CA1326930C - Curable epoxy resin composition - Google Patents

Abstract

ABSTRACT

Curable compositions comprising epoxide prepolymers and polyaminobenzoates combined with reinforcements and, optionally, modified with second resins. The cured resin fiber matrix compositions exhibit high toughness combined with excellent hot/wet strength.

Description

1 326q30 :
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CURABLE EPOXY RESIN COMPOSITIONS

' FIELD OF THE INVENTION

. . .
This is a divisional of Canadian application, Serial No.
, 460,012 filed July 30, 1984 and relates to improved epoxy resin . compositions. In addition, it relates to curable epoxy resin compositions comprising reinforcing filaments and epoxy prepolymers combined with aromatic polyamine curing agents.

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BACRGROUND OF THE IN~ENTION
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Epoxy resin compositions are useful to encap-sulate electronic components, and as structural adhes-ives, and the like. Reinforced epoxy resin compositeshaving high strength to weightratios have found extensive use in the aircraft and aerospace industries, and in other applications where strength, corrosion resistance and light weight are desirable. For instance, fiber resin matrix materials have replaced aluminum and other metals in primary and secondary structures of modern military and commerical aircraft. Sporting equipment such as tennis rackets and golf clubs have also adopted fiber resin materials successfully.
Epoxy resin compositions and fiber modifica-tions are abundant. Since the advent of fiber resin matrix materials, much effort has been expended in improving their properties and characterisitics, includ-ing the development of many different curing systems.

Amine and polyamine curing agents have receivedwide acceptance, but the toxicity, low solubility, high exotherm and variable curing rates seen with the most commonly used amines, such as m-phenylenediamine, 4,4'-diaminodiphenyl methane and 4,4'-diaminodiphenyl sulfone, has made further improvement desirable. In particular, for aircraft structural applications, epoxy resins cured with available curing agents are either too brittle or do not have sufficient strength and stiffness under hot/-wet conditions. It is disclosed in U.X. Patent 1,182,377, that certain aromatic polyamines are effective as curing agents for a variety of polyepoxides, and the resulting cured compositions are useful as films, moldings, coat-' ~

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ings and glass-reinforced laminates. There is no indication in the properties presented in the U.R.
Patent that the curing agents exemplified therein will produce the combination of toughness and strength under S hot/wet conditions essential for use in the above-mentioned structural applications.

, In U.S. 3,932,360, diamine cured polyurethane products are described, in which the diamines are of the formula, e.g., H2N~ O ~CH2)n ~NH2 wherein n is an integer from 2 to 12. This '360 pa~ent does not deal with curing compounds having more than one epoxide groups per molecule.

; In Gillhan et al, Organic Coatings and Applied Polymer Science Proceedings, Vol. 46, p. 592-598, March-April, 1982, polyepoxides cured with diamines of the immediately preceding formula (n is 3), are f 2S descri~ed.
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The present development relates to curable epoxy resin compositions. In one of its aspects, it provides fiber resin matrixes comprising reinforcing filaments in a heat-curable epoxy resin composition comprising an epoxy prepolymer and a novel family of ~1 aromatic polyamine curing agents. No member of this novel family of curing agents is specifically exemplified I in the U.K. Patent. The invention provides neat resin formulations having, after cure improved physical ~.j ~ f ~: . . - :

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:- -1 326q30 propertles, e.g. hlgher elongatlon and satisfactory hot/wet modulus. The epoxy composltlons of the present lnventlon, cured , wlth fllaments, exhlblt lmproved lnterlamlnar toughness and resldual compresslon strength after lmpact, while malntalnlng compresslon strength under hot/wet condltlons.

' SUMMARY OF THE INVENTION
The present lnventlon seeks to provlde lmproved epoxy ; resln composltlons.
The present lnventlon also seeks to provide a flber matrlx compositlon that affords satlsfactory compresslon strength ; over known matrlx formulations, especlally under hot/wet condl-i tions, and lmproved compresslon strength after lmpact.
Accordingly, the present lnventlon relates to flber i relnforced heat-curable epoxy resln composltlons comprlslng a siliceous reinforcement fllament and ~1) an epoxy prepolymer or comblnatlon of prepolymers ~ having more than one epoxide group per molecule, an~
¦ ~ii) an amount effectlve to promote cure of an amlne-functlonal curlng agent or comblnation of curlng agents selected from those of the formula, R NN~ O (CH2)z 0 C O_NHR

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1 3 2 6 ~ 3 0 61109-7316D
wherein Rl is hydrogen or methyl, and z is an integer of from 2 to 12, with the proviso that when Rl is hydrogen, the amine-functional curing agent is not present in greater stoichiometric amounts than the epoxy prepolymer.
It is among the features of this aspect of the invention to provide such compositions in filled and/or reinforced, e.g., glass fiber reinforced, embodiments which are useful as prepregs, for example, to make laminates and other structual shapes in accordance with procedures known in this art.

DESCRIPTION OF THE DRAWINGS
FIGURE 1 iS a schematic of one method for preparing a fiber resin matrix prepreg tape of the present invention.
FIGURE 2 is an enlarged cross-sectional view of a strip of the fiber resin matrix prepreg tape of the invention.
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FIGURE 3 is a graphical representation compar-ing hot/wet compressive strength versus dry impact strength for composites according to this invention with state-of-the-art composites.
,., DESCRIPTION OF THE PREFERRED EMBODIMENTS
:
In general, the resin compositions of this invention are prepared by mixing the polyepoxide com-pounds with the polyamines of the above-mentioned formula in conventional quantitative ratios, e.g., - 1 epoxide equivalent to 0.3 to 3.0 NH- equivalents, preferably 1.0 to 3.0 NH- equivalents, and especially preferably 1.5 to 2.5 NH- equivalents, optionally with heating, e.g., at a temperature in the range of 30 to 300~C., preferably at a temperature in the range of 80 to 180C., until a melt is obtained. The melt can then be poured into a mold and reacted, for example, ;~ for 2 hours at 135C. and then for 3 hours at 180C., to form moldings showing outstanding mechanical and electrical properties. The NH- equivalents is the quantity of aromatic polyamine in grams in which 1 gram -atom of hydrogen combined with amine nitrogen is present.

-~1 25 Fillers, pigments, dyes, reinforcements, suchas glass fibers or woven cloths, plasticizers, and mixtures thereof, may be added to the epoxy resin - polyamine composition before the reaction in order to modify ultimate properties, in known ways. Applications can also be made by trowelling, brush coating, immersion or dip-coating, spraying and other convenient method. Catalysts, such as boron trifluoride - organic amine adducts, and the reaction product of toluene 2,4-diisocyanate and dimethylamine can also be included, in quantities of 35 ~

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from e.g., 0.1 to 5% by weight based on the resin -polyamine, to accelerate curing.

The fiber resin matrix compositions according to the present invention can be prepared by embedding filaments! e.g., glass fibers and/or non-siliceous filaments in a curable resin composition to form a fiber resin matrix which can be manipulated and cured to a solid composite. ParticuIar selection of the filament material, epoxy prepolymer and curing agent, as well as including optional ingredients such as fillers, dyes, catalysts, processing aids, etc.,can give a range of curable compositions heretofore unknown in the art and exhibiting improved physical properties over known materials.

Glass filaments useful herein are well known.
, The non-siliceous filament component may be of any non-glass, non-silicon dioxide-containing material which improves the strength or other physical properties of the curable epoxy resin component (described infra.).
Such filaments include, but are not limited to, filaments comprised of carbon, graphite, silicon carbide, boron, aramid, polyester, polyamide, rayon, polybenzimidazole, polybenzothiazole, metal-coated such filaments, for example nickel-coated and/or silver-coated graphite fibers and filaments, or combinations of such filaments.
Fibers (woven or non-woven), tows or mats of such fila-ments, or tapes (unwoven, flat bundles of the unidirec-tional filaments) may be employed as desired. In appli-cations dem~ing high stiffness to weight ratio or shear strength, carbon fibers, graphite filaments, polyaramid ~ filaments or nickel-plated graphite filaments, as dis-35 closed in assi~nee~s ~nPn~; n~ ~n~ n ~ n ~

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-81.326930 -- 423,551 are mDst preferred. ~--~ The epoxy resins suitable for the present inven-~ tion are compounds having more than one epoxide group ; 5 per molecule available for reac~ion with the primary and secondary polyamines of the present invention (described infra.). Such epoxy prep~lymers include but are n~t lLmited to polyglycidyl ethers of polyvalent phenols, for example - pyrocatechol; resorcinol; hydroquinone; 4,4'-dihydroxy-diphenyl methane; 4;4'-dihydroxy-3,3'-dimethyldiphenyl - methane; 4,4'-dihydroxydiphenyl dimethyl methane; 4,4'-~ dihydroxydiphenyl methyl methane; 4,4'-dihydroxydi-~A phenyl cyclohexane; 4,4'-dihydroxy-3,3'-dimethyldi-,",A~ phenyl propane; 4,4'-dihydroxydiphenyl sulphone; or ' 15 tris-~4-hydroxyphenyl) methane; polyglycidyl ethers of the chlorination and bromination products of the above-mentioned diphenols; polyglycidyl ethers of novolacs (i.e., reaction products of monohydric or polyhydric phenols with aldehydes, formaldehyde in particular, ~ 20 in the presence of acid catalysts); polyglycidyl ethers i~ of diphenols obtained by esterifying 2 mols of the sodium salt of an aromatic hydroxycarboxylic acid with l l. of a dihalogenoalkane or dihalogen dialkyl ether ~U.X. 1,017,612); and polyglycidyl ethers of poly-phenols obtained by condensing phenols and long-chain halogen paraffins containing at least 2 halogen atoms , (U.X. l,024,288).

Other suitable compounds include polyepoxy compounds based on aromatic amines and epichlorohydrin, for example N,N'-diglycidyl-aniline; N,N'-dimethyl-N,N'-diglycidyl-4,4'-diaminodiphenyl methane; N,N,N',N'-tetra-~; glycidyl-4,4'-diaminodiphenyl methane; and N-diglycidyl-, 4-aminophenyl glycidyl ether. Special mention is made .~ ,.

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: I 1 326930 g of N,N,N',N'-tetraglycidyl-1,3-propylene bis-4-aminobenzoate.

Glycidyl esters and/or epoxycyclohexyl : 5 esters of aromatic, aliphatic and cycloaliphatic poly-carboxylic acids, for example phthalic acid diglycidyl ester and adipic ester diglycidyl and glycidyl esters of reaction products of 1 mol of an aromatic or cyclo-aliphatic dicarboxylic acid anhydride and 1/2 mole of a diol or l/n mol of a polyol with n hydroxyl groups, or hexahydrophthalic acid diglycidyl esters, optionally substituted by methyl groups, are also suitable.

Glycidyl ethers of polyhydric alcohols, . 15 for example of 1,4-butanediol; 1,4-butenediol; glycerol;
~' l,l,l-trimethylol propane; pentaerythritol and poly-ethylene glycols may also be used. Triglycidyl isocyan-,; urate; and polyglycidyl thioethers of polyvalent thiols, 3 for example of bis mercaptomethylbenzene; and diglycidyl-trimethylene sulphone, are also suitable.

Preferably the epoxy prepolymer component will be selected from compounds having the idealized formula:

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1 326~30 o and halogen and alkyl substituted derivatives of such compounds, wherein c is 2, 3 or 4 and equal to the valence of Q; Q is a divalent, trivalent or tetravalent radical; G is -O-, NR'- or -N-; R is hydrogen or alkyl; and d is 1 or 2 depending on the valence of G.

. The most preferred epoxy compounds will include the following:

_(~N~(C~2~x~-N~)2 wherein x is an integer from 1 to 4, available commerci-~ ally (where x=l) as Araldite ~ MY-720 (Ciba-Geigy);
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~ ~ ) 3 ; - available commercially as XD7342*(Dow Chemical);

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;~.' available commercially as DER331*(Dow Chemical) or .,3 EPON 828 (Shell);
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X~ )YOy ~ CH2 f '~

n ,~ , ,, wherein Y is 1 or 2, X is -O- or -N-,R3 is H or C~3 'l 15 and n is 2 to 8.
~, Compounds in which X is -O- are available as - a mixture under the tra~rk DEN-438 from Dow Chemical Company.
Also preferred are triglycidyl ethers of meta- and para-hydroxyaniline, e.g., represented by t'he formula: ' O ~ O ~ N 4 ~ ) ' These are available under the ~rademark ARALDITE~ 0500, ' 0510 from Ciba-Geigy.
The polyaminc curing agcnts arc of "t,hc fornula:
X{~ N)lR) :~.

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^., - - -1 326q30 o wherein a is 2 or 3, R is hydrogen alkyl or aryl, and X is a divalent or trivalent organic hydrocarbon, hetero-interrupted hydrocarbon, or substituted hydrocarbon radical or -N- . They may beprepared from correspond-ing starting materials, e.g., nitro compounds, byreduction, for example, according by methods described i in U.K. Patent 1,182,377. In addition, commonly assigned .:, Canadian application No. 460,022, shows an elegant method for N-methylation, using succinimide and formal-dehyde with the primary amine, followed by reductive :~ cleavage.

,,,' ~ Preferred curing agents are compounds accord-,;'f 15 ing to the a~ove formula in which R is hydrogen, Cl-C3 alkyl, or phenyl and X is a divalent or trivalent I radical of valence a, selected either from (1~ a divalent group consisting of -(CH2)y~, wherein y is an integer of from 2 to 12, -(CH2CH2OCH2CH2OCH2CH2)-, ~ > ~ C ~

-CH2~)-CHZ-~

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-CH2 ~ CH2~ H2~C~cH2~ , or (2) a trivalent group consisting of -N- and -(CH2)n-CH-, (CH2)m- , wherein n and m are the same or different .~, 10 integers from 1 to 4.
;~ More preferred curing agents are the following:

H2N- ~ -C-O-~CH2)z-O-C- ~ NH2, wherein z is an integer of from 2.-.to 12, preferably 2 to 6, ~--C-O-~CN2)z~0~C~

! H2 NH2 . wherein z is an integer from 2 to 12, prefera~ly 2 to 6, .,~ .

H2N- ~ ~-O-Y-O-C ~ NH2 ~ wherein ., .
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~CH~ CH2-<~ CH2 i 5 CH3 C 2 ~ -CH2- 1_CH2_ , -O ; or ~, IN2-o-c-~NN2 CN2-O-C-~N 2 CN-O-C-~NN2 : CN-O-C-~Nd2 :~ CH2_o_C_(~NH2 CH2-0- -(~NH2 :~ 20 O-C~N21 : and N ~-C O~CN2~Z <~I-CN3, wherein . - ~
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. z is an integer cf from 2 to 12, preferably 2 to 6.

In the most preferred compounds, the primary diamine will include one or more of a compound of the formula:
., :.! R HN~e-O- (CH2) Z-O-c~N~Rl . ,, wherein Rl is hydrogen or Cl-C6 alkyl, e.g., methyl, and z is an integer of from 2 to 12, preferably 2 to 6, and most preferably 3. Also contemplated are the use of such compounds in combination with other conventional poly-amines such as methylene dianiline, phenylene diamine, 1 15 and the like.
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One method of forming the fiber matrix composition , of the invention is illustrated in the drawings. As seen in FIGURE 1, the basic fiber matrix material is ; 20 produced by delivering fiber 2 through conventional eyeboards 4 and 6 to a pressure roller assembly 8. The resin composition is coated in a layer 10 from a conven--.~, tional film coating applicator 12 onto a substrate .' such as release paper 14 and passed through the pressure ~ 25 roller assembly 8. Release paper 16 is also delivered ') to the pressure roller assembly 8.

The pressure rollers 8 are set at a temperature and pressure for imbedding the fibers 2 in the resin . 30 layer 10 to form a fiber matrix composition 18. Practice has taught that a temperature in the range of 190F. and ,' pressures of one thousand pounds over fifteen inch centers are suitable for producing fiber resin prepreg ;;~ tape 18.
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The fibers 2, the substrate 14 with resin layer 10 and the release paper 16 are delivered to the ; pressure rollers 8 and passed therethrough at the - rate of 5-20 feet/minute.
¦ The feed of fibe_ 2 and resin layer 10 to the pressure rollers 8 is selected to produce a fiber matrix of about twenty to sixty weiqht percent resin and about eighty to forty weight percent fiber. For example, one hundred twenty spools of 6K carbon fibers are delivered within a twelve inch width to the ; pressure rollers 8 with a layer of resin 0.009 to 0.0013 pounds per square foot. The resulting fiber resin matrix 18 results in a generally parallel array of fibers, shown by FIGURE 2.

Fillers, pigments, dyes, curing catalysts and other such conventional additives and processing aids may be added to the fiber matrix compositions of the invention before curing to influence the properties of the final resin composite. In addition, polymeric additives such as the butadiene-styrene-acrylonitrile core-shell polymers and the like can be included for their known effects on polymer properties.

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The following examples will illustrate the practice of the present invention and are provided by way of demonstration and not by way of limitation.

3 The following procedure is used to prepare Z and cure neat resin compositions: the epoxide pre-polymer and the polyamine component are mixed at 135C.
, 10 for 10 minutes, and cooled to 100C, the catalyst, if any, is mixed in, and the mixture is degassed for 10 minutes. The liquid resin is then poured into a mold and cured for 2 hours at 135C and for 3 hours at 180C.
Properties are determined by the following procedures:
The flexural test is described in ASTM D-790, Method I.
Dynamic mechanical analysis was performed on a Dupont 981 Dynamic Mechanical Analyzer, and Tg was defined as the temperature at which the loss tangent, tan ~, is a maximum. ASTM D4065 test method covers this type of Tg measurement. Conditioning before testing is ' described by the phrases "wet" and "dry". "Wet" refers to conditioning for two weeks at 71C, immersing in distilled water, prior to testing at 93C. "Dry" means testing a sample, as prepared, at 2~ C. The formulations tested and the results obtained are set forth in Table I:

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H ! ri ri ~ ~U ;a P~ e J~ u~ u, ~ è u o ;j W H ~ o i O J ~i ri Cl~ 8 ~ ~ ~Hi i ql '10 ,~1~ --i O ~1 ., ~, u., - e ~ ~ ~ ~ a-- ri 010 ~ ~ Li ~i ~ ` ~
P1 O Zri ~11 ri ~U I I ~ Ui ~ ~ O ~ ~1 0 ri b~
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X O ~ ri Ll 0 ~ .a Ql ~O ~ ~;
a E~i'~ Z 0: P~

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The data demonstrate that when the composi-tions of this invention are cured and tested, in com-parison with a standard curing agent, para-diaminodi-phenyl sulfone,flexural strength is increased, strain is increased, and work-to-break is increased. Some 3 properties are decreased oniy slightly. In addition, Tg is reduced by only an average 10%. The advantages of the compositions of this invention are thus shown.

Three fiber resin matrix formulations were-prepared from the following materials:
-!
component (a~ CELION~ 6X high strain qraphite fiber component (b)(i) ARALDITE~ MY720 EPON~ 1031 (see formulae, suPra.) ~curing agent) (ii) trimethylene bis-(p-. aminobenzoate) ' (optional curing agent) diaminodiphenyl sulfone (DDS) ? polymer modifier acrylonitrile-butadiene-styrene, core-shell polymer catalyst toluene-2,4-diisocyanate reaction product with dimethyl amine filler fumed colloidal silica ~Cab-O-Sil* M-5 Cabot Corp.).
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` Using an apparatus shown generally in Fig. 1, prepreg tapes of the structure shown generally in Fig.
2, were prepared:
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(28%) Resin mixture (parts bY weight) N,N,N'N'-tetra(glycidyl-4,4' diaminodiphenyl)methane 80 ao 80 Tetraglycidoxy tetraphenylethane 2020 20 10 Trimethylene bis-(para-ami~obenzoate) 44 44 65 Diaminodiphenyl sulfone ~ 20 Polymer modifier* -- 5 --1~ Catalyst Fumed silica 6 6 6 ,, , .. _ (72%) Filament(parts by weight) (6K graphite fibers having a strain to failure of about 1.5%) :, . .
i3 * BLENDEX 311, Borg-Warner Co (Tradem~rk) .; .

These samples were cured and compared against ~; commerical epoxy resin matrixes. rhe sheets of resin involved were as follows:
Uni-Comp : 8 sheets [0]
Quasi-Comp : 16 sheets[(~45/0/90)2]s i, Comp./Impact: 36 sheets.[(+45/0/90/0/90)2_ ',! /+45/0/-90/l45]5 ~1 .
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The compressive strength was measured on a modified ASTM D695 specimen described in D.H. Woolsencraft et al, Composites, Oct., 1981, pages 275-280. Both unidirec ~ tional and quasi isotropic laminates were tested by ! 5 this method. Compressive strength after impact was measured as described in B.A. Byers, NASA Report No.
CR 159293, August, 1980. This property is tested by subjecting a cured laminate specimen to 1500 in.-lb.
per inch of nominal thickness impact with a 0.62 diameter - 10 spherical tip impacter while supported by a rigid base ~e.g., 3x5 in. steel cutout). The panel is then tested in compression. The results are set forth in Table 2, as follows:

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Some of the foregoing data are represented graphically also in FIG. 3. The data demonstrate that reinforced compositions according to this invention (Examples 6 and 7) have higher compression strength after impact than two of the three commercial composi-tions, and better hot/wet compression strength than one of them.

:: EXAMPLES 9-11 ,~
~ 10 : Using the general procedure of Exa~ple 1, compositions were prepared and tested. The formulations used, and the results obtained are set forth in Table 3.
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X 1 ~ 1 oa~ ~ ~ .~ _ -.. 3 ~ d a. _ ~ ~ U l _) '~ ~A ~ O ~ K ~--~.! ~~ ~ I >~ Il~ C,) U~ ~ ~ t~ ¦
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~ H f~ ,y ~, o ::f ~y 1 326q30 -27 _ ~ _ _ By the general procedure of Examples 6-8, the resins of Examples 9 and 10 were made into prepregs with graphite fiber (CELION~ high strain graphite fiber).
The prepreg had a resin content of 28% and a reinforce-ment content of 72%, by weight. Thirty six plies were consolidated under heat and pressure into a unidirec-tional laminate at 15~ F. for 1 hour and 350F. for - 10 two hours. Compressi~e strength after impact was measured 1500 in.-lb./in. thickness, with the following results: Example 12, 34 ksi, and Example 13, 33 ksi., demonstrating excellent properties in this respect.
.

The general procedure of Example 1 was used < to prepare and test compositions according to this invention which also include, ~ethylene dianiline i~ 20 bismaleimide. The formulations used and the results ~; obtained are set forth in Table No. 4.
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1 326q30 _28_ TABLE 4: EPOXY COMPOSITIONS AND PROPERTIES

: COMPOSITION ~parts by weight) N,N,N',N' tetraglycidyl-4,4'-diamino ~iphenyl methane60 60 60 60 Diglycidyl ether of bisphenol-A 40 40 40 40 Trimethylene bis-~p-amino-benzoate 50 50 50 50 : Methylenedianiline bis ; 10 maleimide * 5 10 15 20 PROPERTIES
Modulus, MSI dry 0.46 0.48 0.470.49 Strength, KSI dry 23.2 21.5 22.923.0 :. Strain, % dry 7.3 6.1 6.66.2 :~ 15 Work-to-break, in-lbs./in.3 dry 1070 810 910840 Tg, C. dry 207 208 207206 ._ 20 ¢N ~C112~) O O
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, .: . ` , The general procedure of Example 1 was used to prepare and test compositions according to this invention, substituting different epoxy resin prepoly-mers:

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~ TGPC ~ ~ C- ~ CN2 ~ C ~ N ~ 0)7 "~ O
E RL- 4 2 9 9 --- ~ C 20C ~CN ~ C-O-CII z~CcO

2 5 ARALDI TE 0 5 1 0- - o~/\ O--(~ N ~ ) 2 ''I
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_30_ The formulations used and the results obtained are set forth in Table No. 5:

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TABLE No. 5: EPOXY COMPOSITIONS AND PROPERTIES

COMPOSITION (Parts bY weight) : N,N,N'N'-tetra~lycidyl 3,3'-diamino-diphenyl sulfone 100 N,N,N'N'-tetraglycidyl tri-10 methylene bis-(p-aminobenzoate) ~ 100 - -Bis-(3,4-epoxy-6-methylcyclo-hexylmethyl) adipate ~ ~ 100 100 :~ N,N-Diglycidyl-4-aminophenyl glycidyl ether - - - 100 ~rimethylene bis (p-15 aminobenzoate) 51 38.5 37.4 62.8 PROPERTIES
Modulus, MSI dry 0.630.55 *NA 0.53 wet 0.350.18 NA 0.26 Strength, KSI dry 23.023.4 NA 21.3 Strain, % dry 4.0 5.5 NA 5.6 Work-to-break, in.-lb./in 3 dry 485 770 NA 740 Tg, C. dry/wet 240/223 - NA /156 ~ Not yet available ~!

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_31 _ : EXAMPLES 22-24 :
The ~eneral procedure of Example 1 was used to prepare and test compositions according to this invention, substituting an N-methylated curing agent.
~ The formulations used and the results obtained are - summarized in Table No. 6:

TABLE No. 6: EPOXY RESIN COMPOSITION AND PROPERTIES
EXAMPLE . 22 23 24 - COMPOSITION (equivalents) 'J
N,N,N'N'-tetraglycidyl-4,4'-diamino diphenyl methane - 1.0 1.0 1.0 N,N'-dimethyl-~rimethylene bis-(p-aminobenzoate) 1.0 0.8 0.6 PROPERTIES
Modulus, NSI dry 0.49 0.49 0.48 wet 0.19 0.22 0.25 ;I Strength, KSI dry 22.8(y)* 21.7~y) 21.9(y) ~A 20 Strain, % dry 7.1(y) . 7.1(y) 7.5(y) ~1 Work-to-break, ,~ in-lb/in.3 dry >1698 ~1600 >1470 :~, Tg, C. dry/wet 158/120 165/- 163/-:.
3 ~ (y) yield ,, .~
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The general procedure of Example 1 was repeated, increasing the ratio of amine equivalents to epoxide equivalents. The formulations used, and the results obtained are shown in Table ~o. 7:
., TABLE No. 7: INCREASING THE AMINE/EPOXY RATIO

COMPOSITION (equivalents) . N,N,N',N'-tetraglycidyl-4,4'-d~no di~henyl m~ne 1.0 1.0 1.0 1.0 1.0 Trimethylene bis(p-aminobenzoate) 1.0 1.25 1.5 1.75 2.0 PROPERTIES
Modulus, MSI 0.49 0.48 0.51 0.53 0.54 Strength, KSI 19.0 18.8 20.4 22.7 23.1 Strain, ~ 4.3 4.5 4.9 5.5 5.4 Work-to-break, in-lbs./in3 449 451 560 728 729 The beneficial effect provided by increasing the ratio of amine equivalents to epoxide equivalents is seen from these data.

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1 326~30 The general procedures of Example 1 and Example 25-29 are repeated, including diaminodiphenyl sulfone (DDS) as a co-curing agent and increasing the ratio of the during agents to epoxide, as was done in Examples 25-29. The formulations used and the results obtained are shown in Table No. 8:

TABLE No. 8: INCREASING THE AMINE/EPOXY RATIO

j EXAMPLE 30 31 32 33 34 35 '~ COMPOSITION (equivalents) N,N,N''~N'-tetraglycidyl-4,4'-d~m~nodi~yl me~ l.0 1.0 1.0 1.0 1.0 1.0 ' Diaminodi~henyl sulfone 0.5 0.5 0.5 0.5 0-5 0-5 T~imethylene bis-~p-aminobenzoate) 0.75 1.~ 1.25 1.50 1.75 2.0 PROPERTIES
~, .
Modulus, MIS 0.51 0.50 0.54 0.57 0.60 0.60 Strength, KSI 20~8 21.0 23.0 27.3 26.7 29.9 Strain, % 4.8 5.0 5.06.8 5.7 7.4 '~ Work to break, in.-lb./in.3 545 592 6551156 915 1~76 '', The beneficial effect on properties resulting from an increase in the ratio of amine equivalents to epoxide equivalents again is demonstrated.
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~isphenol A diglycidyl ether plus oligomers (EPON~ 828, Shell Chemical Co.) was mixed with trimethylene bi~p-aminobenzoate) at a ratio of 1.0 epoxy equivalents to 0.75 amine equivalents twt- ratio:
94.9 g. to 30.1 g.). The resin was coated onto graphite fiber (CELION~ 6K high strain graphite fiber) and cured into unidirectional 8 ply laminates by heat-ing at 350F. for 2 hours. The interlaminar strain energy release rate was 5.0 in.-lb.~in.2.

Bisphenol A diglycidyl ether and oligomers (DER~ 331, Dow Chemical Co.) was mixed with N,N-dimethyl ` 15 trimethylene-bis(p-aminobenzoate) at a ratio of 1.0 ¦ epoxy equivalents to 0.75 NH- amine eguivalents (weight ratio: 75.9:52.3 g.). ~he resin was coated onto graphite fabric (CELIONO 3K70, plain weave) and cured to a 10 ply laminate by heating at 35~ F. for 2 hours.
20 Good quality laminates were produced.

,~, 3 A mixture comprising tris(4-glycidoxyphenyl) ~ 25 diglycidylmethane ~80 parts, Dow Chemical XD-7342), i! bisphenol A diglycidylether ~20 parts, Dow Chemical DER0 331), trimethylene bis(p-aminobenzoate), 38 parts, dicyandiamide, 2 parts, and the reaction product of 2,4-toluene diisocyanate and dimethylamine, 2 parts, all by weight, wa~ prepared and applied to CELION~
high strain graphite fibers and made into an 8 ply ~l unidirectional laminate. It had a compression strength of 20.9 x 103 p8i at 7~ F.

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1 326q30 _35 EX~MPLE 39 Tris-4 glycidoxyphenyl) methane (Dow Chemical, XD-7342) was mixed with N,N'-dimethyl-trimethylene bis(p-aminobenzoate) at a ratio of 1.0 epoxy equivalents to 0.75 amine equivalents (weight ratio: 69.ag: 55.2g). The resin was coated onto graph-ite fabric (CELION~ 3K70, plain weave) and cured into a 10-ply laminate, by heating at 350F. for 2 hours.
Good quality laminates were produced.
, .
~: EXAMPLJ3 4 0 ,, An epoxylated novolac (Dow Chemical DEN~ 438) ; 15 was mixed with trimethylene bis-(p-aminobenzoate) at A a ratio of 1.0 epoxy equivalent to 0.75 amine equiva-lents (weight ratio: 78.9:26.1 g). The resin was coated onto graphite fabric (CELION~ 3X70, plain weave) and cured into a 10 ply laminate by heating at 35~ F.
20 for 2 hours. Good quality laminates were produced.

The procedure of Example 40 was repeated, 25 ~ub~titutinq for the polyamine, N,N'-dimethyl-trimethylenebi~(p-aminobenzoate) (weight ratio : 72.7 g.
epoxy : 52.3 g. diamine). Good quality lamintes were produced.

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Bisphenol A diglycidyl ether (DER~ 331, Dow Chemical Co.). was mixed with 1,3-trimethylene aminobenzoate) at a weight ratio of 94.9 epoxide: 30.1 g.
diamine . ~he resin was coated onto polyaramid satin weave fabric (DuPont REVLARO2aSR) and cured into a six ply laminate , by heating at 35~ F. for 2 hours.
s~ Good quality composites were obtained.

~;
The procedure of Example 42 was repeated, substituting for the polyamine, N,N'-dimethyl trimethylenebis-(p-aminobenzoate) (weight ratio 75.9 g.
q- epoxy : 52.3 g). Good quality composites were obtained.

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The procedure of Example 42 was repeated, $~ except that the the resin mixture was coated onto nickel plated graphite fibers instead of polyaramid cloth. The matrix composition was cured into 1~4" x 10~ x 1/8" composite rods by heating at 35~ F. for two hours. Good quality composites were obtained.

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The procedure of Example 43 was repeated, except that the resin mixture was coated onto nickel plated graphite fibers instead of polyaramid cloth. The matrix composition as cured into 1/4" x 10" x 1/8"
composite rods by heating at 35~ F. for two hours. Good quality composites were obtained.

A resin compo ition is prepared by mixing the following (by weight) ., .
(a) N,N,N',N'-tetraglycidyl-4,4' diamino diphenyl methane 120 parts (b) Polyether polyimide resin (General Electric Ultem, Example 11, above) lS parts (c) trimethylene bis-p-amino-benzoate) 48 parts (d) Boron trifluoride-ethylamine , complex (catalyst) 0.5 parts ,~
A prqpreg tape is prepared following the general procedure of 6-8, with a 35 to 45 preferably 40% resin/
~, 55 to 65, preferably, 60% graphite loading. When this is formed into laminates by the procedure of Examples 6-8, excellent quality composites are produced. Preferred range-~ of compositions are (a), 114-126 parts; (b), 14.25-15.75 parts; (c) 45.6-50.4 parts; and (d), 0.475-, 0.525 parts.

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1 326q30 ! It is seen that the present invention produces articles of manufacture with beneficial properties, making them useful in a variety of applications. Many variations will suggest themselves to those skilled in this art in light of the fore-going detailed description. All such obvious variations are 3 within the full intended scope of the appended claims.

.'i

Claims (4)

1. A heat-curable epoxy resin composition comprising a siliceous reinforcement filament and (i) an epoxy prepolymer or combination of prepolymers having more than one epoxide per molecule, and (ii) an amount effective to promote cure of an amine-functional curing agent or combination of curing agents selected from those of the formula:

wherein R1 is hydrogen or methyl, and z is an integer of from 2 to 12, with the proviso that when R1 is hydrogen, the amine-functional curing agent is not present in greater stoichiometric amounts than the epoxy prepolymer.

2. A composition as in Claim 1 wherein, in component (ii), z is 3.

3. A composition as in Claim 2 wherein, in component (ii), R1 is methyl.

4. A composition as in any one of Claims 1, 2, or 3 wherein said reinforcing filaments comprise glass filaments.