Long glass fiber reinforced polyurethane composite material as well as preparation process and application thereof

Abstract

The invention discloses a long glass fiber reinforced polyurethane composite material and a preparation process and application thereof.The long glass fiber reinforced polyurethane composite material adopts calcium ion doped zirconium-based MOF and is modified through phosphite to form a P-Br reaction layer, doped calcium ions are used for replacing part of zirconium-hydroxyl coordination sites, a non-catalytic metal center is formed, and the long glass fiber reinforced polyurethane composite material is obtained. According to the present invention, the aromatic halide coupling and cyclization reaction tendency of the bromination system during the combustion process is weakened, the material can efficiently capture the bromine free radical in the gas phase during the combustion, and the rapid chemical reaction is performed on the P-H bond in the phosphite group and the bromine free radical to generate the stable P-Br structure so as to improve the combustion stability of the material; the bromine free radicals are prevented from participating in generation of toxic substances such as hydrogen bromide or bromo-dioxin, the release amount of toxic flue gas and corrosive gas in the combustion process is remarkably reduced, the safety of the composite material in a fire scene is further improved, and the composite material can meet the strict standard of building door and window materials for low smoke and low toxicity and is suitable for popularization and application. And personnel escape and rescue safety can be effectively guaranteed.

Description

Technical Field

[0001] This invention relates to the preparation of composite materials, and more particularly to a long glass fiber reinforced polyurethane composite material, its preparation process, and its applications. Background Technology

[0002] Flame retardants, such as brominated flame retardants, need to be added to long glass fiber reinforced polyurethane composites. Brominated flame retardants can rapidly release bromine free radicals with strong chain termination ability after being heated. These free radicals directly act on the high-energy free radicals in the flame zone, inhibiting the combustion chain reaction in a very short time. This effectively suppresses the flame spread rate, reduces the heat release rate, and reduces the continuous thermal shock of the flame to the door and window structure. At the same time, the long glass fiber reinforcement system gives the material excellent load-bearing capacity and dimensional stability, enabling it to bear the building load in door and window frames, load-bearing beams, and other parts, while also providing rapid fire protection in the early stages of a fire. Compared with halogen-free flame retardant systems that rely on later expansion, it can better meet the strict requirements of building doors and windows for "early flame suppression, structural stability, and prevention of fire spread".

[0003] During combustion, bromine compounds decompose and release bromine free radicals (Br·), which capture high-energy H· and HO· free radicals in the combustion chain reaction, thus interrupting combustion. This is a "sacrificial" chemical process, usually accompanied by the production of large amounts of smoke and potentially toxic gases. In fires, the main cause of injury or death is often the inhalation of toxic fumes rather than direct burns. However, in real fire scenarios, bromine flame retardant materials may release high concentrations of highly toxic and corrosive gases such as hydrogen bromide, brominated dioxins, and brominated furans, threatening human life and fire rescue. Furthermore, in the early and later stages of a fire, the temperature may be low, leading to incomplete combustion. When bromine-containing organic compounds undergo incomplete combustion at low temperatures (200-450℃), under the catalysis of oxygen and metal ions (such as copper, commonly found in electrical wires), they readily generate brominated dioxins and brominated furans through the "Ullmann reaction" and "cyclization reaction."

[0004] Therefore, it is necessary to design a method for preparing long glass fiber reinforced polyurethane composites that retains the gas-phase flame-retardant advantages of bromine-based flame retardants and can solve the problem of generating other gases and toxic gases during combustion. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a long glass fiber reinforced polyurethane composite material, its preparation process, and its application.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: a preparation process for long glass fiber reinforced polyurethane composite materials, comprising the following steps:

[0007] Step S1: The zirconium source and the organic ligand are subjected to a solvothermal reaction in a solvent system, and an alkaline earth metal salt solution containing calcium ions is added to obtain a calcium ion-doped zirconium-based MOF.

[0008] Step S2: Disperse the zirconium-based MOF in ethanol, add phosphonite groups for modification, and form a P-Br reaction layer on the surface that is chemically bonded to bromine free radicals to obtain the modified zirconium-based MOF;

[0009] Step S3: Mix the long glass fiber, polyurethane, brominated flame retardant and the modified zirconium-based MOF masterbatch obtained in step S2 in a high shear mixer to obtain a mixture.

[0010] Step S4: The mixture is continuously drawn and cured at a mold temperature of 45-70℃ through a pultrusion molding process to obtain a long glass fiber reinforced polyurethane composite profile.

[0011] Step S5: The composite profile is post-cured at 80-100℃ for 1.5-3 hours to enrich the zirconium-based MOF in the 100-300μm region at the outer edge of the profile, forming a functional gradient distribution.

[0012] In a preferred embodiment of the present invention, in step S1, the zirconium source is zirconium tetrachloride, the organic ligand is terephthalic acid, the solvent is N,N-dimethylformamide, and the alkaline earth metal salt solution containing calcium ions is calcium nitrate tetrahydrate.

[0013] In the solvothermal reaction, glacial acetic acid needs to be added to regulate the reaction. The ratio of zirconium tetrachloride: terephthalic acid: glacial acetic acid: water is 1:1-1.5:20-60:6-12.

[0014] In a preferred embodiment of the present invention, in step S1, calcium ions are doped relative to Zr at a molar ratio of 0.3 to 1.5 mol%, the reaction temperature is 120 to 150 °C, and the reaction time is 8 to 24 h, to obtain calcium ion-doped zirconium-based MOF.

[0015] In a preferred embodiment of the present invention, in step S2, the silane coupling agent containing phosphonates is diethylphosphonopropyltriethoxysilane, and the amount added is 5-30 wt% of the mass of the zirconium-based MOF. The reaction is carried out in an ethanol solvent in the presence of a catalyst, the reaction temperature is 35-60°C, and the reaction time is 12-24 h.

[0016] In a preferred embodiment of the present invention, in step S2, the modified zirconium-based MOF is washed and vacuum dried at 45-60°C for 6-12 hours, and then vacuum activated at 100-120°C for 4-8 hours to remove residual solvent and stabilize the surface P-Br reaction layer.

[0017] In a preferred embodiment of the present invention, in step S3, the components are as follows by weight:

[0018] Long glass fibers: 20-40 parts;

[0019] Polyurethane resin: 30-50 parts;

[0020] Brominated flame retardants: 5-15 parts;

[0021] Modified zirconium-based MOF masterbatch: 1-10 parts.

[0022] In a preferred embodiment of the present invention, the brominated flame retardant is at least one of brominated polystyrene and brominated epoxy resin;

[0023] The length of the long glass fiber is 10-50 mm.

[0024] In a preferred embodiment of the present invention, in step S4, the die temperature of the pultrusion molding process is 45-70°C and the traction speed is 0.2-1.0 m / min.

[0025] A long glass fiber reinforced polyurethane composite material is prepared based on the aforementioned preparation process of a long glass fiber reinforced polyurethane composite material.

[0026] An application of a long glass fiber reinforced polyurethane composite material obtained by the aforementioned preparation process in building doors and windows.

[0027] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0028] (1) This invention provides a preparation process for a long glass fiber reinforced polyurethane composite material. It uses a calcium ion-doped zirconium-based MOF and modifies it with phosphonates to form a P-Br reaction layer. The calcium ions replace some of the zirconium-hydroxy coordination sites to form a non-catalytic metal center, which weakens the tendency of the bromination system to couple and cyclize aromatic halides during combustion. It also enables the material to efficiently capture bromine free radicals in the gas phase during combustion. The PH bond in the phosphonate group reacts rapidly with the bromine free radicals to generate a stable P-Br structure, thereby preventing bromine free radicals from participating in the generation of toxic substances such as hydrogen bromide or brominated dioxins. This significantly reduces the release of toxic smoke and corrosive gases during combustion, further improving the safety of the composite material in fire scenarios. It enables the material to meet the strict standards for low smoke and low toxicity of building door and window materials, effectively ensuring the safety of personnel escape and rescue.

[0029] (2) This invention provides a preparation process for long glass fiber reinforced polyurethane composite material. By introducing calcium ion doped zirconium-based MOF and combining pultrusion molding and post-curing process, MOF is enriched on the outer edge of the profile to form a functional gradient distribution. Calcium ions neutralize or block the catalytic activity of transition metal ions, thereby inhibiting the formation path of brominated dioxins during low-temperature incomplete combustion. At the same time, the surface-enriched MOF layer can play a barrier role in the early stage of fire, enhancing the flame retardant efficiency of the condensed phase of the material, promoting the formation of a dense carbon layer, further improving the limiting oxygen index and flame retardant rating, and ensuring the structural integrity of the material at high temperatures, thus extending its fire resistance time in building doors and windows applications.

[0030] (3) This invention provides a preparation process for long glass fiber reinforced polyurethane composite material. By modifying the surface of the phosphonate group, a P-Br reaction layer that can undergo a substitution reaction with Br is formed on the surface of the zirconium-based MOF. During combustion, bromine free radicals are actively captured and fixed into a P-Br bond structure, preventing the large-scale release of HBr gas in the later stage of combustion. Since a stable Zr-OP bond is formed between the phosphonate and the zirconium-oxygen skeleton, the phosphate residue after the reaction promotes the carbonization and polycondensation of the polyurethane matrix at high temperature, forming a dense phosphorus-rich and bromine-rich carbon layer. After combustion, it can achieve both flame retardant and smoke reduction effects, further improving the durability of flame retardant performance and the long-term safety of the material. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a three-dimensional structural diagram of a preferred embodiment of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0035] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] Long glass fiber: sourced from Chongqing International Composite Materials Co., Ltd., model 973 series, with a length of 10-50mm and a diameter of 10-13μm.

[0038] Polyurethane resin: sourced from Datong Resin Chemical Co., Ltd., model number DDPU-801.

[0039] Zirconium tetrachloride: sourced from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of ≥99.5%.

[0040] Terephthalic acid: sourced from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of ≥99.5%.

[0041] N,N-Dimethylformamide: sourced from Jiangsu Jiangyin Organic Chemical Co., Ltd., with a purity of ≥99.5%.

[0042] Glacial acetic acid: sourced from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of ≥99.5%.

[0043] Calcium nitrate tetrahydrate: sourced from Sinopharm Chemical Reagent Co., Ltd., purity ≥99%.

[0044] Diethylphosphonopropyltriethoxysilane: sourced from Nanjing Mest Chemical Co., Ltd., with a purity of ≥95%.

[0045] Brominated polystyrene (bromine-based flame retardant): sourced from Shandong Haili Chemical Co., Ltd., model HIPS-Br70 (bromine content 68–70%).

[0046] Anhydrous ethanol: sourced from Sinopharm Chemical Reagent Co., Ltd., with a purity of ≥99%.

[0047] Catalyst (stannous octoate (T-9)): sourced from Tianjin Kemeo Chemical Reagent Co., Ltd.

[0048] Nitrogen-phosphorus flame retardant (ammonium polyphosphate): sourced from Clariant Chemicals (China) Co., Ltd., model number Exolit AP422.

[0049] like Figure 1 As shown, a preparation process for a long glass fiber reinforced polyurethane composite material includes the following steps:

[0050] Step S1: The zirconium source and the organic ligand are subjected to a solvothermal reaction in a solvent system, and an alkaline earth metal salt solution containing calcium ions is added to obtain a calcium ion-doped zirconium-based MOF.

[0051] In step S1, the zirconium source is zirconium tetrachloride, the organic ligand is terephthalic acid, the solvent is N,N-dimethylformamide, and the alkaline earth metal salt solution containing calcium ions is calcium nitrate tetrahydrate.

[0052] In the solvothermal reaction, glacial acetic acid needs to be added to regulate the reaction. The ratio of zirconium tetrachloride: terephthalic acid: glacial acetic acid: water is 1:1-1.5:20-60:6-12.

[0053] In step S1, calcium ions are doped relative to Zr at a molar ratio of 0.3 to 1.5 mol%, the reaction temperature is 120 to 150 °C, and the reaction time is 8 to 24 h to obtain calcium ion-doped zirconium-based MOF.

[0054] Specifically, in this invention, zirconium tetrachloride is used as the metal source, terephthalic acid is used as the organic ligand, N,N-dimethylformamide (DMF) is used as the solvent, and calcium nitrate tetrahydrate is introduced as the alkaline earth metal ion source. Under solvothermal reaction conditions, calcium ions are stably doped into the Zr-O framework nodes through co-crystallization.

[0055] An appropriate amount of glacial acetic acid was also added to the reaction system as a nucleation regulator to control the nucleation rate and the density of pore defects.

[0056] The molar ratio of zirconium tetrachloride, terephthalic acid, glacial acetic acid, and water is controlled within the range of 1:1.0-1.5:20-60:6-12, so that the coordination assembly process can form a highly crystalline framework structure under relatively mild conditions.

[0057] During the solvothermal reaction, DMF not only provides a uniform dissolution environment, but also slowly releases some formate ions to promote the coordination reaction between zirconium ions and ligands.

[0058] In this system, calcium ions are embedded around the Zr6O4(OH)4 cluster by coordinating with Zr-OH bridging oxygen, forming partially substituted structural units.

[0059] By controlling the Ca / Zr molar ratio between 0.3 and 1.5 mol%, the integrity of the framework can be effectively maintained and appropriate coordination defects can be introduced, thereby improving the adsorption and fixation capacity of MOF for active bromine species.

[0060] When the Ca doping content is less than 0.3 mol%, there are insufficient metal sites available for reaction in the structure, which limits its bromine capture effect during combustion.

[0061] When the doping amount exceeds 1.5 mol%, excessive Ca ions will disrupt the Zr-OC coordination balance, causing the framework crystal form to collapse and reducing the specific surface area of ​​the material.

[0062] It should be noted that in undoped zirconium-based metal-organic frameworks, zirconium ion sites have strong Lewis acidity, which can easily catalyze the Ullmann coupling or cyclization reaction of bromine-containing aromatic compounds under flame conditions, thereby generating brominated dioxin-like byproducts.

[0063] Calcium ion doping, due to its lower charge density and weaker coordination bond energy, can replace some of the Zr-OH active centers and inhibit the occurrence of such coupling reactions.

[0064] On the other hand, calcium ions react with HBr generated during combustion to form CaBr2 solid phase, which can convert gaseous acidic gases into non-volatile salts, reduce flue gas corrosivity and reduce the concentration of toxic gases, thereby significantly improving the safety performance of composite materials during combustion.

[0065] Furthermore, the zirconium-based metal-organic framework formed in step S1 has a high specific surface area and nanoparticle size, and its abundant pore structure provides ideal reaction sites for subsequent surface modification of phosphonates.

[0066] The micro-defect distribution induced by calcium doping further enhances the reactivity of the material surface, allowing the phosphonate-silane coupling reaction to proceed more fully and form a dense P-Br reaction layer.

[0067] The zirconium-based metal-organic framework obtained through this step not only possesses excellent thermal stability and structural integrity, but also provides a dual functional basis for subsequent bromine fixation reactions and carbonization catalysis at the chemical level.

[0068] Step S2: Disperse the zirconium-based MOF in ethanol, add phosphonite groups for modification, and form a P-Br reaction layer on the surface that is chemically bonded to bromine free radicals to obtain the modified zirconium-based MOF;

[0069] In step S2, the modified zirconium-based MOF is washed and vacuum dried at 45–60°C for 6–12 h, and then vacuum activated at 100–120°C for 4–8 h to remove residual solvent and stabilize the surface P-Br reaction layer.

[0070] In this invention, in step S2, the silane coupling agent containing phosphonates is diethylphosphonopropyltriethoxysilane, and the amount added is 5-30 wt% of the mass of the zirconium-based MOF. The reaction is carried out in an ethanol solvent in the presence of a catalyst, at a temperature of 35-60°C, and for a time of 12-24 h.

[0071] Specifically, the calcium ion-doped zirconium-based MOF obtained in step S1 is dispersed in anhydrous ethanol solvent, and the solid-liquid ratio is controlled at 1:10 to 1:20 to ensure that the particles are fully dispersed in the solution and the surface active sites are fully exposed.

[0072] Add diethylphosphonopropyltriethoxysilane, a silane coupling agent containing phosphonates, to the system at an amount of 5–30 wt% of the MOF mass. Stir the reaction at 35–60 °C for 12–24 h. This process can achieve slow hydrolysis and condensation of silane under the action of trace amounts of glacial acetic acid, generating intermediates with -Si-OH and -P(=O)-H activities.

[0073] The intermediate reacts further with the Zr-OH or Ca-OH bonding sites on the MOF surface to form a stable Zr-O-Si and Zr-OP covalently linked structure.

[0074] Due to the high bond energy of the Zr-O bond and the strong coordination stability of the MOF framework, the reaction can be carried out under relatively mild conditions without destroying the crystal structure or pore permeability of the material.

[0075] During the reaction, the phosphonoyl group forms Zr-OP bonds with the hydroxyl or oxygen bridge of the zirconium node, which firmly anchors the phosphonate layer to the MOF surface.

[0076] The -Si-O-Zr bonds in the silane coupling region enhance the bonding strength between the organic layer and the inorganic framework, forming a layered gradient interface structure. This structure combines chemical stability with interfacial flexibility, ensuring dispersibility and compatibility in subsequent composite systems.

[0077] Meanwhile, the phosphonate layer introduces a strong brominophilic functional group in the chemical process, which can actively undergo substitution and addition reactions with bromine radicals or hydrobromic acid in the combustion environment to generate stable P-Br bonds and phosphonates. As a result, high-energy bromine radicals in the gas phase are effectively captured during combustion, thereby blocking their coupling reaction with aromatic structures and inhibiting the formation of brominated dioxins and brominated furans.

[0078] Meanwhile, the P-Br bond structure further promotes the char formation reaction of the polyurethane matrix at high temperatures, forming a phosphorus- and bromine-rich composite carbon layer, realizing a dynamic transformation from gas-phase flame retardancy to condensed-phase protection.

[0079] To ensure the integrity of the surface reaction layer structure, the product was washed with ethanol after the reaction to remove unreacted silane residues, and then vacuum dried at 45–60 °C for 6–12 h, followed by activation at 100–120 °C for 4–8 h to stabilize Zr-OP and Zr-O-Si bonds and remove solvent molecules adsorbed in the pores.

[0080] By introducing phosphonate groups, MOF is transformed from a single physical adsorption support into a chemically responsive reactive material. Secondly, the presence of the P-Br reaction layer endows the material with dynamic stability in the flame, enabling it to rapidly capture bromine radicals at high temperatures and transform them into stable compounds in the solid phase, thereby eliminating the regeneration cycle effect of bromine radicals.

[0081] Furthermore, the reaction layer undergoes dehydration and condensation in the later stages of combustion to form a phosphate network, which co-melts with the Zr-O-Ca structure in the MOF skeleton to form a ceramic-like carbon layer, significantly improving the thermal shielding and structural strength of the composite material.

[0082] The modified zirconium-based MOF obtained through this step not only forms a P-Si-Zr-rich multilayer reaction interface in terms of chemical composition, but also achieves multi-path adsorption and transformation of bromine radicals, HBr and aromatic intermediates in terms of function.

[0083] Specifically, by modifying the surface of the phosphonate groups, a P-Br reaction layer that can undergo a substitution reaction with Br is formed on the surface of the zirconium-based MOF. During combustion, it actively captures bromine free radicals and fixes them into a P-Br bond structure, preventing the large-scale release of HBr gas in the later stages of combustion. Due to the stable Zr-OP bond formed between the phosphonate and the zirconium-oxygen skeleton, the phosphate residue after the reaction promotes the carbonization and polycondensation of the polyurethane matrix at high temperature, forming a dense phosphorus- and bromine-rich carbon layer. After combustion, it can simultaneously achieve flame retardancy and smoke reduction, further improving the durability of flame retardancy and the long-term safety of the material.

[0084] Step S3: Mix the long glass fiber, polyurethane, brominated flame retardant and the modified zirconium-based MOF masterbatch obtained in step S2 in a high shear mixer to obtain a mixture.

[0085] The components are as follows, by weight:

[0086] Long glass fibers: 20-40 parts;

[0087] Polyurethane resin: 30-50 parts;

[0088] Brominated flame retardants: 5-15 parts;

[0089] Modified zirconium-based MOF masterbatch: 1-10 parts.

[0090] In this invention, the brominated flame retardant is at least one of brominated polystyrene and brominated epoxy resin;

[0091] The length of the long glass fiber is 10-50 mm.

[0092] To obtain uniform dispersion and stable viscosity, polyether polyol is first used as the continuous phase to prepare a solid content stable masterbatch slurry of modified zirconium-based MOF, which is then mixed sequentially with matrix resin, flame retardant and chopped glass fiber.

[0093] The masterbatch uses a polyol with the same or similar hydroxyl value as the matrix as a carrier. By utilizing the polar interaction between the surface phosphonite-silane layer and the Zr-O sites, the MOF forms a loose secondary structure in the slurry, thus avoiding hard agglomeration. This significantly reduces the mechanical energy required for the subsequent main mixing stage, while ensuring that the system viscosity is within the processable range of 0.8 to 2.5 Pa·s within the pultrusion wetting window, preventing premature initiation of the polyurethane reaction due to shear heating.

[0094] Specifically, the polyol continuous phase is first degassed under vacuum at 20–30°C to remove free water and dissolved air. Then, modified zirconium-based MOF masterbatch is added, and the mixture is subjected to high shearing using a planetary or stator-rotor type head for 1000–3000 seconds. -1 By applying the material at a shear rate of 3–10 min, a stable hydrogen bond and coordination relationship is formed between the Zr-O-Si / Zr-OP interface layer on the particle surface and the polyurethane continuous phase, thereby establishing a weak gel network of particles and resin.

[0095] The addition of brominated flame retardants at this point can further reduce the dielectric difference of the system and improve wetting and spreading. The flame retardants dispersed in the resin phase provide a uniform release source for subsequent gas-phase flame suppression.

[0096] Short-cut glass fibers with surface sizing are slowly added under continuous stirring, so that they are coated by the resin phase with minimal disturbance. This sequence can avoid the "screening effect" caused by early fiber addition, reduce the risk of MOF and flame retardant being intercepted by fiber bundles, and ensure that inorganic functional particles preferentially reside in the resin enrichment area and fiber-resin interface.

[0097] During mixing, the temperature inside the mixing tank is monitored by an online temperature probe to ensure it does not exceed 35°C, and the ambient dew point is controlled below -20°C, which can significantly reduce the probability of CO2 bubbles precipitating in the subsequent pultrusion die cavity.

[0098] To suppress the sudden increase in viscosity caused by shear heating, the aggregates are first broken up with a high shear rate, then the uniformity is maintained with a medium shear rate, and the system is briefly allowed to stand between the two stages to release microbubbles. After shearing, vacuum degassing at -0.07 to -0.095 MPa is performed for 2 to 5 minutes to allow the micron- and submicron-sized bubbles in the system to float and break up fully, thus avoiding the formation of voids in the fiber wetting path.

[0099] This step, through the synergistic regulation of interfacial chemistry and rheology, enables the modified zirconium-based MOF to preferentially reside in the resin thin layer and pore neck region surrounding the fiber.

[0100] At the microscopic level, the phosphonite group reaction layer increases the surface energy of the particles and forms secondary bonds with the amino, hydroxyl or epoxy active groups in the glass fiber adhesive, constructing a bridging path between the fiber, particles and resin, thereby improving the interfacial shear strength and inhibiting interfacial debonding at high temperatures.

[0101] At the macroscopic level, the bromine free radicals released in the gas phase are more easily captured and solidified into non-volatile species by the P-Br reaction layer near the material surface and fiber coating layer. At the same time, the weak network formed between particles through resin segments can induce oriented carbonization when heated, promoting the continuous and dense composite carbon band to adhere to the fiber, significantly inhibiting the rapid propagation of cracks in the fiber gaps.

[0102] Step S4: The mixture is continuously drawn and cured at a mold temperature of 45-70℃ through a pultrusion molding process to obtain a long glass fiber reinforced polyurethane composite profile.

[0103] Step S5: The composite profile is post-cured at 80-100℃ for 1.5-3 hours to enrich the zirconium-based MOF in the 100-300μm region at the outer edge of the profile, forming a functional gradient distribution.

[0104] In this invention, in step S4, the die temperature of the pultrusion molding process is 45-70°C and the traction speed is 0.2-1.0 m / min.

[0105] Specifically, the mixture is first guided by a guiding device to orient the long glass fibers so that they pass evenly through the impregnation zone and come into full contact with the polyurethane system.

[0106] The resin is continuously pultruded into a multi-temperature zone heated mold. The mold temperature gradually increases from the front zone to the rear zone and is controlled within the range of 45 to 70°C. The front temperature zone is kept at 45 to 55°C to ensure that the resin has good fluidity and wettability, so that the modified zirconium-based MOF can fully contact the fiber surface and establish a chemical bond.

[0107] The mid-temperature zone is maintained at 55-65℃. At this temperature, the isocyanate groups of the polyurethane system undergo a rapid polymerization reaction with the polyol, resulting in increased system viscosity and gradual release of exothermic reaction.

[0108] The end temperature zone is maintained at 65-70℃, which promotes the system to reach the initial solidification state and achieves stable demolding.

[0109] The traction speed is controlled between 0.2 and 1.0 m / min. The dynamic matching between the curing reaction and the heat transfer of the mold can be achieved by adjusting the speed, ensuring that the temperature difference between the curing front edge and the demolding point does not exceed 10℃, and preventing the resin reaction from being too fast, which may lead to stress concentration or residual bubbles in the mold.

[0110] During the pultrusion process, the polyurethane system gradually transforms from a linear fluid to a cross-linked network under heating. Long glass fibers are fully wetted and oriented in the flow field. Modified zirconium-based MOF particles form a stable interfacial chemical bond with polyurethane segments and the silane layer on the glass fiber surface through the Zr-O-Si and Zr-OP bonds on their surface.

[0111] This type of chemical bridging not only prevents interfacial slippage but also forms a composite bonding path of fiber-MOF-resin at the microscopic level. When exposed to external flame, this three-phase interface can act as a thermal resistance layer and stress dispersion zone, delaying local pyrolysis and improving the overall thermal stability of the material. On the other hand, the temperature gradient during pultrusion causes the MOF to form microscale aggregations along the fiber distribution during fluid flow, constituting a functional channel structure within the reinforcing layer. This structure possesses both high modulus and good thermal conductivity uniformity in the longitudinal tensile direction, laying a spatial foundation for subsequent gradient curing and surface functional enrichment.

[0112] After molding, the material proceeds to step S5 for post-curing treatment to further improve the crosslinking density and surface structure stability of the material.

[0113] Specifically, the post-curing process is carried out at 80-100℃ for 1.5-3 hours, mainly utilizing the secondary reaction between the residual isocyanate groups and hydroxyl groups in the polyurethane system to further extend the polymer chain and improve the network crosslinking degree.

[0114] During this process, the viscosity of the system gradually increases, and MOF particles, due to their high surface energy and relative density, undergo microscale migration under the influence of the resin viscosity gradient, gradually accumulating in the surface area of ​​the profile. When the curing reaction stabilizes, this migration process is locked by the curing network, thereby forming an enriched functional gradient band in the 100–300 μm region at the outer edge of the profile.

[0115] This functionally graded distribution layer exhibits significant thermal protection under flame conditions. The modified zirconium-based MOF enrichment region at the outer edge responds first to the flame heat flow, where the phosphonite groups can rapidly capture bromine radicals (Br·) and hydrobromic acid (HBr) in the combustion gas phase, generating stable P-Br bonds and a calcium bromide solid phase.

[0116] Meanwhile, the high proportion of inorganic components in the enriched zone promotes the ceramicization reaction on the surface, generating an inorganic carbonized layer rich in Zr-O-Ca and POC crosslinking in a short time. This layer is dense and continuous, effectively blocking oxygen and heat from entering the inner layer, thereby significantly reducing the combustion rate and flue gas release.

[0117] Because the outer MOF particle structure maintains a porous feature, local gases can diffuse and react in the micropores, further diluting the concentration of toxic gases and forming a triple synergistic flame retardant mechanism of reactive adsorption, chemical fixation, and ceramic shielding.

[0118] Inside the material, the post-curing process strengthens the chemical cross-linking of polyurethane molecular chains, making its interface with glass fiber more tightly bonded, and significantly improving the overall mechanical properties of the material.

[0119] Based on the above, the preparation steps, performance testing methods, and measured data of the embodiments are given below, which correspond one by one to verify the core mechanism and effect of the present invention.

[0120] Example 1:

[0121] Using zirconium tetrachloride as the zirconium source, terephthalic acid as the organic ligand, N,N-dimethylformamide as the solvent, and glacial acetic acid as a coordination modifier, the reaction system ratio was controlled as follows: zirconium tetrachloride: terephthalic acid: glacial acetic acid: water = 1:1:20:8. Calcium nitrate tetrahydrate was then introduced as the calcium source, allowing calcium ions to be incorporated into Zr at a molar ratio of 0.3 mol%. The reaction temperature was 150 °C, and the reaction time was 24 h, yielding calcium ion-doped zirconium-based MOFs.

[0122] The obtained zirconium-based MOF was dispersed in ethanol solvent, and then diethylphosphonopropyltriethoxysilane was added at 5 wt% of the MOF mass. The reaction was carried out at 60 °C for 12 h in the presence of a catalyst, forming a phosphonate-silane composite layer containing P-Br reaction sites on the surface of the zirconium-based MOF. This composite layer can react with bromine free radicals (Br·) generated during combustion to form stable P-Br bonds, thereby achieving chemical capture of gaseous free radicals. The modified zirconium-based MOF was then obtained by vacuum drying at 60 °C for 12 h and activation at 120 °C for 8 h to remove solvent residue.

[0123] 30 parts of long glass fiber, 45 parts of polyurethane resin, 15 parts of brominated flame retardant and 10 parts of modified MOF masterbatch obtained in step S2 were added to a high-shear mixer for dispersion and mixing. To avoid a sudden increase in viscosity due to shear heating, a two-stage shearing strategy was adopted: first, high shearing was used to break up the agglomerates, then medium speed was used to maintain uniformity, and then vacuum degassing at -0.095MPa was performed for 3 minutes.

[0124] The mixture is fed into a pultrusion mold and continuously traction-cured at a mold temperature of 70°C. The traction speed is controlled at 0.5 m / min. The shaped profile is then post-cured at 100°C for 3 hours to obtain a long glass fiber reinforced polyurethane composite material.

[0125] Example 2:

[0126] Similar to Example 1, except that calcium ions were incorporated relative to Zr at a molar ratio of 0.6 mol%.

[0127] Example 3:

[0128] Similar to Example 1, except that calcium ions were incorporated relative to Zr at a molar ratio of 0.9 mol%.

[0129] Example 4:

[0130] Similar to Example 1, except that calcium ions were incorporated relative to Zr at a molar ratio of 1.2 mol%.

[0131] Example 5:

[0132] Similar to Example 1, except that calcium ions were incorporated relative to Zr at a molar ratio of 1.5 mol%.

[0133] Example 6:

[0134] Using zirconium tetrachloride as the zirconium source, terephthalic acid as the organic ligand, N,N-dimethylformamide as the solvent, and glacial acetic acid as a coordination modifier, the reaction system ratio was controlled as follows: zirconium tetrachloride: terephthalic acid: glacial acetic acid: water = 1:1:20:8. Calcium nitrate tetrahydrate was then introduced as the calcium source, allowing calcium ions to be incorporated into Zr at a molar ratio of 1.2 mol%. The reaction temperature was 150 °C, and the reaction time was 24 h, yielding calcium ion-doped zirconium-based MOFs.

[0135] The obtained zirconium-based MOF was dispersed in ethanol solvent, and then diethylphosphonopropyltriethoxysilane was added at an amount of 10 wt% of the MOF mass. The reaction was carried out at 60 °C for 12 h in the presence of a catalyst, forming a phosphonate-silane composite layer containing P-Br reaction sites on the surface of the zirconium-based MOF. This composite layer can react with bromine free radicals (Br·) generated during combustion to form stable P-Br bonds, thereby achieving chemical capture of gaseous free radicals. The modified zirconium-based MOF was then obtained by vacuum drying at 60 °C for 12 h and activation at 120 °C for 8 h to remove solvent residue.

[0136] 30 parts of long glass fiber, 45 parts of polyurethane resin, 15 parts of brominated flame retardant and 10 parts of modified MOF masterbatch obtained in step S2 were added to a high-shear mixer for dispersion and mixing. To avoid a sudden increase in viscosity due to shear heating, a two-stage shearing strategy was adopted: first, high shearing was used to break up the agglomerates, then medium speed was used to maintain uniformity, and then vacuum degassing at -0.095MPa was performed for 3 minutes.

[0137] The mixture is fed into a pultrusion mold and continuously traction-cured at a mold temperature of 70°C. The traction speed is controlled at 0.5 m / min. The shaped profile is then post-cured at 100°C for 3 hours to obtain a long glass fiber reinforced polyurethane composite material.

[0138] Example 7:

[0139] It is largely the same as Example 6, except that the amount of diethylphosphonopropyltriethoxysilane added is 15 wt% of the mass of the MOF.

[0140] Example 8:

[0141] Similar to Example 6, except that the amount of diethylphosphonopropyltriethoxysilane added is 20 wt% of the mass of the MOF.

[0142] Example 9:

[0143] Similar to Example 6, except that the amount of diethylphosphonopropyltriethoxysilane added is 25 wt% of the mass of the MOF.

[0144] Example 10:

[0145] It is largely the same as Example 6, except that the amount of diethylphosphonopropyltriethoxysilane added is 30 wt% of the mass of the MOF.

[0146] Performance testing:

[0147] 1. Flame retardant performance test:

[0148] Limiting Oxygen Index (LOI): GB / T 2406.2-2009.

[0149] Peak heat release rate: ISO 5660-1.

[0150] 2. Flue gas toxicity analysis:

[0151] HBr release: ISO 19702, Fourier transform infrared spectroscopy is used to analyze the gas released from the combustion of materials in a tubular furnace in real time and quantify the HBr concentration.

[0152] CO / CO2 production ratio: obtained by testing with a cone calorimeter (ISO 5660-1).

[0153] 3. Residual carbon content:

[0154] The sample was heated from room temperature to 800℃ at a constant heating rate of 10℃ / min. The change in sample mass with temperature was recorded, and the residual carbon rate was calculated.

[0155] 4. Mechanical property testing:

[0156] Tensile strength: GB / T 1040.2-2006.

[0157] Bending strength: GB / T 9341-2008.

[0158] Impact strength: GB / T 1843-2008.

[0159] The performance of the long glass fiber reinforced polyurethane composites obtained in Examples 1 to 5 was tested, as shown in Table 1.

[0160] Table 1:

[0161] Limiting oxygen index (%) <![CDATA[Peak heat release rate (kW·m -2 )]]> <![CDATA[HBr release amount (mg·m -3 ).]]> <![CDATA[Dioxin toxicity equivalent (ng TEQ·m -3 )]]> Carbon residue rate at 800℃ (%) Example 1 30.2 482 501 0.214 17.4 Example 2 31.3 421 432 0.198 18.9 Example 3 32.1 367 377 0.144 20.2 Example 4 33.7 304 331 0.095 22.7 Example 5 32.4 329 342 0.112 22.4 Example 6 34.2 281 306 0.081 22.9 Example 7 34.9 267 281 0.074 23.9 Example 8 35.7 243 257 0.067 25.7 Example 9 35.1 254 272 0.071 24.8 Example 10 34.8 261 289 0.079 24.1

[0162] Table 1 shows that in Examples 1 to 5, the increased calcium ion content enhanced the performance of the long glass fiber reinforced polyurethane composite material. This is mainly because calcium ions replace some zirconium-hydroxyl coordination sites, forming non-catalytic metal centers. This weakens the tendency of aromatic halogen coupling and cyclization reactions in the bromination system during combustion, and enables the material to efficiently capture bromine radicals in the gas phase during combustion. Calcium ions neutralize or block the catalytic activity of transition metal ions, thereby inhibiting the formation pathway of brominated dioxins during low-temperature incomplete combustion. At the same time, the surface-enriched MOF layer can act as a barrier in the early stages of a fire, enhancing the condensed phase flame retardant efficiency of the material, promoting the formation of a dense char layer, and further improving the limiting oxygen index and flame retardant rating. Furthermore, the rapid chemical reaction between the PH bond in the phosphonite group and bromine radicals generates a stable P-Br structure, thereby preventing bromine radicals from participating in the formation of toxic substances such as hydrogen bromide or brominated dioxins, significantly reducing the release of toxic fumes and corrosive gases during combustion.

[0163] When the calcium ion content is too high, the coordination structure that is originally uniformly dispersed in the zirconium-based metal-organic framework will be excessively disturbed, leading to a decrease in the stability of the metal cluster and a tendency for partial disorder and pore collapse. At this time, the pyrolysis regulation ability of the MOF polyurethane matrix is ​​no longer mainly to enhance carbonization, but will introduce new degradation sites, making the material more prone to structural fracture at high temperature, thereby weakening the overall flame retardant continuity.

[0164] In Examples 6 to 10, as the amount of silane coupling agent containing phosphonates gradually increased from low to high, the surface functional layer of the zirconium-based MOF was gradually improved, forming richer P-Br reaction sites and interfacial bridging structures. On the one hand, the phosphorus-rich reaction layer can selectively react with HBr in the gas phase during combustion to generate stable P-Br bonds, thereby effectively capturing free radicals, cutting off the combustion chain reaction, reducing the release of bromine sources, and reducing the formation of dioxin-like toxic substances. On the other hand, the phosphorus-containing organosilicon structure can form multi-point crosslinks and interfacial bridging with polyurethane matrix segments and glass fiber impregnation layers, thereby improving the bonding strength and load-bearing capacity of the three-phase interface. Under the synergistic mechanism, the limiting oxygen index, char residue, and heat release peak of the material were significantly optimized, and the material showed a stable and enhanced trend in smoke suppression, toxicity reduction, and mechanical properties.

[0165] However, when the amount of silane coupling agent added exceeds a certain range, the material properties begin to decline. This is because excessive unbonded coupling agent easily forms local enrichment zones or oligomeric aggregates in the polyurethane resin, which leads to two adverse effects: First, it causes the formation of a brittle and incompatible coating layer at the interface, interfering with the effective interaction between MOF and the matrix, reducing the interfacial mechanical properties and carbon layer continuity; second, an excessively thick phosphorus-silicon coating layer may block the microporous structure of MOF, inhibiting its physical adsorption capacity for HBr and gas-solid conversion function, thus reducing its original bromine toxicity inhibition advantage. Therefore, among Examples 1 to 10, Example 8 is the optimal solution.

[0166] Comparative Example 1:

[0167] The technical solution of Example 8 is selected.

[0168] Comparative Example 2:

[0169] Comparative Example 2 is largely the same as Example 1, except that the calcium ion-doped zirconium-based MOF used is not modified with phosphonates, i.e., no P-Br reaction layer is built on its surface, and the remaining pultrusion molding and post-curing processes are consistent.

[0170] Comparative Example 3:

[0171] Comparative Example 3 is largely the same as Example 1, except that it uses a bromine-free nitrogen-phosphorus flame retardant.

[0172] Comparative Example 4:

[0173] Comparative Example 4 is largely the same as Example 1, except that a conventional brominated flame retardant system is used, and a calcium ion-doped zirconium-based MOF is not constructed, nor is it modified with phosphonates.

[0174] The performance of the long glass fiber reinforced polyurethane composite materials obtained in Example 6, Comparative Example 1, Comparative Example 2, and Comparative Example 3 was tested, and the results are shown in Table 2.

[0175] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Limiting oxygen index (%) 35.7 27.8 30.4 21.0 <![CDATA[Peak heat release rate (kW·m -2 )]]> 243 498 391 502 <![CDATA[HBr release amount (mg·m -3 )]]> 257 521 - 572 <![CDATA[Dioxin toxicity equivalent (ng TEQ·m -3 )]]> 0.067 0.259 - 0.287 Carbon residue rate at 800℃ (%) 25.7 15.7 19.6 13.4 Bending strength (MPa) 505 487 446 401 Tensile strength (MPa) 445 421 389 371 <![CDATA[Impact toughness (kJ·m -2 ).]]> 201.6 192.1 178.7 170.9

[0176] As shown in Table 2, the modified zirconium-based MOF surface used in Comparative Example 1 constructed a phosphonate-silane composite layer. This structure can selectively react with gaseous bromine free radicals in the combustion environment to form stable P-Br bonds, achieving chemical fixation of gaseous free radicals. Because the free radicals are captured in time, the combustion chain reaction is weakened, the heat release behavior is milder, and the corrosive gases and bromine-containing toxic components in the flue gas are significantly reduced. Simultaneously, the phosphonate-silane composite layer can also participate in carbon layer rearrangement in the condensed phase, promoting a denser and more stable carbon layer structure, thereby forming a more effective continuous barrier layer under thermal exposure conditions.

[0177] Conversely, although Comparative Example 2 contains a calcium-doped zirconium-based MOF, its surface lacks a phosphonate-silane composite layer, thus failing to provide an effective free radical capture interface. In this case, the MOF's role is limited to the adsorption of some HBr decomposition products, but it cannot directionally regulate the combustion chain reaction, nor can it promptly block the feedback cycle of bromine free radicals in the early stages of combustion. Consequently, it falls short of Comparative Example 1 in terms of smoke suppression, toxicity reduction, and char layer structure control. Furthermore, due to the lack of interfacial chemical reaction sites, Comparative Example 2 is also inferior to Comparative Example 1 in terms of mechanical properties and heat resistance structure retention.

[0178] Comparative Example 3 employs a nitrogen-phosphorus intumescent flame-retardant system. Its flame-retardant mechanism primarily relies on the formation of a foamed expansion layer under heating conditions to isolate air and heat radiation. Although this system does not produce bromine-containing polluting gases during combustion, the expansion layer often suffers from insufficient mechanical strength, weak carbon layer stability, and susceptibility to breakage under thermo-oxidative erosion, making it difficult to maintain long-term protective capabilities under sustained flame impact. Furthermore, due to the limited compatibility between the polarity of the intumescent flame retardant and the polyurethane resin, weak interfacial regions easily appear in the composite material regarding interfacial bonding, stress transfer, and fiber wetting, reducing the overall structural load-bearing capacity.

[0179] In contrast, Comparative Example 1, with its calcium-doped zirconium-based MOF and phosphonate-silane functional layer, not only effectively captures gaseous free radicals but also promotes the ceramization of the carbon layer in the condensed phase. This allows the protective layer to maintain its strength, continuity, and structural stability at high temperatures and forms a more stable interfacial network structure with glass fiber and polyurethane. Therefore, Comparative Example 1 combines flame retardant efficiency, structural stability, and mechanical properties, demonstrating significantly better overall performance than the nitrogen-phosphorus system that relies on expansion foaming.

[0180] Comparative Example 4 relies solely on traditional brominated flame retardants, whose flame-retardant process primarily involves releasing bromine free radicals to participate in a gas-phase chain reaction to inhibit combustion. However, this mechanism is characterized by significant sacrificial characteristics, resulting in the generation of large amounts of corrosive gases and bromine-containing toxic fumes, and these byproducts cannot be effectively solidified. Furthermore, in the absence of a solid-phase regulation mechanism, traditional brominated systems often fail to form a stable char layer structure, making the material prone to rapid pyrolysis under sustained flame exposure, resulting in high heat release peaks. The interfacial layer also lacks functional regulation, leading to limited strength of the glass fiber-resin network and generally low mechanical properties.

[0181] Comparative Example 1 not only retains the efficient gas-phase flame-retardant mechanism of brominated flame retardants, but also achieves solid-phase capture of bromine free radicals through calcium ion-doped zirconium-based MOF and phosphonate-silane composite layers, effectively weakening the gas-phase chain reaction and significantly reducing corrosive gases and toxic byproducts. The phosphorus-rich and metal-rich carbon layer network formed in the condensed phase further enhances the material's structural retention and thermal stability under flame conditions, making it significantly superior to Comparative Example 4 in terms of flame-retardant performance, char residue quality, and mechanical load-bearing capacity.

[0182] It should be noted that although the nitrogen-phosphorus system used in Comparative Example 3 produces almost no corrosive or toxic volatiles during combustion, it lacks sufficient gas-phase flame-retardant efficiency under rapid flame impact. The nitrogen-phosphorus expansion system relies on the later expansion of the char layer for protection, while brominated flame retardants can immediately enter the gas-phase inhibition reaction in the early stages of combustion, exhibiting stronger immediate suppression capabilities against high heat flux and rapidly spreading flames. Therefore, if the brominated flame retardant system is completely abandoned, the free radical concentration cannot be rapidly reduced in the early stages of the flame, leaving the material surface unprotected before the nitrogen-phosphorus system forms a complete expansion layer. The brominated system, however, can interrupt the free radical chain reaction in a very short time, preventing catastrophic thermal runaway in the initial stages.

[0183] Meanwhile, it cannot provide sufficient thermal stability and structural retention under continuous flame exposure. The expanded carbon layer is prone to cracking under the influence of wind, impact or high-temperature oxidation. However, the bromine-containing system combined with modified zirconium-based MOF can form a denser, continuous and high-strength composite carbon layer on the surface, enabling the material to maintain its structural integrity even under long-term flame exposure.

[0184] Therefore, even though nitrogen-phosphorus systems are cleaner in terms of gas toxicity, their overall flame retardant efficiency and structural retention are still insufficient to replace bromine-containing systems when facing high heat flux densities, rapid combustion propagation, or long-term fire-resistant applications. This invention addresses the smoke toxicity problem of bromine-based systems while retaining the advantages of bromine-containing systems, and the structural performance of this invention is superior to that of nitrogen-phosphorus composite materials.

[0185] A long glass fiber reinforced polyurethane composite material is prepared based on the aforementioned preparation process of a long glass fiber reinforced polyurethane composite material.

[0186] An application of a long glass fiber reinforced polyurethane composite material obtained by the aforementioned preparation process in building doors and windows.

[0187] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A preparation process for a long glass fiber reinforced polyurethane composite material, characterized in that, Includes the following steps: Step S1: The zirconium source and the organic ligand are subjected to a solvothermal reaction in a solvent system, and an alkaline earth metal salt solution containing calcium ions is added to obtain a calcium ion-doped zirconium-based MOF. Step S2: Disperse the zirconium-based MOF in ethanol, add phosphonite groups for modification, and form a P-Br reaction layer on the surface that is chemically bonded to bromine free radicals to obtain the modified zirconium-based MOF; Step S3: Mix the long glass fiber, polyurethane, brominated flame retardant and the modified zirconium-based MOF masterbatch obtained in step S2 in a high shear mixer to obtain a mixture. Step S4: The mixture is continuously drawn and cured at a mold temperature of 45-70℃ through a pultrusion molding process to obtain a long glass fiber reinforced polyurethane composite profile. Step S5: The composite profile is post-cured at 80-100℃ for 1.5-3 hours to enrich the zirconium-based MOF in the 100-300μm region at the outer edge of the profile, forming a functional gradient distribution.

2. The preparation process of a long glass fiber reinforced polyurethane composite material according to claim 1, characterized in that: In step S1, the zirconium source is zirconium tetrachloride, the organic ligand is terephthalic acid, the solvent is N,N-dimethylformamide, and the alkaline earth metal salt solution containing calcium ions is calcium nitrate tetrahydrate. In the solvothermal reaction, glacial acetic acid needs to be added to regulate the reaction. The ratio of zirconium tetrachloride: terephthalic acid: glacial acetic acid: water is 1:1-1.5:20-60:6-12.

3. The preparation process of a long glass fiber reinforced polyurethane composite material according to claim 1, characterized in that: In step S1, calcium ions are doped relative to Zr at a molar ratio of 0.3 to 1.5 mol%, the reaction temperature is 120 to 150 °C, and the reaction time is 8 to 24 h to obtain calcium ion-doped zirconium-based MOF.

4. The preparation process of a long glass fiber reinforced polyurethane composite material according to claim 1, characterized in that: In step S2, the silane coupling agent containing phosphonates is diethylphosphonopropyltriethoxysilane, and the amount added is 5-30 wt% of the mass of the zirconium-based MOF. The reaction is carried out in an ethanol solvent in the presence of a catalyst at a temperature of 35-60°C for 12-24 h.

5. The preparation process of a long glass fiber reinforced polyurethane composite material according to claim 1, characterized in that: In step S2, the modified zirconium-based MOF is washed and vacuum dried at 45–60°C for 6–12 h, and then vacuum activated at 100–120°C for 4–8 h to remove residual solvent and stabilize the surface P-Br reaction layer.

6. The preparation process of a long glass fiber reinforced polyurethane composite material according to claim 1, characterized in that: In step S3, the components are as follows by weight: Long glass fibers: 20-40 parts; Polyurethane resin: 30-50 parts; Brominated flame retardants: 5-15 parts; Modified zirconium-based MOF masterbatch: 1-10 parts.

7. The preparation process of a long glass fiber reinforced polyurethane composite material according to claim 6, characterized in that: The brominated flame retardant is at least one of brominated polystyrene and brominated epoxy resin; The length of the long glass fiber is 10-50 mm.

8. The preparation process of a long glass fiber reinforced polyurethane composite material according to claim 1, characterized in that: In step S4, the die temperature of the pultrusion molding process is 45-70℃, and the traction speed is 0.2-1.0m / min.

9. A long glass fiber reinforced polyurethane composite material, characterized in that, The long glass fiber reinforced polyurethane composite material was prepared according to any one of claims 1-8.

10. The application of a long glass fiber reinforced polyurethane composite material obtained by the preparation process of a long glass fiber reinforced polyurethane composite material according to any one of claims 1-8 in building doors and windows.

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