CA1271867A - Curable epoxy resin composition - Google Patents

Abstract

ABSTRACT

Curable compositions comprising epoxide pre-polymers and polyaminobenzoates, alone, or combined with reinforcements, e.g., graphite fibers, and, option-ally modified with second resins. The cured resin fiber matrix compositions exhibit high toughness combined with excellent hot/wet strength.

Description

~i~'71~i7 ~`

28,954 CURABLE EPOXY RESIN COMPOSITIONS

FIELD OF THR INVENTION

This invention relat::c~; t:o improved epoxy resin cvmpositions. In addition, it rclates to curable epoxy rcsin compositions comprising reinforcing filaments and epoxy prepolymers combined with aromatic polyamine curing agents.

'71~7 BACKGROUND OF THE INVENTION

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 clllbs have also adopted fiber resin materials successfully.
lS
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.K. 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-~', 1~ 7 ings and glass-reinforced laminates. There is no indication in the properties presented in the U.K.
Patent that the curing agents exemplified therein will produce the combination of toughness and strength under 5 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., ~2 ~ ~--(CH2)n~~C ~ NH2 wherein n is an integer from 2 to 12. This '360 patent 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 curcd with diamines of the immediately preceding formula (n is 3), are described 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 comprisino an epoxy prepolymer and a novel family of aromatic polyamine curing agents. No member of this novel family of curing agents is specifically exemplified in the U.K. Patent. The invention provides neat resin formulations having, after cure improved physical ~ '71~3~i7 properties, e.g., higher elongation and satisfactory hot/wet modulus. The epoxy compositions of the present invention, cured with filaments, exhibit improved inter-laminar toughness and residual compression strength after impact, while maintaining compression strength under hot/wet conditions.

SUMMARY OF THE INVENTION

10 It is an object of the present invention to provide improved epoxy resin compositions.

It is a further object of the present invention to provide a fiber matrix composition that affords satisfactory compression strength over known matrix formulations, especially under hot/wet conditions, and improved compression strength after impact.
These and other objects are accomplished herein by a composition comprising:
(a) non-siliceous reinforcing filaments, and (b) a heat-curable epoxy resin composition comprising:
(i) an epoxy prepolymer or combination of prepolymers having more than one epoxide group 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:
/ NHR\
xto~

a ;7 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-, with the proviso that the curing agent is not

2 ~ ~ ~ O-C { ) NH2 present in greater stoichiometric amounts than the epoxy prepoly-mer.
In a~other aspect, the present invention contemplates fiber reinforced heat-curable epoxy resin compositions comprising a non-sil$ceous filament reinforcement and (i) an epoxy prepolymer or combination of prepolymers having more than one epoxide group 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:

RlHN-~ C (CH2 ) Z O C ~_ NHRl 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 inven-tion to provide such compositions in filled and/or reinforced, ~' - 6a - 61109-7316 e.g., glass fiber reinforced, embodiments which are useful as prepregs, for example, to make laminates and other structural shapes in accordance with procedures known in this art.

71~j7 In another preferred feature of the invention, resin fiber matrix compositions will comprise:
(a) reinforcing filaments, and (b) a heat curable epoxy resin composition formed of the following materials:
(i) N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl methane, e.g., 50 to 100, preferably 75 to 85 parts by weight;
(ii) tetraglycidoxy tetraphenylethane, e.g., 0 to 50, preferably, 15 to 25 parts by weight;
(iii) trimethylene bis-(p-aminobenzoate), e.g., 28 to 60, preferably 35 to 45 parts by weight;
iv) fumed silica, e.g., 0-12, preferably 5 to 7 parts, by weight, and (v) the reaction product of toluene-diisocyanate and dimethylamine, e.g., 0.1 to 2.5 preferably 0.5 to 1.5 parts by weight.
The fiber resin matrix composition is uniquely suitable for use with an interleaf material to prepare a mechanic-ally superior cured structure.
Still another preferred aspect, the present invention provides compositions of epoxy resins and the above-mentioned dimaine curing agents which also include a second resin in an amount sufficient to impart improve-ments in mechanical properties, especially toughness, while preserving substantial resistance to failure under hot/wet conditions. Such resins can be present homogene-ously and also in the form known as interpenetrating polymer networks. Particularly useful in this aspect are resins which include repeating units oi the iormula:

o . I

~ { O ~ O-CH2-CH _ C~2_ n and those with repeating units of the formula:

L ~ 13 ~

wherein n is a number sufficient to provide a molecular weight of 20,000 to 60,000. Amounts of 5 to 30, preferably 10 to 20 parts by weight per 100 parts by weight of epoxy prepolymer can be used.

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.

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-1~ pounds with the polyamines of the above-mentioned formula in conventional quantitative ratlos, 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 300C., 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.

Fillers, pigments, dyes, reinforcements, such as 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 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 d~nding high stiffness to weight ratio or shear strength, carbon fibers, graphite filaments, polyaramid filaments or nickel-plated graPhite filaments, as dis-closed in assignee's copending Canadian application No.

", ~1 423,551 are m~st preferred.
The epoxy resins suitable for the present inven-tion are compounds having more than one epoxide group per molecule a~ailable for reaction with the primary and secondary polyamines of the present invention (described infra.). Such epoxy prepolymers include but are not limited to polyglycidyl ethers of polyvalent phenols, for example -- pyrocatechol; resorcinol; hydroquinone; 4,4l-dihydroxy-1~ diphenyl methane; 4;4'-dihydroxy-3,3'-dimethyldiphenyl methane; 4,4'-dihydroxydiphenyl dimethyl methane; 4,4'-dihydroxydiphenyl methyl methane; 4,4'-dihydroxydi-phenyl cyclohexane; 4,4'-dihydroxy-3,3'-dimethyldi-phenyl propane; 4,4'-dihydroxydiphenyl sulphone; or 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, in the presence of acid catalysts); polyglycidyl ethers of diphenols obtained by esterifying 2 mols of the sodium salt of an aromatic hydroxycarboxylic acid with 1 mol. of a dihalogenoalkane or dihalogen dialkyl ether (U.K. 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.K. 1,024,288).

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,q'-diaminodiphenyl methane; and N-diglycidyl-4-aminophenyl glycidyl ether. Special mention is made ~ ,e I
." " ~

of N,N,N',N'-tetraglycidyl-1,3-propylene bis-4-aminobenzoate.

Glycidyl esters and/or epoxycyclohexyl 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 1~ 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, 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, for example of bis mercaptomethylbenzene; and diglycidyl-trimethylene sulphone, are also suitable.

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

3 0 ~G ~o) ~7~

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 ~ (CH2)x ~ O~ ~ )2 wherein x is an integer from 1 to 4, available commerci-ally (where x=l) as Araldite MY-720 (Ciba-Geigy) I:C{(~)_O/~o) ~ available commercially as XD7342*(Dow Chemical);

10 o~Ao ~ ~0~0 c~3 available commercially as DER331*(Dow Chemical) or EPON 828 (Shell);

~0 )_~

o~ ~0 ~ ~

available commercially as EPON ~ 1031 (Shell);

*Trademark 71~

5 X~ )Y -~ ) ' ~)Y
2 f ~ ~ ~

~ n wherein Y is 1 or 2, X is -O- or -N-,R is H or C~3 and n is 2 to 8.

Compounds in which X is -O- are available as - a mixture under the trademark DEN-438 from Dow Chemical Company.
Also,preferred are triglycidyl ethers of meta- and para-hydroxyaniline, e.g., represented by the formula:

o ~ ~ N ~
These are available under the 'trademark ARALDITE~ 0500, 0510 from Ciba-Geigy.
The polyamino curing agcnts arc of the formula:

1~

,3 5 A~
. .. ` J

1~'71~tj7 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 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-ing to the above formula in which R is hydrogen, Cl-C3 alkyl, or phenyl and X is a divalent or trivalent 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~

-C~l2 ~)-CH -, ~'7~

~ C)H3 -CH2 ~ ~ 2 ' CH2-CI-CH2- , or (2) \___J CH3 a trivalent group consisting of -N- and - (CH2) -CH-(CH2)m- , wherein n and m are the same or different integers froln 1 to 4.

More preferred curing agents are the following:

H2N- ~ -C-O-(CH )-O-C- ~ NH2, wherein z is an integer of from 2.to 12, preferably 2 to 6, ~ C-o-(cH2)z-o-c ~

wherein z is an integer from 2 to 12, prefera~ly 2 to 6, 2 ~ -C-o-Y-O-C ~ NH2 ~ wherein Y is -cH2cH2ocH2cH2ocH2c 2 i7 _ 18 --(~-C-~-, -CH2-(~>-CH2- ' CH2 O 2 ' CH3 : or CH2_o_C_(~NH2 CH2_o_C_<~_NH2 CH-O-C-<~NH2 ; CH-O-~ NH2 (CH2 ) C 'H 2 -0-C-~>-NH2 CH 2 -O-C-~NH 2 ~ O-C~ ~3 H C-N-~C ( 2)z ~N-CH3, wherein o z is an integer of 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 ~ -O-(CH2)z~O~C ~ NHRl 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, and the like.

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 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 substratesuch as release paper 14 and passed through the pressure roller assembly 8. ~elease 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 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.

~ 7~7 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 fiber 2 and resin layer 10 to the pressure rollers 8 is selected to produce a fiber matrix of about twenty to sixty weight 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.

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

The following procedure is used to prepare and cure neat resin compositions: the epoxide pre-polymer and the polyamine component are mixed at 135~C.
for 10 minutes, and cooled to 1~0C, the catalyst, if any, is mixed in, and the mixture is degassed for 10 minùtes. 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 23C. The formulations tested and the results obtained are set forth in Table I:

~;~'7~ 7 o U~o U~
U')I II ~ o o o oo co ~ r- ~ In o ~r I o -- o ~ ~r oo ,~
Ul ~ ~ o o ~¢ O ~ O
O o co ~ ~ ul~ o a~
1~) 1 o o o ~1 ~) ~I
U~ O o H

E~ ,_ ~ o ~D
# c~ ~

4 ~ I O Or l t~
~ O O
~ u~ ~ o a~~ ~
a o ,~ . . O ~
i~ ~ I ~ o,_,O O ~ CO
U~
z OH U1 ~ O
E~ ~ I` ~ o l_ , I. I I _. ~ ~r 1`
cq ~ _l O ~10 0 ~ ~r o O u~ ~1 ~ O O
V o ~ u~, ~ . . o r~
. I . ~ I . a~ ~ ,1 ~1 ~ I o o o ~ ~r V
u~ ~

~ ~ o ~ ~ . . o 1`
Z ~1 I I II ~ ~ ~ a~
H ~ O O
o ~ ~ I
X
O ,1: ~ ~

~ _ ~ o ~ 3 r~ ~ ~a ~ ~ ~
~1) ~r l .~ ~ ~ ~ QJ ~ E3 ~1 ~ h ,~ ,~ v 3 ~v ~v ~a ~v v " ~ o o m ,~ tJ~ N ~v t7' I~ 15 H U~ la .
_ ~ ~ X ~ r~ O rv ~ O
~ ~ o a) ~ o ~ ` ~,~P ,4 Z " ~, ~v .C ~`.C r~ `.C I
O I ~ ~r~ U~ ~ ` O U~ 1:
t~l rr~ rv r-l r-~ ~ a) al 115 U~ ~1 ~ O
E~ - v ~, ~v ~, ~ e ~ ~ ~ ~ H ~ I ~ O ~) ~1 H O r-l O S ~ ~r-l Q. O rv r~l E ~ ~ aJ Id ~ I
~ u~ ` ~ v~ ~ J ~ a-- ,~ o ~ P~ ~a ~ #
O ~ ,a ,~ ~ I I ~ ~ ~ ~o ~ ~ o ,~ v~
E~ P~ ~ ' ~ 3 N - Ulv ~r~ ~ 3 E-~
7 I~ rl ~ Z~ d r-l~v O
x o ~ a-- ~;
~ o z~a ~ a E~

o 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 properties are decreased only 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~ 6K high strain graphite 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.).

*Tra~rk ~5 ,, ~
~ A.~bJ

1;~'71~

Using an apparatus shown generally in Fig. 1, prepreg tapes of the structure shown generally in Fig.
2, were prepared:

(28%) Resin mixture (parts by wei~ht) N,N,N'N'-tetra(glycidyl-4,4l diaminodiphenyl)methane 80 80 80 Tetraglycidoxy tetraphenylethane 20 20 20 Trimethylene bis-(para-aminobehzoate) 44 44 65 Diaminodiphenyl sulfone -- -- 20 Polymer modifier* -- 5 --Catalyst Fumed silica 6 6 6 (72%) Filament(parts by weight) (6K graphite fibers having a strain to failure of about 1.5%) * BLENDEX 311, Borg-Warner Co (Trademark) These samples were cured and compared against commerical epoxy resin matrixes~ The sheets of resin involved were as follows:
Uni-Comp : 8 sheets [0]
Quasi-Comp : 16 sheets[(+45/0/90)2]S
Comp./lmpact: 36 sheets.[(+45/0/90/0/90)2_ /+45/0/-90/+45]s ~.

~ 7 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 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 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:

H 1 ~ 7 ~ 7 E~
Z
~1 ~
U~
~ ~ ~ Ul o o H 1:4 1 ~1 ~`1 ~D ~1 U~ ~ ' (~ ~) 1~) ~ N N
U~ H ~:
O
~ E~ o O ~ In O

H o U~ ~ ~ ~ ~ ~ ~ U~ I o~ ~ I
0~ a~ a~ r~ ~ ~ r~ ~r I r~
H .IJ
C~
~D ~1 ~ I r~ IN I 1 ~7 1 1 t~l c~ I oo I a~ I I co I I ~_ O
~r ~r o a) 3 h ~ ~ O In ~D 00 0 ~1 0 m z r) O ~ ~ ~ r~
~¢ :~ ~ ~
~ _ C~ ~ ~ ~
CJ~ O .~ ,a I o I O I I
I ~ I ~ I I ~1 1 1 ~
o o m a n u~
a) ~
~ G) OH O
E~ * ~ a a zo ~ 3 ~ 3 ~) 3 ~ ~ 3 ~ 3 h c~ a) O O

u ~ o a) ~"a 8 8 ~ o~
o o o ~C ~z C~z C~z 71 ~i7 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-ll Using the general procedure of Example l, compositions were prepared and tested. The formulations used, and the results obtained are set forth in Table 3.

~1 o o o o ~n H
Q o ~; o o ICO o I I o ~ ~ ~r z cn Y

O o ~ o~ I o I o~ o I ~ I Z
~ / \
U) o=~ >=o o ~ a) O o X --I ~ 1 o X
~ o ~ ~ .. ~ u . ~
.. 3 ~ ~0 1 5~ L ~J, ~ ~ .4 ~ ~ -- _ ~ ~ Q~ ~
Ul ~ o ~ ~ ~
m ~ ~ * o ~l ~ ~ ~ .-7 ~ ~" o s~ ~ m ~ ~ ::
E~ ~ ~ ~ 1 ~ ~c~--~ I~
~ ~ ~ ~ ~ 0 ~ I
_ ~ s ~ o o ~
~ C~ ~ \ ai r Z ~ ~ ~ ~ _ ~. _~
o ~ a) ~ ~
H ~ ~1 ~ 'a ~ ~ ~ rl 1~ O ~ , t~) i E~ ~ o O ~ ,~~ ~ ,Y
1~ H Z ~ C:
~ U~ ' ~ ~ lt _~ \
o z ~o ~ ~ I I ~ o- J~=o ~3 O ~ o 3 o c~ Z a E~ m 1~7~

~29-o ~-1 0 ~ O r`
~ ~ CO ~
O ~ o o ~`I ~ In o t.q H
C: o u~
U~ ~ . . U~
O . U~
H H O o ~ 0~ O
V~
~r:
E~
V~
O ~ ~ I` a~ U~
u~
~ . . ~I~
H cn I O O
O ~
~ . I

o .. ~
3 ~,~ h U~ 0 `
dP
U~~o ~ ` O--~1 ~ ~ ~ I ~ o w ~ ~ 0 .
O ~ ~ O
f~ S~ 3 1~ 71~367 - 30_ 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 150F. for 1 hour and 350F. for two hours. Compressive 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, methylene dianiline bismaleimide. The formulations used and the results obtained are set forth in Table No. 4.

'71~67 o 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 maleimide * 5 10 15 20 PROPERTIES
.
Modulus, MSI dry 0.46 0.48 0.47 0.49 Strength, KSI dry 23.2 21.5 22.9 23.0 Strain, % dry 7.3 6.1 6.6 6.2 Work-to-break, in-lbs./in.3 dry 1070 810 910 840 Tg, C. dry 207 208 207 206 .
* o O
Il 11 ¢ N ~ CH2 ~ N ~
Il O O

EX~MPLES lB-21 Tlle general procedure of Example 1 was used to prepare and test compositions according to tllis invelltioJl, substituting different epoxy resin prepoly-mer~:

10 m-TGDDg-- (o/~ ~ N~O ,~) ~ ~ O O
l5 TGPC -- ~ ~ ) N ~ _ c tC~

o E~L-4299 -- ~ CIIzOC ~ Cl~2 ~ ~ O Cl2 ~ O

~R~DIT~ 0510-- 0 ~ o~

~Z~C~

o The formulations used and the results obtained are set forth in Table No. 5:

TABLE No. 5: EPOXY COMPOSITIONS AND PROPERTIES
EXAMPLE _ 19 20 21_ COMPOSITION (parts by weight) N,N,N'N'-tetraglycidyl 3,3'-diamino-diphenyl sulfone 100 - - -N,N,N'N'-tetraglycidyl tri-methylene bis-(p-aminobenzoate) ~ 100 Bis-(3,4-epoxy-6-methylcyclo-hexylmethyl) adipate ~ ~ ln0 100 N,N-Diglycidyl-4-aminophenyl glycidyl ether - - - 100 ~rimethylene bis (p-aminobenzoate) 5138.5 37.4 62.8 PROPERTIES
Modulus, MSI dry 0.63 0.55 *NA 0.53 wet 0.350.18 NA 0.26 Strength, KSI dry 23.0 23.4 NA 21.3 Strain, % dry 4.05.5 NA 5.6 Work-to-break, in.-lb./in3 dry 485 770 NA 740 Tg, C. dry/wet 240/223 - NA /156 * Not yet available _34 _ The general 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

COMPOSITION (equivalents) -N,N,N'N'-tetraglycidyl-4,4'-diamino diphenyl methane 1.0 1.0 1.0 N,N'-dimethyl trimethylene bis-(p-aminobenzoate) 1.0 0.8 0.6 PROPERTIES
Modulus, MSI dry 0.49 0.49 0.48 wet 0.19 0.22 0.25 Strength, KSI dry 22.8(y)* 21.7(y) 21.9(y) Strain, % dry 7.1(y) 7.1(y) 7.5(y) Work-to-break, in-lb/in.3 dry >1698 >1600 >1470 Tg, C. dry/wet 158/120 165/- 163/-* (y) = yield i;~t71867 _ 35-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 No. 7:

TABLE No. 7: INCREASING THE AMINE/EPOXY RATIO

~" COMPOSITION (equivalents) N,N,N',N'-tetraglycidyl-4,4'-diamlno diphenyl methane1.0 1.0 1.0 1.0 1.0 Trimethylene bislp-aminobenzoate) 1.0 1.25 1.5 1.75 2.0 PROPERTIES
Modulus, MSI 0.49 0.480.51 0.53 0.54 Strength, KSI 19.0 18.820.4 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.

1, 18~7 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 donQ 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

COMPOSITION (equivalents) N,N,N'~N'-tetraglycidyl-4,4'-diamino diphenyl methanel.0 1.0 1.0 1.0 1.0 1.0 Diaminodiphenyl sulfone 0.5 0.5 0.5 0.5 0-5 - 5 Trimethylene bis-~p-aminobenzoate) 0.75 1.01.25 1.50 1.75 2.0 PROPERTIES
Modulus, MIS 0.51 0.500.540.57 0.60 0.60 Strength, KSI 20 . 8 21. 0 23. 0 27 . 326 . 7 29 . 9 Strain, % 4.8 5.05.0 6.8 5.7 7.4 Work to break, in.-lb./in. 3 545 592 655 1156 915 1476 The beneficial effect on properties resulting from an increase in the ratio of amine equivalents to epoxide equivalents again is demonstrated.

~37 _ sisphenol A diglycidyl ether plus oligomers (EPON~ 828, Shell Chemical co.) was mixed with trimethylene bis(p-aminobenzoate) at a ratio of 1.0 epoxy equivalents to 0.75 amine equivalents (wt. 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. .

Bisphenol A diglycidyl ether and oligomers (DER~ 331, Dow Chemical Co.) was mixed with N,N-dimethyl trimethylene-bis(p-aminobenzoate) at a ratio of 1.0 epoxy equivalents to 0.75 NH- amine equivalents (weight ratio: 75.9:52.3 g.). The resin was coated onto graphite fabric (CELION~ 3K70, plain weave) and cured to a 10 ply laminate by heating at 350F. for 2 hours.
Good quality laminates were produced.

A mixture comprising tris(4-glycidoxyphenyl) diglycidylmethane (80 parts, Dow Chemical XD-7342), bisphenol A diglycidylether (20 parts, Dow Chemical DER~ 331), t~imethylene bis(p-aminobenzoate), 38 parts, dicyandiamide, 2 parts, and the reaction product of 2,4-toluene diisocyanate and dimethylamine, 2 parts, all by weight, was prepared and applied to CELION~
high strain graphite fibers and made into an 8 ply unidirectional laminate. It had a compression strength of 20.9 x 103 psi at 73F.

1~'71~367 O

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: 69.8g: 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.

An epoxylated novolac (Dow Chemical DEN~ 438) lS was mixed with trimethylene bis-(p-aminobenzoate) at 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~ 3~70, plain weave) and cured into a 10 ply laminate by heating at 350~F.
for 2 hours. Good quality laminates were produced.

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

8~i'7 _39 _ 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 . The resin was coated onto polyaramid satin weave fabric (DuPont KEVLAR~285K) and cured into a six ply laminate , by heating at 350F. for 2 hours.
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.
epoxy : 52.3 g). Good quality composites were obtained.

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 350F. for two hours. Good quality composites were obtained.

-` ` 1;~'71~36 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 l/4" x lO" x l/8"
composite rods by heating at 350F. for two hours. Good quality composites were obtained.

A resin composition is prepared by mixing the following (by weight) lS (a) N,N,N',N'-tetraglycidyl-4,4' diamino diphenyl methane 120 parts (b) Polyether polyimide resin (General Electric Ultem, Example 11, above) 15 parts (c) trimethylene bis-p-amino-benzoate) 48 parts (d) Boron trifluoride-ethylamine complex (catalyst) 0.5 parts A prepreg 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 ranges 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.

1~'71~6''~

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 variatlons are within the full intended scope of the appended claims.

~;

Claims (33)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A fiber resin matrix composition comprised of:
(a) non-siliceous reinforcing filaments, and (b) a heat-curable epoxy resin composition comprising:
(i) an epoxy prepolymer or combination of prepolymers having more than one epoxide group 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 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 -?- , with the proviso that the curing agent is not present in greater stoichiometric amounts than the epoxy prepolymer.

2. A composition as defined in Claim 1 wherein the curing agent (b)(ii) is used in combination with a second aromatic polyamine curing agent.

3. A composition as in Claim 1, wherein said non-siliceous filaments (a) comprise carbon, graphite, silicon carbide, boron, rayon, polybenzimidazole, polybenzothiazole, polyester, polyamide, polyaramid, metal-coated such filaments or a combination of any of the foregoing.

4. A composition as in Claim 3 wherein said filaments comprise graphite filaments, polyaramid filaments or nickel-plated graphite filaments.

5. A composition as in Claim 1 wherein the epoxy prepolymer (b)(i) is a cycloaliphatic poly-epoxide.

6. A composition as in Claim 1 wherein the epoxy prepolymer (b)(i) is selected from aromatic com-pounds of the formula:

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 -?-; R' is hydrogen or alkyl; and d is 1 or 2 and equal to the valence of G.

7. A composition as in Claim 6 wherein the epoxy prepolymer (b)(i) comprises a compound of the formula:

wherein x is an integer of from 1 to 4.

8. A composition as in Claim 7 wherein x is 1.

9. A composition as in Claim 6 wherein the epoxy prepolymer (b)(i) comprises a compound of the formula:

10. A composition as in Claim 6 wherein the epoxy prepolymer (b)(i) comprises a compound of the formula:

11. A composition as in Claim 6 wherein the epoxy prepolymer (b)(i) comprises a compound of the formula:

12. A composition as in Claim 6 wherein the epoxy prepolymer (b)(i) comprises a compound of the formula:
wherein y is 1 or 2, X is -O- or ?, R3 is H or CH3 and n is 2 to 8, or a mixture of the foregoing.

13. A composition as in Claim 6 wherein the epoxy prepolymer (b)(i) comprises a compound of the formula:
in combination with a compound of the formula:

14. A composition as in Claim 6 wherein the epoxy prepolymer (b)(i) comprises a compound of the formula:

15. A composition as in Claim 1 wherein R
in the curing agent (b)(ii) is hydrogen or C1-C3 alkyl;
X is a divalent or trivalent radical having a valence of selected from (1) a divalent group consisting of -(CH2)y -, wherein y is an integer of from 2 to 6;
-(CH2CH2OCH2CH2OCH2CH2) --;
a trivalent group consisting of ? and (CH2)m-, wherein n and m are the same or different integers from 1 to 4.

16. A composition as in Claim 15, wherein said curing agent (b)(ii) is selected from compounds of the formulae:
, wherein z is an integer of from 2 to 12;
, wherein z is an integer of from 2 to 12;
, where Y is -CH2CH2OCH2CH2OCH2CH2-, ; or ; and , wherein n is an integer of from 2 to 12.

17. A composition as in Claim 16 wherein said curing agent (b)(ii) comprises a compound of the formula:

.

18. A composition as in Claim 17 which additionally includes a compound of the formula:

.

19. A composition as in Claim 16 wherein said curing agent (b)(ii) comprises a compound of the form-ula:

.

20. A composition as defined in Claim 16 wherein curing agent (b)(ii) comprises a mixture of a compound of the formula:

and a compound of the formula:
.

21. A composition as in Claim 1 wherein component (b) comprises materials with the following parts by weight allocation from about 50 to 150 parts (b)(i), and from about 28 to 60 parts (b)(ii).

22. A composition as in Claim 1, which addi-tionally contains (b)(iii) a filler.

23. A composition as in Claim 22 wherein the filler (b)(iii) is fumed silica.

24. A composition as in Claim 1 which also includes (b)(iii) a small effective amount of a curing catalyst.

25, A composition as in Claim 24 wherein the catalyst (b)(iii) comprises the reaction product of toluenediisocyanate and dimethylamine or the reaction product of boron trifluoride and an amine.

26. A composition as in Claim l which also includes a minor, effective, property-modifying amount of a bis-maleimide compound or a styrene-butadiene-acrylon-itrile core-shell polymer.

27. A composition as in Claim 26 wherein the bismaleimide compound is of the formula:

28. A heat-curable epoxy resin composition comprising a non-siliceous filament reinforcement and (i) an epoxy prepolymer of 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.

29. A composition as in Claim 28 wherein, in component (ii), z is 3.

30. A composition as in Claim 29 wherein, in component (ii), R1 is methyl.

31. A composition as in Claim 28 wherein said reinforcement comprises reinforcing filaments.

32. A composition as in Claim 31 wherein the reinforcing filaments are non-siliceous filaments.

33. An article of manufacture comprising a plurality of layers of a fiber-resin matrix composi-tion as defined in Claim l consolidated under heat and pressure.