Preparation method of flame-retardant transparent high-strength glass fiber reinforced epoxy resin-based composite material
By incorporating phosphoric trialkyl esters into the epoxy resin matrix, the method addresses the transparency and flame retardancy issues of GFRP, resulting in transparent and mechanically strong composites suitable for high-end applications.
Patent Information
- Application Number
- CN202510638562.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-19
- Publication Date
- 2025-07-15
AI Technical Summary
Existing glass fiber reinforced epoxy resin matrix composites (GFRPs) have shortcomings in transparency and flame retardancy, resulting in limited application in the high-end transparent material market, especially the selection or process limitations of resin matrix lead to reduced material transparency and increased light scattering.
By introducing trialkyl phosphate into the epoxy resin matrix, the flame retardant modification and refractive index regulation of the epoxy resin is achieved, combined with glass fiber reinforced epoxy resin matrix composite materials, the impregnation, lamination and gradient curing process in a vacuum environment is adopted to ensure the refractive index matching between the fiber and the resin, and improve the transparency and flame retardant performance of the material.
A glass fiber reinforced epoxy resin-based composite material with high transparency and excellent flame retardancy has achieved a vertical combustion grade of UL-94 V0, an ultimate oxygen index of more than 36%, tensile and bending strengths are maintained above 300MPa, and the material toughness is improved.
Smart Images
Figure CN120309995A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of flame retardant materials, and particularly relates to a preparation method of a flame retardant transparent high-strength glass fiber reinforced epoxy resin-based composite material. Background Art
[0002] Due to the advantages of light weight and high performance, glass fiber is widely used as a reinforcement for high-performance composite materials. Glass fiber itself has natural non-flammability and extremely low absorbance in the visible light band, and theoretically can meet the requirements of flame retardancy and transparency at the same time, which makes glass fiber have great potential in the preparation of transparent flame retardant glass fiber composite materials. Glass fiber reinforced epoxy resin-based composite material (GFRP) combines the rigidity of glass fiber and the toughness of the resin matrix, and shows irreplaceable advantages in the fields of aerospace, transportation, building materials, electronic appliances, etc. However, the existing GFRP mostly focuses on the improvement of mechanical properties, and its advantages of flame retardancy and transparency have been ignored for a long time. Therefore, how to fully exert the comprehensive performance potential of glass fiber, especially in combination with the requirements of transparency and flame retardancy, has become an important research direction in the field of materials science.
[0003] In traditional GFRP, the flame retardancy and transparency of glass fiber are usually masked due to the choice of resin matrix or process limitations. For example, most resin matrices have poor flame retardancy themselves and need to add flame retardants, but the flame retardants will significantly reduce the transparency of the material; in addition, the low refractive index matching degree and poor interfacial bonding between the resin and glass fiber will lead to increased light scattering, making the composite material appear opaque or translucent. Currently, the common GFRP on the market is mostly used in the field of structural materials, and the application of transparent flame retardant GFRP is still blank. This limitation not only wastes the transparent and flame retardant potential of glass fiber, but also restricts its competitiveness in the high-end transparent material market (such as building curtain walls, electronic display panels, high-safety transparent protective materials). Therefore, developing GFRP with both high transparency and excellent flame retardancy is the key to breaking through the existing technical bottlenecks and expanding application scenarios. Summary of the Invention
[0004] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a preparation method of a flame retardant transparent high-strength glass fiber reinforced epoxy resin-based composite material. Based on the light weight and high strength characteristics of glass fiber reinforced composite materials, the present invention synchronously realizes the flame retardant modification and refractive index regulation of epoxy resin by introducing trialkyl phosphate into the epoxy resin matrix, endows the glass fiber reinforced epoxy resin-based composite material with flame retardant performance, and makes the refractive index of epoxy resin match that of glass fiber, thereby realizing the transparent modification of the composite material.
[0005] To achieve the above object, the technical solution of the present invention is as follows:
[0006] The preparation method of the flame-retardant transparent high-strength glass fiber reinforced epoxy resin-based composite material of the present invention comprises the following steps:
[0007] Step 1: Epoxy resin, a curing agent and trialkyl phosphate are compounded in proportion. High-temperature water bath can be assisted to completely melt and uniformly mix the resin system, and then it is placed in a vacuum environment to remove the air bubbles in the resin system;
[0008] Step 2: The cut glass fiber cloth is impregnated in the resin system obtained in Step 1, taken out after being soaked through, stacked and laid flat on a smooth flat substrate pre-sprayed with a release agent. After covering a flat mold on the top layer, fixed-thickness limit blocks are inserted at the four corners of the mold to control the thickness of the composite material;
[0009] Step 3: The assembled mold is transferred to a vacuum environment for degassing treatment. After the air bubbles in the resin system are completely removed, a flat vulcanizing machine is used to perform gradient curing and molding on the sample, and finally a flame-retardant transparent high-strength glass fiber reinforced epoxy resin-based composite material is obtained.
[0010] Further, in Step 1, the epoxy resin is one of bisphenol A epoxy resin, bisphenol F epoxy resin, and polyphenol glycidyl ether epoxy resin.
[0011] Further, in Step 1, the curing agent is one of diaminodiphenylmethane, diaminodiphenylsulfone, phthalic anhydride, and methylhexahydrophthalic anhydride.
[0012] Further, in Step 1, the trialkyl phosphate is one of trimethyl phosphate, triethyl phosphate, tributyl phosphate, and trioctyl phosphate or a mixture thereof.
[0013] Further, in Step 1, the mass ratio of the epoxy resin to the curing agent is 100:20 to 100:60, and the mass of the trialkyl phosphate is 20-30 wt% of the total mass of the epoxy resin and the curing agent.
[0014] Further, in Step 2, the number of stacked layers of the glass fiber is 1-50 layers, the glass fiber content in the composite material is between 10 wt% and 80 wt%, the thickness of the composite material is between 0.1 and 5 mm, and the specific number of glass fiber layers is jointly determined by the thickness of the composite material, the glass fiber content in the composite material, and the glass fiber surface density.
[0015] Further, in Step 2, the thickness of the limit block is 0.1-5 mm.
[0016] Further, in Step 3, the conditions for gradient curing are set as follows: in the first stage, pre-curing is carried out at 60-100°C for 1-5 hours; in the second stage, final curing is carried out at 120-180°C for 1-15 hours, and the curing pressure is 1-10 MPa. The specific curing time is related to the type of curing agent used.
[0017] It should be noted that trialkyl phosphate is only physically doped as an additive in the epoxy resin system and does not participate in the curing reaction of the epoxy resin. This is because in the absence of a catalyst, the groups of triethyl phosphate cannot react with epoxy and curing agents (amine or anhydride).
[0018] Trialkyl phosphate is an additive type flame retardant. After introducing it into the epoxy resin system, the flame retardancy of the glass fiber reinforced epoxy resin based composite material can be improved through the synergistic effect of gas-phase flame retardancy and condensed-phase flame retardancy.
[0019] Trialkyl phosphate has a low refractive index, and its refractive index is between 1.35 and 1.45. After the epoxy resin is cured, due to the large number of benzene rings in the cross-linked network, its refractive index can reach about 1.60. The refractive index of glass fiber is about 1.57. Therefore, the high refractive index of the epoxy resin makes it difficult to achieve refractive index matching with the glass fiber. When visible light passes through the composite material, a large amount of light refraction and scattering occur, affecting the transparency of the composite material. After trialkyl phosphate is incorporated into the epoxy resin system, the polarization effect generated by the benzene rings in the cross-linked network is diluted, the refractive index of the epoxy resin is reduced, and it reaches close to the refractive index of the glass fiber, thereby reducing the refraction and scattering of light inside the composite material and making the composite material achieve transparent modification.
[0020] The beneficial effects of the present invention are as follows:
[0021] 1. The method of the present invention is simple and controllable. The glass fiber reinforced epoxy resin based composite material has achieved flame retardant modification. The vertical burning grade of the composite material can reach UL-94 V0, and the limiting oxygen index can reach more than 36%, improving the safety of the composite material in a fire environment;
[0022] 2. The introduction of trialkyl phosphate has greatly reduced the refractive index of the epoxy resin matrix, enabling the epoxy resin matrix to achieve refractive index matching with the glass fiber, reducing the refraction and scattering of visible light at the interface of the composite material, and making the composite material exhibit visible light transparency;
[0023] 3. The tensile and flexural strengths of the modified glass fiber reinforced epoxy resin based composite material can both be maintained above 300 MPa, and trialkyl phosphate reduces the brittleness of the epoxy resin and improves the toughness of the composite material. Description of the Drawings
[0024] Figure 1 Refractive index data of the epoxy resin matrix of the composite materials prepared in Comparative Example 2 (a), Comparative Example 3 (b), Example 1 (c), and Comparative Example 4 (d).
[0025] Figure 2 Visible light transmittance data of the composite materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d), and Comparative Example 4 (e).
[0026] Figure 3 Close-up and long-distance through photos of the composite materials prepared in Comparative Example 2 (a), Comparative Example 3 (b), Example 1 (c), and Comparative Example 4 (d).
[0027] Figure 4 Photos of the scattering patterns obtained by laser transmission of the composite materials prepared in Comparative Example 2 (a), Comparative Example 3 (b), Example 1 (c), and Comparative Example 4 (d).
[0028] Figure 5 Tensile strength and tensile modulus data of the composite materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d), and Comparative Example 4 (e).
[0029] Figure 6 Flexural strength and flexural modulus data of the composite materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d), and Comparative Example 4 (e).
[0030] Figure 7 Vertical burning grade and limiting oxygen index test results of the composite materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d), and Comparative Example 4 (e).
[0031] Figure 8 Total heat release data from the cone calorimeter test of the composite materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d), and Comparative Example 4 (e).
[0032] Figure 9 Total smoke release data from the cone calorimeter test of the composite materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d), and Comparative Example 4 (e).
[0033] Figure 10 Digital photos and SEM images of char residues from the cone calorimeter test of the composite materials prepared in Comparative Example 2 (a), Comparative Example 3 (b), Example 1 (c), and Comparative Example 4 (d).
[0034] Figure 11The Raman spectra of char residues of the composite materials prepared in Comparative Example 3 (a), Example 1 (b), and Comparative Example 4 (c) obtained by cone calorimetry test. Detailed implementation manners
[0035] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0036] Here, it should be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, while other details less related to the present invention are omitted.
[0037] In the following examples and comparative examples, unless otherwise specified for raw materials or processing techniques, it means that the commercially available raw material products or conventional processing techniques in the art are used.
[0038] Example 1:
[0039] Step 1: Weigh 50 g of bisphenol A epoxy resin of type E135 and 14 g of diaminodiphenylmethane, and place them under stirring at 95 °C until dissolved and mixed evenly. Weigh 20.21 g of triethyl phosphate and add it to the epoxy resin solution, stir evenly, and place it in a vacuum environment to remove the air bubbles in the resin system.
[0040] Step 2: Cut the glass fiber plain weave cloth into a size of 100×100 mm, place it in the epoxy resin solution. After the glass fiber cloth is soaked with the resin, take out the glass fiber cloth and remove the excess resin, and lay the impregnated fiber cloth flat on a smooth planar substrate pre-sprayed with a release agent. After stacking 6 layers of glass fiber cloth, cover the other substrate on it, and place limit blocks with a thickness of 0.5 mm at the four corners of the substrate to control the thickness of the composite material to 0.5 mm.
[0041] Step 3: Place the laid glass fiber in a vacuum environment. After the air bubbles are removed completely, place it under a pressure of 5 MPa, and carry out curing and forming according to the temperature gradient of 2 hours at 80 °C and 2 hours at 120 °C, and finally obtain a glass fiber-reinforced epoxy resin-based composite material.
[0042] Comparative Example 1:
[0043] Step 1: Weigh 50 g of bisphenol A epoxy resin of type E135 and 14 g of diaminodiphenylmethane, and place them under stirring at 95 °C until dissolved and mixed evenly, and place it in a vacuum environment to remove the air bubbles in the resin system.
[0044] Step 2: Pour the resin system onto a smooth planar substrate pre-sprayed with a release agent, cover it with the other substrate, and place limit blocks with a thickness of 0.5 mm at the four corners of the substrate to control the resin thickness at 0.5 mm.
[0045] Step 3: Place the resin under a pressure of 5 MPa and cure it according to the temperature gradient of 2 hours at 80 °C and 2 hours at 120 °C to finally obtain an epoxy resin sheet.
[0046] Comparative Example 2:
[0047] Compared with Example 1, the difference lies in that in Step 1, 50 g of E135 type bisphenol A epoxy resin and 14 g of diaminodiphenylmethane are weighed, placed at 95 °C and stirred until dissolved and mixed evenly, and placed in a vacuum environment to remove the bubbles in the resin system.
[0048] Comparative Example 3:
[0049] Compared with Example 1, the difference lies in that in Step 1, 50 g of E135 type bisphenol A epoxy resin and 14 g of diaminodiphenylmethane are weighed, placed at 95 °C and stirred until dissolved and mixed evenly, 18.05 g of triethyl phosphate is weighed and added to the epoxy resin solution, stirred evenly, and placed in a vacuum environment to remove the bubbles in the resin system.
[0050] Comparative Example 4:
[0051] Compared with Example 1, the difference lies in that in Step 1, 50 g of E135 type bisphenol A epoxy resin and 14 g of diaminodiphenylmethane are weighed, placed at 95 °C and stirred until dissolved and mixed evenly, 22.49 g of triethyl phosphate is weighed and added to the epoxy resin solution, stirred evenly, and placed in a vacuum environment to remove the bubbles in the resin system.
[0052] As Figure 1 shown, Figure 1 shows the refractive index results of the epoxy resin matrix of the composites prepared in Comparative Example 2 (a), Comparative Example 3 (b), Example 1 (c), and Comparative Example 4 (d). It can be seen that with the increase in the addition ratio of triethyl phosphate, the refractive index of the epoxy resin has been significantly reduced.
[0053] As Figure 2 shown, Figure 2 shows the visible light transmittance data of the composites prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d), and Comparative Example 4 (e). It can be seen that compared with pure epoxy resin, the transmittance of the composite material after being reinforced with glass fiber has decreased, and with the increase in the addition amount of triethyl phosphate, the resin refractive index also decreases, but the change range is small.
[0054] As Figure 3 shown, Figure 3 the close - up and long - distance through - photos of the composite materials prepared in Comparative Example 2 (a), Comparative Example 3 (b), Example 1 (c) and Comparative Example 4 (d) are shown. It can be seen that the refractive index of the epoxy resin prepared with the formulation in Example 1 is closest to that of the glass fiber. Therefore, clear through - images can be obtained for the sample of Example 1 in both the close - up and long - distance views. For other samples, due to the mismatch of the fiber - resin refractive index, clear images at a long distance cannot be observed.
[0055] As Figure 4 shown, Figure 3 the photos of the scattering patterns obtained by laser transmission of the composite materials prepared in Comparative Example 2 (a), Comparative Example 3 (b), Example 1 (c) and Comparative Example 4 (d) are shown. By comparing the morphology of the transmitted light spots, it can be seen that the composite material prepared in Example 1 has the smallest scattering halo and the sharpest cross - contour edge, proving that the scattering degree of this sample to light is the lowest, making Figure 3 the results further verified.
[0056] As Figure 5 and Figure 6 shown, Figure 5 and Figure 6 respectively show the tensile strength and tensile modulus, as well as the flexural strength and flexural modulus data of the composite materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d) and Comparative Example 4 (e). It can be seen that, compared with pure epoxy resin, the tensile and flexural properties of the composite materials reinforced with glass fiber have been greatly improved, proving that high - strength composite materials have been successfully prepared.
[0057] As Figure 7 shown, Figure 7 the vertical burning grade and limiting oxygen index test results of the composite materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d) and Comparative Example 4 (e) are shown. It can be seen that when the addition amount of triethyl phosphate reaches the proportion in Example 1, the vertical burning grade of the composite material can reach UL - 94 V0, and the limiting oxygen index proves that the composite material can reach the flame - retardant grade.
[0058] As Figure 8 and Figure 9 shown, Figure 8 and Figure 9The total heat release and total smoke release data of the composites prepared from Comparative Example 1 (a), Comparative Example 2 (b), Comparative Example 3 (c), Example 1 (d) and Comparative Example 4 (e) in the cone calorimetry test are shown. The results indicate that both the heat release and smoke release of the glass fiber-reinforced composite during combustion are much lower than those of pure epoxy resin, and with the increase in the addition amount of triethyl phosphate, both the heat release and smoke release are further reduced.
[0059] As Figure 10 shown, Figure 10 the digital photos of the char residues and SEM images of the composites prepared from Comparative Example 2 (a), Comparative Example 3 (b), Example 1 (c) and Comparative Example 4 (d) in the cone calorimetry test are shown. It can be seen that after adding triethyl phosphate, the amount of char residues remaining on the surface of the glass fiber increases, which proves that triethyl phosphate can promote the carbonization of epoxy resin.
[0060] As Figure 11 shown, Figure 11 the Raman spectra of the char residues of the composites prepared from Comparative Example 3 (a), Example 1 (b) and Comparative Example 4 (c) in the cone calorimetry test are shown. It can be seen that the addition amount of triethyl phosphate in Example 1 has the best promoting effect on the carbonization of epoxy resin, which is also the reason for the lowest smoke release amount in Example 1.
[0061] In summary, for the composite material prepared in the manner of Example 1, the addition amount of triethyl phosphate is optimal. The presence of triethyl phosphate not only enables the composite material to achieve flame retardancy and fire resistance, but also makes the refractive indices of the fiber and resin achieve the best match, and a flame-retardant, transparent, high-strength glass fiber-reinforced epoxy resin-based composite material is successfully prepared.
Claims
1. A preparation method of a flame-retardant transparent high-strength glass fiber reinforced epoxy resin-based composite material, characterized in that It includes the following steps: Step 1: Mix epoxy resin, curing agent and trialkyl phosphate in proportion and mix them evenly. Then place them in a vacuum environment to remove the air bubbles in the resin system; Step 2: Immerse the cut glass fiber cloth in the resin system obtained in Step 1. After soaking, take it out and lay it flat in layers on a smooth flat substrate pre-sprayed with a mold release agent, and cover the top layer with a flat mold; Step 3: Transfer the assembled mold to a vacuum environment for degassing treatment, and then use a flat vulcanizing machine to carry out gradient curing and molding on the sample to finally obtain a flame-retardant transparent high-strength glass fiber-reinforced epoxy resin-based composite material.
2. The preparation method according to claim 1, wherein: In Step 1, the epoxy resin is one of bisphenol A epoxy resin, bisphenol F epoxy resin, and polyphenol glycidyl ether epoxy resin.
3. The preparation method according to claim 1, wherein: In Step 1, the curing agent is one of diaminodiphenylmethane, diaminodiphenylsulfone, phthalic anhydride, and methylhexahydrophthalic anhydride.
4. The preparation method according to claim 1, wherein: In Step 1, the trialkyl phosphate is one of trimethyl phosphate, triethyl phosphate, tributyl phosphate, and trioctyl phosphate or a mixture thereof.
5. The preparation method according to claim 4, wherein: In Step 1, the mass of the trialkyl phosphate is 20-30 wt% of the total mass of the epoxy resin and the curing agent.
6. The preparation method according to claim 1, wherein: In Step 2, the number of stacked layers of the glass fiber is 1-50 layers.
7. The preparation method according to claim 1, wherein: In Step 3, the conditions of the gradient curing are set as follows: pre-curing at 60-100 °C in the first stage and final curing at 120-180 °C in the second stage, and the curing pressure is 1-10 MPa.
8. A flame-retardant transparent high-strength glass fiber-reinforced epoxy resin-based composite material prepared by the preparation method according to any one of claims 1-7.
9. The flame-retardant transparent high-strength glass fiber-reinforced epoxy resin-based composite material according to claim 8, wherein: The thickness of the flame-retardant transparent high-strength glass fiber-reinforced epoxy resin-based composite material is 0.1-5 mm.
10. The flame-retardant transparent high-strength glass fiber-reinforced epoxy resin-based composite material according to claim 9, characterized in that: The content of glass fiber in the flame-retardant transparent high-strength glass fiber-reinforced epoxy resin-based composite material is 10 wt% - 80 wt%.