Thermosetting carbon fiber composite material recovery method based on molecular binding energy

Abstract

The invention discloses a thermosetting carbon fiber composite material recovery method based on molecular binding energy, which comprises the following steps: carrying out effective binding energy analysis on thermosetting resin and reagents on the surface of a thermosetting carbon fiber composite material to be recovered through a quantum chemical calculation method; selecting a reagent of which the effective binding energy with the thermosetting resin is less than-15 kcal / mol as a swelling reagent; carrying out swelling treatment on the to-be-recycled thermosetting carbon fiber composite material by adopting a swelling reagent; and immersing the swelled material into a solution containing an oxidizing solvent for degradation to obtain the recycled carbon fiber. According to the method, a synergistic process of swelling pretreatment and peroxy acid degradation is innovatively adopted, efficient degradation of the thermosetting resin is realized under low-temperature and normal-pressure conditions, high-temperature damage caused by a pyrolysis method is avoided, the defect of fiber breakage caused by a mechanical method is overcome, and the original performance of the carbon fiber is well maintained.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber recycling technology, and specifically to a method for recycling thermosetting carbon fiber composite materials based on molecular binding energy. Background Technology

[0002] Carbon fiber reinforced polymer (CFRP) composites, with their excellent specific strength, high stiffness, and corrosion resistance, have become core materials in aerospace, new energy equipment, and high-end sporting goods. However, their widespread use has also brought about an increasingly serious problem of waste disposal. According to industry statistics, the total amount of CFRP waste worldwide continues to rise.

[0003] A large portion of these waste materials originate from carbon fiber composites based on thermosetting resins. While their stable three-dimensional cross-linked structure endows the materials with excellent properties, it also makes them difficult to degrade and recycle. Currently, the mainstream CFRP recycling methods include mechanical recycling, pyrolysis recycling, and chemical recycling, but these methods generally suffer from problems such as high energy consumption, significant carbon fiber damage, and low recycling efficiency.

[0004] It is worth noting that carbon fiber manufacturing is an energy-intensive process, requiring approximately 200-600 MJ of energy to produce each kilogram of virgin carbon fiber, and is accompanied by significant carbon emissions. Therefore, developing efficient and low-damage thermosetting carbon fiber recycling technologies is an effective way to address the aforementioned challenges.

[0005] Patent CN117567839A discloses a biodegradable epoxy resin composition, prepreg, and composite material thereof. By introducing an epoxy resin containing imine bonds and a curing agent containing imine bonds to construct a biodegradable crosslinking network, the composite material achieves controlled degradation under mild acidic conditions while maintaining its mechanical and thermal properties. However, the amount of biodegradable component added in this technical solution needs to be controlled within the range of 20-50 parts. Too low an addition amount may lead to insufficient degradation efficiency, while too high an addition amount will affect the mechanical strength of the material.

[0006] Patent CN120775253A discloses a method for recycling carbon fibers in carbon fiber composites. This method achieves efficient carbon fiber recycling through a combination of swelling pretreatment, electrochemical degradation, and plasma treatment. The method effectively decomposes the resin matrix using electrochemical degradation, followed by plasma treatment to remove residues, resulting in recycled carbon fibers with no significant surface defects and maintaining good mechanical properties. However, this technical solution involves a multi-stage process combination, requiring complex equipment and high energy consumption. In particular, the plasma treatment stage requires precise control of processing parameters to avoid damage to the carbon fibers. Furthermore, the selection of the electrolyte and subsequent treatment may introduce new environmental burdens, and the process cost and scalability still require further verification. Summary of the Invention

[0007] This invention addresses the problems of significant carbon fiber damage and insufficient degradation rate in the recycling of carbon fiber composites. It provides a thermosetting carbon fiber composite recycling method based on molecular binding energy. By combining theoretical simulation with experimental verification, this method has the advantages of precise screening, mild conditions, high recycling efficiency, and minimal fiber damage, providing a new approach for the high-value recycling of carbon fiber composites.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for recycling thermosetting carbon fiber composites based on molecular binding energy includes the following steps: Step 1: Analyze the effective binding energy of the thermosetting resin and reagents on the surface of the thermosetting carbon fiber composite material to be recycled, and select reagents with an effective binding energy of <-15 kcal / mol with the thermosetting resin as swelling reagents. Step 2: Use a swelling agent to treat the thermosetting carbon fiber composite material to be recycled to swell. Step 3: Immerse the swollen material from Step 2 in a solution containing an oxidizing solvent for degradation to obtain recycled carbon fiber.

[0009] This invention utilizes software simulation to analyze the surface electrostatic potential and binding energy of thermosetting resins with various swelling agents, optimizing the selection of highly efficient swelling agents. Subsequently, a swelling treatment is applied to the thermosetting carbon fiber composite material. Combined with degradation treatment using oxidizing solvents, a degradation rate of over 95% of the thermosetting resin on the carbon fiber surface can be achieved. This method, guided by theoretical prediction, significantly improves the efficiency and specificity of carbon fiber recycling, providing a reliable pathway for the recycling and reuse of thermosetting composite materials.

[0010] In step 3, the oxygen content of the oxidizing solvent is 5-15%. Within this range, the thermosetting resin can achieve a high efficiency of over 95% degradation, avoiding incomplete resin degradation or excessively rapid reaction that could lead to hindered mass transfer or aggravated side reactions, which would be detrimental to the deep degradation of the resin.

[0011] In step 1, the effective binding energy between the swelling reagent and the thermosetting resin is < -15.0 kcal / mol. A smaller binding energy indicates a stronger interaction between the swelling reagent and resin molecules, which is more conducive to the reagent penetrating into the resin cross-linking network. When the binding energy is < -15.0 kcal / mol, the reagent has sufficient affinity to achieve effective swelling of the resin; if the binding energy is ≥ -15.0 kcal / mol, the interaction is weak, making it difficult to fully expand the resin network, resulting in insufficient swelling.

[0012] The swelling rate of the material in step 2 is 30.0%~80.0%. The swelling rate is negatively correlated with the binding energy in step 1: the smaller the binding energy, the stronger the interaction between the reagent and the resin, which is more conducive to obtaining a higher swelling rate. When the binding energy is <-15.0 kcal / mol, the reagent has sufficient affinity to achieve effective swelling of the resin, resulting in a swelling rate of 30.0%~80.0%.

[0013] Based on the correlation between binding energy and swelling ratio, the binding energy analysis in step 1 can be used to quickly screen for highly efficient swelling reagents, reducing experimental workload. If the binding energy meets the standard but the swelling ratio is too low, it indicates that the swelling process conditions are insufficient, and parameters such as temperature and time need to be optimized. Therefore, meeting the binding energy standard is the foundation for effective swelling, and meeting the swelling ratio standard is a prerequisite for efficient degradation.

[0014] The swelling agent includes any one or more of the following: sulfolane, dimethoxymethane, acetic acid, N,N-dimethylacetamide, γ-butyrolactone, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and dichloromethane; The thermosetting resin includes any one or more blends of epoxy resin, bismaleimide resin, phenolic resin, and cyanate ester resin.

[0015] In step 1, the effective binding energy of thermosetting resin and reagent is simulated and analyzed using quantum chemical calculation methods.

[0016] In step 2, the swelling treatment temperature is 20-40℃ and the time is 12-36h.

[0017] The degradation temperature in step 3 is 40-80℃, and the reaction time is 4-8h.

[0018] The solution containing the oxidizing solvent includes a mixture of peroxide and concentrated sulfuric acid, wherein the volume of concentrated sulfuric acid is 3%-5% of the volume of peroxide.

[0019] The peroxides include any one or more of peracetic acid, peroxybenzoic acid, m-chloroperoxybenzoic acid, and peroxynitric acid.

[0020] The degradation rate of thermosetting resin in the recycled carbon fiber obtained in step 3 is over 95%.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention proposes for the first time to use software molecular simulation technology to establish a swelling reagent screening system based on binding energy, which fundamentally changes the blindness of the traditional trial and error method, realizes the transformation from "experience screening" to "theoretical prediction", and significantly improves the R&D efficiency.

[0022] (2) The present invention innovatively adopts a synergistic process of “swelling pretreatment + peroxy acid degradation” to achieve efficient degradation of thermosetting resin under low temperature and normal pressure conditions. This avoids the high temperature damage of pyrolysis and overcomes the fiber breakage defects of mechanical method, thus maintaining the original properties of carbon fiber. Attached Figure Description

[0023] Figure 1 This is a simulation diagram of molecular swelling calculated using quantum chemistry in Comparative Example 1.

[0024] Figure 2 Scanning electron microscope image of the recycled carbon fiber prepared for Comparative Example 1.

[0025] Figure 3 This is a simulation diagram of molecular swelling calculated using quantum chemistry in Comparative Example 2.

[0026] Figure 4 Scanning electron microscope image of the recycled carbon fiber prepared for Comparative Example 2.

[0027] Figure 5 The figures are simulations of molecular swelling calculated using quantum chemistry in Comparative Examples 3-5 and Examples 3-5.

[0028] Figure 6 Scanning electron microscope image of the recycled carbon fiber prepared for Comparative Example 3.

[0029] Figure 7 Scanning electron microscope image of the recycled carbon fiber prepared for Comparative Example 4.

[0030] Figure 8 Scanning electron microscope image of the recycled carbon fiber prepared for Comparative Example 5.

[0031] Figure 9 This is a simulation diagram of molecular swelling calculated using quantum chemistry in Example 1.

[0032] Figure 10 This is a scanning electron microscope image of the recycled carbon fiber prepared in Example 1.

[0033] Figure 11 This is a simulation diagram of molecular swelling calculated using quantum chemistry in Example 2.

[0034] Figure 12 This is a scanning electron microscope image of the recycled carbon fiber prepared in Example 2.

[0035] Figure 13 This is a scanning electron microscope image of the recycled carbon fiber prepared in Example 3.

[0036] Figure 14 This is a scanning electron microscope image of the recycled carbon fiber prepared in Example 4.

[0037] Figure 15This is a scanning electron microscope image of the recycled carbon fiber prepared in Example 5. Detailed Implementation

[0038] 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. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0039] All raw materials used in the following specific implementation methods were purchased from the market.

[0040] Comparative Example 1 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and acetone reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -6.32 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 1 As shown.

[0041] Step 2, swelling experiment: The carbon fiber composite material was immersed in 50 ml of acetone reagent for a swelling experiment. The swelling temperature was 25℃ and the time was 24 h. The molecular swelling rate was 13.36%.

[0042] Step 3, Peroxyacid Degradation Experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded by adding 4 ml of concentrated sulfuric acid to 100 ml of peracetic acid (oxygen ratio 10.6%), at a temperature of 60℃ for 6 hours. After the reaction, recycled carbon fiber was obtained, and the epoxy resin degradation rate was 82.53%. Its scanning electron microscopy results are shown below. Figure 2 As shown, there is clearly residual resin, indicating incomplete degradation.

[0043] Comparative Example 2 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and ethanol reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -9.80 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 3 As shown.

[0044] Step 2, swelling experiment: The carbon fiber composite material was added to 50 ml of ethanol reagent for a swelling experiment. The swelling temperature was 25℃ and the time was 24 h. The molecular swelling rate was 18.23%.

[0045] Step 3, Peroxyacid Degradation Experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of peracetic acid (oxygen content 10.6%), at 60℃ for 6 hours, with 4 ml of concentrated sulfuric acid. After the reaction, recycled carbon fiber was obtained. The epoxy resin degradation rate was 83.78%, as shown in the scanning electron microscope image. Figure 4 As shown, there is clearly residual resin, indicating incomplete degradation.

[0046] Comparative Example 3 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and dimethyl sulfoxide reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -20.20 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 5 As shown.

[0047] Step 2, swelling experiment: The carbon fiber composite material was added to 50 ml of dimethyl sulfoxide reagent for a swelling experiment. The swelling temperature was 25℃ and the time was 24 h, and the molecular swelling rate was 40.87%.

[0048] Step 3, Oxygen-free acid degradation experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of hydrochloric acid (2 mol / L, 0% oxygen content), at 60℃ for 6 hours, and 4 ml of concentrated sulfuric acid. After the reaction, recycled carbon fiber was obtained. The epoxy resin degradation rate was 36.35%, as shown in the scanning electron microscope image. Figure 6 As shown, there is clearly residual resin, indicating incomplete degradation.

[0049] Comparative Example 4 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and dimethyl sulfoxide reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -20.20 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 5 As shown.

[0050] Step 2, swelling experiment: The carbon fiber composite material was added to 50 ml of dimethyl sulfoxide reagent for a swelling experiment. The swelling temperature was 25℃ and the time was 24 h, and the molecular swelling rate was 40.87%.

[0051] Step 3, Oxygen-free acid degradation experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of acetic acid (0% oxygen content), at 60°C for 6 hours, and 4 ml of concentrated sulfuric acid. The recovered carbon fiber was obtained after the reaction. The epoxy resin degradation rate was 23.12%, as shown in the scanning electron microscope image. Figure 7 As shown, there is clearly residual resin, indicating incomplete degradation.

[0052] Comparative Example 5 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and dimethyl sulfoxide reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -20.20 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 5 As shown.

[0053] Step 2, swelling experiment: The carbon fiber composite material was added to 50 ml of dimethyl sulfoxide reagent for a swelling experiment. The swelling temperature was 25℃ and the time was 24 h, and the molecular swelling rate was 40.87%.

[0054] Step 3, Peroxyacid Degradation Experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of peracetic acid (oxygen content 19.6%), at 60℃ for 6 hours, with 4 ml of concentrated sulfuric acid. The recovered carbon fiber was obtained after the reaction. The epoxy resin degradation rate was 92.78%, as shown in the scanning electron microscope image. Figure 8 As shown, due to the slightly higher oxygen content in the solution during degradation, residual resin is clearly visible, indicating incomplete degradation.

[0055] Example 1 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and dimethylacetamide reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -17.10 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 9 As shown.

[0056] Step 2, swelling experiment: 50 ml of dimethylacetamide reagent was added to the carbon fiber composite material for a swelling experiment. The swelling temperature was room temperature and the time was 24 h. The molecular swelling rate was 38.62%.

[0057] Step 3, Peroxyacid Degradation Experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of peracetic acid (oxygen content 10.6%), at 60℃ for 6 hours, with 4 ml of concentrated sulfuric acid. The recovered carbon fiber was obtained after the reaction. The epoxy resin degradation rate was 97.23%, as shown in the scanning electron microscope image. Figure 10 As shown, no residual resin was found, and the resin was effectively removed.

[0058] Example 2 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and tetrahydrofuran reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -27.05 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 11 As shown.

[0059] Step 2, swelling experiment: 50 ml of tetrahydrofuran reagent was added to the carbon fiber composite material for a swelling experiment. The swelling temperature was room temperature and the time was 24 h. The molecular swelling rate was 58.06%.

[0060] Step 3, Peroxyacid Degradation Experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of peracetic acid (oxygen content 10.6%), at 60℃ for 6 hours, with 4 ml of concentrated sulfuric acid. The recovered carbon fiber was obtained after the reaction. The epoxy resin degradation rate was 98.52%, as shown in the scanning electron microscope image. Figure 12 As shown, no residual resin was found, and the resin was effectively removed.

[0061] Example 3 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and dimethyl sulfoxide reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -20.20 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 5 As shown.

[0062] Step 2, swelling experiment: The carbon fiber composite material was added to 50 ml of dimethyl sulfoxide reagent for a swelling experiment. The swelling temperature was room temperature and the time was 24 h. The molecular swelling rate was 40.87%.

[0063] Step 3, Peroxyacid Degradation Experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of peracetic acid (oxygen content 7.1%), at 60℃ for 6 hours, with 4 ml of concentrated sulfuric acid. The recovered carbon fiber was obtained after the reaction. The epoxy resin degradation rate was 96.10%, as shown in the scanning electron microscope image. Figure 13 As shown, no residual resin was found, and the resin was effectively removed.

[0064] Example 4 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and dimethyl sulfoxide reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -20.20 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 5 As shown.

[0065] Step 2, swelling experiment: The carbon fiber composite material was added to 50 ml of dimethyl sulfoxide reagent for a swelling experiment. The swelling temperature was room temperature and the time was 24 h. The molecular swelling rate was 40.87%.

[0066] Step 3, Peroxyacid Degradation Experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of peracetic acid (oxygen content 10.6%), at 60℃ for 6 hours, with 4 ml of concentrated sulfuric acid. After the reaction, recycled carbon fiber was obtained. The epoxy resin degradation rate was 96.40%, as shown in the scanning electron microscope image. Figure 14 As shown, no residual resin was found, and the resin was effectively removed.

[0067] Example 5 Step 1, Calculation of binding energy between swelling reagent and resin: The binding energy between epoxy resin and dimethyl sulfoxide reagent was simulated using quantum chemical calculation methods, yielding a binding energy of -20.20 kcal / mol. The molecular swelling simulation diagram is shown below. Figure 5 As shown.

[0068] Step 2, swelling experiment: The carbon fiber composite material was added to 50 ml of dimethyl sulfoxide reagent for a swelling experiment. The swelling temperature was room temperature and the time was 24 h. The molecular swelling rate was 40.87%.

[0069] Step 3, Peroxyacid Degradation Experiment: The swollen carbon fiber composite material obtained in Step 2 was degraded using 100 ml of peracetic acid (oxygen content 14.0%), at 60℃ for 6 hours, with 4 ml of concentrated sulfuric acid. After the reaction, recycled carbon fiber was obtained. The epoxy resin degradation rate was 95.30%, as shown in the scanning electron microscope image. Figure 15 As shown, no residual resin was found, and the resin was effectively removed.

[0070] In summary, the technical solution of this invention establishes a clear quantitative standard: when the binding energy between the swelling agent and the thermosetting resin is less than -15 kcal / mol, the swelling rate is greater than 30%, and the oxygen content in the peroxyacid is 5-15%, the system can achieve a thermosetting resin degradation rate of over 95%. The establishment of this standard system enables full-process quantitative control from theoretical prediction to process parameters, providing a reliable basis for the efficient recycling of carbon fiber composite materials.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for recycling thermosetting carbon fiber composite materials based on molecular binding energy, characterized in that, Including the following steps: Step 1: Analyze the effective binding energy of the thermosetting resin and reagents on the surface of the thermosetting carbon fiber composite material to be recycled, and select reagents with an effective binding energy of <-15 kcal / mol with the thermosetting resin as swelling reagents. Step 2: Use a swelling agent to treat the thermosetting carbon fiber composite material to be recycled to swell. Step 3: Immerse the swollen material from Step 2 in a solution containing an oxidizing solvent for degradation to obtain recycled carbon fiber.

2. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, In step 3, the oxygen content of the oxidizing solvent is 5-15%.

3. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, The swelling rate of the material in step 2 is 30.0% to 80.0%.

4. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, The swelling agent includes any one or more of the following: sulfolane, dimethoxymethane, acetic acid, N,N-dimethylacetamide, γ-butyrolactone, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and dichloromethane; The thermosetting resin includes any one or more blends of epoxy resin, bismaleimide resin, phenolic resin, and cyanate ester resin.

5. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, In step 1, the effective binding energy of thermosetting resin and reagent is simulated and analyzed using quantum chemical calculation methods.

6. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, In step 2, the swelling treatment temperature is 20-40℃ and the time is 12-36h.

7. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, The degradation temperature in step 3 is 40-80℃, and the reaction time is 4-8h.

8. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, The solution containing the oxidizing solvent includes a mixture of peroxide and concentrated sulfuric acid, wherein the volume of concentrated sulfuric acid is 3%-5% of the volume of peroxide.

9. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, The peroxides include any one or more of peracetic acid, peroxybenzoic acid, m-chloroperoxybenzoic acid, and peroxynitric acid.

10. The method for recycling thermosetting carbon fiber composite materials based on molecular binding energy according to claim 1, characterized in that, The degradation rate of thermosetting resin in the recycled carbon fiber obtained in step 3 is over 95%.

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