1. A high-performance fluorine-containing cyanate ester resin system is characterized in that the components comprise 1-20 parts of fluorine-containing hyperbranched polysiloxane and 80-100 parts of cyanate ester resin by mass; wherein the structural formula of the fluorine-containing hyperbranched polysiloxane is as follows:

2. the high performance fluorochemical cyanate ester resin system according to claim 1, wherein: the cyanate ester resins include, but are not limited to: bisphenol a type cyanate ester resin, bisphenol M type cyanate ester resin, bisphenol E type cyanate ester resin, dicyclopentadiene type cyanate ester resin or other types of cyanate ester resin.

3. The high performance fluorochemical cyanate ester resin system according to claim 1 or 2, wherein: the cyanate resin is bisphenol A type cyanate resin, and the structural formula is as follows:

4. the high performance fluorochemical cyanate ester resin system according to claim 1, wherein: the fluorine-containing hyperbranched polysiloxane is obtained by performing ester exchange polycondensation on trifunctional alkoxy silicon and hexafluorobisphenol A at a molar ratio of 0.8-5: 1.

5. The high performance fluorochemical cyanate ester resin system according to claim 4, wherein: the trifunctional alkoxysilanes include, but are not limited to: gamma-glycidoxypropyltriethoxysilane, gamma-glycidoxypropyltrimethoxysilane, beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, or other types of epoxysilanes.

6. A method for preparing the high-performance fluorine-containing cyanate ester resin system according to any one of claims 1 to 5, which comprises the following steps:

step 1: melting cyanate ester resin at 80-120 ℃, adding fluorine-containing hyperbranched polysiloxane, and mechanically stirring for 30-60 min to prepare a resin prepolymer;

step 2: pouring the resin prepolymer into a preheated mold at the temperature of 80-120 ℃, vacuumizing for 0.5-2 h in a vacuum oven at the temperature of 120-140 ℃, then putting the mold into a forced air drying oven for staged heating and curing, wherein the curing process is 150-190 ℃/2-4 h + 190-210 ℃/2-4 h + 210-240 ℃/1-3 h, cooling, demolding, and post-treating at the temperature of 230-260 ℃ for 3-5 h to obtain the high-performance fluorine-containing cyanate ester resin system.

7. The method of claim 4, wherein: the preparation method of the fluorine-containing hyperbranched polysiloxane comprises the following steps: stirring the three-functionality alkoxy silicon and hexafluorobisphenol A according to a molar ratio of 0.8-5: 1 under the protection of nitrogen, controlling the reaction temperature to be 80-150 ℃, and reacting for 2-12 hours until no distillate is generated, thus obtaining the fluorine-containing hyperbranched polysiloxane.

Background

Cyanate ester resin is used as a high-performance resin matrix, has the advantages of excellent dielectric property, good heat resistance, smaller curing shrinkage, excellent processability and the like, and is widely applied to the fields of electronics and electricians, aerospace and the like. However, the triazine ring structure formed after the cyanate ester resin is cured is highly symmetrical and has high crystallinity, so that the cured product has high brittleness, and the application of the cyanate ester resin is severely limited. Although various methods for modifying cyanate ester have been proposed to improve the toughness to some extent, they have been known to reduce the dielectric properties and heat resistance. Therefore, the toughness, heat resistance and dielectric property of the cyanate ester resin are improved, and the preparation of the high-performance fluorine-containing cyanate ester resin has important practical application value.

Patent CN 106753218A relates to a cyanate ester adhesive with low dielectric constant and high toughness and a preparation method thereof. According to the invention, bisphenol AF type epoxy resin and an organic metal salt catalyst are used for jointly modifying cyanate ester, epoxy group and cyanate ester react to generate oxazololinone, so that on one hand, the regular arrangement of triazine ring in a system is changed, and the cross-linking density of the triazine ring is reduced, thereby reducing the rigidity of the system and improving the toughness of the system; on the other hand, symmetrical-CF in bisphenol AF type epoxy resin₃The polarizability is low, and the dielectric constant and the dielectric loss of the modified cyanate ester adhesive can be effectively reduced. In addition, the addition of an organic metal salt catalyst can effectively promote the curing of cyanate ester, but in practical application, too much residual metal ions in the cured product may reduce the dielectric properties of the product and cause environmental pollution. Patent CN 110028787 a relates to a cyanate ester resin with low dielectric constant and low loss, a wave-transparent composite material and a preparation method thereof. The wave-transmitting composite material consists of reinforced fiber and resin matrix, wherein the resin matrix is prepared by adding fluorinated polyimide into bisphenol M type cyanate resinAnd polyphenylene ether. According to the invention, the rigid monomer containing the fluorine structure is introduced into the main chain of the polyimide molecule, the intermolecular acting force and the close packing degree are reduced by utilizing the bulky side group, the cyanate group with larger polarity is converted into the triazine ring with smaller polarity, the dielectric constant and the dielectric loss of the material are reduced by increasing the bulky side group structure in the molecular structure, and meanwhile, the toughness of the cyanate resin is improved. In addition, the polyphenyl ether has low dielectric constant, in the polymerization process, cyanate ester in a cyanate ester molecular chain reacts with hydroxyl at the chain end of the polyphenyl ether molecular chain to generate imine carbonate, and then further generates triazine ring, the movement of the molecular chain is limited by crosslinking, and the directional polarization is difficult, so that the dielectric constant and the dielectric loss are reduced. However, in the modified resin matrix, polyphenylene ether lacks reactive groups reactive with cyanate ester, and therefore has a problem of poor compatibility with cyanate ester, and the modified resin has an increased viscosity, which affects the molding processability.

The hyperbranched polymer is a polymer with a highly branched structure, the molecular terminal of the hyperbranched polymer contains a large number of active functional groups, the functionalization is easy, a large number of nano-scale cavities exist in the molecule, the viscosity is low, the synthesis of the molecular structure is controllable, and the hyperbranched polymer is widely applied to the modification of resin matrix composite materials. However, the hyperbranched polysiloxane modifiers which are researched and adopted at present can obviously improve the toughness of a resin matrix, but the hyperbranched polysiloxane modifiers still generally have the problem of causing the heat resistance of a resin system to be reduced. Therefore, the invention skillfully designs the molecular structure, utilizes the rigid monomer bisphenol AF with the fluorine-containing structure and the micromolecular silane coupling agent to synthesize the fluorine-containing hyperbranched polysiloxane in one step through condensation polymerization, modifies the cyanate ester resin, has a large number of active functional groups at the end position of the fluorine-containing hyperbranched polysiloxane, can generate copolymerization reaction with the bisphenol A type cyanate ester resin, introduces the flexible Si-O chain segment and the rigid benzene ring structure into the cyanate ester resin, and improves the toughness and the heat resistance of the resin system through the 'rigid-flexible-economic' effect. In addition, a large amount of C-F bonds with low polarizability are introduced, so that the dielectric constant and the dielectric loss of the cyanate ester resin can be effectively reduced.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a high-performance fluorine-containing cyanate resin system and a preparation method thereof, which can improve the dielectric property and the heat resistance of cyanate resin while obviously improving the toughness of cyanate resin.

Technical scheme

A high-performance fluorine-containing cyanate ester resin system is characterized in that the components comprise 1-20 parts of fluorine-containing hyperbranched polysiloxane and 80-100 parts of cyanate ester resin by mass; wherein the structural formula of the fluorine-containing hyperbranched polysiloxane is as follows:

the cyanate ester resins include, but are not limited to: bisphenol a type cyanate ester resin, bisphenol M type cyanate ester resin, bisphenol E type cyanate ester resin, dicyclopentadiene type cyanate ester resin or other types of cyanate ester resin.

The cyanate resin is bisphenol A type cyanate resin, and the structural formula is as follows:

the fluorine-containing hyperbranched polysiloxane has a large number of active functional groups at the end positions, can generate copolymerization reaction with bisphenol A type cyanate ester resin, introduces a flexible Si-O chain segment and a rigid benzene ring structure into the cyanate ester resin, and improves the toughness and heat resistance of a resin system by the 'hardness and softness combined' effect. In addition, a large amount of C-F bonds with low polarizability are introduced, so that the dielectric constant and the dielectric loss of the cyanate ester resin can be effectively reduced.

The fluorine-containing hyperbranched polysiloxane is obtained by performing ester exchange polycondensation on trifunctional alkoxy silicon and hexafluorobisphenol A at a molar ratio of 0.8-5: 1.

The trifunctional alkoxysilanes include, but are not limited to: gamma-glycidoxypropyltriethoxysilane, gamma-glycidoxypropyltrimethoxysilane, beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, or other types of epoxysilanes.

The method for preparing the high-performance fluorine-containing cyanate resin system is characterized by comprising the following steps:

step 1: melting cyanate ester resin at 80-120 ℃, adding fluorine-containing hyperbranched polysiloxane, and mechanically stirring for 30-60 min to prepare a resin prepolymer;

step 2: pouring the resin prepolymer into a preheated mold at the temperature of 80-120 ℃, vacuumizing for 0.5-2 h in a vacuum oven at the temperature of 120-140 ℃, then putting the mold into a forced air drying oven for staged heating and curing, wherein the curing process is 150-190 ℃/2-4 h + 190-210 ℃/2-4 h + 210-240 ℃/1-3 h, cooling, demolding, and post-treating at the temperature of 230-260 ℃ for 3-5 h to obtain the high-performance fluorine-containing cyanate ester resin system.

The preparation method of the fluorine-containing hyperbranched polysiloxane comprises the following steps: stirring the three-functionality alkoxy silicon and hexafluorobisphenol A according to a molar ratio of 0.8-5: 1 under the protection of nitrogen, controlling the reaction temperature to be 80-150 ℃, and reacting for 2-12 hours until no distillate is generated, thus obtaining the fluorine-containing hyperbranched polysiloxane.

Advantageous effects

Aiming at the problems that cured cyanate ester resin is high in brittleness, the original excellent dielectric property and heat resistance are often damaged by the existing toughening modification method and the like, the invention synthesizes fluorine-containing hyperbranched polysiloxane by ingenious molecular structure design and uses the fluorine-containing hyperbranched polysiloxane to modify bisphenol A cyanate ester resin. The fluorine-containing hyperbranched polysiloxane has a large number of active functional groups at the end positions, can generate copolymerization reaction with bisphenol A type cyanate ester resin, introduces a flexible Si-O chain segment and a rigid benzene ring structure into the cyanate ester resin, and improves the toughness and heat resistance of a resin system by the 'hardness and softness combined effect' in a synergistic manner. In addition, the low-polarizability C-F bonds contained in the cyanate ester resin can effectively improve the dielectric properties of the cyanate ester resin. The high-performance fluorine-containing cyanate ester resin system has wide application prospect in the fields of high-performance wave-transmitting materials, 5G communication and the like.

With particular reference to the accompanying drawings:

the IR spectra of bisphenol AF (BPAF), gamma-glycidoxypropyltriethoxysilane (A-187) and fluorine-containing hyperbranched polysiloxane (FHBep) are shown in FIG. 1. In the infrared spectrum of BPAF, 3300cm^-1The nearby absorption peak is the stretching vibration peak of the phenolic hydroxyl group, 1609cm^-1And 1515cm^-1Is the stretching vibration peak of benzene ring skeleton, 1175cm^-1is-CF₃Symmetrical telescopic vibration peaks; in the infrared spectrum of A-187, 1253cm^-1Is a characteristic absorption peak of an epoxy group, 1105cm^-1、1078cm^-1And 849cm^-1Is the stretching vibration peak of C-O-C, Si-O and Si-C; the comparison shows that the absorption peaks all appear in the infrared spectrum of FHBep, and are 3340cm^-1Shows an absorption peak of-OH at 1609cm^-1And 1515cm^-1The stretching vibration peak of the benzene ring skeleton appears, and the absorption peak strength is obviously enhanced. 1253cm^-1、1105 cm^-1、1078cm^-1And 835cm^-1Characteristic absorption peaks of epoxy groups, C-O-C, Si-O and Si-C respectively appear. From this, it can be preliminarily judged that FHBep was successfully synthesized.

As shown in FIG. 2, the designed fluorine-containing hyperbranched polysiloxane has a regular three-dimensional spherical structure under a transmission electron microscope, and in addition, a strong fluorine element absorption peak can be seen from an energy spectrum diagram, which indicates that hyperbranched polysiloxane containing a large number of C-F bonds is successfully synthesized, and elements such as C, O, F, Si and the like are alternately arranged on the surface of the spherical fluorine-containing hyperbranched polysiloxane from an element distribution diagram.

As shown in fig. 3, the flexural strength and the impact strength of the modified cyanate ester resin both increased and then decreased with the increase of the content of the modifier. When the addition amount of the fluorine-containing hyperbranched polysiloxane is 9 wt%, the bending strength and the impact strength of the modified cyanate ester resin are highest, and are respectively improved by 36.4% and 100% compared with pure cyanate ester resin. The main reason is that the molecular structure of the fluorine-containing hyperbranched polysiloxane not only contains a large number of flexible siloxane bonds, but also contains a large number of rigid benzene ring structures. And the fluorine-containing hyperbranched polysiloxane molecule is in a three-dimensional spherical shape (as shown in figure 2) due to the highly branched topological structure, and is similar to a rigid-flexible microsphere, in addition, the fluorine-containing hyperbranched polysiloxane molecule modified cyanate ester resin is not only simply blended, and the fluorine-containing hyperbranched polysiloxane end contains a large amount of active functional groups, can generate copolymerization reaction with the cyanate ester resin, and has good interface bonding effect with a resin matrix so as to meet the stress transfer. Therefore, the cyanate ester modified by the cyanate ester resin has a good toughening effect and can also play a role in strengthening. However, when the addition amount of the particles is increased to a certain degree, the flexural strength and the impact strength of the resin system are reduced, mainly because excessive fluorine-containing hyperbranched polysiloxane molecules react with the resin system, so that the crosslinking density of the cured resin system is too high, the molecular motion is limited, stress is concentrated on local network chains, and the flexural strength and the impact strength of the material are reduced.

Fig. 4 shows TGA and DMA curves of modified cyanate ester resin systems with different amounts of added fluorine-containing hyperbranched polysiloxane, wherein when the amount of added fluorine-containing hyperbranched polysiloxane is 9 wt%, the initial decomposition temperature and the glass transition temperature of the modified cyanate ester resin are both the highest, and are respectively increased by 23 ℃ and 50 ℃ compared with pure cyanate ester resin, on the one hand, the fluorine-containing hyperbranched polysiloxane can be copolymerized with cyanate ester resin to effectively increase the crosslinking density and improve the decomposition resistance thereof; on the other hand, the fluorine-containing hyperbranched polysiloxane contains a large amount of rigid benzene ring structures, and the glass transition temperature of the fluorine-containing hyperbranched polysiloxane can be remarkably improved when the fluorine-containing hyperbranched polysiloxane is introduced into a resin system.

FIG. 5 shows the dielectric constant and dielectric loss of modified cyanate ester resin system with different added amounts of fluorine-containing hyperbranched polysiloxane at high frequency of 8.2-12.4 GHz. As shown in fig. 5, the dielectric constant of all resin systems decreases with increasing frequency, and the dielectric loss increases with increasing frequency, which is mainly attributed to that as the test frequency increases, the atomic polarization and the oriented polarization cannot catch up with the change of the electric field, the polarization degree of the polymer decreases, and the dielectric constant decreases; in addition, the polymer can generate relaxation phenomenon of stimulus response lag in the alternating electric field, the turning of the dipole can not completely follow the change of the electric field due to the viscous force action of the polymer medium, and a part of electric energy is converted into heat energy to be consumed in order to overcome the viscous resistance of the medium. The dielectric constant and the dielectric loss of the cyanate resin system modified by the fluorine-containing hyperbranched polysiloxane are both obviously reduced, which is mainly attributed to that the fluorine-containing hyperbranched polysiloxane contains a large amount of fluorine elements with strong electronegativity, and a large amount of C-F bonds with low polarizability are introduced into the cyanate resin system through copolymerization reaction, so that the polarity of the whole resin system can be reduced, and the dielectric property of the resin system is obviously improved.

Drawings

FIG. 1: example 3 infrared spectrum of fluorine-containing hyperbranched polysiloxane.

FIG. 2: example 3 transmission electron micrograph and energy spectrum of fluorine-containing hyperbranched polysiloxane.

FIG. 3: the bending strength and the impact strength of the fluorine-containing hyperbranched polysiloxane modified cyanate ester resin system with different addition amounts.

FIG. 4: TGA and DMA curves of fluorine-containing hyperbranched polysiloxane modified cyanate ester resin systems with different addition amounts.

FIG. 5: the fluorine-containing hyperbranched polysiloxane modified cyanate ester resin system with different addition amounts has dielectric constant and dielectric loss.

Detailed Description

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

the first step is as follows: adding gamma-glycidyl ether oxypropyl triethoxysilane and hexafluorobisphenol A into a three-neck flask according to a molar ratio of 0.8-5: 1, stirring under the protection of nitrogen, controlling the reaction temperature to be 80-150 ℃, and reacting for 2-12 hours until no distillate is produced, so as to obtain fluorine-containing hyperbranched polysiloxane;

the second step is that: melting bisphenol A type cyanate ester resin at 80-120 ℃, adding 1-20 parts of fluorine-containing hyperbranched polysiloxane, and mechanically stirring for 30-60 min to prepare a resin prepolymer; pouring the resin prepolymer into a preheated mold, vacuumizing for 0.5-2 h in a vacuum oven at 120-140 ℃, then putting into a forced air drying oven for staged heating and curing, wherein the curing process is 150-190 ℃/2-4 h + 190-210 ℃/2-4 h + 210-240 ℃/1-3 h, cooling, demolding, and post-treating for 3-5 h at 230-260 ℃ to obtain the high-performance fluorine-containing cyanate ester resin system.

Example 1 was carried out:

(1) preparation of fluorine-containing hyperbranched polysiloxane

Adding gamma-glycidyl ether oxypropyl triethoxysilane and hexafluorobisphenol A into a three-neck flask according to a molar ratio of 3:1, stirring under the protection of nitrogen, controlling the reaction temperature to be 80-150 ℃, and reacting for 2-12 hours until no distillate is produced, so as to obtain fluorine-containing hyperbranched polysiloxane;

(2) preparation of high-performance fluorine-containing cyanate resin system

Melting 100 parts of bisphenol A type cyanate ester resin at 80 ℃, adding 6 parts of fluorine-containing hyperbranched polysiloxane, mechanically stirring for 30min, pouring into a preheated mold, vacuumizing for 30min in a vacuum oven at 120 ℃, putting into an air-blast drying oven for staged heating and curing, wherein the curing process is 160 ℃/2h +190 ℃/3h +220 ℃/2h, cooling, demolding, and post-treating for 4h at 240 ℃ to obtain the high-performance fluorine-containing cyanate ester resin system.

Example 2 was carried out:

(1) preparation of fluorine-containing hyperbranched polysiloxane

Adding gamma-glycidyl ether oxypropyl triethoxysilane and hexafluorobisphenol A into a three-neck flask according to the molar ratio of 2:1, stirring under the protection of nitrogen, controlling the reaction temperature to be 80-150 ℃, and reacting for 2-12 hours until no distillate is produced, thus obtaining the fluorine-containing hyperbranched polysiloxane;

(2) preparation of high-performance fluorine-containing cyanate resin system

Melting 100 parts of bisphenol A type cyanate ester resin at 80 ℃, adding 9 parts of fluorine-containing hyperbranched polysiloxane, heating to 120 ℃, mechanically stirring for 1h, pouring into a preheated mold, vacuumizing in a vacuum oven at 120 ℃ for 1h, putting into a forced air drying oven for staged heating and curing, wherein the curing process is 160 ℃/2h +190 ℃/3h +220 ℃/2h, cooling, demolding, and post-treating at 240 ℃ for 4h to obtain the high-performance fluorine-containing cyanate ester resin system.

Example 3 of implementation:

(1) preparation of fluorine-containing hyperbranched polysiloxane

Adding gamma-glycidyl ether oxypropyl triethoxysilane and hexafluorobisphenol A into a three-neck flask according to the molar ratio of 1.8:1, stirring under the protection of nitrogen, controlling the reaction temperature to be 80-150 ℃, and reacting for 2-12 hours until no distillate is produced, thus obtaining the fluorine-containing hyperbranched polysiloxane;

(2) preparation of high-performance fluorine-containing cyanate resin system

Melting 100 parts of bisphenol A type cyanate ester resin at 80 ℃, adding 12 parts of fluorine-containing hyperbranched polysiloxane, heating to 120 ℃, mechanically stirring for 40min, pouring into a preheated mold, vacuumizing for 2h in a vacuum oven at 120 ℃, putting into a forced air drying oven for staged heating and curing, wherein the curing process is 160 ℃/2h +190 ℃/3h +220 ℃/2h, cooling, demolding, and post-treating for 4h at 240 ℃ to obtain the high-performance fluorine-containing cyanate ester resin system.

Example 4 of implementation:

(1) preparation of fluorine-containing hyperbranched polysiloxane in the same manner as in example 3

(2) Preparation of high-performance fluorine-containing cyanate resin system

Melting 100 parts of bisphenol A type cyanate ester resin at 80 ℃, adding 15 parts of fluorine-containing hyperbranched polysiloxane, heating to 120 ℃, mechanically stirring for 40min, pouring into a preheated mold, vacuumizing for 2h in a vacuum oven at 120 ℃, putting into a forced air drying oven for staged heating and curing, wherein the curing process is 160 ℃/2h +190 ℃/3h +220 ℃/2h, cooling, demolding, and post-treating for 4h at 240 ℃ to obtain the high-performance fluorine-containing cyanate ester resin system.

The raw material components of the fluorine-containing hyperbranched polysiloxane and the technological parameter chain participating in the reaction designed by the invention are reasonable and can complete the reaction. On the contrary, the purpose and effect of the invention can not be achieved due to unreasonable selection of component parameters or process parameter chains participating in the reaction. As in the following examples:

example 5 was carried out:

adding gamma-glycidoxypropyltriethoxysilane and hexafluorobisphenol A into a three-neck flask according to the molar ratio of 1:2, stirring under the protection of nitrogen, controlling the reaction temperature below 80 ℃, and reacting for 2-12 hours. This is mainly because the reaction temperature is low enough to satisfy the conditions for the reaction to proceed.

Example 6 of implementation:

adding gamma-glycidoxypropyltriethoxysilane and hexafluorobisphenol A into a three-neck flask according to the molar ratio of 1:3, stirring under the protection of nitrogen, controlling the reaction temperature to be 80-150 ℃, and generating a gel phenomenon in the reaction process. The reason is mainly that the content of the hexafluorobisphenol A is high, two benzene rings exist in the structure of the hexafluorobisphenol A, the hexafluorobisphenol A is different from common aliphatic dihydric alcohol, the steric hindrance inside the generated polymer molecule is continuously increased along with the reaction with the gamma-glycidyl ether oxypropyl triethoxysilane, the molecular crosslinking density is continuously increased, when the molecular internal movement is increased to a certain value, the molecular internal movement is severely limited, and the reaction has a gel phenomenon.

Comparative example 1:

continuously stirring 80 parts of bisphenol A type cyanate ester resin for 30min at 120 ℃, and pouring into a preheated mold; vacuumizing for 2h in a vacuum oven at 120 ℃, putting the material into a forced air drying oven for staged heating and curing, wherein the curing process is 160 ℃/1h +180 ℃/2h +200 ℃/2h +220 ℃/3h, cooling, demolding, and post-treating for 4h at 240 ℃ to obtain the bisphenol A cyanate ester resin matrix.

The performance tests of the fluorine-containing cyanate resin systems prepared in the embodiments 1-4 and the comparative example 1 and the bisphenol A cyanate resin matrix are shown in the attached drawings of the specification.

The resin matrix adopted by the high-performance fluorine-containing cyanate ester resin system provided by the embodiment of the invention is bisphenol A cyanate ester resin, and the performances of pure bisphenol A cyanate ester resin matrixes produced by different merchants or resin matrixes produced by different batches of the same merchant have larger difference, so that the beneficial effects of the invention are mainly derived from the improvement of the performance of the fluorine-containing hyperbranched polysiloxane of the invention for modifying the pure bisphenol A cyanate ester resin matrix of the same specification by comparing the performances of the fluorine-containing hyperbranched polysiloxane of the invention.

The above description is provided for further details of the present invention with reference to specific embodiments, which should not be construed as limiting the present invention, but are foreseen and determined by those skilled in the art without disclosure of the present invention.