A method for preparing powdered modified aramid nanocomposite filler and its application

Abstract

This invention provides a powdered modified aramid nanofiber filler, its preparation method, and its application, belonging to the field of composite material technology. The method provided by this invention first adds a water-soluble polymer to a solvent, then adds nano-aramid fiber hydrogel to the solution, and finally adds alkoxysilane compounds and silicate ester compounds respectively to obtain a powdered modified aramid nanocomposite filler with surface-grafted functionalized silica nanoparticles. The modified aramid nanocomposite filler prepared by this invention is a powdered solid filler, which is relatively easy to industrialize and can be used as a nanocomposite filler for polymer composites. The prepared modified aramid nanocomposite filler / polymer composite material not only effectively improves the problem of difficult dispersion of aramid nanofibers in polymers, but more importantly, it improves the physical and mechanical properties of the composite material.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and particularly relates to a powdered modified aramid nanofiber filler, its preparation method, and its application. Background Technology

[0002] Aramid nanofibers possess the structural characteristics of high aspect ratio and high specific surface area, while retaining the excellent mechanical, chemical resistance, and thermal durability properties of poly(p-phenylene terephthalamide) (PPTA) fibers. As one of the most prominent reinforcing materials in various high-performance polymer composites used in aerospace, bulletproof materials, and building materials, it has attracted significant attention in the field of nanocomposites and has been widely used in polymer composite reinforcement, high-performance aerospace, and military equipment materials research and applications.

[0003] While aramid nanofibers possess nanoscale structural advantages, their chemical inertness due to the highly oriented internal molecular chains and the strong interactions between aromatic rings via π-π stacking and conjugation presents challenges for modification. Uniform dispersion of aramid nanofibers in the matrix is ​​limited, with a tendency for aggregation, hindering the complete restoration of their nanoscale morphology. Furthermore, the lack of effective filler-matrix interaction between the fibers and the matrix, i.e., weak interfacial bonding between aramid nanofibers and the matrix, leads to poor mechanical properties of the composite material. Therefore, increasing the contact area between the fibers and the matrix to achieve good dispersion within the polymer matrix and improve the interfacial properties of the composite material are current problems that need to be addressed. Summary of the Invention

[0004] The purpose of this invention is to provide a powdered modified aramid nanofiber filler, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] First, the present invention provides a method for preparing a powdered modified aramid nanocomposite filler, the method comprising the following steps:

[0007] (1) Add the water-soluble polymer to solvent A, stir to dissolve, and obtain mixed solution A;

[0008] (2) Add the aramid nanofiber hydrogel to the mixed solution A, add alkoxysilane compounds during stirring, and continue stirring until the mixture is homogeneous to obtain mixed solution B;

[0009] (3) After dispersing the silicate compound in solvent B, add it to the mixed solution B and continue stirring to react, to obtain a dispersion of modified aramid nanocomposite filler with grafted functionalized silica nanoparticles.

[0010] (4) After vacuum-assisted filtration of the modified aramid nanocomposite filler dispersion, the solid obtained is washed and placed in a vacuum oven for drying to obtain powdered modified aramid nanocomposite filler.

[0011] Preferably, for every 20-56g of the water-soluble polymer, the amount of solvent A used is 50-500mL, the amount of aramid nanofiber hydrogel used is 1.54-15.5g, the amount of alkoxysilane compound used is 4-35mL, the amount of silicate compound used is 1.7-20mL, and the amount of solvent B used is 0.9-8.5mL.

[0012] Preferably, in step (1), the water-soluble polymer is at least one of strongly hydrophilic polymers containing polar nonionic groups;

[0013] The aramid nanofibers in the aramid nanofiber hydrogel have a diameter of 10-300 nm and a content of 1-10 wt%.

[0014] Solvent A is at least one selected from deionized water, ethanol, propanol, acetone, butanone, tetrahydrofuran, n-butanol, ethyl acetate, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0015] Preferably, the strongly hydrophilic polymer includes one or more of polyethylene glycol monomethyl ether, polyethylene glycol, polyoxyethylene, and polyvinylpyrrolidone.

[0016] Preferably, in step (2), the alkoxysilane compound is one or a mixture of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane;

[0017] Preferably, in step (3), the silicate ester compound is one or a mixture of tetraethyl orthosilicate, butyl orthosilicate, propyl orthosilicate and isopropyl orthosilicate;

[0018] Solvent B is one or a mixture of deionized water, ethanol, propanol, acetone, butanone, tetrahydrofuran, n-butanol, ethyl acetate, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0019] Preferably, in step (3), the device is a mechanical stirring device, the stirring reaction time is 0.5-8 hours, and the reaction temperature is room temperature-60℃.

[0020] Secondly, the present invention provides a powdered modified aramid nanocomposite filler, which is prepared by the above-described preparation method.

[0021] This invention provides the application of powdered modified aramid nanocomposite filler in the preparation of modified polymer composite materials, wherein the polymer in the modified polymer composite material is one or more of polar or non-polar polymers.

[0022] Preferably, the polymer is one or more of polymers containing benzene rings or polar groups.

[0023] Preferably, the polymer is at least one of polymers containing a benzene ring, ester group, ether group, hydroxyl group, cyano group, amide group, halogen group, carboxyl group, and carbonate group.

[0024] Preferably, the polymer is one or a mixture of styrene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, acrylate rubber, ethylene-vinyl acetate rubber, polycarbonate, polyurethane, polytetrafluoroethylene, epoxy resin, and polyvinyl alcohol.

[0025] Preferably, the application involves mixing the modified aramid nanofiber composite filler with a polymer and then vulcanizing (hot pressing) the mixture to obtain a modified aramid nanofiber / polymer composite material with significantly improved tensile strength and tensile stress.

[0026] Alternatively, the application may involve mixing the modified aramid nanofiber composite filler with polymers and silica, followed by vulcanization (hot pressing) to obtain a modified aramid nanofiber / silica reinforced polymer composite material with significantly improved tensile strength, tensile stress at a given elongation, and abrasion resistance.

[0027] The beneficial effects of this invention are as follows:

[0028] This invention provides a method for preparing powdered filler-modified aramid nanofibers. This method uses functionalized silica nanoparticles to modify the aramid nanofibers. Through silica enhancement, the aramid nanofibers and polymer interfacial interaction is strengthened, allowing them to function as nanofillers and form good dispersion in the polymer matrix. This overcomes the problems of ordinary aramid nanofibers, which cannot be directly mechanically blended and are prone to agglomeration and uneven dispersion in polymers. Applied to the preparation of polymer composites, this method improves the physical and mechanical properties of polymer materials. For example, adding 5 phr of modified aramid nanocomposite filler increases the tensile strength of the composite material by 1200% and the 300% constant elongation stress by 1357% compared to the polymer without modified aramid nanocomposite filler. Adding only 2.5 phr of modified aramid nanocomposite filler to a silica-reinforced polymer matrix increases the tensile strength of the composite material by 30%, the 300% constant elongation stress by 58%, and the DIN abrasion resistance by 25% compared to the silica-reinforced polymer. Attached Figure Description

[0029] Figure 1 TEM images of (a) aramid nanofibers before modification and (b) the modified aramid nanocomposite filler a in Example 1;

[0030] Figure 2 Photographs of (a) aramid nanofiber hydrogel and (b) the modified aramid nanocomposite filler b in Example 2;

[0031] Figure 3 Thermogravimetric analysis diagrams of aramid nanofibers and modified aramid nanocomposite filler b in Example 2;

[0032] Figure 4 SEM images of the polymer composites in (a) Example 6 and (b) Comparative Example 2;

[0033] Figure 5 This is a cross-sectional electron micrograph of the aramid nanofiber / rubber composite compound 1 in Comparative Example 3. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0035] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0036] In this invention, "aramid nanofibers" include meta-aramid fibers and para-aramid fibers, which may or may not contain other comonomers.

[0037] Para-aramid, also known as poly(p-phenylene terephthalamide) (PPTA) or aramid 1414, is a linear polymer in which more than 85% of the amide bonds in the molecular chain are directly bonded to the aromatic ring. It has a simple, symmetrical, and regularly arranged structure with a diameter between 10 and 100 nm and an aspect ratio of approximately 3000. Besides possessing high strength, high modulus, high temperature resistance, and corrosion resistance, it also exhibits a large specific surface area, high surface energy, good dispersibility, high water retention, and excellent flame retardant properties. Due to its superior properties, para-aramid nanofibers have broad application prospects in composite reinforcement, battery separators, adsorption filtration, electrical insulation, and flexible electrodes.

[0038] Meta-aramid, also known as poly(m-phenylene isophthalamide) (PMTA) or aramid 1313, is the fastest-growing type of organic high-temperature resistant fiber. Its fibers are composed of amide groups linked together at meta-phenyl positions, resulting in linear zigzag-shaped molecular chains with low density and orientation. Therefore, its strength and modulus are lower than para-aramid. However, due to strong intermolecular hydrogen bonding, the fiber exhibits excellent flame retardancy, thermal stability, and radiation resistance.

[0039] In this invention, "aramid nanofiber hydrogel" refers to a hydrogel structure formed by aramid nanofibers, wherein the content of aramid nanofibers is 2 to 5 wt%. This hydrogel structure can be directly generated during the in-situ synthesis of aramid nanofibers, or it can be a hydrogel formed by dry aramid fibers through technical means.

[0040] The materials used in this invention are listed in Table 1:

[0041] Table 1. Basic Raw Materials Used in This Invention

[0042]

[0043] The analysis and testing performed in this invention are as follows:

[0044] TEM testing: The microstructure of the nanofibers was tested using a JEM-2100 transmission electron microscope (manufactured by JEOL Ltd, Japan).

[0045] TGA testing: Thermogravimetric analysis was performed using a TGA 2 thermogravimetric analyzer (manufactured by METTLER TOLEDO Ltd, USA), with a heating rate of 10 K / min, a temperature range of room temperature to 900 °C, and a nitrogen atmosphere.

[0046] SEM testing: The scanning electron microscopy spectra of the polymer composite material were determined using a JSM7500F scanning electron microscope (manufactured by JEOL Ltd., Japan). The test sample was a brittle fracture surface of a tensile specimen.

[0047] Polymer tensile strength test: The tensile strength of polymer composites was measured using a Model Z005 electronic tensile testing machine (manufactured by Zwick Ltd, Germany) in accordance with DIN 53504 standard, at a tensile speed of 500 mm / min and at room temperature.

[0048] Example 1

[0049] Preparation of modified aramid nanofiber composite filler a

[0050] (1) Add 56g of polyethylene glycol monomethyl ether to 300mL of n-butanol and stir at 30℃ and 500rpm for 30 minutes to obtain mixed solution A1;

[0051] (2) Add 15.5g of para-aramid nanofiber hydrogel (aramid nanofiber solid content is 3%) to mixed solution A1, add 20mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane during stirring, and continue stirring for 1 hour to obtain mixed solution B1.

[0052] (3) After dispersing 10 mL of tetrabutyl orthosilicate in 5 mL of n-butanol solvent, it was added to mixed solution B1 to obtain functionalized silica nanoparticles. After stirring for 6 hours, a modified aramid composite filler dispersion of grafted functionalized silica nanoparticles was obtained.

[0053] (4) Vacuum-assisted filtration, wash twice with ethanol and once with deionized water, and dry in a vacuum oven for 8 hours to obtain powdered modified aramid nanocomposite filler a.

[0054] The powdered modified aramid nanocomposite filler a prepared by the method of the present invention exhibits a highly dispersed state of ultrafine particles.

[0055] First, the differences between aramid nanofibers before and after modification were examined using transmission electron microscopy, and the results are as follows: Figure 1 As shown.

[0056] from Figure 1 It can be seen that on the modified aramid nanocomposite filler a, silica nanoparticles are uniformly distributed on the surface of aramid nanofibers.

[0057] Next, the modified aramid nanofiber powder filler was subjected to thermogravimetric analysis, and the silica content was found to be 28.8 wt%.

[0058] Example 2

[0059] Preparation of modified aramid nanofiber composite filler b

[0060] (1) Add 50g of polyethylene glycol to 300mL of ethanol and stir at 30℃ and 500rpm for 30 minutes to obtain mixed solution A2.

[0061] (2) Add 9.26g of para-aramid nanofiber hydrogel (aramid nanofiber solid content is 3%) to mixed solution A2, add 18mL of γ-aminopropyltriethoxysilane during stirring, and continue stirring for 1 hour to obtain mixed solution B2;

[0062] (3) After dispersing 10 mL of tetraethyl orthosilicate in 5 mL of ethanol solvent, it was added to mixed solution B2 to obtain functionalized silica nanoparticles. After stirring for 6 hours, a modified aramid nanocomposite filler dispersion of grafted functionalized silica nanoparticles was obtained.

[0063] (4) Vacuum-assisted filtration, washing twice with ethanol and once with deionized water, and drying in a vacuum oven for 8 hours to obtain powdered modified aramid nanocomposite filler b.

[0064] The powdered modified aramid nanocomposite filler b prepared by this invention is as follows: Figure 2 As shown in (b).

[0065] Next, the present invention performs thermogravimetric analysis on the modified aramid nanofiber powder filler, such as... Figure 3 As shown, the obtained silica content is 31.6 wt%.

[0066] Example 3

[0067] Preparation of modified aramid nanofiber composite filler c

[0068] (1) Add 20g of polyvinyl alcohol to 50mL of propanol and stir at 30℃ and 500rpm for 30 minutes to obtain mixed solution A3.

[0069] (2) Add 1.54 g of para-aramid nanofiber hydrogel (aramid nanofiber solid content is 3%) to mixed solution A3, add 4 mL of γ-methacryloxypropyltrimethoxysilane during stirring, and continue stirring for 1 hour to obtain mixed solution B3.

[0070] (3) After dispersing 1.7 mL of propyl orthosilicate in 0.9 mL of propanol solvent, it was added to mixed solution B3 to obtain functionalized silica nanoparticles. After stirring for 6 hours, a modified aramid nanocomposite filler dispersion of grafted functionalized silica nanoparticles was obtained.

[0071] (4) Vacuum-assisted filtration, washing twice with ethanol and once with deionized water, and then obtaining modified aramid nanocomposite filler c after filtration.

[0072] The present invention performs thermogravimetric analysis on powdered modified aramid nanocomposite filler c, and the silica content is found to be 28.2 wt%.

[0073] Example 4

[0074] Preparation of modified aramid nanofiber composite filler d

[0075] (1) Add 35g of polyvinylpyrrolidone to 500mL of dimethylformamide and stir at 30℃ and 500rpm for 30 minutes to obtain mixed solution A4.

[0076] (2) 15.5g of meta-aramid nanofiber hydrogel (aramid nanofiber solid content is 3%) was added to 300mL of dimethylformamide. During the stirring process, 35mL of γ-mercaptopropyltriethoxysilane was added and the mixture was stirred for 1 hour to obtain mixed solution B4.

[0077] (2) After dispersing 20 mL of tetraethyl orthosilicate in 8.5 mL of dimethylformamide solvent, it was added to mixed solution B4 to obtain silica nanoparticles. After stirring for 6 hours, a modified aramid nanocomposite filler dispersion grafted with silica nanoparticles was obtained.

[0078] (3) Vacuum-assisted filtration, washing twice with ethanol and once with deionized water, and drying in a vacuum oven for 8 hours to obtain powdered modified aramid nanocomposite filler d.

[0079] The present invention uses thermogravimetric analysis of modified aramid nanofiber powder filler to obtain a silica content of 26.9 wt%.

[0080] Example 5

[0081] Preparation of modified aramid nanofiber / rubber composite material 1

[0082] (1) 100 phr of styrene-butadiene rubber, 5 phr of modified aramid nanocomposite filler a, 1 phr of antioxidant 4020, 1 phr of antioxidant RD, 3 phr of zinc oxide and 1 phr of stearic acid were mixed into a mixer at 100±5℃ for 6 minutes to obtain a mixed rubber.

[0083] (2) Mix the intensive rubber and vulcanizing agent (sulfur 2 phr, accelerator CZ 1.6 phr, accelerator D 1.5 phr) in a two-roll mill, and then sheet it after passing it through a thin mill 5 times to obtain the compound rubber;

[0084] (3) The compound is vulcanized at a specific temperature of 90°C and 160°C to obtain vulcanized rubber, i.e. composite material 1.

[0085] The tensile strength test results showed that adding 5 phr of modified aramid nanocomposite filler a to the polymer matrix increased the tensile strength of the composite material by 1200% compared with the polymer without modified aramid nanocomposite filler a, and increased the 300% constant elongation stress by 1357%.

[0086] Example 6

[0087] Preparation of modified aramid nanofiber / rubber composite material 2

[0088] (1) 100 phr styrene-butadiene rubber, 2.5 phr modified aramid nanofiber composite filler a, 1 phr antioxidant 4020, 1 phr antioxidant RD, 3 phr zinc oxide, 1 phr stearic acid, 50 phr silica, 4 phr silane coupling agent Si69 and 10 phr aromatic oil are mixed into a mixer at 100±5℃ and mixed for 6 minutes to obtain a mixed rubber.

[0089] (2) Mix the intensive rubber at 140±5℃ for 5 minutes;

[0090] (3) Mix the intensive rubber and vulcanizing agent (sulfur 2 phr, accelerator CZ 1.6 phr, accelerator D 1.5 phr) in a two-roll mill, and then sheet it after passing it through a thin mill 5 times to obtain the compound rubber;

[0091] (4) The compound is vulcanized at a specific temperature of 90°C and 160°C to obtain vulcanized rubber, i.e. composite material 2.

[0092] The tensile strength test results showed that adding only 2.5 phr of modified aramid nanocomposite filler a to the silica-reinforced polymer matrix increased the tensile strength of the composite material by 30% compared to the silica-reinforced polymer; the 300% constant elongation stress increased by 58%; and the DIN abrasion test results showed that the abrasion resistance was improved by 25%.

[0093] In addition, such as Figure 4 As shown in (a), scanning electron microscopy of the brittle fracture surface of the composite material shows that the modified aramid nanofibers are uniformly dispersed in the polymer matrix, and the interfacial interaction between the fibers and the rubber matrix is ​​improved.

[0094] Example 7

[0095] Preparation of modified aramid nanofiber / rubber composite material 3

[0096] (1) Mix 100 phr nitrile rubber, 5 phr modified aramid nanocomposite filler b, 1 phr antioxidant 4020, 1 phr antioxidant RD, 5 phr zinc oxide and 1 phr stearic acid into a mixer at 100±5℃ and mix for 6 minutes to obtain a mixed rubber.

[0097] (2) Mix the intensive rubber and vulcanizing agent (sulfur 1.5 phr, accelerator DM 1.5 phr) in a two-roll mill, and then sheet it after passing it through a thin mill 5 times to obtain the compound rubber;

[0098] (3) The compound is vulcanized at a specific temperature of 90°C and 160°C to obtain vulcanized rubber, i.e. composite material 3.

[0099] The tensile strength test results showed that adding 5 phr of modified aramid nanocomposite filler b to the polymer matrix increased the tensile strength of the composite material by 1095% and the 300% constant elongation stress by 1136% compared with the polymer without modified aramid nanocomposite filler b.

[0100] Example 8

[0101] Preparation of modified aramid nanofiber / rubber composite material 4

[0102] (1) Mix 100 phr chloroprene rubber, 5 phr modified aramid nanocomposite filler c, 1 phr antioxidant 4020, 1 phr antioxidant RD, 5 phr NA-22 and 1 phr stearic acid into a mixer at 100±5℃ for 6 minutes to obtain a mixed rubber.

[0103] (2) Mix the intensive rubber and vulcanizing agent (magnesium oxide 4 phr, magnesium oxide 5 phr) in a two-roll mill, and then sheet it after passing it through a thin mill 5 times to obtain the compound rubber.

[0104] (3) The compound is vulcanized at a specific temperature of 90°C and 160°C to obtain vulcanized rubber, i.e. composite material 4.

[0105] The tensile strength test results showed that the addition of 5 phr modified aramid nanocomposite filler b to the polymer matrix increased the tensile strength of the composite material by 262% and the 300% constant elongation stress by 553% compared with the polymer without modified aramid nanocomposite filler c.

[0106] Example 9

[0107] Preparation of modified aramid nanofiber / rubber composite material 5

[0108] (1) 100 phr hydrogenated nitrile butadiene rubber, 2.5 phr modified aramid nanofiber composite filler a, 1 phr antioxidant 445, 1 phr antioxidant RD, 5 phr zinc oxide, 1 phr stearic acid, 50 phr silica, 4 phr silane coupling agent Si69 and 10 phr dibutyl phthalate were mixed in a mixer at 100±5℃ for 6 minutes to obtain a mixed rubber.

[0109] (2) Mix the intensive rubber and vulcanizing agent (sulfur 1.5 phr, accelerator DM 2 phr) in a two-roll mill, and then sheet it after passing it through a thin mill 5 times to obtain the compound rubber;

[0110] (3) The compound is vulcanized at a specific temperature of 90°C and 160°C to obtain vulcanized rubber, i.e. composite material 5.

[0111] Tensile strength tests revealed that adding 5 phr of modified aramid nanocomposite filler b to the polymer matrix increased the tensile strength of the composite material by 23% compared to the polymer without modified aramid nanocomposite filler b, increased the 300% constant elongation stress by 36%, and improved abrasion resistance by 15%.

[0112] Example 10

[0113] Preparation of modified aramid nanofiber / rubber composite material 6

[0114] (1) Mix 50 phr polyisocyanate (component A), 50 phr polyether polyol (component B), 2 phr modified aramid nanocomposite filler d, antioxidant 4020 (1 phr), and antioxidant RD (1 phr) into a mixer at 100±5℃ for 6 minutes to obtain a mixed rubber.

[0115] (2) The viscous rubber was pressed into sheets at room temperature and cured to obtain polyurethane composite material 6.

[0116] The tensile strength test results showed that adding 2 phr of modified aramid nanocomposite filler d to the polymer matrix increased the tensile strength of the composite material by 353% compared with the polymer without modified aramid nanocomposite filler d, increased the 300% constant elongation stress by 475%, and improved the wear resistance by 310%.

[0117] Example 11

[0118] Preparation of modified aramid nanofiber / resin composite materials 7

[0119] (1) Mix 100 phr epoxy resin, 2 phr modified aramid nanocomposite filler b and antioxidant 1010 into a mixer at 160±5℃ for 6 minutes to obtain a mixture;

[0120] (2) The mixture was pressed into tablets at 160°C for 10 min to obtain epoxy resin composite material 7.

[0121] The tensile strength test results showed that adding 2.5 phr of modified aramid nanocomposite filler a to the polymer matrix increased the tensile strength of the composite material by 33% and improved the wear resistance by 21% compared with the epoxy resin polymer without modified aramid nanocomposite filler a.

[0122] Comparative Example 1

[0123] Preparation of modified aramid nanofiber composite filler e

[0124] (1) Add 9.26g of aramid nanofiber hydrogel to n-butanol, and add 20mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane while stirring. Continue stirring for 1 hour to obtain mixed solution A5.

[0125] (2) After dispersing 10 mL of tetrabutyl orthosilicate in 5 mL of n-butanol solvent, it was added to mixed solution B5 to obtain functionalized silica nanoparticles. After stirring for 6 hours, a modified aramid composite filler dispersion of grafted functionalized silica nanoparticles was obtained.

[0126] (3) Vacuum-assisted filtration, wash twice with ethanol and once with deionized water, and dry in a vacuum oven for 8 hours to obtain powdered modified aramid nanocomposite filler e.

[0127] No water-soluble polymers were added during the preparation of Comparative Example 1.

[0128] Comparative Example 2

[0129] Preparation of aramid nanocomposite fillers f

[0130] (1) Add 56g of polyethylene glycol monomethyl ether to 300mL of n-butanol and stir at 30℃ and 500rpm for 30 minutes to obtain mixed solution A6.

[0131] (2) Add 9.26g of aramid nanofiber hydrogel to the mixed solution A6, filter under vacuum, wash twice with ethanol and once with deionized water, and dry in a vacuum oven for 8 hours to obtain blocky aramid nanocomposite filler f.

[0132] Because no alkoxysilane compounds and silicate ester compounds were added during the preparation process of Comparative Example 2, the bulk aramid nanocomposite filler f prepared by the method of the present invention exhibits ultra-high hardness, cannot form a powder sample, and cannot be dispersed through subsequent mixing and processing.

[0133] Comparative Example 3

[0134] Preparation of aramid nanofiber / rubber composite material 1

[0135] (1) 100 phr styrene-butadiene rubber, 25 phr unmodified aramid nanofiber hydrogel (solid content 3%, i.e. containing 0.75 phr pure aramid nanofiber), 1 phr antioxidant 4020, 1 phr antioxidant RD, 3 phr zinc oxide, 1 phr stearic acid, 50 phr silica, 4 phr silane coupling agent Si69 and 10 phr aromatic oil are mixed in a mixer at 100±5℃ for 6 minutes to obtain a mixed rubber.

[0136] (2) Mix the intensive rubber at 140±5℃ for 5 minutes;

[0137] (3) Mix the intensive rubber and vulcanizing agent in a two-milling machine, and then sheet it after passing it through a thin mill 5 times to obtain the compound rubber.

[0138] (4) The compound is vulcanized at a specific temperature of 90°C and 160°C to obtain vulcanized rubber, namely aramid nanofiber / rubber composite material 1.

[0139] like Figure 5 As shown, aramid nanofiber aggregates are clearly visible to the naked eye inside the compound. Unmodified aramid nanofibers cannot be uniformly mixed and dispersed in the polymer matrix through conventional mixing methods.

[0140] Comparative Example 4

[0141] Preparation of modified aramid nanofiber / rubber composite materials 7

[0142] (1) 100 phr styrene-butadiene rubber, 2.5 phr modified aramid nanofiber composite filler e, 1 phr antioxidant 4020, 1 phr antioxidant RD, 3 phr zinc oxide, 1 phr stearic acid, 50 phr silica, 4 phr silane coupling agent Si69 and 10 phr aromatic oil are mixed into a mixer at 100±5℃ and mixed for 6 minutes to obtain a mixed rubber.

[0143] (2) Mix the intensive rubber at 140±5℃ for 5 minutes;

[0144] (3) Mix the intensive rubber and vulcanizing agent in a two-milling machine, and then sheet it after passing it through a thin mill 5 times to obtain the compound rubber.

[0145] (4) The compound is vulcanized at a specific temperature of 90°C and 160°C to obtain vulcanized rubber, i.e. composite material 7.

[0146] The tensile strength test results showed that adding 2.5 phr of modified aramid nanocomposite filler e to the fumed silica-reinforced polymer matrix increased the tensile strength of the composite material by 5.3%, the 300% constant elongation stress by 7.1%, and the DIN abrasion by 4.2% because no water-soluble polymer was added during the preparation of the modified aramid nanocomposite filler e.

[0147] like Figure 4As shown in (b), scanning electron microscopy of the brittle fracture surface of the composite material reveals that although the dispersion of modified aramid nanofibers in the polymer matrix is ​​improved, there are some interfacial interaction defects, resulting in insignificant performance improvement.

[0148] In summary, through the comparison of the examples and comparative examples, it can be clearly observed that the powdered modified aramid nanocomposite filler prepared by the modification method of this invention overcomes the chemical inertness of aramid nanofibers and improves the aggregation problem of aramid nanofibers. Secondly, in the obtained modified aramid nanocomposite filler / polymer composite material, the modified aramid nanofibers exhibit excellent dispersibility, and the interfacial bonding between the modified aramid nanofibers and the polymer composite material is significantly enhanced. Furthermore, the physical and mechanical properties of the polymer composite material are significantly improved by adding a small amount of modified aramid nanocomposite filler.

Claims

1. A method for preparing powdered modified aramid nanocomposite filler, characterized in that, The preparation method of the powdered modified aramid nanocomposite filler includes the following steps: (1) Add the water-soluble polymer to solvent A, stir to dissolve, and obtain mixed solution A; (2) Add the aramid nanofiber hydrogel to the mixed solution A, add alkoxysilane compounds during stirring, and continue stirring until uniform to obtain mixed solution B; (3) After dispersing the silicate compound in solvent B, add it to the mixed solution B and continue stirring to obtain a dispersion of modified aramid nanocomposite filler with grafted functionalized silica nanoparticles. (4) After vacuum-assisted filtration of the modified aramid nanocomposite filler dispersion, the solid obtained is washed and placed in a vacuum oven for drying to obtain powdered modified aramid nanocomposite filler. The aramid nanofibers in the aramid nanofiber hydrogel have a diameter of 10-300 nm and a content of 1-10 wt%. The combination of the water-soluble polymer, solvent A, aramid nanofiber hydrogel, alkoxysilane compound, silicate ester compound, and solvent B is selected from any one of the following: (a) 56g polyethylene glycol monomethyl ether, 300mL n-butanol, 15.5g para-aramid nanofiber hydrogel, 20mL γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 10mL tetrabutyl orthosilicate and 5mL n-butanol; (b) 50g polyethylene glycol, 300mL ethanol, 9.26g para-aramid nanofiber hydrogel, 18mL γ-aminopropyltriethoxysilane, 10mL tetraethyl orthosilicate and 5mL ethanol; (c) 20g polyvinyl alcohol, 50mL propanol, 1.54g para-aramid nanofiber hydrogel, 4mL γ-methacryloyloxypropyltrimethoxysilane, 1.7mL propyl orthosilicate and 0.9mL propanol; (d) 35g polyvinylpyrrolidone, 500mL dimethylformamide, 15.5g meta-aramid nanofiber hydrogel, 35mL γ-mercaptopropyltriethoxysilane, 20mL tetraethyl orthosilicate and 8.5mL dimethylformamide; In step (1), the water-soluble polymer is stirred at 30°C and 500 rpm for 30 minutes to obtain mixed solution A; in step (2), after adding alkoxysilane compounds, stirring is continued for 1 hour to obtain mixed solution B; in step (3), after adding silicate ester compounds, stirring is carried out for 6 hours; in step (4), the washing is carried out by washing twice with ethanol and once with deionized water, and the vacuum oven drying time is 8 hours.

2. A powdered modified aramid nanocomposite filler, characterized in that, The powdered modified aramid nanocomposite filler is prepared by the preparation method described in claim 1.

3. The application of the powdered modified aramid nanocomposite filler as described in claim 2 in the preparation of modified polymer composite materials, characterized in that, The polymer in the modified polymer composite material is styrene-butadiene rubber, nitrile rubber, chloroprene rubber, hydrogenated nitrile rubber, polyurethane, or epoxy resin.

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