Preparation method of aramid fiber UHMWPE (Ultra High Molecular Weight Polyethylene) composite fiber material

Abstract

The present application relates to an aramid fiber amp; the preparation method of the UHMWPE composite fiber material comprises the following steps: pulp surface pre-activation, UHMWPE fiber plasma pretreatment, UHMWPE fiber surface activation, graded dispersion and gradient hot pressing. The aramid pulp is subjected to epoxy group modification, the UHMWPE is subjected to surface amino functionalization, an amino-epoxy ring-opening reaction is initiated in the hot pressing process, a covalent bond bridged multi-stage interface structure is constructed, compared with modification with a single coupling agent, the interface shear strength is improved, and the problem that the strength is difficult to retain under the condition of low polyethylene content is solved. A four-step logic chain of pretreatment, directional modification, graded dispersion and gradient hot pressing is constructed, meanwhile, the proportion of aramid chopped fibers to pulp is increased, the tensile strength is still higher than that of pure aramid on the premise that the continuous use temperature is close to that of pure aramid, and the optimal balance of high-temperature tolerance, light weight and high strength is achieved.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and in particular to a method for preparing an aramid & UHMWPE composite fiber material. Background Technology

[0002] High-performance fiber composites, due to their advantages of being lightweight, high-strength, corrosion-resistant, and multifunctional, have become core structural materials in key fields such as aerospace, personal protective equipment, and high-end equipment manufacturing. Among them, meta-aramid chopped strand fibers, with their excellent thermal stability (continuous use temperature up to 205℃), high limiting oxygen index (LOI > 28), and characteristics such as no dripping during combustion, low smoke, and non-toxicity, occupy an important position in fireproofing, thermal insulation, and electrical insulation. Meanwhile, high-strength, high-modulus polyethylene (UHMWPE) fibers, known for their extremely low density, ultra-high tensile strength, and excellent abrasion resistance, are widely used in lightweight bulletproof and impact-resistant structural components. Combining these two materials is expected to achieve a balance between high-temperature resistance and mechanical properties, realizing functional complementarity.

[0003] However, existing technologies face significant interfacial compatibility challenges when constructing aramid / UHMWPE composite systems. The strong chemical inertness and lack of polar functional groups on the surface of UHMWPE fibers result in extremely weak interfacial adhesion between them and meta-aramid chopped fibers and the resin matrix, severely restricting effective stress transfer and hindering the synergistic reinforcement effect of the components. Simultaneously, the significant differences in physical properties between the two fibers mean that direct blending easily leads to uneven dispersion and localized agglomeration, causing fluctuations in the material's mechanical properties or even failure. Although some studies have attempted to activate the surface of UHMWPE through plasma treatment, gamma-ray irradiation, or chemical grafting, these methods generally suffer from high equipment dependence, complex processes, high costs, and the potential to damage the fiber's bulk mechanical properties, making them unsuitable for large-scale industrial production. Aramid pulp, as a high-performance reinforcing agent, possesses abundant amide functional groups on its surface that can provide hydrogen bonding sites; however, an effective solution remains to be found for using it as an "interfacial bridging agent" through a simple process to achieve synergistic reinforcement of the three components.

[0004] Chinese patent CN120389198A discloses a method for preparing an aramid-coated polyolefin battery separator, the steps of which include: (1) The polyolefin-based membrane was treated with a strong oxidizing agent to obtain a hydroxylated modified polyolefin-based membrane; (2) Dissolve the aramid resin in a solvent to obtain an aramid coating solution; (3) The aramid coating liquid is coated onto the surface of the hydroxylated modified polyolefin base film to obtain an aramid coated separator; the aramid coated separator is cured to obtain the aramid coated polyolefin battery separator.

[0005] As can be seen from the steps, the polyolefin material and the aramid material are not uniformly mixed materials, but rather a sandwich-structured composite material. The thickness of the material cannot be freely controlled, and the bonding force between the two materials is unreliable.

[0006] Chinese patent CN121043360A discloses a method for preparing an aramid long fiber reinforced thermoplastic resin-based composite material, the steps of which include: S1. Preparation of blended yarn strips: Aramid long fibers are blended with thermoplastic resin long fibers (polyethylene long fibers can be used) to obtain uniform blended yarns. S2. Preparation of fiber felt: Blended yarns are dispersed by airflow and preheated to obtain fiber mats; S3, Melt Mixing and Injection Molding: The fiber felt is sequentially fed into the first-stage pre-plasticizing mechanism and the second-stage injection mechanism for conveying and melting, and then enters the mold assembly for injection molding; The first-stage pre-plasticizing mechanism and the second-stage injection mechanism are each equipped with a screw. The fiber felt first enters the rear conveying section through the front conveying section of the first-stage pre-plasticizing mechanism, where it is preheated and melted. Then it enters the compression section of the second-stage injection mechanism, where it is mixed, compressed, and pressurized to exhaust air. Finally, it enters the metering section, where it is mixed evenly and then injection molded.

[0007] Firstly, this type of polyethylene long fiber does not have the properties of high-strength, high-modulus polyethylene. Secondly, aramid long fiber and thermoplastic resin long fiber are blended to form blended yarns, and the two are bonded by physical bonds rather than chemical bonds, so the tensile strength is not high.

[0008] Therefore, it is necessary to improve the material preparation methods to solve the above problems. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing aramid & UHMWPE composite fiber material. Using aramid pulp as a natural interface modifier, a composite fiber material and its preparation method that synergistically reinforces meta-aramid short-cut fibers and UHMWPE are achieved through simple chemical modification and gradient dispersion processes. This method improves mechanical strength while ensuring high temperature resistance, and the process is simple and controllable.

[0010] This invention achieves the above objective through the following technical solution: a method for preparing an aramid & UHMWPE composite fiber material, comprising the following steps: S1. Pre-activation of pulp surface: Deionized water is added to meta-aramid short fibers to make pulp dispersion, then silane coupling agent is added and mixed evenly. Subsequently, vacuum filtration and drying are carried out to constant weight to obtain pre-activated aramid pulp. S2, UHMWPE fiber plasma pretreatment: The dried UHMWPE fiber is pretreated with plasma to introduce oxygen-containing polar groups on its surface; S3. Surface activation of UHMWPE fibers: Mix silane coupling agent with deionized water, adjust pH to 4-5 to promote hydrolysis of silane coupling agent, and prepare modified solution; immerse UHMWPE fibers that have undergone plasma pretreatment into modified solution, remove UHMWPE fibers that have been soaked in modified solution, heat and dry to obtain activated UHMWPE fibers. S4. Grading and Dispersion: The pre-activated aramid pulp and a portion of activated UHMWPE fiber are mixed evenly at a high speed of 800–1000 r / min. Then, meta-aramid short-cut fibers and the remaining activated UHMWPE fibers are added and mixed evenly at a low speed of 500–600 r / min to obtain aramid & UHMWPE composite fiber. S5. Gradient hot pressing: Aramid & UHMWPE composite fibers are formed by a three-stage hot pressing process of pre-compression degassing, heating and pressurization, and slow cooling and depressurization to obtain aramid & UHMWPE composite fiber materials.

[0011] Specifically, before pre-activation of the aramid pulp surface, the meta-aramid chopped fibers and the UHMWPE fibers are dried separately at a temperature of 105°C for 2 hours.

[0012] Specifically, the silane coupling agent used in step S1 is KH-560 silane coupling agent, and the amount of KH-560 added is 1–5% of the mass of aramid pulp.

[0013] Specifically, the mixing temperature in step S1 is 50°C, the stirring time is 30 minutes, and the drying temperature is 80°C.

[0014] Specifically, step S2 involves placing the dried UHMWPE fiber in a low-temperature plasma treatment device, introducing air or oxygen, controlling the air pressure at 50-100Pa, the power at 80-120W, and the treatment time at 2-5 minutes.

[0015] Specifically, the silane coupling agent used in step S3 is KH-550 silane coupling agent, and the amount of KH-550 silane coupling agent added is 0.5–3% of the mass of UHMWPE fiber.

[0016] Specifically, in step S3, 0.1% glacial acetic acid is used to adjust the pH, and the stirring time is 10 minutes to promote the hydrolysis of the silane coupling agent.

[0017] Specifically, the soaking conditions in step S3 are constant temperature oscillation soaking at 40℃ for 30 minutes, and the UHMWPE fibers soaked in the modified solution are first pre-dried at 80℃ for 1 hour to remove surface free moisture, and then heated to 110℃ for 1.5 hours to obtain activated UHMWPE fibers.

[0018] Specifically, the step S4 graded dispersion operation is as follows: the pre-activated aramid pulp and 50% by mass of activated UHMWPE fiber are first mixed at 800 r / min for 3 min; the speed is increased to 1000 r / min and the mixing is continued for 5 min to obtain pulp-UHMWPE composite material; the speed is reduced to 500 r / min, meta-aramid short-cut fiber and the remaining 50% activated UHMWPE fiber are added and mixed for 4 min to obtain aramid & UHMWPE composite fiber.

[0019] Specifically, the three-stage hot-pressing process in step S5 involves forming aramid & UHMWPE composite fibers into sheets with a basis weight of 100-150 g / m². 2 The base paper is placed in a flat vulcanizing machine preheated to 80°C and pre-pressed at 4MPa for 5 minutes; then the temperature is raised to 160°C and the pressure is increased to 10MPa, and hot-pressed at constant temperature and pressure for 15 minutes; after naturally cooling to 100°C, the pressure is reduced to 2MPa and then cooled to room temperature to obtain aramid & UHMWPE composite fiber material.

[0020] The beneficial effects of the technical solution of this invention are: 1. Epoxy modification of aramid pulp and surface amino functionalization of UHMWPE are carried out to initiate an amino-epoxy ring-opening reaction during hot pressing, thereby constructing a multi-level interface structure with covalent bonds. Compared with modification by a single coupling agent, the interfacial shear strength is improved, which solves the problem of difficulty in retaining strength under low polyethylene content.

[0021] 2. This invention constructs a four-step logical chain of "pretreatment-directional modification-hierarchical dispersion-gradient hot pressing". ① Pretreatment controls the moisture content to ensure the activity of the silane coupling agent; ② directional modification avoids mutual interference of silane coupling agents; ③ hierarchical dispersion controls the mixing order according to density differences; ④ gradient hot pressing first degassing, then reacting, and then slowly cooling to reduce the internal stress of the material.

[0022] 3. The UHMWPE content has been reduced from the industry standard of 45-65% to 30-45%, while the ratio of aramid chopped fiber to pulp has been increased. Under the premise that the continuous use temperature is increased to 198-202℃ (close to pure aramid), the tensile strength is still 64.6-75.4% higher than that of pure aramid, achieving the optimal balance of "high temperature resistance - lightweight and high strength". Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments.

[0024] This invention provides a method for preparing an aramid & UHMWPE composite fiber material, comprising the following steps: S1. Raw material pretreatment: Place the meta-aramid short-cut fibers and UHMWPE fibers into a drying oven, and dry them at 105℃ for 2 hours.

[0025] Meta-aramid chopped strands and UHMWPE fibers are the main raw materials, and they readily absorb water. The molecular structure of meta-aramid chopped strands contains a large number of amide groups (-CONH-), which easily adsorb moisture from the air through hydrogen bonds. If drying is insufficient, the moisture will vaporize upon heating during processing, leading to bubbles and pinholes in the composite material, and causing a decrease in interfacial bonding. UHMWPE fiber raw material particles or the surface of nascent fibers may adsorb free water; drying prevents problems such as fiber breakage and fuzzing during melt spinning.

[0026] S2. Pre-activation of pulp surface: Deionized water is added to meta-aramid short chopped fibers to prepare a pulp dispersion with a mass concentration of 5%. Then, 1–5% of KH-560 silane coupling agent by mass of the pulp dispersion is added, and the mixture is stirred at 50°C for 30 minutes to achieve pre-activation of the pulp surface. Subsequently, the mixture is vacuum filtered and dried at 80°C to constant weight to obtain pre-activated aramid pulp.

[0027] The molecular structure of KH-560 (γ-glycidoxypropyltrimethoxysilane) is as follows: CH2(O)CHCH2O(CH2)3Si(OCH3)3 The surface of meta-aramid chopped fibers (such as Kevlar) mainly contains amide groups (-CONH-) and a small amount of carboxyl groups (-COOH) or hydroxyl groups (-OH) (generated by surface oxidation or hydrolysis). The reaction of KH-560 with the fiber surface occurs in two steps: ① Silane hydrolysis and condensation (forming a siloxane coating) -Si(OCH3)3+3H2O→-Si(OH)3+3CH3OH Condensation occurs between silanol groups: -Si-OH+HO-Si-→-Si-O-Si-+H2O Result: A cross-linked siloxane network (-Si-O-Si-) was formed on the fiber surface.

[0028] ② The reaction between organic functional groups and the fiber surface The epoxy groups of KH-560 can undergo ring-opening reactions with the amino groups (-NH2, generated by the hydrolysis of amide groups) or hydroxyl groups (-OH) on the surface of aramid fibers:

[0029] Reaction with amino groups: -NH2+CH2OCH-CH2-O-→-NH-CH2-CH(OH)-CH2-O-

[0030] Reaction with hydroxyl groups: -OH+CH2OCH-CH2-O-→-O-CH2-CH(OH)-CH2-O- Therefore, KH-560 introduces a siloxane crosslinking network and hydroxylated organic segments onto the surface of meta-aramid chopped fibers through siloxane hydrolysis condensation and epoxy ring-opening reaction, thereby improving the interfacial bonding between the fiber and the resin matrix.

[0031] S3. Plasma pretreatment of UHMWPE fibers: Place the dried UHMWPE fibers in a low-temperature plasma treatment device, introduce air or oxygen, control the air pressure at 50-100Pa, the power at 80-120W, and the treatment time at 2-5min to introduce oxygen-containing polar groups (-OH, -COOH) on the surface; after treatment, remove the fibers for later use and avoid prolonged exposure to air to maintain surface activity.

[0032] The surface of UHMWPE fibers consists of non-polar polyethylene chains (-CH2-CH2-), lacking active functional groups (such as hydroxyl and carboxyl groups) and exhibiting extremely low surface energy (approximately 31 mN / m). Therefore, they cannot directly react chemically with the silane coupling agent KH-550. Thus, oxygen-containing polar groups must first be introduced. Under the influence of plasma, oxygen atoms are inserted into the CH bonds at some positions on the carbon chains to generate hydroxyl groups (-OH), while C / C bonds in some branches break, subsequently generating carboxyl groups (-COOH). This provides modifiable sites for surface activation.

[0033] S4. Surface activation of UHMWPE fibers: Mix 0.5–3% by weight of KH-550 silane coupling agent with deionized water, add 0.1% glacial acetic acid to adjust the pH to 4–5, stir for 10 min to promote the hydrolysis of KH-550 silane coupling agent, and prepare a modified solution; immerse the pretreated UHMWPE fibers in the modified solution, and soak at 40℃ with constant temperature and shaking for 30 min to ensure that the fiber surface is fully in contact with the modified solution; take out the UHMWPE fibers soaked in the modified solution, pre-dry at 80℃ for 1 h to remove free surface moisture, and then heat to 110℃ for 1.5 h to form stable chemical bonds between the silane coupling agent KH-550 and the surface of the UHMWPE fibers, thus obtaining activated UHMWPE fibers.

[0034] The molecular structure of KH-550 (γ-aminopropyltriethoxysilane) is as follows: NH2-(CH2)3-Si-(OC2H5)3 The principle of surface activation is as follows: Silane hydrolysis and condensation form a physical coating layer KH-550's alkoxy groups hydrolyze to generate silanol groups: -Si(OC2H5)3+3H2O→-Si(OH)3+3C2H5OH If the surface contains hydroxyl groups (-OH): condensation reaction forms Si-OC covalent bonds. -Si-OH + HO-C → -Si-OC- + H2O (Residual amino group: -NH2 remains at the end of the molecular chain) If the surface contains carboxyl groups (-COOH): amidation reaction forms -CONH- bonds. -NH2+-COOH→-CONH-+H2O (Simultaneously accompanied by silanol condensation: -Si(OH)3+ HO-Si- → -Si-O-Si- + H2O)

[0035] KH-560 is used to epoxide-modify aramid pulp, and KH-550 is used to surface-functionalize UHMWPE with amino groups. During hot pressing, an amino-epoxy ring-opening reaction is initiated to construct a multi-level interface structure with covalent bonds. Compared with modification by a single coupling agent, the interfacial shear strength is improved, which solves the problem of difficulty in retaining strength under low polyethylene content.

[0036] S5. Graded dispersion: Start the high-speed mixer, first add pre-activated aramid pulp and 50% by mass of activated UHMWPE fiber, mix at 800 r / min for 3 min; increase the speed to 1000 r / min and continue mixing for 5 min to obtain pulp-UHMWPE composite material; reduce the speed to 500 r / min, add meta-aramid short-cut fiber and the remaining 50% activated UHMWPE fiber, mix for 4 min to obtain aramid & UHMWPE composite fiber.

[0037] The first stage of mixing is to use the lightweight properties of activated UHMWPE fibers to disperse the pulp. The second stage is to make the pre-activated aramid pulp evenly adhere to the surface of the activated UHMWPE fibers. The third stage is to use low-speed mixing to reduce fiber breakage, and finally form a uniformly dispersed system with meta-aramid as the skeleton and pulp-UHMWPE as the reinforcing unit.

[0038] S6. Gradient hot pressing: Aramid & UHMWPE composite fibers are formed into sheets with a basis weight of 100-150g / m². 2 The base paper is placed in a flat vulcanizing machine preheated to 80°C and pre-pressed at 4MPa for 5 minutes; then the temperature is raised to 160°C and the pressure is increased to 10MPa, and hot-pressed at constant temperature and pressure for 15 minutes; after naturally cooling to 100°C, the pressure is reduced to 2MPa and then cooled to room temperature to obtain aramid & UHMWPE composite fiber material.

[0039] Aramid & UHMWPE composite fibers are formed into aramid & UHMWPE composite fiber materials through a three-stage hot-pressing process: pre-compression degassing, heating and pressurizing, and slow cooling and depressurization. Gradient hot pressing is used to gradually expel air from the base paper and eliminate internal stress in the material. During the hot-pressing process, the hydroxylated organic segments on the surface of the meta-aramid short fibers can undergo further dehydration condensation with the three-dimensional siloxane network on the surface of the activated UHMWPE fibers, forming covalent bonds, thus resulting in a uniform material texture.

[0040] This invention constructs a four-step logical chain of "pretreatment-directional modification-hierarchical dispersion-gradient hot pressing". ① Pretreatment controls the moisture content to ensure the activity of silane coupling agents; ② directional modification avoids mutual interference of silane coupling agents; ③ hierarchical dispersion controls the mixing order according to density differences; ④ gradient hot pressing first degassing, then reacting, and then slow cooling to reduce the internal stress of the material.

[0041] Example 1: 1. Raw material pretreatment: Aramid short-cut fibers are dried with UHMWPE at 105℃ for 2 hours; 2. Pre-activation of pulp surface: Add 2g of oven-dried aramid pulp to 100g of deionized water, sonicate for 15min, add 0.06g of KH-560, stir at 50℃ for 30min, filter and dry at 80℃ to constant weight; 3. Plasma pretreatment of UHMWPE fiber: Place 4g of UHMWPE fiber in a low-temperature plasma treatment machine, introduce oxygen, pressurize at 80Pa, power at 100W, and treat for 3min; 4. Surface activation of UHMWPE fibers: Mix 0.04g KH-550 with 100g deionized water, add glacial acetic acid to adjust pH=4.5, stir for 10min; add plasma pretreated UHMWPE, shake and soak at 40℃ for 30min, pre-dry at 80℃ for 1h, and dry at 110℃ for 1.5h. 5. Grading and Dispersion: First, add KH-560 treated pulp and 2g KH-550 treated UHMWPE to the mixer. Stir at 800r / min for 3min, then increase to 1000r / min and stir for 5min. Then add 4g aramid chopped fiber and 2g KH-550 treated UHMWPE. Stir at 500r / min for 4min to obtain aramid & UHMWPE fiber blend. 6. Gradient hot pressing: The graded and dispersed aramid & UHMWPE fibers are rolled into base paper with a basis weight of 120 g / m², placed in a flat vulcanizing machine preheated to 80°C, and pre-pressed at 4 MPa for 5 min to expel air from the material; the temperature is then increased to 150°C and the pressure is increased to 10 MPa, and hot pressing is carried out at constant temperature and pressure for 15 min; after naturally cooling to 100°C, the pressure is reduced to 2 MPa, and the material is further cooled to room temperature to obtain aramid & UHMWPE composite fiber material.

[0042] Example 2: 1. Raw material pretreatment: Aramid short-cut fibers are dried with UHMWPE at 105℃ for 2 hours; 2. Surface pre-activation of pulp: Add 2g of aramid pulp to 100g of deionized water, sonicate for 15min, add 0.06g of KH-560, stir at 50℃ for 30min, filter and dry at 80℃ to constant weight; 3. Plasma pretreatment of UHMWPE fiber: Place 3g of UHMWPE fiber in a low-temperature plasma treatment machine, introduce oxygen, pressurize at 80Pa, power at 100W, and treat for 3min; 4. Surface activation of UHMWPE fibers: Mix 0.03g KH-550 with 100g deionized water, add glacial acetic acid to adjust pH=4.5, stir for 10min; add plasma pretreated UHMWPE, shake and soak at 40℃ for 30min, pre-dry at 80℃ for 1h, and dry at 110℃ for 1.5h. 5. Grading and Dispersion: First, add KH-560 treated pulp and 1.5g KH-550 treated UHMWPE to the mixer. Stir at 800r / min for 3min, then increase to 1000r / min and stir for 5min. Then add 5g aramid chopped fibers and 1.5g KH-550 treated UHMWPE. Stir at 500r / min for 4min to obtain aramid & UHMWPE fiber blend. 6. Gradient hot pressing: The graded and dispersed aramid & UHMWPE fibers are rolled into base paper with a basis weight of 120 g / m², placed in a flat vulcanizing machine preheated to 80°C, and pre-pressed at 4 MPa for 5 min to expel air from the material; the temperature is then increased to 150°C and the pressure is increased to 10 MPa, and hot pressing is carried out at constant temperature and pressure for 15 min; after naturally cooling to 100°C, the pressure is reduced to 2 MPa, and the material is further cooled to room temperature to obtain aramid & UHMWPE composite fiber material.

[0043] Example 3: 1. Raw material pretreatment: Aramid short-cut fibers are dried with UHMWPE at 105℃ for 2 hours; 2. Surface pre-activation of pulp: Add 2g of aramid pulp to 100g of deionized water, sonicate for 15min, add 0.06g of KH-560, stir at 50℃ for 30min, filter and dry at 80℃ to constant weight; 3. Plasma pretreatment of UHMWPE fiber: Place 2g of UHMWPE fiber in a low-temperature plasma treatment machine, introduce oxygen, pressurize at 80Pa, power at 100W, and treat for 3min; 4. Surface activation of UHMWPE fibers: Mix 0.02g KH-550 with 100g deionized water, add glacial acetic acid to adjust pH=4.5, stir for 10min; add plasma pretreated UHMWPE, shake and soak at 40℃ for 30min, pre-dry at 80℃ for 1h, and dry at 110℃ for 1.5h. 5. Grading and Dispersion: First, add KH-560 treated pulp and 1g KH-550 treated UHMWPE to the mixer. Stir at 800r / min for 3min, then increase to 1000r / min and stir for 5min. Then add 6g aramid chopped fiber and 1g KH-550 treated UHMWPE. Stir at 500r / min for 4min to obtain aramid & UHMWPE fiber blend. 6. Gradient hot pressing: The graded and dispersed aramid & UHMWPE fibers are rolled into base paper with a basis weight of 120 g / m², placed in a flat vulcanizing machine preheated to 80°C, and pre-pressed at 4 MPa for 5 min to expel air from the material; the temperature is then increased to 150°C and the pressure is increased to 10 MPa, and hot pressing is carried out at constant temperature and pressure for 15 min; after naturally cooling to 100°C, the pressure is reduced to 2 MPa, and the material is further cooled to room temperature to obtain aramid & UHMWPE composite fiber material.

[0044] Comparative Example 1: Raw material ratio: Aramid short chopped fiber: UHMWPE fiber: 5:3.

[0045] Preparation steps: 1. Aramid short-cut fibers are dried with UHMWPE at 105℃ for 2 hours; 2. Mix 0.03g KH-550 with 100g deionized water, add glacial acetic acid to adjust pH to 4.5, stir for 10min; add 3g UHMWPE, shake and soak at 40℃ for 30min, pre-dry at 80℃ for 1h, and dry at 110℃ for 1.5h; 3. 5g of aramid short-cut fiber and 3g of UHMWPE treated with KH-550 were put into a mixer and mixed at 1000r / min for 8min to obtain aramid & UHMWPE fiber blend. 4. The graded and dispersed aramid & UHMWPE fibers are rolled into base paper with a basis weight of 120 g / m², placed in a flat vulcanizing machine preheated to 80°C, and pre-pressed at 4 MPa for 5 min to expel air from the material and prevent bubbles from forming after molding; continue to heat to 150°C, increase the pressure to 10 MPa, and hot press at constant temperature and pressure for 15 min; after naturally cooling to 100°C, reduce the pressure to 2 MPa and continue to cool to room temperature to obtain aramid & UHMWPE composite fiber material.

[0046] The results are shown in Table 1.

[0047]

[0048] As shown in Table 1, with comparable thickness, the tensile strength of Examples 1-3 is increased by more than 50% and the elongation by more than 200% compared to the comparative example. The comparative example, lacking plasma treatment, exhibits significantly poor performance.

[0049] The UHMWPE content has been reduced from the industry standard of 45-65% to 30-45%, while the ratio of aramid chopped fibers to pulp has been increased. Under the premise that the continuous use temperature is increased to 198-202℃ (close to pure aramid), the tensile strength is still 64.6-75.4% higher than that of pure aramid, achieving the optimal balance of "high temperature resistance - lightweight and high strength". It is suitable for high temperature filter materials, secondary load-bearing components in aerospace, protective equipment or lightweight structural components.

[0050] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an aramid & UHMWPE composite fiber material, characterized in that... The steps include: S1. Pre-activation of pulp surface: Deionized water is added to meta-aramid short fibers to make pulp dispersion, then silane coupling agent is added and mixed evenly. Subsequently, vacuum filtration and drying are carried out to constant weight to obtain pre-activated aramid pulp. S2, UHMWPE fiber plasma pretreatment: The dried UHMWPE fiber is pretreated with plasma to introduce oxygen-containing polar groups on its surface; S3, UHMWPE fiber surface activation: Mix silane coupling agent with deionized water, adjust pH to 4-5 to promote the hydrolysis of silane coupling agent, and obtain modified solution; The plasma-pretreated UHMWPE fibers were immersed in a modification solution, the UHMWPE fibers soaked in the modification solution were removed, and then heated and dried to obtain activated UHMWPE fibers. S4. Grading and Dispersion: The pre-activated aramid pulp and a portion of activated UHMWPE fiber are mixed evenly at a high speed of 800–1000 r / min. Then, meta-aramid short-cut fibers and the remaining activated UHMWPE fibers are added and mixed evenly at a low speed of 500–600 r / min to obtain aramid & UHMWPE composite fiber. S5. Gradient hot pressing: Aramid & UHMWPE composite fibers are formed by a three-stage hot pressing process of pre-compression degassing, heating and pressurization, and slow cooling and depressurization to obtain aramid & UHMWPE composite fiber materials.

2. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: Before pre-activation of the aramid pulp surface, the meta-aramid chopped fibers and the UHMWPE fibers are dried separately at a temperature of 105°C for 2 hours.

3. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: The silane coupling agent used in step S1 is KH-560 silane coupling agent, and the amount of KH-560 added is 1–5% of the mass of aramid pulp.

4. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: The mixing temperature in step S1 is 50℃, the stirring time is 30 minutes, and the drying temperature is 80℃.

5. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: Step S2 involves placing the dried UHMWPE fibers in a low-temperature plasma treatment device, introducing air or oxygen, controlling the air pressure at 50-100 Pa, the power at 80-120 W, and the treatment time at 2-5 min.

6. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: The silane coupling agent used in step S3 is KH-550 silane coupling agent, and the amount of KH-550 silane coupling agent added is 0.5–3% of the mass of UHMWPE fiber.

7. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: In step S3, the pH is adjusted using 0.1% glacial acetic acid, and the stirring time is 10 minutes.

8. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: The soaking conditions in step S3 are constant temperature shaking soaking at 40℃ for 30 minutes. The UHMWPE fibers soaked in the modified solution are first pre-dried at 80℃ for 1 hour to remove free surface moisture, and then heated to 110℃ for 1.5 hours to obtain activated UHMWPE fibers.

9. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: The specific operation of step S4, graded dispersion, is as follows: the pre-activated aramid pulp and 50% by mass of activated UHMWPE fiber are first mixed at 800 r / min for 3 min; the speed is increased to 1000 r / min and the mixing is continued for 5 min to obtain pulp-UHMWPE composite material; the speed is reduced to 500 r / min, meta-aramid short-cut fiber and the remaining 50% activated UHMWPE fiber are added and mixed for 4 min to obtain aramid & UHMWPE composite fiber.

10. The method for preparing the aramid & UHMWPE composite fiber material according to claim 1, characterized in that: The specific operation of the three-stage hot pressing process in step S5 is as follows: Aramid & UHMWPE composite fibers are formed into sheets with a basis weight of 100-150 g / m². 2 The base paper is placed in a flat vulcanizing machine preheated to 80°C and pre-pressed at 4MPa for 5 minutes; then the temperature is raised to 160°C and the pressure is increased to 10MPa, and hot-pressed at constant temperature and pressure for 15 minutes; after naturally cooling to 100°C, the pressure is reduced to 2MPa and then cooled to room temperature to obtain aramid & UHMWPE composite fiber material.

Images