Carbon fiber polyester composite felt and preparation method thereof

Abstract

The invention discloses a carbon fiber polyester composite felt and a preparation method thereof, and relates to the technical field of high polymer materials, and the preparation method comprises the following steps: (1) carbon fiber directional activation; (2) in-situ grafting of sheath-core monofilaments; (3) dual-network synchronous lapping; and (4) node in-situ thermal consolidation. According to the preparation method disclosed by the invention, a carbon fiber polyester composite felt preparation system without an additional binder is constructed by sequentially implementing four steps of processes of carbon fiber directional activation, skin-core monofilament in-situ grafting, dual-network synchronous lapping and node in-situ thermal consolidation, and molecular-level synergistic combination of carbon fibers and polyester components is realized. The interface bonding strength and structural integrity of the composite felt can be remarkably improved, and meanwhile, the mechanical bearing stability of the composite felt is improved, so that the problems that in the prior art, carbon fibers and a polyester matrix are poor in interface compatibility, layering and falling are prone to occurring, and the service life is short can be solved. And the problems that the mechanical property of the composite felt is reduced, the preparation process is complicated and the environmental protection property is insufficient due to the need of adding an external binder are solved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a carbon fiber polyester composite felt and its preparation method. Background Technology

[0002] Carbon fiber polyester composite felt combines the high strength, high modulus, electrical and thermal conductivity of carbon fiber with the flexibility, easy molding, and weather resistance of polyester fiber. It can improve the overall strength and stiffness of composite materials, optimize surface smoothness, reduce defects, enhance weather resistance and UV resistance, improve resin impregnation efficiency, improve molding process, and also achieve electromagnetic shielding and thermal insulation, making it suitable for the manufacture of lightweight and high-performance components.

[0003] In existing technologies, the preparation of carbon fiber polyester composite felt suffers from poor interfacial compatibility between carbon fiber and polyester matrix, easy delamination and detachment, the need for external binders leading to decreased mechanical properties, complex preparation processes, and insufficient environmental friendliness. Furthermore, it suffers from uneven carbon fiber surface activation, poor grafting effect, significant anisotropy in the mechanical properties of the composite felt, loose structure, and the risk of fiber damage during thermal consolidation, resulting in high energy consumption. These issues affect the structural integrity, mechanical load-bearing stability, and overall performance of the composite felt. Therefore, this invention provides a carbon fiber polyester composite felt and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon fiber polyester composite felt and its preparation method. This invention constructs a preparation system without external binders through a four-step process: directional activation of carbon fibers, in-situ grafting of core and sheath monofilaments, synchronous laying of dual networks, and in-situ thermal consolidation of nodes. This achieves molecular-level bonding between carbon fibers and polyester components, significantly improving interfacial bonding strength, structural integrity, and mechanical load-bearing stability. It solves the problems of poor interfacial compatibility, easy delamination and detachment, performance degradation caused by external binders, complex processes, and insufficient environmental friendliness.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing carbon fiber polyester composite felt includes the following steps: (1) Directional activation of carbon fiber: Continuous carbon fiber is introduced into a low-power oxygen plasma gas phase activation chamber for pulsed directional activation treatment. Single active hydroxyl functional groups are introduced into the defect sites and axial active sites on the carbon fiber surface to obtain activated carbon fiber. (2) In-situ grafting of core-sheath monofilament: Activated carbon fibers are continuously fed into a closed grafting reactor. Molten comb-shaped polybutylene succinate homopolymer is uniformly loaded onto the surface of a single carbon fiber by atmospheric pressure vapor deposition. The main chain of the prepolymer is covalently anchored at one end to the single active hydroxyl functional group on the surface of the carbon fiber, thus obtaining a core-sheath composite monofilament. (3) Simultaneous double network laying: The core-sheath composite monofilament is cut to a fixed length, opened, combed, and laid in an orientation to form a main load-bearing skeleton fiber network. Simultaneously, short-cut polybutylene succinate fibers are interwoven into the pores of the main load-bearing skeleton fiber network in a multi-oriented cross-laying manner to obtain an interpenetrating double network fiber network. (4) In-situ thermal consolidation of nodes: The double network fiber mesh is passed into a low-temperature thermal consolidation oven and subjected to pressureless heat treatment in the pre-crystallization temperature range below the melting point of polybutylene succinate. This allows the comb-shaped polybutylene succinate homopolymer side chains to undergo in-situ co-crystallization and ester exchange reaction with the polybutylene succinate short chopped fibers, forming a molecular-level consolidation layer at the cross-entanglement nodes, thus obtaining a carbon fiber polyester composite felt without added adhesive.

[0006] Preferably, in step (1), the excitation frequency of the low-power oxygen plasma gas phase activation chamber is 13.56MHz, and the working environment is atmospheric pressure; The pulsed directional activation process has a power of 10W to 200W, a pulse duty cycle of 10% to 50%, an oxygen flow rate of 5mL / min to 50mL / min, and an activation time of 5min to 60min.

[0007] Preferably, in step (2), the atmospheric pressure vapor deposition method uses an ultrasonic atomizing device with a power of 200W to 800W to atomize the molten comb-shaped polybutylene succinate homopolymer at a temperature of 120℃ to 150℃ to form a molecular-level gas phase component. The grafting reaction temperature is 100℃~140℃, and the reaction time is 10min~90min.

[0008] Preferably, in step (3), the cutting length of the core-sheath composite monofilament is 3mm to 12mm; The length of polybutylene succinate chopped fibers is 3mm to 12mm, and the melting point is 115℃ to 120℃.

[0009] Preferably, in step (4), the heat treatment temperature is 95℃~109℃ and the heat treatment time is 5min~40min, and the heat treatment process does not cause the overall melting of the polybutylene succinate short fiber.

[0010] Preferably, the comb-shaped polybutylene succinate homopolymer described in step (2) has a main chain consisting of polybutylene succinate homopolymer segments with single-ended carboxyl groups and a number-average molecular weight of 3000 g / mol to 20000 g / mol. The main chain is grafted with homopolymer side chains that are completely identical to the structural units of polybutylene succinate. The number of side chains grafted on each main chain is 3 to 12, the number average molecular weight of the side chains is 1000 g / mol to 8000 g / mol, and the end of the side chains is a hydroxyl active end group.

[0011] Preferably, the continuous carbon fiber mentioned in step (1) is one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and viscose-based carbon fiber, with a linear density of 6K to 24K.

[0012] Preferably, in step (3), the mass ratio of the main load-bearing skeleton fiber network to the fiber network formed by polybutylene succinate short chopped fibers is 3:7 to 7:3.

[0013] Preferably, the mass ratio of the continuous carbon fiber in step (1) to the comb-shaped polybutylene succinate homopolymer in step (2) is 10:1 to 1:2.

[0014] Preferably, a carbon fiber polyester composite felt is prepared by a method for preparing carbon fiber polyester composite felt, comprising a main load-bearing skeleton fiber network composed of core-sheath composite monofilaments, and a polybutylene succinate chopped fiber network interspersed in the skeleton pores. At the fiber cross nodes, a molecular-level consolidation layer is formed by in-situ co-crystallization and ester exchange reaction. The carbon fiber polyester composite felt does not contain any external adhesive.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention constructs a carbon fiber-polyester composite felt preparation system without external binders by sequentially implementing four core processes: directional activation of carbon fibers, in-situ grafting of core-sheath monofilaments, synchronous double-network web laying, and in-situ thermal consolidation of nodes. This achieves molecular-level synergistic bonding between carbon fibers and polyester components. Compared with existing technologies, this significantly improves the interfacial bonding strength and structural integrity of the composite felt, while also enhancing its mechanical load-bearing stability. Therefore, it can solve the problems of poor interfacial compatibility between carbon fibers and the polyester matrix, easy delamination and detachment, and the need to add external binders, which leads to a decrease in the mechanical properties of the composite felt, as well as the complexity of the preparation process and insufficient environmental friendliness.

[0016] 2. This invention employs low-power oxygen plasma pulsed directional activation treatment to precisely introduce single active hydroxyl functional groups into defect sites and axial active sites on the carbon fiber surface. This is combined with in-situ grafting of comb-shaped polybutylene succinate homopolymer via atmospheric pressure vapor deposition. Furthermore, the molecular weight, number of side grafts, and type of active end groups of the prepolymer are strictly controlled. Compared to existing technologies, this improves the orientation and grafting efficiency of active sites on the carbon fiber surface, ensuring the uniformity of the core-sheath composite filaments. It also enhances the interfacial bonding stability between the carbon fiber and the polyester component. Therefore, it solves the problems of uneven carbon fiber surface activation and disordered active sites in existing technologies, leading to poor grafting effects, easy peeling of the core-sheath structure, and consequently affecting the overall performance consistency of the composite felt.

[0017] 3. This invention utilizes a dual-network synchronous web-laying process to form an interpenetrating structure of a main load-bearing skeleton fiber web and multi-oriented cross-linked polyester short-cut fibers. This is combined with low-temperature, pressureless, in-situ thermal consolidation below the melting point of polybutylene succinate. A molecular-level consolidation layer is formed through in-situ co-crystallization and transesterification of the prepolymer side chains and polyester short-cut fibers. Furthermore, precise control of parameters such as the web-laying mass ratio, thermal consolidation temperature, and time improves the isotropic mechanical properties and structural density of the composite felt compared to existing technologies. Simultaneously, it reduces energy consumption and process complexity during preparation, and avoids damage to fiber properties caused by high-temperature and high-pressure treatment. Therefore, it solves the problems of significant anisotropy in the mechanical properties of composite felts, loose structure, and the high energy consumption and easy damage to fiber structure caused by thermal consolidation processes in existing technologies. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention have been clearly and completely described. 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.

[0019] The method for preparing carbon fiber polyester composite felt provided by the present invention includes the following core steps: (1) Directional activation of carbon fiber: Continuous carbon fiber is introduced into a low-power oxygen plasma gas phase activation chamber with an excitation frequency of 13.56MHz and pulsed directional activation is performed under normal pressure. Through intermittent pulse discharge, only the defect sites and axial active sites on the carbon fiber surface are selectively activated in a non-etching manner without damaging the graphite layer structure of the carbon fiber body. Single active hydroxyl functional groups are introduced into the defect sites and axial active sites on the carbon fiber surface to obtain activated carbon fiber. (2) In-situ grafting of core-sheath monofilament: Activated carbon fibers are continuously fed into a closed grafting reactor. Molten comb-shaped polybutylene succinate (hereinafter referred to as PBS) homopolymer is uniformly loaded onto the surface of a single carbon fiber by atmospheric pressure vapor deposition. The single-end carboxyl groups of the prepolymer main chain undergo esterification reaction with the single active hydroxyl groups on the carbon fiber surface to achieve single-end covalent anchoring and obtain core-sheath composite monofilament. (3) Simultaneous double network laying: The core-sheath composite monofilament is cut to a fixed length, opened, combed, and laid in an orientation to form a continuous and interconnected main load-bearing skeleton fiber network. Simultaneously, PBS short-cut fibers are interwoven into the pores of the main load-bearing skeleton fiber network in a multi-oriented cross-laying manner to obtain an interpenetrating double network fiber network. (4) In-situ thermal consolidation of nodes: The double network fiber network is passed into a low-temperature thermal consolidation oven and subjected to pressureless heat treatment in the pre-crystallization temperature range below the melting point of PBS. This causes the side chains of the comb-shaped PBS homopolymer to undergo in-situ co-crystallization and transesterification reaction with the PBS short-cut fibers, forming a molecular-level consolidation layer at the fiber cross-entanglement nodes, thus obtaining a carbon fiber polyester composite felt without external binders. The absence of external binders in this invention means that no foreign resins, emulsions, or additives that are not homologous to the PBS matrix and only serve as binders are added. The comb-shaped PBS homopolymer is homologous to the matrix and is not an external binder.

[0020] In some embodiments, the processing power of pulsed directional activation in step (1) is 10W to 200W, the pulse duty cycle is 10% to 50%, the oxygen flow rate is 5mL / min to 50mL / min, and the activation time is 5min to 60min.

[0021] In some embodiments, in step (2), the atmospheric pressure vapor deposition method uses an ultrasonic atomizing device with a power of 200W to 800W to atomize the molten comb-shaped PBS homopolymer at a temperature of 120℃ to 150℃ to form a molecular-level gas phase component. The deposition carrier gas is an inert gas, including but not limited to nitrogen and argon, preferably high-purity nitrogen, and the carrier gas flow rate is 100mL / min to 500mL / min. The grafting reaction temperature is 100℃ to 140℃, the reaction time is 10min to 90min, and the reaction environment is protected by atmospheric pressure inert gas.

[0022] In some embodiments, the cutting length of the core-sheath composite monofilament in step (3) is 3mm to 12mm; the length of the PBS short-cut fiber is 3mm to 12mm, and the melting point is 115℃ to 120℃.

[0023] In some embodiments, the pre-crystallization temperature range in step (4) is the temperature range of 5°C to 20°C below the melting point of PBS as determined by differential scanning calorimetry (DSC) at a heating rate of 10°C / min; the heat treatment temperature is 95°C to 109°C, the heating rate is 2°C / min to 5°C / min, the heat treatment time is 5 min to 40 min, and the heat treatment process is carried out under normal pressure inert gas protection to prevent the overall melting of PBS chopped fibers.

[0024] In some embodiments, the comb-shaped PBS homopolymer in step (2) has a main chain consisting of a single-ended carboxyl-terminated homopolymer segment of PBS with a number-average molecular weight of 3000 g / mol to 20000 g / mol; the main chain is grafted with homopolymer side chains that are completely identical to the PBS structural units, and each main chain has 3 to 12 side chains with a number-average molecular weight of 1000 g / mol to 8000 g / mol, and the side chains are hydroxyl active end groups.

[0025] In some embodiments, the continuous carbon fiber in step (1) is one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and viscose-based carbon fiber, with a linear density of 6K to 24K.

[0026] In some embodiments, the mass ratio of the main load-bearing skeleton fiber network to the fiber network formed by the PBS short-cut fibers in step (3) is 3:7 to 7:3.

[0027] In some embodiments, the mass ratio of the continuous carbon fiber in step (1) to the comb-shaped PBS homopolymer in step (2) is 10:1 to 1:2.

[0028] In some embodiments, a carbon fiber polyester composite felt is prepared by the above preparation method; the composite felt has an interpenetrating double network structure, including a main load-bearing skeleton fiber network formed by oriented core-sheath composite monofilaments, and a secondary fiber network formed by PBS short-cut fibers interspersed in the skeleton pores; the fiber cross nodes are molecular-level consolidation layers formed by in-situ co-crystallization and ester exchange reaction, with no external adhesives or organic solvent residues throughout the process.

[0029] In some embodiments, the carbon fiber polyester composite felt has a porosity of ≥80%, a tensile breaking strength that is ≥100% higher than that of conventional PBS needle-punched felt of the same weight, a trapezoidal tear strength that is ≥250% higher, a final aerobic biodegradation rate of ≥95% after 180 days of composting, and a fatigue cycle count at 50% strain that is ≥300% higher than that of conventional PBS needle-punched felt.

[0030] The core raw material of this invention, the comb-shaped PBS homopolymer, is prepared by melt polycondensation-ester exchange branching method, without any external copolymerization units, and is completely homologous to the PBS matrix resin. The specific preparation steps are as follows: Synthesis of a single-carboxyl-terminated PBS backbone: Succinic acid and 1,4-butanediol were added to a reactor at a molar ratio of 1:1.1. Tetrabutyl titanate (0.08% molar amount of succinic acid) was added as a catalyst. The reactor was protected with high-purity nitrogen and heated to 160℃ for 2 hours for isothermal esterification. The temperature was then increased to 220℃, and n-butanol (0.3%–1.0% molar amount of succinic acid) was added as a monofunctional end-capping agent. Melt polycondensation was carried out under a vacuum of ≤100 Pa for 3–6 hours. The reactor was then cooled and discharged to obtain a single-carboxyl-terminated linear PBS backbone. The number-average molecular weight of the backbone could be controlled to be 3000 g / mol–20000 g / mol by adjusting the polycondensation time. Synthesis of hydroxyl-terminated PBS side chains: Succinic acid and 1,4-butanediol were added to a reactor at a molar ratio of 1:1.3, and tetrabutyl titanate catalyst (0.05% molar amount of succinic acid) was added. Esterification was carried out at 160℃ for 2 hours under high-purity nitrogen protection, followed by polycondensation at 220℃ under a vacuum of ≤100Pa for 1-3 hours. The mixture was then cooled and discharged to obtain hydroxyl-terminated PBS side chains. The number-average molecular weight of the side chains could be controlled from 1000 g / mol to 8000 g / mol by adjusting the polycondensation time. Comb-shaped prepolymer branching reaction: The above-mentioned single-end carboxyl-terminated PBS main chain and hydroxyl-terminated PBS side chain were added to the reactor at a molar ratio of 1:3 to 1:12. 0.05% by weight of tetrabutyl titanate catalyst was added to the main chain. Under high-purity nitrogen protection, the temperature was raised to 180℃ and transesterification branching reaction was carried out at atmospheric pressure for 2 to 4 hours. The mixture was then cooled and discharged. After precipitation three times with anhydrous ethanol and vacuum drying at 40℃ for 24 hours, a comb-shaped PBS homopolymer with single-end carboxyl-terminated main chain and hydroxyl-terminated side chain was obtained. The number of side branches on each main chain was 3 to 12.

[0031] Verification of single active hydroxyl functional groups: The elemental composition and functional group content of the carbon fiber surface were determined using a Thermo Scientific K-Alpha X-ray photoelectron spectroscopy (XPS) instrument. Test conditions: AlKα rays, energy 1486.6 eV, test vacuum ≤ 5 × 10⁻⁶. -10 mbar; the content of hydroxyl functional groups was calculated by fitting the C1s peak and combining the area ratio of the C-OH characteristic peak at 286.3 eV; the selective introduction of single active hydroxyl groups was verified by the areal density test of hydroxyl functional groups, and the areal density of single active hydroxyl groups was controlled at 0.5 to 1.2 per nm², with no polyhydroxyl aggregation sites.

[0032] Single-end covalent anchoring verification: The characteristic peak changes of carbon fibers before and after grafting were tested using a Nicoleti S50 Fourier transform infrared spectrometer, and the results were obtained through a 1730 cm⁻¹ spectroscopy. -1 The appearance of the characteristic peak of the ester group at the grafting site verifies the esterification reaction and the formation of covalent bonds; the change in molecular weight of the prepolymer before and after the grafting reaction is tested by gel permeation chromatography to verify that it is single-end anchoring rather than multi-point grafting; combined with the interfacial shear strength data of the single fiber pull-out test, the interfacial bonding effect is quantitatively verified.

[0033] Verification of in-situ co-crystallization and transesterification: The changes in melting and crystallization peaks of the samples before and after thermal solidification were measured using a TAQ2000 differential scanning calorimeter. The in-situ co-crystallization behavior was verified by observing the shift in crystallization temperature to higher temperatures and the increase in crystallinity. FT-IR was used to measure the crystals at 1730 cm⁻¹. -1The shift of the characteristic peak of the ester group was used to verify the transesterification reaction; the morphology of the fiber cross nodes was observed using a Zeiss Sigma 300 scanning electron microscope to verify that the nodes are a continuous molecular-level consolidation layer without fiber peeling gaps.

[0034] Verification of no added binder: Thermogravimetric analysis was used to test the thermal decomposition curve of the sample. Only the characteristic decomposition peaks of PBS and carbon fiber appeared, and there were no decomposition peaks of external binder, thus verifying that no external binder was added.

[0035] General raw materials: Polyacrylonitrile-based / asphalt-based / viscose-based continuous carbon fibers are commercially available general grade with tensile strength ≥3.5GPa; PBS chopped fibers are commercially available industrial grade with melting point 110℃~120℃ and melt flow rate 15g / 10min (190℃ / 2.16kg); all other chemical reagents are commercially available analytical grade. General equipment: Low-power oxygen plasma gas phase activation chamber, closed grafting reactor, ultrasonic atomization device, opening machine, carding machine, cross-laying machine, and low-temperature heat consolidation oven are all general industrial equipment in the nonwoven materials industry, with no special customization requirements.

[0036] The following embodiments fully cover all the technical features and core parameter ranges of the claims of this invention. All embodiments fall within the protection scope of the claims of this invention. All process steps are carried out online continuously, without organic solvents, offline processing, or external binders.

[0037] Example 1: This example is the basic optimal solution, and the specific process steps are as follows: (1) Directional activation of carbon fiber: 12K polyacrylonitrile-based continuous carbon fiber was introduced into a low-power oxygen plasma gas phase activation chamber with an excitation frequency of 13.56MHz. Pulsed directional activation was performed under normal pressure with a processing power of 200W, a pulse duty cycle of 30%, an oxygen flow rate of 50mL / min, and an activation time of 30min. XPS characterization showed that the surface density of hydroxyl functional groups on the carbon fiber surface was 0.8 groups / nm², and the proportion of single hydroxyl groups was ≥92%, thus achieving the selective introduction of single active hydroxyl functional groups and obtaining activated carbon fiber. (2) In-situ grafting of core-sheath monofilaments: Activated carbon fibers were continuously fed into a closed grafting reactor. Atmospheric pressure vapor deposition was used, and a 400W ultrasonic atomizing device was used to atomize molten comb-shaped PBS homopolymer at 130℃ to form a molecular-level gas phase component. High-purity nitrogen was used as the carrier gas at a flow rate of 300 mL / min, and the component was uniformly loaded onto the surface of a single carbon fiber. The mass ratio of continuous carbon fiber to prepolymer was 5:1. The number-average molecular weight of the prepolymer main chain was 8000 g / mol, and each main chain had 6 side chains with a number-average molecular weight of 3000 g / mol. The grafting reaction temperature was 120℃, the reaction time was 40 min, and atmospheric pressure nitrogen protection was used. The prepolymer main chain and the single active hydroxyl group on the carbon fiber surface underwent single-end covalent anchoring. FT-IR characterization showed that the 1730 cm⁻¹… -1 A distinct ester group characteristic peak appeared at the point, verifying the formation of covalent bonds and obtaining a core-shell composite monofilament. (3) Double network synchronous web laying: The core-sheath composite monofilament is cut into 6mm lengths online, and after opening and combing, it is laid in an orientation to form a main load-bearing skeleton fiber web. At the same time, 6mm PBS short-cut fibers (melting point 114℃) are interwoven into the pores of the main load-bearing skeleton fiber web in a multi-oriented cross-laying manner. The mass ratio of the fiber web formed by the main load-bearing skeleton fiber web and the PBS short-cut fibers is 4:6, and an interpenetrating double network fiber web with an areal density of 200g / ㎡ is obtained. (4) In-situ thermal consolidation of nodes: The double-network fiber mesh was introduced into a low-temperature thermal consolidation oven online, protected by nitrogen at normal pressure, with a heating rate of 3℃ / min, and subjected to pressureless heat treatment at 98℃ (16℃ below the melting point of PBS, which meets the requirements of the pre-crystallization temperature range) for 20 min; DSC characterization showed that the crystallinity of the sample increased by 12% compared with that before thermal consolidation. SEM observation showed that a continuous molecular-level consolidation layer was formed at the fiber cross nodes without peeling gaps, verifying that the in-situ co-crystallization and ester exchange reaction were completed, and carbon fiber polyester composite felt without external adhesive was obtained.

[0038] Example 2: The only difference between this example and Example 1 is that in step (1), the processing power of pulsed directional activation is 10W, the pulse duty cycle is 10%, the oxygen flow rate is 5mL / min, and the activation time is 5min. The remaining process steps and parameters are completely consistent with Example 1.

[0039] Example 3. The only difference between this example and Example 1 is that in step (1), the processing power of pulsed directional activation is 800W, the pulse duty cycle is 50%, the oxygen flow rate is 50mL / min, and the activation time is 60min. The remaining process steps and parameters are completely consistent with Example 1.

[0040] Example 4. The only difference between this example and Example 1 is that in step (2), the ultrasonic atomizing device has a power of 200W, the prepolymer melting temperature is 120℃, the grafting reaction temperature is 100℃, and the reaction time is 10min. The remaining process steps and parameters are completely consistent with Example 1.

[0041] Example 5. The only difference between this example and Example 1 is that in step (2), the ultrasonic atomizing device has a power of 800W, the prepolymer melting temperature is 150℃, the grafting reaction temperature is 140℃, and the reaction time is 90min. The remaining process steps and parameters are completely consistent with Example 1.

[0042] Example 6. The only difference between this example and Example 1 is that in step (2), the number-average molecular weight of the main chain of the comb-shaped PBS homologous prepolymer is 3000 g / mol, the number of side branches of each main chain is 3, and the number-average molecular weight of the side chains is 1000 g / mol. The remaining process steps and parameters are completely consistent with Example 1.

[0043] Example 7. The only difference between this example and Example 1 is that in step (2), the main chain of the comb-shaped PBS homologous prepolymer has a number-average molecular weight of 20,000 g / mol, each main chain has 12 side branches, and the side chain has a number-average molecular weight of 8,000 g / mol. The remaining process steps and parameters are completely consistent with Example 1.

[0044] Example 8: The only difference between this example and Example 1 is that in step (4), the heat treatment temperature is 95°C and the heat treatment time is 5 min. The remaining process steps and parameters are completely consistent with Example 1.

[0045] Example 9: The only difference between this example and Example 1 is that in step (4), the heat treatment temperature is 109°C and the heat treatment time is 40 min. The remaining process steps and parameters are completely consistent with Example 1.

[0046] Example 10 differs from Example 1 only in that: in step (2), the mass ratio of continuous carbon fiber to comb-shaped PBS homopolymer is 10:1; in step (3), the mass ratio of the main load-bearing skeleton fiber network to the fiber network formed by PBS short-cut fibers is 3:7. The remaining process steps and parameters are completely consistent with Example 1.

[0047] Example 11. The only difference between this example and Example 1 is that the mass ratio of continuous carbon fiber to comb-shaped PBS homopolymer in step (2) is 1:2; the mass ratio of the main load-bearing skeleton fiber network to the fiber network formed by PBS short-cut fibers in step (3) is 7:3. The remaining process steps and parameters are completely consistent with Example 1.

[0048] Example 12. The only difference between this example and Example 1 is that in step (1), the continuous carbon fiber is 12K viscose-based carbon fiber, and the other process steps and parameters are completely consistent with Example 1.

[0049] Example 13 differs from Example 1 only in the following aspects: Step (1) activation power 100W, pulse duty cycle 20%, activation time 20min; Step (2) ultrasonic atomization power 300W, grafting reaction temperature 110℃, reaction time 30min; prepolymer main chain molecular weight 10000g / mol, number of side chains 8, side chain molecular weight 4000g / mol; the remaining process steps and parameters are completely consistent with Example 1.

[0050] The following comparative examples all maintain a single variable difference from Example 1, and the verification purpose is clearly marked. Comparative Example 1: This comparative example reproduces the conventional preparation method of carbon fiber reinforced PBS composite needle-punched felt in the prior art. The specific steps are as follows: 12K polyacrylonitrile-based carbon fiber is cut into 6mm short fibers, refluxed with 65% concentrated nitric acid at 80℃ for 4h and surface modified with silane coupling agent KH-550. After cleaning and drying, it is uniformly blended with 6mm PBS short fibers at a mass ratio of 4:6. After opening, carding, and web laying, it is formed by needle punching with a needle punching density of 300 needles / cm². Then, it is heat-set at 120℃ to obtain 200g / ㎡ carbon fiber / PBS composite needle-punched felt.

[0051] Comparative Example 2 differs from Example 1 only in that: in step (1), the carbon fiber is refluxed at 80°C for 4 hours with 65% concentrated nitric acid and surface modified with silane coupling agent KH-550, and the pulsed directional activation process is not used; in step (2), the comb-shaped PBS homologous prepolymer in-situ grafting process is not used, and the remaining process steps and parameters are completely consistent with Example 1.

[0052] Comparative Example 3 differs from Example 1 only in that: after thermal solidification in step (4), the sample is impregnated with PBS emulsion with 10% solid content, an external binder is introduced, and the sample is dried at 60°C for 2 hours to constant weight. The remaining process steps and parameters are completely consistent with Example 1.

[0053] Comparative Example 4 differs from Example 1 only in that: step (3) does not use the dual-network synchronous web laying process. Instead, the core-sheath composite monofilament is cut and then uniformly blended with PBS short-cut fibers, followed by opening, carding, and web laying. There is no hierarchical structure of main load-bearing skeleton and secondary fiber web. The remaining process steps and parameters are completely consistent with Example 1.

[0054] Comparative Example 5 differs from Example 1 only in that: in step (2), the comb-shaped PBS homopolymer is replaced with a linear PBS prepolymer with an equal number-average molecular weight of 8000 g / mol and a single-end carboxyl-terminated structure. The remaining process steps and parameters are completely consistent with Example 1.

[0055] Comparative Example 6 differs from Example 1 only in that the carbon fiber was not subjected to any surface activation or grafting modification, and was directly cut and then blended with PBS chopped fibers for needle punching. The remaining process steps and parameters are completely consistent with Example 1.

[0056] Performance Testing: Performance tests were conducted on the carbon fiber-polyester composite felts treated in the examples and comparative examples. All test samples had a uniform areal density of 200 g / m². Before testing, all samples were conditioned for 24 hours in a standard atmospheric environment at 23°C and 50% relative humidity. All tests were conducted under the aforementioned standard atmospheric environment. Five parallel samples were used for each test item, and the relative standard deviation of the parallel sample test results was ≤5%. The arithmetic mean was taken as the final test result. All performance tests adopted currently valid national standards, as detailed below: Tensile breaking strength: GB / T3923.1-2013 "Textiles - Tensile properties of fabrics - Part 1: Determination of breaking strength and elongation at break (strip method)", strip width 50mm, spacing length 200mm, tensile speed 100mm / min; Trapezoidal tear strength: GB / T3917.3-2009 "Textiles - Tear properties of fabrics - Part 3: Determination of tear strength of trapezoidal specimens", specimen size 75mm×150mm, cut length 20mm, tensile speed 100mm / min; Porosity: GB / T24218.15-2018 "Textiles - Nonwovens - Test Methods - Part 15: Determination of Porosity", tested using the gas displacement method; 180-day compost biodegradation rate: GB / T19277.1-2011 "Determination of final aerobic biodegradation capacity of materials under controlled composting conditions by means of determination of carbon dioxide released - Part 1: General method", test temperature 58℃±2℃, inoculum is mature compost of municipal solid waste with a maturity of ≥80%, compost moisture content 50%±5%, pH value 7.0~8.0, forced aeration rate 0.05L / min・L, test period 180 days; Interfacial shear strength: GB / T35466-2017 "Test method for single fiber pull-out of fiber reinforced plastic composites", the matrix is ​​PBS resin of the same grade as PBS short chopped fiber, the sample embedding length is 50μm, the curing temperature is 120℃, the curing time is 30min, and the loading rate is 0.5mm / min; Fatigue cycle count: GB / T24218.19-2019 "Textiles - Test methods for nonwoven fabrics - Part 19: Determination of reciprocating tensile fatigue properties", constant strain 50%, tensile frequency 20 times / min, record the number of cycles when the specimen fails.

[0057] The obtained test data are recorded in Table 1 below: Performance test results show that Example 1 exhibits excellent performance in all aspects, indicating that under these process parameters, the synergistic effect of carbon fiber directional activation, in-situ grafting of core-sheath monofilaments, simultaneous double-network laying, and in-situ thermal consolidation of nodes can effectively improve the interfacial bonding force between carbon fiber and PBS matrix, taking into account the mechanical properties, biodegradability, and porosity of the material, thus verifying the feasibility and superiority of the basic process of this invention.

[0058] Example 2, using lower activation power, pulse duty cycle, oxygen flow rate, and shorter activation time, still achieved good product performance, indicating that the directional activation process of the present invention remains stable and effective under lower parameter conditions, and can stably achieve the selective introduction of single active hydroxyl groups, thus broadening the applicable range of process parameters.

[0059] Example 3 uses higher activation power, pulse duty cycle, oxygen flow rate and longer activation time. The product performance remains excellent, indicating that within the higher parameter range, the directional activation process of the present invention is still a non-etching selective activation that will not damage the graphite layer structure of the carbon fiber body and can still achieve the selective introduction of single active hydroxyl groups, further verifying the stability of the process.

[0060] Example 4 uses lower ultrasonic atomization power, prepolymer melting temperature, grafting reaction temperature, and shorter reaction time, yet the product performance still meets the standards. This demonstrates that the in-situ grafting process of the present invention can still achieve single-end covalent anchoring of comb-shaped PBS homopolymer and carbon fiber under lower parameter conditions, reflecting the flexibility of the process.

[0061] Example 5 employed higher ultrasonic atomization power, prepolymer melting temperature, grafting reaction temperature, and longer reaction time, resulting in outstanding product performance. This demonstrates that suitable high temperature and high power parameters can promote a more complete single-end covalent anchoring reaction between the comb-shaped PBS homopolymer and carbon fiber, further optimizing the interfacial bonding effect.

[0062] Example 6 uses a comb-shaped PBS homopolymer with lower parameters, and the product performance still meets the requirements. This shows that the comb-shaped PBS homopolymer structure design of the present invention can still play a good role in interface modification within a lower parameter range, and achieve single-end covalent anchoring with carbon fibers and subsequent co-crystallization reaction with PBS short-cut fibers.

[0063] Example 7 uses a comb-shaped PBS homopolymer with higher parameters, which significantly improves the mechanical and interfacial properties of the product. This shows that optimizing the structural parameters of the comb-shaped PBS homopolymer can further enhance its single-end covalent anchoring effect with carbon fibers and the efficiency of co-crystallization and transesterification reaction with PBS chopped fibers, thereby improving the bonding force between carbon fibers and the PBS matrix and the overall performance of the product.

[0064] Example 8 uses a lower thermal consolidation temperature and a shorter heat treatment time, and the temperature is within the pre-crystallization temperature range below the melting point of PBS. All the product properties can meet the standards, indicating that the in-situ thermal consolidation process of the present invention can still achieve in-situ co-crystallization and ester exchange reaction at the fiber cross nodes at a lower temperature and a shorter time, forming a molecular-level consolidation layer and ensuring the structural stability of the product.

[0065] Example 9 uses a higher thermal consolidation temperature and a longer heat treatment time, and the temperature does not exceed the melting point of PBS and is within the pre-crystallization temperature range. The product has stable and excellent performance, indicating that appropriate high temperature and long time treatment can promote more complete co-crystallization and transesterification reaction between the comb-shaped PBS homopolymer side chains and PBS short-cut fibers, and further improve the molecular-level consolidation effect of fiber cross nodes.

[0066] Example 10 uses a lower mass ratio of carbon fiber to comb-shaped PBS homopolymer and a lower mass ratio of main load-bearing skeleton fiber network to PBS chopped fiber network. The product still maintains good porosity and biodegradability, and meets the mechanical properties. This provides a wider range of choices for optimizing the raw material ratio and is suitable for application scenarios with high porosity requirements.

[0067] Example 11 uses a higher mass ratio of carbon fiber to comb-shaped PBS homopolymer and a higher mass ratio of main load-bearing skeleton fiber network to PBS chopped fiber network. The mechanical properties of the product are significantly improved, indicating that increasing the proportion of carbon fiber to comb-shaped PBS homopolymer can effectively enhance the main load-bearing performance of the material and is suitable for application scenarios with high mechanical performance requirements.

[0068] Example 12 uses viscose-based carbon fiber instead of polyacrylonitrile-based carbon fiber in Example 1, and the product performance remains stable. This shows that the process of the present invention is applicable to different types of continuous carbon fibers such as polyacrylonitrile-based, viscose-based, and pitch-based, which broadens the applicable range of raw materials and improves the versatility of the process.

[0069] Example 13 uses a combination of intermediate process parameters, and the product exhibits balanced and excellent performance. This demonstrates that the process parameters of the present invention are reasonably matched and can stably achieve the expected technical effects within the intermediate parameter range, providing a more easily achievable parameter reference for industrial production.

[0070] Comparative Example 1, as the closest existing technology, uses conventional 65% concentrated nitric acid reflux oxidation and silane coupling agent KH-550 modification and needle punching process, but does not use the core process of this invention. All performance aspects are significantly inferior to Example 1, indicating that the directional activation, in-situ grafting, double network laying, and in-situ thermal consolidation of this invention have significant advantages over existing technologies, and can effectively solve the performance shortcomings of existing technologies such as weak interfacial bonding, poor degradability, and insufficient mechanical properties.

[0071] Comparative Example 2 did not employ the pulsed directional activation process and in-situ grafting process of comb-shaped PBS homopolymer of the present invention. Instead, it used conventional 65% concentrated nitric acid reflux oxidation and silane coupling agent KH-550 modification method. The mechanical properties and degradability of the product were significantly reduced, which verified the key role of directional activation and in-situ grafting process in improving the interfacial bonding force between carbon fiber and PBS matrix and retaining the degradability of the material.

[0072] After the thermal solidification in step (4) of Comparative Example 3, PBS emulsion with 10% solid content was introduced as an external binder. Although the mechanical properties were improved to a certain extent, the porosity decreased significantly and the degradability decreased. This shows that the present invention does not have an external binder and can effectively balance porosity and degradability, thus solving the performance conflict problem caused by the external binder.

[0073] Comparative Example 4 did not employ the dual-network synchronous web laying process and lacked the hierarchical structure of the main load-bearing skeleton and secondary fiber web. As a result, the mechanical properties and fatigue resistance of the product decreased significantly, verifying the important significance of the dual-network structure design in improving the load-bearing performance and structural stability of materials.

[0074] Comparative Example 5 used a linear PBS prepolymer with single-ended carboxyl groups of equal number-average molecular weight to replace the comb-shaped PBS homopolymer of the present invention. The interfacial shear strength and fatigue resistance of the product decreased significantly, indicating that the branched structure of the comb-shaped prepolymer can more effectively achieve single-ended covalent anchoring with the single active hydroxyl groups on the carbon fiber surface. At the same time, it is easier to co-crystallize and transesterify with PBS short-cut fibers, thereby improving the interfacial bonding effect. This verifies the core role of the comb-shaped PBS homopolymer in the present invention.

[0075] Comparative Example 6, which did not undergo any surface activation or grafting modification of the carbon fiber, had the worst performance in all aspects, indicating that surface modification of carbon fiber is a necessary condition for improving its interfacial bonding with the PBS matrix and optimizing the overall performance of the product.

[0076] By comparing and analyzing the relevant data in the table, it can be seen that this invention, through the rational design of a carbon fiber pulsed directional activation process, optimization of the structural parameters of the comb-shaped PBS homologous prepolymer, adoption of a dual-network synchronous web laying method and in-situ thermal consolidation process at the nodes, and coordinated control of various process parameters and raw material ratios, achieves simultaneous improvement in the mechanical properties, biodegradability, porosity, and fatigue resistance of carbon fiber polyester composite felt. This effectively solves the industry pain points of existing technologies, such as weak interfacial bonding between carbon fiber and PBS matrix, conflict between reinforcement and biodegradability, contradiction between structural stability and porosity, and poor fatigue resistance. At the same time, it broadens the applicability of raw materials and process parameters, ensuring the stability and versatility of the process. Furthermore, the entire process is free of organic solvents, offline processing, and external binders, meeting the requirements of environmental protection and industrial production. Therefore, this invention indicates that the carbon fiber polyester composite felt and its preparation method provided by this invention have a broader market prospect and are more suitable for promotion.

[0077] In the description of this specification, references to terms such as "an experiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that experiment or example is included in at least one experiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same experiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more experiments or examples.

[0078] The preferred experiments disclosed above are merely illustrative of the invention. These preferred experiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these experiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing carbon fiber polyester composite felt, characterized in that, Includes the following steps: (1) Directional activation of carbon fiber: Continuous carbon fiber is introduced into a low-power oxygen plasma gas phase activation chamber for pulsed directional activation treatment. Single active hydroxyl functional groups are introduced into the defect sites and axial active sites on the carbon fiber surface to obtain activated carbon fiber. (2) In-situ grafting of core-sheath monofilament: Activated carbon fibers are continuously fed into a closed grafting reactor. Molten comb-shaped polybutylene succinate homopolymer is uniformly loaded onto the surface of a single carbon fiber by atmospheric pressure vapor deposition. The main chain of the prepolymer is covalently anchored at one end to the single active hydroxyl functional group on the surface of the carbon fiber, thus obtaining a core-sheath composite monofilament. (3) Simultaneous double network laying: The core-sheath composite monofilament is cut to a fixed length, opened, combed, and laid in an orientation to form a main load-bearing skeleton fiber network. Simultaneously, short-cut polybutylene succinate fibers are interwoven into the pores of the main load-bearing skeleton fiber network in a multi-oriented cross-laying manner to obtain an interpenetrating double network fiber network. (4) In-situ thermal consolidation of nodes: The double network fiber mesh is passed into a low-temperature thermal consolidation oven and subjected to pressureless heat treatment in the pre-crystallization temperature range below the melting point of polybutylene succinate. This allows the comb-shaped polybutylene succinate homopolymer side chains to undergo in-situ co-crystallization and ester exchange reaction with the polybutylene succinate short chopped fibers, forming a molecular-level consolidation layer at the cross-entanglement nodes, thus obtaining a carbon fiber polyester composite felt without added adhesive.

2. The method for preparing a carbon fiber polyester composite felt according to claim 1, characterized in that, In step (1), the excitation frequency of the low-power oxygen plasma gas phase activation chamber is 13.56MHz, and the working environment is atmospheric pressure; The pulsed directional activation process has a power of 10W to 200W, a pulse duty cycle of 10% to 50%, an oxygen flow rate of 5mL / min to 50mL / min, and an activation time of 5min to 60min.

3. The method for preparing a carbon fiber polyester composite felt according to claim 1, characterized in that, In step (2), the atmospheric pressure vapor deposition method uses an ultrasonic atomizing device with a power of 200W to 800W to atomize the molten comb-shaped polybutylene succinate homopolymer at a temperature of 120℃ to 150℃ to form molecular-level gas phase components. The grafting reaction temperature is 100℃~140℃, and the reaction time is 10min~90min.

4. The method for preparing a carbon fiber polyester composite felt according to claim 1, characterized in that, In step (3), the cutting length of the core-sheath composite monofilament is 3mm to 12mm; The length of polybutylene succinate chopped fibers is 3mm to 12mm, and the melting point is 115℃ to 120℃.

5. The method for preparing a carbon fiber polyester composite felt according to claim 1, characterized in that, In step (4), the heat treatment temperature is 95℃~109℃ and the heat treatment time is 5min~40min. The heat treatment process does not cause the overall melting of the polybutylene succinate short fiber.

6. The method for preparing a carbon fiber polyester composite felt according to claim 1, characterized in that, The comb-shaped polybutylene succinate homopolymer described in step (2) has a main chain consisting of polybutylene succinate homopolymer segments with single-end carboxyl groups and a number-average molecular weight of 3000 g / mol to 20000 g / mol. The main chain is grafted with homopolymer side chains that are completely identical to the structural units of polybutylene succinate. The number of side chains grafted on each main chain is 3 to 12, the number average molecular weight of the side chains is 1000 g / mol to 8000 g / mol, and the end of the side chains is a hydroxyl active end group.

7. The method for preparing a carbon fiber polyester composite felt according to claim 1, characterized in that, The continuous carbon fiber mentioned in step (1) is one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and viscose-based carbon fiber, with a linear density of 6K to 24K.

8. The method for preparing a carbon fiber polyester composite felt according to claim 1, characterized in that, In step (3), the mass ratio of the main load-bearing skeleton fiber network to the fiber network formed by polybutylene succinate short chopped fibers is 3:7 to 7:

3.

9. The method for preparing a carbon fiber polyester composite felt according to claim 1, characterized in that, The mass ratio of the continuous carbon fiber in step (1) to the comb-shaped polybutylene succinate homopolymer in step (2) is 10:1 to 1:

2.

10. A carbon fiber polyester composite felt, characterized in that, The carbon fiber polyester composite felt is prepared by the method of any one of claims 1-9, comprising a main load-bearing skeleton fiber network composed of core-sheath composite monofilaments, and a polybutylene succinate short fiber network interspersed in the skeleton pores. At the fiber cross nodes, a molecular-level consolidation layer is formed by in-situ co-crystallization and ester exchange reaction. The carbon fiber polyester composite felt does not contain any external adhesive.

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