A polymer self-repairing tpu material, method and application

Abstract

The application discloses a kind of polymer self-repairing TPU materials, methods and applications.It includes the polyester TPU matrix of mass percentage 80-85%, 5-8%, 2-3%, 1.5-3%, 0.5-1%, 0.3-0.5%, nano-silica, fluorinated modifier, siloxane microcapsule, antioxidant, lubricant;Siloxane microcapsule adopts the polyurethane-polyurea double-layer microcapsule of coated siloxane repair agent;Preparation includes premixing stage in high-speed mixer, melt co-extrusion is carried out in twin-screw extruder and subsection temperature control and late melt co-extrusion stage of microcapsule addition, granulation forming stage after underwater cutting and drying.The application scheme is through nano SiO2 directional reinforcement and interface optimization of microcapsule, realizes strength and repair;Through intelligent trigger mechanism, the accuracy of repair is realized, and the double-layer wall material of microcapsule, the directional dispersion of nano SiO2, the molecular insertion of fluorinated modifier all provide structural basis for performance synergy.

Description

Technical Field

[0001] This invention relates to the field of self-healing polymer materials, specifically to a self-healing TPU material, method, and application. Background Technology

[0002] Traditional self-healing microcapsules suffer from problems such as insufficient thermal stability of the wall material (e.g., gelatin wall material with a temperature resistance of <80℃[6]) and low core material release efficiency. Existing patent CN118978805A uses a single-layer polyurea wall material, but it has the defect of being prone to cracking at processing temperatures. In cable movement, the single-layer polyurea wall material will crack before the TPU cracks, and existing technologies usually cannot solve the problem of polyurea wall material cracking. Summary of the Invention

[0003] To address the problems existing in the background art, the present invention provides a self-healing TPU polymer material, method, and application.

[0004] The present invention achieves a synergistic improvement in strength and repair performance through directional reinforcement with nano-SiO2 and optimization of the microcapsule interface.

[0005] The technical solution adopted in this invention is: I. A self-healing TPU polymer material: The self-healing TPU material comprises a polyester TPU matrix, nano-silica, fluorinated modifier, siloxane microcapsules, antioxidant, and lubricant. Preferably, the polymer self-healing TPU material consists only of a polyester TPU matrix, nano-silica, fluorinated modifier, siloxane microcapsules, antioxidant, and lubricant.

[0006] The mass percentage relationship of the polyester-type TPU matrix, nano-silica, fluorinated modifier, siloxane microcapsules, antioxidant, and lubricant is 80-85%, 5-8%, 2-3%, 1.5-3%, 0.5-1%, and 0.3-0.5%, respectively.

[0007] The polyester-type TPU matrix is ​​mainly composed of polycaprolactone polyol and MDI.

[0008] The nano-silica was obtained by surface silane coupling modification treatment, with a particle size of 50 nm. The fluorinated modifier is a perfluoropolyether graft; The siloxane microcapsules are polyurethane-polyurea bilayer microcapsules coated with siloxane repair agents. The antioxidant is a mixture of a complex hindered phenol and a phosphite, with a mass ratio of 1:1. The complex hindered phenol is specifically pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the phosphite is specifically tris[2,4-di-tert-butylphenyl]phosphite. The lubricant is zinc stearate with a purity ≥99.5% and a particle size ≤10μm.

[0009] The lubricant is ethylene bis-stearamide. The polyester-type TPU matrix is ​​a particulate material.

[0010] The microcapsules are prepared by emulsion polymerization. The wall material is a polyurea-polyurethane bilayer structure formed by crosslinking isocyanate prepolymer and ethylenediamine. The core material is siloxane with a thickness of 5-8 μm and a core material loading rate of ≥85%.

[0011] The microcapsules have a particle size distribution of 50-200μm (D50=120μm) and a thermal decomposition temperature of ≥160℃, which meets the TPU processing temperature requirements.

[0012] The wall material of the microcapsule is a polyurethane-polyurea composite double-layer structure, and the core material is a siloxane repair agent. The polyurethane-polyurea composite bilayer structure mainly consists of a polyurea inner layer and a polyurethane outer layer. The polyurea inner layer is mainly prepared by crosslinking isocyanate prepolymer and ethylenediamine, with a mass ratio of isocyanate prepolymer to ethylenediamine crosslinking agent of 6:1. The polyurethane outer layer mainly uses polyurethane, and the siloxane repair agent is α,ω-dihydroxypolydimethylsiloxane with a viscosity of 500-800 mPa·s.

[0013] The microcapsules have an overall particle size of 50-200 μm and a thermal decomposition temperature of ≥160℃. The microcapsules are prepared using a combined emulsion polymerization-spray drying process.

[0014] The microcapsules possess high-temperature resistance and stress-responsive properties, and are used in the preparation of thermoplastic polyurethane (TPU) materials. These microcapsules are used in the co-extrusion preparation of TPU, thereby repairing cracks and fissures generated during TPU extrusion and promoting the densification of the TPU.

[0015] II. A method for preparing a self-healing TPU polymer material, the method being as follows: 1) Premixing stage: The polyester TPU matrix of TPU particles is premixed with nano silica, fluorinated modifier, antioxidant and lubricant in a high-speed mixer at 800 rpm for 15 min to form raw materials; 2) Melt co-extrusion: The product is fed into a twin-screw extruder for melt co-extrusion with segmented temperature control, and microcapsules are added in the later stage of melting; 3) Granulation: The granules after melt co-extrusion are cut underwater into granules with a diameter of 3mm×3mm, and then dried to ensure that the moisture content is ≤0.02%.

[0016] Step 2) is specifically divided into the following three stages of segmented temperature-controlled melt co-extrusion: Feeding section: 160-170℃; Plasticizing section: 190-200℃; Head section: 180-185℃ Microcapsules are then injected through the side feed port at the late melting stage of the screw at 70% position to reduce thermomechanical damage.

[0017] In the premixing stage described in section 1), the high-speed premixing speed is 800 rpm and the time is 15 min.

[0018] The microcapsules were prepared according to the following method: S1, Emulsion polymerization: The isocyanate prepolymer is dispersed in liquid paraffin containing Span 80 to form an oil phase; Then add the oil phase to the aqueous phase and emulsify by uniform stirring; Finally, ethylenediamine is added and reacted at a specific temperature for a period of time to form a polyurea inner layer; S2, Interface Enhancement: MDI-type polyurethane prepolymer is sprayed onto the inner layer of polyurea and cured at a certain temperature to form an outer polyurethane layer, thereby forming the wall material of the microcapsules. S3. Core material injection: The siloxane repair agent was injected into the wall material of the microcapsules using a vacuum infiltration method and then subjected to depressurization treatment. S4. Post-processing: Finally, the powder is spray-dried to obtain a free-flowing powder.

[0019] Step S1 specifically involves: S11. Isophorone diisocyanate (IPDI) prepolymer is dispersed as isocyanate prepolymer in liquid paraffin containing 0.5% Span 80 by mass to form an oil phase; S12. Add the oil phase to the aqueous phase for emulsification. The aqueous phase is a 1% polyvinyl alcohol solution. The mass ratio of the oil phase to the aqueous phase is 1:3. Maintain the emulsification speed at 6000 rpm for 15 min. S13. Finally, add ethylenediamine crosslinking agent and react at 40°C for 4 hours to form a polyurea inner layer; Specifically, step S2 involves spraying an MDI-type polyurethane prepolymer with a solid content of 20% onto the surface of the polyurea inner layer and curing it at 80°C for 2 hours to form the outer layer. Specifically, step S3 involves injecting α,ω-dihydroxypolydimethylsiloxane with a viscosity of 500-800 mPa·s as a siloxane repair agent and treating it under reduced pressure at 50°C for 4 hours.

[0020] The present invention relates to the application of the above-mentioned self-healing TPU polymer material in self-healing and self-healing products.

[0021] The triggering mechanism of the microcapsules in the self-healing TPU material: When the material cracks, stress concentration causes the microcapsules to rupture, and the released siloxanes react with the hydroxyl groups at the ends of the TPU molecular chains to form a Si-OC covalent repair network, thereby achieving repair.

[0022] The innovation of this invention lies in the following points: 1. In-depth innovation of the "rigid-flexible" interpenetrating network collaborative mechanism The original proposal, which proposed "a 'rigid-flexible' interpenetrating network formed by a polyester-type TPU matrix and a fluorinated modifier / nano-SiO2," has a core innovation in its multi-component directional interface design. Rigidity enhancement pathway: Nano-SiO2 forms chemical crosslinks with the TPU hard segment (MDI-derived urethane groups) through the double bonds of silane coupling agents (such as KH570), filling the interface region between the TPU soft segment (PCL polyol) and the hard segment, enhancing the crystallinity of the hard segment (XRD test shows that the crystallinity of the hard segment increases from 18% to 25%), and significantly improving the material's hardness (88A) and temperature resistance (HDT 105℃).

[0023] Flexible maintenance strategy: The perfluoropolyether segments (flexible) of the fluorinated modifier (PFPE graft) react with the hydroxyl groups of the TPU soft segments through the terminal hydroxyl groups, and insert into the soft segment molecular chains to form a flexible connection of "soft segment-fluorine chain-soft segment". This avoids the increase in brittleness caused by excessive filling of nano-SiO2 (the elongation at break only decreases from 600% to 550%, which is far better than the traditional filling system below 300%).

[0024] Trade-off breakthrough verification: Through dynamic mechanical analysis (DMA), the material's storage modulus remains at 300MPa above the glass transition temperature (Tg) (100℃) (compared to 150MPa for traditional TPU), while the loss factor (tanδ) is only 0.25 (compared to 0.35 for traditional TPU). This indicates that the "rigid-flexible" network improves high-temperature rigidity while maintaining low-temperature flexibility, completely resolving the contradiction of traditional TPU where "increased temperature resistance leads to decreased wear resistance, and increased hardness leads to decreased elongation."

[0025] 2. Precise design of intelligent triggering mechanism The innovation of the original "stress-sensitive triggering" solution lies in the precise matching of the wall material structure with the service conditions: The dual-layer wall material has a functional division of labor: the inner layer is polyurea (formed by rapid cross-linking of isocyanate prepolymer and ethylenediamine), possessing high hardness (Shore D 75) and high stress sensitivity (rupture threshold 0.5 MPa), responsible for sensing local stress concentration when the material cracks; the outer layer is polyurethane (formed by slow reaction of isocyanate prepolymer and water), possessing high flexibility (elongation at break 300%) and shear resistance, used to protect the inner polyurea layer from damage during processing (such as the shear force of twin-screw extrusion, approximately 0.3 MPa). Through finite element analysis (FEA), the stress transfer efficiency of the dual-layer wall material is 40% higher than that of the single-layer polyurea wall material, ensuring that the microcapsules only rupture when the material cracks (local stress ≥ 0.5 MPa).

[0026] Quantitative method for threshold control: By adjusting the NCO content of the isocyanate prepolymer (12%-15%) and the amount of ethylenediamine added (1.5%-2.0wt%), the crosslinking density of the polyurea inner layer is precisely controlled (gel content increases from 70% to 85%), thereby adjusting the rupture threshold from 0.3MPa (monolayer polyurea) to 0.5MPa, perfectly matching the service stress range (0.1-0.4MPa) of target applications such as automotive sealing strips and industrial rubber rollers, and avoiding accidental triggering of microcapsules during normal use.

[0027] 3. Technological breakthroughs in environmental protection processes The innovation of the original "solvent-free microcapsule preparation technology" lies in the closed-loop design of the all-aqueous system: Solvent-free mechanism: Employing emulsion polymerization with deionized water as the dispersion medium and isocyanate prepolymers (such as prepolymers of MDI and polypropylene glycol) as the oil phase, oil droplets are formed through high-speed stirring (1200 rpm). Subsequently, ethylenediamine is added as a crosslinking agent to form a polyurea-polyurethane bilayer wall material in situ on the surface of the oil droplets. The entire process requires no organic solvents, and VOC emissions are only 5 ppm as measured by GC-MS (far below the REACH regulation limit of 10 ppm).

[0028] Closed-loop wastewater treatment: Wastewater after microcapsule preparation is filtered through a ceramic membrane (0.2μm pore size) to recover unreacted isocyanate prepolymer (recovery rate ≥90%). After biochemical treatment (activated sludge method), the COD value of the filtrate is reduced from 1200mg / L to 50mg / L, meeting the national first-class discharge standard (GB 8978-1996), achieving the environmental protection goal of "zero organic solvent discharge + wastewater recycling".

[0029] The beneficial effects of this invention are: (1) Synergistic effect system: The polyester TPU matrix and the fluorinated modifier / nano SiO2 form a "rigid-flexible" interpenetrating network, which breaks through the trade-off effect of traditional TPU in terms of temperature resistance and wear resistance. (2) Intelligent triggering mechanism: The stress sensitivity of the microcapsule wall material (fracture threshold 0.5MPa) is precisely matched with the service conditions of the material. (3) Environmentally friendly process: The solvent-free microcapsule preparation technology is adopted, and the VOC emission is <10ppm, which complies with REACH regulations. The innovation of this invention lies primarily in its multi-scale, multi-component synergistic design: it resolves the performance contradictions of traditional TPU through a rigid-flexible interpenetrating network, achieves precise repair through an intelligent triggering mechanism, and meets stringent regulatory requirements through environmentally friendly processes. Structurally, the bilayer wall material of the microcapsules, the directional dispersion of nano-SiO2, and the molecular insertion of fluorinated modifiers all provide the structural basis for synergistic performance. In terms of features, the synergistic balance between strength and repair, temperature resistance and abrasion resistance, the precision of intelligent triggering, and the rigorous verification of environmental performance give this material significant market competitiveness and application value. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments.

[0031] The present invention incorporates a double-layer wall material structure and function for microcapsules in its technical solution: Inner layer (polyurea): 3-5 μm thick, formed by crosslinking isocyanate prepolymer (14% NCO content) and ethylenediamine (molar ratio 1:1.2). It has high hardness (Shore D 75) and high stress sensitivity (fracture strain 1.5%), serving as the "sensing layer" that triggers repair. SEM observation shows that the inner polyurea layer has a dense network structure, ensuring rapid rupture under stress concentration.

[0032] Outer layer (polyurethane): 2-3 μm thick, formed by the reaction of isocyanate prepolymer and water (molar ratio 1:0.8), possessing high flexibility (300% elongation at break) and shear resistance (shear strength 0.4 MPa), serving as a "buffer layer" protecting the inner layer. The outer polyurethane molecular chain contains a large number of hydroxyl groups (-OH), which can form hydrogen bonds with the hydroxyl groups of the TPU matrix, improving the interfacial bonding force between the microcapsule and the matrix (interfacial shear strength increases from 0.2 MPa to 0.5 MPa).

[0033] Core material loading rate optimization: By adjusting the volume ratio (1:3) of the oil phase (isocyanate prepolymer + core material siloxane) to the water phase of the wall material and the stirring speed (1200 rpm), the core material loading rate was increased from 75% (traditional method) to 88%, ensuring that each microcapsule releases enough siloxane (core material content ≥85wt%) for crack repair.

[0034] This invention incorporates a directional dispersion structure of nano-SiO2: Nano-sized SiO2 (50nm particle size) is uniformly distributed in the TPU matrix using in-situ dispersion technology: Dispersion mechanism: In the premixing stage, nano-SiO2 and TPU particles form a "particle-to-particle" physical adsorption through high-speed mixing (800 rpm, 15 min). Subsequently, during the melt co-extrusion process, the shear force of the twin-screw extruder (approximately 1000 s) disperses the particles. -1 The SiO2 aggregates are dispersed into single particles. The KH570 double bond of the silane coupling agent undergoes a Diels-Alder reaction with the hard segment urethane groups of TPU to form chemical crosslinks, ensuring the dispersion of SiO2 in the matrix (by TEM observation, the aggregate size is ≤200nm, and the dispersion uniformity index decreases from 0.8 to 0.3).

[0035] Interface enhancement effect: The interfacial bonding force between nano-SiO2 and the TPU matrix increased from 0.15 MPa to 0.4 MPa through single fiber pull-out tests, significantly improving the material's wear resistance (wear loss increased from 105 mm). 3 Reduced to 40mm 3 Wear rate reduced by 62%.

[0036] This invention incorporates a molecular insertion structure for the fluorinated modifier: The molecular chain of the fluorinated modifier (perfluoropolyether graft, PFPE-g-OH) reacts with the isocyanate end groups of TPU through the terminal hydroxyl groups, inserting itself between the soft segments (PCL polyol) molecular chains of TPU: Insertion mechanism: The perfluorinated segments (-CF2-CF2-) of PFPE have low surface energy (≤18mN / m). The grafted hydroxyl groups (-OH) react with the isocyanate end groups (-NCO) of TPU to form urethane bonds, thus fixing the PFPE molecular chains within the interstices of the TPU soft segments. XPS testing showed that the fluorine content on the material surface increased from 0 to 3.5 at%, forming a continuous low surface energy layer.

[0037] Oil resistance improvement mechanism: The low surface energy fluorine segments form a "barrier" on the material surface, preventing the penetration of IRM903 oil (mainly composed of aromatics and esters). The volume change rate is reduced from 25% (base TPU) to 8%, and the oil resistance is improved by 3 times (through weight change test, the weight increase rate after soaking for 72 hours is reduced from 15% to 5%).

[0038] In specific implementation, the siloxane microcapsules are polyurethane-polyurea bilayer microcapsules, with a polyurethane-polyurea composite bilayer structure as the wall material and a siloxane repair agent as the core material. The bilayer refers to the bilayer material structure of polyurethane and polyurea.

[0039] The microcapsules have an overall particle size of 50-200 μm and a thermal decomposition temperature of ≥160℃. The microcapsules are prepared using a combined emulsion polymerization-spray drying process.

[0040] The polyurethane-polyurea composite bilayer structure mainly consists of a polyurea inner layer and a polyurethane outer layer. The polyurea inner layer is mainly prepared by crosslinking isocyanate prepolymer with ethylenediamine; the mass ratio of isocyanate prepolymer to ethylenediamine crosslinking agent is 6:1. The siloxane repair agent is α,ω-dihydroxypolydimethylsiloxane with a viscosity of 500-800 mPa·s.

[0041] The preparation method of the siloxane microcapsules includes sequential processes of emulsion polymerization, interface strengthening, core material injection, and spray drying, specifically including: S1, Emulsion polymerization: The isocyanate prepolymer is dispersed in liquid paraffin containing Span 80 to form an oil phase; Add 0.1-0.3 wt% of nano-CaCO3 with a particle size of 10-50 nm to the oil phase; The oil phase is then added to the aqueous phase and emulsified by high-speed stirring. Finally, ethylenediamine is added and reacted at a specific temperature for a period of time to form a polyurea inner layer.

[0042] Step S1 specifically involves: S11. Isophorone diisocyanate (IPDI) prepolymer is dispersed as isocyanate prepolymer in liquid paraffin containing 0.5% Span 80 by mass to form an oil phase; S12. Add the oil phase to the aqueous phase for emulsification. The aqueous phase is a 1% polyvinyl alcohol solution. The mass ratio of the oil phase to the aqueous phase is 1:3. Maintain the emulsification speed at 6000 rpm for 15 min. S13. Finally, add ethylenediamine crosslinking agent and react at 40°C for 4 hours to form a polyurea inner layer.

[0043] S2, Interface Enhancement: MDI-type polyurethane prepolymer is sprayed onto the inner surface of the polyurea layer and cured at a certain temperature to form the outer polyurethane layer, thereby forming the wall material of the microcapsules.

[0044] Step S2 specifically involves spraying an MDI-type polyurethane prepolymer with a solid content of 20% onto the surface of the polyurea inner layer and curing it at 80°C for 2 hours to form the outer layer.

[0045] S3. Core material injection: The siloxane repair agent was injected into the wall material of the microcapsules using a vacuum infiltration method and then subjected to depressurization treatment. Specifically, step S3 involves injecting α,ω-dihydroxypolydimethylsiloxane with a viscosity of 500-800 mPa·s as a siloxane repair agent and treating it under reduced pressure at 50°C for 4 hours.

[0046] S4. Post-processing: Finally, the powder is spray-dried to obtain a free-flowing powder.

[0047] This invention also innovatively sets up siloxane microcapsules in polyurethane-polyurea double-layer wall material, adds nano-CaCO3 to construct a directional release mechanism, and combines it with water-based environmentally friendly process; achieving high temperature resistance to prevent processing cracking, precise stress triggering, high core material load and release rate, good compatibility with TPU, and VOC emission compliance.

[0048] The microcapsules of the present invention contain a molecular mechanism for the synergistic effect of bilayer wall materials: The inner layer of polyurea is cross-linked with isophorone diisocyanate (IPDI) prepolymer and ethylenediamine. The molecular structure is rich in rigid urea bonds (-NH-CO-NH-), which gives the wall material high hardness (Shore D≥85) and excellent thermal stability (urea bond decomposition temperature>200℃), providing rigid support for the microcapsules. The outer polyurethane layer uses an MDI-type prepolymer (containing polyether soft segments), which is covalently bonded to the inner polyurea layer through urethane bonds (-NH-CO-O-). The soft segments (polyether chains) can absorb external stress and undergo plastic deformation, thereby enhancing the interfacial toughness (peel strength ≥1.2MPa).

[0049] The double-layer structure, through the synergy of "rigid support and tough buffer", improves the temperature resistance (temperature of 5% weight loss) by 40°C compared to the single-layer polyurea structure (from 120°C to 160°C), while avoiding the defect of single-layer polyurea being brittle and prone to cracking during processing.

[0050] Stress transfer principle with directional release mechanism: This invention also uniformly disperses 0.1-0.3 wt% nano-CaCO3 (particle size 10-50 nm) in the wall material, and the difference in thermal expansion coefficient between it and the polymer matrix (CaCO3: 8 × 10⁻⁶) is significant. -6 / ℃; Polyurea: 15×10 -6 The stress at the interface is caused by the formation of micro-defects (≥0.5MPa) due to the pressure of the temperature (°C). When the composite material is subjected to external force and cracks are generated, the stress at the crack tip (≥0.5MPa) preferentially concentrates in the weak area around the nano-CaCO3, causing the wall material to fracture directionally along the defect (the angle between the fracture path and the crack propagation direction is ≤15°). This mechanism increases the core material release rate from 75% in a single-layer structure to ≥90%, and avoids false triggering in non-crack areas (such as shear stress <0.3MPa during processing, which is insufficient to activate stress concentration points).

[0051] Technologies with environmentally friendly processes: This invention uses a water-based emulsification system (the aqueous phase is a 1% polyvinyl alcohol solution, and the oil phase is a liquid paraffin dispersion of IPDI prepolymer) to replace traditional solvent-based systems (such as toluene and xylene), reducing VOC emissions from >500ppm to <50ppm (complying to the "VOC limit" requirements in Annex XVII of the REACH Regulation).

[0052] During emulsion polymerization, Span80, acting as a lipophilic emulsifier (HLB=4.3), synergistically with polyvinyl alcohol (HLB=17) to form a stable O / W emulsion (emulsion particle size ≤5μm), ensuring uniform microcapsule particle size distribution (coefficient of variation <15%). The spray drying process combines low-temperature air inlet (180℃) with rapid drying (outlet air temperature 85℃), avoiding a decrease in the loading rate of the core material (siloxane) due to high-temperature volatilization (siloxane boiling point >250℃) (loading rate maintained ≥85%).

[0053] Embodiments of the present invention: Example 1: 1) Formula components and proportions 2) Preparation process 21) Premixing stage: TPU particles, nano silica and fluorinated modifier are premixed in a high-speed mixer (800 rpm, 15 min).

[0054] 22) Melt co-extrusion: A twin-screw extruder with segmented temperature control is used. Feeding section: 160-170℃ Plasticizing section: 190-200℃ Nose section: 180-185℃ 23) Microcapsule introduction: Microcapsules are injected through the side feed port in the later stage of melting (70% position of the screw).

[0055] 24) Granulation and molding: underwater pelleting, particle size 3mm×3mm, moisture content ≤0.02% after drying.

[0056] 3) Performance index verification In the specific implementation, the prepared TPU material product was tested and verified according to the following performance indicators: Comparative Example 1: Basic TPU only: Under the same conditions, the repair rate is only 65%, and 30% of the microcapsules rupture prematurely during processing.

[0057] The test data results of Example 1 and Comparative Example 1 are compared in the table below: The comparison in the table above shows that the formulation of this invention achieves significant breakthroughs in core performance compared to basic TPU: tensile strength increases from 35MPa to 42MPa, with a mechanical strength increase of approximately 20%; although the elongation at break decreases slightly to 550%, it still maintains excellent flexibility and toughness, meeting the deformation requirements of practical applications; the self-healing efficiency jumps from 0 to 82%, reaching the technical standard of ≥80% self-healing rate at room temperature after 24 hours, far exceeding the 65% self-healing effect of basic TPU and Comparative Example 1. Combined with the tensile strength retention rate of ≥85% and DIN 53516 abrasion loss ≤40mm after aging at 105℃ and 120℃ for 500 hours as mentioned above, this further enhances the performance. 3 The formula of this invention achieves synergistic optimization of mechanical properties, self-healing ability, and environmental tolerance through a "rigid-flexible" interpenetrating network synergy mechanism and intelligent triggering design, meeting the requirements of ASTM D471 oil resistance volume change rate ≤8%. It effectively solves the problems of lack of self-healing in basic TPU and premature rupture of microcapsules in Comparative Example 1, providing key technical support for the self-healing application of polymer materials in cables, seals and other fields.

[0058] After testing, the present invention has achieved the following effects and characteristics: 1) The ultimate balance of synergistic performance Synergistic effect of strength and repair: The tensile strength of the formulation of this invention is increased from 35 MPa (base TPU) to 42 MPa (+20%), while the elongation at break only decreases from 600% to 550% (-8%), and the self-repair efficiency reaches 82% (24h room temperature repair rate). The reason is that: nano-SiO2 enhances the crystallinity of the hard segments and improves the strength; the siloxane released by the microcapsules reacts with the hydroxyl groups of TPU to form Si-OC covalent bonds, repairing the molecular chains in the cracked area and maintaining the elongation; the flexible segments of the fluorinated modifier compensate for the brittleness of nano-SiO2, achieving a synergistic effect of "strength improvement + repair performance maintenance + minimal loss of flexibility".

[0059] Synergistic effect of temperature and abrasion resistance: The HDT (1.8MPa) of the material increased from 85℃ (base TPU) to 105℃ (+23%), and the tensile strength retention rate after aging at 120℃ for 500h increased from 70% to 85%; at the same time, the abrasion resistance (wear loss) increased from 105mm. 3 Reduced to 40mm 3 (-62%). The reason is that the "rigid-flexible" interpenetrating network enhances the thermal stability of the hard segment, and the nano-SiO2 fills the interfacial gap between the soft and hard segments, reducing molecular chain slippage at high temperatures, thereby improving both temperature resistance and wear resistance.

[0060] 1) The accuracy of intelligent triggering Matching to service conditions: The rupture threshold of the microcapsules (0.5 MPa) is higher than the normal service stress (0.1-0.4 MPa) of the target application (such as automotive sealing strips), ensuring that the microcapsules do not rupture during normal use. When the material is subjected to stress exceeding the threshold (such as impact or scratches from sharp objects, stress ≥ 0.5 MPa), the microcapsules rupture to release the core material, achieving precise repair. Through simulated service tests (cyclic tensile test of automotive sealing strips, 1000 cycles, stress 0.3 MPa), the rupture rate of the microcapsules is only 5% (compared to 30% for traditional microcapsules), significantly improving the service life of the microcapsules.

[0061] Repair timeliness: The hydroxyl reaction rate between the siloxane core material (α,ω-dihydroxy polydimethylsiloxane) and TPU was tested by FTIR. After 24 hours, the reaction conversion rate reached 90%, and the crack healing rate was ≥80% (microscopic SEM showed that a continuous siloxane cross-linked network was formed in the crack area, and the crack width decreased from 10μm to below 2μm).

[0062] 1) Rigorous verification of environmental performance VOC emission test: VOC emissions during the microcapsule preparation process were tested using GC-MS. The results showed that the VOC concentration was 5 ppm (far below the REACH limit of 10 ppm).

[0063] Solvent-free closed-loop process: Wastewater from microcapsule preparation is filtered through a ceramic membrane to recover unreacted isocyanate prepolymer (recovery rate ≥90%). After biochemical treatment, the COD value of the filtrate is reduced to 50 mg / L (national first-class emission standard), achieving the environmental protection goal of "zero organic solvent discharge + wastewater recycling".

Claims

1. A self-healing TPU polymer material, characterized in that: The self-healing TPU material comprises a polyester TPU matrix, nano-silica, fluorinated modifier, siloxane microcapsules, antioxidant, and lubricant. The mass percentage relationship of the polyester-type TPU matrix, nano-silica, fluorinated modifier, siloxane microcapsules, antioxidant, and lubricant is 80-85%, 5-8%, 2-3%, 1.5-3%, 0.5-1%, and 0.3-0.5%, respectively.

2. The self-healing TPU polymer material according to claim 1, characterized in that: The polyester-type TPU matrix is ​​mainly composed of polycaprolactone polyol reacted with MDI. The nano-silica was obtained by surface silane coupling modification treatment, with a particle size of 50 nm. The fluorinated modifier is a perfluoropolyether graft; The siloxane microcapsules are polyurethane-polyurea bilayer microcapsules coated with siloxane repair agents. The antioxidant is a mixture of a complex hindered phenol and a phosphite, with a mass ratio of 1:

1. The complex hindered phenol is specifically pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the phosphite is specifically tris[2,4-di-tert-butylphenyl]phosphite. The lubricant is zinc stearate with a purity ≥99.5% and a particle size ≤10μm.

3. The self-healing TPU polymer material according to claim 1, characterized in that: The microcapsules are prepared by emulsion polymerization. The wall material is a polyurea-polyurethane bilayer structure formed by crosslinking isocyanate prepolymer and ethylenediamine, and the core material is siloxane with a thickness of 5-8 μm.

4. The self-healing TPU polymer material according to claim 1, characterized in that: The wall material of the microcapsule is a polyurethane-polyurea composite double-layer structure, and the core material is a siloxane repair agent. The polyurethane-polyurea composite bilayer structure is mainly composed of a polyurea inner layer and a polyurethane outer layer. The polyurea inner layer is prepared by crosslinking isocyanate prepolymer with ethylenediamine, and the polyurethane outer layer is made of polyurethane. The siloxane repair agent is α,ω-dihydroxypolydimethylsiloxane with a viscosity of 500-800 mPa·s.

5. A method for preparing any of the self-healing TPU materials according to claims 1-4, characterized in that: The preparation method is as follows: 1) Premixing stage: Polyester TPU matrix is ​​premixed with nano silica, fluorinated modifier, antioxidant and lubricant in a high-speed mixer at high speed; 2) Melt co-extrusion: The product is fed into a twin-screw extruder for melt co-extrusion with segmented temperature control, and microcapsules are added in the later stage of melting; 3) Granulation and molding: The treated granules are cut underwater into granules with a diameter of 3mm×3mm, and then dried to ensure that the moisture content is ≤0.02%.

6. The preparation method according to claim 5, characterized in that: Step 2) is specifically divided into the following three stages of segmented temperature-controlled melt co-extrusion: Feeding section: 160-170℃; Plasticizing section: 190-200℃; Head section: 180-185℃ Microcapsules are then injected through the side feed port at the late melting stage of the screw at 70% position.

7. The preparation method according to claim 5, characterized in that: In the premixing stage described in section 1), the high-speed premixing speed is 800 rpm and the time is 15 min.

8. The preparation method according to claim 5, characterized in that: The microcapsules were prepared according to the following method: S1, Emulsion polymerization: The isocyanate prepolymer is dispersed in liquid paraffin containing Span 80 to form an oil phase; Then add the oil phase to the aqueous phase and emulsify by uniform stirring; Finally, ethylenediamine is added and reacted at a specific temperature for a period of time to form a polyurea inner layer; S2, Interface Enhancement: MDI-type polyurethane prepolymer is sprayed onto the inner surface of the polyurea layer and cured at a certain temperature to form the outer polyurethane layer, thereby forming the wall material of the microcapsules. S3. Core material injection: The siloxane repair agent was injected into the wall material of the microcapsules using a vacuum infiltration method and then subjected to depressurization treatment. S4. Post-processing: Finally, the powder is spray-dried to obtain a free-flowing powder.

9. The preparation method according to claim 8, characterized in that: Step S1 specifically involves: S11. Isophorone diisocyanate (IPDI) prepolymer is dispersed as isocyanate prepolymer in liquid paraffin containing 0.5% Span 80 by mass to form an oil phase; S12. Add the oil phase to the aqueous phase for emulsification. The aqueous phase is a 1% polyvinyl alcohol solution. The mass ratio of the oil phase to the aqueous phase is 1:

3. Maintain the emulsification speed at 6000 rpm for 15 min. S13. Finally, add ethylenediamine crosslinking agent and react at 40°C for 4 hours to form a polyurea inner layer; Specifically, step S2 involves spraying an MDI-type polyurethane prepolymer with a solid content of 20% onto the surface of the polyurea inner layer and curing it at 80°C for 2 hours to form the outer layer. Specifically, step S3 involves injecting α,ω-dihydroxypolydimethylsiloxane with a viscosity of 500-800 mPa·s as a siloxane repair agent and treating it under reduced pressure at 50°C for 4 hours.

10. An application of a self-healing TPU material comprising any one of the self-healing TPU materials according to claims 1-3 or any one of the preparation methods according to claims 4-7, characterized in that, Applications in self-healing and self-healing products.

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