Preparation method of benzoxazine and bismaleimide transparent resin alloy

Abstract

The invention relates to the technical field of thermosetting materials, and discloses a preparation method of benzoxazine and bismaleimide transparent resin alloy, which comprises the following steps: preparing required materials: mixing bismaleimide and benzoxazine according to a certain proportion, adding a proper amount of solvent, and stirring for a period of time to form a uniform mixture; adding a proper amount of cross-linking agent into the mixture, fully stirring, casting a blend solution on a glass plate pretreated with dimethyldichlorosilane, drying at 50 DEG C for 4-6 hours, and then respectively carrying out heat treatment at different temperatures for 1-3 hours to obtain an alloy membrane; and testing the performance of the alloy film. According to the process, bismaleimide and benzoxazine are used as main raw materials, and the transparent bismaleimide resin alloy material with excellent performance is prepared through a specific formula and process steps. The alloy material not only has high transparency and excellent heat resistance, but also has relatively high mechanical strength and chemical stability.

Description

Technical Field

[0001] This invention relates to the field of thermosetting materials technology, specifically to a method for preparing a transparent resin alloy of benzoxazine and bismaleimide. Background Technology

[0002] Polybenzoxazine has been developed as a novel phenolic resin, which can be provided through ring-opening polymerization of benzoxazine monomers. A typical benzoxazine monomer, 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (Pa), has the following structural formula: Figure 1 As shown. It not only possesses the characteristics of traditional phenolic resins, such as good flame retardancy and chemical resistance, but also unique properties not found in traditional phenolic resins, such as molecular design flexibility, low hygroscopicity, near-zero shrinkage during polymerization, and low dielectric constant. Furthermore, benzoxazine can be polymerized simply by heating without the need for strong acid catalysts and does not produce harmful byproducts during curing. Therefore, polybenzoxazine overcomes the shortcomings of traditional phenolic resins without sacrificing their advantages. However, its glass transition temperature (Tg) is approximately 100℃~150℃, insufficient for use under harsh conditions. Methods to improve the thermal properties of polybenzoxazine can be divided into two types. One is modification of the monomer structure, and the other is alloying or mixing with materials possessing high thermal stability, such as polyimide, multi-walled carbon nanotubes, titanium dioxide, and clay.

[0003] Bismaleimide (BMI) possesses excellent thermomechanical properties and withstands high stress at high temperatures. Therefore, maleimide structures have long been incorporated into many polymer systems because they typically produce thermally stable polymers with high heat deflection temperatures (Tg) and improved heat distortion temperatures due to the rigid imide rings. Incorporating maleimide groups into benzoxazine monomers effectively improves the thermal properties of their thermosetting materials. To broaden the service temperature range of polybenzoxazine, improve thermal stability and flame retardancy, and enable its use under harsh conditions, a method for preparing a transparent benzoxazine-bismaleimide resin alloy is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a transparent resin alloy of benzoxazine and bismaleimide, in order to solve the problem mentioned in the background art of using polybenzoxazine under harsh conditions by broadening its operating temperature range, improving its thermal stability and flame retardancy.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a benzoxazine and bismaleimide transparent resin alloy, comprising the following steps:

[0006] Step 1: Prepare the required materials: bismaleimide, benzoxazine, solvent, and crosslinking agent;

[0007] Step 2: Mix bismaleimide and benzoxazine in a certain proportion, add an appropriate amount of solvent, and stir for a period of time to form a homogeneous mixture;

[0008] Step 3: Add an appropriate amount of crosslinking agent to the mixture and stir thoroughly to disperse it evenly and form a blend solution;

[0009] Step 4: Cast the blend solution onto a glass plate pretreated with dimethyldichlorosilane, dry it at 50°C for 4-6 hours, and then heat treat it at different temperatures for 1-3 hours to obtain the alloy film.

[0010] Step 5: Perform performance tests on the alloy films obtained with different mixing ratios and different heat treatment temperatures.

[0011] Preferably, in step four, the blend solution is cast onto a glass plate pretreated with dimethyldichlorosilane, dried at 50°C for 4 hours, and then heat-treated at 100°C, 120°C, 160°C, 200°C, and 240°C for 1 hour respectively to obtain an alloy film.

[0012] Preferably, the solvent in step one is chloroform.

[0013] Preferably, benzoxazine comprises 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine.

[0014] Preferably, the mass ratio of bismaleimide and benzoxazine is one of 20 / 80, 40 / 60, 50 / 50, 70 / 30 and 80 / 20.

[0015] Preferably, the different heat treatment temperatures in step five are 100℃, 120℃, 160℃, 200℃, and 240℃.

[0016] Preferably, the stirring time in step three is 30-60 minutes.

[0017] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0018] This process uses bismaleimide and benzoxazine as main raw materials, and through specific formulations and process steps, prepares a transparent bismaleimide resin alloy material with excellent properties. This alloy material not only possesses high transparency and excellent heat resistance, but also high mechanical strength and chemical stability. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The structural formula of 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (Pa);

[0021] Figure 2 The structural formula of bismaleimide (BMI);

[0022] Figure 3 (a) DSC curves of Pa / BMI blends with different BMI weight contents; (b) DSC curves of Pa / BMI blends with 20 wt% BMI content after each curing stage at different temperatures;

[0023] Figure 4 Infrared spectra of Pa / BMI blends with a BMI content of 20 wt% after each curing stage at 50℃(a), 160℃(b), 200℃(c) and 240℃(d);

[0024] Figure 5 Viscoelastic analysis of polymers with different Pa / BMI ratios;

[0025] Figure 6 TGA curves of Pa / BMI polymer alloys at different ratios;

[0026] Figure 7 Schematic diagram of the thermal reaction between polybenzoxazine and bismaleimide. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The technical problem solved by this invention is to broaden the operating temperature range of polybenzoxazine, improve its thermal stability and flame retardancy, and enable its use under harsh conditions.

[0029] Example 1

[0030] Please see Figure 1-7This invention provides a technical solution: a method for preparing a benzoxazine and bismaleimide transparent resin alloy, comprising the following steps:

[0031] Step 1: Prepare the required materials: bismaleimide, benzoxazine, solvent, and crosslinking agent;

[0032] Benzoxazine contains 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (Pa).

[0033] Step 2: Mix bismaleimide and benzoxazine in a mass ratio of 20 / 80, 40 / 60, 50 / 50, 70 / 30 and 80 / 20, and add an appropriate amount of chloroform solvent. Stir for a period of time to form a homogeneous mixture.

[0034] Step 3: Add an appropriate amount of crosslinking agent to the mixture and stir thoroughly for 30-60 minutes to ensure uniform dispersion and form a blend solution;

[0035] Step 4: Cast the blend solution onto a glass plate pretreated with dimethyldichlorosilane, dry it at 50°C for 4-6 hours, and then heat treat it at different temperatures for 1-3 hours to obtain the alloy film.

[0036] Step 5: Perform performance tests on the alloy films obtained with different mixing ratios and different heat treatment temperatures.

[0037] Polymer alloys were prepared by blending BMI and benzoxazine followed by heat treatment. The blends of benzoxazine and BMI were yellow and opaque after drying at 50°C for 4 hours; however, all blend films became transparent after curing at 160°C, above the melting point of BMI. At high benzoxazine contents, the film cured to 240°C was dark red, turning brown with increasing BMI content. Furthermore, the alloy film obtained by casting onto a glass plate without surface treatment with dichlorodimethylsilane was difficult to peel from the glass due to the very strong adhesion and high hydrophilicity of polybenzoxazine. The resulting alloy film exhibited improved toughness compared to the pure benzoxazine film, and the toughness of the alloy film increased with increasing BMI content.

[0038] Example 2

[0039] Please see Figure 1-7A method for preparing a benzoxazine-bismaleimide transparent resin alloy includes the following steps: mixing 80g of benzoxazine (Pa), 20g of bismaleimide (BMI), and 2g of crosslinking agent in chloroform and stirring for 30 minutes to form a blend solution. The blend solution is then cast onto a glass plate pretreated with dimethyldichlorosilane, dried at 50°C for 4 hours, and then heat-treated at 100°C, 120°C, 160°C, 200°C, and 240°C for 1 hour respectively to obtain an alloy film.

[0040] Characterization: The Pa / BMI polymer alloy was characterized using infrared spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC).

[0041] The DSC curves show a sharp exothermic peak in the ring-opening polymerization of the original Pa, starting at approximately 198 °C and reaching a maximum at 222 °C, with an exothermic value of 57 cal / g. The exothermic reaction of the original BMI begins at approximately 171 °C, reaches a maximum at 207 °C, and corresponds to an endothermic peak of 37 cal / g after the melting of BMI. It is clearly evident that the exothermic reaction of the blend is greater than that of Pa and BMI. The DSC results indicate that other reactions occurred simultaneously with the homopolymerization of benzoxazine and BMI.

[0042] The DSC curves of the Pa / BMI blend with a 20 wt% BMI content, cured at different temperatures, showed a single exothermic peak, corresponding to the ring-opening polymerization of Pa and the addition polymerization of BMI. The exothermic effect gradually decreased with increasing heat treatment temperature and disappeared completely after heat treatment at 240 °C. These results indicate that the reaction between benzoxazine and BMI occurs simultaneously and is completed at 240 °C.

[0043] Infrared spectrum ( Figure 4 The alloy of Pa and BMI (BMI: 20 wt%) was shown. Benzooxazine at 1037 cm⁻¹ -1 and 952 cm -1 Characteristic absorption at 3101cm -1 The characteristic absorptions of BMI were observed before curing. These characteristic absorptions decreased simultaneously with the curing process and disappeared after curing at 240°C, indicating that the double bond reaction and the ring-opening reaction of benzoxazine in BMI occurred simultaneously and were completed at a temperature consistent with the DSC results. At 1187 cm⁻¹ -1 The characteristic absorption at the site is attributed to ether bonds (COC), which increase as curing progresses.

[0044] The viscoelastic properties of benzoxazine / bismaleimide (BMI) alloys were investigated using DMA. The temperature dependence of the storage modulus (E') and loss modulus (E') of pure polybenzoxazine and the polymer alloy was studied. The presence of only one Tg in all alloy films indicates that the two components in this invention are well miscible or co-crosslinked. With increasing BMI content, the Tg of the polymer alloy shifts towards higher temperatures, indicating that the addition of BMI is effective in improving the properties of polybenzoxazine.

[0045] TGA curve ( Figure 6 It can be seen that with the increase of BMI content, the T5 and T10 values ​​of polybenzoxazine gradually shift towards higher temperatures, indicating that the addition of BMI is effective in improving the thermal stability of polybenzoxazine. Furthermore, compared with homopolymers, the char yield of polymer alloys is increased, indicating that alloying also improves flame retardancy.

[0046] In summary, this process uses bismaleimide and benzoxazine as main raw materials, and through specific formulations and process steps, prepares a transparent bismaleimide resin alloy material with excellent properties. This alloy material not only possesses high transparency and excellent heat resistance, but also high mechanical strength and chemical stability. The polymer alloy is an AB co-crosslinked polymer network formed by ether bonds between the hydroxyl groups of polybenzoxazine and the double bonds of bismaleimide. Viscoelastic analysis and softening temperature measurements show that the polymer alloy has a glass transition temperature much higher than that of each homopolymer. With increasing BMI content, the color of the alloy film gradually changes from dark red to brown. Thermal stability also increases with increasing bismaleimide content. The DMA measurement of the polymer alloy shows only one Tg, also indicating the formation of an AB co-crosslinked structure. By increasing the BMI content, the Tg of the polymer alloy shifts to higher temperatures. In particular, the Tg of the polymer alloy at high BMI content is even higher than that of the two single resins.

[0047] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. It should be noted that implementations not illustrated or described in the drawings or the main text of the specification are forms known to those skilled in the art and are not described in detail. Furthermore, the definitions of the components described above are not limited to the various specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or substitute them.

[0048] Those skilled in the art will understand that the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0049] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a transparent resin alloy of benzoxazine and bismaleimide, characterized in that: Includes the following steps: Step 1: Prepare the required materials: bismaleimide, benzoxazine, solvent, and crosslinking agent; Step 2: Mix bismaleimide and benzoxazine in a certain proportion, add an appropriate amount of solvent, and stir for a period of time to form a homogeneous mixture; Step 3: Add an appropriate amount of crosslinking agent to the mixture and stir thoroughly to disperse it evenly and form a blend solution; Step 4: Cast the blend solution onto a glass plate pretreated with dimethyldichlorosilane, dry it at 50°C for 4-6 hours, and then heat treat it at different temperatures for 1-3 hours to obtain the alloy film. Step 5: Perform performance tests on the alloy films obtained with different mixing ratios and different heat treatment temperatures.

2. The method for preparing a benzoxazine and bismaleimide transparent resin alloy according to claim 1, characterized in that: In step four, the blend solution is cast onto a glass plate pretreated with dimethyldichlorosilane, dried at 50°C for 4 hours, and then heat-treated at 100°C, 120°C, 160°C, 200°C, and 240°C for 1 hour respectively to obtain an alloy film.

3. The method for preparing a benzoxazine and bismaleimide transparent resin alloy according to claim 1, characterized in that: The solvent in step one is chloroform.

4. The method for preparing a benzoxazine and bismaleimide transparent resin alloy according to claim 1, characterized in that: Benzooxazine contains 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine.

5. The method for preparing a benzoxazine and bismaleimide transparent resin alloy according to claim 1, characterized in that: The mass ratio of bismaleimide and benzoxazine is one of 20 / 80, 40 / 60, 50 / 50, 70 / 30 and 80 / 20.

6. The method for preparing a benzoxazine and bismaleimide transparent resin alloy according to claim 1, characterized in that: The different heat treatment temperatures in step five are 100℃, 120℃, 160℃, 200℃, and 240℃.

7. The method for preparing a benzoxazine and bismaleimide transparent resin alloy according to claim 1, characterized in that: The stirring time in step three is 30-60 minutes.

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