Cyanate ester composite resin with low dielectric constant and high thermal conductivity and preparation method thereof
By uniformly loading nano-hexagonal boron nitride onto the surface of hollow polyamic acid microspheres, a three-dimensional thermally conductive network is constructed and the dielectric constant is reduced, thus solving the problems of low thermal conductivity and poor interfacial compatibility of cyanate ester resins. This results in the preparation of a low-dielectric-and-high-thermal-conductivity cyanate ester composite resin suitable for radar radomes and aerospace structural components.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-17
- Publication Date
- 2026-05-05
AI Technical Summary
Pure cyanate resin has low thermal conductivity, making it difficult to meet the heat dissipation requirements of high-power electronic devices and radar systems. Furthermore, hexagonal boron nitride tends to agglomerate in the resin matrix and has poor interfacial compatibility, which makes it difficult to improve the thermal conductivity and dielectric properties of the composite material.
Nanoscale hexagonal boron nitride was uniformly loaded onto the surface of polyamic acid hollow microspheres using electrostatic self-assembly technology. The amide and carboxyl groups of the polyamic acid porous microspheres formed a cross-linked structure during the curing process of cyanate ester, thus constructing a three-dimensional thermally conductive network. Air was also introduced to reduce the dielectric constant.
The high thermal conductivity and low dielectric properties of cyanate ester composite resins have been achieved, making them suitable for radar radomes and aerospace structural components.
Smart Images
Figure CN121975320A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of resin matrices, and more specifically to a low dielectric and high thermal conductivity cyanate ester composite resin and its preparation method. Background Technology
[0002] Cyanate ester resins are widely used in high-frequency circuit boards, aerospace structural components, and radar radomes due to their excellent heat resistance and good dielectric properties. However, the thermal conductivity of pure cyanate ester resin is only about 0.2 W / (m·K), which is insufficient to meet the heat dissipation requirements of high-power electronic devices and radar systems.
[0003] Adding high thermal conductivity fillers to the resin matrix is the most direct and effective way to improve the thermal conductivity of composite materials. Hexagonal boron nitride (h-BN) has a graphite-like layered structure, a theoretical thermal conductivity as high as 400 W / (m·K), and good electrical insulation and low dielectric properties, making it an ideal filler for improving the thermal conductivity of resins.
[0004] However, h-BN has a large specific surface area and high surface energy, making it prone to agglomeration in resin matrices. Furthermore, its poor interfacial compatibility with organic resin matrices leads to defects within the composite material and increased interfacial thermal resistance, hindering the achievement of the desired improvement in thermal conductivity. Directly filling h-BN into the matrix often results in a high percolation threshold, easy agglomeration, and high interfacial thermal resistance due to interfacial phonon scattering, further deteriorating the material's dielectric properties. Summary of the Invention
[0005] To address the aforementioned problems and shortcomings, and to solve the current challenge of simultaneously controlling the dielectric and thermal conductivity properties of cyanate esters, this invention provides a low-dielectric- and high-thermal-conductivity cyanate ester composite resin and its preparation method. Through electrostatic self-assembly technology, nano-hexagonal boron nitride is uniformly loaded onto the surface of hollow polyamic acid microspheres, achieving uniform dispersion of the filler in the cyanate ester resin. The addition of hollow porous microspheres simultaneously introduces a large amount of air, thereby obtaining a composite material with both excellent dielectric and thermal conductivity properties.
[0006] A method for preparing a low-dielectric- and high-thermal-conductivity cyanate ester composite resin includes the following steps:
[0007] Step 1: Disperse polyamic acid hollow microsphere powder in deionized water, add a strong cationic polyelectrolyte (a polyelectrolyte that is completely dissociated in the current solution) under magnetic stirring, stir the reaction at room temperature until complete, centrifuge to separate, remove the supernatant, and collect the positively charged polyamic acid hollow porous microspheres.
[0008] Step 2: Disperse nano-hexagonal boron nitride (h-BN) in a polar organic solvent and sonicate it to ensure uniform dispersion. Then add the positively charged polyamic acid hollow porous microspheres obtained in Step 1. After stirring, centrifuge, wash and dry to obtain polyamic acid@hexagonal boron nitride microspheres (PAA@h-BN-PM).
[0009] Step 3: Weigh out cyanate ester resin and toughening agent in a mass ratio of 10:0.5~10:2, melt and mix them evenly, add the polyamic acid@hexagonal boron nitride microspheres obtained in Step 2, stir and mix evenly to obtain polyamic acid@hexagonal boron nitride microsphere modified cyanate ester resin prepolymer.
[0010] Step 4: Add a catalyst-toughening agent to the polyamic acid@hexagonal boron nitride microsphere modified cyanate resin prepolymer obtained in Step 3, and heat and stir to mix thoroughly. Then pour it into a preheated mold, degas under vacuum, and then cure by step heating at 120~220℃ to obtain polyimide hollow microspheres@hexagonal boron nitride modified cyanate resin.
[0011] Furthermore, the strong cationic polyelectrolyte in step 1 is one of polydiallyldimethylammonium chloride (PDDA) and polyethyleneimine (PEI).
[0012] Furthermore, the polar organic solvent in step 2 is either isopropanol or ethanol.
[0013] Furthermore, the toughening agent in step 3 is one of bisphenol A type epoxy resin (E51), carboxyl-terminated butadiene nitrile rubber (CTBN), and epoxy-terminated butadiene nitrile rubber (ETBN).
[0014] Furthermore, the catalyst-toughening agent in step 4 is two or three of diallyl bisphenol A (DBA), cobalt acetylacetonate, dibutyltin dilaurate (DBTDL), and 4-methylquinoline.
[0015] Furthermore, the polyamic acid hollow porous microsphere powder is prepared using the following steps:
[0016] Step 1: Dissolve the diamine as a reactant monomer in a nonpolar solvent, stir to dissolve, and then add the dianhydride monomer. Perform a polycondensation reaction under a protective atmosphere and at low temperature to obtain polyamic acid (PAA). Then add an organic amine (such as triethylamine) to obtain polyamic acid salt. The molar ratio of the organic amine to the diamine monomer is 2:1, and the molar ratio of the diamine to the dianhydride is 1:1 to 1:1.5.
[0017] The dianhydride monomer is one or a combination of several of the following: pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 4,4'-oxobisphthalic anhydride (ODPA).
[0018] The diamine monomer is one or a combination of several of 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenylmethane (MDA), and p-phenylenediamine (p-PDA).
[0019] The nonpolar solvent is one of N,N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP).
[0020] Step 2: Dissolve the polyamic acid salt obtained in Step 1 in deionized water with a solid content of 1-5 wt% to obtain an aqueous PAA solution.
[0021] Step 3: Add cationic surfactant and liquid paraffin oil phase to the PAA aqueous solution obtained in Step 2 while stirring to form an oil-in-water emulsion and continue stirring. The volume ratio of liquid paraffin to PAA aqueous solution is 1:2 to 1:8, and the volume ratio of cationic surfactant to PAA aqueous solution is 1:50 to 1:150.
[0022] The cationic surfactant is one or two of hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and dimethyl dioctadecylammonium chloride (DODAC).
[0023] Step 4: Add a mixed solution of acetic anhydride and pyridine to the solution obtained in Step 3, then wash, centrifuge, and freeze-dry to obtain polyamic acid hollow porous microsphere powder. The volume ratio of acetic anhydride to pyridine is 1:1 to 1:3.
[0024] In summary, this invention prepares positively charged polyamic acid porous microspheres and uses electrostatic self-assembly technology to uniformly load nano-hexagonal boron nitride onto the surface of the hollow polyamic acid microspheres. This achieves uniform dispersion of the filler in cyanate ester resin, forming a core-shell structure PAA@h-BN-PM, effectively improving the problems of easy agglomeration of h-BN in the resin matrix and poor interfacial compatibility. The surface of the polyamic acid porous microspheres is rich in amide groups (-CO-NH-) and carboxyl groups (-COOH), which can be simultaneously imidized during the cyanate ester curing process, promoting the formation of cross-linked structures between microspheres, thereby effectively reducing interfacial thermal resistance and constructing a highly efficient three-dimensional thermally conductive network. Simultaneously, the addition of hollow polyamic acid porous microspheres introduces a large amount of air into the system, which can significantly reduce the dielectric constant of the composite resin. Therefore, this invention prepares a cyanate ester composite resin with both low dielectric constant and high thermal conductivity, suitable for applications such as radar radomes and aerospace structural components. Attached Figure Description
[0025] Figure 1 FTIR of polyamic acid@hexagonal boron nitride hollow porous microspheres prepared in Example 1.
[0026] Figure 2 SEM and EDS images of the polyamic acid@hexagonal boron nitride hollow porous microspheres prepared in Example 1.
[0027] Figure 3 The thermal conductivity of the polyimide hollow microspheres@hexagonal boron nitride modified cyanate ester composite resin obtained in Examples 1-3 was tested compared with that in Comparative Example 2.
[0028] Figure 4 Dielectric properties of the polyimide hollow microspheres@hexagonal boron nitride modified cyanate ester composite resin obtained in Examples 1-3 and Comparative Example 2 were tested. Detailed Implementation
[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.
[0030] Example 1:
[0031] A method for preparing a low-dielectric- and high-thermal-conductivity cyanate ester composite resin includes the following steps:
[0032] Step 1: Weigh 0.01 mol of 4,4'-diaminodiphenyl ether and dissolve it in 50 mL of N,N-dimethylacetamide (DMAc) under a nitrogen atmosphere. Then add 0.01 mol of pyromellitic anhydride (PMDA) and stir at 0 °C for 6 h to obtain a viscous polyamic acid solution. Add 2.78 mL of triethylamine (TEA) to the reaction system and continue stirring for half an hour to form a salt. In subsequent purification, the reaction product is washed with acetone at least three times and dried to obtain the target product, polyamic acid salt solid.
[0033] Step 2: Weigh 0.0445 g of polyamic acid acid solid and dissolve it in 14 ml of deionized water as the outer aqueous continuous phase. Add 0.1 ml of low-valent cetyltrimethylammonium bromide (CTAB) dropwise to the reaction system, followed by 8 ml of liquid paraffin as the inner oil phase, and stir to emulsify. Then add a mixed solvent consisting of 1 ml acetic anhydride and 1 ml pyridine and stir for 10 minutes. Finally, wash the product at least three times with petroleum ether, centrifuge, and freeze-dry to obtain well-dispersed polyamic acid hollow porous microsphere powder.
[0034] Step 3: Take 1.0 g of the polyamic acid hollow microspheres prepared in Step 2 and disperse them in 100 mL of deionized water. Stir magnetically to ensure thorough dispersion. Add 0.2 g of polydiallyldimethylammonium chloride solution (20 wt%) and stir at room temperature for 1 hour. After the reaction is complete, centrifuge to remove the supernatant and collect the positively charged polyamic acid hollow microspheres.
[0035] Step 4: Disperse 0.15 g of nano-hexagonal boron nitride in 200 mL of isopropanol aqueous solution (isopropanol:water = 1:2, v / v), and sonicate to achieve uniform dispersion, obtaining a negatively charged h-BN dispersion. Weigh 0.5 g of positively charged polyamic acid hollow microspheres obtained in Step 3 and add them to the h-BN dispersion, stirring continuously at room temperature for 2 hours. After the reaction is complete, centrifuge, wash with isopropanol, and dry to obtain polyamic acid@hexagonal boron nitride hollow porous microspheres (h-BN:PAA mass ratio = 0.3:1).
[0036] Step 5: Place 10g of bisphenol A dicyanate (BADCy) and 1g of epoxy resin (E-51) in a 120℃ oil bath and heat with mechanical stirring until the mixture is completely melted and no crystal residue remains to obtain the modified cyanate prepolymer. Weigh 0.25g of polyamic acid@hexagonal boron nitride hollow porous microspheres obtained in Step 4 and ultrasonically disperse them in an appropriate amount of anhydrous ethanol. Slowly add the mixture to the modified cyanate prepolymer under stirring and mix thoroughly. Then, add 0.0025g of tetramethylquinoline (1% of the mass of PAA@h-BN-PM) and stir at 120℃ until the ethanol is completely evaporated. Then, pour the mixture into a preheated mold and degas under vacuum at 120℃ for 2 hours; then, cure by stepwise temperature increases of 140℃ / 2h, 160℃ / 2h, 180℃ / 2h, 200℃ / 2h, and 220℃ / 4h to obtain the polyamic acid hollow microsphere@hexagonal boron nitride modified cyanate composite resin.
[0037] Example 2
[0038] The difference between this embodiment and Example 1 is that in step 5, 0.5g of the polyamic acid@hexagonal boron nitride hollow porous microspheres prepared in step 4 are weighed and 0.005g of tetramethylquinoline (1% of the mass of PAA@h-BN-PM) is added; the remaining steps are the same as in Example 1.
[0039] Example 3
[0040] The difference between this embodiment and Example 1 is that in step 5, 0.75g of the polyamic acid@hexagonal boron nitride hollow porous microspheres prepared in step 4 are weighed and 0.0075g of tetramethylquinoline (1% of the mass of PAA@h-BN-PM) is added; the remaining steps are the same as in Example 1.
[0041] Comparative Example 1
[0042] 0.01 mol of 4,4'-diaminodiphenyl ether was dissolved in 50 mL of N,N-dimethylacetamide (DMAc) under a nitrogen atmosphere. Then, 0.01 mol of pyromellitic anhydride (PMDA) was added, and the mixture was stirred at 0 °C for 6 h to obtain a viscous polyamic acid solution. 2.78 mL of triethylamine (TEA) was added to the reaction system, and stirring was continued for another half hour to form a salt. In subsequent purification, the reaction product was washed with acetone at least three times and dried to obtain the target product, polyamic acid salt solid.
[0043] Step 2: Weigh 0.0445 g of polyamic acid acid solid and dissolve it in 14 ml of deionized water as the outer aqueous continuous phase. Add 0.1 ml of low-valent cetyltrimethylammonium bromide (CTAB) dropwise to the reaction system, followed by 8 ml of liquid paraffin as the inner oil phase, and stir to emulsify. Then add a mixed solvent consisting of 1 ml acetic anhydride and 1 ml pyridine and stir for 10 minutes. Finally, wash the product at least three times with petroleum ether, centrifuge, and freeze-dry to obtain well-dispersed polyamic acid hollow porous microsphere powder (PAA-PM).
[0044] Comparative Example 2
[0045] Bisphenol A dicyanate (BADCy) and 10 wt% epoxy resin (E-51) were heated at 160°C and mechanically stirred until the mixture was completely melted and no crystal residue remained, thus obtaining the modified cyanate resin prepolymer (mCE).
[0046] Figure 1 The figures show a comparison of the FTIR spectra of the two porous microspheres obtained in Example 1 and Comparative Example 1, respectively. As can be seen from the figures, the polyamic acid hollow porous microspheres prepared in Comparative Example 1 have a larger 1664 cm⁻¹ diameter. -1 The peak corresponds to the characteristic peak of the C=O stretching vibration of the carboxyl group (-COOH), while 1605 cm⁻¹ is... -1 and 1548 cm -1 The peaks at these locations correspond to the characteristic peaks of C=O and CN of the amide group (-CONH-) in polyamic acid, respectively. Furthermore, at 1375 cm⁻¹... -1 and 780 cm -1 The characteristic stretching vibration peak of h-BN was clearly observed.
[0047] Figure 2The images show SEM and EDS images of the polyamic acid@hexagonal boron nitride hollow porous composite microspheres obtained in Example 1. As can be seen from the images, the surface of the microspheres is relatively rough and uniformly covered with sheet-like protrusions. Furthermore, according to the EDS, the distribution of boron (B) element shows a highly consistent correlation with the microsphere morphology, and the distribution is uniform. This preliminarily indicates that Example 1 successfully prepared polyamic acid@hexagonal boron nitride hollow porous composite microspheres.
[0048] Figure 3 The figures show the thermal conductivity test results for Examples 1-3 and Comparative Example 2. As shown, the thermal conductivity and thermal diffusivity of Examples 1-3 are significantly higher than those of Comparative Example 2, and both show a continuous upward trend with the increase of polyimide@hexagonal boron nitride composite microsphere content. This indicates that the polyimide@hexagonal boron nitride composite microspheres construct an effective three-dimensional thermally conductive network in the resin system. When the microspheres come into contact with each other, the h-BN shell on the surface forms an effective "thermal bridge" at the contact point, promoting rapid heat transfer along the highly thermally conductive h-BN channels, significantly reducing interfacial thermal resistance, and effectively improving the thermal conductivity of the composite resin.
[0049] Figure 4 The dielectric properties of the polyimide@hexagonal boron nitride microsphere-modified cyanate ester composite resins obtained in Examples 1-3 and the modified cyanate ester resin obtained in Comparative Example 2 are shown in the figure. (a) shows the change in dielectric constant, and (b) shows the change in dielectric loss. As shown, the dielectric constants of Examples 1 and 2 are lower than those of Comparative Example 2. This is because the porous structure of the microspheres introduces air with a dielectric constant of 1, significantly reducing the dielectric constant of the resin.
[0050] As can be seen from the above examples and comparative examples, this invention, by preparing positively charged polyamic acid porous microspheres and utilizing electrostatic self-assembly technology, uniformly loads nano-hexagonal boron nitride onto the surface of the hollow polyamic acid microspheres, achieving uniform dispersion of the filler in the cyanate ester resin. This improves the problems of easy agglomeration of h-BN in the resin matrix and poor interfacial compatibility. The amide groups (-CO-NH-) and carboxyl groups (-COOH) abundant on the surface of the polyamic acid porous microspheres undergo simultaneous imidization during the cyanate curing process, promoting the formation of cross-linked structures between the microspheres, thereby effectively reducing interfacial thermal resistance and constructing a highly efficient three-dimensional thermally conductive network. Simultaneously, the addition of hollow polyamic acid porous microspheres introduces a large amount of air into the system, which can significantly reduce the dielectric constant of the composite resin. The cyanate ester composite resin prepared by this invention possesses both low dielectric constant and high thermal conductivity, making it suitable for applications such as radar radomes and aerospace structural components.
Claims
1. A method for preparing a low-dielectric- and high-thermal-conductivity cyanate ester composite resin, characterized in that, Includes the following steps: Step 1: Disperse polyamic acid hollow porous microsphere powder in deionized water, add strong cationic polyelectrolyte under magnetic stirring, stir and react completely at room temperature, centrifuge to remove the supernatant, and collect the positively charged polyamic acid hollow porous microspheres. Step 2: Disperse nano-hexagonal boron nitride h-BN in a polar organic solvent, sonicate to make it uniformly dispersed, and then add the positively charged polyamic acid hollow porous microspheres obtained in Step 1. After stirring, centrifuge and analyze, wash and dry to obtain polyamic acid@hexagonal boron nitride microspheres PAA@h-BN-PM. Step 3: Weigh out cyanate resin and toughening agent in a mass ratio of 10:0.5~2, melt and mix them evenly, add the polyamic acid@hexagonal boron nitride microspheres obtained in Step 2, stir and mix evenly to obtain polyamic acid@hexagonal boron nitride microsphere modified cyanate resin prepolymer; Step 4: Add a catalyst-toughening agent to the polyamic acid@hexagonal boron nitride microsphere modified cyanate resin prepolymer obtained in step 3, heat and stir to mix thoroughly; then pour into a preheated mold, degas under vacuum, and then cure by step heating at 120~220℃ to obtain polyimide hollow microspheres@hexagonal boron nitride modified cyanate resin.
2. The method for preparing the low-dielectric- and high-thermal-conductivity cyanate ester composite resin as described in claim 1, characterized in that: The strong cationic polyelectrolyte in step 1 is one of polydiallyldimethylammonium chloride (PDDA) and polyethyleneimine (PEI).
3. The method for preparing the low-dielectric- and high-thermal-conductivity cyanate ester composite resin as described in claim 1, characterized in that: The polar organic solvent in step 2 is either isopropanol or ethanol.
4. The method for preparing the low-dielectric- and high-thermal-conductivity cyanate ester composite resin according to claim 1, characterized in that: The toughening agent in step 3 is one of bisphenol A type epoxy resin E51, carboxyl-terminated butadiene nitrile rubber CTBN, and epoxy-terminated butadiene nitrile rubber ETBN.
5. The method for preparing the low-dielectric- and high-thermal-conductivity cyanate ester composite resin according to claim 1, characterized in that: The catalyst-toughening agent in step 4 is two or three of diallyl bisphenol A (DBA), cobalt acetylacetonate, dibutyltin dilaurate (DBTDL), and 4-methylquinoline.
6. The method for preparing the low-dielectric- and high-thermal-conductivity cyanate ester composite resin as described in claim 1, characterized in that, The polyamic acid hollow porous microsphere powder is prepared using the following steps: Step 1: Dissolve the diamine as a reactive monomer in a non-polar solvent, stir to dissolve, and then add the dianhydride monomer. Polycondensation reaction is carried out under a protective atmosphere and at low temperature to obtain polyamic acid PAA. Then, triethylamine is added to obtain polyamic acid salt. The molar ratio of organic amine to diamine monomer is 2:1, and the molar ratio of diamine to dianhydride is 1:1 to 1:1.
5. The dianhydride monomer is one or a combination of several of the following: pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 4,4'-oxobisphthalic anhydride (ODPA). The diamine monomer is one or a combination of several of 4,4'-diaminodiphenyl ether ODA, 4,4'-diaminodiphenylmethane MDA, and p-phenylenediamine p-PDA; The nonpolar solvent is one of N,N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP). Step 2: Dissolve the polyamic acid salt obtained in Step 1 in deionized water with a solid content of 1-5 wt% to obtain an aqueous PAA solution; Step 3: Add cationic surfactant and liquid paraffin oil phase to the PAA aqueous solution obtained in Step 2 under stirring to form an oil-in-water emulsion and continue stirring; wherein, the volume ratio of liquid paraffin to PAA aqueous solution is 1:2 to 1:8, and the volume ratio of cationic surfactant to PAA aqueous solution is 1:50 to 1:
150. The cationic surfactant is one or two of hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and dimethyl dioctadecylammonium chloride (DODAC). Step 4: Add a mixed solution of acetic anhydride and pyridine to the solution obtained in step 3, and then wash, centrifuge and freeze dry to obtain polyamic acid hollow porous microsphere powder; wherein the volume ratio of acetic anhydride to pyridine is 1:1 to 1:
3.
7. A method for preparing a low-dielectric- and high-thermal-conductivity cyanate ester composite resin, characterized in that: Prepared using the method described in any one of claims 1-5.