrogen bonds, with most of them appearing at 1729 cm⁻¹. -1 The unbonded carbonyl group at the 1700 cm⁻¹ flows away from the hydrogen bond. -1 The movement of hydrogen-bonded carbonyl groups indicates that the free carbonyl groups within the polyurethane undergoing tannic acid treatment have extensively crosslinked and formed numerous intermolecular hydrogen bonds. This facilitates the formation of a crosslinked network and enhances the material's mechanical properties. The infrared characterization results of the final products obtained in Examples 5 and 6 are similar to those in Example 4.

[0111] Tensile tests were performed on the final products prepared in Examples 1-6. The test conditions were as follows: using a 500N mechanical sensor, selecting small test samples of 4mm × 50mm, and conducting the tests at a tensile rate of 20mm / min. The results are as follows. Figure 2 As shown, the mechanical properties of the polyurethane samples modified with polyphenols and subjected to heat treatment (the mechanical properties after tannic acid treatment are around 22 MPa, and the mechanical properties after tea polyphenol treatment are around 24 MPa) are improved by 46.7% and 60% respectively compared with the mechanical properties of ordinary polyurethane elastomers (around 15 MPa). This indicates that the polyphenol-modified polyurethane can be used as a type of polyurethane elastomer modifier to significantly improve the mechanical properties of polyurethane.

[0112] The self-healing properties of the final products prepared in Examples 1-6 were tested using tensile tests. The test method involved making a 2mm deep notch on the surface of the prepared polyphenol-modified polyurethane with a knife, adding two drops of tetrahydrofuran to the notch, and then bringing the two ends of the sample together. After 10 seconds, the sample was released and the cross-section was observed. At this point, the sample had completed the self-healing process and maintained its original shape, confirming that the sample possesses short-term self-healing properties. The test results for samples in Examples 2-3 were similar to those in Example 1, and the test results for samples in Examples 5-6 were similar to those in Example 4.

[0113] Comparative Example 1

[0114] The polyurethane elastomer described in Example 1 was immersed in 250 ml of ethanol solution of tannic acid. The solution was yellow at this time. After immersion for 12 hours, the polyurethane was removed and dried at room temperature for 12 hours to obtain tannic acid modified polyurethane elastomer. The tannic acid modified polyurethane obtained at this time was white, consistent with the polyurethane elastomer before modification, confirming that tannic acid was not successfully introduced into the polyurethane elastomer.

[0115] Comparative Example 2

[0116] The polyurethane elastomer described in Example 1 was immersed in 250 ml of a deionized aqueous solution of tannic acid. The solution was light yellow in color. After immersion for 12 hours, the polyurethane was removed and dried at room temperature for 12 hours to obtain a tannic acid-modified polyurethane elastomer. The tannic acid-modified polyurethane obtained at this time was white, consistent with the polyurethane elastomer before modification, confirming that tannic acid was not successfully introduced into the polyurethane elastomer.

[0117] Comparative Example 3

[0118] The polyurethane elastomer described in Example 1 was immersed in 250 ml of pure tetrahydrofuran solvent. The solution was colorless and transparent. After immersion for 12 hours, the polyurethane was removed and dried at room temperature for 12 hours to obtain tetrahydrofuran-modified polyurethane elastomer. Mechanical properties were tested on the sample under the following conditions: a 500 N mechanical sensor was used, and a small test sample of 4 mm × 50 mm was selected. The test was conducted at a tensile rate of 20 mm / min. The test structure is as follows. Figure 3 As shown, the tensile strength of a normal polyurethane sample is 13.11 MPa, while the tensile strength of the sample treated with tetrahydrofuran is reduced to 8.73 MPa, indicating a significant decrease in mechanical properties.

[0119] Comparative Example 4

[0120] The polyurethane elastomer described in Example 1 was immersed in 250 ml of pure N,N-dimethylformamide solvent. The solution was colorless and transparent. After immersion for 12 hours, the polyurethane was removed and dried at room temperature for 12 hours to obtain a tetrahydrofuran-modified polyurethane elastomer. Mechanical properties were tested on this sample using a 500 N mechanical sensor. Small test samples (4 mm × 50 mm) were selected, and the test was conducted at a tensile rate of 20 mm / min. The test structure is as follows. Figure 3 As shown, the tensile strength of a normal polyurethane sample is 13.11 MPa, while the tensile strength of the sample treated with N,N-dimethylformamide decreased to 9.02 MPa, indicating a significant decline in mechanical properties.

[0121] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A method for preparing a polyphenol-modified polyurethane elastomer, characterized in that: The polyurethane elastomer was immersed and stirred in an organic solution of polyphenols for 18–24 hours. After complete immersion, the solid phase was removed and dried at 25–70°C to obtain polyphenol-modified polyurethane elastomer. The organic solvent was tetrahydrofuran. The polyurethane elastomer is composed of hard segments and soft segments, and intermolecular hydrogen bonds are formed between the polyphenolic compound and the hard and soft segments of the polyurethane elastomer; the structural formula of the polyphenolic compound-modified polyurethane elastomer is as follows: Wherein, R' and R” are -H, -OH, C3-C5 alkyl groups, benzene rings, catechol or pyrogallol, respectively; ||||| represents intermolecular hydrogen bonds; and x ranges from 4 to 30.

2. The method for preparing a polyphenol-modified polyurethane elastomer as described in claim 1, characterized in that: The polyphenolic compound-modified polyurethane elastomer contains 5% to 25% polyphenolic compounds by mass.

3. The method for preparing a polyphenol-modified polyurethane elastomer as described in claim 1, characterized in that: The polyurethane elastomer is obtained by curing and molding components A and B. The raw materials used to prepare component A are based on a total mass of 100%, and the components and their mass fractions are as follows: diisocyanate substances 44%–46%, polypolyols 54%–56%. The raw materials used to prepare component B are based on a total mass of 100%, and the components and their mass fractions are as follows: polybutanediol 70%–74%, polyether 330N polyol 18%–22%, and diol chain extenders 4%–8%.

4. The method for preparing a polyphenol-modified polyurethane elastomer as described in claim 3, characterized in that: The diisocyanate is diphenylmethane diisocyanate; The diol chain extender is one or more of 1,4-butanediol, 1,3-propanediol, ethylene glycol, and 1,5-pentanediol; The molecular weight of the polyol is 1760-2080, and the molecular weight of the polyether 330N polyol is 4600-4800.

5. The method for preparing a polyphenol-modified polyurethane elastomer as described in claim 3, characterized in that: The polyurethane elastomer is prepared by the following method, the steps of which include: (1) Under the protection of protective gas, the raw materials of component A, diphenylmethane diisocyanate and polyol, are mixed, heated to 80-85°C, stirred and reacted for 4-5 hours, and then cooled to obtain viscous polyurethane prepolymer; (2) Under air-isolated conditions, the viscous polyurethane prepolymer is preheated to 40-50°C, and the polyol, polyether 330N polyol and diol chain extender in component B are preheated to 50-70°C. (3) Stir the preheated raw material in step (2) at a speed of 2000 r / min for 10-15 s, pour it into a polytetrafluoroethylene mold, and cure it at 65-75℃ for 2-4 h to obtain polyurethane elastomer.

6. The method for preparing a polyphenol compound-modified polyurethane elastomer as described in claim 5, characterized in that: The isocyanate content of the polyurethane prepolymer was determined by titration: the polyurethane prepolymer was added to isopropanol and heated and stirred at 45-55°C to dissolve it, thus obtaining a titration sample solution; then, the isocyanate content in the prepolymer was determined by titration using a toluene solution of bromocresol blue and di-n-butylamine as an indicator. The ratio of the polyurethane prepolymer to isopropanol is 3-4 g: 450-550 mL; the volume ratio of the titration sample solution to the di-n-butylamine toluene solution is 2:1; and the ratio of bromocresol blue to the titration sample solution is 1 g: 1000 mL.

7. The method for preparing a polyphenol-modified polyurethane elastomer as described in claim 5, characterized in that: The mass relationship between the polyurethane prepolymer, the polyol in component B, the polyether 330N polyol, and the diol chain extender satisfies the following formula: (m1×a%) / 42=R×((m2 / N1)×2+(m3 / N2)×3+(m4 / N3)×2) In the formula, m1, m2, m3, and m4 represent the masses of the polyurethane prepolymer, the polyol in component B, the polyether 330N polyol, and the diol chain extender, respectively; N1, N2, and N3 represent the molecular weights of the polyol in component B, the polyol in component B, the polyether 330N polyol, and the diol chain extender, respectively; a represents the isocyanate content of the polyurethane prepolymer; and R is the ratio of isocyanate to hydroxyl groups in the system, with R values ​​ranging from 1.04 to 1.

06.

8. The method for preparing a polyphenol-modified polyurethane elastomer as described in claim 1, characterized in that: The polyphenolic substances are punicin, gallic acid, tannic acid, or tea polyphenols.

9. The method for preparing a polyphenol-modified polyurethane elastomer as described in claim 1, characterized in that: The ratio of polyphenols to organic solvents is 4-5g: 200-250mL; the soaking process is carried out at 25-40℃ with a stirring speed of 200-500r / min.

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