WO2012151250A1

WO2012151250A1 - Composite resin compositions

Info

Publication number: WO2012151250A1
Application number: PCT/US2012/036074
Authority: WO
Inventors: Lloyd H. Hihara; Atul Tiwari
Original assignee: University Of Hawaii
Priority date: 2011-05-03
Filing date: 2012-05-02
Publication date: 2012-11-08

Abstract

Disclosed are compositions that include an epoxy resin, a phenolic resin, a solvent, and a filler. These compositions may be used to produce prepreg materials, which materials remain in condition for layup processing after extended storage at ambient conditions.

Description

COMPOSITE RESIN COMPOSITIONS

RELATED APPLICATION

[0001] This application claims priority to United States patent application 61/481,774, "Resin Composition," filed on May 3, 2011, the entirety of which is incorporated herein for any and all purposes.

STATEMENT OF GOVERNMENT RIGHTS

[0002] This invention was made with government support under grant number W1SQKN-07-C-002, awarded by the U.S. Army, TACOM/ARDEC. The government has certain rights in this invention.

TECHNICAL FIELD

[0003] The present application relates to the field of resin materials and to the field of nanoscale filler materials.

BACKGROUND

[0004] Resin compositions utilized to produce prepregs are utilized in a variety of industries including military, aerospace, appliances, business equipment, construction, consumer products, marine products, land transportation, and others. One attribute of prepregs is their ability to replace conventional light-weight, high-strength metal or wood structures with an even lighter-weight, higher-strength alternative. Nevertheless, improving the manufacturing technology for resin compositions for prepregs presents challenges in the field of composites.

[0005] Prepregs are fabricated through the combination of a reinforced fiber fabric and a resin composition. This combination forms a prepreg after the appropriate curing procedures.

[0006] For many applications associated with reinforced fiber prepreg technology, the prepreg is suitably tacky so as to facilitate application to composite materials. The value of a prepreg would be enhanced if the prepregs could remain tacky for an extended period of time so that the prepregs would not need to be made on-site and so that the prepregs can be produced or purchased in large quantities to reduce costs.

[0007] Currently, the tackiness of a prepreg containing an epoxy resin is facilitated by the use of a hardener/curing agent, such as amine. With the presence of such agents, however, it is preferable that the prepregs be stored at a temperature equal to or below freezing temperature.

Storage of prepregs at such temperatures, however, increases costs to the user, and freezer storage increases the transportation costs of the prepregs because the prepregs either have to be transported at freezing temperatures or utilized shortly after removal from the freezer.

[0008] Some epoxy resin formulated prepregs have been designed for storage at room temperatures, but such formulations have short shelf-lives. A short shelf-life limits the end use of the prepregs and could potentially increase costs. The short shelf-life requires that the end-user know the application date of the prepregs before purchasing/producing a prepreg so as to ensure that the prepreg is used before its date of expiration. This short shelf-life increases the likelihood that stored prepregs may not be used before they lose the tackiness needed to facilitate application. The use of a hardener/curing agent in epoxy resin compositions increases storage and transportation costs and decreases the overall shelf-life of formed prepregs stored at room temperature. Accordingly, there is a need in the art for resins and prepregs capable of extended shelf lives.

SUMMARY

[0009] In meeting the described challenges, the present disclosure provides compositions, the compositions comprising an epoxy resin; a phenolic resin; a solvent; and a filler.

[0010] Also provided are prepregs, the prepregs comprising a fibrous substrate, the fibrous substrate being impregnated with a resin admixture, the resin admixture comprising an epoxy resin, a phenolic resin, a solvent; and a filler.

[0011] Further provided are methods, the methods comprising contacting an epoxy resin, a phenolic resin, a solvent, and a filler to form a primary admixture.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following figures, which form a part of this application, are illustrative of systems and methods described below and are not meant to limit the scope of the disclosure in any manner, which scope shall be based on the claims appended hereto.

[0013] The summary, as well as the following detailed description, is further understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there are shown in the drawings exemplary embodiments of the disclosure; however, the disclosure is not limited to the specific methods, compositions, and devices disclosed. In addition, the drawings are not necessarily drawn to scale. In the drawings [0014] FIG. 1 illustrates a graph of the percent of transmittance at increasing wavelengths for three differently formulated reaction inducted macromolecular matrix

("RIMM") materials according to the present disclosure;

[0015] FIG. 2 illustrates a graph of the percent of transmittance at increasing wavelength for three differently formulated prepregs; and

[0016] FIG. 3 presents three scanning electron microscope images of a cross-section of a composite formed from a prepreg made from a composition according to the present disclosure composition.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0017] The present disclosure may be understood more readily by reference to the following detailed description taken in connection with the accompanying figures and examples, which form a part of this disclosure. It is to be understood that this disclosure is not limited to the specific devices, methods, applications, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claims. Also, as used in the specification including the appended claims, the singular forms a, an, and the include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise.

[0018] The term "plurality," as used herein, means more than one. When a range of values is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about" it will be understood that the particular value forms another embodiment. All ranges are inclusive and combinable. Any and all documents cited herein are incorporated herein by reference in their entireties for any and all purposes.

[0019] In a first embodiment, the present disclosure provides compositions. These compositions suitably include an epoxy resin; a phenolic resin; a solvent; and a filler.

[0020] A variety of epoxy resins are suitable for use in the disclosed compositions. As some examples, epoxy resins that include a bifunctional epoxy resin, a polyfunctional epoxy resin, a glycidylamine epoxy resin, a glycidylether epoxy resin, a brominated epoxy resin, are all suitable, as are combinations thereos. Where the epoxy resin is a bifunctional epoxy resin, the resin suitably includes a bisphenol A epoxy resin, a bisphenol F epoxy resin, a biphenyl epoxy resin, a dicyclopentadiene epoxy resin, and the like, as well as combinations of the foregoing. [0021] In some cases, the epoxy resin may be a polyfunctional epoxy resin. Some such suitable resins include phenol novolac epoxy resins, resol epoxy resins, and the like. When a glycidylamine epoxy resin is present in the compositions, such a resin suitably includes a tetraglycidyldiaminodiphenylmethane, a triglycidylaminophenol, a tetraglycidyldiamine, and the like, as well as combinations of the foregoing. When a glycidylether epoxy resin is present, such resin may include a tetrakis(glycidyloxyphenyl)ethane, a tris(glycidyloxymethane), and the like, as well as combinations thereof.

[0022] A variety of phenolic resins are suitable for use in the disclosed compositions. Phenol formaldehyde resins are considered especially suitable. Other solvents capable of solvating the epoxy resin and the phenolic resin are considered suitable. Resins in novolac and resol forms are considered especially suitable. The solvent may be present at from about 0.1 wt% to about 99 wt% of the composition or even from about 10 wt% to about 50 wt% of the composition, or even from about 15 wt% to about 25 wt% of the composition. The amount of solvent present in a given embodiment will be determined by the user of ordinary skill in the art without undue experimentation.

[0023] A variety of solvents may be used in the disclosed compositions; alcohols are considered especially suitable. Some suitable alcohols include methanol, ethanol, propanol, butanol, and the like, as well as combinations of the foregoing and also isomers thereof. The solvent is suitably a solvent that is common to the epoxy resin and the phenolic resin, e.g., an alcohol. The solvent may more effectively solvate the epoxy resin over the phenolic resin (or vice versa), as it is not necessary that the solvent solvate the resins equally well.

[0024] A spectrum of fillers may be used in the disclosed compositions. Some such suitable fillers include carbon nanotubes (single- and multi-wall), nanoparticles, and graphene. Suitable nanoparticles may be of titanium dioxide, silicon dioxide, and the like. Nanoparticles may be present in spherical form, but need not be spherical, as oblong and other shapes of nanoparticles may be used. The foregoing also applies to titanium dioxide and silicon dioxide that may be present in the disclosed compositions. Mixtures of fillers (e.g., single-wall carbon nanotubes and silicon dioxide nanoparticles) may be used in the disclosed compositions.

[0025] Filler bodies suitably have at least one cross sectional dimension (e.g., width, height, radius, thickness) that is in the range of from about 1 nm to about 1000 nm, or from about 10 nm to about 500 nm, or even in the range of from about 50 nm to about 200 nm, including all intermediate values of the foregoing.

[0026] The phenolic resin of the compositions may be present in a weight fraction that is equal to or greater than the amount of epoxy resin present in the composition. For example, the phenolic resin may be present at 100%, 105%, 120%, 150%, 200%, 500%, 1000%, or even 10,000% the amount of the epoxy resin. Alternatively, the epoxy resin may be present in an amount 100%, 105%, 120%, 150%, 200%, 500%, 1000%, or even 10,000% the amount of the phenolic resin. In some especially suitable embodiments, the epoxy resin is present in the range of from about 10 wt% to 60 wt%, while the phenolic resin is present in the range of from about 90 wt% to 40 wt.%.. Embodiments wherein the epoxy is present are between 40 - 60 wt % and phenolic is between at between about 60 - 40 wt% of the composition.

[0027] Filler may be present in an amount of less than about 10 wt%, about 5 wt%, or even less than about 2 wt% of the composition. The filler may be present in an amount of less than about 1 wt% of the composition, less than about 0.5 wt% of the composition. Filler levels of from about 0.1 wt% to about 0.5 wt% of the compositions are considered especially suitable.

[0028] The compositions may also include a fibrous substrate. The fibrous substrate is suitably impregnated with the epoxy resin, the phenolic resin, the solvent; and the filler, as described herein.

[0029] The fibrous substrate may be present in the form of a cloth, a yarn, a braid, a thread, and the like. The fibrous substrate may include carbon fibers, graphite fibers, aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, tungsten carbide fibers, glass fibers, and the like, as well as combinations thereof. Dimensions of suitable fibers are set forth elsewhere herein.

[0030] The present disclosure also provides prepregs. The prepregs suitably include a fibrous substrate, the fibrous substrate being impregnated with a resin admixture, the resin admixture comprising an epoxy resin, a phenolic resin, a solvent; and a filler.

[0031] Suitable resin admixtures are described elsewhere herein. The fibrous substrate may include carbon fibers, graphite fibers, aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, tungsten carbide fibers, glass fibers, and the like, as well as combinations thereof. The fibrous substrate may include unidirectional fibers, woven fibers, unwoven fibers, and the like. A fiber may have at least one cross-sectional dimension in the range of from about about 0.01 micrometers to about 100 micrometers, of from about 0.1 micrometers to about 50 micrometers, or of any intermediate value. A fiber may have a length in the range of, e.g., 0.01 micrometers to about 1 meter and of any value therebetween. The fibrous substrate may include fibers that differ from one another in terms of composition, size, or both.

[0032] The prepreg is suitably capable of remaining in a condition suitable for layup processing after storage at ambient conditions for up to six months, or even after storage in ambient conditions for up to about one year. Without being bound to any single theory, the presence of the epoxy resin, the phenolic resin, and the solvent gives rise to a prepreg capable of remaining in conditions for layup processing after extended storage at ambient conditions. The prepreg may be packaged so as to limit the prepreg's exposure to the exterior environment.

[0033] Also provided are methods. These methods suitably include contacting an epoxy resin, a phenolic resin, a solvent, and a filler to form a primary admixture. In some embodiments, a user may contact the epoxy resin to a quantity of the solvent to form a first admixture. A user may further contact the phenolic resin to a quantity of the solvent to form a second admixture. The user may then contact the first and second admixtures. The primary admixture may then be used to impregnate a fibrous substrate (described elsewhere herein) with that primary admixture.

[0034] In some embodiments, a prepreg according to the present disclosure may be heated and cooled. In one exemplary embodiment, a fabric impregnated with a composition according to the present disclosure is heated (e.g., at from 90 deg. C. to about 120 deg. C.) for from about 1 to about 10 minutes and then cooled to ambient temperature. The fabric may then be re-impregnated with the composition and again heated. The fabric may then be rolled between plastic sheets or other separator materials.

[0035] The RIMM composition described herein is utilized to fabricate prepregs that can be stored at room temperature prior to a final curing. Unlike prior prepregs, the prepregs formulated from the RIMM composition have a shelf-life or remain tacky during storage at room temperature for at least six months. In one embodiment, the prepregs formulated from the RIMM composition have a shelf-life of at least year when stored at room temperature. As used herein the term "room temperature" or "ambient" refers to a temperature that is suitably in the range of from about 20 degrees Celsius to about 30 degrees Celsius.

[0036] Unlike the prior prepregs, the prepregs formulated from the RIMM composition do not require storage at freezing temperatures. Further, unlike the prior prepregs, the prepregs formulated from the RIMM composition do not require a hardener/curing agent, although such agents may be used in some embodiments. As such, the RIMM composition reduces overall costs and increases functionality.

[0037] For instance, unlike the prior prepregs, the prepregs formulated from the RIMM composition have reduced storage and transportation costs because they do not require freezer storage. Further, unlike the prior prepregs, the prepregs formulated from the RIMM composition have an increased functionality, because they can be easily transported for long distances and do not require the end user to know the exact date of application. Additionally, the shelf life of the prepregs formulated from the RIMM composition helps to prevent purchased prepregs from expiring before use when stored at room temperature.

[0038] The polymeric resin composition as disclosed herein may, in some

embodiments, be prepared by mixing an epoxy resin with a phenolic resin in a common solvent without the use of a hardener/curing agent, such as amine. Without being bound to any particular theory, the fillers may assist the reaction mechanism and provide additional matrix strength.

[0039] The resin composition can be utilized to impregnate any suitable fiber fabric, such as glass and carbon fiber fabrics. In one embodiment, the fiber fabric is glass. A wet, resin- impregnated fiber fabric is heated to produce a macromolecular, matrix prepreg that can be stored at room temperature. The prepreg has a tacky consistency allowing for easy handling and layup.

[0040] The prepregs produced by the RIMM composition provide for storage at room temperature for at least six months. In one embodiment, the prepregs produced by the RIMM composition have a shelf-life at room temperature of 1 year.

[0041] It will be clear that the systems and methods described herein are well adapted to attain the ends and advantages mentioned as well as those inherent therein. Those skilled in the art will recognize that the methods and systems within this specification may be implemented in many manners and as such is not to be limited by the foregoing exemplified embodiments and examples.

[0042] While various embodiments have been described for purposes of this disclosure, various changes and modifications may be made which are well within the scope of the present disclosure. Numerous other changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the spirit of the disclosure.

[0043] Unless otherwise indicated, all numbers expressing quantities, properties, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure.

[0044] The term "tack" or "tacky" is well known to those skilled in the art. it is often a subjective measurement made by touching the prepreg with a finger. If the surface is "sticky" or

"tacky" then it has the property of "tack". Tack may be measured subjectively by means of many scales, but to illustrate the concept, fly paper may be considered the high point of the scale. A sheet of TEFLON™ (polytetrafluoroethylene) has no tack and may be considered the low point of the scale. Further, prepregs and films having the greater tackiness of fly paper may not be suitable for all application.

[0045] Exemplary Embodiments

[0046] A reaction-induced, macromolecular-matrix (RIMM), composition is formed by combining a component A, a component B, and a component D with a component C and mixing or sonicating. These components combine to form the RIMM composition and do not use a hardener/curing agent, such as amine. By utilizing the components as included herein, several advantages for prepregs are realized. For example, the prepregs formed from the RIMM, have a tacky consistency making them easy to use and apply. Additionally, the prepregs formed from the RJMM, composition can be stored at room temperature for at least six months before curing. In one embodiment, the prepregs formed from utilizing the RIMM composition are storable at room temperature for at least one year before curing.

[0047] COMPONENT A

[0048] Component A may be an epoxy resin.

[0049] Examples of an epoxy resin include bifunctional epoxy resins, such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, and

dicyclopentadiene type epoxy resin or modified epoxy resins thereof. Further examples of an epoxy resin include polyfunctional epoxy, such as a phenol novolac type epoxy resin and a cresol type epoxy resin. Examples of other epoxy resins include glycidylamine type epoxy resins such as tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, and tetraglycidyldiamine. Additional examples of an epoxy resin include glycidylether type epoxy resins, such as tetrakis(glycidyloxyphenyl)ethane, a tris(glycidyloxymethane), and modified epoxy resins thereof. In one embodiment, the epoxy resin is a brominated epoxy resin which is formulated by brominating any of the aforementioned epoxy resins. The foregoing list is not limiting, as any suitable epoxy resins may be utilized for forming the disclosed compositions. The

aforementioned epoxy resins may be used in combination to form component A.

[0050] In one embodiment, bisphenol A is utilized as component A. In another embodiment, diglycyclether of Bisphenol A resin is utilized as component A.

[0051] COMPONENT B

[0052] Component B is a second polymer resin that suitably differs from component A. Component B is a phenolic resin, e.g., a phenol formaldehyde resin.

[0053] COMPONENT C

[0054] Component C is a solvent. [0055] The solvent of component C is suitably an alcohol. Any alcohol or mixture of alcohols may be utilized as component C, such as n-Butonal, isoproponal, n-proponal, ethanol, and/or methanol. In one embodiment, the solvent is a simple alcohol, such as ethanol and/or methanol.

[0056] COMPONENT D

[0057] The reaction-induced, macromolecular-matrix (RTMM) composition is formed by adding component D to components A, 8 , and C.

[0058] Component D is a filled. The filler of component D includes at least one nano- filler. The nano-filler is single-walled carbon nanotubes, silicon nanoparticles, graphene, titanium dioxide, and/or silicon dioxide nanoparticles.

[0059] Component D assists the reaction mechanism and provides for additional matrix strength. In one embodiment, component D may include other suitable fillers. In another embodiment, the other suitable fillers are inorganic fine particles, such as a fine powder silica, pigments, elastomers, flame retardants, bromide compounds, phosphorus compounds, defoaming agents, imidazole derivatives, and/or metal complex salts.

[0060] Exemplary method

[0061] A compositions according to the present disclosure may be formed by performing the following steps.

[0062] Component A and component B are mixed and/or sonicated with component C to form a homogenous mixture. The homogenous mixture is then mixed and/or sonicated with a component D. Lastly, this mixture of components A, B, C, and D is incubated to form the disclosed resin composition.

[0063] The amount of component B added may be equal to or greater than the amount of component A added to the mixture. In one embodiment, the ratio of component A to component B is about 60:40. In one embodiment, the amount of component D is less than 2% and sometimes less than about 1% of the total amount of components added to make the RIMM composition. In another embodiment, the amount of component Dis about 0.55% of the total amount of components added to make the composition. Any amount of component C or solvent suitable for dissolving components A, B, and D may be added to the mixture. In one embodiment, the RIMM composition includes 40% component A, 40% component B, 19.5% component C, and 0.5% component D.

[0064] The components A, B, and C may be combined in various ways. In one combination, component A and component B are added to separate solutions of component C.

In this combination, the two separate mixtures are combined and then mixed and/or sonicated until homogeneous or in one phase. In a second combination, component A and component B are added to the same portion of component C and mixed and/or sonicated until homogeneous or in one phase. In one embodiment, component A, component B, and component C are mixed. Component A, component B, and component C may be mixed with any suitable mixing device for forming a RIMM composition, such as a shear mixer, stirrer, or sonicator. The components are mixed for about 30 to about 50 minutes. In one embodiment, the components (A, B, and C) are mixed for 45 minutes.

[0065] Next, the method for producing a RIMM composition includes adding component D or nano-fillers to the homogenous product above created by the mixture of component A, component B, and component C. In one embodiment, component Dis carbon nanotubes or graphene and silicon dioxide nanoparticles.

[0066] In one embodiment, the nano-filler added is produced by combining carbon nanotubes or graphene and silicon dioxide nanoparticles with solvent and mixing for about 4 to about 8 hours. The mixing of the nano-filler and solvent may be performed with any suitable mixing device for forming a RIMM composition, such as a shear mixer or a sonicator (in ultrasonic water bath). In one embodiment, the nano-filler added is produced by combining carbon nanotubes or graphene and silicon dioxide nanoparticles with solvent and sonicating for about 6 hours. The solvent in this example may be any of the solvents utilized for component C. Any amount of solvent suitable for dissolving component D may be added to this mixture.

[0067] After the formation of component D, component D is added to the homogenous product created above. Component D and the homogenous product created above are mixed with any suitable device for forming a RIMM composition, such as a shear mixer or sonicator (in ultrasonic water bath), for about 30 minutes to 50 minutes. In one embodiment, component D and the homogenous product created above are sonicated for 45 minutes.

[0068] Next, the method for producing a RIMM composition further includes incubating the product of component A, component B, component C, and component D in an incubator after mixing to form the desired homogenous mixture. The incubation of the product decreases the viscosity of the product to allow for better mixing of the components. The product may be incubated for about 20 to about 30 minutes after mixing. In one embodiment, the product may be incubated for about 30 minutes after mixing. The temperature of the incubator may be about 50 to about 60 degrees Celsius. In another embodiment, the temperature of the incubator may be about 55 degrees Celsius.

[0069] METHOD FOR PRODUCING PREPREGS [0070] The production of the prepreg can be carried out by known devices and methods.

[0071] The RIMM composition described above is utilized to impregnate a reinforced fiber fabric. The RIMM composition may be applied to the reinforced fiber fabric by any known suitable methods. In one embodiment, the reinforced fiber fabric is impregnated with the RIMM composition by brushing or painting the wet resin composition onto the reinforced fiber fabric.

[0072] The reinforced fiber fabric of the prepreg may be various kinds depending on the purpose of pre pre g. For example, the fibers of the prepreg may be carbon fibers, graphite fibers, aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, tungsten carbide fibers, glass fiber and/or any similar types of fibers. Moreover, different fibers may be utilized in combination. In one embodiment, the fibers are glass fibers. The configuration of the fibers in the reinforced fiber fabric may be unidirectional, woven, or unwoven.

[0073] After the RIMM composition described above impregnates the reinforced fiber fabric, the wet impregnated fiber is heated to a temperature of about 114 to about 120 degrees Celsius for about 2 to about 4 minutes to form the prep reg. In one embodiment, the wet impregnated fiber is heated to a temperature of 114 degrees Celsius for 3 minutes to form the prepreg.

[0074] The formed prepreg has a tacky consistency that allows for easy handling and layup. Further, the prepreg formed from the RIMM composition has a shelf-life of at least six months at room temperature without utilizing a hardener. In one embodiment, the prepreg formed from the RIMM composition has a shelf-life of at least a one year at room temperature without the use of a hardener. The prepreg formed from the RIMM composition may be cut into any desirable shape and size to form composite slabs.

[0075] The prepreg formed from the RIMM composition may be molded and/or applied by any known suitable methods in the formation of composite structures.

[0076] After the prepreg is applied for its intended use, it is cured by heating the prepreg to a temperature of about 200 to about 220 degree Celsius. In one embodiment, the prep reg is cured by heating to a temperature of about 220 degree Celsius. The heating rate is about one to about five degrees Celsius per minute. In one embodiment the heating rate is about one degree Celsius per minute. In another embodiment, the prepreg is heated by utilizing a forced air oven.

EXAMPLES [0077] The following are embodiments of different methods for producing the reaction- induced, macromolecular-matrix (RIMM) composition and/or prepregs formed from the RTMM composition.

[0078] EXAMPLE 1

[0079] In one exemplary embodiment, four different effective RIMM. nanoresin compositions for industrial application were made. The compositions were formed by mixing two different polymers in a common solvent. In each mixture, 2 ml of methanol was utilized as the common solvent. The first sample contained 5 gm of phenol-formaldehyde (phenolic) resin and 5 gm of diglycyclether of Bisphenol A (epoxy) resin. The second sample contained 4 gm of phenolic resin and 6 gm of epoxy resin. The third sample contained 6 gm of phenolic resin and 4 gm of epoxy. Lastly, the fourth sample contained 7 gm of phenolic resin and 3 gm of epoxy resin.

[0080] The resin was applied to a glass fiber fabric surface. Next, the prepreg was sealed on both surfaces with polypropylene sheets. The sheets were peeled after one week to expose the prepreg. Next plies were stacked in a mold to make a laminate. Accordingly, the efficacy of these RIMM compositions for industrial application was confirmed by impregnating the RIMM compositions on glass fiber fabric and heating to different temperatures to determine that viable prepregs for industrial application could be formed from these concentrations of polymers.

[0081] EXAMPLE 2

[0082] In another experiment, phenolic resin was combined with epoxy resin, silicon nanoparticles (treated) and single-walled carbon nanotubes. The mixture was sonicated in an ethanol solution. After sonication the solution appeared to be homogeneous. Next, glass fiber fabric was impregnated with the RIMM solution and then heated to about 1 12 degrees Celsius for three minutes. The fabric still appeared to be too tacky. Accordingly, the fabric impregnated with RIMM solution was heated to 1 14 degrees Celsius for and additional three minutes to form a prepreg that was suitable for use.

[0083] The resin was embedded on glass fiber fabric surface. Next, the prepreg was sealed on both surfaces with polypropylene sheets. The sheets were peeled after one week to expose the prepreg. Next, plies were stacked in a mold to make a laminate. A 5 mm thick composite was obtained after beating the laminated prepreg in the mold to a temperature of about

220 degrees Celsius. Accordingly, this experiment determined that a composition formed from these concentrations requires heating to a minimum temperature of about 114 degrees Celsius to form a suitable prepreg for industrial application. Further, this experiment determined that a prepreg is suitably cured for industrial application when heated to a temperature of 220 degrees Celsius.

[0084] EXAMPLE 3

[0085] In this experiment, 75 ml of phenolic resin was combined with 35 ml of epoxy resin, 0.5 gm of silicon nanoparticles (treated), 0.015% single-walled carbon nanotubes, and 25 ml of methanol and then mixed. The mixture was then incubated at a constant temperature in an incubator for 30 minutes. After incubation, the solution appeared to be in one phase to form a RTMM composition. Next, a 24 x 12 inch glass fiber fabric was impregnated with the RIMM nano-resin composition and heated to 1 12 degrees Celsius for three minutes. The fabric was quite tacky, so the fabric impregnated with RIMM was subsequently heated to 1 14 degrees Celsius for an additional three minutes. The produced prepreg was weighed to check the amount of resin on the surface. Because the resin concentration was 40% or higher, the formed prepreg was considered generally acceptable for composite manufacturing. The formed prepregs were cut and rolled between polypropylene sheets for storage prior to use.

[0086] Accordingly, this experiment also showed that a composition formed from these concentrations requires heating to a minimum temperature of about 1 14 degrees Celsius to form a suitable prepreg for industrial application. Further, this experiment showed that if the impregnated fabric was heated to more than 5 degrees above 114 degrees Celsius, the prepreg cures and if temperature remained 5 degrees below 1 14 degrees Celsius, the prepreg was too tacky and could not be rolled between the polypropylene sheets.

[0087] EXAMPLE 4

[0088] In yet another experiment, a RIMM composition was made by utilizing the following process. First, 75 ml of phenolic resin was added to 15 ml of methanol to form a phenolic resin solution. Next, 35 ml of epoxy resin was added to 10 ml of methanol to form an epoxy resin solution. The phenolic resin solution and the epoxy resin solution were combined to form a combination mixture.

[0089] A composition of 0.5 gm of silicon dioxide nanoparticles, 0.0165 gm of single— walled carbon nanotubes, and 10 ml of a methanol/ethanol was added to a sonicate and sonicated for four hours to form a sonicated composition.

[0090] The sonicated composition was mixed with the combination mixture and sonicated for 30 minutes in a sonication water bath to form a sonicated mixture. Next, the sonicated mixture was heated in an incubator for 30 minutes at 50 degrees Celsius to form the

RIMM composition. A portion of the RIMM composition was applied to a glass fiber fabric utilizing a paint brush. After the application of the composition, the wet impregnated glass fiber fabric was heated to 120 degrees Celsius for 3 minutes. After heating, more of the RIMM composition was applied to both sides of the once heated glass fiber fabric. Next, there-wetted glass fiber fabric was heated to 120 degrees Celsius for 2 minutes. The impregnated fabric was cooled with air and then rolled between two polypropylene sheets to form prepregs. The prepregs were cut into composite slabs of desired shape and size from the cooled rolled sheets.

[0091] Next, this experiment further applied and cured the prepregs to form a composite structure. First, the prepreg made by the above process was cut into 5 x 6 inch pieces. Next, the cut prep reg were stacked in a three piece split mold and then manually tightened with the help of four nuts and bolts. The prepregs were tacky for easy application. The mold and the prepreg sheets were heated until a temperature of 220 degrees Celsius was reached in a forced air oven. The heating rate for the forced air oven was one degree Celsius per minute. After heating, the mold was cooled to room temperature and the composite slab was removed. Scanning electron microscope (SEM) analysis suggested that the fibers were well adhered with the resin. The results of the SEM analysis are illustrated in FIG. 3. FIG. 3 illustrates how the glass fibers are embedded inside the RIMM matrix at different levels of magnification (40 micrometers & 50 micrometers). Accordingly, the cured prepregs formed an effective structural composite for industrial application.

[0092] EXAMPLE 5

[0093] FIG. 1 illustrates a Fourier transform infrared (FTIR) spectra showing the percent of transmittance at increasing wavelengths for three differently formulated RIMM resins. The FTIR spectra were acquired on resins coated and heated over a potassium bromide pellet. The first formulated RIMM resin was heated to 65 degrees Celsius for one hour. The second formulated RIMM resin was heated from 50 degrees to 200 degrees Celsius. The third formulated RIMM resin was maintained at ambient temperatures and was not heated. The appearance and disappearance of peaks on the spectra are signatures of certain reactions occurring in the resin with the change in time and temperatures. For instance, the disappearance of a peak at approximately 915 cm^"1 from the third formulated RIMM resin suggests the disappearance of hydroxyl functionalities from the epoxy as well as the phenolic resin. This disappearance of hydroxyl functionalities from the epoxy as well as the phenolic resin indicate that the RIMM resin forms an intermediate compound that can be stabilized for a longer period oftime than the first two formulated RIMM resins.

[0094] EXAMPLE 6

[0095] FIG. 2 illustrates a FTIR spectra showing the percent of transmittance at increasing wavelengths for three differently formulated prepregs. The first formulated prepreg was heated to from 50 degrees to 20 degrees Celsius. The second formulated prepreg was heated to 140 degrees Celsius. The third formulated prepreg was heated to a temperature of 200 degrees Celsius. Again, appearance and disappearance of peaks on the spectra are signatures of certain reactions occurring in the prepregs with the change in time and temperatures.

[0096] INDUSTRIAL APPLICABILITY

[0097] The compositions described herein provides a prepreg that is easy to handle and apply due to its tackiness. Further, the RTMM composition described herein provides for a prep reg without the use of hardener/curing agent. Additionally, the RIMM composition described herein forms a prepreg that is storable at room temperature prior to curing for at least six months. The prepregs made with the RIMM composition have a wide potential application for advanced structural composites. For instance, the prepregs may be utilized in the following fields:

aerospace industry, marine industry, automotive industry, energy research, space research, and any other similar fields.

EXAMPLE EMBODIMENTS

[0098] A reaction-induced, macromolecular-matrix, nano-resin composition comprising: component A, component B, component C and component D, wherein: the component A is an epoxy resin;

the component B is a phenolic resin;

the component C is a solvent; and

the component Dis a filler, the filler comprising at least one nano-filler, wherein the components combine to form a reaction-induced, macromolecular-matrix, nano-resin

composition without utilizing a hardener.

[0099] In one embodiment, the component D comprises single-walled carbon nanotubes and silicon dioxide nanoparticles.

[0100] In another embodiment, a reaction-induced, macromolecular-matrix, nanoresin composition comprising:

component A, component B, and component C, wherein:

the component A is an epoxy resin;

the component B is a phenolic resin;

the component C is at least one of methanol and ethanol; and

the component Dis a filler, the filler comprising at least one of single- walled carbon nanotubes and silicon dioxide nanoparticles,

wherein the components combine to form a reaction-induced, macromolecular-matrix, nano-resin composition without utilizing a hardener. [0101] In yet another embodiment, a prepreg comprising a reinforced fiber fabric impregnated with the above reaction-induced, macromolecular-matrix, nano-resin composition. In one embodiment, the reinforced fiber of the prepreg is glass fiber. In a further embodiment, the above prepreg has a shelf-life at room temperature of at least one year.

Claims

What is Claimed:

1. A composition, comprising: an epoxy resin; a phenolic resin; a solvent common to the epoxy resin and the phenolic resin; and a filler.

2. The composition of claim 1, wherein the epoxy resin comprises a bifunctional epoxy resin, a polyfunctional epoxy resin, a glycidylamine epoxy resin, a glycidylether epoxy resin, a brominated epoxy resin, or any combination thereof.

3. The composition of claim 2, wherein the bifunctional epoxy resin comprises a bisphenol A epoxy resin, a bisphenol F epoxy resin, a biphenyl epoxy resin, a dicyclopentadiene epoxy resin, or any combination thereof.

4. The composition of claim 2, wherein the polyfunctional epoxy resin comprises a phenol novolac epoxy resin, a resol epoxy resin, or any combination thereof.

5. The composition of claim 2, wherein the glycidylamine epoxy resin comprises a tetraglycidyldiaminodiphenylmethane, a triglycidylaminophenol, a tetraglycidyldiamine, or any combination thereof.

6. The composition of claim 2, wherein the glycidylether epoxy resin comprises a tetrakis(glycidyloxyphenyl)ethane, a tris(glycidyloxymethane), or any combination thereof.

7. The composition of claim 1, wherein the phenolic resin comprises a phenol formaldehyde resin.

8. The composition of claim 1, wherein the solvent comprises an alcohol.

9. The composition of claim 8, wherein the alcohol comprises methanol, ethanol, propanol, butanol, or any combination thereof.

10. The composition of claim 1, wherein the filler comprises carbon nanotubes,

nanoparticles, graphene, titanium dioxide, silicon dioxide, or any combination thereof.

1 1. The composition of claim 1, wherein the phenolic resin is present in the composition in an amount equal to or greater than the amount of epoxy resin present in the composition.

12. The composition of claim 1, wherein the filler is present in an amount of less than about 2 wt% of the composition.

13. The composition of claim 12, wherein the filler is present in an amount of less than about 1 wt% of the composition.

14. The composition of claim 13, wherein the filler is present in an amount of less than about 0.5 wt% of the composition.

15. The composition of claim 1, further comprising a fibrous substrate, the fibrous substrate being impregnated with the epoxy resin, the phenolic resin, the solvent common to the epoxy resin and the phenolic resin, and the filler.

16. The composition of claim 15, wherein the fibrous substrate comprises carbon fibers, graphite fibers, aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, tungsten carbide fibers, glass fibers, or any combination thereof.

17. A prepreg, comprising: a fibrous substrate, the fibrous substrate being impregnated with a resin admixture, the resin admixture comprising an epoxy resin, a phenolic resin, a solvent common to the epoxy resin and the phenolic resin, and a filler.

18. The prepreg of claim 17, wherein the fibrous substrate comprises carbon fibers, graphite fibers, aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, tungsten carbide fibers, glass fibers, or any combination thereof.

19. The prepreg of claim 17, wherein the fibrous substrate comprises unidirectional fibers, , woven fibers, unwoven fibers, or any combination thereof.

20. The prepreg of claim 17, wherein at least one fiber comprises a cross-sectional dimension in the range of from about 0.01 micrometers to about 100 micrometers

21. The prepreg of claim 17, wherein the prepreg remains in a condition suitable for layup processing after storage at ambient conditions for up-to six months.

22. The prepreg of claim 17, wherein the prepreg remains in a condition suitable for layup processing after storage at ambient conditions for up to one year.

23. A method, comprising: contacting an epoxy resin, a phenolic resin, a solvent, and a filler to form a primary admixture.

24. The method of claim 23, further comprising contacting the epoxy resin to a quantity of the solvent to form a first admixture.

25. The method of claim 24, further comprising contacting the phenolic resin to a quantity of the solvent to form a second admixture.

26. The method of claim 25, further comprising contacting the first and second admixtures.

27. The method of claim 23, further comprising impregnating a fibrous substrate with the primary admixture.