Multifunctional antibacterial degradable bio-based polyurethane foam and preparation method thereof

Abstract

The invention relates to multifunctional antibacterial degradable bio-based polyurethane foam and a preparation method thereof. Polycaprolactone dihydric alcohol and castor oil-based polyhydric alcohol are compounded to form a bio-based soft segment, a three-dimensional conductive network is constructed by adding multi-walled carbon nanotube conductive enhanced master batches, and efficient and uniform heat conduction and safe heating are achieved; meanwhile, epsilon-polylysine and chitosan quaternary ammonium salt composite antibacterial agents and nano-crystalline cellulose reinforcing fillers are adopted, and a one-step foaming process is adopted for preparation. The foam has multiple functions: the foam has excellent biodegradability; the antibacterial performance is lasting, and washing resistance is achieved; relying on the three-dimensional conductive network, the foam has good conductive and heat-conducting properties, the shape memory response is fast, and the shape fixing rate and the recovery rate are gt; 90%. The bio-based polyurethane foam has the advantages that through material design and process innovation, the antibacterial function, the degradation function, the shape memory function and the electricity and heat conduction function are integrated into bio-based polyurethane foam, and the diversified requirements of modern bedding for environment friendliness, health, comfort and intelligent temperature control are met.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a multifunctional antibacterial and biodegradable bio-based polyurethane foam and its preparation method, and more particularly to a soft polyurethane foam material that integrates antibacterial, biodegradable, shape memory and electrical and thermal conductivity functions, which can be applied to products such as mattresses and wearable thermotherapy protective gear. Background Technology

[0002] With increasing health awareness and improved living standards, the health, comfort, and functionality of the sleep environment have become key concerns for consumers. Since mattresses come into direct contact with the human body, their material properties directly impact sleep quality and overall health.

[0003] However, traditional mattress materials generally suffer from the following problems: While traditional polyurethane foam offers excellent cushioning and comfort, its raw materials are primarily derived from petrochemical resources, making it difficult to degrade after disposal and causing environmental pollution. Furthermore, its open-cell structure easily absorbs human metabolic waste and moisture, creating a breeding ground for bacteria and mites, which may lead to skin diseases and allergic reactions with long-term use. Currently, most antibacterial mattresses on the market use post-treatment methods to add organic antibacterial agents, but these suffer from problems such as easy loss of antibacterial components, poor durability, and poor heat resistance. Additionally, some organic antibacterial agents may pose biosafety risks.

[0004] In recent years, shape memory materials have shown great potential in the fields of smart bedding and wearable devices. In mattress applications, shape memory materials not only deform according to ambient temperature or external stimuli, achieving personalized fit and pressure distribution, but also significantly improve the mattress's anti-creep performance. Traditional mattresses are prone to irreversible deformation under long-term loads, leading to decreased support and comfort. Shape memory polyurethane, through its reversible phase change structure and cross-linked network, can return to its initial shape under body temperature or external heat stimulation, effectively delaying or inhibiting creep, extending the mattress's lifespan, and maintaining lasting support. In wearable devices such as rehabilitation gloves and sports protective gear, shape memory materials can adaptively deform according to local body temperature, achieving a close and flexible fit to the contours of finger bones, thereby improving wearing comfort and the accuracy of functional movements, showing broad prospects in medical rehabilitation and sports protection.

[0005] However, existing shape memory polyurethane materials are mostly used in medical stents or temperature-sensitive devices, which suffer from complex manufacturing processes, high costs, and slow response speeds. This makes it difficult to meet the application requirements of large-size, low-cost, and fast-response mattresses, and also limits their adoption in wearable devices that require rapid adaptive deformation. Furthermore, traditional electric heated mattresses use resistance wire heating, which suffers from uneven heating, localized overheating, electromagnetic radiation, and safety hazards. Meanwhile, the filling material, a thermally conductive material, often suffers from uneven distribution of conductive fillers, leading to damage to the cell structure and affecting mechanical properties and user comfort.

[0006] Driven by the concept of sustainable development, bio-based polymer materials have become a research hotspot. Renewable resources such as polycaprolactone and castor oil-based polyols show promising application prospects, but pure bio-based polyurethane foams often suffer from insufficient mechanical strength and limited functionality. Although some studies have attempted to improve performance by adding reinforcing fillers such as nanocellulose and carbon nanotubes, achieving efficient synergy among multiple functions such as antibacterial properties, degradation resistance, shape memory, and electrical and thermal conductivity remains a key technological bottleneck restricting its application in high-end smart bedding and wearable health products.

[0007] Therefore, developing a multifunctional polyurethane foam material that combines long-lasting antibacterial properties, biodegradability, rapid shape memory response, and high-efficiency electrical and thermal conductivity to achieve a balance between green environmental protection and intelligent comfort has become an important issue that urgently needs to be addressed in the field of mattress and wearable health product materials technology. Summary of the Invention

[0008] The purpose of this invention is to provide a multifunctional antibacterial and biodegradable bio-based polyurethane foam and its preparation method. Through multi-element synergistic enhancement and multi-level structural regulation, it achieves efficient integration of antibacterial, biodegradable, shape memory and electrical and thermal conductivity functions, solving the problems of traditional mattress materials such as single function, poor environmental protection, insufficient intelligent response capability and uneven heating.

[0009] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: the raw materials comprise the following components by mass: Component A: Bio-based polyols: 45.0-82.0 parts, wherein the bio-based polyols include polycaprolactone diol and castor oil-based polyols, wherein the number average molecular weight of polycaprolactone diol is 1000-3000 Da; Conductivity-enhancing masterbatch: 5.0-8.0 parts, wherein the conductivity-enhancing masterbatch is prepared by pre-dispersion-melt blending of multi-walled carbon nanotubes and polycaprolactone diol; Reinforcing filler: 0.8-2.5 parts, wherein the reinforcing filler is one or a combination of two of carboxylated nanocellulose dry powder and organic modified montmorillonite; the carboxyl groups on the surface of carboxylated nanocellulose can react with isocyanate to improve the cell wall strength and shape memory recovery rate; Antibacterial agent: 2.0-4.0 parts, wherein the antibacterial agent is a combination of ε-polylysine and chitosan quaternary ammonium salt or quaternized chitosan; Chain extender: 0-2.0 parts, the chain extender is glycerol or 1,4-butanediol; Catalyst: 0.3-0.4 parts, wherein the catalyst is stannous octoate or a composite system of stannous octoate and delayed-type dibutyltin dilaurate; Foam stabilizer: 1.0 part, wherein the foam stabilizer is a polyether-modified organosilicon surfactant; Component B: Poly(diphenylmethane) diisocyanate: 35.2–45.8 parts, NCO content 31.5%, wherein the molar ratio R of NCO to total OH is 1.10–1.25; Foaming agent: 1.2 to 1.8 parts of deionized water.

[0010] As a preferred embodiment of the present invention, in the bio-based polyol, the mass ratio of polycaprolactone diol to castor oil-based polyol is (40-48):(12-18), and the two are compounded to form a biodegradable soft segment phase, which gives the foam good resilience and degradation performance.

[0011] As a preferred embodiment of the present invention, the conductive reinforcing masterbatch comprises the following components by weight: 1.5 to 2.4 parts multi-walled carbon nanotubes, 5 to 8 parts ethanol, 0.3 to 0.5 parts Tween-80, and 3.2 to 5.0 parts polycaprolactone diol. The method for preparing the conductive reinforcing masterbatch is as follows: multi-walled carbon nanotubes and Tween-80 are pre-dispersed in ethanol, and then mixed with molten polycaprolactone diol at 50-60 °C by a high-speed shear emulsifier at a speed of 8000-12000 rpm for 30-40 minutes. Subsequently, the ethanol is removed under vacuum, and the masterbatch is obtained after cooling and crushing. This masterbatch can effectively avoid the aggregation of multi-walled carbon nanotubes during the foaming process and construct a highly efficient three-dimensional conductive network.

[0012] The multi-walled carbon nanotubes have a diameter of 10–20 nm and a length of 5–15 μm.

[0013] As a preferred embodiment of the present invention, in the antibacterial agent, the mass ratio of ε-polylysine to chitosan quaternary ammonium salt or quaternized chitosan is (1.5-2.5):(1.0-1.5). The two are anchored to the cell wall through electrostatic adsorption and hydrogen bonding to achieve a broad-spectrum and long-lasting antibacterial effect.

[0014] A method for preparing a multifunctional antibacterial and biodegradable bio-based polyurethane foam, characterized by comprising the following steps: (1) Preparation of premix: Add bio-based polyol to the reaction vessel and stir at 500 rpm under nitrogen protection at 50-70 ℃ until a homogeneous liquid is obtained; then add conductive reinforcing masterbatch, reinforcing filler and antibacterial agent in sequence, increase the stirring speed to 4000-6000 rpm, and continue high-speed shear dispersion for 20-30 minutes to obtain a uniformly dispersed mixture; (2) Catalysis and emulsification: Cool the mixture obtained in step (1) to 30-40 °C, and add chain extender, catalyst and foam stabilizer in sequence. After each additive is added, stir at 800-1000 rpm for 3-5 minutes to make it evenly mixed; (3) Foaming and curing: Add deionized water to the premix obtained in step (2) and stir at 1500-2000 rpm for 30-40 seconds; then add all of component B at once and immediately stir at 2500-3500 rpm for 10-15 seconds. When the system turns milky white and begins to expand, quickly pour it into a mold preheated to 20-50 ℃ for free foaming and curing. (4) Post-curing treatment: Demold the cured foam and place it in a forced-air drying oven at 70-90 ℃ for 3-5 hours. Depending on the application requirements, selectively perform hot pressing and light treatment or cold storage for shaping to finally obtain the multifunctional foam.

[0015] As a preferred embodiment of the present invention, a three-stage variable speed shearing process is adopted in step (1): shearing at 4000 rpm for 5 minutes → shearing at 6000 rpm for 15 minutes → shearing at 4000 rpm for 5 minutes, so as to achieve gradient dispersion and interface optimization of filler in polyol matrix; in step (3), vertical vibration with a frequency of 20-30 Hz and an amplitude of 0.3-0.5 mm is applied in the mold to assist in degassing, and the vibration lasts for 20-30 seconds to improve the uniformity of cell structure.

[0016] As a preferred embodiment of the present invention, the polycaprolactone diol has a number average molecular weight of 1000 Da and also contains 2.0 parts of nano-silver-chitosan composite microspheres. When preparing polyurethane foam, after post-curing treatment, it is cooled and shaped in a refrigerator at 4 ℃ for 2 hours to obtain a low-temperature responsive flexible antibacterial conductive foam. This polyurethane foam is used to prepare wearable thermotherapy protective gear.

[0017] As a preferred embodiment of the present invention, the polycaprolactone diol has a number average molecular weight of 3000 Da, and 10.0 parts of soybean oil-based polyol are added. Graphene nanosheets are added to the conductive reinforcing masterbatch, and 2.0 parts of 1,4-butanediol are added. 1.0 part of organically modified montmorillonite is added. The molar ratio R of NCO to total OH of the polymeric diphenylmethane diisocyanate is 1.25. During the preparation of the polyurethane foam, the post-curing treatment conditions are 90°C for 5 hours and hot pressing and calendering treatment is performed to obtain a high-strength, fast-response, antibacterial, and thermally conductive foam. This polyurethane foam is used to prepare a high-power electric heating mattress.

[0018] The advantages of this invention are: it uses polycaprolactone and castor oil-based polyols to construct fully bio-based soft segments, and the foam can achieve a degradation rate of over 90% under composting conditions in 6 months, significantly reducing the environmental burden and making it green and environmentally friendly; ε-polylysine and chitosan quaternary ammonium salt are fixed inside the pores through a combination of chemical bonding and physical adsorption. After 50 washes, the antibacterial rate remains above 70%, and the inhibition rate against Escherichia coli and Staphylococcus aureus is greater than 80%, achieving long-lasting and highly effective antibacterial properties. By optimizing the crosslinking density and soft segment crystallization behavior, the shape fixation rate (R0) of foam under thermal stimulation was improved. f The shape recovery rate (R) reached over 92%, and the shape recovery rate (R) was over 92%. r With a response time of less than 60 seconds, the mattress achieves a high accuracy of over 90%, enhancing rapid shape memory response and long-lasting support and fit. This feature not only allows for adaptive deformation based on the human body shape to achieve personalized support, but also significantly improves the mattress's anti-creep performance. Furthermore, it enables a close and flexible fit to the contours of finger bones in wearable devices. Conductivity-enhancing masterbatch technology enables multi-walled carbon nanotubes (MWCNTs) to form a three-dimensional conductive network in foam, reducing the volume resistivity to 10. 2 ~10 3 With a thermal conductivity of 0.11–0.22 W / (m·K), the three-dimensional network ensures uniform and efficient heat transfer. When used with a low-voltage safe power supply, it can achieve uniform and rapid heating, avoiding the risks of local overheating and electromagnetic radiation, thus giving the polyurethane foam excellent and uniform electrical and thermal conductivity. The synergistic reinforcing effect of carboxylated nanocellulose and organically modified montmorillonite increases the compressive strength of foam by 30-50%, maintains a resilience of over 55%, and retains good flexibility to meet the requirements of long-term use, thus synergistically improving the mechanical properties of polyurethane foam. This invention employs a one-step foaming process, which can achieve multi-functional integration through formula and process parameter control. The process is simple and controllable, suitable for large-scale industrial production, and has obvious cost advantages. This invention, through material design and process innovation, successfully integrates antibacterial, degradable, shape memory, and electrical and thermal conductivity functions into bio-based polyurethane foam, providing a high-performance, green and environmentally friendly new material solution for the field of smart health bedding. It can be applied to smart mattresses, wearable thermotherapy protective gear, and other fields, meeting the diverse needs of modern bedding for green environmental protection, health and comfort, and intelligent temperature control. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the antibacterial efficacy of the multifunctional antibacterial and biodegradable bio-based polyurethane foam prepared according to the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments will enable those skilled in the art to more fully understand this invention, but do not limit the invention to the scope of the described embodiments.

[0021] This specific embodiment adopts the following technical solution: a multifunctional antibacterial and biodegradable bio-based polyurethane foam, the raw materials of which include the following components by mass: Component A: Bio-based polyols: 45.0–82.0 parts, including polycaprolactone diol (PCL) and castor oil-based polyols, wherein the number average molecular weight of polycaprolactone diol is 1000–3000 Da; the mass ratio of polycaprolactone diol to castor oil-based polyol is (40–48):(12–18), and the two are compounded to form a biodegradable soft segment phase, giving the foam good resilience and degradation properties.

[0022] Conductive reinforcement masterbatch: 5.0-8.0 parts. The conductive reinforcement masterbatch is prepared by pre-dispersion-melt blending of multi-walled carbon nanotubes (MWCNTs) and polycaprolactone diol. The conductive reinforcement masterbatch includes the following components by mass: 1.5-2.4 parts multi-walled carbon nanotubes, 5-8 parts ethanol, 0.3-0.5 parts Tween-80, and 3.2-5.0 parts polycaprolactone diol.

[0023] The conductive reinforcing masterbatch is prepared as follows: multi-walled carbon nanotubes and Tween-80 are pre-dispersed in ethanol, and then sheared and blended with molten polycaprolactone diol at 50–60 °C using a high-speed shear emulsifier at a speed of 8000–12000 rpm for 30–40 minutes. Subsequently, the ethanol is removed under vacuum, and the mixture is cooled and crushed to obtain the conductive reinforcing masterbatch. This masterbatch effectively avoids the aggregation of multi-walled carbon nanotubes during the foaming process, constructing a highly efficient three-dimensional conductive network. The multi-walled carbon nanotubes have a diameter of 10–20 nm and a length of 5–15 μm.

[0024] Reinforcing filler: 0.8 to 2.5 parts, the reinforcing filler is one or a combination of two of carboxylated nanocellulose dry powder and organic modified montmorillonite; the carboxyl groups on the surface of carboxylated nanocellulose can react with isocyanate to improve the strength of the cell wall and the shape memory recovery rate.

[0025] Antibacterial agent: 2.0-4.0 parts, the antibacterial agent is a combination of ε-polylysine and chitosan quaternary ammonium salt (HACC) or quaternized chitosan; the mass ratio of ε-polylysine to chitosan quaternary ammonium salt or quaternized chitosan is (1.5-2.5):(1.0-1.5), the two are anchored to the cell wall through electrostatic adsorption and hydrogen bonding to achieve a broad-spectrum and long-lasting antibacterial effect.

[0026] Chain extender: 0-2.0 parts, the chain extender is glycerol or 1,4-butanediol; Catalyst: 0.3-0.4 parts, the catalyst is stannous octoate or a composite system of stannous octoate and delayed dibutyltin dilaurate (DBTDL); Foam stabilizer: 1.0 part, the foam stabilizer is a polyether-modified organosilicon surfactant; Component B: Poly(diphenylmethane) diisocyanate (PMDI): 35.2–45.8 parts, NCO content 31.5%, wherein the molar ratio R of NCO to total OH is 1.10–1.25; Foaming agent: 1.2 to 1.8 parts of deionized water.

[0027] A method for preparing a multifunctional antibacterial and biodegradable bio-based polyurethane foam includes the following steps: (1) Preparation of premix: Bio-based polyol is added to a reaction vessel and stirred at 500 rpm under nitrogen protection at 50-70 °C until a homogeneous liquid is obtained; then conductive reinforcing masterbatch, reinforcing filler and antibacterial agent are added in sequence, and the stirring speed is increased to 4000-6000 rpm, and high-speed shear dispersion is carried out for 20-30 minutes to obtain a uniformly dispersed mixture; a three-stage variable speed shear process is adopted: shear at 4000 rpm for 5 minutes → shear at 6000 rpm for 15 minutes → shear at 4000 rpm for 5 minutes to achieve gradient dispersion and interface optimization of filler in polyol matrix.

[0028] (2) Catalysis and emulsification: Cool the mixture obtained in step (1) to 30-40 °C, and add chain extender, catalyst and foam stabilizer in sequence. After each additive is added, stir at 800-1000 rpm for 3-5 minutes to make it evenly mixed.

[0029] (3) Foaming and curing: Add deionized water to the premix obtained in step (2) and stir at 1500-2000 rpm for 30-40 seconds; then add all of component B at once and immediately stir at 2500-3500 rpm for 10-15 seconds. When the system turns milky white and begins to expand, quickly pour it into a mold preheated to 20-50 ℃ for free foaming and curing. Apply vertical vibration with a frequency of 20-30 Hz and an amplitude of 0.3-0.5 mm to the mold to assist in defoaming. The vibration lasts for 20-30 seconds to improve the uniformity of the cell structure.

[0030] (4) Post-curing treatment: Demold the cured foam and place it in a forced-air drying oven at 70-90 ℃ for 3-5 hours. Depending on the application requirements, selectively perform hot pressing and light treatment or cold storage for shaping to finally obtain multifunctional foam.

[0031] The polycaprolactone diol has a number average molecular weight of 1000 Da and also contains 2.0 parts of nano-silver-chitosan composite microspheres. During the preparation of polyurethane foam, after post-curing treatment, it is cooled and shaped in a refrigerator at 4 ℃ for 2 hours to obtain a low-temperature responsive flexible antibacterial conductive foam. This polyurethane foam is used to prepare wearable thermotherapy protective gear.

[0032] The polycaprolactone diol has a number average molecular weight of 3000 Da, and 10.0 parts of soybean oil-based polyol are added. Graphene nanosheets are added to the conductive reinforcing masterbatch, and 2.0 parts of 1,4-butanediol are added. 1.0 part of organically modified montmorillonite is added. The molar ratio R of NCO to total OH of the polymeric diphenylmethane diisocyanate is 1.25. During the preparation of polyurethane foam, the post-curing treatment is 90℃ for 5 hours, followed by hot pressing and calendering to obtain a high-strength, fast-response, antibacterial, and thermally conductive foam. This polyurethane foam is used to prepare a high-power electric heating mattress.

[0033] Unless otherwise specified, all raw materials used in this invention are commercially available in the field.

[0034] Example 1: Multifunctional antibacterial and biodegradable bio-based polyurethane foam, the raw materials include by weight: Component A: Polycaprolactone diol (PCL-2000, number average molecular weight 2000 Da, hydroxyl value 56 mg KOH / g): 45.0 parts; Castor oil-based polyol (hydroxyl value 160 mg KOH / g): 15.0 parts; Conductivity-enhancing masterbatch: 5.0 parts; Carboxylated nanocellulose dry powder: 1.0 part; ε-Polylysine: 2.0 parts; Chitosan Quaternary Ammonium Salt (HACC): 1.0 part; Glycerin: 1.5 parts; Stannous octoate: 0.3 parts; Polyether-modified silicone foam stabilizer: 1.0 part; Component B: Poly(diphenylmethane) diisocyanate (PMDI, NCO content 31.5%): 38.5 parts (based on a molar ratio of NCO to total OH of R value of 1.15); Foaming agent: 1.5 parts deionized water.

[0035] The conductive enhancement masterbatch was prepared by the following method: 1.5 parts of multi-walled carbon nanotubes (MWCNTs, diameter 10-20 nm, length 5-15 μm) and 0.3 parts of Tween-80 were pre-dispersed in 5 parts of ethanol, and then mixed with 3.2 parts of molten polycaprolactone diol (PCL-2000) at 50°C by shearing at 10,000 rpm for 30 minutes using a high-speed shear emulsifier. The ethanol was then removed under vacuum, and the mixture was cooled and crushed to obtain the final product.

[0036] The multifunctional foam of Example 1 was prepared by the following method: Premix preparation: Polycaprolactone diol and castor oil-based polyol were added to a plastic beaker and stirred at 500 rpm at 60°C under nitrogen protection until a homogeneous liquid was obtained. Then, conductive reinforcing masterbatch, carboxylated nanocellulose powder, ε-polylysine and chitosan quaternary ammonium salt were added in sequence. The stirring speed was increased to 5000 rpm and high-speed shear dispersion was carried out for 20 minutes to obtain a homogeneous mixture.

[0037] (2) Catalysis and emulsification: Cool the mixture obtained in step (1) to 35°C, and add glycerol, stannous octoate and polyether modified silicone foam stabilizer in sequence. After each additive is added, stir at 800 rpm for 3 minutes to make it evenly mixed.

[0038] (3) Foaming and curing: Add 1.5 parts of deionized water to the premix obtained in step (2) and stir at 1500 rpm for 30 seconds. Then add all of component B (PMDI) at once and immediately stir at 3000 rpm for 10 seconds. When the system turns milky white and begins to expand, quickly pour it into a room temperature mold (15 cm × 15 cm × 5 cm), allow it to foam freely, and cure at room temperature for 60 minutes.

[0039] (4) Post-curing: Demold the cured foam and place it in an 80°C drying oven for 4 hours. Then cool it naturally to room temperature to obtain a multifunctional antibacterial biodegradable polyurethane foam.

[0040] Example 2: The difference between Example 2 and Example 1 is that the raw material formula and process parameters are adjusted to prepare a low-temperature responsive flexible antibacterial conductive foam, suitable for wearable thermotherapy protective gear. Specifically: Formula adjustments: The following adjustments were made: Polycaprolactone diol was replaced with PCL-1000 (number average molecular weight 1000 Da, hydroxyl value 112 mg KOH / g): 48.0 parts; castor oil-based polyol was adjusted to: 18.0 parts; the amount of conductive reinforcing masterbatch was adjusted to: 6.0 parts (of which the MWCNTs content was increased to 1.8 parts); carboxylated nanocellulose dry powder was adjusted to: 0.8 parts; ε-polylysine was adjusted to: 1.5 parts; new nano-silver-chitosan composite microspheres (Ag content 0.1 wt%) were added: 2.0 parts; glycerol was adjusted to: 1.2 parts; PMDI was adjusted to: 35.2 parts (based on NCO / OH molar ratio R value = 1.10); deionized water was adjusted to: 1.8 parts.

[0041] Preparation method adjustment: The premixing temperature was adjusted to 50 ℃, the high-speed shearing speed was adjusted to 4000 rpm, and the shearing time was 25 min; the mold was preheated to 35 ℃; the post-curing conditions were 70 ℃ for 3 h, followed by cooling and shaping in a 4 ℃ refrigerator for 2 h.

[0042] The remaining steps and processes are the same as in Example 1, and the low-temperature responsive foam of this example is obtained.

[0043] Example 3: The difference between Example 3 and Example 1 is that, through multi-component synergistic reinforcement and high cross-linking density design, a high-strength, fast-response, antibacterial, and thermally conductive foam is prepared, suitable for high-power electric heating mattresses. Specifically: Formula adjustments: Polycaprolactone diol was replaced with PCL-3000 (number average molecular weight 3000 Da, hydroxyl value 37 mg KOH / g): 40.0 parts; castor oil-based polyol was adjusted to: 12.0 parts; soybean oil-based polyol (hydroxyl value 240 mg KOH / g) was added: 10.0 parts; the amount of conductive reinforcing masterbatch was adjusted to: 8.0 parts (of which MWCNTs were increased to 2.4 parts and 0.3 parts of graphene nanosheets were added), with MWCNTs as the main component and graphene nanosheets as the auxiliary component, filling the gaps in the MWCNT network and utilizing its two-dimensional large specific surface area characteristics to enhance the network connection density; carboxylated nanocellulose dry powder was adjusted to: 1.5 parts; organic modified montmorillonite (OMMT, d 001 ≥3.0 nm): 1.0 part; ε-polylysine adjusted to: 2.5 parts; chitosan quaternary ammonium salt replaced with quaternized chitosan (substitution degree 90%): 1.5 parts; glycerol replaced with 1,4-butanediol (BDO): 2.0 parts; PMDI amount adjusted to: 45.8 parts (based on R value = 1.25); deionized water adjusted to: 1.2 parts.

[0044] Preparation method adjustment: The premixing temperature was increased to 70 ℃, and the high-speed shearing was carried out using a three-stage variable speed shearing: 4000 rpm (5 min) → 6000 rpm (15 min) → 4000 rpm (5 min); the catalyst used was a dual system (0.3 parts stannous octoate + 0.1 parts delayed DBTDL); after adding PMDI, the stirring speed was varied: 3500 rpm (5 seconds) → 2500 rpm (10 seconds); the mold temperature was 50 ℃, and vertical vibration (30 Hz, 0.5 mm) was applied to assist in degassing for 30 seconds; the post-curing conditions were 90 ℃ for 5 h, followed by hot pressing and polishing treatment (80 ℃, linear pressure 3 N / mm).

[0045] The remaining steps and processes are the same as in Example 1, and the high-strength foam of Example 3 is obtained.

[0046] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the conductive enhancement masterbatch does not contain MWCNTs, but is replaced by an equal amount of pure PCL. All other process steps are the same as in Example 1.

[0047] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that carboxylated nanocellulose was not added. All other steps and processes were performed in accordance with Example 1.

[0048] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that polycaprolactone diol was replaced in equal amounts with ordinary polyether polyol (hydroxyl value 56 mg KOH / g). The remaining steps and processes are the same as in Example 1.

[0049] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the NCO / OH molar ratio R is reduced to 1.05. All other process steps are the same as in Example 1.

[0050] Comparative Example 5 The difference between Comparative Example 5 and Example 2 is that the 4°C cooling and shaping process is omitted, and the product is directly cooled to room temperature. The remaining steps and processes are the same as in Example 2.

[0051] Comparative Example 6 The difference between Comparative Example 6 and Example 3 is that no vibration-assisted process is applied. The remaining steps and processes are the same as in Example 3.

[0052] The polyurethane foams prepared in Examples 1-3 and Comparative Examples 1-6 were tested for antibacterial rate, degradation rate, volume resistivity, thermal conductivity, and shape memory function.

[0053] Performance testing methods Antibacterial properties: The test was conducted according to the national standard GB / T 31402-2020, "Test Method for Antibacterial Properties of Plastic Surfaces". Specifically, foam samples were cut into 50 mm × 50 mm pieces and inoculated with *Escherichia coli* (ATCC 25922) and *Staphylococcus aureus* (ATCC 6538) respectively, with an inoculation concentration of 1.0 × 10⁻⁶. 5 CFU / mL. Inoculated samples were incubated at (37 ± 1) °C and relative humidity ≥ 90% for 24 h. After incubation, viable bacteria on the sample surface were washed away with neutralization solution, and colony counts were performed. The antibacterial rate was calculated using the formula: Antibacterial rate = (C0 - C) / C0 × 100%, where C0 is the average viable count of the blank control group, and C is the average viable count of the experimental group. Three parallel samples were tested for each type of sample, and the average result was taken.

[0054] Degradation performance: The biodegradability potential of the foam was evaluated using an alkali-accelerated degradation experiment. Foam samples were cut into 10 mm × 10 mm × 5 mm pieces and vacuum-dried at 60 °C to constant weight; the initial dry weight (W0) was recorded. Subsequently, the samples were completely immersed in a 10 wt% sodium hydroxide (NaOH) aqueous solution, sealed, and placed at a constant temperature of (80 ± 2) °C for 50 h. After removal, the samples were repeatedly rinsed with deionized water until neutral, and then vacuum-dried again at 60 °C to constant weight; the final dry weight (W0) was recorded. t The degradation rate is calculated using the formula: Degradation rate = (W0 - W) t ) / W0 × 100%. Five parallel samples were tested for each sample, and the average value of the results was taken.

[0055] Volume resistivity: A four-probe method was used for testing. The foam sample was processed into a regular shape of 30 mm × 30 mm × 10 mm, and gold electrodes were sputtered onto its upper and lower surfaces to reduce contact resistance. Before testing, the sample needed to equilibrate for 24 hours at 23 °C and 50% relative humidity. A four-probe resistivity meter was used, with a probe spacing of 1 mm and a pressure of 0.2 N. Five points were randomly selected along the sample thickness direction for measurement. The volume resistivity ρv was calculated using the formula: ρv = R × A / t, where R is the measured resistance value, A is the electrode contact area, and t is the sample thickness. The result was the geometric mean of the five measurement points, retained to two significant figures.

[0056] Thermal conductivity: The transient plane heat source method was used for testing. Two foam samples measuring 30 mm × 30 mm × 10 mm were cut, and the Hot Disk sensor was sandwiched between the two samples. The test was conducted in a constant temperature and humidity chamber at 23 °C and 50% relative humidity. The test parameters were set as follows: power 20 mW, test time 10 s. Each sample was tested five times, and the average value was taken after removing outliers to obtain the thermal conductivity λ, expressed in W / (m·K). The result was retained to three significant figures.

[0057] Shape memory function: The tests were conducted using a dynamic thermomechanical analyzer. The foam samples were processed into strips measuring 40 mm × 10 mm × 5 mm and conditioned at 23 °C and 50% relative humidity for 24 hours. The tensile test was performed, and the specific steps are as follows: ① Deformation: At 45 °C, the sample was stretched to 50% strain (εm) at a stress rate of 0.02 MPa / min, held for 5 min, and the length L1 at this time was recorded.

[0058] ② Fixation: Cool the system to 5 °C at a rate of 2 °C / min, unload the stress at this temperature, hold for 10 min, and record the length L2 of the sample after fixation.

[0059] ③ Response: The system was heated to 45 °C at a rate of 5 °C / min and held at this temperature for 10 min. The final length L3 of the sample was recorded.

[0060] Shape fixation rate (R) f ) and shape recovery rate (R r Calculate using the following formula: R f = (L2 - L0) / (L1 - L0) × 100% R r = (L1 - L3) / (L1 - L0) × 100% Where L0 is the initial length of the sample. The test is performed for 3 complete deformation-fixation-recovery cycles, and the data from the 3rd cycle is used for calculation. Five parallel specimens are tested for each type of sample, and the results are averaged.

[0061] The test results are shown in the table below.

[0062] sample Antibacterial rate (%) Escherichia coli; Staphylococcus aureus Degradation rate (%) (80℃, 10 wt% NaOH aqueous solution for 50 hours) Volume resistivity (Ω·cm) Thermal conductivity W / (m·K) Shape memory function (%) R f = Shape fixation rate; R r =Shape recovery rate Example 192.3; 90.5525.2×10 3 0.1195.2; 93.0 Example 291.0; 89.8614.2×10 3 0.1892.5; 90.6 Example 395.8; 93.0481.1×10 2 0.2296.1; 94.3 Comparative Example 185.7; 84.3581.0×10 10 0.0189.2; 85.0 Comparative Example 288.5; 87.2475.0 × 10 4 0.0788.0; 85.1 Comparative Example 385.6; 83.73 84.8 × 10 4 0.0850.6; 45.9 Comparative Example 486.8; 84.0555.1×10 5 0.0585.4; 80.5 Comparative Example 584.0; 82.9603.6×10 3 0.1083.9; 82.4 Comparative Example 688.3; 86.4456.7×10 3 0.1292.8; 90.2 Based on the above data and appendix Figure 1 It is evident that the fully bio-based soft segments constructed using polycaprolactone and castor oil-based polyols exhibit high degradation rates, significantly reducing environmental burden; the antibacterial rates against Escherichia coli and Staphylococcus aureus are both greater than 80%, demonstrating high antibacterial efficiency; and the foam shape fixation rate (R... f The shape recovery rate (R) reached over 92%, and the shape recovery rate (R) was over 92%. r With a resistivity exceeding 90%, it possesses rapid shape memory response and long-lasting support and fit, enabling a tight and flexible fit to the contours of finger bones in wearable devices; the conductive reinforced masterbatch technology allows multi-walled carbon nanotubes (MWCNTs) to form a three-dimensional conductive network within the foam, reducing the volume resistivity to 10. 2 ~10 3 With a thermal conductivity of 0.11–0.22 W / (m·K), it possesses excellent and uniform electrical and thermal conductivity. The three-dimensional network ensures the uniformity and efficiency of heat transfer. When used with a low-voltage safe power supply, it can achieve uniform and rapid heating, avoiding the risks of local overheating and electromagnetic radiation. It successfully integrates antibacterial, degradable, shape memory, and electrical and thermal conductivity functions into bio-based polyurethane foam.

[0063] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A multifunctional antibacterial and biodegradable bio-based polyurethane foam, characterized in that: The raw materials include the following components by weight: Component A: Bio-based polyols: 45.0-82.0 parts, wherein the bio-based polyols include polycaprolactone diol and castor oil-based polyols, wherein the number average molecular weight of polycaprolactone diol is 1000-3000 Da; Conductivity-enhancing masterbatch: 5.0-8.0 parts, wherein the conductivity-enhancing masterbatch is prepared by pre-dispersion-melt blending of multi-walled carbon nanotubes and polycaprolactone diol; Reinforcing filler: 0.8-2.5 parts, wherein the reinforcing filler is one or a combination of two of carboxylated nanocellulose dry powder and organic modified montmorillonite; Antibacterial agent: 2.0-4.0 parts, wherein the antibacterial agent is a combination of ε-polylysine and chitosan quaternary ammonium salt or quaternized chitosan; Chain extender: 0-2.0 parts, the chain extender is glycerol or 1,4-butanediol; Catalyst: 0.3-0.4 parts, wherein the catalyst is stannous octoate or a composite system of stannous octoate and delayed-type dibutyltin dilaurate; Foam stabilizer: 1.0 part, wherein the foam stabilizer is a polyether-modified organosilicon surfactant; Component B: Poly(diphenylmethane) diisocyanate: 35.2–45.8 parts, NCO content 31.5%, wherein the molar ratio R of NCO to total OH is 1.10–1.25; Foaming agent: 1.2 to 1.8 parts of deionized water.

2. The multifunctional antibacterial and biodegradable bio-based polyurethane foam according to claim 1, characterized in that: In the bio-based polyol, the mass ratio of polycaprolactone diol to castor oil-based polyol is (40-48):(12-18), and the two are compounded to form a biodegradable soft segment phase.

3. The multifunctional antibacterial and biodegradable bio-based polyurethane foam according to claim 1, characterized in that: The conductive reinforcing masterbatch comprises the following components by weight: 1.5–2.4 parts multi-walled carbon nanotubes, 5–8 parts ethanol, 0.3–0.5 parts Tween-80, and 3.2–5.0 parts polycaprolactone diol. The method for preparing the conductive reinforcing masterbatch is as follows: multi-walled carbon nanotubes and Tween-80 are pre-dispersed in ethanol, and then mixed with molten polycaprolactone diol at 50-60 °C by a high-speed shear emulsifier at a speed of 8000-12000 rpm for 30-40 minutes. After vacuum removal of ethanol, the masterbatch is obtained by cooling and crushing. The multi-walled carbon nanotubes have a diameter of 10–20 nm and a length of 5–15 μm.

4. The multifunctional antibacterial and biodegradable bio-based polyurethane foam according to claim 1, characterized in that: In the antibacterial agent, the mass ratio of ε-polylysine to chitosan quaternary ammonium salt or quaternized chitosan is (1.5-2.5):(1.0-1.5), and the two are anchored to the cell wall through electrostatic adsorption and hydrogen bonding.

5. A method for preparing a multifunctional antibacterial and biodegradable bio-based polyurethane foam according to any one of claims 1-4, characterized in that: Includes the following steps: (1) Preparation of premix: Add bio-based polyol to the reaction vessel and stir at 500 rpm under nitrogen protection at 50-70 ℃ until a homogeneous liquid is obtained; then add conductive reinforcing masterbatch, reinforcing filler and antibacterial agent in sequence, increase the stirring speed to 4000-6000 rpm, and continue high-speed shear dispersion for 20-30 minutes to obtain a uniformly dispersed mixture; (2) Catalysis and emulsification: Cool the mixture obtained in step (1) to 30-40 °C, and add chain extender, catalyst and foam stabilizer in sequence. After each additive is added, stir at 800-1000 rpm for 3-5 minutes to make it evenly mixed; (3) Foaming and curing: Add deionized water to the premix obtained in step (2) and stir at 1500-2000 rpm for 30-40 seconds; then add all of component B at once and immediately stir at 2500-3500 rpm for 10-15 seconds. When the system turns milky white and begins to expand, quickly pour it into a mold preheated to 20-50 ℃ for free foaming and curing. (4) Post-curing treatment: Demold the cured foam and place it in a forced-air drying oven at 70-90 ℃ for 3-5 hours. Depending on the application requirements, selectively perform hot pressing and light treatment or cold storage for shaping to finally obtain the multifunctional foam.

6. The method for preparing a multifunctional antibacterial and biodegradable bio-based polyurethane foam according to claim 5, characterized in that: In step (1), a three-stage variable-speed shearing process is adopted: shearing at 4000 rpm for 5 minutes → shearing at 6000 rpm for 15 minutes → shearing at 4000 rpm for 5 minutes, so as to achieve gradient dispersion and interface optimization of filler in polyol matrix; in step (3), vertical vibration with a frequency of 20-30 Hz and an amplitude of 0.3-0.5 mm is applied in the mold to assist in degassing, and the vibration lasts for 20-30 seconds to improve the uniformity of cell structure.

7. The multifunctional antibacterial and biodegradable bio-based polyurethane foam according to claim 1, characterized in that: The polycaprolactone diol has a number average molecular weight of 1000 Da, and 2.0 parts of nano-silver-chitosan composite microspheres are added. When preparing polyurethane foam, after post-curing treatment, it is cooled and shaped in a refrigerator at 4 ℃ for 2 hours to obtain low-temperature responsive flexible antibacterial conductive foam.

8. An application of a multifunctional antibacterial and biodegradable bio-based polyurethane foam, characterized in that: The application includes using the polyurethane foam as described in claim 7 to prepare wearable thermotherapy protective gear.

9. The multifunctional antibacterial and biodegradable bio-based polyurethane foam according to claim 1, characterized in that: The polycaprolactone diol has a number average molecular weight of 3000 Da, and 10.0 parts of soybean oil-based polyol are added. Graphene nanosheets are added to the conductive reinforcing masterbatch, and 2.0 parts of 1,4-butanediol are added. 1.0 part of organically modified montmorillonite is added. The molar ratio R of NCO to total OH of the polymeric diphenylmethane diisocyanate is 1.

25. During the preparation of polyurethane foam, the post-curing treatment conditions are 90℃ for 5 hours and hot pressing and calendering treatment to obtain high-strength fast-response antibacterial thermally conductive foam.

10. An application of a multifunctional antibacterial and biodegradable bio-based polyurethane foam, characterized in that: The application includes using the polyurethane foam as described in claim 9 to prepare a high-power electric heating mattress.

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