A microporous polyphosphazene foam material and a method of preparation

Abstract

The application discloses a kind of microporous structure polyphosphazene foam material and its preparation method, the method is to be mixed with the mechanical stirring in organic solvent by polyphosphazene, vulcanizing agent, the ring crosslinking polyphosphazene microspheres of load foaming agent, after removing solvent, it is prepared by heat pressing pre-curing, foaming and post-curing to obtain microporous polyphosphazene foam material.The method of the application adds the ring crosslinking polyphosphazene microspheres of load foaming agent with foaming agent, heterogeneous nucleating agent and flame retardant effect, realizes the improvement of matrix foaming performance, and improves the flame retardancy of polyphosphazene foam at the same time;By controlling pre-curing condition, the content of ring crosslinking polyphosphazene microspheres of load foaming agent and post-curing condition, matrix crosslinking density, gas evolution and heterogeneous nucleation site number and cell growth process are regulated, and the cell morphology of polyphosphazene foam material can be effectively controlled.

Description

Technical Field

[0001] This invention belongs to the field of foam material technology, specifically relating to a microporous polyphosphazene foam material and its preparation method. Background Technology

[0002] Polyphosphazene is an inorganic / organic hybrid polymer with an alternating phosphorus and nitrogen atom main chain structure and organic groups such as aryloxy and alkoxy groups as side groups. The synergistic flame-retardant effect between phosphorus and nitrogen elements in the main chain gives it inherent flame-retardant advantages. Its diverse side group structure endows it with heat and cold resistance, chemical stability, flexibility, and biocompatibility. However, its high material density limits its applications. By introducing a microporous structure into polyphosphazene materials through foaming technology, materials with internal pore sizes ranging from 1 to 100 μm and pore densities greater than 10⁻⁶ were prepared. 7 pcs / cm 3 Microporous polyphosphazene materials can reduce the density of polyphosphazene materials, improve impact resistance, and reduce dielectric constant and thermal conductivity, showing great application value in aerospace, military, biomedicine, and flexible electronics. However, the low melt strength of the polyphosphazene bulk makes it difficult to contain the gas generated during foaming, causing bubble aggregation and collapse. Crosslinking can improve the melt strength of polyphosphazene, but the crosslinked network hinders bubble growth during foaming, which may cause matrix cracking, making the preparation of microporous polyphosphazene materials quite difficult.

[0003] Patent CN 118085586 A discloses a flame-retardant polyphosphazene foam material and its preparation method. This method employs a one-step foaming process within a mold. The cell structure of the prepared polyphosphazene foam material is affected by multiple factors, including the type and content of the foaming agent, vulcanizing agent, and various additives, as well as the vulcanization and foaming time and the foaming mold, resulting in poor controllability of the cell morphology. While the strategy of not adding flame retardants can minimize the adverse effects of flame-retardant fillers on material performance, it also limits further improvement in the material's flame-retardant properties.

[0004] Therefore, it is of great significance to study and develop a method for preparing microporous polyphosphazene foam materials, to solve the problems of poor controllability of cell morphology and limited improvement of flame retardant performance in the preparation of polyphosphazene foam materials by existing technologies, and to further enhance the application value of polyphosphazene foam materials. Summary of the Invention

[0005] The purpose of this invention is to provide a microporous polyphosphazene foam material and its preparation method, aiming to solve the problems of poor controllability of cell morphology and limited improvement of flame retardant performance in the preparation of polyphosphazene foam materials by existing technologies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a microporous polyphosphazene foam material includes the following steps: Step S1: Polyphosphazene is dissolved in dichloromethane to prepare adhesive solution A; Step S2: The foaming agent is dissolved in dimethyl sulfoxide, and then the cyclic cross-linked polyphosphazene microspheres are added to the solution and mechanically stirred. After filtration and removal of excess solvent, the cyclic cross-linked polyphosphazene microspheres loaded with foaming agent are obtained. In step S3, the cyclic cross-linked polyphosphazene microspheres containing vulcanizing agent and foaming agent are added to adhesive solution A, mechanically stirred until homogeneous, and the solvent is removed to obtain a mixed adhesive. Step S4: The mixed adhesive is placed in a mold and pre-cured by hot pressing to obtain the foamed precursor; Step S5: The foaming precursor is placed in an oven for foaming and post-curing to obtain microporous polyphosphazene foam.

[0008] Optionally, the cyclic cross-linked polyphosphazene microspheres are hydroxyl-containing cyclic cross-linked polyphosphazene microspheres.

[0009] Optionally, the foaming agent is at least one of azodicarbonamide, 4,4'-oxobis(benzenesulfonylhydrazine) and N,N-dinitropentamethylenetetramine.

[0010] Optionally, the vulcanizing agent is benzoyl peroxide and dicumyl peroxide; The mass ratio of benzoyl peroxide to polyphosphazene is 1:20-50; The mass ratio of dicumyl peroxide to polyphosphazene is 1:50 to 200.

[0011] Optionally, the hot-pressing pre-curing conditions are 100-120°C, 1-10 MPa, and 10-60 min.

[0012] Optionally, the foaming and post-curing conditions are 150–170°C and 30–60 min.

[0013] A microporous polyphosphazene foam material is prepared using any of the preparation methods for microporous polyphosphazene foam materials described in this invention.

[0014] The beneficial effects of this invention are as follows: 1. This invention incorporates loaded foaming agent cyclic crosslinked polyphosphazene microspheres that act as foaming agents, heterogeneous nucleating agents, and flame retardants, thereby improving the foaming performance of the matrix while enhancing the flame retardant properties of the polyphosphazene foam. 2. This invention uses pre-curing to prepare the foaming precursor, followed by foaming and post-curing processes. By controlling the pre-curing conditions, the content of the loaded foaming agent ring-crosslinked polyphosphazene microspheres, and the post-curing conditions, the crosslinking density of the matrix, the amount of gas generated, the number of heterogeneous nucleation sites, and the cell growth process can be regulated, which can effectively control the cell morphology of polyphosphazene foam materials. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 Here is a scanning electron microscope image of the microporous polyphosphazene foam material in Example 3; Figure 2 This is a scanning electron microscope image of the polyphosphazene foam material in Comparative Example 1. Detailed Implementation

[0016] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0017] The preparation method of the microporous polyphosphazene foam material of the present invention includes the following steps: Step S1: Polyphosphazene is dissolved in dichloromethane to prepare adhesive solution A; Step S2: The foaming agent is dissolved in dimethyl sulfoxide, and then the cyclic cross-linked polyphosphazene microspheres are added to the solution and mechanically stirred. After filtration and removal of excess solvent, the cyclic cross-linked polyphosphazene microspheres loaded with foaming agent are obtained. In step S3, the cyclic cross-linked polyphosphazene microspheres containing vulcanizing agent and foaming agent are added to adhesive solution A, mechanically stirred until homogeneous, and the solvent is removed to obtain a mixed adhesive. Step S4: The mixed adhesive is placed in a mold and pre-cured by hot pressing to obtain the foamed precursor; Step S5: The foaming precursor is placed in an oven for foaming and post-curing to obtain microporous polyphosphazene foam.

[0018] In the scheme disclosed herein, in S2, the foaming agent is one or more of azodicarbonamide (AC), 4,4'-oxobis(benzenesulfonylhydrazine) (OBSH), and N,N-dinitropentamethylenetetramine (foaming agent H).

[0019] In the disclosed scheme, S2, the cyclic cross-linked polyphosphazene microspheres are hydroxyl-containing cyclic cross-linked polyphosphazene microspheres, prepared by ultrasonic reaction of the monomers hexachlorocyclotriphosphazene and 4,4'-dihydroxydiphenyl sulfone. The hydroxyl-containing polyphosphazene microspheres refer to the synthetic monomers being hexachlorocyclotriphosphazene and 4,4'-dihydroxydiphenylmethane or 4,4'-dihydroxydiphenyl sulfone. The specific synthesis process is as follows: a certain mass of monomers are dissolved in acetonitrile, and after complete dissolution, a mixed solution is added. A certain amount of triethylamine is then added, and the mixture is placed in an ultrasonic reactor for 6 hours. After the reaction, centrifugation is performed, and the lower solid layer is washed three times with ethanol and deionized water, and then centrifuged again. Finally, the obtained product is vacuum dried to obtain the hydroxyl-containing polyphosphazene microspheres.

[0020] In the scheme disclosed herein, in S3, the mass ratios of BPO and DCP to polyphosphazene are 1:20-50 and 1:50-200, respectively.

[0021] In the scheme disclosed herein, in S4, the pre-curing conditions of the mixed adhesive are 100–120°C, 1–10 MPa, and 10–60 min.

[0022] In the scheme disclosed herein, in S5, the foaming and post-curing conditions are 150–170°C for 30–60 min.

[0023] Example 1: Step S1: Weigh 10g of polyphosphazene and dissolve it in 100ml of dichloromethane to prepare adhesive solution A; Step S2: Weigh 0.5g AC and dissolve it in 20ml dimethyl sulfoxide. Then add 1g of hydroxyl-containing cyclic cross-linked polyphosphazene microspheres to the solution and stir mechanically until uniform. Filter the solution and vacuum dry to remove excess solvent to obtain cyclic cross-linked polyphosphazene microspheres loaded with foaming agent. Step S3: Weigh 0.3g of BPO, 0.05g of DCP, and 1g of cyclic cross-linked polyphosphazene microspheres loaded with foaming agent and add them to adhesive solution A. After mechanical stirring and vacuum drying to remove the solvent, a mixed adhesive is obtained. Step S4: Place the mixed adhesive in a mold for hot pressing and pre-curing, and control the pre-curing conditions as 100℃, 3MPa, and 20min to obtain the foaming precursor. Step S5: Place the foaming precursor in an oven for foaming and post-curing, and control the conditions at 150℃ for 30 minutes to obtain microporous polyphosphazene foam.

[0024] Example 2: Step S1: Weigh 10g of polyphosphazene and dissolve it in 100ml of dichloromethane to prepare adhesive solution A; Step S2: Weigh 0.5g of OBSH and dissolve it in 20ml of dimethyl sulfoxide. Then add 1g of hydroxyl-containing cyclic cross-linked polyphosphazene microspheres to the solution and stir mechanically until uniform. Filter the solution and vacuum dry to remove excess solvent to obtain cyclic cross-linked polyphosphazene microspheres loaded with foaming agent. Step S3: Weigh 0.3g of BPO, 0.05g of DCP, and 1g of cyclic cross-linked polyphosphazene microspheres loaded with foaming agent and add them to adhesive solution A. After mechanical stirring and vacuum drying to remove the solvent, a mixed adhesive is obtained. Step S4: Place the mixed adhesive in a mold for hot pressing and pre-curing, and control the pre-curing conditions as 110℃, 5MPa, and 30min to obtain the foaming precursor. Step S5: Place the foaming precursor in an oven for foaming and post-curing, and control the conditions at 160℃ for 60 minutes to obtain microporous polyphosphazene foam.

[0025] Example 3: Step S1: Weigh 10g of polyphosphazene and dissolve it in 100ml of dichloromethane to prepare adhesive solution A; Step S2: Weigh 2g of foaming agent H and dissolve it in 20ml of dimethyl sulfoxide. Then add 1g of hydroxyl-containing cyclic cross-linked polyphosphazene microspheres to the solution and stir mechanically until uniform. Filter the solution and vacuum dry to remove excess solvent to obtain cyclic cross-linked polyphosphazene microspheres loaded with foaming agent. Step S3: Weigh 0.2g of BPO, 0.2g of DCP, and 2g of cyclic cross-linked polyphosphazene microspheres loaded with foaming agent and add them to adhesive solution A. After mechanical stirring and vacuum drying to remove the solvent, a mixed adhesive is obtained. Step S4: Place the mixed adhesive in a mold for hot pressing and pre-curing, and control the pre-curing conditions as 110℃, 7MPa, and 20min to obtain the foaming precursor. Step S5: Place the foaming precursor in an oven for foaming and post-curing, and control the conditions at 170℃ for 20 minutes to obtain microporous polyphosphazene foam.

[0026] Figure 1 Here are scanning electron microscope (SEM) images of the microporous polyphosphazene foam material from Example 3; Figure 1 The results show that the prepared polyphosphazene foam material has a uniform cell structure, and the calculated average cell diameter is 33.0 μm.

[0027] Comparative Example 1: Step S1: Weigh 10g of polyphosphazene and dissolve it in 100ml of dichloromethane to prepare adhesive solution A; Step S2: Weigh 0.5g BPO, 0.1g DCP and 0.5g foaming agent H and add them to adhesive solution A. Stir mechanically until uniform and vacuum dry to remove solvent to obtain mixed adhesive. Step S3: Place the mixed adhesive in a mold for hot pressing and pre-curing, and control the pre-curing conditions as 100℃, 5MPa, and 20min to obtain the foaming precursor. Step S4: Place the foaming precursor in an oven for foaming and post-curing, and control the conditions at 160℃ for 30 minutes to obtain polyphosphazene foam.

[0028] Figure 2 This is a scanning electron microscope (SEM) image of the polyphosphazene foam material in Comparative Example 1. Figure 2 The results show that the prepared foam material has poor foaming performance, with a calculated average cell diameter of 307.8 μm.

[0029] The polyphosphazene foams obtained in the examples and comparative examples were subjected to structural and performance tests, and the test results are shown in Table 1.

[0030] Table 1. Test results of polyphosphazene foam structure and performance.

[0031] As shown in Table 1, the limiting oxygen index of the polyphosphazene foam materials in Examples 1-3 increased from a minimum of 35.9% to a maximum of 38.4%, and the average cell diameter increased from a minimum of 27.4 μm to a maximum of 33.0 μm. In Comparative Example 1, the limiting oxygen index of the polyphosphazene foam material was only 29.3%, and the average cell diameter was 307.8 μm.

[0032] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0033] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0034] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing a microporous polyphosphazene foam material, characterized in that, Includes the following steps: Step S1: Polyphosphazene is dissolved in dichloromethane to prepare adhesive solution A; Step S2: The foaming agent is dissolved in dimethyl sulfoxide, and then the cyclic cross-linked polyphosphazene microspheres are added to the solution and mechanically stirred. After filtration and removal of excess solvent, the cyclic cross-linked polyphosphazene microspheres loaded with foaming agent are obtained. Step S3: The cyclic cross-linked polyphosphazene microspheres containing vulcanizing agent and foaming agent are added to adhesive solution A, mechanically stirred until homogeneous, and the solvent is removed to obtain a mixed adhesive. Step S4: The mixed adhesive is placed in a mold and pre-cured by hot pressing to obtain the foamed precursor; Step S5: The foaming precursor is placed in an oven for foaming and post-curing to obtain microporous polyphosphazene foam.

2. The method for preparing microporous polyphosphazene foam material according to claim 1, characterized in that, The cyclic cross-linked polyphosphazene microspheres are hydroxyl-containing cyclic cross-linked polyphosphazene microspheres.

3. The method for preparing microporous polyphosphazene foam material according to claim 1 or 2, characterized in that, The foaming agent is at least one of azodicarbonamide, 4,4'-oxobis(benzenesulfonylhydrazine) and N,N-dinitropentamethylenetetramine.

4. The method for preparing microporous polyphosphazene foam material according to claim 1 or 2, characterized in that, The vulcanizing agents are benzoyl peroxide and dicumyl peroxide; The mass ratio of benzoyl peroxide to polyphosphazene is 1:20-50; The mass ratio of dicumyl peroxide to polyphosphazene is 1:50 to 200.

5. The method for preparing microporous polyphosphazene foam material according to claim 1 or 2, characterized in that, The conditions for hot-pressing pre-curing are 100-120℃, pressure 1-10MPa, and time 10-60min.

6. The method for preparing the microporous polyphosphazene foam material according to claim 1 or 2, characterized in that, The foaming and post-curing conditions are 150–170°C and 30–60 min.

7. A microporous polyphosphazene foam material, characterized in that, It was prepared using the preparation method of the microporous polyphosphazene foam material according to any one of claims 1-6.

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