Sheet molding compound of epoxy resin matrix and method for producing same

Abstract

The application discloses a kind of epoxy resin matrix sheet molding compound and preparation method thereof, it is related to composite material technical field.The weight parts of the following raw material components are included:epoxy resin 70-100, modified epoxy resin 10-20, long straight chain active epoxy diluent 10-15, latent curing agent 7.5-10, accelerator 0.5-1.0, internal release agent 1.5-4.5, filler 120-180, thickening agent 0.5-4.5, color paste 0.1-0.5, chopped yarn 50-80.The application is with epoxy resin as matrix, in combination with polyester sheet molding compound thickening mechanism, design a new type of epoxy resin SMC, and realizes good thickening, demolding, with shape and fast curing purposes, and then with the epoxy SMC as raw material, production epoxy resin moulded part.The application has no VOC emission in sheet production process, and product performance is excellent, with high mechanical strength, electrical performance and flame retardant performance, and is expected to achieve wide application in insulation material, rail transit, automobile industry and other fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, in particular to a sheet molding compound of an epoxy resin matrix and a preparation method thereof. BACKGROUND

[0002] Sheet molding compound (SMC) refers to a sheet-shaped raw material that uses a thermosetting resin as a main raw material, adds thickening agents, low shrinkage agents, mold release agents, fillers and other additives, and is reinforced by chopped fibers (usually glass fibers or carbon fibers). The molding process has the advantages of high production efficiency, stable product quality and low cost, and is suitable for large-scale production of high-precision, complex structure, high-requirement appearance, and different requirements of parts or products, and is widely used in the fields of automobiles, electronics and electrical appliances, and infrastructure.

[0003] At present, the resins used in sheet molding compounds are mainly unsaturated polyester resins and epoxy vinyl resins, and the thickening methods mainly include two kinds: (1) alkali earth metal oxide or hydroxide thickening, which mainly grows UP molecules by forming a coordination bond between the carboxyl group in the resin and the metal ion; (2) isocyanate and prepolymer modification (ITP method or chemical method), which is mainly used for low-acid-value and high-hydroxyl-value resin systems, and grows molecules by forming covalent bonds. In the two thickening methods, the first kind often causes the load between the fiber and the resin to decrease due to the breakage of the coordination bond, resulting in problems such as yarn exposure during pressing, and the second kind of thickening method has a relatively firm covalent bond, and the viscosity decreases less when heated, but the thickening effect is still not ideal. Among them, the reaction speed of isocyanate and hydroxyl group is fast, and the reaction with carboxyl group is slow, which produces CO2 and bubbles during the pressing process. On the other hand, due to the use of low shrinkage agents, the traditional sheet material is not resistant to high temperature, and in a high temperature environment, pyrolysis easily occurs, and due to the poor interfacial affinity of unsaturated polyester or epoxy vinyl resin and glass fiber, the surface porosity of the product is high, which further leads to the serious limitation of its application in many application fields, especially in the electrical insulation field.

[0004] Epoxy resin, as an important thermosetting resin, has the performance advantages of high mechanical properties, strong corrosion resistance, heat resistance, water resistance and mold resistance, etc. depending on the ring-opening reaction of its epoxy functional group and the polar structure. Epoxy resin has strong interfacial adhesion with glass fiber, carbon fiber and various substrates such as metal, concrete and glass, and is also used as an important adhesive in the fields of electronic processing, aerospace, automobile and building.

[0005] However, since the epoxy resin curing reaction is continuous, i.e. it cannot be controlled at a certain reaction stage, the epoxy resin cannot realize the stage thickening, i.e. the curing reaction is irreversible, once the curing starts, it is difficult to ensure the flowability of the epoxy resin in the pressing process, and in the thickening mechanism, it is difficult to realize the physical thickening, and the isocyanate is used for thickening, which increases the cost, and due to the irreversibility of the reaction, the prepared sheet has a large hardness, and it is difficult to realize the shape pressing requirement of the SMC. SUMMARY

[0006] The present application provides a kind of epoxy resin matrix sheet molding compound and its preparation method, to solve the technical problems of the epoxy resin not thickening in the above background art, while avoiding the release of VOCs in the sheet production process and its influence on human health.

[0007] In order to achieve the above technical purpose, the present application mainly adopts the following technical scheme:

[0008] The present application provides a kind of epoxy resin matrix sheet molding compound, which comprises the following raw material components by weight: epoxy resin 70-100 parts, modified epoxy resin 10-20 parts, long straight chain active epoxy diluent 10-15 parts, latent curing agent 7.5-10 parts, accelerator 0.5-1.0 parts, internal release agent 1.5-4.5 parts, filler 120-180 parts, thickening agent 0.5-4.5 parts, chopped yarn 50-80 parts; wherein the modified epoxy resin has carboxyl functional group which reacts with divalent metal ion.

[0009] In the preferred embodiment of the present application, the epoxy resin is one or more of bisphenol A epoxy resin, phenolic epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, glycidyl ester type epoxy resin.

[0010] In the preferred embodiment of the present application, the modified epoxy resin is an epoxy resin which is functionally modified by amino benzoic acid.

[0011] Further, the modified epoxy resin is prepared by the following method:

[0012] The epoxy resin is added to the reaction kettle, heated to a constant temperature, and stirred under nitrogen protection conditions, amino benzoic acid is added, and stirring is continued for a period of time, then an organic metal salt catalyst is added, and the constant temperature is maintained under nitrogen protection conditions until the reaction is complete, and the modified epoxy resin is obtained after cooling.

[0013] Further, the constant temperature is 77-83℃, and the organic metal salt catalyst is selected from one or more of stannous octoate, dibutyltin dilaurate, MB20, BiCAT Zn, zirconium acetylacetonate, nickel acetylacetonate, and rubidium neodecanoate.

[0014] In a preferred embodiment of the present application, the long straight-chain active epoxy diluent is one or two of decyl glycidyl ether (AGE), 1,4-butanediol diglycidyl ether (BDDGE), trimethylolpropane triglycidyl ether (TPEG), ethylene glycol diglycidyl ether (EGDE), and 1,6-hexanediol diglycidyl ether (1,6-HDE), preferably decyl glycidyl ether (AGE).

[0015] In a preferred embodiment of the present application, the latent curing agent is one or two of dicyandiamide and its derivatives.

[0016] In a preferred embodiment of the present application, the accelerator is one or more of imidazole accelerators, urea derivative accelerators, boron trifluoride-amine complexes, quaternary ammonium salts, and triphenyl phosphine complexes; the internal release agent is one or more of lecithin, alkyl phosphate esters, stearic acid, and stearate; the filler is one or more of aluminum hydroxide, diatomite, calcium carbonate, calcium sulfate, and talc; and the thickening agent is one or more of magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, and barium oxide.

[0017] In a preferred embodiment of the present application, the chopped yarn is obtained by cutting continuous glass fibers to a nominal length of 30-55 mm, and the glass fiber is one of ECT / TM 468A, ECT / TM 468G, ECT / TM 468GE, ECT / TM 468T, and ECT / TM 468HS.

[0018] The present application also provides a method for preparing the sheet molding compound of the epoxy resin matrix as described above, comprising the following steps:

[0019] Step one, the epoxy resin, modified epoxy resin, long straight-chain active epoxy diluent, latent curing agent, internal release agent, color paste, and filler are added to a mixing kettle with a heat preservation heating device in proportion, and then the accelerator and thickening agent are added in proportion, and after mixing and stirring, a resin paste is obtained;

[0020] Step two, the cutting knife size is adjusted, the epoxy special yarn is cut into chopped yarn of a nominal length, and the chopped yarn is uniformly dispersed on a PE film, and the PE film with the chopped yarn is passed under a glue tank;

[0021] Step three, pump the resin paste into the glue tank, and adjust the glue amount with the card below the glue tank with the minimum size of 0.3mm; when the chopped yarn on the PE film passes below the glue tank, open the glue outlet to make the resin paste flow uniformly on the PE film, and cover a layer of PE film on the resin paste with the laminating machine;

[0022] Step four, the material obtained in step three is pulled into the chain type roller compactor with heating radiation, and is fully rolled, then is collected in a box or rolled, and is transferred to the drying room for thickening, so that the SMC sheet is obtained;

[0023] Step five, after the sheet is cured, the film is torn, the sheet is cut, and the number of layers is calculated according to the sample thickness according to 0.5mm per layer SMC, then the sheet is pressed by using a mold pressing machine, after the pressing is completed, the mold is lifted and the sample is taken out, and after cooling to room temperature, the edge is removed, so that the sheet molding compound of the epoxy resin matrix is obtained.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1. The sheet molding compound of the epoxy resin matrix prepared by the present application breaks the original three-dimensional network structure of the epoxy resin by adding a long straight chain active epoxy diluent, improves the defects that the existing epoxy resin SMC will appear yellowing and blackening under light and heat, and solves the technical problem that the existing SMC is prone to yellowing.

[0026] 2. The sheet molding compound of the epoxy resin matrix prepared by the present application further adds a modified epoxy resin on the basis of the epoxy resin matrix, the modified epoxy resin is prepared from amino benzoic acid and the base resin, the carboxyl functional group is added, and the carboxyl functional group on the modified epoxy resin reacts with the divalent metal ion in the thickening agent, so that the thickening effect of the epoxy resin SMC is achieved. Compared with the sheet molding compound prepared without adding the modified epoxy resin, the present application can better solve the basic problem of thickening the epoxy SMC.

[0027] 3. The present application provides a design concept and preparation method of epoxy SMC, and solves the problems of low strength, high porosity and high water absorption of unsaturated polyester SMC products. The present application uses epoxy resin as the matrix, and the modified epoxy resin with added carboxyl functional group is used for co-reaction, and a new type of epoxy resin SMC is designed by combining the thickening mechanism of polyester sheet molding compound, so that the purposes of good thickening, demolding, following shape and rapid curing are achieved. The epoxy SMC is used as the raw material to produce epoxy resin mold pressing parts, and there is no VOC emission in the sheet production process, and the product performance is excellent, and the product has high mechanical strength, electrical performance and flame retardant performance, and can be widely used in the fields of insulating materials, rail transit and automobile industry. DETAILED DESCRIPTION

[0028] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described below in conjunction with the embodiments. It should be understood that the embodiments described herein are only used to explain the present application and not used to limit the present application.

[0029] Preparation of modified epoxy resin in Example 1

[0030] 100 parts of epoxy resin were added into a reaction kettle, then the temperature was raised to 80℃, nitrogen protection was started, and stirring was started with a stirring speed of 500 r / min. Then 60 parts of amino benzoic acid were added, and after 3 minutes of stirring, 0.5 parts of an organic metal salt catalyst (which can be one or more of stannous octoate, dibutyltin dilaurate, MB20, BiCAT Zn, zirconium acetylacetonate, nickel acetylacetonate, and rubidium neodecanoate) was added. Nitrogen protection was continued, the temperature was maintained at 80℃, the reaction temperature range was 80℃±3℃, and the reaction was continued for 13 hours. After cooling, the modified epoxy resin was obtained, which was denoted as material A.

[0031] Preparation of epoxy SMC-1 in Example 2

[0032] Step one, preparation of resin paste: 90 parts of epoxy resin and 10 parts of material A prepared in Example 1 were added into a mixing kettle with a heat preservation and heating device, stirring was started with a stirring speed of 300 r / min. After mixing, 10 parts of AGE, 10 parts of dicyandiamide, 1.5 parts of internal release agent, 130 parts of filler, 0.3 parts of red paste, and 0.5 parts of organic urea accelerator UR300 were sequentially added into the mixing kettle. After 30 minutes of continuous stirring, water cooling was started, and after the temperature was cooled to below 35℃, 3 parts of thickening agent was added, and stirring was continued for 10 minutes. After mixing, the resin paste was pumped into a resin tank for use.

[0033] Step two, preparation of sheet: the yarn cutter was adjusted, the yarn length was controlled to be 40 mm, and the yarn running speed was controlled to be 5 m / min. A PE film was laid under the glue tank, and the chopped yarn was evenly dispersed on the PE film. The resin paste was uniformly dispersed on the PE film by the glue outlet of the glue tank. The height of the glue outlet was controlled by a caliper with an accuracy of 0.03 mm to ensure the content of the resin paste. Then, another PE film was laid on the resin paste and the fiber, and then the mixture was pulled into a track roller compactor with a radiation heating device. The length of the compactor was 5 m, the flow rate of the PE film was 1.5 m / min, and the temperature of the heating device was 45℃. After sufficient compaction, the resin paste was uniformly impregnated into the fiber. After the mixture was discharged from the compactor, it was pulled by the counter roller, transferred by the guide roller, and stretched, and then it was wound or boxed. The areal density of the sheet was 2.2-2.4 kg / m 2 , and then it was transferred to an oven. After 48 hours of thickening at 40℃, the epoxy resin sheet was obtained, which was denoted as SMC-1.

[0034] Mold pressing: take the test sample as an example (mold size is 300mm*300mm); after the film of the sheet obtained in step two of the embodiment is torn off, it is cut into 290mm*290mm, and the layering design is carried out according to 0.5mm / layer, for example, 10 layers are needed for pressing a 5mm thick sample. The specific pressing process is as follows: the temperature of the press is set to 150℃, after the temperature is stable, the mold is opened, and the outer release agent is sprayed, then the laid sheet is put into the mold cavity as a whole. The mold is closed, the pressure is 3MPa, after 45s of pressure maintaining, the pressure is increased to 10MPa, and after 30s, the pressure is increased to 15MPa, and the pressing time is determined according to 3min / mm, for example, for a 5mm sample, after full pressing, the sample is kept and pressed for 15min, then the mold is opened, the sample is taken out, after edge removal treatment, it is sent for inspection, processing and detection; the sample obtained in this embodiment is recorded as sample A.

[0035] Preparation of epoxy SMC-2

[0036] Step one, preparation of resin paste: take 85 parts of epoxy resin and 15 parts of material A prepared in example 1 into a mixing kettle with heat preservation and heating device, start stirring, set the speed to 300r / min, after mixing uniformly, add AGE 10 parts, dicyandiamide 8.5 parts, internal release agent 1.5 parts, filler 130 parts, red paste 0.3 parts, organic urea accelerator UR300 0.5 parts into the mixing kettle in turn, continue stirring for 30min, then cool down by water, cool down to below 35℃, then add thickening agent 3 parts, stir for 10min, mix uniformly, then pump the resin paste into the resin tank for use;

[0037] Step two, preparation of sheet: adjust the yarn cutter, control the length of the chopped yarn to be 40mm, and the yarn running speed to be 5m / min; lay PE film under the glue tank, uniformly disperse the chopped yarn on the PE film, pass through the glue outlet of the glue tank to uniformly disperse the resin paste on the PE film covered with chopped yarn; control the height of the glue outlet (control by caliper, accuracy 0.03mm) to ensure the content of the resin paste; then cover another layer of PE film on the resin paste and fiber, then pull into the track roller press with radiation heating device, the length of the roller press is 5m, the flow speed of the PE film is 1.5m / min, and the temperature of the heating device is 45℃; after sufficient rolling, the resin paste can uniformly impregnate the fiber, after the mixture comes out of the roller press, it is pulled by the counter roller, transferred by the guide roller, stretched, then wound or boxed, the surface density of the sheet is 2.2-2.4kg / m 2 , and transferred to the drying room, after thickening at 40℃ for 48h, the epoxy resin sheet is obtained, recorded as SMC-2.

[0038] Mould pressing: taking the test sample as an example (mould size: 300mm*300mm); after the film of the sheet obtained in step two of the example was removed, it was cut into 290mm*290mm, and was designed to be laid in 0.5mm / layer, for example, to press a 5mm thick sample, 10 layers were needed. The specific pressing process was as follows: the temperature of the press was set to 150℃, after the temperature was stable, the mould was opened, and the outer release agent was sprayed, then the laid sheet was put into the mould cavity as a whole. The mould was closed, the initial pressure was 3MPa, after 45s of pressure maintaining, the pressure was increased to 10MPa, and after 30s, the pressure was increased to 15MPa, and the pressing time was determined according to 3min / mm, for example, for a 5mm sample, after full pressure, the sample was kept for 15min after pressure maintaining, then the mould was opened, the sample was taken out, after edge removal, it was sent for inspection, processing and detection; the sample obtained in this example was recorded as sample M.

[0039] Preparation of epoxy SMC-3

[0040] Step one, preparation of resin paste: take epoxy resin 80 parts, material A 20 parts into the mixing kettle with heat preservation and heating device, start stirring, set the speed to 300r / min, after mixing evenly, add AGE 10 parts, dicyandiamide 7.0 parts, internal release agent 1.5 parts, filler 130 parts, red paste 0.3 parts, organic urea accelerator UR300 0.5 parts into the mixing kettle in turn, continue to stir for 30min, then cool down by water, cool down to below 35℃, then add thickening agent 3 parts, stir for 10min, mix evenly, then pump the resin paste into the resin tank for use;

[0041] Step two, preparation of sheet: adjust the yarn cutter, control the length of the chopped yarn to be 40mm, and the yarn running speed to be 5m / min; lay PE film under the glue tank, evenly disperse the chopped yarn on the PE film, pass through the glue outlet of the glue tank to make the resin paste evenly disperse on the PE film covered with chopped yarn; control the height of the glue outlet (control by caliper, accuracy 0.03mm) to ensure the content of the resin paste; then cover another layer of PE film on the resin paste and fiber, then pull into the track roller press with radiation heating device, the length of the roller press is 5m, the flow speed of the PE film is 1.5m / min, and the temperature of the heating device is 45℃; after sufficient rolling, the resin paste can be evenly impregnated with the fiber, after the mixture comes out of the roller press, it is pulled by the counter roller, transferred and stretched by the guide roller, then wound or boxed, the surface density of the sheet is 2.2-2.4kg / m 2 and is transferred to the drying room, after thickening at 40℃ for 48h, the epoxy resin sheet is obtained, recorded as SMC-3.

[0042] Mold pressing: take the test sample as an example (the mold size is 300 mm*300 mm); the sheet obtained in step two of the example is cut into 290 mm*290 mm after the film is torn off, and is designed to be laminated according to 0.5 mm per layer, for example, a 5 mm thick sample needs to be laminated by 10 layers. The specific pressing process is as follows: the temperature of the press is set to 150 DEG C, and after the temperature is stabilized, the mold is opened, and the outer release agent is sprayed, then the laid sheet is put into the mold cavity as a whole. Close the mold, the initial pressure is 3 MPa, after 45 s of pressure maintaining, the pressure is increased to 10 MPa, and after 30 s, the pressure is increased to 15 MPa, and the pressing time is determined according to 3 min / mm, for example, for a 5 mm sample, after full pressure, after 15 min of heat preservation and pressure maintaining, the mold is opened, the sample is taken out, after edge removal treatment, it is sent for inspection, processing and detection; the sample obtained in this example is recorded as sample X.

[0043] Comparative Example 1

[0044] The difference between this comparative example 1 and the example is that no modified epoxy resin is added.

[0045] Step one, preparation of resin paste: take 100 parts of epoxy resin and add it to a mixing kettle with heat preservation and heating device, start stirring, set the speed to 500 r / min, mix uniformly, then add 10 parts of active epoxy diluent, 10 parts of dicyandiamide, 1.5 parts of internal release agent, 130 parts of filler, 0.3 parts of red paste, 0.5 parts of organic urea accelerator UR300 to the mixing kettle, continue stirring for 30 min, then cool down by water, cool down to below 35 DEG C, then add 3 parts of thickening agent, stir for 10 min, mix uniformly, then pump the resin paste into the resin tank for use;

[0046] Step two, preparation of sheet: adjust the yarn cutter, control the chopped yarn length to be 40 mm, and the yarn running speed to be 5 m / min; lay a PE film under the glue tank, evenly disperse the chopped yarn on the PE film, pass through the glue outlet of the glue tank to make the resin paste evenly disperse on the PE film covered with chopped yarn; control the height of the glue outlet (control by caliper, accuracy 0.03 mm) to ensure the content of the resin paste; then cover another layer of PE film on the resin paste and fiber, then pull into the track roller press with radiation heating device, the length of the roller press is 5 m, the flow speed of the PE film is 1.5 m / min, and the temperature of the heating device is 45 DEG C; after sufficient rolling, the resin paste can be evenly impregnated with the fiber, after the mixture comes out of the roller press, it is pulled by the counter roller, transferred by the guide roller, stretched, then wound or boxed, the surface density of the sheet is 2.2-2.4 kg / m 2 , and is transferred to the drying room, and after 48 h of thickening at 40 DEG C, the epoxy resin sheet is obtained, which is recorded as SMC-4.

[0047] Sample pressing: the sample obtained in Comparative Example 1 cannot be thickened after thickening treatment, and cannot be pressed.

[0048] Comparative Example 2

[0049] Comparative Example 2 is different from Comparative Example 1 in that amino benzoic acid is added on the basis of Comparative Example 1.

[0050] Step 1, preparation of resin paste: take 100 parts of epoxy resin and add it to a mixing kettle with heat preservation and heating device, start stirring, set the speed to 300 r / min, after mixing evenly, add 12 parts of amino benzoic acid, continue stirring for 10 min, then add active epoxy diluent 10 parts, dicyandiamide 10 parts, internal release agent 1.5 parts, filler 130 parts, red paste 0.3 parts, organic urea promoter UR300 0.5 parts, continue stirring for 30 min, then cool down to below 35℃ by water cooling, then add thickening agent 3 parts, stir for 10 min, mix evenly, then pump the resin paste into the resin tank for use;

[0051] Step 2, preparation of sheet: adjust the yarn cutter, control the length of the chopped yarn to be 40 mm, and the yarn running speed to be 5 m / min; lay PE film under the glue tank, and evenly disperse the chopped yarn on the PE film, pass through the glue outlet of the glue tank to make the resin paste evenly disperse on the PE film covered with chopped yarn; control the height of the glue outlet (controlled by caliper, accuracy 0.03 mm) to ensure the content of the resin paste; then add another layer of PE film on the resin paste and fiber, then pull into the track roller compactor with radiation heating device, the length of the roller compactor is 5 m, the flow rate of the PE film is 1.5 m / min, and the temperature of the heating device is 45℃; after sufficient rolling, the resin paste can evenly impregnate the fiber, after the mixture comes out of the roller compactor, it is pulled by the counter roller, transferred by the guide roller, stretched, then wound or boxed, and the surface density of the sheet is 2.2-2.4 kg / m 2 , and transferred to the drying room, and after thickening at 40℃ for 48 h, the epoxy resin sheet SMC-5 is obtained.

[0052] Sample pressing: the sample obtained in Comparative Example 2 cannot be thickened after thickening treatment, and cannot be pressed.

[0053] Comparative Example 3

[0054] The comparative example uses commercially available unsaturated polyester SMC sheet, which is recorded as SMC-6, and the pressing process is as follows: after the film is torn, it is cut into 290mm*290mm, and the layering design is 0.5mm per layer, for example, 10 layers are needed to press a 5mm thick sample. The specific pressing process is as follows: the temperature of the press is set to 150°C, after the temperature is stable, the mold is opened, and the outer release agent is sprayed, then the laid sheet is put into the mold cavity as a whole. Close the mold, the initial pressure is 3MPa, after 45s of pressure maintaining, the pressure is increased to 10MPa, and after 30s, the pressure is increased to 15MPa, and the pressing time is determined according to 3min / mm, for example, for a 5mm sample, after full pressure, after 15min of heat preservation and pressure maintaining, the mold is opened, the sample is taken out, after edge removal treatment, it is sent for inspection, processing and detection; the sample obtained in this example is recorded as sample S.

[0055] Characterization test one

[0056] The material properties and thickening properties of the sheet SMC 1-6 obtained from examples 2-4 and comparative examples 1-3 of the present application were detected, and the test results are shown in Table 1.

[0057] Table 1: sheet properties and thickening performance list

[0058]

[0059] As can be seen from Table 1, the sheet SMC 1-3 prepared by examples 2-4 of the present application can achieve effective thickening, while the sheet prepared by comparative examples 1-2 fails to achieve thickening as expected, which shows that the design and synthesis of modified epoxy resin, i.e. material A, can solve the basic problem of epoxy SMC thickening.

[0060] Specifically, the corresponding sheet SMC 1-3 of embodiments 2-4 of the present application can be smoothly film-torn after thickening for 48h under the condition of 40℃, and SMC-2 and SMC-3 can reach the non-sticky state of ordinary polyester SMC; at the same time, according to the gelation time test results, SMC 1-3 can complete rapid curing at 150℃, and the gelation time is less than 155s, SMC 4-5 cannot measure the gelation time under this condition, and the gelation time of the commercially available polyester SMC is 180s; in addition, in order to monitor the storage period of the epoxy SMC sheet, according to the industry requirements, the gelation time test of the sample stored at room temperature for two weeks is carried out again, and the test results show that the gelation time of SMC 1-3 changes slightly, and the gelation time is shortened by 13s, 9s and 15s respectively, which shows that the performance basically maintains constant, that is, the three sheets can meet the quality requirements of room temperature storage for two weeks; the gelation time of the commercially available sheet SMC-6 is shortened by 54s after two weeks of storage, so the SMC sheet involved in the present application has better stability. The present application realizes the production and preparation of epoxy resin SMC sheet by a simple method, and solves the technical problem that epoxy resin cannot be thickened under controllable conditions.

[0061] Characterization test two

[0062] In order to further illustrate the benefits of the present application, the epoxy SMC sheet and commercially available SMC sheet (which is a commercially available SMC sheet produced by the company itself) involved in the present application are subjected to sample pressing and testing, and the test results are shown in the following table.

[0063] Table 2

[0064]

[0065] From the sample detection result, it can be seen that the epoxy SMC product provided by the application has competitive advantages in main performance index parameters such as mechanical properties and electrical properties compared with traditional polyester SMC products. Among them, the sample M prepared by the application shows the best comprehensive performance, the bending strength, tensile strength and compressive strength of which reach 382 MPa, 305 MPa and 384 MPa respectively, which are increased by 61.2%, 144% and 38.1% respectively compared with the commercially available polyester SMC sample S, in addition, the elastic modulus of the sample M reaches 42.3 GPa, which is much higher than that of sample A (21.3 GPa), sample X (31.8 GPa) and sample S (15.6 GPa), the performance reaches 1 / 5 of steel, at the same time, it meets the relevant requirements and standards of structural design of electrical equipment, engineering vehicles and the like, can meet the material performance design requirements in lightweight, steel replacement and other structural designs, and achieves wide application. At the same time, the epoxy SMC sample involved in the application shows better electrical performance, the breakdown voltage of sample A, sample M and sample X reaches 80 kV, 85 kV and 80 kV respectively, which is greatly improved (60 kV) compared with the polyester SMC sample, and the surface resistance of sample A, sample M and sample X is 2-3 orders of magnitude (10^13-10^14 Ω) higher than that of the polyester SMC sample S; due to the good wetting and hydrophobic properties of the epoxy resin to the glass fiber, the water absorption of the epoxy SMC sample is obviously reduced (from 0.43wt% of the polyester SMC sample to 0.13wt%), more importantly, the breakdown voltage of the sample A, sample M and sample X after immersion in water does not decrease obviously, that is, after being immersed in 90℃ water for 48h, the breakdown voltage of the sample A, sample M and sample X can still reach 70 kV, 80 kV and 70 kV (the breakdown voltage of the polyester SMC sample is only 35 kV), and the insulation properties are greatly retained (the surface resistance can still reach 10^12-10^13 Ω, and the surface resistance of the polyester SMC sample is 10^9 Ω), which shows that the epoxy SMC sample involved in the application can overcome the technical problems that the polyester SMC product is easy to break down and fail in high temperature and high humidity environment.

[0066] In summary, the application provides a design concept and preparation method of an epoxy SMC sheet, the prepared epoxy SMC product shows better mechanical properties and electrical properties, can solve the technical bottleneck problems such as poor high temperature resistance and easy water absorption failure of traditional SMC products, and can provide a material basis for high performance composite material structural design and equipment manufacturing.

[0067] The above only describes the preferred embodiments of the application and should not be used to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A sheet molding compound with an epoxy resin matrix, characterized in that, The raw material components include the following parts by weight: 70-100 parts epoxy resin, 10-20 parts modified epoxy resin, 10-15 parts long-chain active epoxy diluent, 7.5-10 parts latent curing agent, 0.5-1.0 parts accelerator, 1.5-4.5 parts internal release agent, 120-180 parts filler, 0.5-4.5 parts thickener, 0.1-0.5 parts color paste, and 50-80 parts chopped strands; wherein the modified epoxy resin has carboxyl functional groups that react with divalent metal ions; and the modified epoxy resin is an epoxy resin functionally modified with aminobenzoic acid.

2. The sheet molding compound with an epoxy resin matrix according to claim 1, characterized in that: The epoxy resin is one or more of the following: bisphenol A epoxy resin, phenolic epoxy resin, bisphenol F epoxy resin, polyphenolic glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, and glycidyl ester epoxy resin.

3. The sheet molding compound with an epoxy resin matrix according to claim 1, characterized in that: The modified epoxy resin is prepared by the following method: Epoxy resin is added to a reaction vessel, heated to a constant temperature, and stirred under nitrogen protection. Aminobenzoic acid is added, and stirring is continued for a period of time. Then, an organometallic salt catalyst is added, and under nitrogen protection, the constant temperature is maintained until the reaction is complete. After cooling, the modified epoxy resin is obtained.

4. The sheet molding compound with an epoxy resin matrix according to claim 3, characterized in that: The constant temperature is 77-83℃, and the organometallic salt catalyst is selected from one or more of stannous octoate, dibutyltin dilaurate, MB20, BiCAT Zn, zirconium acetylacetonate, nickel acetylacetonate, and rubidium neodecanoate.

5. The sheet molding compound with an epoxy resin matrix according to claim 1, characterized in that: The long-chain active epoxy diluent is one or two of the following: decyl glycidyl ether (AGE), 1,4-butanediol diglycidyl ether (BDDGE), trimethylolpropane triglycidyl ether (TPEG), ethylene glycol diglycidyl ether (EGDE), and 1,6-hexanediol diglycidyl ether (1,6-HDE).

6. The sheet molding compound with an epoxy resin matrix according to claim 1, characterized in that: The latent curing agent is one or two of dicyandiamide and its derivatives.

7. The sheet molding compound with an epoxy resin matrix according to claim 1, characterized in that: The accelerator is one or more of imidazole accelerators, urea derivative accelerators, boron trifluoride-amine complexes, quaternary ammonium salts, and triphenylphosphine complexes; the internal release agent is one or more of lecithin, alkyl phosphates, stearic acid, and stearates; the filler is one or more of aluminum hydroxide, diatomaceous earth, calcium carbonate, calcium sulfate, and talc; and the thickener is one or more of magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, and barium oxide.

8. The sheet molding compound with an epoxy resin matrix according to claim 1, characterized in that: The chopped strands are made from continuous glass fibers by cutting, with a rated length between 30-55 mm. The glass fibers are one of ECT / TM 468A, ECT / TM468G, ECT / TM 468GE, ECT / TM 468T, and ECT / TM 468HS.

9. A method for preparing a sheet molding compound with an epoxy resin matrix as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Add epoxy resin, modified epoxy resin, long-chain active epoxy diluent, latent curing agent, internal release agent, color paste and filler to a mixing kettle equipped with a heat preservation and heating device in proportion. Then add accelerator and thickener in proportion. Mix and stir evenly to obtain resin paste. Step 2: Adjust the size of the cutting blade, cut the epoxy special yarn into short yarn of the rated length, and evenly distribute the short yarn on the PE film. Pass the PE film with the short yarn through the bottom of the glue tank. Step 3: Pump the resin paste into the glue tank, and use a card with a minimum size of 0.3mm to adjust the amount of glue dispensed from the bottom of the glue tank; When the chopped yarn on the PE film passes under the glue tank, open the glue outlet so that the resin paste flows evenly onto the PE film, and use a laminating machine to cover the resin paste with a layer of PE film. Step 4: The material obtained in Step 3 is pulled into a chain-type rolling mill with heating radiation, fully rolled, then boxed or rolled up, and transferred to a drying room for thickening to obtain SMC sheets. Step 5: After peeling off the film from the cured sheet, cut the sheet and calculate the number of layers to be laid according to the sample thickness at 0.5mm / layer SMC. Then, use a molding machine to press it. After pressing, remove the mold and take out the sample. After cooling to room temperature, remove the edges to obtain the epoxy resin matrix sheet molding compound.

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