A composite tube material for high-pressure air ribs and its preparation method

Abstract

This invention relates to the field of polymer compound composition technology, specifically disclosing a composite tube material for high-pressure air ribs and its preparation method. The composite tube material comprises, by weight, 70-85 parts of alicyclic isocyanate-modified thermoplastic polyurethane elastomer, 18-25 parts of modified reinforcing fiber, 4-6 parts of interface compatibilizer, 2-4 parts of composite anti-aging system, 1-3 parts of nano-reinforcing agent, 5-15 parts of composite flame retardant system, 1-2 parts of processing aid, and 10-45 parts of solvent. The preparation method includes nano-slurry pretreatment, fiber modification treatment, raw material premixing, and melt blending granulation. The composite tube material of this invention possesses high mechanical strength, excellent anti-aging properties, environmentally friendly and efficient flame retardancy, and good interfacial bonding strength, meeting the requirements for high-pressure air ribs. The preparation process is simple and controllable, suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of polymer compound composition technology, and more specifically to a composite tube material for high-pressure air ribs and its preparation method. Background Technology

[0002] High-pressure air ribs, as a key inflatable load-bearing structure, are expanding their applications from traditional military and aerospace fields to civilian emergency response and outdoor recreation. This places more comprehensive demands on the tubing materials that form the core of these structures: not only are excellent mechanical properties and airtightness required, but also superior weather resistance (especially resistance to UV yellowing), higher flame retardant safety levels, and more stable long-term performance have become essential characteristics of the next generation of products.

[0003] Current technologies mostly use conventional aromatic TPU as the matrix, but its tendency to yellow under ultraviolet light affects the product's appearance and long-term performance. The dispersion of nanofillers largely relies on melt shearing, which has limited effectiveness. Flame-retardant systems also often present a trade-off between efficiency and migration risk. Therefore, developing a new material system that comprehensively addresses these problems is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a composite tube material for high-pressure air ribs and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, on the one hand, the present invention provides a composite tube material for high-pressure air ribs, comprising, by weight, the following components: 70-85 parts of alicyclic isocyanate modified thermoplastic polyurethane elastomer, 18-25 parts of modified reinforcing fiber, 4-6 parts of interface compatibilizer, 2-4 parts of composite anti-aging system, 1-3 parts of nano-reinforcing agent, 5-15 parts of composite flame retardant system, 1-2 parts of processing aid, and 10-45 parts of solvent.

[0006] Preferably, the alicyclic isocyanate-modified thermoplastic polyurethane elastomer is a mixture of HMDI-based polyester TPU and HMDI-based polyether TPU, with a weight ratio of (3-4):1. HMDI (hexamethylene diisocyanate)-based polyester or polyether TPU is selected, preferably mixed in a (3-4):1 ratio. HMDI has an alicyclic structure and no benzene ring, exhibiting superior anti-yellowing and anti-aging properties compared to aromatic isocyanate-modified TPU. Polyester TPU has high mechanical strength and good wear resistance, while polyether TPU has excellent flexibility and hydrolysis resistance. The combination of the two can synergistically improve the overall mechanical properties of the material, with an elongation at break ≥500%, ensuring the material's elastic recovery ability under high pressure.

[0007] Preferably, the modified reinforcing fiber is a glass fiber or aramid fiber that has undergone low-temperature plasma pretreatment and then has been coated with an aminosilane coupling agent and a portion of the interface compatibilizer. The low-temperature plasma treatment power is 300-500W, and the treatment time is 2-5 minutes. Glass fiber or aramid fiber is selected, pretreated with low-temperature plasma, and then coated with an aminosilane coupling agent and a portion of the interface compatibilizer. Low-temperature plasma treatment (300-500W, 2-5 minutes) can etch the fiber surface, increasing surface roughness and active groups; the amino groups of the aminosilane coupling agent can react with the hydroxyl groups on the fiber surface, and the isocyanate groups can react with the TPU matrix. The long flexible chains of the interface compatibilizer can improve the interfacial bonding force between the fiber and the matrix, reduce interfacial defects, and significantly improve the tensile strength and tear resistance of the material.

[0008] Preferably, the nano-reinforcing agent is stearic acid-modified nano-silica. Before being added, the nano-reinforcing agent needs to be prepared with some processing aids to form a pre-dispersed slurry with a solid content of 10%-20%, and then subjected to ultrasonic treatment with a power of 500-1000W for 10-30 minutes. This can effectively prevent the agglomeration of nanoparticles, and the agglomerate size is <80nm. The nano-silica uniformly dispersed in the matrix can improve the tensile strength, hardness and wear resistance of the material through the nano-reinforcing effect.

[0009] Preferably, the composite flame retardant system is a phosphorus-nitrogen-based halogen-free intumescent flame retardant, which is composed of an acid source, a carbon source and a gas source, with a weight ratio of (3-4):(1-1.5):1.

[0010] Preferably, the acid source is ammonium polyphosphate (APP), the carbon source is pentaerythritol (PER), and the gas source is melamine (MEL). APP is the acid source, which decomposes upon heating to produce phosphoric acid; PER is the carbon source, which dehydrates to form carbon under the catalysis of phosphoric acid; and MEL is the gas source, which releases ammonia upon heating. The three components work synergistically to form a dense, expanded carbon layer, which blocks heat and oxygen transfer, achieving highly efficient flame retardancy with a limiting oxygen index ≥30%, and a mass loss rate of <5% after baking at 85°C for 168 hours. It also exhibits good temperature stability and is environmentally friendly and halogen-free.

[0011] The processing aids selected are zinc stearate and polyethylene wax, which are mixed in a 1:1 mass ratio to improve the melt flowability of the material and enhance its processing and molding performance.

[0012] Preferably, the composite anti-aging system is a mixture of hindered phenolic antioxidants, phosphite antioxidants, and benzotriazole UV absorbers, with a weight ratio of 1:(1-1.5):(0.8-1.2). The hindered phenolic antioxidant is primarily antioxidant 1010, which can capture free radicals; the phosphite antioxidant is primarily antioxidant 168, which can decompose hydrogen peroxide; and the benzotriazole UV absorber is UV-326, which can absorb ultraviolet light. The synergistic effect of these three components significantly improves the material's resistance to thermo-oxidative aging and UV aging, extending its service life.

[0013] Preferably, the interface compatibilizer is a polyurethane prepolymer with both isocyanate groups and long flexible chains. By selecting a polyurethane prepolymer with both isocyanate groups and long flexible chains, the isocyanate groups can react with the amino and hydroxyl groups on the surface of the reinforcing fiber and the terminal hydroxyl groups of the TPU matrix, while the long flexible chains can alleviate interfacial stress concentration, further improving the interfacial compatibility between the fiber and the matrix and preventing fiber debonding.

[0014] On the other hand, the present invention also provides a method for preparing a composite tube material for high-pressure air ribs, comprising the following steps:

[0015] The nano-reinforcing agent is mixed with some processing aids and solvents in a certain proportion, and then subjected to ultrasonic treatment with a power of 500-1000W for 10-30 minutes to prepare a nano-predispersed slurry. Subsequently, it is concentrated and dried to obtain a nano-composite masterbatch.

[0016] First, the reinforcing fiber is subjected to low-temperature plasma treatment with a power of 300-500W for 2-5 minutes. Then, it is immersed in a mixed solution composed of an aminosilane coupling agent, an interfacial compatibilizer (30%-50% of the total weight of the interfacial compatibilizer), and an ethanol aqueous solution, and reacted at 70-85°C for 2-4 hours. After centrifugation, the precipitate is dried to obtain the modified reinforcing fiber. The interfacial bonding between the fiber and the matrix is ​​improved by a two-step modification method of low-temperature plasma etching + coupling agent + compatibilizer composite coating.

[0017] According to the formula, the alicyclic isocyanate modified thermoplastic polyurethane elastomer, nanocomposite masterbatch, modified reinforcing fiber, composite flame retardant system, composite anti-aging system, and remaining processing aids and interface compatibilizers are placed in a high-speed mixer and mixed at a speed of 2000-3000 rpm for 5-10 minutes to obtain a uniform premix.

[0018] The premixed material is fed into a co-rotating parallel twin-screw extruder for melt blending, extrusion, cooling, traction, and pelletizing. The temperature range from the feed port to the die head of the twin-screw extruder is set at 165℃, 175℃, 185℃, 195℃, and 190℃, with a screw speed of 250-350 rpm and a vacuum degree controlled at -0.095 to -0.098 MPa. Controlling the screw speed and vacuum degree ensures complete melting and eliminates air bubbles.

[0019] Preferably, the solvent is anhydrous ethanol. Using anhydrous ethanol as the pre-dispersion medium for the nano-reinforcing agent provides a uniformly dispersed environment for the nanoparticles, preventing their agglomeration in the dry state. Furthermore, it is completely removed during vacuum drying in the preparation process, leaving no residue in the final product and not affecting the material's core properties such as mechanical properties and flame retardant performance.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention eliminates the root cause of UV-induced yellowing caused by benzene rings at the molecular structure by using alicyclic TPU based on HMDI as the matrix, thereby fundamentally improving the material's weather resistance and simultaneously endowing it with a higher elongation at break (≥500%). By introducing an ultrasonic dispersion pretreatment process using nano-SiO2, the agglomerate size is controlled below 80nm in the early stages of batching using the cavitation effect, laying a perfect dispersion foundation for subsequent melt blending. This maximizes its role as a heterogeneous nucleation point and physical crosslinking point, significantly improving the material's elastic modulus and heat distortion temperature. By employing a phosphorus-nitrogen synergistic expansion flame retardant system, a dense porous expansion char layer is generated in the condensed phase during combustion, achieving highly efficient heat insulation and oxygen suppression. This not only raises the limiting oxygen index (LOI) to a high flame retardant level of ≥30%, but also fundamentally solves the migration problem of small molecule flame retardants (migration rate <5%) through the solidification charring mechanism. The synergistic effect of these three core technologies has resulted in a high-pressure air-ribbed composite tube material that has made leapfrog progress in terms of yellowing resistance, mechanical toughness, modulus, thermal stability, and long-term flame retardancy and safety, with overall performance far exceeding that of existing technology systems. Detailed Implementation

[0022] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0023] It should be noted that all reagents and raw materials used in this invention are commercially available, and the reagents are of analytical grade.

[0024] The HMDI-based polyester TPU is sourced from Huntsman Polyurethanes (Shanghai) Co., Ltd., and its model number is S6440.

[0025] The HMDI-based polyether TPU is sourced from Huntsman Polyurethanes (Shanghai) Co., Ltd., and its model number is A92P4207.

[0026] The epoxy-modified aromatic polyurethane is sourced from Complex High-Tech Materials (Shanghai) Co., Ltd., and its model number is EPU-105.

[0027] The interface compatibilizer is sourced from Covestro Polymers (China) Co., Ltd., and its model number is Desmodur® MS-242.

[0028] The nano-enhancing agent is from Xi'an Qiyue Biotechnology Co., Ltd., and its model number is Q-0347854.

[0029] The isocyanate-siloxane bifunctional crosslinking agent is from Nanjing Nengde New Material Technology Co., Ltd., and its model number is SCA-Y25M.

[0030] Example 1

[0031] Raw material preparation: The components are as follows, by weight:

[0032] HMDI-based polyester TPU: 52.5 parts; HMDI-based polyether TPU: 17.5 parts (weight ratio 3:1);

[0033] Glass fiber: 18 parts;

[0034] Interface compatibilizer: 4 parts;

[0035] Composite anti-aging system: 2 parts (antioxidant 1010: antioxidant 168: UV-326 = 1:1:0.8 (by weight)).

[0036] Nano-reinforcing agent: 1 part;

[0037] Composite flame retardant system: 5 parts (APP:PER:MEL=3:1:1 (by weight));

[0038] Processing aid: 1 part (zinc stearate: polyethylene wax = 1:1 (by weight));

[0039] Solvent (anhydrous ethanol): 10 parts.

[0040] Preparation method:

[0041] (1) Pretreatment of nano slurry: The nano reinforcing agent is mixed with part (0.3 parts) of processing aid and solvent anhydrous ethanol, treated with 500W ultrasonic for 30min, concentrated under reduced pressure, and then dried to obtain nano composite masterbatch;

[0042] (2) Fiber modification treatment: Glass fiber is treated with low temperature plasma at 300W and 30℃ for 5min, and then immersed in a mixed solution consisting of 2.8 parts KH-550 and part (2 parts) of interface compatibilizer and ethanol aqueous solution (ethanol:water = 9:1, v / v, accounting for 86.3% of the mixed solution). The reaction vessel is sealed and reacted at 70℃ for 4h. Then, the centrifuged precipitate is dried to obtain modified glass fiber.

[0043] (3) Raw material premixing: According to the formula, the polyester TPU and polyether TPU based on HMDI, nanocomposite masterbatch, modified glass fiber, composite flame retardant system, composite anti-aging system, and remaining processing aids and interface compatibilizers are placed in a high-speed mixer and mixed at 2000 rpm for 10 min to obtain the premix.

[0044] (4) Melt blending and granulation: The premixed material is fed into a twin-screw extruder for extrusion and granulation. The temperature range from the feed port to the die head of the twin-screw extruder is set to 165℃, 175℃, 185℃, 195℃, and 190℃. The screw speed is 250 rpm and the vacuum degree is -0.095 MPa to obtain the tube material.

[0045] Example 2

[0046] Raw material preparation: The components are as follows, by weight:

[0047] HMDI-based polyester TPU: 60 parts; HMDI-based polyether TPU: 20 parts (weight ratio 3:1);

[0048] Aramid fiber: 21 parts;

[0049] Interface compatibilizer: 5 parts;

[0050] Composite anti-aging system: 3 parts (antioxidant 1010: antioxidant 168: UV-326 = 1:1.2:1.0 (by weight)).

[0051] Nano-reinforcing agent: 2 parts;

[0052] Composite flame retardant system: 10 parts (APP:PER:MEL=3.5:1.2:1 (by weight));

[0053] Processing aids: 1.5 parts (zinc stearate: polyethylene wax = 1:1 (by weight));

[0054] Solvent (anhydrous ethanol): 30 parts.

[0055] Preparation method:

[0056] (1) Pretreatment of nano slurry: The nano reinforcing agent is mixed with part (0.5 parts) of processing aid and anhydrous ethanol, and treated with ultrasonic waves at 750W for 20 minutes. Then, it is concentrated under reduced pressure and dried to obtain nano composite masterbatch.

[0057] (2) Fiber modification treatment: Aramid fibers were treated with low-temperature plasma at 400W and 40℃ for 3.5min, and then immersed in a mixed solution consisting of 4.0 parts KH-550, a portion (2 parts) of interfacial compatibilizer and an ethanol aqueous solution (ethanol:water = 9:1, v / v, accounting for 85.0% of the mixed solution). The reaction vessel was sealed and reacted at 75℃ for 3h. The centrifuged precipitate was then dried to obtain modified aramid fibers.

[0058] (3) Raw material premixing: According to the formula, the polyester TPU and polyether TPU based on HMDI, nanocomposite masterbatch, modified aramid fiber, composite flame retardant system, composite anti-aging system, and remaining processing aids and interface compatibilizers are placed in a high-speed mixer and mixed at 2500 rpm for 7 min to obtain the premix.

[0059] (4) Melt blending and granulation: The premixed material is fed into a twin-screw extruder for extrusion and granulation. The temperature range from the feed port to the die head of the twin-screw extruder is set to 165℃, 175℃, 185℃, 195℃, and 190℃. The screw speed is 300 rpm and the vacuum degree is -0.096 MPa to obtain the tube material.

[0060] Example 3

[0061] Raw material preparation: The components are as follows, by weight:

[0062] HMDI-based polyester TPU: 68 parts; HMDI-based polyether TPU: 17 parts (weight ratio 4:1).

[0063] Glass fiber: 23 parts;

[0064] Interface compatibilizer: 5 parts;

[0065] Composite anti-aging system: 3 parts (antioxidant 1010: antioxidant 168: UV-326 = 1:1.5:1.2 (by weight)).

[0066] Nano-reinforcing agent: 2 parts;

[0067] Composite flame retardant system: 12 parts (APP:PER:MEL=4:1.5:1 (by weight));

[0068] Processing aids: 1.8 parts (zinc stearate: polyethylene wax = 1:1 (by weight));

[0069] Solvent (anhydrous ethanol): 25 parts.

[0070] Preparation method:

[0071] (1) Pretreatment of nano slurry: The nano reinforcing agent is mixed with part (0.6 parts) of processing aid and anhydrous ethanol, and then treated with ultrasonic waves at 1000W for 10 min. After vacuum concentration and drying, nano composite masterbatch is obtained.

[0072] (2) Fiber modification treatment: Glass fibers are treated with low-temperature plasma at 500W and 45℃ for 2min, and then immersed in a mixed solution consisting of 5.4 parts KH-550 and part (2.5 parts) of interface compatibilizer and ethanol aqueous solution (ethanol:water = 9:1, v / v, accounting for 82.4% of the mixed solution). The reaction vessel is sealed and reacted at 80℃ for 2.5h. Then, the precipitate is taken by centrifugation and dried to obtain modified glass fibers.

[0073] (3) Raw material premixing: According to the formula, the polyester TPU and polyether TPU based on HMDI, nanocomposite masterbatch, modified glass fiber, composite flame retardant system, composite anti-aging system, and remaining processing aids and interface compatibilizers are placed in a high-speed mixer and mixed at 3000 rpm for 5 min to obtain the premix.

[0074] (4) Melt blending and granulation: The premixed material is fed into a twin-screw extruder for extrusion and granulation. The temperature range from the feed port to the die head of the twin-screw extruder is set to 165℃, 175℃, 185℃, 195℃, and 190℃. The screw speed is 350 rpm and the vacuum degree is -0.098 MPa to obtain the tube material.

[0075] Example 4

[0076] Raw material preparation: The components are as follows, by weight:

[0077] HMDI-based polyester TPU: 63 parts; HMDI-based polyether TPU: 18 parts (weight ratio 3.5:1).

[0078] Aramid fiber: 25 parts;

[0079] Interface compatibilizer: 6 parts;

[0080] Composite anti-aging system: 4 parts (antioxidant 1010: antioxidant 168: UV-326 = 1:1.3:1.1 (by weight)).

[0081] Nano-reinforcing agent: 3 parts;

[0082] Composite flame retardant system: 15 parts (APP:PER:MEL=3.8:1.4:1 (by weight));

[0083] Processing aids: 2 parts (zinc stearate: polyethylene wax = 1:1 (by weight));

[0084] Solvent (anhydrous ethanol): 45 parts.

[0085] Preparation method:

[0086] (1) Pretreatment of nano slurry: The nano reinforcing agent is mixed with part (0.8 parts) of processing aid and anhydrous ethanol, and treated with ultrasonic waves at 800W for 15 minutes. After concentration and drying, nano composite masterbatch is obtained.

[0087] (2) Fiber modification treatment: Aramid fibers were treated with low-temperature plasma at 450W and 35℃ for 4 min, and then immersed in a mixed solution consisting of 5.5 parts KH-550 and part (2.4 parts) of interfacial compatibilizer and ethanol aqueous solution (ethanol:water = 9:1, v / v, accounting for 84.2% of the mixed solution). The reaction vessel was sealed and reacted at 85℃ for 2 h. Then, the centrifuged precipitate was dried to obtain modified aramid fibers.

[0088] (3) Raw material premixing: According to the formula, the polyester TPU and polyether TPU based on HMDI, nanocomposite masterbatch, modified aramid fiber, composite flame retardant system, composite anti-aging system, and remaining processing aids and interface compatibilizers are placed in a high-speed mixer and mixed at 2800 rpm for 6 min to obtain the premix.

[0089] (4) Melt blending and granulation: The premixed material is fed into a twin-screw extruder for extrusion and granulation. The temperature range from the feed port to the die head of the twin-screw extruder is set to 165℃, 175℃, 185℃, 195℃, and 190℃. The screw speed is 320 rpm and the vacuum degree is -0.097 MPa to obtain the tube material.

[0090] Comparative Example 1

[0091] Compared with Example 2, the reinforcing fiber was not subjected to low-temperature plasma pretreatment and composite coating modification, while the remaining components and preparation process were the same.

[0092] Comparative Example 2

[0093] Compared with Example 2, an equal amount of microencapsulated red phosphorus flame retardant (from Dongguan Hongtaiji Flame Retardant Materials Co., Ltd.) was used to replace the composite flame retardant system, while the remaining components and preparation process remained the same.

[0094] Comparative Example 3

[0095] Compared to Example 2, an equal amount of conventional MDI-type aromatic TPU (Covestro, Texin® 250DE) was used to replace the alicyclic isocyanate-modified thermoplastic polyurethane elastomer, while the remaining components and preparation process remained the same.

[0096] Comparative Example 4

[0097] Compared to Example 2, the composite flame retardant system uses only 12 parts of APP (without PER and MEL), while the remaining components and preparation process are the same.

[0098] Comparative Example 5

[0099] Compared to Example 2, the aramid fibers were only pretreated with low-temperature plasma (without KH-550 and interface compatibilizer composite coating).

[0100] The composite tube materials prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to performance tests, and the test standards and methods are as follows.

[0101] 1. Tensile strength and elongation at break

[0102] The testing standard is based on GB / T 1040.2-2006 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics". The test method is as follows: The composite tube material is cut into dumbbell-shaped standard specimens (Type 1A, total length 150mm, gauge length 50mm, width 10mm, thickness 2mm). A universal testing machine is used to conduct a uniaxial tensile test at a tensile rate of 50mm / min. The maximum tensile force and the elongation of the gauge length at the time of specimen breakage are recorded. The tensile strength (maximum tensile force divided by the original cross-sectional area of ​​the specimen) and the elongation at break (the percentage of the elongation of the gauge length at the time of breakage to the original gauge length) are calculated respectively.

[0103] 2. Maximum withstand pressure

[0104] The testing standard is based on GB / T 15560-1995 "Hydraulic instantaneous burst and pressure resistance test method for plastic pipes for fluid transportation". The test method is as follows: after the woven pipe is formed, a 300mm long pipe section is cut, and both ends are fixed with special sealing joints. The pipe is connected to a hydraulic testing system and the pressure is gradually increased at a rate of 0.1MPa / min. The pressure change of the pipe section is monitored in real time until the pipe section ruptures or obvious leakage occurs. The maximum pressure value at the moment of rupture is recorded as the maximum withstand pressure.

[0105] 3. Limiting Oxygen Index (LOI)

[0106] The testing standard is based on GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". The testing method is as follows: the material is processed into a standard sample with dimensions of 80mm×10mm×4mm, which is vertically fixed in the combustion chamber of the oxygen index tester. The flow rate of the mixed gas of oxygen and nitrogen is adjusted so that the oxygen concentration changes according to a certain gradient. The top of the sample is ignited, and the combustion of the sample is observed. The lowest oxygen concentration when the sample combustion time is ≥3min or the combustion length is ≥50mm is recorded, which is the limiting oxygen index.

[0107] 4. Tensile strength retention rate after aging, yellowing index after aging

[0108] The anti-aging performance testing standard is based on GB / T 16422.2-2014 "Laboratory Light Source Exposure Test Methods for Plastics - Part 2: Xenon Arc Lamp". The test method is as follows: the sample is placed in a xenon lamp aging test chamber, with the irradiance set to 0.51 W / (m²・nm) (340 nm), blackboard temperature to 65℃, and relative humidity to 50%, and continuously aged for 1000 h. After aging, the tensile strength is tested according to GB / T 1040.2-2006, and the percentage of the tensile strength after aging to the original tensile strength is calculated, which is the tensile strength retention rate. At the same time, according to GB / T 2409-1980 "Test Method for Yellow Index of Plastics", the yellowing index (ΔYI) of the aged sample is determined using a colorimeter, and compared with the unaged sample.

[0109] 5. Interfacial peel strength

[0110] The testing standard is based on GB / T 2790-1995 "Test Method for 180° Peel Strength of Adhesives - Flexible Materials vs. Rigid Materials". The testing method is as follows: Modified reinforcing fibers and TPU matrix are made into "fiber-matrix" composite peel test specimens (specimen width 25mm, length 150mm, fiber exposed end length 50mm). A universal testing machine is used to perform a 180° peel test at a rate of 50mm / min. The average peel force during the peeling process is recorded, and the average peel force is divided by the specimen width to obtain the interfacial peel strength.

[0111] 6. Quality loss rate

[0112] The testing standard refers to GB / T 11997-2008 "Plastic Multipurpose Test Samples". The testing method is as follows: Take a material sample dried to constant weight (mass recorded as m0), place it in an 85℃ forced-air drying oven for constant temperature baking for 168h, take it out and place it in a desiccator to cool to room temperature, weigh the mass of the cooled sample (recorded as m1), and calculate the mass loss rate according to the formula (m0-m1) / m0×100%.

[0113] 7. Flammability rating (UL94)

[0114] The testing standard is based on UL94-2021 "Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances". The testing method is as follows: the material is processed into a standard sample of 127mm×12.7mm×3.2mm, which is vertically fixed in the combustion test device. The top of the sample is ignited with a specified flame (20mm high) for 10s. After the flame is removed, the flaming time and the flameless time of the sample are recorded. It is observed whether there are any drips that ignite the degreased cotton below. The flammability rating (V-0, V-1, V-2, etc.) is determined according to the combustion behavior. The flammability rating determination index is shown in Table 1.

[0115] Table 1. Combustion Rating Determination Criteria

[0116] Single flaming combustion time After two ignitions, the duration of each flaming combustion session is ≤10s. After two ignitions, the duration of each flaming combustion session is ≤30s. After two ignitions, the duration of each flaming combustion session is ≤30s. Total time of two flaming combustion cycles The sum of the two flaming combustion times is ≤50s The sum of the two flaming combustion times is ≤250s The sum of the two flaming combustion times is ≤250s Flameless combustion time After two ignitions, the flameless combustion time was ≤30s. After two ignitions, the flameless combustion time was ≤60s. After two ignitions, the flameless combustion time was ≤60s. Ignition of dripping material No dripping, or the dripping does not ignite the absorbent cotton. No dripping, or the dripping does not ignite the absorbent cotton. There were dripping substances, and these dripping substances ignited the absorbent cotton. Sample flammability limits The combustion flame must not spread to the specimen clamping end (marked line 100mm from the top). The combustion flame must not spread to the sample clamping end. The combustion flame must not spread to the sample clamping end.

[0117] 8. Hydrolysis resistance (tensile strength retention rate after boiling in water at 70℃ for 72 hours)

[0118] The testing standard refers to GB / T 15593-1995 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The test method is as follows: place the standard tensile specimen in a constant temperature water bath at 70℃ and boil it for 72 hours. After taking it out, use filter paper to absorb the surface moisture and place it in a standard environment (23℃, relative humidity 50%) for 24 hours. Test the tensile strength according to GB / T 1040.2-2006. Calculate the percentage of the tensile strength after hydrolysis to the original tensile strength, which is the hydrolysis resistance tensile strength retention rate.

[0119] The test results of the relevant performance of the tube materials in the examples and comparative examples are shown in Table 2.

[0120] Table 2 Performance Test Results

[0121] Tensile strength (MPa) 42.3 48.6 51.2 53.8 34.2 46.8 45.4 38.5 47.2 Elongation at break (%) 580 620 605 630 490 585 540 520 605 Maximum withstand pressure (MPa) 3.8 4.5 4.8 5.0 2.9 4.1 3.7 3.5 4.3 Limiting Oxygen Index (LOI, %) 30.2 32.6 33.8 34.5 32.3 27.7 32.1 32.4 25.3 Tensile strength retention rate after aging (%) 89.5 92.3 93.1 91.7 86.7 90.3 72.4 91.8 91.5 Yellowing index after aging 1.8 1.5 1.3 1.6 1.4 1.5 9.2 1.6 1.4 Interfacial peel strength (N / mm) 3.2 3.8 4.2 4.3 2.0 3.6 3.5 2.5 3.7 Quality loss rate (%) 3.4 2.9 2.5 2.6 2.8 3.5 3.1 3.0 3.1 Flammability rating (UL94) V-0 V-0 V-0 V-0 V-0 V-2 V-0 V-0 V-2 Hydrolysis resistance (tensile strength retention rate after boiling in water at 70℃ for 72 hours, %) 85.1 88.6 90.4 89.3 84.5 82.3 78.6 85.2 87.9

[0122] Compared with Example 2, Comparative Example 1 showed a significant decrease in interfacial bonding performance and mechanical properties. The interfacial peel strength of Comparative Example 1 was only 2.0 N / mm (compared to 3.8 N / mm in Example 2, a decrease of 47.4%), the tensile strength was 34.2 MPa (a decrease of 29.6%), and the maximum withstand pressure was 2.9 MPa (a decrease of 35.6%). The main reasons are: without low-temperature plasma pretreatment, the fiber surface lacked microscopic etching, resulting in a small specific surface area and a lack of active groups (hydroxyl and carboxyl groups); without the aminosilane coupling agent-KH-550 composite coating, a chemical bond connection between the fiber, coupling agent, compatibilizer, and TPU matrix could not be formed. The loose interfacial bonding, relying solely on physical mixing, led to fiber debonding under stress, thus reducing overall mechanical properties and high-pressure resistance.

[0123] Compared with Example 2, Comparative Example 2 showed a significant deterioration in flame retardant performance and a decrease in temperature stability. The LOI of Comparative Example 2 was only 27.7% (compared to 32.5% in Example 2, a decrease of 14.7%), the flammability rating dropped to V-2, and the mass loss rate was 3.5% (an increase of 25%). The main reason is that the microencapsulated red phosphorus flame retardant is an additive flame retardant that relies solely on gas-phase flame retardancy (releasing PO free radicals to capture combustion free radicals), without the barrier effect of an expanded char layer, resulting in low flame retardant efficiency. Furthermore, red phosphorus is easily oxidized and decomposed at high temperatures (baking at 85°C), leading to increased mass loss. In contrast, the phosphorus-nitrogen-based intumescent flame retardant system of this invention forms a dense expanded char layer through the synergistic effect of APP (acid source), PER (carbon source), and MEL (gas source), which can not only block heat and oxygen but also possess excellent thermal stability, resulting in a more durable and environmentally friendly flame retardant effect.

[0124] Compared to Example 2, Comparative Example 3 exhibited extremely poor anti-aging and anti-yellowing properties. The tensile strength retention rate after aging in Comparative Example 3 was only 72.4% (compared to 92.3% in Example 2, a decrease of 21.6%), and the yellowing index after aging was 9.2 (compared to 1.5 in Example 2, an increase of 513.3%). Hydrolysis resistance also decreased significantly (tensile strength retention rate 78.6% vs 88.6%). The main reason is that MDI is an aromatic isocyanate with a benzene ring in its molecular structure, which is prone to oxidative breakage of the benzene ring under ultraviolet light, leading to yellowing and degradation of mechanical properties. HMDI, on the other hand, is an alicyclic isocyanate without a benzene ring structure, resulting in higher chemical stability. Furthermore, the combination of polyester and polyether HMDI-TPU in this invention retains the high strength of the polyester type while also possessing the hydrolysis resistance of the polyether type, resulting in anti-aging and structural stability far exceeding that of aromatic TPU.

[0125] Compared with Example 2, Comparative Example 4 showed a decrease in interfacial peel strength from 3.8 N / mm to 2.5 N / mm (a decrease of 34.2%), and a decrease in maximum withstand pressure from 4.5 MPa to 3.5 MPa (a decrease of 22.2%). The main reason for this is that while plasma pretreatment alone can increase fiber surface activity, it lacks the "chemical bond bridging" between KH-550 and the compatibilizer, failing to form a flexible transition layer. Consequently, interfacial stress concentration cannot be alleviated, and the fiber remains prone to debonding under stress. Example 2's "two-step modification" (physical etching + chemical bonding) achieves a 1+1>2 effect, overcoming the performance bottleneck of simple physical modification.

[0126] Compared to Example 2, Comparative Example 5 showed a decrease in LOI from 32.5% to 25.3% (a decrease of 22.2%), resulting in a V-1 flammability rating and flame retardant failure. The main reason is that a single APP (acid source) cannot form an expanded char layer; relying solely on acidic gas for flame retardancy is extremely inefficient. Example 2's "APP:PER:MEL=3.5:1.2:1" utilizes the synergistic effect of acid-catalyzed carbonization and gas source expansion to construct a dense char layer that blocks heat / oxygen, achieving "high flame retardancy + virtually no loss of mechanical properties," overcoming the technical bottleneck of traditional additive flame retardants where "improved flame retardancy inevitably leads to decreased mechanical properties."

[0127] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe the various possible combinations.

[0128] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A composite tube material for high-pressure air ribs, characterized in that, By weight, it includes the following components: 70-85 parts of alicyclic isocyanate modified thermoplastic polyurethane elastomer, 18-25 parts of modified reinforcing fiber, 4-6 parts of interface compatibilizer, 2-4 parts of composite anti-aging system, 1-3 parts of nano reinforcing agent, 5-15 parts of composite flame retardant system, 1-2 parts of processing aid, and 10-45 parts of solvent. The alicyclic isocyanate modified thermoplastic polyurethane elastomer is a mixture of HMDI-based polyester TPU and HMDI-based polyether TPU, with a weight ratio of (3-4):

1. The HMDI-based polyester TPU is sourced from Huntsman Polyurethanes (Shanghai) Co., Ltd., and its model number is S6440. The HMDI-based polyether TPU is sourced from Huntsman Polyurethanes (Shanghai) Co., Ltd., and its model number is A92P4207. The modified reinforcing fiber is a glass fiber or aramid fiber that has been pretreated with low-temperature plasma and then coated with a composite surface by an aminosilane coupling agent and part of the interface compatibilizer; the low-temperature plasma treatment power is 300-500W and the treatment time is 2-5min. The interface compatibilizer is a polyurethane prepolymer that combines isocyanate groups and long flexible chains. The nano-reinforcing agent is stearic acid-modified nano-silica; The composite flame retardant system is a phosphorus-nitrogen-based halogen-free intumescent flame retardant, which is composed of an acid source, a carbon source and a gas source, with a weight ratio of (3-4):(1-1.5):

1. The acid source is ammonium polyphosphate, the carbon source is pentaerythritol, and the gas source is melamine.

2. The composite tube material for high-pressure air ribs according to claim 1, characterized in that, Before being added, the nano-reinforcing agent is first formulated with some processing aids to form a pre-dispersed slurry with a solid content of 10%-20%, and then subjected to ultrasonic treatment with a power of 500-1000W for 10-30 minutes.

3. The composite tube material for high-pressure air ribs according to claim 1, characterized in that, The composite anti-aging system is a mixture of hindered phenolic antioxidants, phosphite antioxidants and benzotriazole UV absorbers, with a weight ratio of 1:(1-1.5):(0.8-1.2).

4. A method for preparing a composite tube material for high-pressure air ribs according to any one of claims 1-3, characterized in that, Includes the following steps: The nano-reinforcing agent is mixed with some processing aids and solvents in a certain proportion, and ultrasonically treated to prepare a nano-predispersed slurry. Then, it is concentrated and dried to obtain a nano-composite masterbatch. First, the reinforcing fiber is subjected to low-temperature plasma treatment, and then it is immersed in a mixed solution composed of an aminosilane coupling agent, an interface compatibilizer accounting for 30%-50% of the total weight of the interface compatibilizer, and an ethanol aqueous solution. The mixture is reacted at 70-85°C for 2-4 hours. Then, the precipitate is collected by centrifugation and dried to obtain the modified reinforcing fiber. According to the formula, the alicyclic isocyanate modified thermoplastic polyurethane elastomer, nanocomposite masterbatch, modified reinforcing fiber, composite flame retardant system, composite anti-aging system, and remaining processing aids and interface compatibilizers are placed in a high-speed mixer and mixed to obtain a uniform premix. The premixed material is fed into a co-rotating parallel twin-screw extruder for melt blending, extrusion, cooling, traction, and pelletizing.

5. The method for preparing the composite tube material for high-pressure air ribs according to claim 4, characterized in that, The solvent is anhydrous ethanol.