Preparation method and application of bio-based furan polyurethane honeycomb porous material

Abstract

The invention discloses a preparation method and application of a bio-based furan polyurethane honeycomb porous material. The bio-based furan polyurethane honeycomb porous material disclosed by the invention is prepared from bio-based polyether polyol / furan modified polyester polyol, dihydroxyl-terminated polysiloxane, diphenylmethane diisocyanate and a functional additive through step-by-step polymerization and wet-process solvent replacement. According to the invention, by introducing bio-based sourced compounds including furan modified polyester polyol, furan-2, 5-diformylhydrazine and poly trimethylene ether glycol, dihydroxyl-terminated polysiloxane is utilized to enhance an environmental barrier, and polyvinyl alcohol and polyamide wax are combined to regulate and control a phase separation process, so that the phase separation efficiency is improved; and finally, the bio-based furan polyurethane honeycomb porous material with a bionic honeycomb porous structure, extremely soft skin-friendly touch feeling and excellent rebound resilience is developed.

Description

Technical Field

[0001] This invention belongs to the field of bio-based polymeric furan polyurethane porous materials, specifically relating to a method for preparing a bio-based furan polyurethane honeycomb porous material and its application. Background Technology

[0002] With the rapid development of cutting-edge fields such as flexible electronics, smart wearable devices, and robotics, the demand for polymer materials that combine excellent mechanical properties, environmental friendliness, and functional adaptability is becoming increasingly urgent. Porous polyurethane materials, with their unique lightweight microporous structure, excellent flexibility, and tunable physicochemical properties, are considered one of the ideal candidate materials for these fields, showing potential in applications requiring high resilience, high energy absorption, or biomimetic tactile sensations. In the field of robotic biomimetic skin, using flexible materials such as aqueous polyurethane to simulate the feel of human skin has become an important research direction. Existing technologies are dedicated to optimizing material formulations and processes to make biomimetic skin increasingly closer to real skin in terms of lightweight, softness, and fit. Meanwhile, to meet the requirements of sustainable development, bio-based polyurethane has become a research hotspot. The latest technological advancements show that through innovative molecular design, the mechanical properties of bio-based polyurethane have achieved significant breakthroughs.

[0003] Despite the progress made in existing technologies, the following inherent contradictions and challenges remain in developing next-generation high-performance bio-based polyurethane porous materials suitable for applications such as robotic biomimetic skin:

[0004] 1. The Technological Gap Between High-Performance Elastomers and Porous Materials: Current cutting-edge research on bio-based polyurethanes focuses primarily on achieving the ultimate intrinsic mechanical properties (such as strength and toughness) of elastomers. However, the microphase separation behavior of molecular chains and the formation of cell structures during the foaming process of porous foam materials required for biomimetic skin are extremely complex. Directly applying the aforementioned furan ring rigid structure or dynamic hydrogen bond network design, suitable for dense elastomers, to the preparation of porous materials often interferes with foaming kinetics, leading to problems such as uneven cell structure, excessively wide pore size distribution, or excessively high closed-cell ratio. This uneven cell structure becomes stress defect points, severely affecting the material's resilience, durability, and tactile uniformity under repeated compression deformation.

[0005] 2. The Challenge of Balancing Mechanical Properties with Processability and Lightweighting: For biomimetic skin applications, materials need to provide durable support and resistance to collapse while maintaining sufficient softness (low modulus) and lightweightness. Current technologies often increase mechanical strength by adding rigid components such as furan rings or increasing cross-linking density, which often leads to material hardening and increased density, sacrificing a lightweight feel and fit. Conversely, pursuing extreme softness and lightweightness inevitably results in plastic deformation and weakening of support during long-term use. Therefore, achieving a precise synergy between rigidity and toughness, and between soft feel and durable support at the molecular framework level remains a bottleneck that current technologies have not yet ideally resolved.

[0006] 3. The Scalability Contradiction Between Bio-based Content, Performance, and Cost: Although furan-based bio-based platform compounds using furfural, 5-hydroxymethylfurfural (HMF), and other raw materials have achieved large-scale production, their application in polyurethane is still largely limited to some hard segments or chain extenders. To significantly improve the greenness of materials throughout their entire life cycle, it is necessary to increase the overall content of bio-based monomers. However, how to achieve controllable preparation and cost control of high bio-based content formulations without compromising the overall performance (cell quality, mechanical balance) of the aforementioned porous materials is a key obstacle from laboratory to industrialization.

[0007] In summary, existing technologies have not yet provided a solution with ideal overall performance. The fundamental problem lies in the failure to simultaneously resolve the contradiction between the uniformity of the pore structure, the balance of mechanical properties (rigidity and flexibility), and the high bio-based content in bio-based polyurethane in a porous morphology, starting from the molecular design stage. Therefore, the purpose of this invention is to provide a novel bio-based furan ring-modified polyurethane porous material and its preparation method to overcome the above-mentioned shortcomings. Specifically, it aims to achieve the following technical effects: by introducing furan rings, the microphase separation behavior of soft and hard segments is precisely controlled at the molecular level, thereby directly inducing the formation of a uniform and stable pore structure during the foaming process; on this basis, the material simultaneously possesses excellent soft touch, high resilience, fatigue resistance, and sufficient rigid support; and ensures that the material system has a significant bio-based carbon content to meet the dual requirements of high performance and green environmental protection, making it particularly suitable for advanced application fields such as robotic bionic skin with stringent standards for touch, durability, and environmental friendliness. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing a bio-based furan-based polyurethane honeycomb porous material and its application. This invention synergistically constructs a polyurethane network using bio-based polyether polyols / furan-based polyester polyols, hydroxyl-terminated polysiloxanes, and diphenylmethane-4,4'-diisocyanate (MDI). Silicone oil segments provide smoothness, the furan structure introduces rigidity and reactive sites, and the aromatic structure in MDI provides support and resilience. The molecular weight and hard segment ratio are controlled by chain extenders ethylene glycol / bio-based furanoyl hydrazine, and the cell structure is further modified with polyvinyl alcohol and polyamide wax. A DMF solution-hot water solvent displacement process is used to induce phase separation, ultimately forming a bio-based furan polyurethane material with a uniform honeycomb cell structure. This material possesses low-modulus softness and skin-friendliness, reversible self-healing / reprocessing properties based on furan groups, excellent fast resilience, and low density, providing a novel, comfortable, and intelligent material solution for biomimetic robotic skin that combines excellent mechanical properties with environmentally friendly characteristics.

[0009] The bio-based furan-based polyurethane honeycomb porous material of the present invention comprises the following raw materials by mass percentage:

[0010]

[0011] The polymer polyol is selected from one or more of polyether polyols and furanyl polyester polyols; the number average molecular weight of the polymer polyol is 2000-4000 g / mol.

[0012] The polyether polyol is either bio-based or non-bio-based. Specifically, the bio-based polyether polyol is polytrimethylene ether glycol (commercially available), and the non-bio-based polyether polyol is polytetramethylene ether glycol (commercially available).

[0013] Furthermore, the polymeric polyol includes polyether polyol and furanyl polyester polyol, wherein the mass ratio of polyether polyol to furanyl polyester polyol is 4-6:1.

[0014] Furthermore, the furan-based polyester polyol is poly(adipic acid-furandicarboxylic acid-hexanediol ester diol).

[0015] The hydroxyl-terminated polysiloxane is selected from α,ω-dihydroxy polydimethylsiloxane and hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of 2000-4000 g / mol.

[0016] Furthermore, the total mass percentage of the polymer polyol and the double-hydroxyl-terminated polysiloxane is 11%.

[0017] The chain extender is one or more of ethylene glycol and bio-based furanoyl hydrazide (such as furan-2,5-dicarboxyhydrazide).

[0018] Furthermore, the chain extender comprises ethylene glycol and bio-based furanoyl hydrazine, wherein the mass ratio of ethylene glycol to bio-based furanoyl hydrazine is 1:2 to 2:1.

[0019] This invention relates to a bio-based furan-based polyurethane honeycomb porous material, which is formed by prepolymerizing furan-modified polyester polyol and bi-hydroxyl-terminated polysiloxane as soft segments, and obtaining a resin by prepolymerization, chain extension / end-capping with diphenylmethane diisocyanate, and then blending it with polyvinyl alcohol and polyamide wax. The solution is then subjected to hot water solvent displacement induced phase separation to form the material.

[0020] The present invention discloses a method for preparing a bio-based furan-based polyurethane honeycomb porous material, comprising the following steps:

[0021] (1) Prepolymerization reaction and raw material processing: The polymer polyol and the hydroxyl-terminated polysiloxane were put into the reactor and stirred under vacuum at 120°C for 2 h; then the temperature was lowered to 70°C and a portion of diphenylmethane-4,4′-diisocyanate (MDI) was added. The molar ratio of hydroxyl to isocyanate groups in the system was controlled to be 1:2 for reaction. The reaction was carried out until the viscosity of the reaction liquid reached 130-150 Pa·s / 50°C, thus completing the first step of the prepolymerization reaction.

[0022] (2) Chain extension and end-capping reaction: Add the remaining diphenylmethane-4,4′-diisocyanate (MDI) and chain extender to the reaction vessel, control the total isocyanate index of the system to be 1 (i.e., the equivalent ratio of isocyanate group (NCO) to hydroxyl group (-OH) is 1:1), and carry out the chain extension reaction; during this period, add N,N-dimethylformamide (DMF) in 4-5 batches to adjust the solution concentration, and continue the reaction until the viscosity of the system drops to 20-30 Pa·s / 50℃, and add methanol to end-cap the remaining isocyanate groups.

[0023] (3) Blending reaction and resin preparation: Polyvinyl alcohol 0588 powder and polyamide wax are added to the reaction system and stirred and blended at a certain temperature (60-100 ℃) until the system is evenly dispersed to obtain wet resin.

[0024] (4) Wet molding and post-treatment: After vacuum stirring to remove bubbles, the obtained wet resin is transferred to hot water at 40-60℃ and left to stand for 12 hours to set, and then dynamically stirred for 24 hours; the molding material is then placed in an oven to dry, and finally bio-based furan polyurethane honeycomb porous material is obtained.

[0025] The application of the bio-based furan-based polyurethane honeycomb porous material prepared by this invention in the preparation of biomimetic robot skin materials, medical flexible materials, or flexible electronic devices.

[0026] For example, the bio-based furan-based polyurethane honeycomb porous material is used to make the skin layer of a biomimetic robot. The skin layer has a honeycomb pore structure similar to biological soft tissue, excellent soft and skin-friendly feel, and ideal mechanical cushioning and breathability.

[0027] This invention achieves a breakthrough in the comprehensive performance of materials through precise molecular structure design and synergistic process control: Furan-modified polyester polyols are used as active soft segments, synergistically combined with dihydroxyl-terminated polysiloxanes to construct a composite polymer network. The furan rings provide the supporting structure, while the siloxane segments form a hydrophobic barrier through surface enrichment. The switchable design of chain extenders (ethylene glycol / bio-based furanoyl hydrazine) enables the tunability of the hard segments—ethylene glycol constructs urethane bonds, while furanoyl hydrazine introduces multiple hydrogen bonds to enhance the mechanical properties of the polyurethane. Utilizing the synergistic effect of batch-added DMF solvent and polyvinyl alcohol / polyamide wax, phase separation is induced by solvent-water bidirectional diffusion in a hot water bath. Precise control of phase separation kinetics ultimately results in a honeycomb-like three-dimensional porous structure with uniform pore size, intact pore walls, and interconnected pores. This technical solution achieves a dual synergy of softness and elasticity at the molecular level, as well as environmental friendliness, providing an innovative solution for developing next-generation green biomimetic skin materials.

[0028] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0029] 1. Achieving Synergistic Innovation and Fundamental Breakthrough in Performance: This invention innovatively introduces furan-modified polyester polyols as bio-based functional soft segments and copolymerizes them with dihydroxyl-terminated polysiloxanes. This synergistically constructs a polyurethane network at the molecular level, combining bio-based origin, multiple hydrogen bond synergy (from bio-based furanyl hydrazine chain extenders), and a long-lasting solvent-repellent barrier. Simultaneously, by utilizing the physical thickening and nucleation regulation effects of polyvinyl alcohol and polyamide wax, precise control of the phase separation process is achieved during wet solidification molding. This solves the problem of large and uneven pores in traditional porous materials, achieving a highly uniform and stable honeycomb structure that integrates environmental friendliness, structural precision, and soft, elastic, and durable properties.

[0030] 2. Imbuing Robotic Skin with Realistic and Adaptive Capabilities: This material represents a qualitative leap forward in the field of robotic skin. Its precisely constructed honeycomb porous structure serves as an ideal biomimetic platform, perfectly mimicking the mechanical cushioning, soft touch, and breathability of biological tissue, providing an excellent substrate for the integration of various flexible sensors and electronic components. More importantly, the material's built-in bio-based furanoyl hydrazine-based multi-hydrogen bond network endows it with inherent self-healing capabilities. Combined with the superior anti-aging and media resistance provided by the siloxane segments, this constitutes a "dual lifespan guarantee" mechanism for the material in complex dynamic environments. This allows the robotic skin to not only maintain functional stability over a long period but also to shift from passive wear and tear to active maintenance, greatly improving the system's reliability and service life. Attached Figure Description

[0031] Figure 1 A scanning electron microscope image (150x magnification) showing the pore structure of the porous material prepared by the wet-process resin in Example 1 of the present invention.

[0032] Figure 2 A scanning electron microscope image (150x magnification) of the cross-section of the porous material made from the wet-process resin of Example 2 of the present invention.

[0033] Figure 3 A scanning electron microscope image (150x magnification) of the cross-section of the porous material made from the wet-process resin of Example 3 of the present invention.

[0034] Figure 4 A scanning electron microscope image (150x magnification) of the cross-section of the porous material made from the wet-process resin of Example 4 of the present invention.

[0035] Figure 5 A scanning electron microscope image (150x magnification) of the cross-section of the porous material made from the wet-process resin of Example 5 of the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments.

[0037] The poly(hexanediol adipate-furandicarboxylic acid) diol used in the examples was prepared by the following method:

[0038] Weigh 1670g of furanyl dicarboxylic acid (FDCA) and 2276g (19.26mol) of 1,6-hexanediol (HDO) and add them to a three-necked flask. Place the flask with the raw materials in an oil bath at 190℃ and react for 12 hours under a nitrogen atmosphere. Then, cool down to 170℃, add the catalyst tetrabutyl titanate (TBT), stir and react for 1 hour, raise the oil bath temperature to 230℃, and continue reacting for 10 hours. Take a sample to test the acid value and separate poly(adipic acid-furanyl dicarboxylic acid-hexanediol) diol.

[0039] Example 1:

[0040] 1. Formula

[0041]

[0042] 2. Preparation method

[0043] In a reaction vessel, 6.44 kg of polytrimethylene ether glycol (number average molecular weight 4000 g / mol), 1.38 kg of polyhexane-furandicarboxylate diol (number average molecular weight 3000 g / mol), and 0.46 kg of dihydroxyl-terminated polysiloxane (number average molecular weight 2000 g / mol) were added. The mixture was then evacuated to -0.1 MPa at 120°C and stirred to remove water for 2–3 h. The temperature was lowered to 70°C, and 1.15 kg of diphenylmethane-4,4'-diisocyanate (MDI) was added. After reacting for 2–3 h, when the viscosity of the reaction solution reached 130–150 Pa·s / 50°C, the remaining 1.73 kg of diphenylmethane-4,4'-diisocyanate and 0.43 kg of ethylene glycol (chain extender) were added to the reaction vessel. The chain extension reaction was carried out at 70-80℃, with N,N-dimethylformamide solution added to dilute the concentration during the chain extension process. After 3-4 hours of reaction, the reaction temperature was lowered to 40-50℃, and 0.42 kg of furanyl hydrazine, a chain extender, was added. The reaction was continued for 1-2 hours, with N,N-dimethylformamide added to dilute the viscosity during this period. The total amount of N,N-dimethylformamide added was 70 kg. When the viscosity of the reaction solution reached 20-30 Pa·s at 50℃, 6 g of methanol was added to end-cap the free isocyanate. Finally, 17.76 kg of polyvinyl alcohol 0588 powder and 0.24 kg of polyamide wax were added for blending reaction. The reaction was continued for 4-6 hours. When the viscosity of the reaction solution reached 10-30 Pa·s / 50℃, the reaction was stopped to obtain the wet-process resin. After the obtained wet-process resin was vacuum stirred and degassed, it was transferred to 50°C hot water for static setting and dynamic stirring for 12 h; then the molded material was placed in a 70°C oven to dry, and finally a bio-based furan polyurethane honeycomb porous material was obtained.

[0044] Example 2:

[0045] 1. Formula

[0046]

[0047] 2. Preparation method

[0048] 7.97 kg of polytetramethylene ether glycol (number average molecular weight 4000 g / mol) and 0.44 kg of dihydroxyl-terminated polysiloxane (number average molecular weight 2000 g / mol) were added to a reactor. The reactor was evacuated to -0.1 MPa at 120°C and stirred to remove water for 2–3 hours. The temperature was then lowered to 70°C, and 1.11 kg of diphenylmethane-4,4'-diisocyanate (MDI) was added. After reacting for 2–3 hours, when the viscosity of the reaction solution reached 130–150 Pa·s / 50°C, the remaining 1.66 kg of diphenylmethane-4,4'-diisocyanate and 0.82 kg of ethylene glycol (a chain extender) were added to the reactor for chain extension. The reaction temperature was controlled at 70–80°C. During chain extension, N,N-dimethylformamide was added to bring the concentration to 70 kg of diluted solution. After reacting for 3–4 hours, when the viscosity of the reaction solution reached 20–30 Pa·s / 50°C, 6 kg of methanol was added. g was used to cap free isocyanate groups; finally, 17.76 kg of polyvinyl alcohol 0588 powder and 0.24 kg of polyamide wax were added for blending reaction, which was carried out for 4-6 h. When the viscosity of the reaction solution reached 10-30 Pa·s / 50℃, the reaction was stopped to obtain wet resin. The obtained wet resin was vacuum stirred to remove bubbles, and then transferred to 50℃ hot water for static setting and dynamic stirring for 12 h; then the molded material was placed in a 70℃ oven to dry, and finally a honeycomb porous polyurethane material was obtained.

[0049] Example 3:

[0050] 1. Formula

[0051]

[0052] 2. Preparation method

[0053] 7.97 kg of polyethylene adipate diol (number average molecular weight 4000 g / mol) and 0.44 kg of dihydroxyl-terminated polysiloxane (number average molecular weight 2000 g / mol) were added to a reactor. The reactor was evacuated to -0.1 MPa at 120°C and stirred to remove water for 2–3 h. The temperature was then lowered to 70°C, and 1.11 kg of diphenylmethane-4,4'-diisocyanate (MDI) was added. After reacting for 2–3 h, when the viscosity of the reaction solution reached 130–150 Pa·s / 50°C, the remaining 1.66 kg of diphenylmethane-4,4'-diisocyanate and 0.82 kg of chain extender ethylene glycol were added to the reactor for chain extension. The reaction temperature was controlled at 70–80°C. During chain extension, N,N-dimethylformamide solution was added to dilute the solution. The reaction was continued for 3–4 h, with a total N,N-dimethylformamide addition of 70 g / mol. When the viscosity of the reaction solution reaches 20–30 Pa·s at 50°C, 6 g of methanol is added to cap the free isocyanate groups. Finally, 17.76 kg of polyvinyl alcohol 0588 powder and 0.24 kg of polyamide wax are added for blending. The reaction is carried out for 4–6 h. When the viscosity of the reaction solution reaches 10–30 Pa·s / 50°C, the reaction is stopped to obtain a wet-process resin. The obtained wet-process resin is degassed by vacuum stirring and then transferred to 50°C hot water for static setting and dynamic stirring for 12 h. Subsequently, the molded material is dried in a 70°C oven to finally obtain a honeycomb porous polyurethane material.

[0054] Example 4:

[0055] 1. Formula

[0056]

[0057] 2. Preparation method

[0058] In a reaction vessel, 6.44 kg of polytrimethylene ether glycol (number average molecular weight 4000 g / mol), 1.38 kg of polyhexane-furandicarboxylate diol (number average molecular weight 3000 g / mol), and 0.46 kg of dihydroxyl-terminated polysiloxane (number average molecular weight 2000 g / mol) were added. The mixture was then evacuated to -0.1 MPa at 120°C and stirred to remove water for 2–3 h. The temperature was lowered to 70°C, and 1.15 kg of diphenylmethane-4,4'-diisocyanate (MDI) was added. After reacting for 2–3 h, when the viscosity of the reaction solution reached 130–150 Pa·s / 50°C, the remaining 1.73 kg of diphenylmethane-4,4'-diisocyanate and 0.84 kg of chain extender ethylene glycol were added to the reaction vessel. The chain extension reaction was carried out at a controlled temperature of 70-80℃. During the chain extension, N,N-dimethylformamide solution was added to dilute the solution, with a total addition of 70 kg of N,N-dimethylformamide. After reacting for 3-4 hours, when the viscosity of the reaction solution reached 20-30 Pa·s at 50℃, 6 g of methanol was added to end-cap the free isocyanate. Finally, 17.76 kg of polyvinyl alcohol 0588 powder and 0.24 kg of polyamide wax were added for blending. The reaction was carried out for 4-6 hours. When the viscosity of the reaction solution reached 10-30 Pa·s / 50℃, the reaction was stopped, and a wet-process resin was obtained. The obtained wet-process resin was vacuum stirred to remove bubbles, then transferred to 50℃ hot water for static setting and dynamic stirring for 12 hours. Subsequently, the molded material was dried in a 70℃ oven, finally obtaining a bio-based furan-based polyurethane honeycomb porous material.

[0059] Example 5:

[0060] 1. Formula

[0061]

[0062] 2. Preparation method

[0063] In a reaction vessel, 6.44 kg of polytrimethylene ether glycol (number average molecular weight 4000 g / mol), 1.38 kg of polyhexane-furandicarboxylate diol (number average molecular weight 3000 g / mol), and 0.46 kg of dihydroxyl-terminated polysiloxane (number average molecular weight 2000 g / mol) were added. The mixture was then evacuated to -0.1 MPa at 120°C and stirred to remove water for 2–3 h. The temperature was lowered to 70°C, and 1.15 kg of diphenylmethane-4,4'-diisocyanate (MDI) was added. After reacting for 2–3 h, when the viscosity of the reaction solution reached 130–150 Pa·s / 50°C, the remaining 1.73 kg of diphenylmethane-4,4'-diisocyanate and 0.43 kg of ethylene glycol (chain extender) were added to the reaction vessel. The chain extension reaction was carried out at a temperature of 70-80℃, with N,N-dimethylformamide solution added to dilute the solution during the chain extension process. After 3-4 hours of reaction, the reaction temperature was lowered to 40-50℃, and 0.42 kg of furanyl hydrazine, a chain extender, was added. The reaction was continued for 1-2 hours, with N,N-dimethylformamide added to dilute the viscosity during this period. The total amount of N,N-dimethylformamide added was 70 kg. When the viscosity of the reaction solution reached 20-30 Pa·s at 50℃, 6 g of methanol was added to end-cap the free isocyanate groups. The reaction was stopped when the viscosity of the reaction solution reached 10-30 Pa·s / 50℃, yielding a wet-process resin. The obtained wet-process resin was degassed under vacuum and then transferred to 50℃ hot water for static setting and dynamic stirring for 12 hours. Subsequently, the molded material was dried in a 70℃ oven to finally obtain a bio-based porous furan polyurethane material.

[0064] Results analysis:

[0065] The cross-sectional cell structure of the bio-based furan-based polyurethane honeycomb porous materials prepared in Examples 1 and 4 of this invention is as follows: Figure 1 , Figure 4 (Scanning electron microscope, magnification 150x); The cross-sectional cell structure of the honeycomb porous polyurethane material prepared in Examples 2 and 3 of this invention is as follows: Figure 2 , Figure 3 (Scanning electron microscope, magnified 150 times).

[0066] Example 5 of the present invention, as a comparative example, shows the cross-sectional cell structure of a bio-based porous furan polyurethane material as follows: Figure 5 (Scanning electron microscope, magnified 150 times).

[0067] like Figures 1 to 4As shown, it is evident that the cross-sectional pores of the porous material prepared in the embodiments of the present invention exhibit a highly interconnected, uniformly sized honeycomb-like three-dimensional network structure with clear and complete pore walls, resulting in higher overall structural density and integrity of the material. In contrast, the pores of the material prepared in the comparative example (without the addition of polyamide wax and polyvinyl alcohol) show obvious non-uniform distribution, accompanied by local stacking, pore wall collapse, and structural inhomogeneity, resulting in a loose overall structure of the material.

[0068] The microscopic, uniform pore structure lays a solid foundation for the macroscopic physicochemical properties of porous materials. The bio-based honeycomb porous polyurethane material prepared in the embodiments of this invention combines excellent properties such as extremely low density, high softness and resilience, and environmental friendliness, making it very suitable for use as a simulated flesh layer for robotic biomimetic skin. A comparison of its key physical and mechanical properties is shown in Table 1 below:

[0069]

[0070] The above data demonstrate that the uniform honeycomb structure formed in the embodiments effectively improves the porosity and pore size uniformity of the material, accommodating more air within the same volume, thus achieving significant weight reduction. The highly interconnected honeycomb structure with intact pore walls constitutes a highly efficient three-dimensional elastic network, capable of rapidly and fully recovering its original shape after compression deformation with minimal energy loss. The low-density, high-porosity uniform porous structure, combined with the flexible design of the molecular chains, enables the material to exhibit extremely low initial resistance to deformation on a macroscopic scale, with a modulus close to that of natural soft tissue.

[0071] The comparison results between Examples 1 and 4 show that adding furanoyl hydrazine as a chain extender in the formulation of bio-based porous polyurethane materials can provide multiple hydrogen bonds, significantly improving the tensile strength and tensile resistance of the materials. The comparison results between Examples 2 and 3 show that the type of macromolecular polyol in porous polyurethane materials has a significant impact on the softness of the materials. The comparison results between Examples 1 and 5 show that polyamide wax and polyvinyl alcohol, as cell regulating agents, significantly improve the uniformity of honeycomb cells, thus significantly improving the softness and resilience of porous materials.

[0072] Comprehensive Performance Analysis: The comprehensive optimization of material properties in this invention's embodiments stems fundamentally from the precise honeycomb porous structure synergistically induced by furan-modified polyester polyol and double-hydroxyl-terminated polysiloxane. The significant reduction in density, hardness, and modulus, coupled with the simultaneous improvement in resilience, demonstrates that the material macroscopically achieves a "balanced" biomimetic characteristic of "rigidity and flexibility"—possessing extreme softness and a low modulus to mimic the feel of real skin, while simultaneously providing stable and reliable mechanical support and rapid deformation recovery through a highly resilient elastic network. This synergistic change in performance is the key to its ability to serve as an ideal "tissue layer" for biomimetic robotic skin.

[0073] The blended resin material of this invention, through the molecular synergistic design of bio-based polyether polyols / bio-based furan-modified polyester polyols and double-hydroxyl-terminated polysiloxanes, alters the phase separation behavior and curing kinetics of the resin solution during wet coagulation, inducing the formation of a biomimetic honeycomb-like pore topology that differs from traditional polyurethanes. This structure, in both morphology and function, more closely resembles the natural porous network of biological soft tissue, endowing the material with excellent softness and resilience, a delicate and skin-friendly feel, and good breathability. Simultaneously, it establishes a stable and uniform mechanical support framework, providing a key material foundation for achieving highly realistic mechanical responses in biomimetic robotic skin.

Claims

1. A method for preparing a bio-based furan-based polyurethane honeycomb porous material, characterized in that... Includes the following steps: (1) Prepolymerization reaction and raw material processing: The polymer polyol and the hydroxyl-terminated polysiloxane were put into the reactor and stirred under vacuum at 120°C for 2 h; then the temperature was lowered to 70°C, and some diphenylmethane-4,4′-diisocyanate was added. The molar ratio of hydroxyl to isocyanate groups in the system was controlled to be 1:2 for reaction. The reaction was carried out until the viscosity of the reaction solution reached 130-150 Pa·s / 50°C, thus completing the first step of the prepolymerization reaction. (2) Chain extension and end-capping reaction: Add the remaining diphenylmethane-4,4′-diisocyanate and chain extender to the reaction vessel, control the equivalent ratio of isocyanate groups to hydroxyl groups in the system to be 1:1, and carry out the chain extension reaction; add N,N-dimethylformamide in batches to adjust the solution concentration, and continue the reaction until the viscosity of the system drops to 20-30 Pa·s / 50℃, and add methanol to end-cap the remaining isocyanate groups; (3) Blending reaction and resin preparation: Polyvinyl alcohol and polyamide wax are added to the reaction system and stirred and blended at 60-100 °C until the system is evenly dispersed to obtain wet resin; (4) Wet molding and post-treatment: After vacuum stirring to remove bubbles, the obtained wet resin is transferred to hot water at 40-60℃ and left to stand for 12 hours to set, and then dynamically stirred for 24 hours. The molded material was then placed in an oven to dry, ultimately yielding a bio-based furan-based polyurethane honeycomb porous material.

2. The preparation method according to claim 1, characterized in that... The composition of each raw material by mass percentage is as follows: 。 3. The preparation method according to claim 1, characterized in that: The polymer polyol is selected from one or more of polyether polyols and furanyl polyester polyols; the number average molecular weight of the polymer polyol is 2000-4000 g / mol.

4. The preparation method according to claim 3, characterized in that: The polyether polyol is either bio-based or non-bio-based; the bio-based polyether polyol is polytrimethylene ether diol; and the non-bio-based polyether polyol is polytetramethylene ether diol.

5. The preparation method according to claim 3, characterized in that: The polymeric polyols include polyether polyols and furan-based polyester polyols.

6. The preparation method according to claim 3 or 5, characterized in that: The furan-based polyester polyol is poly(adipate-furandicarboxylic acid-hexanediol ester diol).

7. The preparation method according to claim 1, characterized in that: The chain extender is one or more of ethylene glycol and bio-based furanoyl hydrazine.

8. The preparation method according to claim 1, characterized in that: The hydroxyl-terminated polysiloxane is selected from one or more of α,ω-dihydroxy polydimethylsiloxane and hydroxyl-terminated polydimethylsiloxane.

9. A bio-based furan-based polyurethane honeycomb porous material, prepared by any one of the preparation methods according to claims 1-8.

10. The application of the bio-based furan-based polyurethane honeycomb porous material of claim 9 in the preparation of biomimetic robot skin materials, medical flexible materials or flexible electronic devices.

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