CN113512273B - OoA molding epoxy resin composition for prepreg by hot-melt method - Google Patents
OoA molding epoxy resin composition for prepreg by hot-melt method Download PDFInfo
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Abstract
The invention discloses an epoxy resin composition for a OoA molding hot-melt prepreg; firstly, preparing modified toughness epoxy resin, blending a toughening agent and at least one liquid difunctional epoxy resin to obtain modified toughness epoxy resin, and adding at least one solid epoxy resin at a certain temperature for melt mixing to regulate viscosity and regulate viscosity to obtain a mixture A; and secondly, passing the solid latent curing agent and the liquid difunctional epoxy resin through a three-roller grinder to enable the curing agent to be uniformly dispersed in the resin to obtain a mixture B, and uniformly mixing and dispersing the mixture A and the mixture B by mechanical stirring to obtain the epoxy resin composition. The resin system has good latency, longer viscosity platform, less volatile content, high resin reactivity and good fracture toughness. The hot-melting prepreg fiber prepared by the resin has good matching property with the resin, and two methods for exhausting OoA molding inclusion gas are provided, so that the prepared composite material has low porosity and good mechanical property.
Description
Technical Field
The invention belongs to the technical field of carbon fiber composite materials, and particularly relates to a rapid-curing high-toughness epoxy resin composition for a OoA molding hot-melt prepreg and a preparation method thereof.
Background
With the progress of China from the large aerospace country to the strong aerospace country, part of carriers are developed from one year to five six times of the prior year, are faced with scientific research production tasks with higher density and higher strength, and are more urgent in production cycle requirements of the carriers, so that the time for preparing the carrier structural parts is shortened, and most of carbon fiber composite structural parts are still subjected to the traditional autoclave and compression molding process. Liquid forming represented by VARI and RTM has great advantages in low-cost manufacture, but the manufactured composite material product has low fiber volume content and poor performance, and can not meet the requirement of the aerospace field on high-performance composite materials.
The existing high-performance resin for aerospace mainly comprises high heat-resistant resin systems such as AG80 tetrafunctional epoxy resin, cyanate resin and the like, and the curing speed of the resin system is low, so that the curing efficiency cannot be improved; the hot-melt prepreg resin system for autoclave molding and compression molding is mainly toughened, tackified and modified by thermoplastic resins such as polyether sulfone (PES), polyether ether ketone (PEEK) and the like, but the thermoplastic resins have the disadvantages of large molecular weight, rapid rising of viscosity of the resin system in the processing process, deterioration of manufacturability and spreadability of the prepreg, deterioration of wettability of the resin system to fiber bundles, and influence on matching of the resin and the fibers while toughening.
The prior patent with the patent number of CN201610365714 discloses a high-temperature-curing-resistant epoxy resin carbon fiber prepreg. The invention uses the epoxy resin with four functional groups, the obtained epoxy resin composition has higher viscosity and higher reactivity, and the requirements of OoA molding process viscosity and gel time are hardly met.
Disclosure of Invention
The invention aims at the defects of higher cost, low molding efficiency, insufficient toughness of a resin system and the like of the existing autoclave molding and compression molding process; in order to improve the molding quality of the composite structural member, reduce the molding efficiency and the process cost, prepare a high-performance resin system, widen the application field of the composite material, and provide the rapid-curing high-toughness epoxy resin composition for the OoA molding hot-melt prepreg.
In order to solve the problems, the invention adopts the following technical scheme:
in a first aspect, the invention relates to a fast-curing high-toughness epoxy resin composition for OoA molded hot-melt prepreg, which comprises the following components in parts by weight: 10-30 parts of liquid difunctional epoxy resin, 50-70 parts of solid difunctional epoxy resin, 5-15 parts of amine curing agent, 10-20 parts of toughening agent and 0.5-2 parts of accelerator.
Further, the liquid difunctional epoxy resin is any one or a combination of a plurality of bisphenol F type epoxy resin, E51 epoxy resin and E44 epoxy resin. Three liquid trifunctional epoxy resins with different viscosities are selected in the invention, the viscosity and viscosity of the prepreg by a hot melting method are finely adjusted, and one resin plays a role in dispersing powdery amine curing agents.
Further, the solid difunctional epoxy resin is any one or a combination of a plurality of E20 epoxy resin, 704 epoxy resin and oxazolidone modified epoxy resin. The solid difunctional epoxy resin is added to mainly increase the viscosity of a normal-temperature resin system, the melting point of the solid difunctional epoxy resin is lower, the resin system can reach lower viscosity at a lower temperature, and the viscosity platform area is longer. The addition of the solid epoxy resin also increases the film forming property of the resin system, and is suitable for preparing the prepreg by the hot melting method.
Further, the amine curing agent is any one or the combination of a plurality of dicyandiamide, 4' -diaminodiphenyl sulfone, m-phenylenediamine and biguanide compounds. The curing agent adopts a grinding mode to increase the dispersion uniformity of the powdery curing agent, and no heat release concentration point or stress concentration point is generated. The dicyandiamide curing agent has high curing speed, is suitable for a rapid curing system, has long storage period for preparing the prepreg by a hot melting method, and belongs to a latent curing agent.
Further, the toughening agent is one or a combination of two of polyurethane modified epoxy resin and liquid epoxy cage-type silsesquioxane in any proportion. The toughening agent used in the invention is not a conventional toughening agent, and the toughening agent selected in the hot-melt prepreg is generally thermoplastic resin, but the thermoplastic resin has the disadvantages of large molecular weight, rapid increase of viscosity of a resin system in the processing process, deterioration of manufacturability and spreadability of the prepreg, and deterioration of wettability of the resin system to fiber bundles. The two toughening agents used in the invention are both toughening agents of modified epoxy resin, have good compatibility with matrix resin, do not generate phase separation and uneven mixing effects, and achieve the purpose of toughening while keeping the viscosity of the system improved.
Further, the viscosity of the polyurethane modified epoxy resin is 40000-60000 mPa.s, and the epoxy equivalent is 210-250g/eq. The number of epoxy groups in the liquid epoxy cage-type silsesquioxane structure is 2-4, and the volatile component is less than 0.5%. The polyurethane modified epoxy resin with the performance is selected, the final viscosity of the resin system is improved from the viscosity, the epoxy equivalent is similar to that of the main resin, the number of the epoxy groups can increase the crosslinking density, and the heat resistance of the resin system is not reduced.
Further, the accelerator is one or the combination of two of organic urea accelerators. The accelerator selected by the invention can reduce the curing temperature of the amine curing agent and improve the curing rate.
Further, the epoxy resin composition has a normal temperature viscosity of 3000-6000 Pa.s and a viscosity-temperature rheological curve with a minimum viscosity of 1000-3000 mPa.s. The epoxy resin composition has a sufficiently high viscosity at normal temperature, a sufficiently low viscosity at high temperature, and a long viscosity plateau. The normal temperature resin is too viscous, so that a large amount of air is easily wrapped in the laying process, the exhaust channel is blocked, and the prepreg is poor in laying property when the viscosity is high. In the heating and curing process, the resin has enough fluidity to fully infiltrate the fiber, the lowest viscosity is suitable, the lowest viscosity is too low, the resin flows too fast, the air guide channel is blocked by the resin before the mixed gas is effectively led out, and if the lowest viscosity is too high, the resin has insufficient fluidity at a limited atmosphere pressure, the fiber is not fully infiltrated, and the porosity of the composite material is increased. In addition, the resin should be maintained in a suitable viscosity region for a period of time to ensure sufficient time for the occluded gases and volatiles to escape.
Further, the lowest viscosity plateau of the viscosity-temperature curve of the epoxy resin composition is longer. Therefore, the gel time is longer, the lowest viscosity platform area can still be kept below 8000 mPas, the fiber can be fully soaked in the low viscosity time, and the pores in the composite material are reduced.
In a second aspect, the invention also relates to a preparation method of the fast-curing high-toughness epoxy resin composition for OoA molding hot-melt prepreg, which comprises the following steps:
s1, mixing 5-15 parts of liquid difunctional epoxy resin, 50-70 parts of solid difunctional epoxy resin and 10-20 parts of toughening agent, heating and melting at 105-115 ℃ and stirring for 30-60min to obtain a transparent and uniform mixture A;
s2, mixing, stirring and grinding 5-20 parts of amine curing agent, 0.5-2 parts of accelerator and 5-15 parts of liquid difunctional epoxy resin to obtain a mixture B with uniformly dispersed amine curing agent;
s3, reducing the temperature of the materials in the oil bath to 80-90 ℃, adding the mixture B into the mixture A, stirring and mixing for 8-10min, and obtaining the epoxy resin composition.
Further, in the grinding in step S2, one of the liquid epoxy resins is ground as a master batch. The amine curing agent can be uniformly dispersed in a composition system when a master batch of the liquid difunctional epoxy resin is subjected to a three-roller grinder, and particle agglomeration phenomenon can not occur, so that the prepared resin casting body has no stress concentration point and has excellent performance compared with unground performance.
Further, the grinding was performed using a three-roll grinder, and the grinding was performed for not less than 3 times.
Wherein the stirring speed of stirring and mixing is 1000-2000r/min, and the stirring time is 8-10min. The amine curing agent can be fully and uniformly dispersed, and the quick-curing high-toughness epoxy resin composition for the OoA molding hot-melt prepreg is obtained after full mixing.
Further, the liquid difunctional epoxy resin in step S2 is bisphenol F type epoxy resin.
In a third aspect, the present invention further relates to an application of the epoxy resin composition in OoA molding, where the epoxy resin composition is used in combination with fibers to form a reserved air channel in the molding process, and the method for constructing the reserved air channel adopts a first method or a second method:
the method comprises the following steps: preparing a resin adhesive film, and preparing a semi-impregnation hot-melting prepreg by adopting an upper and lower double-sided film coating method, so that carbon fibers cannot be completely impregnated, and an un-impregnated area is formed in the middle, wherein a reserved air passage is formed in the un-impregnated area in the forming process;
the second method is as follows: preparing a resin adhesive film, and preparing a fully-impregnated prepreg by fully soaking carbon fibers by adopting an upper and lower double-sided film coating method; in the forming process, a nanofiber membrane is covered between resin adhesive membrane layers during layering, so that reserved air passages are formed between the layers.
In the first method, the temperature for preparing the resin adhesive film is 65-75 ℃. When the adhesive film is laminated on the upper and lower surfaces of the fiber, the temperatures of the roller 1, the roller 2 and the roller 3 are respectively 80 ℃, 75 ℃ and 75 ℃.
In the second method, the temperature for preparing the resin adhesive film is 65-75 ℃. When the adhesive film is laminated on the upper and lower surfaces of the fiber, the temperatures of the roller 1, the roller 2 and the roller 3 are 105 ℃, 100 ℃ and 100 ℃ respectively.
In the first method, the compounding temperature of the semi-impregnated prepreg is 25 ℃ lower than that of the fully-impregnated prepreg. In the second method, the fully-impregnated prepreg is prepared, and in the layering process, an interlayer nanofiber membrane covering method is adopted, so that air passages are reserved between layers, the purpose of exhausting is achieved, and the interlayer toughening effect is achieved.
Compared with the existing autoclave molding and compression molding, the epoxy resin composition suitable for OoA molding process has the beneficial effects that:
1) The epoxy resin composition suitable for OoA molding process not only increases the toughness of a resin system, improves the molding quality of a composite structural member and the molding efficiency and reduces the process cost, but also shortens the curing time of the resin, prepares a high-performance resin system, widens the application field of the composite material, and is particularly suitable for OoA molding.
2) The solid difunctional epoxy resin used in the epoxy resin composition suitable for the OoA molding process can effectively adjust the viscosity of the composition to achieve the requirement of OoA molding epoxy resin.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a schematic diagram of a OoA semi-impregnated prepreg;
FIG. 2 is a schematic illustration of a fully impregnated prepreg layup;
wherein, 1, a resin adhesive film, 2, carbon fiber, 3, a nanofiber film.
Detailed Description
The present invention will be described in detail with reference to examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that several modifications and improvements can be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
In the following examples, E44 epoxy resin (trade name E44) was selected from the group consisting of tin-free resin factories, bisphenol F epoxy resin (trade name NPEF-170), E20 epoxy resin (trade name NPES-901), novolac epoxy resin (trade name NPCN-704), E51 epoxy resin (trade name E51) was selected from the group consisting of Shanz advanced materials institute, liquid epoxy cage silsesquioxane (trade name EP-POSS) was selected from the group consisting of Shanz Sizhi New materials Co., ltd., 4' -diaminodiphenyl sulfone was selected from Shanghai Sanai Sanyi reagent Co., ltd., polyurethane modified epoxy resin (trade name EPU-133), dicyandiamide (trade name DDH 0) was selected from the group consisting of Shanghai complex high material Co., organic urea accelerators (German UR300, UR 500). The liquid difunctional epoxy resin, the solid difunctional epoxy resin, the amine curing agent and the toughening agent used in the present invention are not limited to the above-listed ones.
Example 1
Mixing 5 parts of E51 epoxy resin, 44 parts of E20 epoxy resin, 21 parts of 704 epoxy resin and 20 parts of polyurethane modified epoxy resin, and heating, melting and stirring for 30min in an oil bath at 110 ℃ to obtain a transparent and uniform mixture A;
mixing and stirring 6 parts of dicyandiamide curing agent, 1 part of UR300 accelerator and 10 parts of bisphenol F epoxy resin, and passing through a three-roller grinder for at least 3 times to obtain a mixture B with uniformly dispersed dicyandiamide curing agent;
the temperature of the material in the oil bath pot is reduced to 80 ℃, the mixture B is added into the mixture A to be stirred and mixed at a high speed (preferably, the stirring speed is 1000 r/min), the stirring time is 8min, the solid amine curing agent can be fully and uniformly dispersed, the epoxy resin composition suitable for the OoA molding process for the hot-melt prepreg is obtained after the full mixing, the defoaming is carried out for 30min at 110 ℃, and then the temperature is increased to 160 ℃ to be cured for 30min, so that the cured epoxy resin composition is obtained.
Example 2
Mixing 10 parts of E51 epoxy resin, 40 parts of E20 epoxy resin, 20 parts of 704 epoxy resin and 20 parts of polyurethane modified epoxy resin, and heating, melting and stirring for 30min in an oil bath at 110 ℃ to obtain a transparent and uniform mixture A;
mixing 7 parts of dicyandiamide curing agent, 1 part of UR300 accelerator and 10 parts of bisphenol F epoxy resin, and stirring, and passing through a three-roller grinder for at least 3 times to obtain a mixture B with uniformly dispersed dicyandiamide curing agent;
the temperature of the material in the oil bath pot is reduced to 80 ℃, the mixture B is added into the mixture A to be stirred and mixed at a high speed (preferably, the stirring speed is 2000 r/min) for 10min, so that the solid amine curing agent can be fully and uniformly dispersed, the epoxy resin composition suitable for the OoA molding process for the hot-melt prepreg is obtained after the full mixing, the defoaming is carried out for 30min at 110 ℃, and then the temperature is increased to 160 ℃ to be cured for 30min, so that the cured epoxy resin composition is obtained.
Example 3
Mixing 15 parts of E51 epoxy resin, 37 parts of E20 epoxy resin, 18 parts of 704 epoxy resin and 20 parts of polyurethane modified epoxy resin, and heating, melting and stirring for 30min in an oil bath at 110 ℃ to obtain a transparent and uniform mixture A;
mixing 8 parts of dicyandiamide curing agent, 1 part of UR300 accelerator and 10 parts of bisphenol F epoxy resin, and stirring, and passing through a three-roller grinder for at least 3 times to obtain a mixture B with uniformly dispersed dicyandiamide curing agent;
the temperature of the material in the oil bath pot is reduced to 80 ℃, the mixture B is added into the mixture A to be stirred and mixed at a high speed (preferably, the stirring speed is 1500 r/min), the stirring time is 9min, the solid amine curing agent can be fully and uniformly dispersed, the epoxy resin composition suitable for the OoA molding process for the hot-melt prepreg is obtained after the full mixing, the defoaming is carried out for 30min at 110 ℃, and then the temperature is increased to 160 ℃ to be cured for 30min, so that the cured epoxy resin composition is obtained.
Example 4
Mixing 15 parts of E51 epoxy resin, 44 parts of E20 epoxy resin, 21 parts of 704 epoxy resin and 10 parts of polyurethane modified epoxy resin, and heating, melting and stirring for 30min in an oil bath at 110 ℃ to obtain a transparent and uniform mixture A;
mixing 10 parts of dicyandiamide curing agent, 1 part of UR300 accelerator and 10 parts of bisphenol F epoxy resin, and stirring, and passing through a three-roller grinder for at least 3 times to obtain a mixture B with uniformly dispersed dicyandiamide curing agent;
the temperature of the material in the oil bath pot is reduced to 80 ℃, the mixture B is added into the mixture A to be stirred and mixed at a high speed (preferably, the stirring speed is 2000 r/min), the stirring time is 8min, the solid amine curing agent can be fully and uniformly dispersed, the epoxy resin composition suitable for the OoA molding process for the hot-melt prepreg is obtained after the full mixing, the defoaming is carried out for 30min at 110 ℃, and then the temperature is increased to 160 ℃ to be cured for 30min, so that the cured epoxy resin composition is obtained.
Example 5
Mixing 5 parts of E51 epoxy resin, 44 parts of E20 epoxy resin, 21 parts of 704 epoxy resin and 20 parts of liquid epoxy cage-type silsesquioxane, and heating, melting and stirring for 30min in an oil bath at 110 ℃ to obtain a transparent and uniform mixture A;
mixing and stirring 6 parts of dicyandiamide curing agent, 1 part of UR300 accelerator and 10 parts of bisphenol F epoxy resin, and passing through a three-roller grinder for at least 3 times to obtain a mixture B with uniformly dispersed dicyandiamide curing agent;
the temperature of the material in the oil bath pot is reduced to 80 ℃, the mixture B is added into the mixture A to be stirred and mixed at a high speed (preferably, the stirring speed is 1000 r/min), the stirring time is 8min, the solid amine curing agent can be fully and uniformly dispersed, the epoxy resin composition suitable for the OoA molding process for the hot-melt prepreg is obtained after the full mixing, the defoaming is carried out for 30min at 110 ℃, and then the temperature is increased to 160 ℃ to be cured for 30min, so that the cured epoxy resin composition is obtained.
Example 6
Mixing 5 parts of E51 epoxy resin, 44 parts of E20 epoxy resin, 21 parts of 704 epoxy resin, 10 parts of polyurethane modified epoxy resin and 10 parts of liquid epoxy cage-type silsesquioxane, and heating, melting and stirring for 30min in an oil bath pot at 110 ℃ to obtain a transparent and uniform mixture A;
mixing and stirring 6 parts of dicyandiamide curing agent, 1 part of UR300 accelerator and 10 parts of bisphenol F epoxy resin, and passing through a three-roller grinder for at least 3 times to obtain a mixture B with uniformly dispersed dicyandiamide curing agent;
the temperature of the material in the oil bath pot is reduced to 80 ℃, the mixture B is added into the mixture A to be stirred and mixed at a high speed (preferably, the stirring speed is 1000 r/min), the stirring time is 8min, the solid amine curing agent can be fully and uniformly dispersed, the epoxy resin composition suitable for the OoA molding process for the hot-melt prepreg is obtained after the full mixing, the defoaming is carried out for 30min at 110 ℃, and then the temperature is increased to 160 ℃ to be cured for 30min, so that the cured epoxy resin composition is obtained.
Example 7
Mixing 5 parts of E51 epoxy resin, 44 parts of E20 epoxy resin, 21 parts of 704 epoxy resin and 20 parts of polyurethane modified epoxy resin, and heating, melting and stirring for 30min in an oil bath at 110 ℃ to obtain a transparent and uniform mixture A;
mixing and stirring 6 parts of dicyandiamide curing agent, 1 part of UR500 accelerator and 10 parts of bisphenol F epoxy resin, and passing through a three-roller grinder for at least 3 times to obtain a mixture B with uniformly dispersed dicyandiamide curing agent;
the temperature of the material in the oil bath pot is reduced to 80 ℃, the mixture B is added into the mixture A to be stirred and mixed at a high speed (preferably, the stirring speed is 1000 r/min), the stirring time is 8min, the solid amine curing agent can be fully and uniformly dispersed, the epoxy resin composition suitable for the OoA molding process for the hot-melt prepreg is obtained after the full mixing, the defoaming is carried out for 30min at 110 ℃, and then the temperature is increased to 160 ℃ to be cured for 30min, so that the cured epoxy resin composition is obtained.
Example 8
Mixing 5 parts of E51 epoxy resin, 44 parts of E20 epoxy resin, 21 parts of 704 epoxy resin and 20 parts of polyurethane modified epoxy resin, and heating, melting and stirring for 30min in an oil bath at 110 ℃ to obtain a transparent and uniform mixture A;
mixing 5 parts of dicyandiamide curing agent, 10 parts of 4,4' -diaminodiphenyl sulfone 1 and 1 part of UR300 accelerator with 10 parts of bisphenol F epoxy resin, stirring, and grinding for at least 3 times by a three-roller grinder to obtain a mixture B with uniformly dispersed dicyandiamide curing agent;
the temperature of the material in the oil bath pot is reduced to 80 ℃, the mixture B is added into the mixture A to be stirred and mixed at a high speed (preferably, the stirring speed is 1000 r/min), the stirring time is 8min, the solid amine curing agent can be fully and uniformly dispersed, the epoxy resin composition suitable for the OoA molding process for the hot-melt prepreg is obtained after the full mixing, the defoaming is carried out for 30min at 110 ℃, and then the temperature is increased to 160 ℃ to be cured for 30min, so that the cured epoxy resin composition is obtained.
Testing the viscosity-temperature curve of the epoxy resin composition before curing by adopting a rotary rheometer; the fracture toughness of the epoxy resin composition was tested according to ASTM-5045 standard; the tensile properties of the epoxy resin composition were tested according to GB/T2567-2008 standard; the impact strength of the epoxy resin composition was tested according to GB/T1843-2008 standard; the performance parameters of the epoxy resin compositions prepared in examples 1-8 are shown in Table 1.
TABLE 1
As can be seen from the comparison of the performance parameters of the epoxy resin compositions of examples 1 to 8 in Table 1, the epoxy resin composition of example 1 has the best performance. The epoxy resin composition suitable for OoA molding has low viscosity, long temperature rising process minimum viscosity platform area (long gel time), good resin mechanical property and good interlayer fracture toughness. Therefore, the requirements of the OoA molding epoxy resin are best met in the embodiment 1 and the embodiment 6, and the embodiment 1 has the best effect in terms of engineering manufacturability because the embodiment 6 adopts two toughening agents to cooperatively toughen, and the manufacturability is not as simple as the embodiment 1.
Example 9
The resin system in any one of examples 1-8 is adopted, a resin film is prepared by using a resin film coating machine, the film coating temperature is 65-75 ℃, a hot-melt prepreg is prepared by a two-step method, the semi-impregnated prepreg film and fiber compounding temperature roller 1, roller 2 and roller 3 are respectively 80 ℃, 75 ℃, the fully-impregnated prepreg film and fiber compounding temperature roller 1, roller 2 and roller 3 are respectively 105 ℃, 100 ℃ and 100 ℃, the compounding temperature of the semi-impregnated prepreg film and the fiber compounding temperature is lower than that of the fully-impregnated prepreg by 25 ℃ relative to the fully-impregnated prepreg, so that the fiber is not fully soaked, and an un-impregnated area exists in the middle, wherein the carbon fiber 2 is fully impregnated by the resin film 1, and the un-impregnated area serves as an air passage for inclusion gas in the forming process, which is a method for achieving OoA forming in the process of preparing the hot-melt prepreg, and is convenient for discharging the inclusion gas.
Example 10
By adopting the fully-impregnated prepreg prepared in the embodiment 9, 45gsm of nanofiber membrane is paved between the prepreg layers by a hot-melting method, as shown in fig. 2, a certain micro gap is formed between the resin adhesive film layers impregnated with carbon fibers 2 by the nanofiber membrane 3 to serve as an air passage, and the nanofiber membrane is paved between the layers, so that the interlayer toughening effect is better than the toughening effect of the resin of the toughened body for the composite laminated plate, and the damage resistance tolerance between the composite material layers is improved.
Comparative example 1
This comparative example provides a fast curing high toughness epoxy resin composition, with the specific steps being substantially the same as in example 1, except that: the liquid difunctional epoxy resin is AG80 tetrafunctional epoxy resin and AFG90 trifunctional epoxy resin; the solid difunctional epoxy resin is oxazolidone modified epoxy resin, the obtained epoxy resin composition has higher viscosity and higher reactivity, and the requirements of OoA molding process viscosity and gel time are hardly met.
TABLE 2
| Minimum viscosity (mPa. S) | Gel time at 120 DEG C | |
| Example 1 | 1355 | 18′50″ |
| Comparative example 1 | 3400 | 7′30″ |
Comparative example 2
This comparative example provides a fast curing high toughness epoxy resin composition, with the specific steps being substantially the same as in example 1, except that: the toughening agent is carboxyl-terminated nitrile rubber.
The resin composition has high viscosity and difficult bubble removal, and the toughening agent has obvious toughening effect, but the heat resistance of the composition is obviously reduced, the mechanical property is reduced to some extent, and the process performance requirement cannot be met. The reason for not adopting the toughening agent is that the mechanical property is reduced, the reduction range is larger, and the heat resistance is reduced.
TABLE 3 Table 3
Comparative example 3
This comparative example provides a fast curing high toughness epoxy resin composition, with the specific steps being substantially the same as in example 1, except that: the toughening agent is polyacrylate.
The reason for not adopting the toughening agent is that the acrylic polymer is small molecules, unreacted small molecules can escape under vacuum, and the material with large vacuum escape amount is not adopted in general aerospace, and the glass transition temperature is lower.
Comparative example 4
This comparative example provides a fast curing high toughness epoxy resin composition, with the specific steps being substantially the same as in example 1, except that: the toughening agent is polyether sulfone thermoplastic resin.
Thermoplastic resins have the disadvantage that the molecular weight is high, the viscosity of the resin system increases sharply during processing, the manufacturability and spreadability of the prepreg deteriorate, and the wettability of the resin system to the fiber bundles also deteriorates, so that the disadvantage is obvious.
Comparative example 5
This comparative example provides a fast curing high toughness epoxy resin composition, with the specific steps being substantially the same as in example 1, except that: the polyurethane modified epoxy resin adopted by the toughening agent has the viscosity of 5000-11000 mPa.s at 25 ℃ and the epoxy equivalent of 240-280g/eq, the toughening effect of the polyurethane modified epoxy resin is poorer than that of the embodiment 1, and the viscosity of the resin is lower, so that the viscosity of the composition is higher and lower, and the requirement of the viscosity of the resin for preparing the prepreg by a hot melting method is not met.
TABLE 4 Table 4
| Fracture toughness (MPa/m) 1/2 ) | Composition room temperature viscosity (Pa.s) | |
| Example 1 | 4.1 | 3200 |
| Comparative example 5 | 2.4 | 2300 |
Comparative example 6
This comparative example provides a fast curing high toughness epoxy resin composition, with the specific steps being substantially the same as in example 1, except that: the liquid epoxy cage-type silsesquioxane is selected as the toughening agent, the number of epoxy groups in the structure of the toughening agent is 5, and the toughening effect of the composition is not obvious.
TABLE 5
Comparative examples 7 to 10
Comparative examples 7 to 10 were in one-to-one correspondence with examples 1 to 4, respectively, and the components and steps were substantially the same, except that one of the amine powder curing agents in comparative examples 7 to 10, which was not a liquid difunctional epoxy resin, was used as the master batch was dispersed through a three-roll mill.
Compared with a three-roller mill, the amine powder curing agent is prepared by dispersing master batch, stress concentration points are easy to appear on fracture surfaces of a stretched resin casting body, the stretching performance is poor, the properties of the two are shown in table 2, macroscopic particles are easy to appear in the process of preparing a prepreg coating film, and the mechanical properties of the resin and the composite material are influenced.
TABLE 6
The foregoing describes specific embodiments of the present invention. It is to be understood that the invention is not limited to the particular embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the claims without affecting the spirit of the invention.
Claims (6)
1. An epoxy resin composition for OoA molding hot-melt prepreg is characterized by comprising the following components in parts by weight:
10-30 parts of liquid difunctional epoxy resin;
50-70 parts of solid difunctional epoxy resin;
5-15 parts of an amine curing agent;
10-20 parts of toughening agent;
0.5-2 parts of promoter;
the liquid difunctional epoxy resin is a combination of bisphenol F type epoxy resin and E51 epoxy resin;
the solid difunctional epoxy resin is a combination of E20 epoxy resin and 704 epoxy resin;
the epoxy resin composition has normal temperature viscosity of 3000-6000 Pa.s and viscosity-temperature rheological curve minimum viscosity of 1000-3000 mPa.s;
the toughening agent is one or a combination of two of polyurethane modified epoxy resin and liquid epoxy cage-type silsesquioxane in any proportion; the viscosity of the polyurethane modified epoxy resin is 40000-60000 mPa.s, and the epoxy equivalent is 210-250g/eq; the number of epoxy groups in the liquid epoxy cage-type silsesquioxane structure is 2-4, and the volatile component is less than 0.5%.
2. The epoxy resin composition for a OoA molded hot-melt prepreg of claim 1, wherein the amine curing agent is any one or a combination of more of dicyandiamide, 4' -diaminodiphenyl sulfone, m-phenylenediamine and biguanide compounds.
3. An epoxy resin composition for a OoA molded hot melt prepreg as claimed in claim 1, wherein said accelerator is one or a combination of two of organic urea accelerators.
4. A method of preparing the epoxy resin composition of claim 1, comprising the steps of:
s1, mixing 5-15 parts of liquid difunctional epoxy resin, 50-70 parts of solid difunctional epoxy resin and 10-20 parts of toughening agent, heating and melting at 105-115 ℃ and stirring for 30-60min to obtain a transparent and uniform mixture A;
s2, mixing, stirring and grinding 5-15 parts of amine curing agent, 0.5-2 parts of accelerator and 5-15 parts of liquid difunctional epoxy resin to obtain a mixture B with uniformly dispersed amine curing agent;
s3, reducing the temperature of the mixture A in the step S1 to 80-90 ℃, adding the mixture B into the mixture A, stirring and mixing for 8-10min, and obtaining the epoxy resin composition.
5. The method of producing an epoxy resin composition according to claim 4, wherein one of the liquid epoxy resins is ground as a master batch in step S2.
6. Use of the epoxy resin composition of claim 1 in OoA molding, wherein the resin is used in combination with fibers to form a pre-reserved air channel during molding; the construction method of the reserved air passage adopts a first method or a second method:
the method comprises the following steps: preparing a resin adhesive film, and preparing a semi-impregnation hot-melting prepreg by adopting an upper and lower double-sided film coating method, so that carbon fibers cannot be completely impregnated, and an un-impregnated area is formed in the middle, wherein a reserved air passage is formed in the un-impregnated area in the forming process;
the second method is as follows: preparing a resin adhesive film, and preparing a fully-impregnated prepreg by fully soaking carbon fibers by adopting an upper and lower double-sided film coating method; in the forming process, a nanofiber membrane is covered between resin adhesive membrane layers during layering, so that reserved air passages are formed between the layers.
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| CN114230973B (en) * | 2021-11-29 | 2023-05-12 | 航天特种材料及工艺技术研究所 | Epoxy resin composition for OOA process and preparation method of composite material of epoxy resin composition |
| CN114410067A (en) * | 2022-01-28 | 2022-04-29 | 山东非金属材料研究所 | Epoxy resin composition for hollow thin-wall variable-cross-section high-bearing structure, prepreg and preparation method of prepreg |
| CN116218146A (en) * | 2022-12-20 | 2023-06-06 | 哈尔滨玻璃钢研究院有限公司 | Preparation method of composite toughening agent modified medium-temperature cured epoxy resin prepreg |
| CN115975346B (en) * | 2023-03-13 | 2023-07-28 | 北京天仁道和新材料有限公司 | Epoxy resin premix for OOA cured prepreg and preparation method thereof |
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