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CN-121992650-A - Modified aramid nanofiber/rubber composite material and preparation method thereof

CN121992650ACN 121992650 ACN121992650 ACN 121992650ACN-121992650-A

Abstract

The invention discloses a modified aramid nanofiber/rubber composite material and a preparation method thereof, wherein an aramid nanofiber with good water dispersibility is prepared through epoxy modification, the effect of in-situ polycondensation of silicate compounds on the surface of the nanofiber is improved through nucleophilic substitution reaction of epoxy groups and amino groups, ANFs@SiO 2 is formed, and the composite material with excellent physical and mechanical properties and ablation resistance can be obtained through reinforcing rubber by using lower parts by weight of ANFs@SiO 2 . In the ablation process, the nano silicon dioxide is firstly melted to form a protective film to cover the surface of the aramid nanofiber, so that the aramid nanofiber is prevented from being corroded and decomposed by heat flow, and ceramic structures such as SiC, si 3 N 4 and the like are generated in situ to promote densification of the carbon layer, and the ablation resistance of the rubber is obviously enhanced.

Inventors

  • JIA HONGBING
  • FU QUANSHENG
  • YANG ZIFAN
  • ZHAO DONGWEI
  • DENG JIAJIA
  • SONG XIAO

Assignees

  • 南京理工大学

Dates

Publication Date
20260508
Application Date
20241107

Claims (10)

  1. 1. The preparation method of the aramid nanofiber with the nano silicon dioxide grown on the surface in situ is characterized by comprising the following steps of: Step one, adding an epoxy modifier into dimethyl sulfoxide dispersion liquid of aramid nanofiber under the stirring condition, and dialyzing with deionized water until the pH value is 7 to obtain epoxy modified aramid nanofiber (m-ANFs) aqueous dispersion liquid; Step two, adding a silane coupling agent into the m-ANFs aqueous dispersion in the step one at a certain temperature, stirring and reacting for a period of time, filtering and washing to obtain modified aramid nanofiber (mk-ANFs), and re-dispersing in an aqueous solution to obtain mk-ANF aqueous dispersion; And thirdly, adding an ethanol solution of silicate compounds into the mk-ANF aqueous dispersion, stirring and reacting for a period of time at a certain temperature, and carrying out suction filtration and washing to obtain the aramid nanofiber of which the surface grows nano silicon dioxide in situ, namely ANFs@SiO 2 .
  2. 2. The method of claim 1, wherein in the first step, the epoxy modifier is epichlorohydrin or epibromohydrin, the mass ratio of the aramid nanofibers to the epoxy modifier is 1:0.5-1:1, and the stirring time is 12-24h.
  3. 3. The method of claim 1, wherein in the second step, the silane coupling agent is a primary amino group-containing silane coupling agent, and is one of gamma-aminopropyl triethoxysilane, gamma-aminopropyl trimethoxysilane, N-beta (aminoethyl) -gamma-aminopropyl trimethoxysilane and N-beta (aminoethyl) -gamma-aminopropyl triethoxysilane, the mass ratio of the aramid fiber to the silane coupling agent is 1:0.5-1:1, the stirring reaction temperature is 60-80 ℃, and the stirring reaction time is 4-6 h.
  4. 4. The method of claim 1, wherein in the third step, the silicate compound is one of methyl orthosilicate, ethyl orthosilicate and bis (trimethoxy silicon-based) ethane, the mass ratio of the aramid nanofiber to the silicate compound is 1:2-1:4, the stirring reaction temperature is 60-80 ℃, and the stirring reaction time is 4-6 h.
  5. 5. An anfs@sio 2 prepared by the method of any one of claims 1-4.
  6. 6. The ANFs@SiO 2 /rubber ablation-resistant composite material is characterized by comprising, by weight, 100 parts of rubber, 3-7 parts of ANFs@SiO 2 prepared by the method according to any one of claims 1-4, 1-2 parts of a silane coupling agent, 4-6 parts of zinc oxide, 1-3 parts of stearic acid, 20-30 parts of a flame retardant filler, 1-2 parts of a vulcanization accelerator and 3-6 parts of a vulcanizing agent.
  7. 7. The anfs@sio 2 /rubber ablation resistant composite material of claim 6, wherein the rubber is one of ethylene propylene diene monomer rubber, nitrile rubber or silicone rubber.
  8. 8. The ANFs@SiO 2 /rubber ablation-resistant composite material according to claim 6, wherein the flame retardant filler is a mixture of one of zinc borate, zirconium oxide and zirconium silicide and benzoxazine resin, and the mass ratio of the flame retardant filler to the benzoxazine resin is 1:0.5-1.5.
  9. 9. The ANFs@SiO 2 /rubber ablation resistant composite material according to claim 6, wherein the vulcanizing agent is a mixture of sulfur and one of di-tert-butyl cumene peroxide and dicumyl peroxide, and the mass ratio of the vulcanizing agent to the sulfur is 1:0.5-1.
  10. 10. A method for preparing an anfs@sio 2 /rubber composite material according to any one of claims 6-9, comprising the steps of: uniformly dispersing the ANFs@SiO 2 in water, blending with rubber under the stirring condition to obtain a pre-dispersion, and removing a solvent to obtain an ANFs@SiO 2 /rubber masterbatch; Step two, sequentially placing ANFs@SiO 2 /rubber masterbatch, zinc oxide, stearic acid, flame retardant filler, coupling agent, vulcanization accelerator and vulcanizing agent into an open mill for blending to obtain ANFs@SiO 2 /rubber compound; and thirdly, standing the ANFs@SiO 2 /rubber compound at room temperature for a period of time, and vulcanizing and forming to obtain vulcanized rubber, namely the ANFs@SiO 2 /rubber ablation-resistant composite material.

Description

Modified aramid nanofiber/rubber composite material and preparation method thereof Technical Field The invention belongs to the field of rubber composite materials, and relates to a modified aramid nanofiber and application thereof in rubber. Background Thermal protection materials are an important component of aerospace vehicles. However, preparing a thermal protection material with light weight, excellent mechanical properties, high temperature resistance and ablation resistance remains a difficult problem. Rubber is considered to be a good matrix for ablation-resistant composite materials because of its good thermal stability, low density and excellent ablation resistance, and has great potential in the application field of thermal protection layer materials for aerospace vehicles. However, the rubber has poor mechanical properties and low carbon residue rate, and more excellent mechanical strength and ablation resistance can be obtained by adding reinforcing filler. Chinese patent CN118085462a discloses an aramid pulp/ethylene propylene diene monomer composite material and a preparation method thereof, the linear ablation rate of the ethylene propylene diene monomer composite material reinforced by using 20 parts of aramid pulp is reduced to 0.118mm/s, however, the tensile strength and elongation at break are only 8.018MPa and 81%. The ablation rate of ethylene propylene diene monomer is reduced by a large amount of aramid pulp, but the mechanical property of the composite material is simultaneously damaged, the density is increased, and the utilization value of the composite material is greatly reduced. Therefore, it is urgent to find a filler that effectively reinforces a rubber-based heat insulating material. The Aramid Nanofiber (ANFs) is a high-performance nanofiber, and has a very strong reinforcing effect on a polymer matrix due to the high length-diameter ratio (diameter 3-30 nm and length 5-10 mu m), high tensile strength (3.6 GPa) and high modulus (90 GPa) with very little consumption. Chinese patent CN108424563a reports an aramid nanofiber/carboxylated nitrile rubber composite material and a preparation method thereof, and after adding 5 parts of aramid nanofibers, the tensile strength and elongation at break of the composite material are increased to 13.12MPa and 128%. At present, the application of the aramid nanofiber is mainly focused on the improvement of the mechanical property of a composite material, and the research of improving the ablation resistance of a thermal protection material has not been reported at present. At present, the report on the rubber-based ablation-resistant composite material is mainly focused on the improvement of the ablation resistance, but the mechanical property is inevitably reduced while the ablation resistance is improved. The difficulty of how to balance ablation rate, tensile strength and elongation at break is a current urgent need for researchers. Disclosure of Invention The invention aims to provide a modified aramid nanofiber, a modified aramid nanofiber/rubber composite material and a preparation method thereof. The invention realizes the aim through the following technical scheme: In a first aspect, the present invention provides a method for preparing an aramid nanofiber (anfs@sio 2) with nano-silica grown on the surface in situ, comprising the steps of: Step one, adding an epoxy modifier into dimethyl sulfoxide dispersion liquid of the aramid nanofiber under the stirring condition, and dialyzing with deionized water until the pH value is 7 to obtain aqueous dispersion liquid of the epoxy modified aramid nanofiber (m-ANFs); Step two, adding a silane coupling agent into the m-ANFs aqueous dispersion in the step one at a certain temperature, stirring and reacting for a period of time to initiate the in-situ growth of subsequent nano silicon dioxide, filtering and washing to obtain modified aramid nanofiber (mk-ANFs), and re-dispersing in an aqueous solution to obtain mk-ANF aqueous dispersion; And thirdly, adding an ethanol solution of silicate compounds into the mk-ANF aqueous dispersion, stirring at a certain temperature for reacting for a period of time, and carrying out suction filtration and washing to obtain the ANFs@SiO 2. In the first step, the epoxy modifier is epichlorohydrin or epibromohydrin, the mass ratio of the aramid nanofiber to the epoxy modifier is 1:0.5-1:1, and the stirring time is 12-24 hours. In the second step, the silane coupling agent is a silane coupling agent containing primary amino, and can be one of gamma-aminopropyl triethoxysilane, gamma-aminopropyl trimethoxysilane, N-beta (aminoethyl) -gamma-aminopropyl trimethoxysilane and N-beta (aminoethyl) -gamma-aminopropyl triethoxysilane, wherein the mass ratio of the aramid fiber to the silane coupling agent is 1:0.5-1:1, the stirring reaction temperature is 60-80 ℃, and the stirring reaction time is 4-6h. In the third step, the silicate compound is one of methyl orthosil