阅读说明：本技术 一种用于改性氰酸酯树脂的功能化中空二氧化硅的合成方法 (Synthetic method of functionalized hollow silica for modified cyanate ester resin ) 是由 焦剑 王瑾 王佳 官梓怡 袁凯 李威霖 于 2019-10-08 设计创作，主要内容包括：本发明涉及一种用于改性氰酸酯树脂的功能化二氧化硅的合成方法,属于雷达防护罩用基体材料技术领域。其包括如下步骤:溶胶-凝胶法、溶剂热法和高温固化制备POSS-HSNs/CE复合材料。本发明采用溶胶-凝胶法并结合有机化改性合成功能化的中空二氧化硅(HSNs)。首先是模板法,模板剂存在时其表面形成二氧化硅壳层后溶解模板剂,得到中空结构完整且封闭中空二氧化硅纳米粒子,模板剂在整个过程中起保护和支撑孔结构的作用。向其表面引入有机官能团以提高与氰酸酯树脂(CE)的键合作用能力,本发明使用硅烷偶联剂和带特殊基团的笼型倍半硅氧烷(POSS)对纳米粒子表面进行修饰。(The invention relates to a synthetic method of functionalized silicon dioxide for modified cyanate ester resin, belonging to the technical field of base materials for radar protective covers. The preparation method comprises the following steps of preparing the POSS-HSNs/CE composite material by a sol-gel method, a solvothermal method and high-temperature curing. The invention adopts a sol-gel method and combines organic modification to synthesize functionalized Hollow Silica (HSNs). Firstly, a template method is adopted, when the template exists, a silicon dioxide shell layer is formed on the surface of the template, then the template is dissolved, the hollow silicon dioxide nano particles with complete hollow structures and closed hollow are obtained, and the template plays a role in protecting and supporting the pore structures in the whole process. Organic functional groups are introduced to the surface of the nano-particle to improve the bonding capability with cyanate ester resin (CE), and the nano-particle surface is modified by using a silane coupling agent and cage type silsesquioxane (POSS) with special groups.)

1. A synthetic method of functionalized hollow silica for modified cyanate ester resin is characterized by comprising the following steps:

step 1, preparing HSNs nano particles by a sol-gel method:

step 1.1: template agents PAA and NH₃·H₂Mixing and standing O for 5-15min, adding ethanol, stirring at room temperature, and sequentially adding TEOS for 5 times at intervals of 20-40 min; after the TEOS is added, continuously stirring for 10-14h to obtain HSNs; the TEOS, template agents PAA and NH₃·H₂Drying and crushing the mixture at the temperature of 60-80 ℃ with the volume ratio of O to ethanol being 0.75-3: 0.1-0.2: 4-7: 80-150;

step 1.2: roasting the obtained HSNs at 500-700 ℃ for 2-4h to obtain roasted HSNs;

step 2: preparing POSS modified HSNs nano particles X-POSS-HSNs by adopting a solvothermal method, wherein the X-POSS-HSNs comprise GI-POSS-HSNs or A-POSS-HSNs or G-POSS-HSNs;

step 2.1, preparing epoxy group modified HSNs nano particles GP-HSNS and amino group modified HSNs nano particles AP-HSNs:

1) mixing the roasted HSNs, KH-560 and toluene according to the molar ratio of 3-5: 0.5-2: 80-150, performing ultrasonic dispersion, performing reflux condensation reaction at 110 ℃ for 3-6h, filtering, washing, and drying at 60-80 ℃ to obtain epoxy group modified HSNs nano particles GP-HSNS;

2) KH-550 is used for replacing KH-560 for the reaction, and the HSNs nano particles AP-HSNs modified by amino groups are obtained;

step 2.2, preparing GI-POSS-HSNs or A-POSS-HSNs or G-POSS-HSNs:

1) uniformly mixing epoxy-modified HSNs nanoparticles GP-HSNS, monoamino cage type silsesquioxane A-POSS and toluene according to the mass ratio of 5-7:3-5:300-400, performing reflux condensation reaction at 100 ℃ for 2-4h after uniform ultrasonic dispersion, cooling, filtering, washing, drying and crushing to obtain A-POSS-HSNs;

2) substituting HSNs nano particles AP-HSNS modified by amino groups for HSNs nano particles GP-HSNS modified by epoxy groups, substituting mono-epoxy group cage type silsesquioxane GI-POSS for mono-amino group cage type silsesquioxane A-POSS, and carrying out the reaction to obtain GI-POSS-HSNs;

3) the HSNs nano particles AP-HSNS modified by amino are unchanged, and the mono-epoxy cage silsesquioxane GI-POSS is replaced by the octa-epoxy cage silsesquioxane G-POSS for the reaction to obtain the G-POSS-HSNs;

step 3, preparing the POSS-HSNs/CE composite material by high-temperature curing: heating 80-120g of bisphenol A type cyanate ester resin CE to a molten state, and then adding X-POSS-HSNs; wherein the X-POSS-HSNs account for 1-7% of the mass of the bisphenol A cyanate ester resin CE; ultrasonic dispersion, adding 4-6 drops of dibutyl lithium dilaurate serving as an accelerator, vacuum drying to remove bubbles, pouring into a mold subjected to heat treatment at 110 ℃ for curing, wherein the curing process is 150 ℃/2h +180 ℃/2h +200 ℃/2h +220 ℃/2h, cooling to room temperature, removing a template material and mechanically cutting a sample to obtain a casting sample, performing post-treatment at 200-250 ℃, and cooling to obtain a POSS-HSNs/CE composite material, namely, functional hollow silica modified cyanate ester resin.

2. The method for synthesizing the functionalized hollow silica for modified cyanate ester resin according to claim 1, wherein: the stirring speed of the step 1 at room temperature is 400-600r/min, and the time is 10-14 h.

3. The method for synthesizing the functionalized hollow silica for modified cyanate ester resin according to claim 1, wherein: the molecular weight of the template agent PAA is 3000-5000.

4. The method for synthesizing functionalized hollow silica for modified cyanate ester resin according to claim 1 or 2, wherein: the room temperature is 25-35 ℃.

5. The method for synthesizing the functionalized hollow silica for modified cyanate ester resin according to claim 1, wherein: the roasting in the step 1.2 adopts a temperature programming process, and the final roasting temperature is 500-700 ℃.

6. The method for synthesizing the functionalized hollow silica for modified cyanate ester resin according to claim 1, wherein: the washing in the step 2 is carried out by washing for 3 times with ethanol and then washing for 3 times with water.

7. The method for synthesizing the functionalized hollow silica for modified cyanate ester resin according to claim 1, wherein: the particle size of the prepared HSNs is 50-150 nm.

8. The method for synthesizing the functionalized hollow silica for modified cyanate ester resin according to claim 1, wherein: the ultrasonic dispersion time in the step 2 and the step 3 is 30-60 min, and the dispersion temperature is 20-40 ℃.

9. The method for synthesizing the functionalized hollow silica for modified cyanate ester resin according to claim 1, wherein: the temperature of vacuum drying and bubble removal in the step 3 is 100-120 ℃, and the bubble removal time is half an hour.

Technical Field

The invention belongs to the technical field of base materials for radar protective covers, and relates to a synthetic method of functionalized hollow silica for modified cyanate ester resin.

Background

The wave-transparent material with excellent performance is mainly applied to the fields of matrixes of aerospace structure composite materials of airplanes, satellites, missiles and the like, protective covers of radars, base materials of high-performance electronic equipment printed circuit boards and the like. The rapid development of the fields of modern aerospace industry and electronic equipment puts higher demands on the wave-transmitting performance of materials at high temperature and wide frequency, and wave-transmitting materials need to have low dielectric constant (epsilon) and smaller dielectric loss (tan delta) in practical application and also have good heat resistance and processability.

The cyanate resin has excellent performance in all aspects, excellent dielectric property and is very suitable to be used as a resin matrix of a wave-transmitting material, so that the cyanate resin has wide application in the fields of aerospace, high-performance circuit boards and the like, but the CE resin has high reaction curing temperature and poor toughness. The cyanate resin can form a triazine ring structure during curing, the triazine ring structure can weaken the interface strength of a material while increasing the mechanical property, so that the brittleness of a polymer is increased, and the application of the polymer is limited.

The cage-type silsesquioxane POSS is used for preparing a composite material with high dielectric property and high mechanical property. POSS can reduce packing density and increase free volume or porosity, which can improve dielectric properties and toughness of the composite. The amino and epoxy groups can react with a cyanate ester bond contained in CE to improve the interface strength of a resin matrix and the nano particles, so POSS with the functional group of the amino or epoxy group can be used for modifying CE, but the introduction of a large amount of POSS is not beneficial to the improvement of the mechanical property and the thermal property of the polymer. Compared with POSS, the mesoporous silica has higher pore volume and more rigid inorganic framework structure, so that the addition of the mesoporous silica can effectively reduce epsilon of the polymer without reducing the mechanical property and the thermal property of the polymer. In the previous work, the CE resin was modified with mesoporous silica, but due to the open pores of the mesoporous silica, the CE resin penetrated into the pores and was filled.

Hollow nano-silica (HSNs) is a nanoparticle with closed gaps, and the porosity of a CE composite material can be improved by introducing the hollow nano-silica (HSNs) into CE, and meanwhile, a large number of hydroxyl groups are contained on the hollow nano-silica, so that conditions are provided for modification of the hollow nano-silica. By introducing an appropriate group thereto, a chemical bond is formed between it and the CE, and the interface strength between the two can be improved. Therefore, based on the advantages of POSS in toughening and HSNs in void content and reinforced rigidity enhancement, the combination of the characteristics of POSS and HSNs in modification of polymers is expected to obtain materials with low dielectric coefficient, high mechanical strength and toughness.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a synthesis method of functionalized hollow silica for modified cyanate ester resin. The hollow silicon dioxide is synthesized by adopting a sol-gel method, and the hollow silicon dioxide nano particles with complete hollow structures and closed hollow silicon dioxide nano particles are obtained by utilizing a method of firstly forming a silicon dioxide shell layer on the surface of a template and then dissolving a template agent, wherein the template agent plays a role in protecting and supporting the pore structures in the whole process. And then organic functional groups are introduced to the surface of the cyanate ester resin (CE) through a solvothermal method so as to improve the bonding effect capacity with the cyanate ester resin (CE).

Technical scheme

A synthetic method of functionalized hollow silica for modified cyanate ester resin is characterized by comprising the following steps:

step 1, preparing HSNs nano particles by a sol-gel method:

step 1.1: template agents PAA and NH₃·H₂Mixing and standing O for 5-15min, adding ethanol, stirring at room temperature, and sequentially adding TEOS for 5 times at intervals of 20-40 min; after the TEOS is added, continuously stirring for 10-14h to obtain HSNs; the TEOS, template agents PAA and NH₃·H₂Drying and crushing the mixture at the temperature of 60-80 ℃ with the volume ratio of O to ethanol being 0.75-3: 0.1-0.2: 4-7: 80-150;

step 1.2: roasting the obtained HSNs at 500-700 ℃ for 2-4h to obtain roasted HSNs;

step 2: preparing POSS modified HSNs nano particles X-POSS-HSNs by adopting a solvothermal method, wherein the X-POSS-HSNs comprise GI-POSS-HSNs or A-POSS-HSNs or G-POSS-HSNs;

step 2.1, preparing epoxy group modified HSNs nano particles GP-HSNS and amino group modified HSNs nano particles AP-HSNs:

1. mixing the roasted HSNs, KH-560 and toluene according to the molar ratio of 3-5: 0.5-2: 80-150, performing ultrasonic dispersion, performing reflux condensation reaction at 110 ℃ for 3-6h, filtering, washing, and drying at 60-80 ℃ to obtain epoxy group modified HSNs nanoparticles GP-HSNS;

2. KH-550 is used for replacing KH-560 for the reaction, and the HSNs nano particles AP-HSNs modified by amino groups are obtained;

step 2.2, preparing GI-POSS-HSNs or A-POSS-HSNs or G-POSS-HSNs:

1. uniformly mixing epoxy-modified HSNs nanoparticles GP-HSNS, monoamino cage type silsesquioxane A-POSS and toluene according to the mass ratio of 5-7:3-5:300-400, performing reflux condensation reaction at 100 ℃ for 2-4h after uniform ultrasonic dispersion, cooling, filtering, washing, drying and crushing to obtain A-POSS-HSNs;

2. substituting the HSNs modified by the amino group by the HSNs nano particle AP-HSNS for the HSNs modified by the epoxy group, and substituting the mono-amino cage silsesquioxane A-POSS by the mono-epoxy cage silsesquioxane GI-POSS to carry out the reaction to obtain GI-POSS-HSNs;

3. the amino modified HSNs nano particles AP-HSNS are unchanged, and the eight-epoxy group cage type silsesquioxane G-POSS is used for replacing mono-epoxy group cage type silsesquioxane GI-POSS to carry out the reaction to obtain G-POSS-HSNs;

step 3, preparing the POSS-HSNs/CE composite material by high-temperature curing: heating 80-120g of bisphenol A type cyanate ester resin CE to a molten state, and then adding X-POSS-HSNs; wherein the X-POSS-HSNs account for 1-7% of the mass of the bisphenol A cyanate ester resin CE; ultrasonic dispersion, adding 4-6 drops of dibutyl lithium dilaurate serving as an accelerator, vacuum drying to remove bubbles, pouring into a mold subjected to heat treatment at 110 ℃ for curing, wherein the curing process is 150 ℃/2h +180 ℃/2h +200 ℃/2h +220 ℃/2h, cooling to room temperature, removing a template material and mechanically cutting a sample to obtain a casting sample, performing post-treatment at 200-250 ℃, and cooling to obtain a POSS-HSNs/CE composite material, namely, functional hollow silica modified cyanate ester resin.

The stirring speed of the step 1 at room temperature is 400-600r/min, and the time is 10-14 h. The beneficial effects are that: the cantilever type constant-speed powerful electric stirrer can control the stirring speed more precisely, increase the dispersion degree, increase the contact of reactants and improve the reaction speed.

The molecular weight of the template agent PAA is 3000-5000.

The room temperature is 25-35 ℃.

The roasting in the step 1.2 adopts a temperature programming process, and the final roasting temperature is 500-700 ℃. The beneficial effects are that: the template agent PAA can be effectively removed under the high-temperature condition.

The washing in the step 2 is carried out by washing for 3 times with ethanol and then washing for 3 times with water.

The particle size of the prepared HSNs is 50-150 nm.

The ultrasonic dispersion time in the step 2 and the step 3 is 30-60 min, and the dispersion temperature is 20-40 ℃.

The temperature of vacuum drying and bubble removal in the step 3 is 100-120 ℃, and the bubble removal time is half an hour.

Advantageous effects

The invention provides a synthesis method of functionalized hollow silica for modified cyanate ester resin, which comprises the following steps of preparing POSS-HSNs/CE composite materials by a sol-gel method, a solvothermal method and high-temperature curing. The invention adopts a sol-gel method and combines organic modification to synthesize functionalized Hollow Silica (HSNs). Firstly, a template method is adopted, when the template exists, a silicon dioxide shell layer is formed on the surface of the template, then the template is dissolved, the hollow silicon dioxide nano particles with complete hollow structures and closed hollow are obtained, and the template plays a role in protecting and supporting the pore structures in the whole process. Organic functional groups are introduced to the surface of the nano-particle to improve the bonding capability with cyanate ester resin (CE), and the nano-particle surface is modified by using a silane coupling agent and cage type silsesquioxane (POSS) with special groups.

The invention utilizes a sol-gel method and a solvothermal method to prepare functionalized hollow silica and applies the functionalized hollow silica to the modification of cyanate ester resin. In the traditional modification of cyanate ester resin by mesoporous material, due to the open pore channel of mesoporous silica, CE resin permeates into the pore channel and is filled. The porosity of the doped nano-particles in the CE is seriously influenced, so that the dielectric property of the composite material is influenced.

The invention adopts a sol-gel method to synthesize the hollow silicon dioxide, and utilizes a method of firstly forming a silicon dioxide shell layer on the surface of the template and then dissolving the template agent to obtain the hollow silicon dioxide nano particles with complete hollow structures and closed cavities. The sealing performance of the internal gaps of the nano particles is fully ensured, and the permeation of the CE resin to the nano material is inhibited.

The invention has the beneficial effects that:

1. compared with the existing template method, the method takes the micelle as the template, and can design the size and the shape of the micelle by adjusting the size and the dispersion condition of the polymer and the solvent so as to obtain the hollow particles with the required specific shape and size.

2. Compared with the existing mesoporous silica modified CE resin, the mesoporous silica modified CE resin fully ensures the closure of the internal voids of the nanoparticles and inhibits the permeation of the CE resin to the nano material. Meanwhile, the pore diameter of the functionalized hollow silica obtained by the sol-gel method and the solvothermal method is averagely kept between 60 and 100nm, and a large space is provided for the dielectric property and the mechanical property of the modified cyanate ester resin.

3. The preparation method disclosed by the invention is simple, easy to operate, low in cost, wide in market prospect and suitable for large-scale popularization and application.

Drawings

FIG. 1 is a flow chart of the sol-gel method for preparing HSNs of the invention.

FIG. 2 is a flow chart of the preparation of functionalized hollow HSNs nanoparticles by solvothermal method of the present invention

FIG. 3 is a transmission electron microscope image of functionalized hollow nanoparticles G-POSS-HSNs obtained by sol-gel method and solvothermal method in Experimental example 5

FIG. 4 is a transmission electron microscope image of GI-POSS-HSNs (functionalized hollow nanoparticles) obtained by sol-gel method and solvothermal method in experimental example 5

FIG. 5 is a transmission electron microscope image of functionalized hollow nanoparticles A-POSS-HSNs obtained by sol-gel method and solvothermal method in Experimental example 5

FIG. 6 is an EDS scan of Si element on a cross section after a bending test is broken in GI-POSS-HSNs/CE material prepared by using functional silica modified cyanate ester resin in Experimental example 6

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

the technical scheme for solving the technical problems is as follows: a method for synthesizing functionalized hollow silica for modified cyanate ester resin. The method comprises the following steps:

the method comprises the following steps: preparation of HSNs nano particles by self-assembly method

Step (1.1): template agent PAA (molecular weight is 5000) and NH₃·H₂Mixing and standing O for 5-15min, adding ethanol, stirring at the speed of 400-600r/min at room temperature for 5-10min, adding TEOS, sequentially adding 5 times at an interval of 20-40min every two times, and continuously stirring for 10-14h after the TEOS is added, wherein TEOS, template agents PAA and NH₃·H₂The volume ratio of O and ethanol is (0.75-3): (0.1-0.2): 47) (80-150), drying and crushing;

step (1.2): roasting the HSNs obtained in the step (1.1) at the temperature of 500-700 ℃ for 2-4h to obtain roasted HSNs;

step two: solvothermal method for preparing HSNs nano-particles (X-POSS-HSNs) with POSS modification

Step (2.1): uniformly mixing the HSNs, KH-560 and toluene obtained in the step (1.2) according to the mol ratio of (3-5) to (0.5-2) to (80-150), performing ultrasonic dispersion, performing reflux condensation reaction at 110 ℃ for 3-6h, filtering, washing and drying at 60-80 ℃ to obtain epoxy group modified HSNs nanoparticles, which are marked as GP-HSNS (epoxy group modification); and (2) uniformly mixing the HSNs, KH-550 and toluene obtained in the step (1.2) according to the mol ratio of (3-5) to (0.5-2) to (80-150), performing ultrasonic dispersion, performing reflux condensation reaction at 110 ℃ for 3-6h, filtering, washing and drying at 60-80 ℃ to obtain amino modified HSNs nano particles, wherein the amino modified HSNs nano particles are marked as AP-HSNs (amino functional group modification).

Step (2.2): uniformly mixing the epoxy group modified HSNs nano particles (GP-HSNS), the monoamino cage type silsesquioxane (A-POSS) and the toluene obtained in the step (2.1) according to the mass ratio of (5-7) to (3-5) to (300-400), uniformly dispersing by ultrasonic waves, carrying out reflux condensation reaction on the solution at 100 ℃ for 2-4h, cooling, filtering, washing, drying and crushing to obtain A-POSS-HSNs; uniformly mixing the HSNs nano particles (AP-HSNS) modified by the amino groups obtained in the step (2.1), the mono-epoxy cage type silsesquioxane (GI-POSS) and the toluene according to the mass ratio of (5-7) to (3-5) to (300-400), uniformly dispersing by ultrasonic, refluxing and condensing the solution at 100 ℃ for 2-4h, cooling, filtering, washing, drying and crushing to obtain GI-POSS-HSNs; uniformly mixing the HSNs nano particles (AP-HSNS) modified by the amino group obtained in the step (2.1), the octa-epoxy cage type silsesquioxane (G-POSS) and the toluene according to the mass ratio of (5-7) to (3-5) to (300-400), uniformly dispersing by ultrasonic, refluxing and condensing the solution at 100 ℃ for 2-4h, cooling, filtering, washing, drying and crushing to obtain the G-POSS-HSNs.

Step three: high-temperature curing preparation of POSS-HSNs/CE composite material

Heating 80-120G of CE to a molten state, and respectively adding the X-POSS-HSNs (GI-POSS-HSNs or A-POSS-HSNs or G-POSS-HSNs) obtained in the step (2.2), wherein the X-POSS-HSNs account for 1-7% of the mass of the CE; ultrasonic dispersion, adding 4-6 drops of dibutyl lithium dilaurate serving as an accelerator, vacuum drying to remove bubbles, pouring into a mold subjected to heat treatment at 110 ℃ for solidification, wherein the solidification process is 150 ℃/2h +180 ℃/2h +200 ℃/2h +220 ℃/2h, cooling to room temperature, removing a template material and mechanically cutting a sample to obtain a casting sample, performing aftertreatment at 200 ℃ and 250 ℃, and cooling to obtain a POSS-HSNs/CE composite material, namely functional hollow silica modified cyanate resin.

In the above technical scheme, in step (1.1), TEOS is an english abbreviation of tetraethoxysilane, which is a silane coupling agent, and it takes ethanol as a catalyst to perform hydrolysis reaction under alkaline condition. The hydrolysis reaction process is divided into the following three stages: (1) ring opening hydrolysis to silanol; (2) the silanol undergoes a glycidyl reaction to generate a linear product which is a main low polymer with silicon-terminated hydroxyl; (3) the silicon hydroxyl groups of the oligomer form hydrogen bonds with the hydroxyl groups of the metal surface oxide or hydrate. In the three stages described above, the sol particles nucleate and the sol particles grow. TEOS has low market price and high hydrolysis yield.

The HSNs are hollow silicon dioxide, which is short for English, and are materials with particle sizes ranging from nanometer to micron and special shapes, and the hollow structure with closed gaps can effectively reduce the dielectric constant of the materials and improve the mechanical property and the thermal property of the materials. By adjusting the addition of TEOS, the addition of ammonia water and the molecular weight of PAA, the hollow nano material with adjustable regular aperture and pore structure, large pore volume and large cavity volume fraction can be obtained.

In the step (1.1), PAA is an English abbreviation of template agent polyacrylic acid, and HSNs prepared by using polyacrylic acid as the template agent have uniform particle size and controllable cavity size.

In the step (2.1), KH-550 is 3 (gamma) -aminopropyltriethoxysilane for short English, KH-560 is gamma-glycidoxypropyltrimethoxysilane, which belong to silane coupling agents, amino groups and epoxy groups are grafted on a target product through reaction, and the problem of an interface between silicon dioxide and a grafted material can be solved.

In step (2.1), GP-HSNS and AP-HSNs refer to materials obtained by grafting KH-560 and KH-550 to HSNs, wherein GP-refers to epoxy modification and AP-refers to amino modification.

In the step (2.2), A-POSS and GP-HSNS are subjected to chemical reaction to obtain A-POSS-HSNs, namely HSNS nano particles modified by monoamino POSS; GI-POSS and AP-HSNS are subjected to chemical reaction to obtain GI-POSS-HSNs, namely HSNS nano particles modified by mono-epoxy POSS; G-POSS and AP-HSNS are subjected to chemical reaction to obtain G-POSS-HSNs, namely HSNS nano particles modified by octa-epoxy group POSS.

In the step (2.2), G-POSS is an octa-epoxy group cage type silsesquioxane for short in English, and the inorganic cage type (core) of the molecule and the organic group R (shell) structure surrounded by the periphery of the G-POSS not only can effectively improve the thermal property and the dielectric property of the material, but also can improve the interface action with other resin matrixes, enhance the compatibility among the materials and show unique advantages in the aspect of polymer modification.

In the step (2.2), X-POSS-HSNs refer to materials obtained by adding X-POSS into GP-HSNs or AP-HSNs according to a certain mass fraction of the total body and carrying out reaction.