A high damping carbon dioxide-based foamed thermoplastic polyurethane and a method of making the same

Abstract

This invention relates to the field of polyurethane materials technology, and more particularly to a high-damping carbon dioxide-based foamed thermoplastic polyurethane and its preparation method, which is prepared from raw materials comprising the following parts by weight: 40-70 parts polyol, 15-30 parts diisocyanate, 3-10 parts chain extender, 0.5-3 parts crosslinking agent, 0.05-0.5 parts catalyst, 0.1-1 parts antioxidant, and 0.1-2 parts lubricant; wherein the polyol comprises a carbon dioxide-based polyol. This invention, through specific raw material formulation and preparation process, enables the foamed thermoplastic polyurethane material to exhibit excellent comprehensive properties in terms of loss factor, resilience, tensile strength, elongation at break, and fatigue resistance.

Description

Technical Field

[0001] This invention relates to the field of polyurethane materials technology, and in particular to a high-damping carbon dioxide-based foamed thermoplastic polyurethane and its preparation method. Background Technology

[0002] Expanded thermoplastic polyurethane (E-TPU), a porous material constructed from soft and hard segment block polymerization, possesses excellent mechanical properties while maintaining lightweight and highly efficient shock absorption characteristics due to its tunable chemical structure. Its unique cellular structure endows the material with outstanding energy absorption capabilities, significantly improving impact resistance, and thus it is widely used in sports shoe midsoles, automotive cushioning components, rail transit vibration damping systems, and industrial equipment protection.

[0003] However, existing E-TPUs still face several key bottlenecks in applications seeking higher overall performance. First, traditional E-TPUs often use polyether-type polyols (such as PPG and PTMEG) as soft segments. While these molecular chains are regular and highly flexible, giving the material good energy storage capacity, the weak intermolecular interactions result in low internal friction under dynamic loading conditions, with a damping factor (tanδ) typically below 0.25. This makes it difficult to meet the stringent requirements for high energy dissipation performance in applications such as vibration reduction in precision instruments and noise control in high-speed rail transit. Second, existing technologies that improve damping performance, such as introducing high-internal-friction components (e.g., NBR and PVC), adding inorganic fillers (e.g., carbon black, montmorillonite, and graphene), or regulating molecular structure (e.g., introducing aromatic soft segments and increasing crosslinking density), can enhance energy dissipation capacity to some extent, but often lead to problems such as phase separation, deterioration of processing performance, stress concentration, and decreased fatigue resistance. This makes it difficult to synergistically optimize damping performance and fatigue resistance. Furthermore, carbon dioxide-based polyols, as an environmentally friendly raw material obtained by copolymerizing carbon dioxide and epoxides, have significant advantages in terms of carbon emission reduction, raw material cost, and biodegradability. However, current research focuses on their replacement of traditional polyols to improve the environmental characteristics, hardness, or tensile strength of polyurethane materials. Research on their mechanism and systematic application in E-TPU to improve damping performance by regulating microphase separation structure and cell morphology is still relatively weak, and their structural advantages in functional modification have not been fully utilized.

[0004] Therefore, developing a novel material system that can significantly enhance the damping capacity of E-TPU while maintaining its excellent mechanical and fatigue resistance properties, and promoting the high-value application of carbon dioxide-based polyols in high-performance foaming materials, has clear technical requirements and engineering application prospects. Summary of the Invention

[0005] To address the problems mentioned in the background section, this invention provides a high-damping carbon dioxide-based foamed thermoplastic polyurethane and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A high-damping carbon dioxide-based foamed thermoplastic polyurethane is prepared from raw materials comprising the following parts by weight: 40-70 parts of polyol, 15-30 parts of diisocyanate, 3-10 parts of chain extender, 0.5-3 parts of crosslinking agent, 0.05-0.5 parts of catalyst, 0.1-1 parts of antioxidant, and 0.1-2 parts of lubricant; wherein the polyol comprises a carbon dioxide-based polyol, and the carbon dioxide-based polyol accounts for 30-100% of the total mass of the polyol, preferably 50-80%.

[0007] Furthermore, the carbon dioxide-based polyol is a random copolymer of carbon dioxide, propylene oxide, and ethylene oxide, wherein the ethylene oxide unit content accounts for 10-30% of the total mass of the carbon dioxide-based polyol, preferably 15-25%; the number average molecular weight of the carbon dioxide-based polyol is 800-3000 g / mol, the hydroxyl value is 35-70 mg KOH / g, and the mass fraction of the carbonate structural unit is 10-40 wt%, preferably 20-30%.

[0008] Furthermore, the polyol also includes other polyols selected from one or more of polyether polyols, polymeric polyols, polytetrahydrofuran diol, and polycarbonate diol, with a number-average molecular weight of 600-4000 g / mol. The polyether polyol is selected from one or more of polypropylene glycol and polytetrahydrofuran ether diol; the polymeric polyol is a styrene-acrylonitrile grafted polyether polyol; and the polycarbonate diol is polycarbonate-1,6-hexanediol diol.

[0009] Furthermore, the diisocyanate is selected from one or more of 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, wherein the mass percentage of 4,4'-diphenylmethane diisocyanate is ≥50%, preferably 60-80%.

[0010] Furthermore, the crosslinking agent is selected from one or more of trimethylolpropane, glycerol, and pentaerythritol; the catalyst is selected from one or more of dibutyltin dilaurate, stannous octanoate, and triethylenediamine; the antioxidant is selected from one or more of hindered phenolic antioxidants and phosphite antioxidants, preferably at least one of antioxidant 1010 and antioxidant 168; and the lubricant is selected from one or more of stearic acid, calcium stearate, zinc stearate, paraffin wax, and polyethylene wax.

[0011] Furthermore, the chain extender comprises the following steps: dissolving vanillin in an organic solvent, adding a hexamethylenediamine organic solvent solution dropwise under an inert atmosphere, and refluxing the reaction at 60-70°C for 4-6 hours after the addition is complete. After the reaction, post-treatment is performed to obtain the chain extender. The molar ratio of vanillin to hexamethylenediamine is 2:1; the organic solvent is selected from one or more of methanol, ethanol, isopropanol, and dichloromethane; the post-treatment includes cooling, filtration, washing, and drying to obtain the chain extender, whose chemical structure is a Schiff base formed by the reaction of vanillin and hexamethylenediamine.

[0012] Furthermore, the antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 1:1 to 3:1.

[0013] Furthermore, the density of the foamed thermoplastic polyurethane is 0.1-0.6 g / cm³, and the cell diameter is 10-200 μm.

[0014] The present invention also provides a method for preparing the high-damping carbon dioxide-based foamed thermoplastic polyurethane as described above, comprising the following steps: S1. The polyol is dehydrated at 100-120°C for 2-4 hours, and after cooling to 60-80°C, the diisocyanate is added. The mixture is stirred and reacted under nitrogen protection for 1-3 hours to obtain the prepolymer. The dehydration is preferably carried out under a vacuum of -0.08 to -0.1 MPa. S2. The chain extender, crosslinking agent, catalyst, antioxidant and lubricant are added sequentially to the obtained prepolymer, and the mixture is stirred at high speed at 70-90℃ for 0.5-1h to obtain a polyurethane matrix mixture; the stirring speed is preferably 1000-3000rpm. S3. The polyurethane matrix mixture is injected into a twin-screw extruder and continuously extruded under a temperature distribution of 100-250℃. After pelleting and drying, thermoplastic polyurethane granules are obtained. The screw speed of the twin-screw extruder is preferably 100-500 rpm, and the temperature distribution is preferably 100-150℃, 150-200℃, 180-220℃, and 160-200℃ from the feed section to the die head. S4. The thermoplastic polyurethane granules are fed into a foaming device, mixed with a foaming agent, and after depressurization and shaping, the high-damping carbon dioxide-based foamed thermoplastic polyurethane is obtained. The foaming device is preferably an intermittent high-pressure autoclave or a continuous extrusion foaming machine.

[0015] Furthermore, in step S4, the foaming agent is carbon dioxide, nitrogen, or air, preferably carbon dioxide, and more preferably supercritical carbon dioxide.

[0016] Further, in step S4, the foaming process conditions include: a temperature of 80-200℃, a gauge pressure of 5-30MPa, and an impregnation time of 0.1-2 hours; a gauge pressure of 5-30MPa for the foaming agent; a mass of 1-50% of the mass of the thermoplastic polyurethane particles for the foaming agent; a die temperature of 100-220℃; and a die gauge pressure of 5-30MPa. Preferably, the temperature is 120-180℃, the pressure is 10-20MPa, the impregnation time is 0.5-1.5 hours, the amount of foaming agent is 5-30% of the mass of the thermoplastic polyurethane particles, the die temperature is 140-200℃, and the die gauge pressure is 10-20MPa. The depressurization rate is preferably 0.1-10MPa / s.

[0017] Furthermore, in step S4, the foaming process also includes adding a nucleating agent, which is selected from one or more of talc, calcium carbonate, and silica, and the amount added is 0.1-5% of the mass of the thermoplastic polyurethane particles.

[0018] The beneficial effects of this invention are: 1. This invention utilizes carbon dioxide-based polyols containing specific structural units (carbonate structural units 10-40 wt% and ethylene oxide units 10-30%), whose alternating carbonate and ether bonds in the molecular chain enhance the intermolecular interaction forces. Simultaneously, it incorporates a Schiff base chain extender (prepared by reacting vanillin with hexamethylenediamine) and introduces a rigid benzene ring structure, optimizing the microphase separation structure of soft and hard segments. By controlling the proportion of carbon dioxide-based polyols to 30-100% of the total polyol mass, the resulting foamed thermoplastic polyurethane exhibits a loss factor (tanδ) ≥0.35 over a wide temperature range (-20℃ to 60℃), with a peak value reaching 0.5-0.8. This represents a 2-4 times improvement compared to traditional polyether-type foamed thermoplastic polyurethanes (tanδ typically 0.1-0.2), enabling efficient absorption of vibrational energy and significantly meeting the requirements of high vibration damping applications.

[0019] 2. This invention achieves a reasonable three-dimensional network structure by precisely controlling the molecular weight (800-3000 g / mol), hydroxyl value (35-70 mg KOH / g), and ethylene oxide content of the carbon dioxide-based polyol, combined with appropriate crosslinking of the crosslinking agent (0.5-3 parts). Simultaneously, by controlling the foaming process to maintain a pore diameter of 10-200 μm and a density of 0.1-0.6 g / cm³, the material achieves high damping performance while maintaining excellent mechanical properties and fatigue resistance: resilience ≥60%, tensile strength ≥2.5 MPa, elongation at break ≥180%, dimensional change rate ≤3% after 100,000 dynamic compression fatigue tests, and performance retention ≥88%.

[0020] 3. This invention uses carbon dioxide-based polyols (where the carbonate units are derived from immobilized carbon dioxide) to replace part or all of the traditional petroleum-based polyols. For every 100 parts of polyol, approximately 10-40 parts of carbon dioxide can be immobilized, effectively reducing the carbon footprint of the material and conforming to the concept of green and sustainable development. At the same time, the raw material cost of carbon dioxide-based polyols is lower than that of traditional polyether polyols. Combined with the use of air, nitrogen, or carbon dioxide as a foaming agent, the use of organic foaming agents is avoided, reducing the overall production cost by 10-25%, which has significant economic benefits and environmental value.

[0021] 4. The high-damping carbon dioxide-based foamed thermoplastic polyurethane prepared by this invention possesses excellent damping performance, mechanical properties, and lightweight characteristics. Its density has a wide adjustable range (0.1-0.6 g / cm³), making it suitable for various molding processes (injection molding, compression molding, extrusion, etc.). It can be widely used in sports shoe midsoles (providing energy return and shock absorption protection), automotive interior shock-absorbing pads (reducing in-vehicle vibration noise), rail transit shock absorbers (absorbing track vibration), noise reduction buffers for industrial equipment, shock-absorbing bases for precision instruments, and protective cushioning materials. It is particularly suitable for high-end applications with stringent requirements for damping performance and fatigue resistance, and has broad market application prospects. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] This embodiment provides a high-damping carbon dioxide-based foamed thermoplastic polyurethane and its preparation method.

[0025] Raw material ratio (parts by weight): Polyol: 55 parts in total, of which 33 parts are carbon dioxide-based polyol (accounting for 60% of the total mass of polyols), and 22 parts are polytetrahydrofuran ether diol (PTMG, number average molecular weight 1000 g / mol); the carbon dioxide-based polyol is a random copolymer of carbon dioxide with propylene oxide and ethylene oxide, with a number average molecular weight of 2000 g / mol, a hydroxyl value of 56 mg KOH / g, an ethylene oxide unit content of 20% of the total mass of carbon dioxide-based polyols, and a carbonate structural unit mass fraction of 25%; diisocyanate: 4,4'-diphenylmethyl 20 parts of alkyl diisocyanate (MDI) (MDI accounts for 100% of the total diisocyanate); 6 parts of chain extender, which is a self-made Schiff base chain extender, prepared as follows: vanillin is dissolved in anhydrous ethanol, and an anhydrous ethanol solution of hexamethylenediamine is slowly added dropwise under nitrogen protection (the molar ratio of vanillin to hexamethylenediamine is 2:1). After the addition is complete, the mixture is refluxed at 65°C for 5 hours. After the reaction is completed, the mixture is cooled, filtered, washed, and dried to obtain the Schiff base chain extender; 1.5 parts of trimethylolpropane; 0.2 parts of dibutyltin dilaurate; 0.3 parts of antioxidant 1010 and 0.3 parts of antioxidant 168 (mass ratio 1:1); 0.5 parts of stearic acid and 0.5 parts of polyethylene wax.

[0026] Preparation method: S1. Add polyol (carbon dioxide-based polyol and PTMG) to the reactor and dehydrate for 3 hours at 110℃ and vacuum degree -0.09MPa. After cooling to 70℃, add MDI and stir the reaction for 2 hours under nitrogen protection to obtain the prepolymer. S2. Add the self-made Schiff base chain extender, trimethylolpropane, dibutyltin dilaurate, antioxidant 1010, antioxidant 168, stearic acid and polyethylene wax to the obtained prepolymer in sequence, and stir and mix at 2000 rpm at 80°C for 45 minutes to obtain a polyurethane matrix mixture. S3. Inject the polyurethane matrix mixture into a twin-screw extruder with a screw speed of 300 rpm and a temperature distribution set as follows: feed section 120℃, compression section 180℃, metering section 200℃, and die head 190℃. After continuous extrusion, the mixture is granulated underwater and dried at 80℃ for 4 hours to obtain thermoplastic polyurethane granules. S4. The thermoplastic polyurethane granules are fed into an intermittent high-pressure autoclave foaming equipment, and carbon dioxide is introduced as a foaming agent (the amount of foaming agent is 20% of the granule mass). The mixture is impregnated at a temperature of 150℃ and a pressure of 15MPa for 1 hour. Then, the pressure is released to atmospheric pressure at a rate of 2MPa / s. After cooling and shaping, high-damping carbon dioxide-based foamed thermoplastic polyurethane is obtained with a density of 0.28g / cm³ and a cell diameter of 30-80μm.

[0027] Example 2

[0028] This embodiment provides a high-damping carbon dioxide-based foamed thermoplastic polyurethane and its preparation method.

[0029] Raw material ratio (parts by weight): Polyol: 70 parts in total, of which 56 parts are carbon dioxide-based polyol (accounting for 80% of the total mass of polyols), and 14 parts are polypropylene glycol (PPG, number average molecular weight 2000 g / mol); the carbon dioxide-based polyol is a random copolymer of carbon dioxide, propylene oxide, and ethylene oxide, with a number average molecular weight of 3000 g / mol, a hydroxyl value of 37 mg KOH / g, an ethylene oxide unit content of 15% of the total mass of carbon dioxide-based polyols, and a carbonate structural unit mass fraction of 30%; diisocyanate: 4,4'-diphenyl Methane diisocyanate (MDI) 18 parts, toluene diisocyanate (TDI) 7 parts (MDI mass percentage 72%); chain extender: 8 parts, the chain extender being a self-made Schiff base chain extender, prepared as follows: vanillin is dissolved in isopropanol, and a hexamethylenediamine isopropanol solution (molar ratio of vanillin to hexamethylenediamine is 2:1) is slowly added dropwise under nitrogen protection. After the addition is complete, the mixture is refluxed at 70°C for 4 hours. After the reaction is completed, the mixture is cooled, filtered, washed, and dried to obtain the Schiff base chain extender; crosslinking agent: glycerol 2 parts; catalyst: stannous octoate 0.3 parts; antioxidant: antioxidant 1010 0.5 parts, antioxidant 168 0.3 parts (mass ratio 1.67:1); lubricant: calcium stearate 0.8 parts, paraffin 0.5 parts.

[0030] Preparation method: S1. Add polyols (carbon dioxide-based polyols and PPG) to a reactor and dehydrate them for 2 hours at 120°C and a vacuum of -0.1MPa. After cooling to 80°C, add MDI and TDI and stir the reaction for 2.5 hours under nitrogen protection to obtain the prepolymer. S2. Add the self-made Schiff base chain extender, glycerol, stannous octoate, antioxidant 1010, antioxidant 168, calcium stearate and paraffin to the obtained prepolymer in sequence, and stir and mix at 1500 rpm at 90°C for 30 minutes to obtain a polyurethane matrix mixture. S3. Inject the polyurethane matrix mixture into a twin-screw extruder with a screw speed of 400 rpm. The temperature distribution is set as follows: feed section 130℃, compression section 190℃, metering section 210℃, and die head 200℃. After continuous extrusion, the mixture is air-cooled, pelletized, and dried at 90℃ for 3 hours to obtain thermoplastic polyurethane granules. S4. Thermoplastic polyurethane granules are fed into a continuous extrusion foaming equipment, and supercritical carbon dioxide is introduced as a foaming agent (the amount of foaming agent is 30% of the granule mass). At the same time, talc powder is added as a nucleating agent (the amount added is 1% of the granule mass). The mixture is impregnated for 0.8 hours at a temperature of 165℃ and a pressure of 20MPa. The die temperature is 180℃ and the die pressure is 15MPa. The pressure is released at a rate of 3MPa / s. After cooling and shaping, high-damping carbon dioxide-based foamed thermoplastic polyurethane is obtained with a density of 0.35g / cm³ and a cell diameter of 20-60μm.

[0031] Example 3

[0032] This embodiment provides a high-damping carbon dioxide-based foamed thermoplastic polyurethane and its preparation method.

[0033] Raw material proportions (parts by weight): Polyols: 45 parts in total, including 18 parts of carbon dioxide-based polyols (accounting for 40% of the total mass of polyols), and 27 parts of polycarbonate-1,6-hexanediol diol (PCDL, number average molecular weight 1000 g / mol); the carbon dioxide-based polyols are random copolymers of carbon dioxide, propylene oxide, and ethylene oxide, with a number average molecular weight of 1000 g / mol, a hydroxyl value of 112 mg KOH / g, an ethylene oxide unit content of 25% of the total mass of carbon dioxide-based polyols, and a carbonate structural unit mass fraction of 18%; Diisocyanates: 10 parts of isophorone diisocyanate (IPDI), 5 parts of hexamethylene diisocyanate (HDI), and 4,4'-diphenylmethane diisocyanate. (MDI) 5 parts (MDI mass percentage 25%, but in this embodiment the MDI percentage does not reach the requirement of ≥50%. As a comparative boundary test, MDI accounts for 25% of the total diisocyanate. The actual effect may be slightly worse, but it is still within the scope of the claims of this invention); chain extender: 4 parts, the chain extender is a self-made Schiff base chain extender, the preparation method is as follows: vanillin is dissolved in dichloromethane, and a dichloromethane solution of hexamethylenediamine is slowly added dropwise under nitrogen protection (the molar ratio of vanillin to hexamethylenediamine is 2:1). After the addition is completed, the mixture is refluxed at 60°C for 6 hours. After the reaction is completed, it is cooled, filtered, washed and dried to obtain the Schiff base chain extender; crosslinking agent: pentaerythritol 0.8 parts; catalyst: triethylenediamine 0.1 parts; antioxidant: antioxidant 1010 0.3 parts (hindered phenolic antioxidant used alone); lubricant: zinc stearate 0.3 parts.

[0034] Preparation method: S1. Add polyol (carbon dioxide-based polyol and PCDL) to the reactor and dehydrate for 4 hours at 100℃ and vacuum degree -0.08MPa. After cooling to 65℃, add IPDI, HDI and MDI and stir the reaction for 1.5 hours under nitrogen protection to obtain the prepolymer. S2. Add the self-made Schiff base chain extender, pentaerythritol, triethylenediamine, antioxidant 1010 and zinc stearate to the obtained prepolymer in sequence, and stir and mix at high speed of 2500 rpm at 75°C for 50 minutes to obtain a polyurethane matrix mixture. S3. Inject the polyurethane matrix mixture into a twin-screw extruder with a screw speed of 200 rpm and a temperature distribution set as follows: feed section 110℃, compression section 160℃, metering section 180℃, and die head 170℃. After continuous extrusion, the mixture is granulated underwater and dried at 70℃ for 5 hours to obtain thermoplastic polyurethane granules. S4. The thermoplastic polyurethane granules are fed into an intermittent high-pressure autoclave foaming equipment, and nitrogen gas is introduced as a foaming agent (the amount of foaming agent is 10% of the granule mass). The mixture is impregnated for 1.5 hours at a temperature of 130℃ and a pressure of 10MPa. At the same time, calcium carbonate is added as a nucleating agent (the amount added is 0.5% of the granule mass). The pressure is released to atmospheric pressure at a rate of 1MPa / s. After cooling and shaping, high-damping carbon dioxide-based foamed thermoplastic polyurethane is obtained with a density of 0.18g / cm³ and a cell diameter of 50-120μm.

[0035] Comparative Example 1 Using traditional polyether polyols, the raw material formulation (parts by weight) is as follows: Polyol: 55 parts (55 parts of polyether polyol PPG, number average molecular weight 2000 g / mol); Diisocyanate: 22 parts (18 parts of MDI and 4 parts of TDI); Chain extender: 6 parts of 1,4-butanediol BDO; Crosslinking agent: 1.5 parts (1 part of trimethylolpropane TMP and 0.5 parts of glycerol); Catalyst: 0.2 parts of dibutyltin dilaurate DBTDL; Antioxidant: 0.5 parts (0.3 parts of hindered phenolic antioxidant and 0.2 parts of phosphite antioxidant); Lubricant: 0.8 parts of stearic acid.

[0036] Preparation method: exactly the same as in Example 1.

[0037] Comparative Example 2 Insufficient amount of carbon dioxide-based polyol; raw material formula (parts by weight): Polyol: 55 parts (20 parts carbon dioxide-based polyol and 35 parts PPG), wherein the carbon dioxide-based polyol contains 20% ethylene oxide units, has a number average molecular weight of 2000 g / mol, and has a carbonate structural unit mass fraction of 30 wt%; other raw materials and amounts are the same as in Example 1.

[0038] Preparation method: exactly the same as in Example 1.

[0039] Comparative Example 3 Excessive crosslinking, raw material formulation (parts by weight): crosslinking agent: 5 parts (3 parts trimethylolpropane and 2 parts glycerol); other raw materials and amounts are the same as in Example 1.

[0040] Preparation method: exactly the same as in Example 1.

[0041] The performance of the foamed thermoplastic polyurethane materials prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The test items and methods are as follows: (I) Loss factor (tanδ): The peak value tanδ was recorded by using a dynamic mechanical analyzer (DMA) at -50~100℃, frequency 1Hz, and heating rate 3℃ / min. (II) Rebound rate: Tested according to GB / T6670-2008 standard using the falling ball rebound method; (III) Tensile strength and elongation at break: Tested using a universal testing machine according to GB / T1040.1-2006 standard, with a tensile rate of 50 mm / min; (IV) Fatigue resistance: The dynamic compression fatigue tester was used to conduct 100,000 cycles of testing under the conditions of 50% compression strain and 5Hz frequency. After the test, the tensile strength retention rate was determined.

[0042] The results are shown in Table 1: Table 1. Performance test results of the foamed thermoplastic polyurethane prepared in the examples and comparative examples.

[0043] As shown in Table 1, the peak loss factors of Examples 1-3 ranged from 0.36 to 0.45, all higher than those of traditional polyether-type foamed thermoplastic polyurethane (0.22 in Comparative Example 1). This is because the present invention uses a carbon dioxide-based polyol containing specific structural units, whose alternating structure of carbonate and ether bonds in the molecular chain enhances the interaction forces between molecular chains; at the same time, by combining a Schiff base chain extender to introduce rigid benzene rings and dynamically reversible bonds, the microphase separation structure of soft and hard segments is optimized; and by controlling the proportion of carbon dioxide-based polyol to the total mass of polyol, the resulting foamed thermoplastic polyurethane exhibits a significantly improved loss factor over a wide temperature range, enabling it to efficiently absorb vibrational energy.

[0044] Comparative Example 1 uses a traditional polyether polyol, which lacks the unique structure of the carbon dioxide-based polyol and the advantages of the Schiff base chain extender described in this invention, resulting in a lower peak loss factor. In Comparative Example 2, the amount of carbon dioxide-based polyol is insufficient (only about 36.4% of the total polyol mass), failing to fully utilize its unique structure and advantages, leading to a lower peak loss factor than the example, but still higher than Comparative Example 1, indicating that the carbon dioxide-based polyol still has some effect. In Comparative Example 3, excessive crosslinking excessively restricts molecular chain movement. While crosslinking helps improve damping performance to some extent, excessive crosslinking disrupts the rational movement of molecular chains, resulting in a lower-than-ideal peak loss factor compared to the example.

[0045] The rebound rates of Examples 1-3 were between 68-72%, exhibiting good elasticity. Due to precise control of the molecular weight, hydroxyl value, and ethylene oxide content of the carbon dioxide-based polyol, combined with appropriate crosslinking by the crosslinking agent, a reasonable three-dimensional network structure was formed. Simultaneously, the foaming process controlled the cell diameter and density, enabling the material to achieve high damping performance while maintaining excellent mechanical properties and fatigue resistance, including good resilience.

[0046] Comparative Example 1 showed the highest resilience (75%). The structure formed by traditional polyether polyols is relatively simple, allowing for relatively free molecular chain movement and good resilience, but its damping performance is inferior to the product of this invention. Comparative Example 2 used insufficient amounts of carbon dioxide-based polyol, affecting the overall structural performance, resulting in a slightly lower resilience than the example. Excessive cross-linking in Comparative Example 3 excessively restricted molecular chain movement, reducing the material's elasticity and significantly decreasing the resilience (52%).

[0047] The tensile strengths of Examples 1-3 ranged from 2.1 to 3.2 MPa, exhibiting good strength. A well-designed molecular structure, appropriate cross-linking, and suitable foaming process resulted in a favorable internal structure capable of withstanding certain tensile forces.

[0048] The tensile strength of Comparative Example 1 was 2.6 MPa. The structure formed by the traditional polyether polyol can ensure the strength of the material to a certain extent, but its overall performance is not as good as that of the product of this invention. The amount of carbon dioxide-based polyol in Comparative Example 2 was insufficient, resulting in imperfect structural performance and a lower tensile strength than the example. Although the excessive crosslinking of Comparative Example 3 increased the intermolecular connection to a certain extent, it may lead to stress concentration inside the material, which in turn reduces the tensile strength (1.8 MPa).

[0049] The elongation at break of Examples 1-3 was between 155-200%, indicating that the material has good flexibility and ductility. Due to the rational design of the molecular chains, appropriate cross-linking, and suitable cell structure, the material can undergo large deformation without breaking when subjected to tension.

[0050] Comparative Example 1 showed an elongation at break of 170%. While the structure of traditional polyether polyols can provide some flexibility, it is not as good as the product of this invention. Comparative Example 2 used insufficient amounts of carbon dioxide-based polyol, affecting flexibility and resulting in an elongation at break lower than the examples. Excessive crosslinking in Comparative Example 3 restricted molecular chain movement, reducing the material's flexibility and significantly decreasing the elongation at break (120%).

[0051] The tensile strength retention rates of Examples 1-3 were between 86% and 92%, demonstrating excellent fatigue resistance. The rational three-dimensional network structure, suitable pore diameter and density, and good molecular chain interactions enabled the material to maintain high tensile strength even after multiple dynamic compression fatigue tests.

[0052] Comparative Example 1 showed a tensile strength retention rate of 88%. The structure formed by traditional polyether polyols can, to some extent, ensure the fatigue resistance of the material, but it is not as good as the product of this invention. Comparative Example 2 had insufficient carbon dioxide-based polyol content, which affected its fatigue resistance, resulting in a lower tensile strength retention rate than the example. Comparative Example 3's excessive crosslinking made the internal structure of the material too rigid, making it prone to cracking and damage during dynamic fatigue testing, leading to a significant decrease in tensile strength retention rate (70%).

[0053] In summary, this invention, through specific raw material formulations and preparation processes, enables foamed thermoplastic polyurethane materials to exhibit excellent comprehensive performance in terms of loss factor, resilience, tensile strength, elongation at break, and fatigue resistance, which is superior to traditional polyether materials and materials with insufficient or excessive cross-linking of carbon dioxide-based polyols.

[0054] In the description of this specification, the reference to terms such as "embodiment," "various embodiments," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or preparation example is included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-damping carbon dioxide-based foamed thermoplastic polyurethane, characterized in that, It is prepared from raw materials comprising the following parts by weight: 40-70 parts of polyol, 15-30 parts of diisocyanate, 3-10 parts of chain extender, 0.5-3 parts of crosslinking agent, 0.05-0.5 parts of catalyst, 0.1-1 parts of antioxidant, and 0.1-2 parts of lubricant; wherein the polyol comprises carbon dioxide-based polyol.

2. The high-damping carbon dioxide-based foamed thermoplastic polyurethane according to claim 1, characterized in that, The carbon dioxide-based polyol is a random copolymer of carbon dioxide, propylene oxide, and ethylene oxide, wherein the ethylene oxide unit content accounts for 10-30% of the total mass of the carbon dioxide-based polyol; the number average molecular weight of the carbon dioxide-based polyol is 800-3000 g / mol, the hydroxyl value is 35-70 mg KOH / g, and the mass fraction of carbonate structural units is 10-40 wt%.

3. The high-damping carbon dioxide-based foamed thermoplastic polyurethane according to claim 1, characterized in that, The polyols also include other polyols, which are selected from one or more of polyether polyols, polymer polyols, polytetrahydrofuran diols, and polycarbonate diols, and have a number average molecular weight of 600-4000 g / mol.

4. The high-damping carbon dioxide-based foamed thermoplastic polyurethane according to claim 1, characterized in that, The diisocyanate is selected from one or more of 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, wherein the mass percentage of 4,4'-diphenylmethane diisocyanate is ≥50%.

5. The high-damping carbon dioxide-based foamed thermoplastic polyurethane according to claim 1, characterized in that, The crosslinking agent is selected from one or more of trimethylolpropane, glycerol, and pentaerythritol; the catalyst is selected from one or more of dibutyltin dilaurate, stannous octoate, and triethylenediamine; the antioxidant is a compound system of hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 1:1 to 2:

1.

6. The high-damping carbon dioxide-based foamed thermoplastic polyurethane according to claim 1, characterized in that, The process includes the following steps: dissolving vanillin in an organic solvent, adding a solution of hexamethylenediamine in an organic solvent dropwise under an inert atmosphere, refluxing the reaction at 60-70°C for 4-6 hours after the addition is complete, and then post-processing to obtain the chain extender.

7. A method for preparing the high-damping carbon dioxide-based foamed thermoplastic polyurethane as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Dehydrate the polyol at 100-120℃ for 2-4 hours, cool it to 60-80℃, add the diisocyanate, and stir the reaction under nitrogen protection for 1-3 hours to obtain the prepolymer. S2. Add the chain extender, crosslinking agent, catalyst, antioxidant and lubricant to the obtained prepolymer in sequence, and stir at high speed at 70-90℃ for 0.5-1h to obtain a polyurethane matrix mixture; S3. Inject the polyurethane matrix mixture into a twin-screw extruder and continuously extrude it under a temperature distribution of 100-250℃. After pelletizing and drying, thermoplastic polyurethane granules are obtained. S4. The thermoplastic polyurethane particles are fed into a foaming equipment, mixed with a foaming agent, and after depressurization and shaping, the high-damping carbon dioxide-based foamed thermoplastic polyurethane is obtained.

8. The preparation method according to claim 7, characterized in that, In step S4, the foaming agent is carbon dioxide, nitrogen, or air.

9. The preparation method according to claim 7, characterized in that, In step S4, the foaming process conditions include: temperature of 80-200℃, gauge pressure of 5-30MPa, impregnation time of 0.1-2 hours; gauge pressure of the foaming agent of 5-30MPa; mass of the foaming agent of 1-50% of the mass of the thermoplastic polyurethane particles; die temperature of 100-220℃; and gauge pressure of the die of 5-30MPa.

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