Method for preparing luminous toughened cyanate ester resin from europium-copolymer nano aggregate

Abstract

The invention discloses a method for preparing luminous toughened cyanate ester resin from a europium-copolymer nano aggregate. The method comprises the following steps: 1) respectively preparing a PS-PAA diblock copolymer and Eu (TTA) Phen: adding an Eu (TTA) Phen solution into the PS-PAA diblock copolymer; obtaining europium-copolymer nano aggregate EIPAs (Europium-Copolymer Nano Aggregate); (2) adding the EIPAs into a cyanate ester monomer; (3) carrying out prepolymerization on a mixture of the europium-copolymer nano aggregate EIPAs and cyanate ester resin; and (4) after the prepolymerization is finished, carrying out a pouring process, degassing treatment and a gradient curing process on the obtained resin-nano aggregate mixture, and cooling and demolding to obtain the luminous toughened cyanate resin. The mechanical property of the obtained composite material is obviously improved, and the tensile strength and the bending strength are obviously enhanced. Meanwhile, the heat resistance of the composite material is also improved, and the potential application value of the composite material in a high-temperature environment is shown.

Description

Technical Field

[0001] The invention relates to the technical field of composite material modification, and in particular to a method for preparing a high-efficiency toughening and luminescent cyanate resin by using europium-copolymer nanoaggregates. Background Art

[0002] Cyanate ester resins (CERs) play an important role in various high-tech fields due to their excellent thermal stability, mechanical strength, and chemical resistance. These thermosetting polymers not only have important applications in aerospace, electronic packaging, and automotive manufacturing, but their low hygroscopicity also makes them ideal for industrial protective and high-performance coatings. However, the high brittleness of cured cyanate ester resins and the high temperature required for curing limit their widespread application in environments requiring high toughness and flexibility. In recent years, research on the modification of cyanate ester resins has focused primarily on improving their toughness and ductility.

[0003] Therefore, the existing technology has defects and needs to be improved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology and provide a method for preparing luminescent toughened cyanate ester resins using europium-copolymer nanoaggregates. The reinforcing effect of CERs by incorporating europium-copolymer nanoaggregates was studied. These modified composites showed significant improvements in mechanical properties, including tensile strength and flexural strength, with the optimal concentration of 0.8 wt% EIPAs significantly improving tensile strength. The study also explored the effect of nanoparticle dispersibility on mechanical properties, emphasizing the importance of controlling particle concentration to avoid aggregation. In addition, the optical and thermal properties of the composites were evaluated, and the results showed enhanced stability and potential for advanced materials applications. The results highlight the potential of CERs in high-performance composites, especially in industries that require a balance between toughness and thermal stability.

[0005] The technical solutions of the present invention are as follows: A method for preparing a luminescent toughened cyanate ester resin from europium-copolymer nanoaggregates comprises the following steps: 1) Separately preparing PS-PAA diblock copolymer and Eu(TTA)3Phen: Adding Eu(TTA)3Phen solution to the PS-PAA diblock copolymer; heating and stirring the resulting mixture to obtain europium-copolymer nanoaggregates (EIPAs); 2) Add EIPAs to the cyanate ester monomer at a ratio of 0.1 wt% to 0.8 wt%; heat and stir the mixture at 60°C to 100°C for 30-120 minutes to ensure uniform dispersion of the EIPAs in the resin.

[0006] 3) Prepolymerization of the mixture of europium-copolymer nanoaggregates (EIPAs) and cyanate ester resin: The EIPAs-doped cyanate ester resin is heated and stirred in an open environment at a temperature between 60°C and 140°C, maintaining this temperature range for prepolymerization. The prepolymerization time at this stage should be 3 to 5 hours to ensure the proper degree of prepolymerization of the resin, providing a good foundation for subsequent curing. 4) After the prepolymerization is completed, the obtained resin-nanoaggregate mixture is subjected to a casting process, a degassing process, a gradient curing process, and a cooling and demolding process to obtain a luminescent toughened cyanate ester resin.

[0007] In the method, the preparation method of Eu(TTA)3Phen in step 1) is as follows: europium chloride hexahydrate (EuCl3·6H2O), 2-thiophenetrifluoroacetone (TTA) and 1,10-phenanthroline (Phen) are mixed in a molar ratio of 1:3:1, heated and stirred at 60°C for 6 hours to obtain a Eu(TTA)3Phen solution.

[0008] In the method, in step 1), the PS-PAA was dissolved in 10 ml of DMF at a concentration of 2 × 10⁻ 4 mol / L, gradually add 10 mL of Eu(TTA)3Phen DMF solution to the PS–PAA DMF solution; the resulting mixture is then heated and stirred for 4–6 h.

[0009] The method includes preheating a polytetrafluoroethylene (PTFE) mold to a temperature between 80°C and 100°C for a time between 30 minutes and 1 hour during the pouring process. The mixture is evenly poured into the preheated mold to ensure that each mold cavity is fully filled and to avoid the formation of bubbles.

[0010] The method described, the PS-PAA diblock copolymer is PS 55 -PAA 47 、PS 55 -PAA 60 or PS 30 -PAA 47 .

[0011] The method includes the following steps: placing the mold after casting in a vacuum oven for low-temperature degassing; the degassing process should be carried out at a temperature range of 90°C to 117°C; and the degassing time is 1-2 hours.

[0012] The method, the gradient curing process: after the degassing treatment is completed, enter the curing step; using the gradient curing process, the specific curing steps are as follows: curing the mixture at 100℃-130℃ for 1-4 hours, curing at 130℃-150℃ for 1-3 hours, curing at 150℃-170℃ for 1-3 hours, curing at 170℃-190℃ for 1-3 hours, curing at 190℃-230℃ for 1-4 hours, and the final curing stage is carried out at 230℃-270℃ for 1-3 hours.

[0013] The method, the cooling and demoulding: after the curing process is completed, the composite material is taken out of the oven and placed in the air to cool naturally for 1 to 4 hours.

[0014] A europium-copolymer nanoaggregate prepared according to any of the methods is used to prepare a high-efficiency toughening and luminescent cyanate resin.

[0015] The present invention has the following beneficial effects after adopting the above technical solution: (1) By doping europium-induced copolymer nanoaggregates into cyanate resin, the thermal stability and mechanical strength of the resin can be significantly improved. This is because europium-induced copolymer nanoaggregates have high thermal stability and excellent mechanical properties. Their addition helps to improve the heat resistance and mechanical properties of the resin material, making the prepared material suitable for applications in higher temperature environments. (2) Better dispersibility and stability: The good dispersibility of europium-induced copolymer nanoaggregates in the resin helps to improve the stability and uniformity of the composite material, avoiding the problems of particle sedimentation and uneven distribution that may occur in traditional methods. The processing process is relatively environmentally friendly and has low volatility and toxicity. Compared with the more harmful solvents that may be used in traditional methods, it is more conducive to operational safety. (3) Gradient curing process: The new method adopts a staged temperature-controlled curing method (gradient curing), first gradually heating at a lower curing temperature and finally curing at a higher temperature. Compared with the traditional method of direct high-temperature curing, this method can effectively reduce internal stress, bubbles and deformation, ensuring that the morphology and structure of the final product are more uniform and stable. (4) Simplifying the process and improving preparation efficiency: This method can achieve the preparation of high-performance composite materials at a low cost by rationally selecting raw materials and process parameters. Most of the raw materials used are common chemicals, and the reaction conditions are relatively mild, which does not require expensive equipment or special environments, thereby reducing production costs. The entire preparation process is simple and efficient. It can ensure the uniform dispersion of europium-induced copolymer nanoaggregates in the resin, and the curing process adopts a gradient temperature curing process, which can effectively avoid bubbles and uneven curing, ensuring the quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Eu 3+(TTA)3phen, three different degrees of polymerization Eu 3+ Induced fluorescence of block polymer aggregates.

[0017] Figure 2 DSC curves of copolymer nanoaggregates co-doped with cyanate ester induced by different concentrations of europium.

[0018] Figure 3 This is the TG curve of pure cyanate ester resin and europium-induced copolymer nanoaggregates co-doped with cyanate ester.

[0019] Figure 4 Tensile (a) and flexural (b) properties of injection molded parts prepared by europium-induced copolymer nanoaggregates co-doped with cyanate.

[0020] Figure 5 TEM images of pure cyanate resin (a), (b) and europium-induced copolymer nanoaggregates co-doped cyanate resin (c), (d). DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to specific embodiments. Example 1: Preparation of Europium Complex Pellets with Different Degrees of Polymerization

[0022] PS 55 -PAA 47 For example, styrene (11.440 g), initiator AIBN (0.054 g), and RAFT agent (0.263 g) were dissolved in 14 ml of 1,4-dioxane. The reaction system was anaerobically treated and heated at 80°C for 6-9 hours. The mixture was then washed with methanol and dried under vacuum to obtain PS. 30 . Prepare a 50mL round-bottom flask, add an appropriate amount of dioxane as a solvent, and stir. Then add 0.4g of polystyrene intermediate and 0.03g of azobisisobutyronitrile (AIBN) initiator to dissolve. After complete dissolution, add concentrated acrylic acid solution in a quantitative manner and mix evenly. The flask is quickly sealed with a rubber stopper to prevent oxygen interference. Nitrogen is introduced for 30-60 minutes to replace the atmosphere, eliminate oxygen in the system, and avoid the formation of by-products. Heat the oil bath at 80°C under a nitrogen environment and react for 9-12 hours to ensure complete reaction. After the reaction is completed, slowly add the solution to an excess of petroleum ether to remove unreacted acrylic acid monomer and by-products. The product in the solution will precipitate and settle downward in the shape of a smoke ring. PS is obtained after standing overnight. 55 -b-PAA 47 After the upper petroleum ether solution was poured off, the precipitate was collected. In order to remove the solvent and excess water, the PS 55 -b-PAA 47The precipitate was placed in a vacuum drying oven at 60°C for 8-10 hours and then the product was collected and stored.

[0023] Dissolve europium chloride (EuCl₃·6H₂O), 2-thiotrifluoroacetone (TTA), and 1,10-phenanthroline (Phen) in 10 mL of N,N-dimethylformamide (DMF) to prepare a solution with a concentration of 4 × 10⁻³ mol / L. These solutions are then mixed in a molar ratio of 1:3:1 to a total volume of 30 mL. The mixture is then heated and stirred at 60°C for 6 hours to prepare the Eu(TTA)₃Phen solution.

[0024] Then PS 30 -b-PAA 47 Dissolved in 10 ml DMF at a concentration of 2 × 10⁻ 4 mol / L. Subsequently, 10 ml of Eu(TTA)3Phen solution was gradually added. The resulting mixture was heated and stirred for another 4 hours to obtain EIPAs 55-47. The same method was then used to obtain EIPAs 55-60 and EIPAs 30-47. Figure 1 Among them, EIPAs55-47 was selected as the fluorescent component for preparing EIPAs / CER because it showed the highest fluorescence intensity.

[0025] Example 2: Preparation of Europium Complex Beads Doped with Cyanate at Different Concentrations: At room temperature, different mass fractions of EIPAs 55-47 (0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, and 1 wt%) were added to five 10-gram portions of cyanate ester monomer. The mixture was heated and stirred at 60°C to 100°C for 30 to 120 minutes to ensure uniform dispersion of the EIPAs in the cyanate ester resin. The EIPAs-doped cyanate ester resin was then heated and stirred in an open environment. The prepolymerization temperature was controlled between 60°C and 140°C and maintained within this temperature range for 3 to 5 hours to achieve the desired degree of prepolymerization.

[0026] Using a polytetrafluoroethylene (PTFE) mold, preheat the mold to 80°C–100°C for 30 minutes–1 hour. Pour the prepolymerized EIPAs / CER evenly into the mold, ensuring that there are no bubbles and that the material is fully filled. The mold is then placed in a vacuum oven for low-temperature degassing at 90°C–117°C for 1–2 hours to remove air bubbles and improve the material's density and performance. After degassing, the mold enters a ramped curing stage within a temperature range of 100°C–270°C. Specifically, the temperature is gradually increased, with the mixture cured at 100°C-130°C for 1-4 hours, 130°C-150°C for 1-3 hours, 150°C-170°C for 1-3 hours, 170°C-190°C for 1-3 hours, 190°C-230°C for 1-4 hours, and a final curing stage at 230°C-270°C for 1-3 hours. The temperature and time of each step are carefully controlled. After curing, the composite is allowed to cool naturally in air for 1-4 hours. Cooling should be slow to avoid thermal stress and cracking. After cooling, the composite is demolded to obtain a solid EIPAs / CER material.

[0027] Figure 2 As shown in the DSC curves, a melting peak is observed at approximately 118°C, while CER and EIPAs / CER exhibit distinct exothermic peaks, also known as curing peaks, in the 200-350°C range. With the introduction of EIPAs, the maximum exothermic peak of CER shifts to lower temperatures. Specifically, the curing temperature gradually decreases after adding 0.2%, 0.4%, 0.6%, 0.8%, and 1% EIPAs to CER, reaching a minimum of 220.38°C at 0.8% EIPAs. This phenomenon highlights the significant catalytic effect of EIPAs in the CE curing process, primarily due to their large surface area and surface-active groups, which affect the energy absorption or release during the resin's transition from an ordered to a disordered state. Furthermore, the introduction of EIPAs may reduce the crosslink density of the resin monomers, which requires higher temperatures and longer times for complete polymerization during the curing process.

[0028] Thermogravimetric analysis (TGA) provides a detailed evaluation of the thermal degradation behavior of cured CER and EIPAs / CER composites to confirm the thermal stability of the materials. Figure 3The thermal degradation curves shown here demonstrate that the addition of nanoaggregates enhances the thermal stability of the composite. Although the addition of nanoaggregates does not alter the fundamental thermal degradation mechanism of the curing system, the initial decomposition temperature of the EIPAs / CER nanocomposite is 447.67°C, 21°C higher than the 426.89°C of pure CER. This indicates that the composite maintains good thermal stability. Therefore, it can be concluded that the addition of different types of carbon nanofillers significantly enhances the thermal resistance of cyanate ester resins.

[0029] Figure 4 (a) Shows the changes in the tensile stress-strain curves of bisphenol F cyanate ester resin (CER) with the incorporation of different concentrations of EIPAs. The tensile strength of pure CER is approximately 18.89 MPa, the lowest among all control experiments, and the area under the curve shows typical brittle fracture behavior. With the addition of nanoaggregates, the tensile strength of the composite system is improved, among which the tensile strength of EIPAs / CER reaches 38.44 MPa, which is 103.49% higher than that of pure CER. The trend in the figure shows that at lower concentrations (0.2%-0.6%), the performance gradually improves, reaching the highest mechanical strength at an addition amount of 0.8 wt%. However, when the concentration is further increased to 1.0 wt%, the strength decreases. This phenomenon can be attributed to the tendency of nanoparticles to aggregate with increasing concentration, resulting in a decrease in their dispersion in the CER composite. This aggregation introduces defects in the material, which in turn affects the overall performance of the composite. Therefore, it is very important to control the concentration of the incorporated particles during the preparation process to avoid excessive nanoparticle aggregation and agglomeration. Similarly, Figure 4 (b) shows that the flexural strength (FS) of pure CER increases from approximately 65.34 MPa to 124.64 MPa for EIPAs / CER, representing an improvement of approximately 90.76%. The addition of nanoparticles increases the interfacial area between the matrix and filler, strengthening interfacial interactions. When EIPAs are uniformly dispersed in CER, they form strong interfacial bonds, facilitating the transfer of external loads across the interface. Nanoparticles act as stress concentrators, effectively transferring stress from the matrix to the nanoparticles under external loads. This effect optimizes the internal stress distribution of the material, reducing the risk of crack initiation and propagation, thereby enhancing the tensile and flexural strength of the composite. At low EIPAs concentrations, the nanoparticles are uniformly distributed in the matrix, maximizing their reinforcing effect. However, at higher concentrations, the nanoparticles tend to aggregate, forming large agglomerates. This aggregation leads to uneven distribution within the material, creating stress concentration points, and ultimately degrading the mechanical properties of the composite.

[0030] Figure 5The micromorphology of the fracture surface of the composite material is shown, observed by scanning electron microscopy (SEM). Figure 5 (a)-(b) show the fracture surface of pure CER (cyanate ester resin), which is smooth and flat, a typical fracture feature of brittle materials. Figure 5 (c)-(d) show the fracture surfaces of EIPAs / CER composites, where the resin surface shows signs of macroscopic plastic deformation, indicating ductile fracture behavior. It can be clearly seen that the cracks propagate in an irregular manner, with obvious deflections and deviations during the propagation process. This is mainly due to the introduction of EIPAs, which increases the resistance to crack propagation and dissipates more fracture energy, thereby enhancing the sample's ability to resist crack extension. In addition, nanoparticles may cause local stress concentration in the matrix, making the fracture surface rougher. The emergence of a layered multi-crack pattern causes the crack surface to deviate from the normal stress axis, thereby improving the bonding ability with the matrix and improving toughness. Therefore, the uniform dispersion of fillers in the resin and their good interaction with the resin are crucial to improving the toughening effect.

[0031] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for preparing a luminescent toughened cyanate ester resin from europium-copolymer nanoaggregates, characterized in that: The following steps are involved: 1) Separately preparing PS-PAA diblock copolymer and Eu(TTA)3Phen: Adding Eu(TTA)3Phen solution to the PS-PAA diblock copolymer; heating and stirring the resulting mixture to obtain europium-copolymer nanoaggregates (EIPAs); 2) Add EIPAs to the cyanate ester monomer at a ratio of 0.1 wt% to 0.8 wt%; heat and stir the mixture at 60°C to 100°C for 30-120 minutes to ensure uniform dispersion of the EIPAs in the resin; 3) Prepolymerization of the mixture of europium-copolymer nanoaggregates (EIPAs) and cyanate ester resin: The EIPAs-doped cyanate ester resin is heated and stirred in an open environment at a temperature between 60°C and 140°C, maintaining this temperature range for prepolymerization. The prepolymerization time at this stage should be 3 to 5 hours to ensure the proper degree of prepolymerization of the resin, providing a good foundation for subsequent curing. 4) After the prepolymerization is completed, the obtained resin-nanoaggregate mixture is subjected to a casting process, a degassing process, a gradient curing process, and a cooling and demolding process to obtain a luminescent toughened cyanate ester resin.

2. The method according to claim 1, characterized in that In step 1), Eu(TTA)3Phen is prepared by mixing europium chloride hexahydrate (EuCl3·6H2O), 2-thiophenetrifluoroacetone (TTA), and 1,10-phenanthroline (Phen) in a molar ratio of 1:3:1, heating and stirring at 60°C for 6 hours to obtain a Eu(TTA)3Phen solution.

3. The method according to claim 1, characterized in that In step 1), the PS-PAA was dissolved in 10 ml of DMF at a concentration of 2 × 10⁻ 4 mol / L, gradually add 10 mL of Eu(TTA)3Phen DMF solution to the PS–PAA DMF solution; the resulting mixture is then heated and stirred for 4–6 h.

4. The method according to claim 1, wherein During the pouring process, a polytetrafluoroethylene (PTFE) mold is preheated to a temperature between 80°C and 100°C for a period of 30 minutes to 1 hour. The mixture is evenly poured into the preheated mold to ensure that each mold cavity is fully filled and to avoid the formation of bubbles.

5. The method according to claim 1, wherein The PS-PAA diblock copolymer is PS 55 -PAA 47 、PS 55 -PAA 60 or PS 30 -PAA 47 .

6. The method according to claim 1, characterized in that The degassing treatment is as follows: the mold after pouring is placed in a vacuum oven for low-temperature degassing; the degassing process should be carried out at a temperature range of 90°C to 117°C; and the degassing time is 1-2 hours.

7. The method according to claim 1, characterized in that The gradient curing process: After the degassing treatment is completed, the curing step is entered; the gradient curing process is adopted, and the specific curing steps are as follows: the mixture is cured at 100°C-130°C for 1-4 hours, 130°C-150°C for 1-3 hours, 150°C-170°C for 1-3 hours, 170°C-190°C for 1-3 hours, 190°C-230°C for 1-4 hours, and the final curing stage is carried out at 230°C-270°C for 1-3 hours.

8. The method according to claim 1, characterized in that The cooling and demoulding: After the curing process is completed, the composite material is taken out of the oven and placed in the air to cool naturally for 1 to 4 hours.

9. A cyanate resin prepared according to any one of claims 1 to 8.

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