阅读说明：本技术 一种含苯并噁唑二胺相容剂的pbo纤维上浆剂及其应用 (PBO fiber sizing agent containing benzoxazole diamine compatilizer and application thereof ) 是由 吴绍华 李春成 肖耀南 张博 于 2019-11-04 设计创作，主要内容包括：本发明公开了一种含苯并噁唑二胺相容剂的PBO纤维上浆剂及其应用。所述上浆剂由硅烷偶联剂改性SiO-2、苯并噁唑二胺、环氧树脂和有机溶剂组成；上浆剂的质量百分比组成如下：硅烷偶联剂改性SiO-20.1～5％；苯并噁唑二胺0.1～1％；环氧树脂0.5～3％；余量的有机溶剂。与未改性的PBO纤维相比,使用本发明所制备的上浆剂改性后的PBO纤维/环氧树脂复合材料的IFSS可提高55～95％。此外,本发明所用表面处理方法为浸涂法,该方法操作简单、条件温和、不会造成PBO纤维力学性能和热性能的下降,而且可重复性好、易于工业化生产。(The invention discloses a PBO fiber sizing agent containing benzoxazole diamine compatilizer and application thereof. The sizing agent is SiO modified by a silane coupling agent 2 Benzoxazole diamine, epoxy resin and organic solvent; the sizing agent comprises the following components in percentage by mass: silane coupling agent modified SiO 2 0.1-5%; 0.1-1% of benzoxazole diamine; 0.5-3% of epoxy resin; the balance of organic solvent. Compared with the unmodified PBO fiber, the fiber prepared by the inventionIFSS of the prepared sizing agent modified PBO fiber/epoxy resin composite material can be improved by 55-95%. In addition, the surface treatment method adopted by the invention is a dip-coating method, the method is simple to operate, the condition is mild, the mechanical property and the thermal property of the PBO fiber are not reduced, the repeatability is good, and the industrial production is easy to realize.)

1. A sizing agent, which is SiO modified by a silane coupling agent₂The epoxy resin comprises benzoxazole diamine, epoxy resin and an organic solvent.

2. The sizing agent according to claim 1, characterized in that: the sizing agent comprises the following components in percentage by mass:

silane coupling agent modified SiO₂ 0.1～5％；

0.1-1% of benzoxazole diamine;

0.5-3% of epoxy resin;

the balance of organic solvent.

3. The sizing agent according to claim 1 or 2, characterized in that: the silane coupling agent modified SiO₂The preparation method comprises the following steps:

in SiO₂Adding a silane coupling agent into the organic solvent dispersion liquid of the nano particles, and stirring to obtain the nano-particles;

the silane coupling agent is at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane and 3- [2- (2-aminoethylamino) ethylamino ] propyl-trimethoxysilane.

4. The sizing agent according to claim 3, characterized in that: the SiO₂The mass ratio of the nanoparticles to the silane coupling agent is 1:0.5 to 3;

the stirring is carried out under the following conditions:

100～120℃，1～24h。

5. the sizing agent according to any one of claims 1 to 4, characterized in that: the benzoxazole diamine is prepared by the following method:

under the inert atmosphere and in the presence of stannous chloride and polyphosphoric acid, reacting the compound A and the compound B to obtain the compound B;

the reaction conditions were as follows:

heating to 100-140 ℃, stirring for 0.5-2 h, then heating to 150-200 ℃, and continuously stirring for reaction for 1-15 h;

the molar ratio of the compound A to the compound B to the stannous chloride is 1: 2-2.5: 0.1 to 0.3;

the mass content of phosphorus pentoxide in the polyphosphoric acid is 80-85%;

the reactant A is 4, 6-diaminoresorcinol dihydrochloride, 3' -dihydroxybenzidine or 2, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane;

the reactant B is p-aminobenzoic acid or 4-aminosalicylic acid.

6. The sizing agent according to any one of claims 1 to 5, characterized in that: the epoxy resin is at least one of epoxy resin E51, epoxy resin E44, epoxy resin AFG-90, epoxy resin AG-80 and epoxy resin TDE-85;

the organic solvent is any one of acetone, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, toluene, tetrahydrofuran and dichloromethane.

7. Use of the sizing agent of any one of claims 1 to 6 for increasing the interfacial bond strength of a composite of PBO fibers and resin.

8. A PBO fiber/epoxy resin composite material obtained by treating PBO fibers by soaking in the sizing agent according to any one of claims 1 to 6.

9. The composite material of claim 8, wherein: and soaking the PBO fiber in the sizing agent for treatment for 10-120 s, and then drying in vacuum for 1-24 h at 30-150 ℃.

10. The composite material according to claim 8 or 9, characterized in that: before treatment, the PBO fiber surface oiling agent needs to be removed, and the steps are as follows:

soaking the PBO fiber in acetone, and heating and refluxing for 4-48 h at 70-80 ℃; or soaking the PBO fiber in acetone or petroleum ether at room temperature for 12-72 h, and then drying in vacuum at 30-80 ℃ for 1-24 h.

Technical Field

The invention relates to a PBO fiber sizing agent containing a benzoxazole diamine compatilizer and application thereof, belonging to the field of surface and interface modification of materials.

Background

Polyphenylene Benzobisoxazole (PBO) fiber is called 'king of organic fiber' because of its ultrahigh strength and modulus and excellent heat resistance and flame retardance, and the performance characteristics make it one of the most promising resin-based composite material reinforcements. However, the PBO fibers have very smooth surfaces and are very chemically inert, and these disadvantages result in very weak interfacial bonding with the matrix resin, which severely limits the broad application of their composites. Therefore, the surface modification research of the PBO fiber has important scientific significance and practical application value.

To date, numerous methods have been developed to render PBO fibers surface active, including mainly plasma/radiation treatment, coupling agent treatment, copolymerization modification, oxidative etching, chemical grafting, and the like. Among them, the chemical grafting method uses an active material as a bridging agent, and greatly improves the bonding strength between a resin and a fiber by forming a stable chemical bond connection therebetween. Therefore, the chemical grafting method becomes the main method for the functional modification of the PBO fiber at present and is widely researched. However, the harsh grafting conditions and cumbersome grafting procedures tend to deteriorate the mechanical and thermal properties of the PBO fibers, limiting the use of chemical grafting methods. For example, Vesper et al first surface-etched PBO fibers with sulfuric and chloroacetic acids, followed by microwave radiation irradiation to graft a metal-organic framework material on the surface. Although this series of treatments increased the interfacial shear strength (IFSS) of the final composite by 49%, the tensile strength of PBO fibers severely declined from 4.9GPa to 2.4GPa (Zhen hu. construction of anti-ultrasound "shielding fabrics" on poly (p)^- phenylene benzobisoxazole)fibers:metal organic framework-mediated absorption strategy.ACS Applied Materials&Interfaces,2018,10(49): 43262-43274). Therefore, it is still very challenging to find a surface modification method that can efficiently improve the bonding strength between the PBO fiber and the matrix resin without damaging the excellent performance of the PBO fiber.

In recent years, the sizing treatment method has simple operation and conditionsMild, and has no damage to the strength of the fiber body, thereby causing wide attention of people. Contains graphene oxide, carbon nanotubes, and silicon dioxide (SiO)₂) And nanoparticles such as titanium dioxide are sequentially reported for modification of various inorganic/organic fibers. The nano particles are used as an interface reinforcement, on one hand, the roughness and the surface activity of the fiber are increased, and on the other hand, the interface damage energy is absorbed, so that the IFSS of the composite material is improved to a certain extent. However, the IFSS of the composite material still cannot meet the practical application requirements due to the poor dispersibility of the nanoparticles and the lack of interaction force with the fibers.

Disclosure of Invention

The invention aims to provide a sizing agent which can be uniformly dispersed on the surface of PBO fiber, has good compatibility with the PBO fiber and can efficiently improve the bonding strength of the interface of the PBO fiber/epoxy resin composite material, thereby solving the problems of poor dispersibility of the existing nanoparticles on the surface of the PBO fiber and poor compatibility with the PBO fiber.

The sizing agent provided by the invention is SiO modified by a silane coupling agent₂Benzoxazole diamine, epoxy resin and organic solvent;

mixing the components, and then uniformly dispersing by ultrasonic to obtain the product.

In the sizing agent, the sizing agent comprises the following components in percentage by mass:

silane coupling agent modified SiO₂ 0.1～5％；

0.1-1% of benzoxazole diamine;

0.5-3% of epoxy resin;

the balance of organic solvent.

The sizing agent can be any one of the following components in percentage by mass:

1) silane coupling agent modified SiO₂0.1-3%; 0.5-0.8% of benzoxazole diamine; 1.5-2% of epoxy resin; the balance of organic solvent;

2) silane coupling agent modified SiO₂0.1-2%; 0.5-1% of benzoxazole diamine; 0.5-1.5% of epoxy resin; the balance of organic solvent;

3) silane coupling agent modified SiO₂0.1-1%; 0.2-0.5% of benzoxazole diamine; 0.7-1.5% of epoxy resin; the balance of organic solvent;

4) silane coupling agent modified SiO₂1-2%; 0.1-1% of benzoxazole diamine; 0.5-0.7% of epoxy resin; the balance of organic solvent;

5) silane coupling agent modified SiO₂1-3%; 0.2-0.8% of benzoxazole diamine; 0.7-2% of epoxy resin; the balance of organic solvent;

6) silane coupling agent modified SiO₂1-5%; 0.1-0.2% of benzoxazole diamine; 0.7-3% of epoxy resin; the balance of organic solvent;

7) silane coupling agent modified SiO₂0.1 percent; 0.5% of benzoxazole diamine; 1.5 percent of epoxy resin; the balance of organic solvent;

8) silane coupling agent modified SiO₂1 percent; 0.2% of benzoxazole diamine; 0.7 percent of epoxy resin; the balance of organic solvent;

9) silane coupling agent modified SiO₂2 percent; 1% of benzoxazole diamine; 0.5 percent of epoxy resin; the balance of organic solvent;

10) silane coupling agent modified SiO₂3 percent; 0.8% of benzoxazole diamine; 2% of epoxy resin; the balance of organic solvent;

11) silane coupling agent modified SiO₂5 percent; 0.1% of benzoxazole diamine; 3% of epoxy resin; the balance of organic solvent.

In the sizing agent, the silane coupling agent modifies SiO₂The preparation method comprises the following steps:

in SiO₂Adding a silane coupling agent into the organic solvent dispersion liquid of the nano particles, and stirring to obtain the nano-particles;

the SiO₂The particle size of the nanoparticles can be 10-200 nm, specifically 10-150 nm, 10-100 nm, 10-50 nm, 100-150 nm, 50-100 nm, 150-200 nm, 10nm, 50nm, 100nm, 150nm or 200 nm;

the SiO₂The mass ratio of the nanoparticles to the organic solvent may beIs 1:1 to 50, specifically 1: 1-30, 1: 1-20, 1: 1-10, 1: 30-50, 1: 20-50, 1:1. 1: 10. 1: 20. 1:30 or 1: 50;

the silane coupling agent can be at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane and 3- [2- (2-aminoethylamino) ethylamino ] propyl-trimethoxysilane;

the organic solvent may be benzene, toluene, xylene, N-dimethylformamide, N-dimethylacetamide, dichloromethane, chloroform, ethanol, or the like.

In the above sizing agent, the SiO₂The mass ratio of nanoparticles to the silane coupling agent may be 1: 0.5-3, specifically 1: 0.5-2, 1: 0.5-1.5, 1: 0.5-1, 1:0.5, 1:1. 1:1.5, 1:2 or 1: 3;

the stirring is carried out under the following conditions:

100～120℃，1～24h；

after the grafting reaction is completed, the following treatments are carried out:

after centrifugation, it was washed three times with ethanol and dried under vacuum at 80 ℃ for 24 h.

In the sizing agent, the benzoxazole diamine is prepared according to the following method:

under the inert atmosphere and in the presence of stannous chloride and polyphosphoric acid, reacting the compound A and the compound B to obtain the compound B;

the reaction conditions were as follows:

heating to 100-140 ℃, stirring for 0.5-2 h, then heating to 150-200 ℃, and continuously stirring for reaction for 1-15 h;

obtaining a wine red transparent solution after the reaction is finished, and then carrying out the following post-treatment:

pouring the obtained wine red transparent solution into water for precipitation, performing suction filtration, repeatedly washing a filter cake with water until the pH value of the filtrate is close to 6-8, and drying to obtain a crude product; recrystallizing the crude product to obtain the product;

the solvent used for recrystallization can be any one of N-methylpyrrolidone, N-dimethylformamide and N, N-dimethylacetamide, or a mixture of the N-methylpyrrolidone, N-dimethylacetamide and water in any proportion;

the molar ratio of the compound A to the compound B to the stannous chloride is 1: 2-2.5: 0.1 to 0.3;

the mass content of phosphorus pentoxide in the polyphosphoric acid is 80-85%;

the reactant A is 4, 6-diaminoresorcinol dihydrochloride, 3' -dihydroxybenzidine or 2, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane;

the reactant B is p-aminobenzoic acid or 4-aminosalicylic acid.

In the sizing agent, the epoxy resin is at least one of epoxy resin E51, epoxy resin E44, epoxy resin AFG-90, epoxy resin AG-80 and epoxy resin TDE-85;

the organic solvent is any one of acetone, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, toluene, tetrahydrofuran and dichloromethane.

The sizing agent can be used for surface modification of PBO fibers, and improves the interface bonding strength of a composite material of the PBO fibers and resin (epoxy resin).

And soaking the PBO fiber in the sizing agent for treatment to realize surface modification of the PBO fiber, treating for 10-120 s, and then drying in vacuum at 30-150 ℃ for 1-24 h.

Before the sizing modification, the PBO fiber surface oiling agent needs to be removed, and the method can be carried out according to the following steps:

soaking PBO fiber in acetone, and heating and refluxing for 4-48 h at 70-80 ℃; or soaking the PBO fiber in acetone or petroleum ether at room temperature for 12-72 h; and then drying the mixture in vacuum at the temperature of 30-80 ℃ for 1-24 hours to obtain the product.

The invention has the following beneficial effects:

(1) modified SiO in the sizing agent prepared by the invention₂The introduction of the nano particles increases the roughness of the surface of the PBO fiber, improves the surface activity of the PBO fiber, and improves the wettability of matrix resin to the fiber; simultaneous modification of SiO₂The active functional groups on the surface of the nanoparticles mayChemically reacting with the matrix resin to form a chemical bond at the interface; in addition, modified SiO₂The nanoparticles can also initiate surface fibrillation of the PBO fibers upon interfacial debonding, absorbing a significant amount of interfacial failure energy.

(2) The benzoxazole diamine in the sizing agent prepared by the invention has a chemical structure similar to that of PBO fibers, and has active amino or hydroxyl which can chemically react with epoxy resin, and the introduction of the benzoxazole diamine improves the compatibility of an interface phase and the PBO fibers and remarkably improves the interaction force of the interface phase and the PBO fibers.

(3) Compared with the unmodified PBO fiber, the IFSS of the PBO fiber/epoxy resin composite material modified by the sizing agent prepared by the invention can be improved by 55-95%. In addition, the surface treatment method adopted by the invention is a dip-coating method, the method is simple to operate, the condition is mild, the mechanical property and the thermal property of the PBO fiber are not reduced, the repeatability is good, and the industrial production is easy to realize.

Drawings

FIG. 1 is a scanning electron micrograph of unmodified PBO fibers;

FIG. 2 is a scanning electron micrograph of a sized modified PBO fiber prepared according to example 1 of the present invention.

FIG. 3 is a bar graph of IFSS of PBO fiber/epoxy composite before and after sizing modification;

FIG. 4 is a bar graph of tensile strength of PBO fibers before and after sizing modification;

FIG. 5 is a bar graph of extrapolated onset decomposition temperatures of PBO fibers before and after sizing modification.

Detailed Description

The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

IFSS of PBO fibers and a matrix resin before and after the sizing treatment was measured by a composite interface performance evaluation apparatus (HM-410, manufactured by Tortoise industries, Japan) and the measurement results are shown in FIG. 3.

According to ASTM-D3379 Standard "tensile Strength and Young's modulus test method for high modulus monofilament Material", a microcomputer controlled electronic tensile tester was used to test the tensile strength of the monofilaments of the PBO fibers before and after the sizing agent treatment, and the test results are shown in FIG. 4.

The thermal weight loss behavior of the PBO fiber before and after the sizing agent treatment in a nitrogen atmosphere is tested by a thermogravimetric analyzer (Perkin-Emler TGA 8000), and the temperature range is determined: the room temperature is 800 ℃, the heating rate is 20 ℃/min, and the test result of the extrapolated initial thermal decomposition temperature is shown in figure 5.

Examples 1,

(1) Silane coupling agent modified SiO₂

Drying SiO with particle diameter of 10nm₂Mixing the nanoparticles with anhydrous toluene at a mass ratio of 1:20, stirring at 120 deg.C for 0.5 hr to obtain a dispersion, and adding gamma-glycidoxypropyltrimethoxysilane (SiO 2)₂The mass ratio of the nano particles to the gamma-glycidoxypropyltrimethoxysilane is 1:3, and the mixed solution is continuously stirred at 100 ℃ for 12 hours to complete the grafting reaction. Centrifuging the product, washing with ethanol for three times, and vacuum drying at 80 deg.C for 24 hr to obtain modified SiO₂Nanoparticles.

(2) Synthesis of benzoxazole diamine compatibilizers

Adding 4, 6-diaminoresorcinol dihydrochloride, p-aminobenzoic acid and stannous chloride into polyphosphoric acid, wherein the molar ratio of the 4, 6-diaminoresorcinol dihydrochloride to the p-aminobenzoic acid to the stannous chloride is 1:2:0.1, and the phosphorus pentoxide content in the polyphosphoric acid is 82 wt%; n is a radical of₂Slowly heating to 100 ℃ under protection, stirring for 2h, then heating to 180 ℃, and continuously stirring for reaction for 7h to obtain a wine red transparent solution; pouring the solution into water for precipitation, performing suction filtration, repeatedly washing a filter cake with water until the pH value of the filtrate is close to 6-8, and drying to obtain a crude product; and recrystallizing the crude product by using N, N-dimethylformamide as a solvent to obtain the benzoxazole diamine.

(3) Modified SiO₂Preparation of benzoxazole diamine/epoxy sizing agent

Taking 2 percent of modified SiO by mass percentage₂Nanoparticles, 1% benzoxazole diamine, 0.5% E51 and 96.5%% of acetone and evenly dispersing by ultrasonic to obtain the sizing agent.

Carrying out PBO fiber surface modification on the prepared sizing agent:

firstly, removing a PBO fiber surface oiling agent: PBO fiber is soaked in acetone, heated and refluxed for 48h at 70 ℃, and then dried in vacuum for 24h at 30 ℃ to obtain the PBO fiber with the oil removed. And then soaking the PBO fiber after the oil agent is removed into a slurry tank filled with a sizing agent for treatment for 10s, and then carrying out vacuum drying at 30 ℃ for 24h to obtain the sizing modified PBO fiber.

The surface roughness of the sized PBO fibers (as shown in FIG. 2) was significantly increased compared to the unmodified fibers (as shown in FIG. 1), and the SiO was significantly increased₂The nanoparticles and the benzoxazole diamine compatilizer can be uniformly dispersed on the surface of the fiber (as can be seen from figure 2, the surface of the sized PBO fiber is coated with a layer of nanoparticles, the particle size is uniform, the nanoparticles are continuously distributed on the surface of the fiber, and the particles are made of SiO₂Nanoparticles, benzoxazole diamine, and epoxy resin).

As shown in fig. 3 and 4, the IFSS of the sized modified PBO fiber/epoxy composite material was improved by 94.5%, and the tensile strength and thermal decomposition temperature of the fiber were maintained substantially unchanged.

Examples 2,

(1) Silane coupling agent modified SiO₂

Drying SiO with particle diameter of 200nm₂Mixing the nanoparticles with xylene at a mass ratio of 1:50, stirring at 120 deg.C for 2h to obtain a dispersion, and adding 3-aminopropyltriethoxysilane, wherein SiO is₂The mass ratio of the nano particles to the 3-aminopropyl triethoxysilane is 1:0.5, and the mixed solution is continuously stirred for 1h at 120 ℃ to complete the grafting reaction. Centrifuging the product, washing with ethanol for three times, and vacuum drying at 80 deg.C for 24 hr to obtain modified SiO₂Nanoparticles.

(2) Synthesis of benzoxazole diamine compatibilizers

Adding 3,3 '-dihydroxybenzidine, 4-aminosalicylic acid and stannous chloride into polyphosphoric acid, wherein the 3,3' -dihydroxybenzidine, 4-aminosalicylic acid and stannous chlorideThe molar ratio of the stannous chloride is 1:2.5:0.3, and the content of phosphorus pentoxide in polyphosphoric acid is 85 wt%; n is a radical of₂Slowly heating to 140 ℃ under protection, stirring for 0.5h, then heating to 150 ℃, and continuously stirring for reaction for 15h to obtain a wine red transparent solution; pouring the solution into water for precipitation, performing suction filtration, repeatedly washing a filter cake with water until the pH value of the filtrate is close to 6-8, and drying to obtain a crude product; and recrystallizing the crude product by using N, N-dimethylacetamide as a solvent to obtain the benzoxazole diamine.

(3) Modified SiO₂Preparation of benzoxazole diamine/epoxy sizing agent

Taking 5 percent of modified SiO according to mass percentage₂Mixing the nano particles, 0.1% of benzoxazole diamine, 3% of E44 and 91.9% of N-methyl pyrrolidone, and performing ultrasonic dispersion uniformly to obtain the sizing agent.

Carrying out PBO fiber surface modification on the prepared sizing agent:

firstly, removing a PBO fiber surface oiling agent: soaking the PBO fiber in petroleum ether at room temperature for 72h, and then carrying out vacuum drying at 80 ℃ for 1h to obtain the oil-removed PBO fiber; and then soaking the PBO fiber after the oil agent is removed into a slurry tank filled with a sizing agent for processing for 120s, and then carrying out vacuum drying for 10h at 150 ℃ to obtain the sizing modified PBO fiber.

As shown in fig. 3 and 4, the IFSS of the sized modified PBO fiber/epoxy composite material was improved by 56.1%, and the tensile strength and thermal decomposition temperature of the fiber were maintained substantially unchanged.

Examples 3,

(1) Silane coupling agent modified SiO₂

Drying SiO with particle size of 100nm₂Mixing the nanoparticles with N, N-dimethylacetamide at a mass ratio of 1:1, stirring continuously at 120 deg.C for 1h to obtain a dispersion, and adding a mixture of 3-aminopropyltrimethoxysilane and gamma-glycidoxypropyltrimethoxysilane, wherein SiO is SiO₂The mass ratio of the nano particles to the mixture of the 3-aminopropyl trimethoxy silane and the gamma-glycidoxypropyl trimethoxy silane is 1:1.5, and the mixed solution is continuously stirred at 110 ℃ for 24 hours to complete the grafting reaction. Centrifuging the product to obtainWashing with ethanol for three times, and vacuum drying at 80 deg.C for 24 hr to obtain modified SiO₂Nanoparticles.

(2) Synthesis of benzoxazole diamine compatibilizers

Adding 2, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 4-aminosalicylic acid and stannous chloride into polyphosphoric acid, wherein the molar ratio of the 2, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, the 4-aminosalicylic acid and the stannous chloride is 1:2.2:0.2, and the phosphorus pentoxide content in the polyphosphoric acid is 80 wt%; n is a radical of₂Slowly heating to 120 ℃ under protection, stirring for 1h, then heating to 200 ℃, and continuously stirring for reaction for 1h to obtain a wine red transparent solution; pouring the solution into water for precipitation, performing suction filtration, repeatedly washing a filter cake with water until the pH value of the filtrate is close to 6-8, and drying to obtain a crude product; and recrystallizing the crude product by using N-methylpyrrolidone as a solvent to obtain the benzoxazole diamine.

(3) Modified SiO₂Preparation of benzoxazole diamine/epoxy sizing agent

Taking 0.1 percent of modified SiO according to mass percentage₂Mixing the nano particles, 0.5% of benzoxazole diamine, 1.5% of TDE-85 and 97.9% of toluene, and performing ultrasonic dispersion uniformly to obtain the sizing agent.

Carrying out PBO fiber surface modification on the prepared sizing agent:

firstly, removing a PBO fiber surface oiling agent: soaking the PBO fiber in acetone for 36h at room temperature, and then carrying out vacuum drying for 24h at 30 ℃ to obtain the oil agent-removed PBO fiber; and then soaking the PBO fiber after the oil agent is removed into a slurry tank filled with a sizing agent for treatment for 60s, and then carrying out vacuum drying for 1h at the temperature of 100 ℃ to obtain the sizing modified PBO fiber.

As shown in fig. 3 and 4, the IFSS of the sized modified PBO fiber/epoxy composite material was increased by 74.8%, and the tensile strength and thermal decomposition temperature of the fiber were maintained substantially unchanged.

Examples 4,

(1) Silane coupling agent modified SiO₂

Drying SiO with particle diameter of 50nm₂Mixing the nanoparticles with ethanol at a mass ratio of 1:10, and continuously stirring at 100 deg.C for 0.5h to obtainTo the dispersion solution, followed by addition of 3- [2- (2-aminoethylamino) ethylamino ] ethyl]Propyl-trimethoxysilane, of which SiO₂Nanoparticles with 3- [2- (2-aminoethylamino) ethylamino]The mass ratio of propyl-trimethoxy silane is 1:1, and the mixed solution is continuously stirred for 6 hours at 105 ℃ to complete the grafting reaction. Centrifuging the product, washing with ethanol for three times, and vacuum drying at 80 deg.C for 24 hr to obtain modified SiO₂Nanoparticles.

(2) Synthesis of benzoxazole diamine compatibilizers

Adding 3,3 '-dihydroxybenzidine, p-aminobenzoic acid and stannous chloride into polyphosphoric acid, wherein the molar ratio of the 3,3' -dihydroxybenzidine to the p-aminobenzoic acid to the stannous chloride is 1:2.1:0.2, and the content of phosphorus pentoxide in the polyphosphoric acid is 81 wt%; n is a radical of₂Slowly heating to 110 ℃ under protection, stirring for 1.5h, then heating to 160 ℃, and continuously stirring for reaction for 3h to obtain a wine red transparent solution; pouring the solution into water for precipitation, performing suction filtration, repeatedly washing a filter cake with water until the pH value of the filtrate is close to 6-8, and drying to obtain a crude product; recrystallizing the crude product by using N, N-dimethylformamide/water as a solvent to obtain benzoxazole diamine;

(3) modified SiO₂Preparation of benzoxazole diamine/epoxy sizing agent

Taking 1 percent of modified SiO by mass percentage₂Mixing the nano particles, 0.2% of benzoxazole diamine, 0.7% of a mixture of E51 and AG-80 and 98.1% of tetrahydrofuran, and performing ultrasonic dispersion uniformly to obtain the sizing agent.

Carrying out PBO fiber surface modification on the prepared sizing agent:

firstly, removing a PBO fiber surface oiling agent: soaking PBO fiber in acetone, heating and refluxing for 4h at 80 ℃, and then drying in vacuum for 12h at 60 ℃ to obtain the PBO fiber with the oil removed; and then soaking the PBO fiber after the oil agent is removed into a slurry tank filled with a sizing agent for processing for 30s, and then carrying out vacuum drying for 12h at the temperature of 50 ℃ to obtain the sizing modified PBO fiber.

As shown in fig. 3 and 4, the IFSS of the sized modified PBO fiber/epoxy composite material was increased by 69.9%, and the tensile strength and thermal decomposition temperature of the fiber were maintained substantially unchanged.

Examples 5,

(1) Silane coupling agent modified SiO₂

Drying SiO with particle diameter of 150nm₂Mixing the nanoparticles with N, N-dimethylformamide at a mass ratio of 1:30, stirring at 120 deg.C for 1 hr to obtain a dispersion, and adding 3-aminopropyltrimethoxysilane (SiO 2)₂The mass ratio of the nano particles to the 3-aminopropyl trimethoxy silane is 1:2, and the mixed solution is continuously stirred for 18 hours at the temperature of 115 ℃ to complete the grafting reaction. Centrifuging the product, washing with ethanol for three times, and vacuum drying at 80 deg.C for 24 hr to obtain modified SiO₂Nanoparticles.

(2) Synthesis of benzoxazole diamine compatibilizers

Adding 4, 6-diaminoresorcinol dihydrochloride, 4-aminosalicylic acid and stannous chloride into polyphosphoric acid, wherein the molar ratio of the 4, 6-diaminoresorcinol dihydrochloride to the 4-aminosalicylic acid to the stannous chloride is 1:2.3:0.3, and the phosphorus pentoxide content in the polyphosphoric acid is 83 wt%; n is a radical of₂Slowly heating to 130 ℃ under protection, stirring for 0.5h, then heating to 170 ℃, and continuously stirring for reaction for 9h to obtain a wine red transparent solution; pouring the solution into water for precipitation, performing suction filtration, repeatedly washing a filter cake with water until the pH value of the filtrate is close to 6-8, and drying to obtain a crude product; and recrystallizing the crude product by using N, N-dimethylacetamide/water as a solvent to obtain the benzoxazole diamine.

(3) Modified SiO₂Preparation of benzoxazole diamine/epoxy sizing agent

Taking 3 percent of modified SiO by mass percentage₂Mixing the nano particles, 0.8% of benzoxazole diamine, 2% of AFG-90 and 94.2% of N, N-dimethylacetamide, and performing ultrasonic dispersion uniformly to obtain the sizing agent.

Carrying out PBO fiber surface modification on the prepared sizing agent:

firstly, removing a PBO fiber surface oiling agent: soaking PBO fiber in acetone, heating and refluxing for 24h at 75 ℃, and then drying in vacuum for 18h at 40 ℃ to obtain the PBO fiber with the oil removed; and then soaking the PBO fiber after the oil agent is removed into a slurry tank filled with a sizing agent for 90s, and then carrying out vacuum drying at 130 ℃ for 6h to obtain the sizing modified PBO fiber.

As shown in fig. 3 and 4, IFSS of the sized and modified PBO fiber/epoxy resin composite material was improved by 83.8%, and tensile strength and thermal decomposition temperature of the fiber were substantially maintained.

Comparative examples 1,

Unmodified SiO₂Preparation of epoxy sizing agent:

2% by mass of unmodified SiO from example 1₂Mixing the nano particles, 0.5 percent of E51 and 97.5 percent of acetone, and performing ultrasonic dispersion uniformly to obtain the sizing agent.

The prepared sizing agent was subjected to surface modification of PBO fiber in the same manner as in example 1.

As shown in fig. 3 and 4, the tensile strength and thermal decomposition temperature of the sized and modified PBO fiber remained substantially unchanged, but the IFSS of the composite material was improved by only 18.1%.

Comparative examples 2,

Modified SiO₂Preparation of epoxy sizing agent:

2% by mass of the modified SiO of example 1₂Mixing the nano particles, 0.5 percent of E51 and 97.5 percent of acetone, and performing ultrasonic dispersion uniformly to obtain the sizing agent.

The prepared sizing agent was subjected to surface modification of PBO fiber in the same manner as in example 1.

As shown in fig. 3 and 4, the tensile strength and thermal decomposition temperature of the sized and modified PBO fiber remained substantially unchanged, but the IFSS of the composite material was increased by only 35.5%.

Comparing the effect of examples 1-5 and comparative examples 1-2 on the modification of PBO fibers, it can be seen that the IFSS of PBO fibers modified with different sizing agents are significantly different: the modification effect of the sizing agent in comparative examples 1-2 was significantly lower than that of the sizing agent in examples 1-5, while the modification of SiO in comparative example 2 was performed₂Epoxy sizing higher than unmodified SiO in comparative example 1₂The modification effect of the epoxy sizing agent shows that the epoxy sizing agent has a modification effect on SiO₂The nano particles are subjected to surface silane coupling agent grafting modification, which is favorable for improving SiO₂On-fiberThe dispersibility of the fiber surface is maintained, and the introduction of benzoxazole diamine is beneficial to improving the compatibility of matrix resin and PBO fibers, so that the IFSS of the composite material is improved.