High-heat-resistance degradable epoxy resin composite material and preparation method thereof

Abstract

The invention belongs to the field of epoxy resin composite materials, and particularly relates to a high-heat-resistance degradable epoxy resin composite material and a preparation method thereof.The high-heat-resistance degradable epoxy resin composite material is prepared by using ester-based structure epoxy resin as matrix resin, selecting benzoxazine as reinforced resin, using a phosphorus-containing polysilazane derivative as a modifier and using anhydride as a curing agent; the high-heat-resistance degradable epoxy resin composite material is prepared by taking epoxy resin as a raw material and an amine accelerant as an accelerant through mixing, pouring, curing and forming. The high-heat-resistance degradable epoxy resin composite material disclosed by the invention has excellent degradation capability in an alkaline solution at the temperature of 80-150 DEG C; the heat resistance is excellent, and the glass transition temperature can reach 185 DEG C; meanwhile, the high mechanical strength is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy resin composite materials, and particularly relates to a highly heat-resistant and degradable epoxy resin composite material and a preparation method thereof. Background Art

[0002] Epoxy resin is a low-cost, high-performance and easy-to-process thermosetting material, and its composite materials are widely used in aerospace, electronics, automobile manufacturing, construction and other fields. However, after curing, epoxy resin with excellent performance is insoluble and infusible, that is, it cannot be melted or softened again, and it is also difficult to degrade or recycle.

[0003] At present, the degradation or recycling methods of epoxy resin products are mainly divided into four categories: a. Energy conversion method; b. Physical recovery method; c. High-temperature pyrolysis method; d. Chemical recovery method: Among them, the chemical recovery method is to degrade the three-dimensional network structure into low-molecular-weight compounds or monomers through chemical pathways such as cracking, hydrolysis, and alcoholysis. After purification, it can be reused with a high performance retention rate. This method is also currently a more effective degradation or recovery method.

[0004] Ester group, as a common organic functional group in the chemical degradation and recovery methods of epoxy resins, has a simplified structural formula of -COOR (R is generally an alkyl group or other non-H group) and is easily degraded under acidic or alkaline conditions. Sichuan University uses acrylic acid and amine compounds to prepare an ester-containing curing agent for epoxy resin curing (CN117946370A), which can degrade at 60-150°C, with a tensile strength of 60-70MPa and a glass transition temperature of about 50°C; Kube Chemical (Shanghai) Co., Ltd. prepares an epoxy resin containing a silazane structure, which is mixed with epoxy resin E44 or E51 to prepare a degradable epoxy resin composite material (CN116813916A), whose glass transition temperature can reach 82°C, and can gradually degrade in strong acid (pH = 1-3) at about 70°C; South-Central University for Nationalities prepares an ester-containing hyperbranched epoxy resin (CN105440261B), which can degrade at high temperature, with a tensile strength of about 120MPa and a glass transition temperature of 116°C. However, it is still difficult for epoxy resin systems containing ester groups to achieve high heat resistance and degradation at medium and low temperatures. At the same time, due to the flammability of epoxy resin, especially the higher the oxygen content in the resin structure, the more difficult it is to achieve high heat resistance and intrinsic flame retardancy. Southwest University of Science and Technology has synthesized a degradable epoxy resin containing nitrogen flame retardant elements (CN116478065A), which achieves UL-94V1 grade and a bending strength of about 70MPa. The degradation rate in an acidic environment is about 10%.

[0005] Therefore, in order to meet the needs of highly integrated equipment for high temperature resistance, medium and low temperature biodegradability and flame retardancy, the present invention has developed a highly heat-resistant biodegradable epoxy resin composite material, which has excellent heat resistance and degradation ability, as well as high mechanical strength and flame retardancy. Summary of the invention

[0006] The object of the present invention is to provide a highly heat-resistant and degradable epoxy resin composite material and a preparation method thereof to solve the above-mentioned problems.

[0007] A highly heat-resistant and degradable epoxy resin composite material is prepared by mixing, pouring, curing and molding an ester-based epoxy resin as a main resin, selecting benzoxazine as a reinforcing resin, using a phosphorus-containing polysilazane derivative as a modifier, adopting anhydride as a curing agent, and using an amine accelerator as an accelerator.

[0008] As a further improvement, the highly heat-resistant degradable epoxy resin composite material comprises the following raw materials in parts by weight:

[0009] 100 parts of ester-structured epoxy resin, 10-30 parts of benzoxazine, 10-20 parts of phosphorus-containing polysilazane derivatives, 10-100 parts of curing agent, and 0.01-0.05 parts of accelerator.

[0010] In a further improvement, the ester-based epoxy resin is one or more of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, and phthalic acid diglycidyl ester.

[0011] As a further improvement, the benzoxazine includes one or more of bisphenol A benzoxazine, bisphenol F benzoxazine, and bio-based benzoxazine.

[0012] As a further improvement, the phosphorus-containing polysilazane derivative includes one or more of DOPO-modified polysilazane (DOPO-VPSN), DPPO-modified polysilazane (DPPO-VPSN), and DCP-modified polysilazane (DCP-VPSN); wherein the polysilazane is vinyl silazane (abbreviated as: VPSN), and the phosphorus compound is one or more of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), diphenylphosphine (DPPO), and diphenyl chloride of phosphorus (DCP).

[0013] As a further improvement, the curing agent includes one or more of hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, pyromellitic anhydride, and trimellitic anhydride.

[0014] In a further improvement, the amine accelerator includes one or more of 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), benzylamines (N-benzylmethylamine, N,N-dimethylbenzylamine, o-methylbenzylamine, m-methylbenzylamine, p-methylbenzylamine, etc.), triethylamine, diethylenetriamine, and triethylenediamine.

[0015] As a further improvement, the method for preparing the highly heat-resistant degradable epoxy resin composite material comprises the following steps:

[0016] Step 1, adding benzoxazine to an ester-structured epoxy resin, stirring at 120-140° C. for 1.0 h-3.0 h to obtain an epoxy resin prepolymer containing a benzoxazine structure;

[0017] Step 2, adding the phosphorus-containing polysilazane derivative to the above epoxy resin prepolymer, stirring and pre-reacting at 80-100° C. for 1.0 h;

[0018] Step 3, adding anhydride and amine accelerator, mixing evenly, degassing and pouring into the mold;

[0019] Step 4: The mold is heated at 80-120° C. for 1-3 hours, at 150-170° C. for 1 hour, and at 180-190° C. for 3 hours to obtain the highly heat-resistant degradable epoxy resin composite material.

[0020] In the present invention, after being modified by a phosphorus-containing compound, benzoxazine modified with a phosphorus-containing compound (including but not limited to one or more of bisphenol A-type benzoxazine, bisphenol F-type benzoxazine, and bio-based benzoxazine) can be generated, wherein the phosphorus-containing compound is one or more of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), diphenylphosphine (DPPO), and pentaerythritol phosphate (PEPA).

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The highly heat-resistant degradable epoxy resin composite material of the present invention has excellent degradation ability in an alkaline solution at 80-150°C.

[0023] 2. The highly heat-resistant and degradable epoxy resin composite material of the present invention has excellent heat resistance, and the glass transition temperature can reach 185°C.

[0024] 3. The highly heat-resistant and degradable epoxy resin composite material of the present invention has high mechanical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the TMA curve diagram of Example 1;

[0026] Figure 2 It is the degradation diagram of Example 1;

[0027] Figure 3 It is the TMA curve diagram of Comparative Example 1;

[0028] Figure 4 It is the TMA curve diagram of Comparative Example 2;

[0029] Figure 5 This is the TMA curve diagram of Comparative Example 3. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0031] Example 1

[0032] Weigh 30.0 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester and 9.0 g of bisphenol A type benzoxazine, add them to the reactor in turn, heat to 130±2°C, stir and keep warm for 2.0 h, then cool to 100°C, add 6.0 g of DOPO modified polysilazane (DOPO-VPSN), and stir for 1.0 h; then cool to room temperature, add 30.0 g of methyltetrahydrophthalic anhydride to the system, stir for 15 min, and finally add 0.215 g of accelerator triethylamine, stir at room temperature for 10 min to obtain resin glue; after vacuum degassing the resin glue, transfer it to the mold, and the curing process is: 85°C / 1.0 h, 160°C / 1 h and 190°C / 3 h. After the curing is completed, a high heat-resistant and degradable epoxy resin composite material is obtained, which is numbered 1#; the performance test results are shown in Table 1, and the TMA curve is as follows Figure 1 shown.

[0033] During the degradation process, the degradation system consists of: 1.0 g epoxy curing material (high heat-resistant degradable epoxy resin composite material), 125.0 g benzyl alcohol, 1.5 g sodium hydroxide, 0.05 g aluminum acetylacetonate, and a temperature of 80 to 150°C. Figure 2 shown.

[0034] Example 2

[0035] Weigh 21.0 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 9.0 g of hexahydrophthalic acid diglycidyl ester, and 6.0 g of bisphenol F type benzoxazine, add them into the reactor in sequence, heat to 135±2°C, stir and keep warm for 1.5 h, then cool to 90°C, add 3.0 g of DOPO modified polysilazane (DOPO-VPSN), 1.5 g of DCP modified polysilazane (DCP-VPSN), and 1.5 g of bisphenol F type benzoxazine. g, stirred for 1.0h; then cooled to room temperature, added 28.7g of methyltetrahydrophthalic anhydride to the system, stirred for 15min, and finally added 0.345g of accelerator N,N-dimethylbenzylamine, stirred at room temperature for 10min to obtain resin glue; after vacuum degassing the resin glue, transferred it to the mold, the curing process was: 90℃ / 1.5h, 160℃ / 1h and 185℃ / 3h, numbered 2#; the performance test results are shown in Table 1.

[0036] Example 3

[0037] Weigh 25.0 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 5.0 g of hexahydrophthalic acid diglycidyl ester, and 4.5 g of bisphenol A type benzoxazine, add them to the reactor in sequence, heat to 138±2°C, stir and keep warm for 1.0 h, then cool to 80°C, add 3.0 g of DOPO modified polysilazane (DOPO-VPSN), and stir for 1.0 h; then cool to room temperature, add 34.5 g of hexahydrophthalic anhydride to the system, stir for 10 min, and finally add 0.345 g of accelerator N,N-dimethylbenzylamine, stir at room temperature for 15 min to obtain resin glue; after vacuum degassing the resin glue, transfer it to the mold, and the curing process is: 80°C / 2h, 150°C / 1h and 185°C / 3h, numbered 3#; its performance test results are shown in Table 1.

[0038] Example 4

[0039] Weigh 23.0 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 7.0 g of tetrahydrophthalic acid diglycidyl ester, 2.0 g of bisphenol A type benzoxazine, and 1.0 g of bisphenol F type benzoxazine, add them into the reactor in sequence, heat to 125±2°C, stir and keep warm for 2.5 h, then cool to 85°C, add 3.0 g of DPPO modified polysilazane (DPPO-VPSN) and 1.5 g of DCP modified polysilazane (DCP-VPSN), stir for 1.0 h; then cool to 85°C, add 3.0 g of DPPO modified polysilazane (DPPO-VPSN), and 1.5 g of DCP modified polysilazane (DCP-VPSN), stir for 1.0 h; then cool to 85°C, add 100 g of bisphenol A type benzoxazine, and stir for 1.0 h. To room temperature, add 25.0g of methyltetrahydrophthalic anhydride and 8.0g of trimellitic anhydride to the system, stir for 15min, finally add 0.158g of accelerator 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) and 0.116g of triethylamine, stir at room temperature for 15min to obtain resin glue; after vacuum degassing the resin glue, transfer it to a mold, and the curing process is: 90℃ / 1.0h, 170℃ / 1h and 185℃ / 3h, numbered 4#; the performance test results are shown in Table 1.

[0040] Example 5

[0041] Weigh 20.0 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 10.0 g of diglycidyl phthalate, and 5.0 g of bio-based benzoxazine, add them into the reactor in sequence, heat to 120±2°C, stir and keep warm for 3.0 h, then cool to 95°C, add 2.5 g of DOPO-modified polysilazane (DOPO-VPSN) and 0.5 g of DCP-modified polysilazane (DCP-VPSN), and stir for 1.0 h; Then the temperature was cooled to room temperature, 20.0 g of hexahydrophthalic anhydride and 10.0 g of trimellitic anhydride were added to the system, and the mixture was stirred for 15 min. Finally, 0.180 g of p-methylbenzylamine and 0.120 g of triethylamine as promoters were added, and the mixture was stirred at room temperature for 15 min to obtain resin glue. After vacuum degassing, the resin glue was transferred to a mold, and the curing process was: 100°C / 1.0h, 160°C / 1h and 180°C / 3h, numbered 5#. The performance test results are shown in Table 1.

[0042] Comparative Example 1: (without phosphorus-containing benzoxazine and polysilazane derivatives)

[0043] 30.0 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester was weighed and added to the reactor, and then 30.0 g of hexahydrophthalic anhydride was added to the system, stirred for 15 min, and finally 0.30 g of accelerator N,N-dimethylbenzylamine was added, and stirred at room temperature for 10 min to obtain resin glue; the resin glue was vacuum degassed and transferred to a mold, and the curing process was: 120°C / 1.0h, 160°C / 1h and 185°C / 3h, numbered d1#; the performance test results are shown in Table 1, and the TMA curve is shown in Figure 3 shown.

[0044] Comparative Example 2: (containing only phosphorus-containing benzoxazine, other excipients are the same)

[0045] Weigh 30.0 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester and 9.0 g of bisphenol A type benzoxazine, add them into the reactor in sequence, heat to 130±2°C, stir and keep warm for 2.0 h, then cool to room temperature, add 30.0 g of methyltetrahydrophthalic anhydride to the system, stir for 15 min, finally add 0.215 g of accelerator triethylamine, stir at room temperature for 10 min to obtain resin glue; after vacuum degassing the resin glue, transfer it to the mold, and the curing process is: 85°C / 1.0 h, 160°C / 1 h and 190°C / 3 h, numbered d2#; the performance test results are shown in Table 1, and the TMA curve is shown in Figure 4 shown.

[0046] Comparative Example 3: (containing only polysilazane derivatives, other auxiliary materials are the same)

[0047] Weigh 30.0 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, heat to 100°C, add 6.0 g of DOPO-modified polysilazane (DOPO-VPSN), and stir for 1.0 h; then cool to room temperature, add 30.0 g of methyltetrahydrophthalic anhydride to the system, stir for 15 min, and finally add 0.215 g of accelerator triethylamine, stir at room temperature for 10 min to obtain resin glue; after vacuum degassing the resin glue, transfer it to the mold, and the curing process is: 85°C / 1.0 h, 160°C / 1 h and 190°C / 3 h, numbered d3#; the performance test results are shown in Table 1, and the TMA curve is shown in Figure 5 shown.

[0048] Table 1 Performance of epoxy resin composite materials corresponding to Comparative Examples 1-3 and Examples 1-5

[0049]

[0050] From Table 1 and Figure 1 , 2 It can be seen that in Examples 1 to 5, benzoxazine is used as a reinforcing resin and a phosphorus-containing polysilazane derivative is used as a resin to improve heat resistance, so that the heat resistance Tg of the ester-based epoxy resin system is as high as 185°C, and it has excellent degradation performance at medium and low temperatures, and has high mechanical strength and flame retardancy.

[0051] Test example

[0052] Weigh 100 parts of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester (1 part is calculated as 1g) and 10 parts of bisphenol A type benzoxazine, add them to the reactor in sequence, heat to 130±2℃, stir and keep warm for 2.0h, then cool to 100℃, add DOPO modified polysilazane according to the number of parts in Table 2, stir for 1.0h; then cool to room temperature, add 100 parts of methyltetrahydrophthalic anhydride to the system, stir for 15min, finally add 7 parts of accelerator triethylamine, stir at room temperature for 10min, and obtain resin glue; after vacuum degassing the resin glue, transfer it to the mold, and the curing process is: 85℃ / 1.0h, 160℃ / 1h and 190℃ / 3h; after curing, obtain epoxy resin composite material. The test results are shown in Table 2:

[0053] Table 2 Effect of the addition amount of DOPO-modified polysilazane on the properties of epoxy resin composites

[0054]

[0055] As shown in Table 2, from the perspective of mechanical properties such as bending strength and tensile strength, as well as heat resistance (Tg), the optimal addition amount of DOPO-modified polysilazane is 20 parts (100 parts of epoxy resin).

[0056] In the present invention, phosphorus-containing benzoxazine can be prepolymerized with epoxy resin at high temperature to form a high temperature resistant structure, providing mechanical strength and heat resistance Tg of the epoxy resin system. A single addition of about 20-30 parts of phosphorus-containing benzoxazine (100 parts of epoxy resin, by mass) can achieve V1 flame retardancy, with Tg at 156-172°C. The higher the addition amount, the longer the medium and low temperature degradation time; when the addition amount exceeds 30 parts, the Tg decreases and is maintained at 165-170°C.

[0057] Polysilazane derivatives have a secondary nitrogen structure and can catalyze the curing of epoxy resins, thereby improving the heat resistance Tg and flame retardancy of epoxy resin systems. The addition of only about 10-20 parts of polysilazane derivatives (100 parts of epoxy resin, by mass) can only achieve V1 flame retardancy with Tg at 145-155°C; if the addition amount is less than 10 parts, the flame retardancy does not reach V1 and the Tg is lower than 145°C; when the addition amount is higher, the Tg decreases and the cost is higher.

[0058] Phosphorus-containing benzoxazine and polysilazane derivatives are used synergistically to construct a P / N / Si flame retardant element system. During the combustion process, benzoxazine and polysilazane construct the main carbon layer, the phosphorus-containing structure decomposes, captures combustible free radicals in the gas phase, and is further catalyzed into carbon in the solidification phase. Polysilazane forms a Si-containing dense carbon layer at high temperature, achieving intrinsic flame retardancy V0. At the same time, it can improve the temperature resistance Tg and strength.

[0059] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A highly heat-resistant and degradable epoxy resin composite material, characterized in that: The high heat-resistant and degradable epoxy resin composite material is prepared by taking an ester-based epoxy resin as the main resin, selecting benzoxazine as the reinforcing resin, using a phosphorus-containing polysilazane derivative as a modifier, adopting an acid anhydride as a curing agent, and taking an amine accelerator as an accelerator, mixing, pouring, curing and molding.

2. A highly heat-resistant and degradable epoxy resin composite material according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of ester-structured epoxy resin, 10-30 parts of benzoxazine, 10-20 parts of phosphorus-containing polysilazane derivatives, 10-100 parts of curing agent, and 0.01-0.05 parts of accelerator.

3. The highly heat-resistant and degradable epoxy resin composite material according to claim 1, characterized in that: The ester-based epoxy resin is one or more of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, and phthalic acid diglycidyl ester.

4. The highly heat-resistant and degradable epoxy resin composite material according to claim 1, characterized in that: The benzoxazine includes one or more of bisphenol A benzoxazine, bisphenol F benzoxazine, and bio-based benzoxazine.

5. The highly heat-resistant and degradable epoxy resin composite material according to claim 1, characterized in that: The phosphorus-containing polysilazane derivative includes one or more of DOPO-modified polysilazane, DPPO-modified polysilazane, and DCP-modified polysilazane.

6. The highly heat-resistant and degradable epoxy resin composite material according to claim 1, characterized in that: The curing agent includes one or more of hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, pyromellitic anhydride, and trimellitic anhydride.

7. The highly heat-resistant and degradable epoxy resin composite material according to claim 1, characterized in that: The amine accelerator includes one or more of 2,4,6-tris(dimethylaminomethyl)phenol, N-benzylmethylamine, N,N-dimethylbenzylamine, o-methylbenzylamine, m-methylbenzylamine, p-methylbenzylamine, triethylamine, diethylenetriamine, and triethylenediamine.

8. A method for preparing a highly heat-resistant and degradable epoxy resin composite material according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, adding benzoxazine to an ester-structured epoxy resin, stirring at 120-140° C. for 1.0 h-3.0 h to obtain an epoxy resin prepolymer containing a benzoxazine structure; Step 2, adding the phosphorus-containing polysilazane derivative to the above epoxy resin prepolymer, stirring and pre-reacting at 80-100° C. for 1.0 h; Step 3, adding anhydride and amine accelerator, mixing evenly, degassing and pouring into the mold; Step 4: The mold is heated at 80-120° C. for 1-3 hours, at 150-170° C. for 1 hour, and at 180-190° C. for 3 hours to obtain the highly heat-resistant degradable epoxy resin composite material.

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