Polyphosphazene random copolymer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polyphosphazene binders, and particularly discloses a polyphosphazene random copolymer as well as a preparation method and application thereof. Bromine-containing aryloxy and bromine-free aryloxy are bonded to a polyphosphazene main chain in a random copolymerization mode, and the matrix resin with an adjustable structure and good compatibility and reaction activity is obtained. After the polyphosphazene resin is prepared into an adhesive, interface chemical bonding can be realized by utilizing the structural similarity and vulcanization synchronism of the polyphosphazene resin and a polyphosphazene base material, so that the bonding strength is obviously improved to 2.0 MPa or above. The method effectively solves the technical problems of low interface bonding strength and insufficient reliability between a polyphosphazene material and a metal or composite material shell, and has important application value in the field of manufacturing of high-end equipment such as aerospace and the like.

Description

Technical Field

[0001] This invention relates to the field of polyphosphazene adhesives, and more particularly to a polyphosphazene random copolymer, its preparation method, and its application. Background Technology

[0002] Polyphosphazenes are a class of linear inorganic-organic hybrid polymer materials whose main chain is composed of alternating single and double bonds between phosphorus and nitrogen atoms. Each phosphorus atom in their molecular structure can be connected to two identical or different organic side groups. This unique structure endows polyphosphazenes with excellent structural designability. By selectively modifying the side groups, key indicators such as polarity, thermal stability, and mechanical properties can be controlled to meet the application requirements of different scenarios. Among them, aryloxy polyphosphazenes, as a class of polyphosphazene materials with phenoxy or phenoxy derivatives as side groups, have attracted widespread attention in high-end fields such as aerospace and weaponry due to their excellent thermal stability, unique char formation mechanism, and excellent resistance to ablation and combustion gas erosion. They are particularly suitable for the preparation of key components such as insulation layers and liners for solid rocket engines.

[0003] In the structural design of solid rocket motors, the bonding reliability between the shell and the insulation and lining layers directly determines the operational safety and service life of the motor. Effective load transfer and interface integrity both depend on the adhesive performance. Currently, improving the bonding strength between polyphosphazene materials (especially aryloxy polyphosphazene, PDPP) and the rocket motor shell has become a research hotspot in the field of aerospace materials.

[0004] However, the low content of polar functional groups and poor surface activity in the molecular structure of ordinary aryloxy polyphosphazenes result in weak interfacial interactions between them and engine casings (metals or composite materials). This leads to a bonding interface primarily based on physical adsorption, resulting in generally low bond strength. Existing adhesives on the market are mostly suitable for bonding traditional elastomers such as natural rubber and EPDM rubber to metals, lacking specialized adhesives for polyphosphazenes and rocket engine casings. Even with imported adhesives, the bond strength only reaches 1.2~1.4 MPa, making it difficult to guarantee the long-term reliability of the casing-insulation interface and hindering the further engineering application of high-performance polyphosphazene materials.

[0005] Therefore, developing a high-performance special adhesive that can significantly improve the interfacial bonding strength between polyphosphazene materials (especially aryloxy polyphosphazene) and engine housing and meet the requirements of use in extreme environments has important theoretical significance and engineering application value. Summary of the Invention

[0006] To address the problem of low bonding strength between commonly used adhesives and polyphosphazene materials and engine housings in existing technologies, this invention provides a polyphosphazene random copolymer, its preparation method, and its application.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a polyphosphazene random copolymer, the polyphosphazene random copolymer containing structural unit A of formula (I), structural unit B of formula (II), and structural unit C of formula (III):

[0008] Wherein, R is selected from H, C1~C5 straight-chain or branched alkyl groups; a and b are positive integers from 1 to 2; The molar percentage of R substituents in the polyphosphazene random copolymer is 10% to 90%, and the molar percentage of Br in the polyphosphazene random copolymer is 90% to 10%.

[0009] Compared with the prior art, the present invention provides a random copolymer with side chains containing specific bromine-containing and non-bromine-containing aryl groups. The molecular structure of the random copolymer is highly similar to that of the polyphosphazene matrix material, which improves its wettability and interfacial affinity with the polyphosphazene substrate. At the same time, the introduced bromine-containing side groups (bromophenoxy groups) significantly increase the polarity of the molecules, enhance their physical and chemical interactions with the surface of metals or composite materials, thereby helping to significantly improve interfacial adhesion.

[0010] Furthermore, this copolymer shares the same phosphazene backbone structure as the polyphosphazene substrate, and its side group design allows it to retain similar or identical active crosslinking sites. During thermal vulcanization, the vulcanization rates of the two are similar, enabling simultaneous crosslinking and curing. At the vulcanization temperature, the molecular chain segments of the random copolymer and the surface layer of the polyphosphazene substrate interdiffusion, and the active sites of both undergo covalent crosslinking reactions at the interface region, thereby generating strong chemical bonds in situ between them. This achieves molecular-level fusion of the two phases, fundamentally overcoming the defect of traditional adhesives that rely solely on physical adsorption generated by van der Waals forces, which easily leads to interfacial failure.

[0011] Further, R is selected from H, C1~C4 straight-chain or branched alkyl groups; the molar percentage of R substituent in the polyphosphazene random copolymer is 30%~70%, and the molar percentage of Br in the polyphosphazene random copolymer is 70%~30%.

[0012] Secondly, the present invention provides a method for preparing a polyphosphazene random copolymer, comprising the following steps: Polydichlorophosphazene is dissolved in an organic solvent to obtain a polydichlorophosphazene solution; Add sodium bromophenoxy as shown in formula (a) and sodium phenoxy as shown in formula (b) to the polydichlorophosphazene solution, and heat to carry out a substitution reaction to obtain a random copolymer of polyphosphazene.

[0013] Wherein, R is selected from H, C1~C5 straight-chain or branched alkyl groups; a and b are positive integers from 1 to 2.

[0014] This invention involves the simultaneous addition of two different sodium phenolate salts, which enable them to competitively and synchronously attack the chlorine atoms on the polydichlorophosphazene chain during the reaction. This ensures that the two different side groups (containing bromoaryloxy and not containing bromoaryloxy) can be randomly bonded to the same polymer backbone, resulting in a random copolymer. This synthetic method eliminates the need for complex intermediate separation or purification steps, exhibits good process stability and reproducibility, and is easily scalable for mass production.

[0015] Specifically, the sodium bromophenoxy can be selected from one or more of the sodium salts of p-bromophenol, 2-bromophenol, 3-bromophenol, 3,5-dibromophenol, and 2,6-dibromophenol; the sodium phenoxy can be selected from one or more of the sodium salts of phenol, m-methylphenol, 2,4-dimethylphenol, 4-butylphenol, or 2-propylphenol.

[0016] Furthermore, the organic solvent includes one or more of xylene, ethyl acetate, butyl acetate, tetrahydrofuran, or cyclohexane.

[0017] Furthermore, the molecular weight M of the polydichlorophosphazene is... w =300,000~800,000, molecular weight distribution PDI=1.3~2.5.

[0018] It should be noted that the above-mentioned polydichlorophosphazene can be prepared by conventional bulk melt polymerization or solution polymerization methods in the art, and for details, please refer to the ring-opening polymerization method reported in CN113150287B.

[0019] Furthermore, the molar ratio of the polydichlorophosphazene to the total amount of bromophenoxy sodium and phenoxy sodium is 1:1.1~1.3, wherein the molar ratio of bromophenoxy sodium and phenoxy sodium is 1:9~9:1.

[0020] Furthermore, the molar ratio of sodium bromophenoxy and sodium phenoxy is 3:7 to 7:3.

[0021] It should be noted that the raw materials used in this invention, such as sodium bromophenoxy as shown in formula (a) and sodium phenoxy as shown in formula (b), can all be prepared by conventional methods well known to those skilled in the art through the reaction of corresponding phenolic compounds with hydrides, hydroxides, carbonates of alkali metals (such as sodium). This invention does not impose any special limitations.

[0022] Furthermore, the temperature of the substitution reaction is 80℃~140℃, and the reaction time is 10h~72h.

[0023] Preferably, the temperature of the substitution reaction is 100℃~120℃, and the reaction time is 20h~30h.

[0024] It should be noted that after the above substitution reaction is completed, the reaction solution is added to a precipitant to precipitate the product, and then dried to obtain a polyphosphazene random copolymer.

[0025] Specifically, the precipitant is one or more of petroleum ether, hexane, ethanol, or water.

[0026] Specifically, the drying temperature is 40℃~120℃.

[0027] Thirdly, the present invention provides the application of the above-mentioned polyphosphazene random copolymer in bonding polyphosphazene materials and rigid structures.

[0028] Specifically, the polyphosphazene material mainly refers to polyphosphazenes with aryloxy groups substituted, such as polydiphenoxyphosphazene (PDPP). The rigid material mainly refers to components that can provide main support and load-bearing capacity, such as metal shells made of steel, aluminum, titanium alloys, etc., or composite material shells reinforced with carbon fiber / glass fiber.

[0029] The random copolymer of polyphosphazene provided by this invention is particularly suitable for solving the key technical problem of insufficient interfacial bonding strength between aryloxy polyphosphazene (such as PDPP) insulation layer / liner and metal or composite material shell in the aerospace field (such as solid rocket engines). It provides key material support for the structural safety of equipment such as solid rocket engines and has significant engineering application value.

[0030] Fourthly, the present invention provides an adhesive composition comprising the above-described polyphosphazene random copolymer.

[0031] Furthermore, the adhesive composition further includes a dispersant, a reinforcing agent, a vulcanizing agent, a vulcanization aid, a resin, a silane coupling agent, and an organic solvent.

[0032] Using the polyphosphazene random copolymer provided by this invention as the matrix material, and compounded with conventional functional additives in the art, a high-performance polyphosphazene-based adhesive composition can be prepared. This adhesive composition is particularly suitable for bonding solid rocket motor casings to insulation layers and liners, with interfacial bond strength reaching over 2.0 MPa, thus providing key material assurance for improving the reliability and safe operation of solid rocket motors.

[0033] Furthermore, the dispersant includes one or more of stearic acid, zinc stearate, pentaerythritol stearate, polyethylene wax, sodium lauryl sulfate, and polymethyl methacrylate.

[0034] Furthermore, the reinforcing agent includes one or more of carbon black, silica, zinc oxide, magnesium oxide, and calcium carbonate.

[0035] Furthermore, the vulcanizing agent includes one or more of sulfur, tetramethylthiuram disulfide, zinc oxide, magnesium oxide, dicumyl peroxide, benzoyl peroxide, and 2,5-dimethyl-2,5-di-tert-butylperoxide.

[0036] Further, the vulcanizing aid includes one or more of 2-thiol-benzothiazole, dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, tetramethylthiuram disulfide, zinc dibutyldithiocarbamate, diphenylguanidine, or zinc dimethyldithiocarbamate.

[0037] Furthermore, the resin includes one or more of epoxy resin, phenolic resin, or polyimide.

[0038] Furthermore, the silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, or γ-mercaptopropyltriethoxysilane.

[0039] Furthermore, the organic solvent includes one or more of xylene, ethyl acetate, butyl acetate, tetrahydrofuran, or cyclohexane.

[0040] Further, the mass concentration of the polyphosphazene random copolymer in the organic solvent is 8% to 15%; based on the mass of the polyphosphazene random copolymer as 100%, the content of the dispersant is 0.5% to 20%, the content of the reinforcing agent is 5% to 40%, the content of the vulcanizing agent is 0.5% to 20%, the content of the vulcanizing aid is 0.5% to 20%, the content of the resin is 20% to 80%, and the content of the silane coupling agent is 3% to 40%.

[0041] Preferably, the mass concentration of the polyphosphazene random copolymer in the organic solvent is 8% to 12%; based on 100% of the mass of the polyphosphazene random copolymer, the content of the dispersant is 1% to 3%, the content of the reinforcing agent is 30% to 35%, the content of the vulcanizing agent is 1% to 2%, the content of the vulcanizing aid is 15% to 20%, the content of the resin is 50% to 60%, and the content of the silane coupling agent is 10% to 40%.

[0042] Specifically, the preparation method of the above adhesive composition includes the following steps: The polyphosphazene random copolymer is dissolved in an organic solvent, and a dispersant, reinforcing agent, vulcanizing agent, vulcanization aid, resin, and silane coupling agent are added. The mixture is stirred for 6 to 10 hours to obtain an adhesive composition.

[0043] In summary, this invention provides an adhesive based on a mixed-substituted polyphosphazene random copolymer, its preparation method, and its application in bonding polyphosphazene materials to rigid structures, particularly suitable for high-strength bonding of solid rocket motor casings to aryloxy polyphosphazene insulation layers / linings. This invention achieves this by randomly copolymerizing bromoaryloxy groups with non-bromoaryloxy groups onto the polyphosphazene backbone, resulting in a matrix resin with tunable structure, good compatibility, and high reactivity. After being formulated into an adhesive, its structural similarity and simultaneous vulcanization with the polyphosphazene substrate enable interfacial chemical bonding, significantly increasing the bond strength to over 2.0 MPa. This invention effectively solves the technical problem of low interfacial bond strength and insufficient reliability between polyphosphazene materials and metal or composite material casings, and has significant application value in high-end equipment manufacturing fields such as aerospace. Attached Figure Description

[0044] Figure 1 The image shows a photograph of the adhesive composition prepared in Example 1 of this invention after it damaged the bond between 45# steel and PDPP. The dashed box is a magnified view of a part of the sample. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] Unless otherwise specified, all reagents used in the following embodiments are commercially available analytical grade reagents, and all experimental and detection methods used in the following embodiments are existing experimental and detection methods.

[0047] To better illustrate the present invention, further examples are provided below.

[0048] The phenolic metal salts such as sodium bromophenoxy and sodium phenoxy in the following examples and comparative examples can all be prepared by reacting the corresponding phenolic compounds with sodium hydride.

[0049] The polydichlorophosphazene (PDCP) used in the following examples and comparative examples was prepared according to the ring-opening polymerization method reported in CN113150287B. The molecular weight M of the prepared polydichlorophosphazene was... w =300,000~800,000, molecular weight distribution PDI=1.3~2.5.

[0050] Example 1 This embodiment provides a method for preparing a polyphosphazene random copolymer, comprising the following steps: Dissolve 10g of polydichlorophosphazene in 80mL of xylene to obtain a polydichlorophosphazene solution; Dissolve 0.1506 mol of sodium p-bromophenolate and 0.0717 mol of sodium phenolate in 80 mL of tetrahydrofuran to obtain a mixed sodium salt solution; A polydichlorophosphazene solution was added dropwise to a mixed sodium salt solution and reacted at 110°C for 24 hours. The reaction solution was then poured into a mixed solution of 2000 mL water and 2000 mL n-hexane for precipitation. The resulting precipitate was vacuum dried in a 60°C oven to constant weight to obtain a polyphosphazene random copolymer with a molecular weight M. w =620000, molecular weight distribution PDI=1.4.

[0051] This embodiment provides an adhesive composition comprising the following components: 2g polyphosphazene random copolymer, 0.1g zinc oxide, 0.04g stearic acid, 0.03g sulfur, 0.6g carbon black, 0.1g dibenzothiazole disulfide, 0.3g tetramethylthiuram disulfide, 1g phenolic resin 2402, 0.2g γ-aminopropyltriethoxysilane, 20mL ethyl acetate.

[0052] Weigh each component according to the above proportions, dissolve the weighed polyphosphazene random copolymer in ethyl acetate, then add the remaining components, and stir magnetically for 10 hours to obtain the adhesive composition.

[0053] The adhesive composition prepared above was used to bond polyaryloxy polyphosphazene (PDPP) and 45# steel. The specific steps are as follows: PDPP was compounded and prepared into samples measuring 25mm × 12.5mm × 2mm. 45# steel plates were processed into test pieces of the same size. The bonding surfaces of the 45# steel plates were uniformly sanded with sandpaper to remove the oxide layer and stains. Then, the bonding surfaces of the steel plates and PDPP samples were cleaned with anhydrous ethanol to remove oil and dust, and then dried. The adhesive composition prepared in the example was uniformly coated onto the bonding areas on both sides of the PDPP test piece and the bonding area of ​​one layer of the 45# steel plate, with a coating thickness of 0.2mm. Then, one 45# steel plate, the coated PDPP test piece, and another 45# steel plate were stacked sequentially, with the PDPP test piece positioned between the two steel plates. The plates were fixed with clamps and left to air dry for 2 hours until the solvent completely evaporated. The assembled specimen was placed in a mold and then placed in a programmed oven where the temperature was increased to 160°C at a rate of 2°C / min for 4 hours for vulcanization. The cured specimen was then tested using a universal tensile testing machine according to the method specified in national standard GB / T 13936-2014. A tensile test was performed at a tensile rate of 50 mm / min, with continuous loading until the bonded joint failed. The maximum load was recorded, and the failure mode of the specimen was recorded using a digital camera. Figure 1 As shown.

[0054] The tensile strength obtained from the test was 2.6 MPa. Figure 1As shown, after the tensile shear test, the bonded joint was damaged, exposing a yellowish-brown interface. This color is consistent with the body color of the PDPP substrate and is significantly different from the black adhesive layer. This phenomenon directly indicates that the damage occurred inside the PDPP substrate, suggesting that the interfacial bonding strength between the adhesive and PDPP exceeded the mechanical strength of the PDPP material itself. This confirms that the adhesive prepared in this embodiment of the invention achieves a super-strong bonding effect through interfacial chemical bonding.

[0055] Example 2 This embodiment provides a method for preparing a polyphosphazene random copolymer, comprising the following steps: Dissolve 10g of polydichlorophosphazene in 80mL of xylene to obtain a polydichlorophosphazene solution; Dissolve 0.0913 mol of sodium p-bromophenolate and 0.0913 mol of sodium phenolate in 80 mL of tetrahydrofuran to obtain a mixed sodium salt solution; A polydichlorophosphazene solution was added dropwise to a mixed sodium salt solution and reacted at 90°C for 30 hours. The reaction solution was then poured into a mixed solution of 2000 mL water and 2000 mL n-hexane for precipitation. The resulting precipitate was vacuum dried in a 60°C oven to constant weight to obtain a polyphosphazene random copolymer with a molecular weight M. w =510000, molecular weight distribution PDI=1.5.

[0056] This embodiment provides an adhesive composition comprising the following components: 2g polyphosphazene random copolymer, 0.1g zinc oxide, 0.01g stearic acid, 0.1g sulfur, 0.1g carbon black, 0.01g dibenzothiazole disulfide, 0.01g tetramethylthiuram disulfide, 0.4g phenolic resin 2402, 0.1g γ-glycidyl etheroxypropyltrimethoxysilane, 18mL ethyl acetate.

[0057] Weigh each component according to the above proportions, dissolve the weighed polyphosphazene random copolymer in ethyl acetate, then add the remaining components, and stir magnetically for 10 hours to obtain the adhesive composition.

[0058] The adhesive composition prepared above was used to bond polyaryloxy polyphosphazene (PDPP) and 45# steel. The specific steps are as follows: PDPP was compounded and prepared into samples measuring 25mm × 12.5mm × 2mm. 45# steel plates were processed into test pieces of the same size. The bonding surfaces of the 45# steel plates were uniformly sanded with sandpaper to remove the oxide layer and stains. Then, the bonding surfaces of the steel plates and PDPP samples were cleaned with anhydrous ethanol to remove oil and dust, and then dried. The adhesive composition prepared in the example was uniformly coated onto the bonding areas on both sides of the PDPP test piece and the bonding area of ​​one layer of the 45# steel plate, with a coating thickness of 0.2mm. Then, one 45# steel plate, the coated PDPP test piece, and another 45# steel plate were stacked sequentially, with the PDPP test piece positioned between the two steel plates. The plates were fixed with clamps and left to air dry for 2 hours until the solvent completely evaporated. The assembled sample was placed in a mold and then placed in a programmable oven at a rate of 2℃ / min to 160℃ for 3 hours of curing. The cured sample was then tested using a universal tensile testing machine according to the method specified in national standard GB / T 13936-2014. The tensile test was performed at a tensile rate of 50 mm / min, and the load was continuously applied until the bonded joint failed. The maximum load was recorded, and the tensile strength obtained was 2.8 MPa.

[0059] Example 3 This embodiment provides a method for preparing a polyphosphazene random copolymer, comprising the following steps: Dissolve 10g of polydichlorophosphazene in 80mL of xylene to obtain a polydichlorophosphazene solution; Dissolve 0.1506 mol of sodium p-bromophenolate and 0.0717 mol of sodium 2,4-dimethylphenolate in 80 mL of tetrahydrofuran to obtain a mixed sodium salt solution. A polydichlorophosphazene solution was added dropwise to a mixed sodium salt solution and reacted at 100°C for 25 hours. The reaction solution was then poured into a mixed solution of 2000 mL water and 2000 mL n-hexane for precipitation. The resulting precipitate was vacuum dried in a 60°C oven to constant weight to obtain a polyphosphazene random copolymer with a molecular weight M. w =620000, molecular weight distribution PDI=1.4.

[0060] This embodiment provides an adhesive composition comprising the following components: 2g polyphosphazene random copolymer, 0.2g zinc oxide, 0.4g zinc stearate, 0.01g dicumyl peroxide, 0.6g silica, 0.1g diphenylguanidine, 0.3g tetramethylthiuram disulfide, 1.2g phenolic resin 2402, 0.8g γ-methacryloyloxypropyltrimethoxysilane, 20mL xylene.

[0061] Weigh each component according to the above proportions, dissolve the weighed polyphosphazene random copolymer in xylene, then add the remaining components, and stir magnetically for 10 hours to obtain the adhesive composition.

[0062] The adhesive composition prepared above was used to bond polyaryloxy polyphosphazene (PDPP) and 45# steel. The specific steps are as follows: PDPP was compounded and prepared into samples measuring 25mm × 12.5mm × 2mm. 45# steel plates were processed into test pieces of the same size. The bonding surfaces of the 45# steel plates were uniformly sanded with sandpaper to remove the oxide layer and stains. Then, the bonding surfaces of the steel plates and PDPP samples were cleaned with anhydrous ethanol to remove oil and dust, and then dried. The adhesive composition prepared in the example was uniformly coated onto the bonding areas on both sides of the PDPP test piece and the bonding area of ​​one layer of the 45# steel plate, with a coating thickness of 0.2mm. Then, one 45# steel plate, the coated PDPP test piece, and another 45# steel plate were stacked sequentially, with the PDPP test piece positioned between the two steel plates. The plates were fixed with clamps and left to air dry for 2 hours until the solvent completely evaporated. The assembled sample was placed in a mold and then placed in a programmable oven at a rate of 2℃ / min to 160℃ for 3 hours of curing. The cured sample was then tested using a universal tensile testing machine according to the method specified in national standard GB / T 13936-2014. The tensile test was performed at a tensile rate of 50 mm / min, and the load was continuously applied until the bonded joint failed. The maximum load was recorded, and the tensile strength obtained was 2.7 MPa.

[0063] Example 4 This embodiment provides a method for preparing a polyphosphazene random copolymer, comprising the following steps: Dissolve 10g of polydichlorophosphazene in 80mL of xylene to obtain a polydichlorophosphazene solution; Dissolve 0.0717 mol of sodium m-bromophenolate and 0.1506 mol of sodium phenolate in 80 mL of tetrahydrofuran to obtain a mixed sodium salt solution; A polydichlorophosphazene solution was added dropwise to a mixed sodium salt solution and reacted at 120°C for 20 hours. The reaction solution was then poured into a mixed solution of 2000 mL water and 2000 mL n-hexane for precipitation. The resulting precipitate was vacuum dried in a 60°C oven to constant weight to obtain a polyphosphazene random copolymer with a molecular weight M. w =400000, molecular weight distribution PDI=1.7.

[0064] This embodiment provides an adhesive composition comprising the following components: 2g polyphosphazene random copolymer, 0.2g magnesium oxide, 0.04g polyethylene wax, 0.02g sulfur, 0.3g carbon black, 0.05g dibenzothiazole disulfide, 0.1g tetramethylthiuram disulfide, 0.8g phenolic resin 2402, 0.5g γ-aminopropyltriethoxysilane, and 20mL butyl acetate.

[0065] Weigh each component according to the above proportions, dissolve the weighed polyphosphazene random copolymer in butyl acetate, then add the remaining components, and stir magnetically for 10 hours to obtain the adhesive composition.

[0066] The adhesive composition prepared above was used to bond polyaryloxy polyphosphazene (PDPP) and 45# steel. The specific steps are as follows: PDPP was compounded and prepared into samples measuring 25mm × 12.5mm × 2mm. 45# steel plates were processed into test pieces of the same size. The bonding surfaces of the 45# steel plates were uniformly sanded with sandpaper to remove the oxide layer and stains. Then, the bonding surfaces of the steel plates and PDPP samples were cleaned with anhydrous ethanol to remove oil and dust, and then dried. The adhesive composition prepared in the example was uniformly coated onto the bonding areas on both sides of the PDPP test piece and the bonding area of ​​one layer of the 45# steel plate, with a coating thickness of 0.2mm. Then, one 45# steel plate, the coated PDPP test piece, and another 45# steel plate were stacked sequentially, with the PDPP test piece positioned between the two steel plates. The plates were fixed with clamps and allowed to air dry for 2 hours until the solvent completely evaporated. The assembled sample was placed in a mold and then placed in a programmable oven at a rate of 2℃ / min to 160℃ for 3 hours of curing. The cured sample was then tested using a universal tensile testing machine according to the method specified in national standard GB / T 13936-2014. The tensile test was performed at a tensile rate of 50 mm / min, and the load was continuously applied until the bonded joint failed. The maximum load was recorded, and the tensile strength obtained was 2.5 MPa.

[0067] Example 5 This embodiment provides a method for preparing a polyphosphazene random copolymer, comprising the following steps: Dissolve 10g of polydichlorophosphazene in 80mL of xylene to obtain a polydichlorophosphazene solution; Dissolve 0.0944 mol of sodium p-bromophenolate and 0.0913 mol of sodium 4-butylphenolate in 80 mL of tetrahydrofuran to obtain a mixed sodium salt solution; A polydichlorophosphazene solution was added dropwise to a mixed sodium salt solution and reacted at 140°C for 15 hours. The reaction solution was then poured into a mixed solution of 2000 mL water and 2000 mL n-hexane for precipitation. The resulting precipitate was vacuum dried in a 60°C oven to constant weight to obtain a polyphosphazene random copolymer with a molecular weight M. w =360000, molecular weight distribution PDI=1.9.

[0068] This embodiment provides an adhesive composition comprising the following components: 2g polyphosphazene random copolymer, 0.1g magnesium oxide, 0.08g stearic acid, 0.4g tetramethylthiuram disulfide, 0.3g calcium carbonate, 0.1g dibenzothiazole disulfide, 0.1g zinc dimethyl dithiocarbamate, 1.5g epoxy resin E44, 0.06g γ-mercaptopropyltrimethoxysilane, 15mL ethyl acetate.

[0069] Weigh each component according to the above proportions, dissolve the weighed polyphosphazene random copolymer in ethyl acetate, then add the remaining components, and stir magnetically for 10 hours to obtain the adhesive composition.

[0070] The adhesive composition prepared above was used to bond polyaryloxy polyphosphazene (PDPP) and 45# steel. The specific steps are as follows: PDPP was compounded and prepared into samples measuring 25mm × 12.5mm × 2mm. 45# steel plates were processed into test pieces of the same size. The bonding surfaces of the 45# steel plates were uniformly sanded with sandpaper to remove the oxide layer and stains. Then, the bonding surfaces of the steel plates and PDPP samples were cleaned with anhydrous ethanol to remove oil and dust, and then dried. The adhesive composition prepared in the example was uniformly coated onto the bonding areas on both sides of the PDPP test piece and the bonding area of ​​one layer of the 45# steel plate, with a coating thickness of 0.2mm. Then, one 45# steel plate, the coated PDPP test piece, and another 45# steel plate were stacked sequentially, with the PDPP test piece positioned between the two steel plates. The plates were fixed with clamps and allowed to air dry for 1–3 hours until the solvent completely evaporated. The assembled sample was placed in a mold and then placed in a programmable oven at a rate of 2℃ / min to 160℃ for 3 hours of curing. The cured sample was then tested using a universal tensile testing machine according to the method specified in national standard GB / T 13936-2014. The tensile test was performed at a tensile rate of 50 mm / min, and the load was continuously applied until the bonded joint failed. The maximum load was recorded, and the tensile strength obtained was 3.2 MPa.

[0071] Example 6 This embodiment provides a method for preparing a polyphosphazene random copolymer, comprising the following steps: Dissolve 10g of polydichlorophosphazene in 80mL of xylene to obtain a polydichlorophosphazene solution; Dissolve 0.0188 mol of sodium p-bromophenolate and 0.1690 mol of sodium 2,6-dibromophenolate in 80 mL of tetrahydrofuran to obtain a mixed sodium salt solution; A polydichlorophosphazene solution was added dropwise to a mixed sodium salt solution and reacted at 110°C for 24 hours. The reaction solution was then poured into a mixed solution of 2000 mL water and 2000 mL n-hexane for precipitation. The resulting precipitate was vacuum dried in a 60°C oven to constant weight to obtain a polyphosphazene random copolymer with a molecular weight M. w =371000, molecular weight distribution PDI=2.2.

[0072] This embodiment provides an adhesive composition comprising the following components: 2g polyphosphazene random copolymer, 0.2g magnesium oxide, 0.06g stearic acid, 0.1g tetramethylthiuram disulfide, 0.4g calcium carbonate, 0.1g dibenzothiazole disulfide, 0.2g zinc dimethyl dithiocarbamate, 1.3g epoxy resin E44, 0.2g γ-mercaptopropyltrimethoxysilane, 15mL ethyl acetate.

[0073] Weigh each component according to the above proportions, dissolve the weighed polyphosphazene random copolymer in ethyl acetate, then add the remaining components, and stir magnetically for 10 hours to obtain the adhesive composition.

[0074] The adhesive composition prepared above was used to bond polyaryloxy polyphosphazene (PDPP) and 45# steel. The specific steps are as follows: PDPP was compounded and prepared into samples measuring 25mm × 12.5mm × 2mm. 45# steel plates were processed into test pieces of the same size. The bonding surfaces of the 45# steel plates were uniformly sanded with sandpaper to remove the oxide layer and stains. Then, the bonding surfaces of the steel plates and PDPP samples were cleaned with anhydrous ethanol to remove oil and dust, and then dried. The adhesive composition prepared in the example was uniformly coated onto the bonding areas on both sides of the PDPP test piece and the bonding area of ​​one layer of the 45# steel plate, with a coating thickness of 0.2mm. Then, one 45# steel plate, the coated PDPP test piece, and another 45# steel plate were stacked sequentially, with the PDPP test piece positioned between the two steel plates. The plates were fixed with clamps and allowed to air dry for 1–3 hours until the solvent completely evaporated. The assembled sample was placed in a mold and then placed in a programmable oven at a rate of 2℃ / min to 160℃ for 3 hours of curing. The cured sample was then tested using a universal tensile testing machine according to the method specified in national standard GB / T 13936-2014. The tensile test was performed at a tensile rate of 50 mm / min and the load was continuously applied until the bonded joint failed. The tensile strength obtained was 3.1 MPa.

[0075] Example 7 This embodiment provides a method for preparing a polyphosphazene random copolymer, comprising the following steps: Dissolve 10g of polydichlorophosphazene in 80mL of xylene to obtain a polydichlorophosphazene solution; Dissolve 0.1690 mol of sodium p-bromophenolate and 0.0188 mol of sodium 4-butylphenolate in 80 mL of tetrahydrofuran to obtain a mixed sodium salt solution; A polydichlorophosphazene solution was added dropwise to a mixed sodium salt solution and reacted at 110°C for 24 hours. The reaction solution was then poured into a mixed solution of 2000 mL water and 2000 mL n-hexane for precipitation. The resulting precipitate was vacuum dried in a 60°C oven to constant weight to obtain a polyphosphazene random copolymer with a molecular weight M. w =272000, molecular weight distribution PDI=2.4.

[0076] This embodiment provides an adhesive composition comprising the following components: 2g polyphosphazene random copolymer, 0.3g magnesium oxide, 0.15g stearic acid, 0.25g tetramethylthiuram disulfide, 0.2g calcium carbonate, 0.1g dibenzothiazole disulfide, 0.3g zinc dimethyl dithiocarbamate, 0.9g epoxy resin E44, 0.4g γ-mercaptopropyltrimethoxysilane, 15mL ethyl acetate.

[0077] Weigh each component according to the above proportions, dissolve the weighed polyphosphazene random copolymer in ethyl acetate, then add the remaining components, and stir magnetically for 10 hours to obtain the adhesive composition.

[0078] The adhesive composition prepared above was used to bond polyaryloxy polyphosphazene (PDPP) and 45# steel. The specific steps are as follows: PDPP was compounded and prepared into samples measuring 25mm × 12.5mm × 2mm. 45# steel plates were processed into test pieces of the same size. The bonding surfaces of the 45# steel plates were uniformly sanded with sandpaper to remove the oxide layer and stains. Then, the bonding surfaces of the steel plates and PDPP samples were cleaned with anhydrous ethanol to remove oil and dust, and then dried. The adhesive composition prepared in the example was uniformly coated onto the bonding areas on both sides of the PDPP test piece and the bonding area of ​​one layer of the 45# steel plate, with a coating thickness of 0.2mm. Then, one 45# steel plate, the coated PDPP test piece, and another 45# steel plate were stacked sequentially, with the PDPP test piece positioned between the two steel plates. The plates were fixed with clamps and allowed to air dry for 2 hours until the solvent completely evaporated. The assembled sample was placed in a mold and then placed in a programmable oven at a rate of 2℃ / min to 160℃ for 3 hours of curing. The cured sample was then tested using a universal tensile testing machine according to the method specified in national standard GB / T 13936-2014. The tensile test was performed at a tensile rate of 50 mm / min, and the load was continuously applied until the bonded joint failed. The maximum load was recorded, and the tensile strength obtained was 2.9 MPa.

[0079] Comparative Example 1 This comparative example provides a method for preparing a polyphosphazene random copolymer. The only difference from Example 5 is that sodium p-bromophenolate is replaced with an equal amount of sodium 2,4,6-tribromophenolate. All other aspects are the same. The resulting polyphosphazene random copolymer has a molecular weight of Mw = 360,000 and a molecular weight distribution PDI = 1.9.

[0080] The adhesive composition prepared by the above-mentioned polyphosphazene random copolymer was prepared according to the same formulation and method as in Example 5, and used to bond 45# steel and PDPP samples. The tensile strength was tested according to the same method and found to be 1.3 MPa.

[0081] Comparative Example 2 This comparative example provides a method for preparing a polyphosphazene random copolymer. The only difference from Example 5 is that sodium p-bromophenolate is replaced with an equal amount of sodium phenolate. The rest is exactly the same. A polyphosphazene random copolymer is prepared with a molecular weight of Mw = 500,000 and a molecular weight distribution PDI = 1.3.

[0082] The adhesive composition prepared by the above-mentioned polyphosphazene random copolymer was prepared according to the same formulation and method as in Example 5, and used to bond 45# steel and PDPP samples. The tensile strength was tested according to the same method and found to be 1.2 MPa.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A random copolymer of polyphosphazene, characterized in that, The polyphosphazene random copolymer contains structural unit A as shown in formula (Ⅰ), structural unit B as shown in formula (Ⅱ), and structural unit C as shown in formula (Ⅲ): Wherein, R is selected from H, C1~C5 straight-chain or branched alkyl groups; a and b are positive integers from 1 to 2; The molar percentage of R substituents in the polyphosphazene random copolymer is 10% to 90%, and the molar percentage of Br in the polyphosphazene random copolymer is 90% to 10%.

2. The method for preparing the polyphosphazene random copolymer according to claim 1, characterized in that, Includes the following steps: Polydichlorophosphazene is dissolved in an organic solvent to obtain a polydichlorophosphazene solution; Add sodium bromophenoxy as shown in formula (a) and sodium phenoxy as shown in formula (b) to the polydichlorophosphazene solution, and heat to carry out a substitution reaction to obtain a random copolymer of polyphosphazene. Wherein, R is selected from H, C1~C5 straight-chain or branched alkyl groups; a and b are positive integers from 1 to 2.

3. The method for preparing the polyphosphazene random copolymer as described in claim 2, characterized in that, The molecular weight M of the polydichlorophosphazene w =300,000~800,000, molecular weight distribution PDI=1.3~2.

5.

4. The method for preparing the polyphosphazene random copolymer as described in claim 2, characterized in that, The molar ratio of the polydichlorophosphazene to the total amount of bromophenoxy sodium and phenoxy sodium is 1:1.1~1.3, wherein the molar ratio of bromophenoxy sodium and phenoxy sodium is 1:9~9:

1.

5. The method for preparing the polyphosphazene random copolymer as described in claim 2, characterized in that, The substitution reaction is carried out at a temperature of 80℃ to 140℃ and for a reaction time of 10h to 72h.

6. The application of the polyphosphazene random copolymer of claim 1 in bonding polyphosphazene materials and rigid structures.

7. An adhesive composition, characterized in that, Including the polyphosphazene random copolymer of claim 1.

8. The adhesive composition according to claim 7, characterized in that, It also includes dispersants, reinforcing agents, vulcanizing agents, vulcanization aids, resins, silane coupling agents, and organic solvents.

9. The adhesive composition of claim 8, characterized in that, The dispersant comprises one or more of stearic acid, zinc stearate, pentaerythritol stearate, polyethylene wax, sodium lauryl sulfate, and polymethyl methacrylate; and / or The reinforcing agent includes one or more of carbon black, silica, zinc oxide, magnesium oxide, and calcium carbonate; and / or The vulcanizing agent includes one or more of sulfur, tetramethylthiuram disulfide, zinc oxide, magnesium oxide, dicumyl peroxide, benzoyl peroxide, and 2,5-dimethyl-2,5-di-tert-butylperoxide; and / or The vulcanization aid comprises one or more of 2-thiol-benzothiazole, dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, tetramethylthiuram disulfide, zinc dibutyldithiocarbamate, diphenylguanidine, or zinc dimethyldithiocarbamate; and / or The resin includes one or more of epoxy resin, phenolic resin, or polyimide; and / or The silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, or γ-mercaptopropyltriethoxysilane; and / or The organic solvent includes one or more of xylene, ethyl acetate, butyl acetate, tetrahydrofuran, or cyclohexane.

10. The adhesive composition according to claim 8 or 9, characterized in that, The mass concentration of the polyphosphazene random copolymer in the organic solvent is 8% to 15%; based on the mass of the polyphosphazene random copolymer as 100%, the content of the dispersant is 0.5% to 20%, the content of the reinforcing agent is 5% to 40%, the content of the vulcanizing agent is 0.5% to 20%, the content of the vulcanizing aid is 0.5% to 20%, the content of the resin is 20% to 80%, and the content of the silane coupling agent is 3% to 40%.

Images