A force-induced color-changing epoxy resin composite material, a preparation method and application thereof

Abstract

The present application relates to a kind of force-induced color change epoxy resin composite and its preparation method and application, belong to resin-based composite material technical field.The method: after rhodamine is mixed with ethylenediamine with anhydrous ethanol, reflux is carried out, then filter, wash and dry;After the modified rhodamine obtained is mixed with epoxy resin, it is treated 2-4h at 130-180 ℃;Rhodamine modified epoxy resin obtained, curing agent and accelerator are mixed, then nano-aluminum oxide is added and mixed, then it is stirred and treated at 60-100 ℃, to obtain the pre-crosslinking material with the viscosity of 40000-80000cps;Pre-crosslinking material is first cured under vacuum condition at 70-90 ℃ for 3-6h, then it is cured at 120-140 ℃ for 10-15h, to prepare force-induced color change epoxy resin composite.The present application can significantly improve the stress color effect of material and strengthen fluorescent opening response, and can effectively prevent alumina from settling.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of resin-based composite materials, and particularly relates to a force-induced color-changing epoxy resin composite material and a preparation method and application thereof. BACKGROUND

[0002] With the gradual improvement of the performance of resin-based composite materials, meeting certain mechanical properties is a prerequisite for its use as a structural material, and toughening is an important means to realize the engineering and high performance of resin-based materials. However, fatigue and damage of resin-based composite materials during storage and use are inevitable, and it is one of the main failure forms of engineering structures. Moreover, in many cases, the significant loss and harm caused by small size defects cannot be underestimated. At present, the surface and subsurface damage of materials is more often detected by ultrasonic detection. This method is not only difficult to operate, but also limited by damage depth and material surface type. Therefore, a more rapid and obvious flaw detection mechanism and detection of the deformation and destruction rules of high molecules at the molecular level are important ways to improve the quality of resin-based composite materials and the needs of production and practical application.

[0003] Elastomeric materials are not very useful in practical engineering applications due to their strength, stiffness, and heat resistance. Rhodamine is considered for damage detection in epoxy resin materials due to its color-changing force-sensitive group. However, conventional epoxy resin materials containing rhodamine are often not sensitive to mechanical forces and do not have obvious coloration after being stressed, which limits their use in applications requiring high precision and high force sensitivity.

[0004] In summary, it is necessary to provide a new force-induced color-changing epoxy resin composite material and a preparation method and application thereof. SUMMARY

[0005] In order to solve one or more technical problems existing in the prior art, the present application provides a force-induced color-changing epoxy resin composite material and a preparation method and application thereof.

[0006] In a first aspect, the present application provides a preparation method of a force-induced color-changing epoxy resin composite material, which comprises the following steps:

[0007] (1) Rhodamine 6G and ethylenediamine are mixed uniformly with anhydrous ethanol and then subjected to a reflux reaction, followed by filtration, washing, and drying to obtain a modified rhodamine;

[0008] (2) The modified rhodamine is mixed uniformly with an epoxy resin and then treated at 130-180℃ for 2-4h to obtain a rhodamine-modified epoxy resin;

[0009] (3) mixing the rhodamine modified epoxy resin, the curing agent and the accelerator uniformly to obtain a first mixture, then adding the nano-alumina into the first mixture and mixing uniformly to obtain a second mixture, and then stirring and treating the second mixture at 60-100 DEG C to obtain a pre-crosslinking material with a viscosity of 40000-80000 cps;

[0010] (4) curing the pre-crosslinking material at 70-90 DEG C under vacuum for 3-6 h, and then curing at 120-140 DEG C for 10-15 h to obtain the force-induced color-changing epoxy resin composite material.

[0011] Preferably, the molar ratio of the rhodamine 6G to the ethylenediamine is 1:(3.5-4.5); the mass ratio of the anhydrous ethanol to the rhodamine 6G is (10-15):1; and / or the temperature of the reflux reaction is 70-90 DEG C, and the time of the reflux reaction is 18-30 h.

[0012] Preferably, the epoxy resin is a bisphenol A type epoxy resin; and / or the mass ratio of the modified rhodamine to the epoxy resin is 1:(15-25).

[0013] Preferably, the curing agent is an acid anhydride type curing agent and / or an amine type curing agent; and / or the accelerator is DMP-30.

[0014] Preferably, the mass ratio of the rhodamine modified epoxy resin, the curing agent and the accelerator is 100:(20-40):(1-5).

[0015] Preferably, the mass ratio of the first mixture to the nano-alumina is 100:(20-70).

[0016] Preferably, the stirring speed of the stirring treatment is 100-400 r / min.

[0017] Preferably, the stirring treatment is carried out under air atmosphere; and / or the curing at 120-140 DEG C is carried out under air atmosphere.

[0018] The present application provides in a second aspect a force-induced color-changing epoxy resin composite material prepared by the preparation method described in the first aspect of the present application.

[0019] The present application provides in a third aspect an application of the force-induced color-changing epoxy resin composite material prepared by the preparation method described in the first aspect of the present application in damage detection.

[0020] Compared with the prior art, the present application has at least the following beneficial effects:

[0021] (1) The force-induced color-changing epoxy resin composite prepared by the present application is a rhodamine force-induced color-changing force-sensitive group modified epoxy resin combined with nano-aluminum oxide, which is a mechanical force response composite with more obvious color development and fluorescence response, and is applied to structural stress detection in engineering and detection of small damage or cracks after stress and fatigue damage; the present application successfully prepares a structural damage detection epoxy resin composite which can significantly improve the stress color development effect and strengthen the fluorescence opening response without sacrificing the mechanical properties by combining rhodamine force-sensitive group modification with the addition of nano-aluminum oxide; the epoxy resin composite in the present application not only improves the stress color development effect of rhodamine modified epoxy resin, but also maintains excellent mechanical properties, making it an ideal resin-based damage detection material, especially suitable for use in high-precision and high-force-sensitive engineering; the epoxy resin composite in the present application can significantly improve the apparent characteristics of resin-based materials when they are damaged and cracked, and this technology can mainly be applied to detect the stress of materials and predict potential damage, and has a wide application prospect in the fields of aerospace, automobile manufacturing, electronic products and the like.

[0022] (2) The force-induced color-changing epoxy resin composite prepared by the present application is a rhodamine modified epoxy resin and nano-aluminum oxide, and the present application finds that the two are not independent, the rhodamine modified epoxy resin can improve the dispersion uniformity of nano-aluminum oxide compared with conventional epoxy resin, and can effectively prevent the sedimentation of nano-aluminum oxide; the addition of nano-aluminum oxide can effectively improve the stress color development effect of the rhodamine modified epoxy resin, which is first discovered by the present application; although the existing technology fills aluminum oxide into the epoxy resin to improve the thermal conductivity, dielectric constant and weather resistance of the epoxy resin, but it has never been reported that nano-aluminum oxide can promote the stress color change and fluorescence opening response of the rhodamine modified epoxy resin.

[0023] (3) To further address the problem of significant sedimentation of nano-alumina particles in epoxy resin materials, this invention, in the process of preparing mechanochromic epoxy resin composites using nano-alumina as a filler to fill rhodamine-modified epoxy resin, optimizes the curing process of epoxy resin by stirring the second mixture to obtain a pre-crosslinked material with a viscosity controlled at 40,000–80,000 cps. This invention finds that by controlling the viscosity of the pre-crosslinked material at 40,000–80,000 cps during molding, the viscous resistance to particle sedimentation is effectively increased. Without altering the composition of the epoxy resin composite material, this stirring pre-crosslinking operation significantly enhances the curing properties. The interfacial bonding between rhodamine-modified epoxy resin and nano-alumina significantly improves the dispersibility and uniformity of nano-alumina in rhodamine-modified epoxy resin, effectively solving the problem of nano-alumina filler sedimentation. This invention discovers that obtaining a pre-crosslinked material with a viscosity of 40,000–80,000 cps through stirring followed by curing is an effective way to prevent sedimentation. This can be used to prepare epoxy resin composites with lower sedimentation rates and more uniform material properties, thereby improving the mechanochromic properties and mechanical properties of epoxy resin composites, effectively ensuring the uniformity of epoxy resin composite performance, while also maintaining a high insulation coefficient and good thermal conductivity. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the preparation process of some specific embodiments of the present invention;

[0025] Figure 2 This is a fluorescence spectrum curve of the mechanochromic epoxy resin composite material prepared in Example 1 of the present invention before and after compression deformation.

[0026] Figure 3 These are fluorescence micrographs of the mechanochromic epoxy resin composite material prepared in Example 1 of the present invention after compression deformation under a pressure of 20 MPa; (a) fluorescence micrograph at low magnification; (b) fluorescence micrograph at high magnification.

[0027] Figure 4 The figures show the color change results of the mechanochromic epoxy resin composite material prepared in Example 2 of this invention under different pressures under natural light; in the figures, (a) is the sample before pressure testing; (b) is the color change result under 7 MPa pressure; (c) is the color change result under 10 MPa pressure; and (d) is the color change result under 20 MPa pressure.

[0028] Figure 5is a fluorescence color change result diagram of the piezochromic epoxy resin composite material prepared in Example 2 of the present application under ultraviolet light conditions corresponding to different pressures; in the diagram, (a) sample before pressure test; (b) fluorescence color change result under 7 MPa pressure; (c) fluorescence color change result under 10 MPa pressure; (d) fluorescence color change result under 20 MPa pressure;

[0029] Figure 6 is a result diagram of the settlement of the alumina filler in the epoxy resin composite material prepared in Comparative Example 2 of the present application;

[0030] Figure 7 is a result diagram of the settlement of the alumina filler in the epoxy resin composite material prepared in Comparative Example 3 of the present application;

[0031] Figure 8 is a result diagram of the settlement of the alumina filler in the piezochromic epoxy resin composite material prepared in Example 5 of the present application. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in conjunction with the examples in the present application. Obviously, the described examples are a part of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0033] The present application provides, in a first aspect, a preparation method of a piezochromic epoxy resin composite material, a preparation flowchart of which is shown, for example, as Figure 1 The method comprises the following steps:

[0034] (1) the rhodamine 6G is mixed with ethylenediamine uniformly with anhydrous ethanol, and then refluxed, filtered, washed and dried to obtain a modified rhodamine; in the present application, the washing is performed, for example, with anhydrous ethanol, and the drying is performed, for example, at 50-80℃ for 2-5h;

[0035] (2) the modified rhodamine is mixed with the epoxy resin uniformly, and then treated at 130-180℃ (for example, 130℃, 140℃, 150℃, 160℃, 170℃ or 180℃) for 2-4h (for example, 2h, 2.5h, 3h, 3.5h or 4h) to obtain a rhodamine modified epoxy resin; in the present application, after the ethylenediamine modified rhodamine 6G is introduced into the epoxy resin, the force can act on the chemical bond directly from both ends of the weak bond (C-N bond) along the polymer chain after stress, so that the rhodamine molecules are converted from the almost non-fluorescent closed ring form to the colored fluorescent open ring form, and the piezochromic effect is achieved;

[0036] (3) the rhodamine modified epoxy resin, the curing agent and the accelerator are mixed uniformly to obtain a first mixture, then the nano-aluminum oxide (nano-Al2O3) is added into the first mixture and mixed uniformly to obtain a second mixture, then the second mixture is treated by stirring at 60-100°C (for example, 60°C, 70°C, 80°C, 90°C or 100°C) to obtain a pre-crosslinking material with a viscosity of 40000-80000 cps; the time for the stirring treatment is not limited specifically in the present application, and it is only required to ensure that the pre-crosslinking material with a viscosity of 40000-80000 cps can be obtained; in the present application, the time for the stirring treatment at 60-100°C can be, for example, 30-60 min; the stirring speed for the stirring treatment is not limited specifically in the present application, and it can be, for example, 100-400 r / min; in the present application, the nano-aluminum oxide is nano-spherical aluminum oxide, and the particle size of the nano-aluminum oxide is not limited specifically in the present application, and it can be, for example, 80-100 nm;

[0037] (4) the pre-crosslinking material is first cured under vacuum at 70-90°C (for example, 70°C, 75°C, 80°C, 85°C or 90°C) for 3-6 h (for example, 3, 4, 5 or 6 h), and then cured at 120-140°C (for example, 120°C, 125°C, 130°C, 135°C or 140°C) for 10-15 h (for example, 10, 11, 12, 13, 14 or 15 h) to obtain a force-induced discoloration epoxy resin composite (abbreviated as epoxy resin composite); the vacuum degree of the vacuum is not limited specifically in the present application, and it is preferably -0.08 MPa to -0.1 MPa; in the present application, the pre-crosslinking is performed by heating and stirring at 60-100°C before curing.

[0038] The force-induced color-changing epoxy resin composite prepared by the present application is a composite material of a rhodamine force-sensitive group modified epoxy resin and nano-aluminum oxide, which is a mechanical force response composite material with more obvious color development and fluorescence response, and is applied to structural stress detection and detection of small damage or cracks after stress and fatigue damage in engineering; the present application successfully prepares a structural damage detection epoxy resin composite which can significantly improve the stress color development effect and strengthen the fluorescence opening response without sacrificing the mechanical properties by the combination of rhodamine force-sensitive group modification and the addition of nano-aluminum oxide; the epoxy resin composite in the present application not only improves the stress color development effect of the rhodamine modified epoxy resin, but also maintains excellent mechanical properties, so that it becomes an ideal resin-based damage detection material, especially suitable for use in high-precision and high-force-sensitive engineering, and the epoxy resin composite in the present application can significantly improve the apparent characteristics of the resin-based material when it is damaged and cracked, and the technology can be mainly applied to detect the stress condition of the material and predict potential damage, and has a wide application prospect in the fields of aerospace, automobile manufacturing, electronic products and the like.

[0039] The force-induced color-changing epoxy resin composite prepared by the present application is a composite material of a rhodamine force-sensitive group modified epoxy resin and nano-aluminum oxide, which is a mechanical force response composite material with more obvious color development and fluorescence response, and is applied to structural stress detection and detection of small damage or cracks after stress and fatigue damage in engineering; the present application successfully prepares a structural damage detection epoxy resin composite which can significantly improve the stress color development effect and strengthen the fluorescence opening response without sacrificing the mechanical properties by the combination of rhodamine force-sensitive group modification and the addition of nano-aluminum oxide; the epoxy resin composite in the present application not only improves the stress color development effect of the rhodamine modified epoxy resin, but also maintains excellent mechanical properties, so that it becomes an ideal resin-based damage detection material, especially suitable for use in high-precision and high-force-sensitive engineering, and the epoxy resin composite in the present application can significantly improve the apparent characteristics of the resin-based material when it is damaged and cracked, and the technology can be mainly applied to detect the stress condition of the material and predict potential damage, and has a wide application prospect in the fields of aerospace, automobile manufacturing, electronic products and the like.

[0040] The existing alumina filled epoxy resin composite material is cured, and the alumina particles in the material are usually obvious in sedimentation, and the cross-section layering of the epoxy resin composite material is usually more serious with the increase of the alumina content, which can cause the performance difference of each part of the material, the uneven strength distribution of the composite material, the reduction of the durability, the unstable mechanical properties and the great increase of the production cost. In order to solve this problem, a method for making the nano alumina filler in the rhodamine modified epoxy resin more uniform is needed. The present application finds through a large number of experiments that if the rhodamine modified epoxy resin is simply mixed with the nano alumina and directly heated and cured, two results can occur: if the initial curing temperature is too low, the viscosity of the composite epoxy resin can remain low in the early stage, which can increase the sedimentation rate of the nano alumina filler, even if the temperature is increased to the curing requirement in the later stage, the obvious alumina filled surface and the epoxy resin rich surface can be formed; if the initial curing temperature is too high, the rhodamine modified epoxy resin can be rapidly cured, the temperature difference between the inside and outside can be sharply increased in a short time, the residual stress in the epoxy resin composite material can cause cracking and reduce the mechanical properties, the air entering can not be discharged in time and small air bubbles can appear at the bottom or inside of the sample, which can cause defects such as cavity, crack, etc., reduce the strength of the epoxy resin composite material and reduce the service life of the epoxy resin composite material, therefore, the present application finds that the sedimentation problem of the nano alumina filler cannot be effectively solved by only controlling the heating and curing curve.

[0041] Unlike the way of controlling the heating curing curve alone, in order to further solve the problem of obvious sedimentation of nano-alumina particles in the epoxy resin material, in the process of preparing the force-induced color epoxy resin composite material by using nano-alumina as filler to fill the rhodamine modified epoxy resin, the second mixture is subjected to stirring treatment, and a pre-crosslinking material with a viscosity controlled in the range of 40000-80000 cps is obtained, and the curing process of the epoxy resin is optimized, it is found that when the viscosity of the pre-crosslinking material is controlled in the range of 40000-80000 cps during pre-curing and pouring, the viscous resistance of particle sedimentation is effectively increased, on the basis of not changing the composition of the epoxy resin composite material, the interface bonding degree of the rhodamine modified epoxy resin and the nano-alumina is obviously enhanced, the dispersity and uniformity of the nano-alumina in the rhodamine modified epoxy resin are obviously improved, the problem of sedimentation of the nano-alumina filler can be effectively solved, and the performance of the epoxy resin composite material is improved; in the present application, the viscosity of the pre-crosslinking material is controlled in the range of 40000-80000 cps, which can effectively prevent the sedimentation of the nano-alumina filler and ensure the quality and performance of the epoxy resin composite material; if the viscosity of the pre-crosslinking material is too low, the nano-alumina particles are easy to precipitate to the bottom of the epoxy resin, which leads to uneven distribution of the nano-alumina filler during the curing process, thereby affecting the force-induced color and mechanical properties of the epoxy resin composite material, and if the viscosity of the pre-crosslinking material is too high, the flowability of the pre-crosslinking material during the curing process will be affected, which leads to uneven filling of the mold and difficulty in removing the bubbles, thereby affecting the compactness and overall performance of the epoxy resin composite material.

[0042] The force-induced color rhodamine force-induced color sensitive group in the prepared force-induced color epoxy resin composite material can be activated by scratching or uniaxial compression, and shows reversible color change and red fluorescence opening response, and by combining the modified rhodamine with the epoxy resin, stress-dependent color change response under uniaxial compression and hydrostatic pressure can be realized; in order to further improve the flaw detection color development degree of the epoxy resin composite material and reduce the threshold of the fluorescence opening response, a new anti-settling pre-crosslinking method is used to treat and formulate a corresponding curing program, the nano-alumina filler is uniformly filled in the rhodamine modified epoxy resin, the sedimentation of the nano-alumina is effectively prevented, and the epoxy resin composite material with lower sedimentation rate and more uniform material quality is prepared, thereby being beneficial to improving the force-induced color characteristics and mechanical properties of the epoxy resin composite material.

[0043] According to some preferred embodiments, the molar ratio of the Rhodamine 6G to the ethylenediamine is 1:(3.5-4.5) (e.g. 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4 or 1:4.5); the mass ratio of the anhydrous ethanol to the Rhodamine 6G is (10-15):1 (e.g. 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1); and / or the temperature of the reflux reaction is 70-90℃ (e.g. 70℃, 75℃, 80℃, 85℃ or 90℃), and the time of the reflux reaction is 18-30h (e.g. 18, 20, 22, 24, 26, 28 or 30h).

[0044] According to some specific embodiments, step (1) is: dissolving Rhodamine 6G in anhydrous ethanol in a round-bottom flask equipped with a reflux condenser, then adding excess ethylenediamine and mixing uniformly, and then refluxing at 80℃ under argon atmosphere for 24h; filtering the obtained substance, washing with anhydrous ethanol for three times, and then drying in an oven at 60℃ for 3h to obtain a dry powder product, which is the modified Rhodamine; preferably, the stirring speed of the reflux reaction is 100-400r / min; in the present application, the substance obtained by reflux reaction forms a stratified state after stopping stirring, the upper layer is the solvent of the reaction liquid, and the lower layer is the product, for example, using a Buchner funnel for filtering.

[0045] According to some preferred embodiments, the epoxy resin is a bisphenol A type epoxy resin, preferably, the bisphenol A type epoxy resin is E51 liquid epoxy resin; and / or the mass ratio of the modified Rhodamine to the epoxy resin is 1:(15-25) (e.g. 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24 or 1:25).

[0046] According to some specific embodiments, step (2) is: mixing the modified Rhodamine and excess epoxy resin uniformly in a round-bottom flask, and then treating at 150℃ under argon atmosphere for 3h to obtain a Rhodamine modified epoxy resin.

[0047] According to some preferred embodiments, the curing agent is an acid anhydride type curing agent and / or an amine type curing agent; the present application does not have special requirements for the acid anhydride type curing agent and the amine type curing agent, and those skilled in the art can choose according to needs, preferably, the acid anhydride type curing agent is a mixture of pyromellitic dianhydride and maleic anhydride (alias: maleic anhydride) in a mass ratio of (70-80):(20-30), and the amine type curing agent is polyetheramine curing agent D230; and / or the accelerator is DMP-30 (2,4,6-tris(dimethylaminomethyl)phenol).

[0048] According to some specific embodiments, when the curing agent is an amine curing agent, the second mixture is stirred at 60-70℃ for 30-60min to obtain a pre-crosslinking material with a viscosity of 40000-80000cps; when the curing agent is an acid anhydride curing agent, the second mixture is first stirred at 60-70℃ for 30-45min, and then stirred at 70-100℃ for 5-15min to obtain a pre-crosslinking material with a viscosity of 40000-80000cps.

[0049] According to some preferred embodiments, the mass ratio of the rhodamine-modified epoxy resin, the curing agent and the accelerator is 100:(20-40):(1-5) (e.g. 100:20:1, 100:20:2, 100:20:3, 100:20:4, 100:20:5, 100:30:1, 100:30:2, 100:30:3, 100:30:4, 100:30:5, 100:40:1, 100:40:2, 100:40:3, 100:40:4 or 100:40:5).

[0050] According to some preferred embodiments, the mass ratio of the first mixture to the nano-aluminum oxide is 100:(20-70) (e.g. 100:20, 100:25, 100:30, 100:35, 100:40, 100:45, 100:50, 100:55, 100:60, 100:65 or 100:70).

[0051] According to some preferred embodiments, the stirring speed of the stirring treatment is 100-400r / min.

[0052] According to some preferred embodiments, the stirring treatment is carried out in an air atmosphere; and / or the curing at 120-140℃ is carried out in an air atmosphere; and other operations of the present application are also carried out in an air atmosphere unless otherwise specified.

[0053] According to some specific embodiments, step (3) is: rhodamine-modified epoxy resin, curing agent, accelerator are weighed according to the mass ratio of 100:30:2, stirred uniformly by hand to obtain a first mixture, then nano-Al2O3filler is added to the first mixture, stirred by hand until mixed uniformly to obtain a second mixture, then the second mixture is placed into a stirring system for stirring treatment at 60℃ in an air atmosphere until a pre-crosslinking material with a viscosity of 40000-80000cps is obtained.

[0054] According to some specific embodiments, step (4) is: adding the pre-crosslinked material into a preheated mold to cure under vacuum at a temperature of 80℃ for 4h, then curing under an air atmosphere at 130℃ for 12h, and finally taking out the sample after the mold is cooled to room temperature to obtain the force-induced color-changing epoxy resin composite; in the present application, the mold is a stainless steel plate mold; in the present application, room temperature refers to room temperature of 15-30℃.

[0055] The present application provides, in a second aspect, a force-induced color-changing epoxy resin composite prepared by the preparation method described in the first aspect of the present application.

[0056] The present application provides, in a third aspect, an application of the force-induced color-changing epoxy resin composite prepared by the preparation method described in the first aspect of the present application in damage detection. The force-induced color-changing epoxy resin prepared by the present application is a composite material of a rhodamine force-induced color-changing force-sensitive group modified epoxy resin combined with nano-aluminum oxide, which has more accurate and obvious fluorescence and color change effect after being broken under stress, and can play a role of precise early warning.

[0057] The present application will be further described below by way of examples, but the scope of protection of the present application is not limited to these examples.

[0058] Example 1

[0059] ① In a round-bottom flask equipped with a reflux condenser, rhodamine 6G was dissolved in anhydrous ethanol, then ethylenediamine was added and mixed uniformly, and then refluxed at 80℃ under an argon atmosphere at 300r / min for 24h; the obtained material was filtered, washed with anhydrous ethanol three times, and then dried in an oven at 60℃ for 3h to obtain modified rhodamine; wherein the mass ratio of anhydrous ethanol to rhodamine 6G was 12:1, and the molar ratio of the rhodamine 6G to ethylenediamine was 1:4.

[0060] ② The modified rhodamine obtained in step ① and E51 liquid epoxy resin were mixed uniformly in a round-bottom flask, and then treated at 150℃ under an argon atmosphere for 3h to obtain a rhodamine modified epoxy resin; wherein the mass ratio of the modified rhodamine to the E51 liquid epoxy resin was 1:20.

[0061] ③ First, clean the mold thoroughly and evenly coat the inner surface of the mold with a layer of release agent. Then, place the mold in an oven and preheat it to 80°C and keep it warm. Weigh the Rhodamine-modified epoxy resin, anhydride curing agent, and accelerator (DMP-30) obtained in step ② according to a mass ratio of 100:30:2. After manually stirring evenly, a first mixture is obtained. Then, nano-alumina filler is added to the first mixture and manually stirred evenly to obtain a second mixture. The second mixture is then stirred at 60°C in air for 40 minutes and then stirred at 100°C in air for 10 minutes to obtain a pre-crosslinked material with a viscosity of 70,000 cps. The stirring speed is 300 r / min. The anhydride curing agent is a mixture of pyromellitic dianhydride and maleic anhydride in a mass ratio of 75:25. The mass ratio of the first mixture to the nano-alumina is 100:20.

[0062] ④ Add the pre-crosslinked material obtained in step ③ into the preheated mold, cure it for 4 hours under vacuum (vacuum degree of -0.095MPa) and temperature of 80℃, then cure it for 12 hours in air atmosphere at 130℃. Finally, after the mold cools to room temperature, take out the sample to obtain the mechanochromic epoxy resin composite material.

[0063] The fluorescence spectrum curves of the mechanochromic epoxy resin composite material prepared in this embodiment before and after compression deformation under a pressure of 20 MPa are shown in the figure. Figure 2 As shown; from Figure 2 The results show that the broad peaks in the 380–500 nm range before and after compression deformation are generated by the self-fluorescence of the rhodamine-modified epoxy resin. After compression deformation, a relatively sharp peak appears in the 550–607 nm range, which is significantly different from the self-fluorescence peaks of the rhodamine-modified epoxy resin in the 380–500 nm range. This indicates that the sample after compression deformation has changed color under stress and activated the fluorescence response. This shows that the epoxy resin composite material prepared in this invention has the characteristic of force-induced color change.

[0064] Fluorescence micrograph of the mechanochromic epoxy resin composite material prepared in this embodiment after compression deformation under 20 MPa pressure, as shown in the figure. Figure 3 As shown; from Figure 3 The results show that the mechanochromic epoxy resin composite material filled with nano-alumina prepared by this invention has a significant mechanochromic fluorescence effect under 20MPa pressure, and the color change area is obviously linear. The color change area is highly consistent with the damaged and cracked area, which can better highlight the weak part of the epoxy resin composite material and play a precise and sufficient early warning role.

[0065] Example 2

[0066] Example 2 is basically the same as Example 1, except that:

[0067] 3. First clean the mold, and then evenly coat a layer of release agent on the inner surface of the mold, then put the mold into the oven and preheat to 80°C and keep warm; the rhodamine modified epoxy resin, amine curing agent, accelerator (DMP-30) obtained in step 2 are weighed according to a mass ratio of 100:30:2, manually stirred uniformly to obtain a first mixture, then nano-aluminum oxide filler is added to the first mixture, and manually stirred uniformly to obtain a second mixture, then the second mixture is stirred and treated at 60°C in air for 40 min to obtain a pre-crosslinking material with a viscosity of 68,000 cps; wherein the stirring speed is 300 r / min, the amine curing agent is polyether amine curing agent D230, and the mass ratio of the first mixture to the nano-aluminum oxide is 100:20.

[0068] The stress-induced color change results of the epoxy resin composite material prepared in this example under natural light corresponding to different pressures are shown in FIG. 1; the fluorescence color change results of the stress-induced color change epoxy resin composite material prepared in this example under ultraviolet light (ultraviolet light wavelength 365 nm) corresponding to different pressures are shown in FIG. 2; and the fluorescence color change results of the stress-induced color change epoxy resin composite material prepared in this example under ultraviolet light (ultraviolet light wavelength 365 nm) corresponding to different pressures are shown in FIG. 3. Figure 4 Figure 5 Figure 4 Figure 5 It can be seen from the results of FIGS. 1-3 that as the pressure increases, the stress-induced color change performance of the stress-induced color change epoxy resin composite material prepared in this example is improved, and the fluorescence color change performance is more obvious.

[0069] Example 3

[0070] Example 3 is basically the same as Example 1, except that:

[0071] 3. First clean the mold, and then evenly coat a layer of release agent on the inner surface of the mold, then put the mold into the oven and preheat to 80°C and keep warm; the rhodamine modified epoxy resin, amine curing agent, accelerator (DMP-30) obtained in step 2 are weighed according to a mass ratio of 100:30:2, manually stirred uniformly to obtain a first mixture, then nano-aluminum oxide filler is added to the first mixture, and manually stirred uniformly to obtain a second mixture, then the second mixture is stirred and treated at 60°C in air for 40 min to obtain a pre-crosslinking material with a viscosity of 68,000 cps; wherein the stirring speed is 300 r / min, the amine curing agent is polyether amine curing agent D230, and the mass ratio of the first mixture to the nano-aluminum oxide is 100:20.

[0072] Example 4

[0073] Example 4 is basically the same as Example 1, except that: ​​​

[0074] III. First, clean the mold and evenly coat a layer of release agent on the inner surface of the mold, then preheat the mold to 80°C in an oven and keep it warm; the rhodamine modified epoxy resin, anhydride curing agent and accelerator (DMP-30) obtained in step II are weighed according to a mass ratio of 100:30:2, stirred uniformly by hand to obtain a first mixture, then nano-aluminum oxide filler is added to the first mixture and stirred uniformly by hand to obtain a second mixture, then the second mixture is stirred at 60°C in air for 50 min and then stirred at 100°C in air for 20 min to obtain a pre-crosslinking material with a viscosity of 90000 cps; the stirring speed is 300 r / min, the anhydride curing agent is a mixture of phthalic anhydride and maleic anhydride in a mass ratio of 75:25, and the mass ratio of the first mixture to the nano-aluminum oxide is 100:20.

[0075] Example 5

[0076] Example 5 is basically the same as Example 2, except that:

[0077] III. First, clean the mold and evenly coat a layer of release agent on the inner surface of the mold, then preheat the mold to 80°C in an oven and keep it warm; the rhodamine modified epoxy resin, anhydride curing agent and accelerator (DMP-30) obtained in step II are weighed according to a mass ratio of 100:30:2, stirred uniformly by hand to obtain a first mixture, then nano-aluminum oxide filler is added to the first mixture and stirred uniformly by hand to obtain a second mixture, then the second mixture is stirred at 60°C in air for 50 min and then stirred at 100°C in air for 20 min to obtain a pre-crosslinking material with a viscosity of 90000 cps; the stirring speed is 300 r / min, the anhydride curing agent is a mixture of phthalic anhydride and maleic anhydride in a mass ratio of 75:25, and the mass ratio of the first mixture to the nano-aluminum oxide is 100:20.

[0078] Comparative Example 1

[0079] Comparative Example 1 is basically the same as Example 1, except that:

[0080] III. First, clean the mold and evenly coat a layer of release agent on the inner surface of the mold, then preheat the mold to 80°C in an oven and keep it warm; the rhodamine modified epoxy resin, anhydride curing agent and accelerator (DMP-30) obtained in step II are weighed according to a mass ratio of 100:30:2, stirred uniformly by hand to obtain a first mixture, then nano-aluminum oxide filler is added to the first mixture and stirred uniformly by hand to obtain a second mixture, then the second mixture is stirred at 60°C in air for 50 min and then stirred at 100°C in air for 20 min to obtain a pre-crosslinking material with a viscosity of 90000 cps; the stirring speed is 300 r / min, the anhydride curing agent is a mixture of phthalic anhydride and maleic anhydride in a mass ratio of 75:25, and the mass ratio of the first mixture to the nano-aluminum oxide is 100:20.

[0081] ④The second mixture obtained in step ③ is added to the preheated mold, and is cured under the condition of vacuum (vacuum degree is -0.095 MPa) and temperature of 80℃ for 4h, then cured under the condition of air atmosphere at 130℃ for 12h, finally the sample is taken out after the mold is cooled to room temperature, to obtain the epoxy resin composite material.

[0082] The epoxy resin composite material prepared in the present comparative example has no nano-alumina filling, and has the disadvantages of high pressure response threshold and not obvious fluorescence opening response under natural light and 365nm ultraviolet light; the epoxy resin composite material without alumina filling in the present comparative example has no discoloration under 7MPa, and only has slight discoloration and slight fluorescence discoloration under 15MPa, and has obvious color change and fluorescence response only when the pressure is increased to 30MPa.

[0083] Comparative Example 2

[0084] Comparative Example 2 is basically the same as Example 1, except that:

[0085] ③The mold is first cleaned and a layer of release agent is evenly coated on the inner surface of the mold, and then the mold is preheated to 80℃ in an oven; the rhodamine modified epoxy resin, acid anhydride curing agent and accelerator (DMP-30) obtained in step ② are weighed according to the mass ratio of 100:30:2, and are manually stirred to obtain a first mixture, then nano-alumina filler is added to the first mixture and stirred to obtain a second mixture; wherein the acid anhydride curing agent is a mixture of pyromellitic dianhydride and maleic anhydride in a mass ratio of 75:25; the mass ratio of the first mixture to the nano-alumina is 100:20.

[0086] ④The second mixture obtained in step ③ is added to the preheated mold, and is cured under the condition of vacuum (vacuum degree is -0.095 MPa) and temperature of 80℃ for 4h, then cured under the condition of air atmosphere at 130℃ for 12h, finally the sample is taken out after the mold is cooled to room temperature, to obtain the epoxy resin composite material.

[0087] Comparative Example 3

[0088] Comparative Example 3 is basically the same as Comparative Example 2, except that:

[0089] ③Firstly, the mold is cleaned and a layer of release agent is evenly coated on the inner surface of the mold, and then the mold is preheated to 80℃ in an oven; the rhodamine modified epoxy resin, amine curing agent and accelerator (DMP-30) obtained in step ② are weighed according to a mass ratio of 100:30:2, and after being manually stirred uniformly, a first mixture is obtained, then nano-aluminum oxide fillers are added to the first mixture and manually stirred uniformly to obtain a second mixture; wherein the amine curing agent is polyether amine curing agent D230; the mass ratio of the first mixture to the nano-aluminum oxide is 100:20.

[0090] The settling results of the aluminum oxide fillings in the epoxy resin composite materials prepared in Comparative Examples 2-3 are tested, as shown in Figure 6 and Figure 7 From the results of Figure 6 and Figure 7 , it can be seen that without pre-crosslinking operation before the curing process of the preparation of the epoxy resin composite material, the settling of the aluminum oxide particles in the material after curing is obvious, and when the mass ratio of the nano-aluminum oxide to the first mixture is only 20:100, the content of the nano-aluminum oxide is low, and the cross-sectional layering phenomenon is serious; and this phenomenon will become more serious with the increase of the content of the aluminum oxide; the settling results of the aluminum oxide fillings in the force-induced color-changing epoxy resin composite material prepared in Example 4 are tested, as shown in Figure 8 From the results of Figure 8 , it can be seen that the content of the aluminum oxide in the force-induced color-changing epoxy resin composite material prepared in Example 5 is as high as 70% of the mass percentage of the first mixture composed of the rhodamine modified epoxy resin, amine curing agent and accelerator, which is obviously different from Comparative Examples 2 and 3, but the aluminum oxide can be uniformly dispersed in the force-induced color-changing epoxy resin composite material without the settling phenomenon.

[0091] Comparative Example 4

[0092] ①Firstly, the mold is cleaned and a layer of release agent is evenly coated on the inner surface of the mold, and then the mold is preheated to 80℃ in an oven; E51 liquid epoxy resin, rhodamine 6G, acid anhydride curing agent and accelerator (DMP-30) are weighed according to a mass ratio of 100:5:30:2, and after being manually stirred uniformly, a first mixture is obtained, then nano-aluminum oxide fillers are added to the first mixture and manually stirred uniformly to obtain a second mixture; wherein the acid anhydride curing agent is a mixture of pyromellitic dianhydride and maleic anhydride in a mass ratio of 75:25; the mass ratio of the first mixture to the nano-aluminum oxide is 100:20.

[0093] (2) The second mixture obtained in step (1) is added into the preheated mold to be cured under vacuum (vacuum degree: -0.095 MPa) and at a temperature of 80°C for 4 hours, and then cured under air atmosphere at 130°C for 12 hours, and finally the sample is taken out after the mold is cooled to room temperature to obtain the epoxy resin composite material.

[0094] The bending strength of the epoxy resin composite material obtained in each example and each comparative example, the sedimentation of the nano-alumina, and the pressure threshold for producing slight discoloration under natural light and the pressure threshold for producing slight fluorescent discoloration under 365 nm ultraviolet light are measured, and the results are shown in Table 1.

[0095] Table 1

[0096]

[0097] In Table 1, the symbol "-" represents that the performance index does not exist.

[0098] From the results in Table 1, it can be seen that the present application can significantly improve the stress-induced color effect of the epoxy resin composite material, strengthen the fluorescent opening response, and effectively prevent the sedimentation of nano-alumina; the pressure threshold for producing slight discoloration under natural light and the pressure threshold for producing slight fluorescent discoloration under ultraviolet light of the sample of Example 1 filled with nano-alumina are obviously smaller than those of Comparative Example 1 without nano-alumina filling, and the pressure threshold for producing slight discoloration under natural light and the pressure threshold for producing slight fluorescent discoloration under ultraviolet light of the sample of Comparative Example 1 without nano-alumina filling are obviously higher, which is insufficient for micro-damage early warning; while the pressure threshold for producing slight discoloration under natural light and the pressure threshold for producing slight fluorescent discoloration under ultraviolet light of the sample of the present application filled with nano-alumina are obviously lower, which can play an accurate and sufficient early warning role.

[0099] The parts of the present application not described in detail are known to those skilled in the art.

[0100] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present application.

Claims

1. A method for producing a force-induced color-changing epoxy resin composite material, characterized by, The method comprises the following steps: (1) mixing rhodamine 6G and ethylenediamine uniformly with anhydrous ethanol, then refluxing, filtering, washing and drying to obtain modified rhodamine; (2) mixing the modified rhodamine and epoxy resin uniformly, then treating at 130-180℃ for 2-4h to obtain rhodamine modified epoxy resin; (3) mixing the rhodamine modified epoxy resin, curing agent and accelerator uniformly to obtain a first mixture, then adding nano-alumina to the first mixture and mixing uniformly to obtain a second mixture, then stirring and treating the second mixture at 60-100℃ to obtain a pre-crosslinking material with a viscosity of 40000-80000cps; (4) curing the pre-crosslinking material at 70-90℃ under vacuum for 3-6h, then curing at 120-140℃ for 10-15h to obtain a photochromic epoxy resin composite material.

2. The preparation method according to claim 1, wherein: the molar ratio of the rhodamine 6G to the ethylenediamine is 1:(3.5-4.5); the mass ratio of the anhydrous ethanol to the rhodamine 6G is (10-15):1; and / or the refluxing temperature is 70-90℃, and the refluxing time is 18-30h.

3. The preparation method according to claim 1, wherein: the epoxy resin is bisphenol A type epoxy resin; and / or the mass ratio of the modified rhodamine to the epoxy resin is 1:(15-25).

4. The preparation method according to claim 1, wherein: the curing agent is an acid anhydride curing agent and / or an amine curing agent; and / or the accelerator is DMP-30.

5. The preparation method according to claim 1, wherein: the mass ratio of the rhodamine modified epoxy resin, the curing agent and the accelerator is 100:(20-40):(1-5).

6. The preparation method according to claim 1, wherein: the mass ratio of the first mixture to the nano-alumina is 100:(20-70).

7. The preparation method according to claim 1, wherein: the stirring speed of the stirring treatment is 100-400r / min.

8. The preparation method according to claim 1, wherein: the stirring treatment is carried out in air atmosphere; and / or the curing at 120-140℃ is carried out in air atmosphere.

9. A photochromic epoxy resin composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of a photochromic epoxy resin composite material prepared by the preparation method according to any one of claims 1 to 8 in damage detection. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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