Modified aramid nanofiber and preparation method and application thereof

Abstract

The application belongs to the technical field of fiber materials, and particularly relates to a modified aramid nanofiber as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) preparing an aramid nanofiber dispersion liquid; (2) modifying the aramid nanofiber by using POSS; and (3) in-situ polymerizing polypyrrole on the surface of the aramid nanofiber. The POSS has a large volume exclusion effect, and the scattered attachment of the POSS on the surface of the aramid nanofiber can affect the templating effect of the long-chain alkyl quaternary ammonium salt, so as to cause the uneven polymerization of pyrrole monomers and be beneficial to the formation of a rough structure on the surface of the fiber. The aramid nanofiber coated with the polypyrrole with the rough structure is used as a modified material of polyolefin, so that the problem of low interface force existing in general fillers is solved, and a polyolefin resin composite material with high strength and antistatic performance is obtained, and the polyolefin resin composite material can be widely applied to the fields of pipe materials, plate materials, grouting equipment parts and grouting bags.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fiber materials, and particularly relates to a modified aramid nanofiber as well as a preparation method and application thereof. BACKGROUND

[0002] Aramid fiber is a general term for aromatic polyamide fibers, and is divided into poly-p-phenylene terephthalamide and poly-m-phenylene isophthalamide according to the molecular structure. Among them, poly-p-phenylene terephthalamide is obtained by condensation reaction of p-terephthaloyl chloride and p-phenylenediamine. Aramid fiber based on poly-p-phenylene terephthalamide is also called aramid 1414 or para-aramid, which was invented by DuPont Company in the 1960s and industrialized, and the trade name is Kevlar. It is prepared by dry-jet wet spinning of poly-p-phenylene terephthalamide liquid crystal solution. In the fiber, the rigid conjugated main chain of poly-p-phenylene terephthalamide shows high orientation order, and strong intermolecular forces are formed through ordered hydrogen bonds and π-π interactions, which is the source of high performance of para-aramid. Due to the characteristics of light weight, high strength, high modulus, heat resistance and flame resistance of para-aramid, aramid products directly processed therefrom or high-performance resin composites prepared by using para-aramid as a reinforcing body have important applications in the fields of aerospace, transportation, national defense equipment, special protection, sound absorption and vibration reduction, insulation and the like. However, para-aramid is difficult to be dissolved in conventional solvents and will not soften before thermal decomposition temperature, and the fiber surface has high chemical inertness, which greatly increases the difficulty of processing and compounding with other resin materials. In order to form effective interfacial bonding with resin, various methods of physical and chemical treatment of fiber surface are proposed in the prior art, such as ion plasma modification, ultrasonic immersion, surface coating and solid solution immersion. As a nanoscale product of aramid fiber, aramid nanofiber has high aspect ratio, large specific surface area and good dispersibility. Compared with aramid fiber, aramid nanofiber not only retains the high mechanical properties and excellent thermal stability of aramid fiber, but also can be used as a nanometer building unit to introduce nanometer material preparation methods to assemble high-level structures from bottom to top, and has become one of the materials with great application potential for constructing high-performance composites. However, aramid nanofiber also faces the technical problem of poor compatibility with resin.

[0003] Among them, polyolefin resin is a general term for polypropylene, polyethylene, ethylene-propylene-diene rubber, polyolefin elastomer and other thermoplastic resins. Among all polyolefin materials, polypropylene and polyethylene are the most widely used. Moreover, polypropylene and polyethylene have excellent chemical resistance and are easy to process and mold, and can be used for various methods such as extrusion, injection molding, blow molding and thermoforming. However, due to the large shrinkage of the molded product, the product surface is prone to warping and deformation, and it is difficult to achieve high precision size requirements. Moreover, the polyolefin resin has poor toughness, poor aging resistance and poor antistatic performance at low temperature.

[0004] Aramid nanofiber has high aspect ratio, large specific surface area, and is expected to solve the problem of low mechanical properties of polyolefin resin. CN112813692A provides a preparation method of para-aramid nanofiber modified polypropylene melt-blown non-woven fabric: configure para-aramid nanofiber dispersion liquid; manufacture polypropylene melt-blown non-woven fabric; para-aramid nanofiber spraying, after pressurized atomization of para-aramid nanofiber dispersion liquid through nozzle, spraying on the surface of melt-blown non-woven fabric through atomizing nozzle, the spraying amount of para-aramid nanofiber is 0.005-0.1% of the mass of polypropylene melt-blown non-woven fabric, after drum drying, corona discharge and electrostatic, the non-woven fabric is treated by high-voltage corona discharge and electrostatic, and para-aramid nanofiber modified polypropylene melt-blown non-woven fabric is obtained. This method significantly improves the mechanical properties of polypropylene, but does not solve the technical problems of large polyolefin insulation and poor antistatic property. CN116355319A discloses a conductive thermoplastic elastomer and a preparation method thereof, which comprises the following raw materials by weight percentage: polypropylene 15-50%, polar resin 10-30%, Cu3(HITP)2MOF@aramid nanofiber 0.5-5%, antioxidant 0.5-2% and filler 1-5%, and the balance is ethylene-propylene-diene rubber. The patent uses aramid nanofiber as a carrier, and uses conductive material Cu3(HITP)2MOF as a conductive material. The Cu3(HITP)2MOF is loaded on the surface of the aramid nanofiber by in-situ growth method, and a continuous conductive path is formed along the radial direction of the fiber. This material has the advantages of small amount and easy to build conductive grid, which can significantly improve the conductivity of polyolefin material. However, it uses expensive metal organic framework material, which not only has complex preparation process, but also does not completely solve the compatibility problem, and the improvement of mechanical properties is limited. Patents CN120574422A, CN120504961A, CN120607742A, CN120310019A, CN120589733A, etc. all use polypyrrole conductive polymer as conductive filler, but they do not fundamentally solve the problem of poor dispersion of polypyrrole in resin. SUMMARY

[0005] In order to solve the technical problems of easy agglomeration of aramid nanofiber and poor compatibility with polyolefin resin, the present application provides a modified aramid nanofiber. The surface of the aramid nanofiber is coated and modified to form a micro-rough structure, which increases the interaction area with the matrix resin, thereby improving the interfacial energy and the mechanical strength and antistatic ability of the polyolefin resin.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] A preparation method of modified aramid nanofiber, comprising the following steps:

[0008] (1) Put aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide to prepare aramid nanofiber, and then add long-chain alkyl quaternary ammonium salt to obtain aramid nanofiber dispersion;

[0009] (2) Add acid and active group-containing POSS to the aramid nanofiber dispersion, heat and stir for a certain time to obtain a POSS-modified aramid nanofiber dispersion; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is (0.01-0.2):1;

[0010] (3) Add pyrrole monomer and initiator to the POSS-modified aramid nanofiber dispersion, react for a certain time, filter, wash and dry to obtain modified aramid nanofiber.

[0011] Polyolefin materials have low mechanical strength and poor antistatic performance. The existing technology generally improves the mechanical properties and antistatic ability of polyolefin composite materials by adding reinforcing fillers and conductive substances respectively.

[0012] The most common reinforcing filler for polyolefin is various organic or inorganic fiber materials. Aramid nanofiber, as a nanoscale product of aramid fiber, has a high aspect ratio, large specific surface area and good dispersibility. Compared with aramid fiber, aramid nanofiber not only retains the high mechanical properties and excellent thermal stability of aramid fiber, but also can be used as a nanoscale building block to introduce nanomaterials and prepare high-level structures from bottom to top. In previous work, the inventors have prepared various forms of aerogel materials (CN118878287A, CN118851649A, CN118812184A, CN118702437A) by compounding aramid nanofiber / inorganic filler to enhance the stability of concrete. However, aramid nanofiber / inorganic filler aerogel is only suitable for the modification of inorganic materials such as concrete, and when it is directly applied to organic polymer materials such as polyolefin, it is difficult to disperse uniformly in polyolefin due to compatibility problems, which may cause stress concentration and even reduce the performance of the composite material.

[0013] To improve the antistatic property of polyolefin resin, conductive fillers are generally added. The conductive materials can be conductive carbon black, carbon fiber, carbon nanotube, graphite, conductive polymer, metal powder, and various conductive metal oxides and metal salts. The composite conductive polyolefin resin has both the processing characteristics of polymer materials and the conductivity of metal. Compared with metal, the composite conductive polyolefin resin has the advantages of good processability, simple process, corrosion resistance, large adjustable range of resistivity, and low price. At present, the conductive materials added to the composite conductive polyolefin resin are small molecule antistatic agents and conductive fillers. Adding antistatic agents is the most common antistatic method for polymer materials. The antistatic agents form a conductive layer on the surface of the material, reduce the surface resistivity, make the generated static charge leak out quickly, and at the same time, give the material surface certain lubricity, reduce the friction coefficient, inhibit and reduce the generation of static charge. However, the reduction of the resistivity by adding small molecule antistatic agents is limited, the durability is poor, and the mechanical properties of the composite material are reduced. Therefore, at present, the composite polyolefin resin mainly adds conductive fillers. Among them, polypyrrole as a common conductive polymer material, adding polypyrrole can improve the antistatic property of polyolefin resin to a certain extent.

[0014] However, a large amount of reinforcing fillers and conductive materials will cause the processing performance of the composite material to decrease, the compatibility of the components to become poor, and it is difficult to simultaneously improve the mechanical properties and antistatic ability. In the previous work, the inventors prepared polypropylene-coated aramid nanofiber. However, the surface of the fiber is smooth, and the interaction force with polyolefin is low, so it is easy to separate at the interface under the action of pulling force, so it needs to be prepared into a composite aerogel to increase the interface area with polyolefin resin, which increases the process complexity and cost.

[0015] To solve this problem, the inventors creatively prepared polypropylene-coated aramid nanofiber with a rough structure. Using polypropylene-coated aramid nanofiber as a reinforcing and conductive material can greatly improve the mechanical strength and antistatic property of polyolefin composite material. As a nanoscale filler, directly adding aramid nanofiber not only easily causes compatibility problems with polyolefin, but also easily causes agglomeration in the processing process due to the strong interaction force of the aramid nanofiber with many surface defects, loses the nanoscale size, and reduces the modification effect. After the polypropylene-coated aramid nanofiber is used, not only the dispersion performance of the fiber is improved, but also the compatibility of the aramid nanofiber with the polyolefin resin is improved through the rough structure of the coating interface, so that the aramid nanofiber is uniformly dispersed in the matrix resin. In turn, the aramid nanofiber as the core layer substrate of polypyrrole can also promote the dispersion of polypyrrole, so that polypyrrole forms a network structure, which is conducive to the formation of conductive paths; with less polypyrrole, the conductive property of the polyolefin composite material can be greatly improved, avoiding the technical problem of mechanical property reduction caused by the large amount of polypyrrole.

[0016] More importantly, the polyacrylonitrile nanofiber coated with polypyrrole with rough structure as an additive of polyolefin material solves the problem of poor compatibility of general fillers. By increasing the roughness of the surface of the polyacrylonitrile nanofiber coated with polypyrrole, the polyolefin resin can be filled in the grooves on the fiber surface, and the interface bonding degree between the fiber and the polyolefin resin can be enhanced by physical entanglement. Compared with the polyacrylonitrile nanofiber coated with polypyrrole with smooth structure prepared by the inventor before, the polyolefin resin can be better filled in the grooves on the rough fiber surface, thereby increasing the contact area between the fiber and the polyolefin resin; at the same time, the polyolefin resin can be better physically entangled on the fiber surface, and the fiber and the polyolefin can be mechanically locked together after curing through the rough morphology of the fiber surface, thereby enhancing the interface bonding force and mechanical bonding strength between the polyacrylonitrile nanofiber coated with polypyrrole and the polyolefin resin.

[0017] Overall, the modified polyacrylonitrile nanofiber prepared by the present application is a composite fiber with a rough surface in one-dimensional form formed by polyacrylonitrile nanofiber and polypyrrole, which can be directly used as a conductive and reinforcing filler of polyolefin resin. Due to the presence of the rough structure polypyrrole coating layer, there is a high interface force between the fiber and the polyolefin resin, which meets the use requirements of the mechanical properties and antistatic properties of the polyolefin. The modified polyacrylonitrile nanofiber is compounded with different polyolefin resin materials, and the different components in the composite material synergistically act at the molecular level to form a resin composite material with a new structure and function.

[0018] Further, the base in step (1) is sodium hydroxide or potassium hydroxide.

[0019] Further, the ratio of polyacrylonitrile fiber, base and dimethyl sulfoxide in step (1) is 1 g: (1-2) g: (350-500) ml. In particular, the preparation process of polyacrylonitrile nanofiber is stirring reaction at room temperature in a reaction kettle for 4-8 days. Further, a commercial polyacrylonitrile fiber is used. During the preparation process of the commercial polyacrylonitrile fiber, various oils may be left on the surface of the fiber, which can be cleaned. Specifically, the fiber surface can be cleaned with acetone solvent, sodium dodecyl benzene sulfonate solution and deionized water in sequence to remove oil and other impurities on the fiber surface.

[0020] Further, the long-chain alkyl quaternary ammonium salt in step (1) is at least one of dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride. In particular, hexadecyl trimethyl ammonium bromide can be selected. By adding long-chain alkyl quaternary ammonium salt in advance to the aramid nanofiber dispersion liquid, the dispersibility of aramid nanofiber can be improved, and the long-chain alkyl quaternary ammonium salt can also play a role as a template. This is because the aramid nanofiber prepared by the alkali / DMSO soaking method contains a large number of reactive oxygen-containing functional groups such as carboxyl and hydroxyl on the surface, which are electronegative. Although the aspect ratio is large and the mechanical properties are excellent, the mixed solution after soaking is extremely unstable. When new polar substances (acid, pyrrole monomer, initiator, etc.) are added, the balance of the solution is destroyed, the fiber bundles between the fibers are combined, and the fiber agglomeration phenomenon occurs, which affects the dispersion of aramid nanofiber. As a cationic surface modifier, the long-chain alkyl quaternary ammonium salt has good surface modification function, and the presence of ammonium ion is conducive to the combination of the long-chain alkyl quaternary ammonium salt with aramid nanofiber, and improves the dispersibility of aramid nanofiber. At the same time, the long-chain alkyl quaternary ammonium salt has a long alkyl chain, which can improve the hydrophilic and hydrophobic properties of the surface of aramid nanofiber, and is conducive to the attachment of pyrrole monomer to form a coating structure by in-situ polymerization. Moreover, the presence of long-chain alkyl can hinder the combination between fibers and promote the dispersion of fibers. In the previous work, the inventors used 1wt% sodium hydroxide aqueous solution to corrode aramid fiber for several hours, and then directly polymerized conductive monomers on the surface of the aramid fiber to prepare polymer-coated aramid fiber. The main form of the aramid fiber of this structure has not changed, which is not a nano structure, but only the surface of the fiber is corroded. Although the relatively thick fiber will not agglomerate, this process does not need to add long-chain alkyl quaternary ammonium salt. However, due to the relatively thick diameter of the fiber, it cannot be used in the field of polyolefin modification, but only in the field of reinforcing inorganic materials such as concrete and cement slurry.

[0021] Further, the mass ratio of the long-chain alkyl quaternary ammonium salt to aramid fiber is (0.1-0.5):1. Specifically, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1; in particular, it is (0.2-0.4):1. The appropriate amount of long-chain alkyl quaternary ammonium salt can not only fully play the role of dispersing aramid nanofiber and serving as a template for pyrrole polymerization, but also avoid the mutual entanglement of long-chain alkyl quaternary ammonium salts themselves due to too much long-chain alkyl quaternary ammonium salt.

[0022] Further, the acid in step (2) is one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, propionic acid, formic acid, malic acid, and phosphoric acid. The molar ratio of the acid to the base in step (1) is (0.5-2):1, and further (1-2):1. In particular, one of concentrated hydrochloric acid, concentrated sulfuric acid, and concentrated nitric acid can be selected. Further, high-concentration concentrated nitric acid can be selected.

[0023] Further, the active group-containing POSS in the step (2) is at least one of amino-containing POSS, hydroxyl-containing POSS, epoxy-containing POSS, carboxyl-containing POSS, and sulfhydryl-containing POSS. Specifically, it can be at least one of aminopropyl heptaphenyl POSS, aminopropyl heptaisobutyl POSS, octaaminophenyl POSS, octaaminopropyl POSS, heptaisooctyl epoxy POSS, heptaisobutyl epoxy POSS, octahydroxybutyl POSS, octa-mercapto-propyl POSS, mercapto-propyl isobutyl POSS, octa-methylcarboxyl POSS, octa-ethylcarboxyl POSS, and octa-propylcarboxyl POSS. In particular, amino-functionalized POSS can be selected. Further, octaaminophenyl POSS or octaaminopropyl POSS having eight functional groups can be selected. The amino group has a higher activity and is more likely to form a chemical bond with an oxygen-containing functional group such as a carboxyl group, which can better promote the combination of POSS and aramid nanofibers. In particular, the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is (0.05-0.2):1. Since POSS has a large volume and a hydrophobic effect, the amount of POSS should not be too large, otherwise the large structure of POSS will hinder the attachment of polypyrrole and affect the modification of aramid nanofibers.

[0024] POSS plays a role in surface modification and dispersion polymerization in the present application. POSS (polyhedral oligomeric silsesquioxane) is a kind of organic-inorganic hybrid material, which has an external organic group and exhibits a three-dimensional structure system at the nanoscale. Compared with general polysiloxanes, POSS has better heat resistance and lower surface energy. The POSS molecule has a closed cubic structure on a macro scale. The external alkane substituent or active reaction group of the POSS molecule can not only improve the compatibility between POSS and the polymer, but also achieve the chemical bonding between POSS and the polymer. Therefore, it is used to modify aramid nanofibers to improve the interfacial properties of aramid nanofibers and polypyrrole. Specifically, the aramid nanofibers prepared by the alkali splitting method have a large number of hydroxyl, carboxyl and other oxygen-containing functional groups on the surface. The active group-containing POSS is used as a modifier, and the active group on the POSS is easy to form a strong chemical bond such as hydrogen bond with the oxygen-containing functional group on the surface of aramid nanofibers. However, the POSS has a large volume exclusion effect and hydrophobic property, and the random attachment of POSS on the surface of aramid nanofibers will affect the templating effect of long-chain alkyl quaternary ammonium salt and the polymerization process of pyrrole monomers. The uneven polymerization of pyrrole monomers on the surface of aramid nanofibers leads to the formation of a rough structure on the surface.

[0025] Further, the temperature of heating and stirring in the step (2) is 80-100℃, and the time is 3-5h. Through the process of heating and stirring, not only the uniform dispersion of the active group-containing POSS can be promoted, but also the chemical bond between the active group-containing POSS and the oxygen-containing functional group on the surface of aramid nanofibers can be formed.

[0026] Further, the initiator in the step (3) is at least one of ammonium persulfate, potassium persulfate, ferric chloride, and azobisisobutyronitrile. In particular, ferric chloride with doping effect can be selected. Since the aramid nanofiber is modified by the long-chain alkyl quaternary ammonium salt, the addition of the polar compounds such as the acid, the pyrrole monomer and the initiator will not cause the merging of the fiber bundles. If the polar compounds such as the acid, the pyrrole monomer or the initiator are added first, and then the long-chain alkyl quaternary ammonium salt is added, not only the fiber bundles will merge, but also the long-chain alkyl quaternary ammonium salt will not be adsorbed on the fiber surface, the template effect will be lost, and the poly-pyrrole coating structure cannot be formed.

[0027] Further, the reaction temperature in the step (3) is 0-30℃, and the reaction time is 8-12h.

[0028] Further, the mass ratio of the initiator to the pyrrole monomer in the step (3) is (1-5):1.

[0029] Further, the mass ratio of the pyrrole monomer to the aramid fiber in the step (3) is (0.1-1):1. The introduction of the POSS modifier improves the dispersibility of the aramid nanofiber, and can better promote the in-situ polymerization of the pyrrole monomer and improve the loading amount of the poly-pyrrole. Further, the mass ratio of the pyrrole monomer to the aramid fiber is (0.2-0.8):1 or (0.3-0.7):1. The aramid nanofiber is coated with an appropriate amount of poly-pyrrole, which is beneficial to the formation of the rough structure and can avoid the problem of excessive poly-pyrrole falling off.

[0030] Further, the washing is carried out by using deionized water, and the drying is carried out by placing in an oven.

[0031] Further, the application also provides a modified aramid nanofiber and its application in the preparation of high-strength pipe, plate, grouting equipment parts and grouting bag.

[0032] In another aspect, the present application provides a polyolefin composite material, comprising the following components by weight: polyolefin resin 50-150 parts, modified aramid nanofiber, 1-30 parts of inorganic fiber reinforcing filler, 1-10 parts of processing aid. In particular, the composite material can be formed by extruder granulation, the extrusion temperature is 150-200℃, in particular 170-190℃. Through the high temperature melting process, it is beneficial for the polyolefin melt to fully infiltrate the rough structure of the aramid nanofiber surface. The type of polyolefin resin is not particularly limited, and the types commonly used in the art such as polyethylene, polypropylene, polybutylene, polystyrene, etc. can be used. Further, the polyolefin composite material can also include glass fiber, carbon fiber, flame retardant, lubricant, flow modifier, toner, anti-aging agent, antioxidant, anti-hydrolysis agent, coupling agent and other aids. In particular, conductive fibrous fillers can be added to promote the formation of a conductive network. The raw materials used in the present application are of common type and can be prepared or purchased and recycled. For example, aramid fibers can be selected from DuPont K series fibers, polyolefins can be selected from Sinopec PPH series polypropylene, carbon fibers can be selected from Toray T series carbon fibers, antioxidants can be selected from Xindongyi Chemical 1010 series, coupling agents can be selected from Hairexinnian material KH570 series, etc. Specifically, the present application uses recycled polypropylene as the base material, which not only saves cost, but also solves the technical problem of poor mechanical properties of recycled polypropylene.

[0033] Advantages:

[0034] (1) POSS has a large volume exclusion effect and hydrophobic property. The random attachment of POSS on the surface of aramid nanofiber can affect the templating effect of long-chain alkyl quaternary ammonium salt and the polymerization process of pyrrole monomer. The uneven polymerization of pyrrole monomer on the surface of aramid nanofiber leads to the formation of rough structure on the surface.

[0035] (2) After the aramid nanofiber is coated with polypyrrole, not only the dispersion performance of the fiber is improved, but also the compatibility of aramid nanofiber and polyolefin resin is improved through the coated interface with rough structure, so that the aramid nanofiber is uniformly dispersed in the matrix resin. On the other hand, the aramid nanofiber as the core layer substrate of polypyrrole can also promote the dispersion of polypyrrole, so that the polypyrrole forms a network structure, which is beneficial to the formation of conductive path; a small amount of polypyrrole can greatly improve the conductive performance of the polyolefin composite material, avoiding the technical problem of mechanical property reduction caused by large amount of polypyrrole addition. It has wide application in the fields of pipe, plate, grouting equipment parts and grouting bag which have high requirements on mechanical strength and antistatic performance. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Scanning electron microscope image of aramid nanofiber prepared in step (1) of Example 10.

[0037] Figure 2 Scanning electron microscope image of modified aramid nanofiber prepared for Example 10.

[0038] Figure 3 Scanning electron microscope image of modified aramid nanofiber prepared for Comparative Example 1. DETAILED DESCRIPTION

[0039] The application will be further described in detail by the following examples and drawings, the raw materials used in the examples can be commercially available or prepared by conventional methods.

[0040] In the following examples and comparative examples, the types of raw materials and specific process steps used are the same unless otherwise specified. In the present application, the aramid fiber used is Kevlar fiber from DuPont after cleaning and removing oil. The cleaning process is to first put the aramid fiber into an acetone solution and ultrasonically treat it, then take it out and clean it with deionized water again; then put it into a sodium dodecyl sulfonate aqueous solution (5wt%) and ultrasonically treat it again; finally, repeatedly clean it with flowing deionized water to remove the oil on the surface of the aramid fiber.

[0041] Performance test: a kind of polypropylene composite material, comprising the following components by weight: polypropylene resin 100 parts, 12 parts of modified aramid nanofiber (prepared in Examples 1-10 and Comparative Examples 1-2, respectively), 4.5 parts of carbon fiber, 1.5 parts of antioxidant 1010, 1.5 parts of polyethylene wax lubricant. The above components are added to a twin-screw extruder, and melt extruded and granulated (the temperature of the extruder is 190°C). Then standard samples are prepared, and their mechanical properties and antistatic properties are tested respectively. Among them, the tensile strength refers to ASTM D638, the bending strength refers to ASTM D790; and the volume resistivity of the sample is tested by using a resistance meter.

[0042] Example 1

[0043] A method for preparing a modified aramid nanofiber, comprising the following steps:

[0044] (1) Put the aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide and stir at room temperature for 4.5 days to prepare aramid nanofiber, then add long-chain alkyl quaternary ammonium salt hexadecyl trimethyl ammonium bromide and stir uniformly to obtain aramid nanofiber dispersion; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:2g:400ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.1:1;

[0045] (2) Add concentrated nitric acid to the aramid nanofiber dispersion and stir uniformly, then add active group-containing POSS octaaminophenyl POSS and stir at 80°C for 5h to obtain POSS modified aramid nanofiber dispersion; the molar ratio of acid to potassium hydroxide in concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.01:1;

[0046] (3) adding pyrrole monomer and initiator ferric chloride into the POSS modified aramid nanofiber dispersion liquid, reacting at 15℃ for 12h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.1:1; the mass ratio of initiator to pyrrole monomer is 2.4:1. The corresponding polypropylene composite material has a tensile strength of 45.2MPa, a bending strength of 56.0MPa, and a volume resistivity of 7.4×10 6 Ω·m.

[0047] Example 2

[0048] A method for preparing modified aramid nanofiber, comprising the following steps:

[0049] (1) putting aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stirring at room temperature for 7 days to prepare aramid nanofiber, then adding long-chain alkyl quaternary ammonium salt hexadecyl trimethyl ammonium bromide to obtain aramid nanofiber dispersion liquid; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1g:480ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.35:1;

[0050] (2) adding concentrated nitric acid into the aramid nanofiber dispersion liquid and stirring uniformly, then adding active group containing POSS octaaminophenyl POSS to obtain POSS modified aramid nanofiber dispersion liquid by stirring at 95℃ for 5h; the molar ratio of acid to potassium hydroxide in concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.2:1;

[0051] (3) adding pyrrole monomer and initiator ferric chloride into the POSS modified aramid nanofiber dispersion liquid, reacting at 23℃ for 8h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.7:1; the mass ratio of initiator to pyrrole monomer is 3.6:1. The corresponding polypropylene composite material has a tensile strength of 39.3MPa, a bending strength of 47.6MPa, and a volume resistivity of 7.5×10 5 Ω·m.

[0052] Example 3

[0053] A method for preparing modified aramid nanofiber, comprising the following steps:

[0054] (1) Put aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stir at room temperature for 5 days to prepare aramid nanofiber, then add long-chain alkyl quaternary ammonium salt cetyltrimethyl ammonium bromide, stir uniformly to obtain aramid nanofiber dispersion; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.2g:500ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.5:1;

[0055] (2) Add concentrated nitric acid to the aramid nanofiber dispersion and stir uniformly, then add active group-containing POSS octaaminophenyl POSS, stir at 90℃ for 4h to obtain POSS modified aramid nanofiber dispersion; the molar ratio of acid to potassium hydroxide in concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.1:1;

[0056] (3) Add pyrrole monomer and initiator ferric chloride to the POSS modified aramid nanofiber dispersion, react at 18℃ for 10h, filter, wash with deionized water, dry in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.45:1; the mass ratio of initiator to pyrrole monomer is 3.1:1. The corresponding polypropylene composite material has a tensile strength of 42.6MPa, a bending strength of 51.3MPa, and a volume resistivity of 5.5×10 6 Ω·m.

[0057] Example 4

[0058] A method for preparing modified aramid nanofiber, comprising the following steps:

[0059] (1) Put aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stir at room temperature for 6.5 days to prepare aramid nanofiber, then add long-chain alkyl quaternary ammonium salt cetyltrimethyl ammonium bromide, stir uniformly to obtain aramid nanofiber dispersion; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.3g:430ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.32:1;

[0060] (2) Add concentrated nitric acid to the aramid nanofiber dispersion and stir uniformly, then add active group-containing POSS octaaminophenyl POSS, stir at 80℃ for 3h to obtain POSS modified aramid nanofiber dispersion; the molar ratio of acid to potassium hydroxide in concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.18:1;

[0061] (3) adding pyrrole monomer and initiator ferric chloride into the POSS modified aramid nanofiber dispersion liquid, reacting at 15℃ for 8h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.25:1; the mass ratio of initiator to pyrrole monomer is 3.6:1. The corresponding polypropylene composite material has a tensile strength of 45.8MPa, a bending strength of 55.3MPa, and a volume resistivity of 6.9×10 6 Ω·m.

[0062] Example 5

[0063] A method for preparing modified aramid nanofiber, comprising the following steps:

[0064] (1) placing aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stirring at room temperature for 5 days to prepare aramid nanofiber, then adding long-chain alkyl quaternary ammonium salt cetyltrimethyl ammonium bromide, and stirring uniformly to obtain aramid nanofiber dispersion liquid; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.2g:500ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.2:1;

[0065] (2) adding concentrated nitric acid into the aramid nanofiber dispersion liquid and stirring uniformly, then adding active group-containing POSS octaaminophenyl POSS, and stirring at 90℃ for 4h to obtain POSS modified aramid nanofiber dispersion liquid; the molar ratio of acid to potassium hydroxide in the concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.3:1;

[0066] (3) adding pyrrole monomer and initiator ferric chloride into the POSS modified aramid nanofiber dispersion liquid, reacting at 18℃ for 10h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.45:1; the mass ratio of initiator to pyrrole monomer is 3.1:1. The corresponding polypropylene composite material has a tensile strength of 43.8MPa, a bending strength of 52.7MPa, and a volume resistivity of 9.3×10 6 Ω·m.

[0067] Example 6

[0068] A method for preparing modified aramid nanofiber, comprising the following steps:

[0069] (1) Put aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stir at room temperature for 5 days to prepare aramid nanofiber, then add long-chain alkyl quaternary ammonium salt cetyltrimethyl ammonium bromide, stir uniformly to obtain aramid nanofiber dispersion; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.7g:440ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.17:1;

[0070] (2) Add concentrated nitric acid to the aramid nanofiber dispersion and stir uniformly, then add active group-containing POSS octaaminophenyl POSS, stir at 83℃ for 4.5h to obtain POSS modified aramid nanofiber dispersion; the molar ratio of acid to potassium hydroxide in concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.07:1;

[0071] (3) Add pyrrole monomer and initiator ferric chloride to the POSS modified aramid nanofiber dispersion, react at 17℃ for 11h, filter, wash with deionized water, dry in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.3:1; the mass ratio of initiator to pyrrole monomer is 2.8:1. The corresponding polypropylene composite material has a tensile strength of 43.1MPa, a bending strength of 51.7MPa, and a volume resistivity of 5.1x10 6 Ω·m.

[0072] Example 7

[0073] A method for preparing modified aramid nanofiber, comprising the following steps:

[0074] (1) Put aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stir at room temperature for 5 days to prepare aramid nanofiber, then add long-chain alkyl quaternary ammonium salt cetyltrimethyl ammonium bromide, stir uniformly to obtain aramid nanofiber dispersion; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.2g:500ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.2:1;

[0075] (2) Add concentrated nitric acid to the aramid nanofiber dispersion and stir uniformly, then add active group-containing POSS octaaminophenyl POSS, stir at 90℃ for 4h to obtain POSS modified aramid nanofiber dispersion; the molar ratio of acid to potassium hydroxide in concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.1:1;

[0076] (3) adding pyrrole monomer and initiator ferric chloride into the POSS modified aramid nanofiber dispersion liquid, reacting at 18℃ for 10h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 1:1; the mass ratio of initiator to pyrrole monomer is 3.1:1. The corresponding polypropylene composite material has a tensile strength of 38.1MPa, a bending strength of 48.7MPa, and a volume resistivity of 7.7×10 5 Ω·m.

[0077] Example 8

[0078] A method for preparing modified aramid nanofiber, comprising the following steps:

[0079] (1) placing aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stirring at room temperature for 6 days to prepare aramid nanofiber, then adding long-chain alkyl quaternary ammonium salt cetyltrimethyl ammonium bromide, and stirring uniformly to obtain aramid nanofiber dispersion liquid; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.6g:380ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.3:1;

[0080] (2) adding concentrated nitric acid into the aramid nanofiber dispersion liquid and stirring uniformly, then adding active group-containing POSS octaaminophenyl POSS, and stirring at 90℃ for 3.5h to obtain POSS modified aramid nanofiber dispersion liquid; the molar ratio of acid to potassium hydroxide in the concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.16:1;

[0081] (3) adding pyrrole monomer and initiator ferric chloride into the POSS modified aramid nanofiber dispersion liquid, reacting at 21℃ for 9h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.6:1; the mass ratio of initiator to pyrrole monomer is 3.3:1. The corresponding polypropylene composite material has a tensile strength of 39.5MPa, a bending strength of 48.1MPa, and a volume resistivity of 2.4×10 6 Ω·m.

[0082] Example 9

[0083] A method for preparing modified aramid nanofiber, comprising the following steps:

[0084] (1) Put aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stir at room temperature for 6 days to prepare aramid nanofiber, then add long-chain alkyl quaternary ammonium salt cetyltrimethyl ammonium bromide, stir uniformly to obtain aramid nanofiber dispersion; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.4g:420ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.23:1;

[0085] (2) Add concentrated nitric acid to the aramid nanofiber dispersion and stir uniformly, then add active group-containing POSS octaaminophenyl POSS, stir at 88℃ for 4.2h to obtain POSS modified aramid nanofiber dispersion; the molar ratio of acid to potassium hydroxide in concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.13:1;

[0086] (3) Add pyrrole monomer and initiator ferric chloride to the POSS modified aramid nanofiber dispersion, react at 19℃ for 9h, filter, wash with deionized water, dry in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.7:1; the mass ratio of initiator to pyrrole monomer is 3.1:1. The corresponding polypropylene composite material has a tensile strength of 41.5MPa, a bending strength of 53.1MPa, and a volume resistivity of 5.7x10 6 Ω·m.

[0087] Example 10

[0088] A method for preparing modified aramid nanofiber, comprising the following steps:

[0089] (1) Put aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stir at room temperature for 5 days to prepare aramid nanofiber, then add long-chain alkyl quaternary ammonium salt cetyltrimethyl ammonium bromide, stir uniformly to obtain aramid nanofiber dispersion; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.2g:500ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.2:1;

[0090] (2) Add concentrated nitric acid to the aramid nanofiber dispersion and stir uniformly, then add active group-containing POSS octaaminophenyl POSS, stir at 90℃ for 4h to obtain POSS modified aramid nanofiber dispersion; the molar ratio of acid to potassium hydroxide in concentrated nitric acid is 1:1; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.1:1;

[0091] (3) adding pyrrole monomer and initiator ferric chloride into the POSS modified aramid nanofiber dispersion liquid, reacting at 18℃ for 10h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.45:1; the mass ratio of initiator to pyrrole monomer is 3.1:1. The corresponding polypropylene composite material has a tensile strength of 44.6MPa, a bending strength of 54.1MPa, and a volume resistivity of 8.2×10 5 Ω·m.

[0092] Comparative Example 1

[0093] A method for preparing modified aramid nanofiber, comprising the following steps:

[0094] (1) placing aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stirring at room temperature for 5 days to prepare aramid nanofiber, then adding long-chain alkyl quaternary ammonium salt hexadecyl trimethyl ammonium bromide to obtain aramid nanofiber dispersion liquid; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.2g:500ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.2:1;

[0095] (2) adding concentrated nitric acid into the aramid nanofiber dispersion liquid and stirring uniformly to obtain modified aramid nanofiber dispersion liquid; the molar ratio of acid to potassium hydroxide in the concentrated nitric acid is 1:1;

[0096] (3) adding pyrrole monomer and initiator ferric chloride into the modified aramid nanofiber dispersion liquid, reacting at 18℃ for 10h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.45:1; the mass ratio of initiator to pyrrole monomer is 3.1:1. The corresponding polypropylene composite material has a tensile strength of 44.6MPa, a bending strength of 54.1MPa, and a volume resistivity of 8.2×10 7 Ω·m.

[0097] Comparative Example 2

[0098] A method for preparing modified aramid nanofiber, comprising the following steps:

[0099] (1) placing aramid fiber into a reaction kettle containing alkali and dimethyl sulfoxide, stirring at room temperature for 5 days to prepare aramid nanofiber, then adding long-chain alkyl quaternary ammonium salt hexadecyl trimethyl ammonium bromide to obtain aramid nanofiber dispersion liquid; the alkali is potassium hydroxide; the ratio of aramid fiber, alkali and dimethyl sulfoxide is 1g:1.2g:500ml; the mass ratio of long-chain alkyl quaternary ammonium salt to aramid fiber is 0.2:1; the molar ratio of acid to potassium hydroxide in the concentrated nitric acid is 1:1;

[0100] (2) adding active group-containing POSS octaaminophenyl POSS to the aramid nanofiber dispersion liquid, stirring at 90°C for 4h to obtain a POSS-modified aramid nanofiber dispersion liquid; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is 0.1:1;

[0101] (3) adding pyrrole monomer and initiator ferric chloride to the POSS-modified aramid nanofiber dispersion liquid, reacting at 18°C for 10h, filtering, washing with deionized water, drying in an oven to obtain modified aramid nanofiber; the mass ratio of pyrrole monomer to aramid fiber is 0.45:1; the mass ratio of initiator to pyrrole monomer is 3.1:1. After testing, the corresponding polypropylene composite material has a tensile strength of 31.5MPa, a bending strength of 39.8MPa, and a volume resistivity of 8.3×10 8 Ω·m.

[0102] Figure 1 、 Figure 2 and Figure 3 are scanning electron microscope images of aramid nanofiber and modified aramid nanofiber prepared in Example 10, respectively, and a scanning electron microscope image of modified aramid nanofiber prepared in Comparative Example 1. The test sample is obtained by repeatedly washing and filtering the corresponding aramid nanofiber and modified aramid nanofiber with deionized water to remove impurities. Figure 1 Compared with the original aramid nanofiber in Figure 2 and Figure 3 , the fiber diameter is significantly thickened, indicating that the pyrrole monomer has undergone in-situ polymerization on the surface of the aramid nanofiber, increasing the fiber diameter. Among them, Figure 2 The modified aramid nanofiber has a granular irregular morphology on the surface, indicating that the polypyrrole forms a rough structure on the surface of the aramid nanofiber. Figure 3 is a scanning electron microscope image of modified aramid nanofiber prepared in Comparative Example 1. Although the diameter of the fiber is larger than that of the original aramid nanofiber in Figure 1The surface is smoother and no rough structure is formed. Meanwhile, according to the data of the examples and comparative examples, it can be seen that the polyacrylonitrile nanofiber coated with polypyrrole with a rough structure as an additive of the polyolefin material solves the problem of poor compatibility of general fillers. By increasing the roughness of the surface of the polyacrylonitrile nanofiber coated with polypyrrole, the resin can be filled in the grooves on the surface of the fiber, and the interface bonding between the fiber and the resin is enhanced by physical entanglement, which is conducive to the adhesion of polypyrrole, prevents the polypyrrole from falling off during processing, and affects the formation of the conductive path. Compared with the polyacrylonitrile nanofiber coated with polypyrrole with a smooth structure prepared by the inventors before, the resin can be better filled in the grooves on the rough surface of the fiber, thereby increasing the contact area between the fiber and the resin; at the same time, the resin can be better physically entangled on the surface of the fiber, and the fiber and the polymer can be mechanically locked together after curing through the rough morphology of the fiber surface, thereby enhancing the interface bonding force and mechanical bonding strength between the polyacrylonitrile nanofiber coated with polypyrrole and the resin. Compared with Example 10, Comparative Example 1 does not add POSS containing active groups, and loses the volume exclusion effect. The template effect of the long-chain alkyl quaternary ammonium salt makes the pyrrole monomer uniformly polymerize, forming a smooth surface. Comparative Example 2 does not add cetyltrimethylammonium bromide in advance, which cannot fully play a role in dispersion and template, and cannot form a stable coating structure, affecting the dispersion of the polyacrylonitrile nanofiber, and being not conducive to the formation of the reinforcing network and the conductive network, and the mechanical properties and conductivity of the prepared polypropylene composite material are reduced.

[0103] The above examples do not limit the content of the composition of the present application in any way. Any minor modification, equivalent change and modification made to the above examples according to the technical essence or composition ingredients or content of the present application still falls within the scope of the technical solution of the present application.

Claims

1. A method for preparing a modified aramid nanofiber, characterized by, The method comprises the following steps: (1) putting aramid fibers into a reaction kettle containing alkali and dimethyl sulfoxide to prepare aramid nanofibers, and then adding long-chain alkyl quaternary ammonium salt to obtain aramid nanofiber dispersion liquid; (2) adding acid and active group-containing POSS to the aramid nanofiber dispersion liquid, heating and stirring to obtain POSS-modified aramid nanofiber dispersion liquid; the mass ratio of POSS to long-chain alkyl quaternary ammonium salt is (0.01-0.3):1; the active group-containing POSS is at least one of amino-containing POSS, hydroxyl-containing POSS, epoxy-containing POSS, carboxyl-containing POSS and sulfhydryl-containing POSS; (3) adding pyrrole monomer and initiator to the POSS-modified aramid nanofiber dispersion liquid, and after reaction, filtering, washing and drying to obtain modified aramid nanofibers.

2. The method for preparing modified aramid nanofibers as described in claim 1, characterized in that, The long-chain alkyl quaternary ammonium salt in step (1) is at least one of dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium bromide and octadecyl trimethyl ammonium chloride.

3. The method for preparing modified aramid nanofibers as described in claim 1, characterized in that, The mass ratio of long-chain alkyl quaternary ammonium salt to aramid fibers in step (1) is (0.1-0.5):

1.

4. The method for preparing modified aramid nanofibers as described in claim 1, characterized in that, The acid in step (2) is at least one of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, propionic acid, formic acid, malic acid and phosphoric acid.

5. The method for preparing modified aramid nanofibers as described in claim 1, characterized in that, The mass ratio of pyrrole monomer to aramid fibers in step (3) is (0.1-1):

1.

6. The method for preparing modified aramid nanofibers as described in claim 1, characterized in that, The drying in step (3) is drying in an oven.

7. A modified aramid nanofiber, characterized by, The modified aramid nanofibers are prepared by the method of any one of claims 1-6.

8. The use of the modified aramid nanofibers of claim 7 in the preparation of pipes, plates, grouting equipment parts and grouting bags.

9. A polyolefin composite material, characterized by, The composition comprises the following components by weight: 50-150 parts of polyolefin resin, 1-30 parts of the modified aramid nanofibers of claim 7, 1-30 parts of inorganic fiber reinforcing filler and 1-10 parts of processing aid.

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