Note: Descriptions are shown in the official language in which they were submitted.
1(;?371~8
This invention relates to a method of modifying
curable epoxy resins by vulcanization and to vulcanized
epoxy resins having improved high temperature adhesive
properties and, in some instances, improved room temperature
adhesive properties.
More particularly, the invention provides curable
epoxy resin compositions havi~g more than one vicinal epoxy
group per molecule, modified by reaction with from .03 to
.2, preferably from .08 to .12, parts by weight per part
of epoxy resin of polymer of butadiene and acrylonitrile,
methacrylonitrile or mixtures thereof, said polymer having
pendant reactive groups selected from COOH, OH and SH, and
containing from 70 to 90, preferably from 80 to 85, percent
by weight of butadiene and from 10 to 30, preferably from
15 to 20, percent by weight of acrylonitrile or methacrylo-
nitrile, said epoxy resin characterized in that the
modifying polymer is vulcanized with from 1.5 to lO parts
by weight or from 3 to 15 parts by weight, respectively,
: of an organic peroxide or sulfur, per 100 parts by weight
of the reactive polymer modifier, at a temperature of from
120C to 160C for from l.0 to 3.0 hours.
The invention also provides a method of modifying
a curable epoxy resin having more than one vicinal epoxy
group per molecule by reaction of said resin with from 0.03
to 0.2 parts by weight, based on the weight of epoxy resin,
of a polymer of butadiene and acrylonitrile, methacrylo-
nitrile or mixtures thereof, said polymer having pendant
reactive groups of COOH, OH or SH and containing 70 to 90
weight percent butadiene and 30 to 10 weight percent
acrylonitrile or methacrylonitrile, characterized by
.... ~, ~^''
16,540-F -1-
1037~88
vulcanizing the modifying polymer with from 1.5 to 10
parts by weight or from 3 to 15 parts by weight, respec-
tively, of an organic peroxide or sulfur, per 100 parts by
weight of the reactive polymer modifier, at a temperature
of from 120C to 160C for from 1.0 to 3.0 hours after
reaction of the polymer with the epoxy resin.
The polymer modified solid epoxy resins of the
present invention are conveniently prepared by mixing a
liquid epoxy resin with the palymer modifier and a dihy-
droxyl-containing compound and heating in the presence of a
suitable catalyst to cause reaction between the liquid epoxy
resin and the reactive groups of the polymer modifier and
with the dihydroxyl-containing compound. Then the resultant
product is vulcanized with sulfur or an organic peroxide.
Suitable catalysts include those normally employed
in the preparation of epoxy resins from polyepoxides and di-
hydroxyl-containing compounds such as, for example, tertiary
amines, quaternary ammonium compounds and phosphonium com-
pounds. Such catalysts and procedures are well known in the
art.
Alternatively, the liquid epoxy resin can be pre-
reacted with the modified polymer compound and then the resul-
tant product can be reacted with a dihydroxyl-containing com-
pound and this product subsequently vulcanized to produce the
resultant vulcanized, polymer modified solid epoxy resins
of the present invention.
The quantities of liquid epoxy resin and dihydroxyl-
-containing compound which are employed to produce a solid
epoxy resin are well known in the art.
The preparation of the polymer modified solid epoxy
resins can be carried out at temperatures from 110C to
16,540-F -2-
. .
103~188
150C, preferably from 130C to 140C, and subsequently
vulcanized at temperatures of from 120C to 160C, pre-
ferably 140C to 150C. The time to complete each reaction
is, of course, dependent upon the temperature, but each
reaction can usually be completed within from 1 to 3,
preferably from 2 to 2.5, hours.
Suitable organic peroxides which may be employed.
as vulcanization agents include, for example, aliphatic
peroxides such as, for example, di-t-butyl peroxide, t-butyl
hydroperoxide and aromatic peroxides, such as, for example,
dicumyl peroxid.e, t-butyl-cumyl peroxide, methyl cumyl
peroxide, mixtures thereof and the like.
The organic peroxide vulcanization agent is
' employed. in quantities of from 1.5 to 10, preferably from3 to 4, parts by weight per 100 parts by weight of the
reactive polymer modifier employed.
I
' The sulfur vulcanization agent is employed in
quantities of from 3 to 15, preferably from 9 to 11, parts
by weight per 100 parts by weight of the polymer modifier
~ 20 employed.
; Suitable liquid epoxy resins which can be employed
in the present invention include but are not limited to
those represented. by the following formulas.
A. O X X
25CH2_cH_cH2 ~ o ~ A ~ O-CH2-CH-CH2 ~ 0
X X OH
CH2-CH-CE~2-O~A ~ i
16,540-F -3-
1037~88
wherein A is a divalent hyd.rocarbon group having from 1
to 6 carbon atoms,
O O O
.. .. ..
-S-, -S-S-, -S-, -S-, -C-, or -0-;
o
X is hydrogen or a halogen atom such as chlorine or
S bromine; and n is an integer having an average value of
from about 0 to about 5.5.
B. O O
CH2-\H-CH2 / \
O ~R O
0 ~C ~H
X X R X X m
~ wherein m has an average value of from about 1.01 to about
: 5~ preferably from about 1.05 to about 4; each X is
. ind.ependently hydrogen, halogen, such as chlorine or
bromine, or an alkyl group of from 1 to 4 carbon atoms and
each R is independently hyd.rogen or an alkyl group of from
l to 4 carbon atoms.
Suitable dihyd.roxy compound.s which can be employed
to prepare the polymer modified solid epoxy resins of the
present invention include but are not limited to those
represented by the general formulas:
HO ~ A ~ OH HO ~ A ~ OH
X X X X
wherein each X is independently hydrogen, chlorine or
bromine, and A is a d.ivalent hydrocarbon group having from
.~ l to 6 carbon atoms,
16,540-F -4-
iO37~8
o o o
.. .. ..
-S-, -S-S-, -S-, -S-, -C- or -0-
o
OH
X ~ OH ~
X X OH
wherein each X is independently hydrogen, chlorine,
bromine or an alkyl group having from about 1 to 6 carbon
atoms.
Suitable reactive polymer modifiers which may
be employed include acrylonitrile-butadiene polymers,
methacrylonitrile-butad.iene polymers, or acrylonitrile-
methacrylonitrile-butadiene polymers, mixtures thereof
and. the like which also contain terminal or pendant reactive
-COOH groups, -OH groups or -SH groups. Suitable polymers
have average molecular weights of from about 2,000 to about
20,000, a reactive group functionality of from 1.2 to 5,
preferably from 1.7 to 2.4, and contain from 10 to 30, pre-
ferably from 15 to 20, percent by weight of acrylonitrile,
methacrylonitrile or mixtures thereof.
; These polymers are known in t:he art and. can be
prepared by any suitable process for polymerizing ethyl-
enically unsaturated compounds and such processes usually
employ free radical catalysts such as 4,4'-azobis(cyano-
valeric acid), azobisisobutyronitrile and. the like. Pend.ant
or terminal COOH groups can then be converted to an -OH or
-SH group if desired.
Another method. is to employ ethylenically un-
saturated monomers containing -COOH, -OH or -SH groups in
the initial polymerization. Suitable such monomers include,
16,540-F _5_
lQ37~88
for example, acrylic acid., methacrylic acid, allyl
alcohol, allyl mercaptan, mixtures thereof and the like.
The modified epoxy resins of the present invention
can be employed in adhesives, coatings, laminates and the
like.
The mod.ified epoxy resins of the present invention
can be cured with the usual curing agents or curing
catalysts for epoxy resins including primary, secondary,
and. tertiary aliphatic amines, aziridines, polycarboxylic
acid.s and. anhydrides thereof, Lewis acids, polythiols,
dicyandiamid.es, aromatic amines, mixtures thereof and the
like. The curing agents or curing catalysts may be employed
in quantities known in the art and the curing agents are
usually employed in quantities of from 80% to 200% of the
theoretical stoichiometric quantity.
The modified epoxy resins of the present invention
can be employed.with the usual modifiers and additives
including fire retardant agents, pigments, dyes, flow control
agents, curing accelerators, fillers, mold release agents,
mixtures thereof and the like.
Example 1
A. Preparation of Modified Solid Epoxy Resin
Vulcanized. With DicumYl Perox de
To a reaction vessel equipped with stirrer and
temperature control means, was added 15 grams of a butadiene-
acrylonitrile polymer containing 1.85 carboxyl groups per
; molecule, 18~8% by weight of acrylonitrile and an average
molecular weight of 3,500, 150 grams of the diglycidyl
ether of bisphenol A having an epoxid.e equivalent weight of
about 190 and 43 grams of bisphenol A. The mixture was heated
to 100C and .3 gram of tetrabutyl phosphonium acetate-acetic
16,540-F -6-
~037~8B
acid complex catalyst as a 70% solution in methanol was
added. The mixture was heated at 140C for 30 minutes.
This 30 minute interval was to permit the carboxyl groups
to react with the epoxy. After 30 minu~es .5 gram of dicumyl
peroxide was added. The reaction temperature has usually
started to exotherm prior to addition of the peroxide and the
exotherm continues to a temperature of approximately 180C.
The temperature was then maintained at approximately 160C
for 2.5 hours to complete the reaction between the epoxy
resin and the bisphenol A. The resultant modified solid
resin was light yellow in color and had an epoxide content
of 7. 8~o (EEW 555) and a ~urran's softening point of 70C.
B. Preparation of Modified Solid Epoxy Resin
Vulcanized With Sulfur
To a reaction vessel equipped with stirrer and
temperature control means was added 15 grams of a poly-
butadiene-acrylonitrile polymer containing 1.85 carboxyl
groups per molecule, 18. 8% by weight of acrylonitrile and
an average molecular weight of 3J500, 150 grams of diglycidyl
ether of bisphenol A having an epoxide equivalent weight of
about 190 and 43 grams of bisphenol A. The mixture was
heated to 100C and .3 gram of tetrabutyl phosphonium
acetate-acetic acid complex catalyst as a 70/O solution in
methanol was added. The mixture was heated at 140C for
30 minutes. This 30 minute interval was to permit the
carboxyl groups to react with the epoxy. After 30 minutes
1.5 grams of sulfur was added. The reaction temperature has
usually started to exotherm prior to addition of the sulfur
and the exotherm continues to a temperature of approximately
180C. The temperature was then maintained at approximately
160C for 2.5 hours to complete the reaction between the
16,540-F -7-
103~1W
epoxy resin and the bisphenol A. The resultant modified
solid resin was light yellow in color and had. an epoxide
content of 7~/O (EEW 544) and a Durran~s softening point
of 70C.
C. Preparation of Mod.ified.Solid Epoxy Resin Without
Vulcanization (For Comparative Purposes)
The reactants and. procedure of Part A above was
repeated except that the dicumyl peroxide was omitted. The
resultant solid epoxy resin was white opaque in color and
had an epoxide content of 8.~/o (an average epoxide equivalent
weight, EEW, of about 525) and a Durran's softening point
of about 69C.
D. PreParation of Adhesives From A, B and C PrePared Above
The following adhesive formulation was melt mixed.
and applied to aluminum, Type 2024 T-3 strips. Two such
strips were overlapped. 1/2 inch and cured at 175C for about
1.5 hours. The resultant test strips were tested accord.ing
to ASTM D-1002-64 at 77F and 250F. The results are given
in Table I.
Ad.hesive Formulation
20 grams of solid epoxy resin prepared
in A, B or C.
lO grams of aluminum powder
0.4 grams of colloidal silica
0.6 grams of d.icyand.iamide
TABLE I
EPOXY Resin EmPloYed Tensile Shear Strenath, PSi
77 F. 250F.
A (vulcanized with
dicumvl peroxide) 6450 3300
B (vulcanized with
sulfur) 5750 1500
C (unvulcanized) 5680 1100
16,540-F I -8-
. . .
~037~88
Example 2
A. Preparation of Vulcanized Carboxyl Containing
Polymer Modified Epoxy Resin
To a reaction vessel equipped.with stirrer and
temperature control means was add.ed. 15 grams of an acrylo-
nitrile-butadiene copolymer having an average molecular
weight of 3,400, an acrylonitrile content of l~/o and
carboxyl functionality of 2.4, and 103.5 gm of the di-
glycidyl ether of bisphenol A having an epoxid.e equivalent
weight of about 190. The mixture was heated to 100C and.
.2 gm of tetrabutyl phosphonium acetate~acetic acid complex
catalyst as a 70% solution in methanol was added. The mixture
was held at 100C for 30 minutes. This 30 minutes interval
was to permit the carboxyl groups to react with the epoxy.
After 30 minutes the temperature was raised to 145C and 18
grams of bisphenol S was added. After 5 minutes to allow
mixing of the bisphenol S, .5 gm dicumyl-peroxide was added
The reaction was continued. for one hour at 145C. The
. average EEW of the resultant solid epoxy resin was about 380.
B. Preparation of Unvulcanized Carboxyl Containing
PolYmer Modified EPOXY Resin (ComParative)
The procedure was the same as in A. above except
for the final step in that no d.icumyl peroxide was ad.ded.
The average EEW of the resultant solid epoxy
resin was about 375.
C. PreParation and Testinq of Adhesives from A and B
Adhesives were prepared from the resins prepared
in A and B above employing the following formulation.
20 grams of epoxy resin
10 grams of aluminum powder
.4 grams of colloidal silica
.6 grams of dicyandiamide
16,540-F _g_
10371~8
The adhesives were applied to aluminum strips
and cured at 175C for 2 hours, and. the lap shear strengths
at 77F and 250F were determined according to ASTM D-1002-64.
The results are given below.
Lap Shear Strenqth, psi
Epoxy Resin Employed~ 77F. 250F.
A. Vulcanized 5650 3750
B. Unvulanized 4600 2100
Example 3
A. Prepaxation of Vulcanized Mercaptan (SH)
Containinq PolYmer-Modified EpoxY Resin
To a reaction vessel equipped with stirrer and
temperature control means was added 15 grams of an acrylo-
nitrile-butadiene copolymer having an average molecular
weight of 3,000, an acrylonitrile content of 24% and
mercaptan (SH) functionality of 1.6, and 150 grams of the
diglycidyl ether of bisphenol A having an epoxide equivalent
weight of about 190. The mixture was heated. to 100C and
.16 gm of tetrabutyl-phosphonium acetate-acetic acid complex
catalyst as a 70/O solution in methanol was added. The
mixture was held at 100C for 30 minutes.
This 30 minutes interval was to permit the mercaptan
groups to react with the epoxy. After 30 minutes the tempera-
ture was raised to 145C. and..5 gram of dicumyl-peroxide
was ad.ded.. The reaction was continued. for one hour at 145C.
The resultant vulcanized polymer modified epoxy
resin was a light amber colored. liquid having an average
EEW of about 205.
B. Preparation of Unvulcanized Mercaptan Containing
Polymer Modified EPoxY Resin (Comparative)
The procedure was the same as in A above except that
the reaction was completed. after 30 minutes at 100C and no
d.icumyl peroxide was employed.
16,540-F -10-
103718~
The average EEW of the light amber liquid resin
was about 205.
C. PreParation and Testing of Adhesives from A and B
Adhesives were prepared from the resins prepared
in A and B above employing the following formulation.
20 grams of epoxy resin
13 grams of aluminum powder
1.0 gram of colloidal silica
1.0 gram of dicyandiamide
The adhesives were applied to aluminum strips and,
cured at 175C for 2 hours, and the lap shear strengths at
77F and 250F were determined according to ASTM D-1002-64.
The results are given below.
Lap Shear Strenqth. PSi
Epoxy Resin EmPloYed 77F. 250F.
A. Vulcanized 3766 1530
B. Unvulcanized 4133 1300
ExamPle 4
To a reaction vessel equipped with stirring and
temperature control means was added 150 grams of a diglycidyl
ether of bisphenol A having an average EEW of 187 and 30
grams of a carboxyl containing acrylonitrile butadiene polymer
having an average molecular weight of about 3500, containing
about 18.6% by weight of acrylonitrile and, containing about
2.7 weight percent of COOH groups and an average function-
ality of COOH groups of about 2. After degassing resultant
mixture at 80C for 15 minutes, 75 milligrams of tetrabutyl
phosphonium acetate-acetic acid complex catalyst was added
and the reaction conducted at 120C for 2 hours.
16,540-F -11-
103~
Then 60 grams of the resultant unvulcanized product
was removed~ and for the purposes herein, this is designated
as resin 4-A and has an average EEW of about 235.
To the remaining product 0.3 gram of dicumyl
peroxide was added and the reaction temperature was raised
to 145C and the reaction conducted under vacuum for 2 hours.
The decomposition of the dicumyl peroxide was essentially
complete and about 50% of the polymer-mod.ifier pres~ent was
vulcanized. The resultant vulcanized. product, for purposes
herein, is designated as resin 4-B and had an~average EEW
of about 236.
Adhesives were prepared from each of the above
prepared modified.-resins employing the following formulation.
6 grams of mod.ified resin
! 15 5 grams of the unmodified. d.iglycidyl ether of
bisphenol A having an average EEW of 187
8 grams of aluminum powder
0.5 gram of colloidal silica
0.8 gram of dicyandiamide
0.3 gram of dichlorophenyl dimethylurea
. 20 Lap shear samples were prepared using 4 1/2" x
1" x .020" d.ichromate etched type 2024-T3 aluminum strips
; overlapped 1/2". The strips were then cured at 280F for
1 hour. Lap shear values were then obtained accord.ing to
ASTM D-1002 at various temperatures. The results are
reported in the following table as the average of three
samples.
~`,
.
16,540-F -12-
1~37188
Resin 4-A Resin 4-B
UnvulcanizedVulcanized
Test TemPerature,F. (ComParative)(Present Inv.)
77 2610 psi5390 psi
150 3180 5340
200 3330 5000
240 2370 3760
260 1420 2560
280 1020 1520
300 730 930
ExamPle 5
To a reaction vessel equipped. with stirring and
temperature control means was added 200 grams of a d.iglycidyl
ether of bisphenol F (p,p'-methylenediphenol) having an
average EEW of about 167 and 18 grams of a carboxyl containing
acrylonitrile-butadiene polymer having about 28Yo acrylo-
nitrile, an average COOH functionality of about 1.9~ 0. 047
equivalent of COOH per 100 grams of polymer and an average
molecular weight of 3500. After devolatilizing the mixture
at 80C under vacuum, the vacuum was replaced with an atmos-
phere of nitrogen and 100 milligrams of tetrabutyl phosphonium
acetate-acetic acid complex catalyst was ad.ded.. The tempera-
ture was raised to 125C and maintained thereat for about
1 1/2 hour~. Then 0.6 gram of dicumyl peroxide was added
; and. the reaction continued for 2 hours at 145 C under vacuum.
One fourth, 54.5 grams of the resultant clear amber liquid
product was removed and for the purposes herein designated
as resin 5-A having a percent epoxide of 22.6 (190 EEW) and
a viscosity of 9,200 centipoises. To the remaind.er of the
product, .45 gram of d.icumyl peroxide was added and the re-
action continued. at 150C for 2 hours. One-half of the
16,540-F -13-
' ~.
1037188
resultant clear amber liquid product having a percent epoxide
of 22.6 (EEW of about 190) and a viscosity of 18,200 centi-
poises was removed. and for the purposes herein designated as
resin 5-B. To the remainder of the resultant product 0.3
grams of dicumyl peroxid.e was added and the reaction continued
under vacuum for 2 hours at 150~C. The resultant product
was a clear, bright yellow liquid having a viscosity of 22,000
centipoises and. a percent epoxide of 22.5 (191 EEW) and for
the purposes herein it was designated resin 5-C.
The mole ratio of peroxide/polymer modifier of
each of the products prepared above was as follows:
Resin Peroxid.e/PolYmer Modifier Mole Ratio
5-A 0.5:1
5-B 1.0:1
5-C 1.5:1
Each of the three products were employed as
adhesives employing the following composition.
10.9 grams modified resin
8 grams aluminum powder
0.5 grams colloidal silica
0.8 grams dicyand.iamide
. 0.2 grams melamine
The adhesives were applied. to etched. 4 1/2" x 1"
x .064" Type 2024-T-3 aluminum test strips for lap shear
and Type 304 stainless steel strips for climbing drum peel,
~ and. after heating at 175C for 0.75 hours the lap shear and
- climbing drum peel strength values were determined at 77F
as d.escribed in ASTM D-1002-64 and.ASTM D-1781-62. The
results are given in the following table.
:"~
1~,540-F -14-
1037~BB
Climbing Drum
Lap Shear Strength Peel Strength
Resin ~o. (psi) lb/inch
`5-A 5930 108
5-B 5740 114
5-C 5660 113
The above example indicates that no particular
advantage over a slight increase in the climbing drum peel
strength is obtained by employing mole ratios of peroxide/
polymer mod.ifier greater than about 0.5:1.
Example 6
~o a 500 ml 3-neck flask equipped for agitation,
nitrogen purge, evacuation, and temperature control was
added:
150 grams of a 2.1 functional epoxy novolac
resin having an EEW of about 167
15 grams CTBN (carboxyl terminated butad.iene-
acrylonitrile rubber containing 26% acrylo-
nitrile and having an average molecular
weight of about 3500)
: 50 milligrams tetrabutylphosphonium acetate--
acetic acid. complex catalyst
The mixture was raised. to a temperature of 105C,
~evacuated and held 1/2 hr. to complete the reaction between
carboxyl and epoxide. Then 0.50 gram of di-tertiary butyl
: 20 peroxide was added. and. the temperature raised guickly to
180C (the temperature at which the rate of decomposition
of this peroxid.e is the same as that for dicumyl peroxid.e
at 155C). A limited vacuum was pulled (to 100 mm Hg.) and
held 1/2 hr. Volatility of this peroxide requires caution
in pulling a high vacuum at such an elevated. temperature.
To assure that peroxid.e was actually present under these
conditions, at the end of this 1/2 hour interval the vacuum
16,540-F -15-
1037188
was released using nitrogen, and 0.25 g. additional di-
tert. butyl peroxid~e was added dropwise. The reaction
mixture was then agitated under 1 atmosphere nitrogen
pressure for 15 minutes and under full vacuum an additional
15 minutes, all at 180C. The product was then cooled and
poured off as a clear amber liquid, with a viscosity at
room temperature of 28,200 centipoises and. an epoxid.e
content of 22.6% (191 EEW).
Adhesives were prepared from the above product
employing the following composition.
11 grams mod.ified resin
~ grams aluminum powder
0.5 grams colloidal silica
0.8 grams dicyandiamide
0.2 grams melamine
The adhesives were applied to etched 4-1/2" x
1" x .064" Type 2024-T-3 aluminum test strips for lap shear
and Type 304 stainless steel strips for climbing drum peel,
and. after heating at 175C for 0.75 hours the lap shear
and climbing drum peel strength values were determined
at 77F as described in ASTM D-1002-64 and ASTM D-1781-62.
. The lap shear strength was 5490 psi and. the climbing drum
peel strength was 106 lb/in.
. ExamPle 7 - Thiol-Containinq Polymer Modifier
. 25 A. . The procedure, reactants and concentration of
., reactants were the same as in Example l-A except that
:: the polymer employed was an acrylonitrile-butadiene co-
polymer having an average molecular weight of about 3000,
:~ an acrylonitrile content of about 24% and a mercaptan (SH)
functionality of about 1.6. The resultant modified epoxy
1~,540-F -16-
~0371B8
resin had an EEW of about 558 and a Durran's softening
point of about 71C.
B. The reactants and procedure of-A above was em-
ployed except that no dicumyl peroxide was employed. The
resultant modified epoxy resin had an EEW of about 558 and
a Durran's softening point of about 71C.
C. Adhesives were prepared from A and B above according
to the procedure in Example l-D. The results were as follows:
Tensile Shear Strenqth. PSi
SamPle 77F. 250F.
A 5716 1083
B 5333 866
ExamPle 8
A. Room TemPerature Curinq Structural Adhesive
A structural epoxy ad.hesive must produce bonds
that have three characteristics: (1) high lap shear and
peel strengthJ (2) low creep (ability to carry a calculated
load. indefinitely without yielding), and. (3) stability
against various forms of environmental attack - temperature,
humidity, etc.
Room temperature curing agents of which triethylene-
tetraamine (TETA)~ diethylenetriamine (DETA), and poly-
amides are most commonly used have never been able to provide
adhesives with suitable peel strength, even with modified
epoxies that give good peel strength when cured at elevated
temperature. We have now prepared carefully selected epoxy-
modifier-hard.ener systems that are found. to meet all the
reguirements for a structural ad.hesive. Since the vulcaniza-
tion of the nitrile rubber modifier is an important step in
the preparation, examples are presented as a part of this
patent application. The preparation and testing of the
1~,540-F -17-
1037~88
adhesive is described, followed by a comparison to results
obtained when the variables or their levels are changed
from the optimum.
To a 10-gallon kettle was add.ed:
75 lb. of an epoxy novolac resin employed and
described in Example 6,
13.5 lb. polymer modifier as employed and
described in Example 6,
24 grams tetrabutyl phosphonium acetate-acetic
acid complex catalyst as a 70O/o solution in
methanol.
The charge was heated to the reaction temperature
of 100C and held 1 hour to assure complete reaction of the
carboxyls on the rubber with epoxide. Then 85 grams of
dicumyl peroxid.e were added and the temperature raised to
150C for 2 hours reaction und.er vacuum. A product was then
drummed out and cooled., analyzing 20.95% epoxide and having
a viscosity of 53500 cp. at 25C.
An adhesive was formulated. from 118 parts of this
~: resin, 40 parts a-luminum powd.er, 10 parts colloidal silica,
and 34 parts DEH~ 29 hard.ener, a polyethylene polyamine con-
taining about 10.9% primary, 17.9% secondary and 5.9~
tertiary nitrogen and an average amine hyd.rogen equivalent
weight of about 30.3.
Lap shear samples were prepared on aluminum sub-
. strates as described previously and tested according to
ASTM D-1002-64. The samples were cured four days at room
~ 25 temperature prior to testing.
; Test TemP. Lap Shear Strenqth
: Room Temp. 4560 psi
150F. 3480 psi
180F. 2130 psi
210F. 1040 psi
16,540-F -18-
1037~88
A climbing drum peel sample was prepared according
to ASTM D-1781-62 using 1" x 12" x 0.020" Type 304 stain-
less steel substrates, etched in conc. HCl at room tempera-
ture. The peel strength after 4 days cure at room tempera-
ture was measured as 89 lb/inch width. These strengths
correspond to those we find for high temperature cured
structural epoxies.
B. Variation in the Hardener Series Including
DiethYlene Triamine and Its Homoloqs
150 grams of a diglycidyl ether of bisphenol A
having an EEW of about 189 epoxy plus 45 g. of an acrylo-
nitrile-butadiene copolymer having an average molecular
weight of 2200 and a COOH functionality of about 1.9 were
mixed and reacted to give complete reaction of the carboxyls
with epoxide. The vulcanization step was omitted in this
case.
To 6.5 grams of this resin was added:
a. 1.0 gram aluminum powder
b. 0.25 gram colloidal silica
c. amount as specified in the Table of a
hardener belonging to the diethylene-
triamine family.
, ,
Test samples were prepared for the climbing drum
, peel test, with a 4-day room temperature cure preceding the
; actual peel test.
Hardener Atnount Peel Value
; 25 DETA 0.522 g. 2 lb/inch
TETA 0.725 g. 42 lb/inch av.
TEPA 0.930 g. 50 lb/inch
D.E.H.~ 29 1.132 g. 75 lb/inch
16,540~F -19-
~, . .
~ 03718B
This shows the improved performance given by the
higher molecular weight hardener homologs. In each case,
the hardener was assumed to be four-functional; that is,
only the hydrogens attached to the terminal nitrogens were
assumed reactive. Thus, excess hardener was pre~ent over
the amount normally calculated as stoichiometric. That
the excess hardener is beneficial is demonstrated in
Example 8-C below.
C. To a 500 ml 3-necked flask equipped for agitation,
nitrogen purge, evacuation, and temperature control, was
added:
120 grams of a 2.1 functional epoxy novolac
resin as defined in Example 6
21.6 grams polymer modifier as described in
Example 6
lS 60 mg tetrabutyl phosphonium acetate acetic
acid complex catalyst
The contents were heated to 120C and held for 1
hour to assure complete reaction of the rubber carboxyls
with epoxide. Then 0.292 grams of dicumyl peroxide was
added and the temperature raised to 150C and held for two
; 20 hours under a full vacuum. The product was then cooled and
poured off as a bright yellow liquid, analyzing 21.7% epoxide
and with a viscosity of 39000 cp.
A "masterbatch" was made from:
70.8 g. above resin
12 g. aluminum powder
3 g. colloidal silica
Four adhesives were prepared by mixing 7.15 grams
of the above formulation with the following amounts of
D.E.H.~ 29 hardener.
16,540-F -20-
1~3~8B
A. 1.08 g. D.E.H~ 29 (stoichiometric)
B. 1.61 g. "
C. 2.15 g. "
D. 4.22 g. polyamide having an amine hydrogen
equivalent weight of about 150.
Lap shear samples were prepared as already
described and Tee Peel samples were also prepared according
to ASTM D-1876-61T, using 1" x 8" x 0.024" Type 2024-T3
aluminum strips, etched by the FPL procedure. Two strips
were spread with the adhesive, then sandwiched~together
and clamped with paper clips for the four day cure period.
Test Results
Adhesive
Sample LaP Shear Strenqth Tee Peel
A 3540 psi (av. of 2) 11.2 lb/in.
B 3860 20.5
C 4850 32.0
D 2760 3.2
This test indicates improved performance for
adheslves using greater amounts of the D.E.H~ 29 poly-
ethylene polyamine hardener. However, results from environ-
mental exposure tests and elevated temperature testing
indicate a fall-off in performance at double stoichiometric
D.E.H.~ 29 (as in C above) and thus the formulation becomes
non-structural for this reason. Sample B above did not show
reduced performance in this respect.
D. Optimum Rubber Modifier Level
In addition to the test using 18 phr of the
vulcanized rubber modifier, lower levels were tested by
diluting with unmodified resin or by preparing separate
modified epoxies. Results are given below, using 32 phr
(parts per 100 parts of epoxy resin) D.E.H~ 29 polyethylene
16,540-F -21-
1037188
polyamine hardener in all cases. In each instance the
polymer modifier which was vulcanized was that described
in Example 6 employing the vulcanization procedure of
Example 8-C.
PHR of
Modifier Lap ShearClimbinq Drum Tee Peel
18 3860 psi -- 20.5 lb/in.
4270 92 lb/in. 5.7 lb/in.
13 4300 88 7.0
9 4300 25 6.2
6 4300 9 6.4
E. Variation in Rubber ComPosition
Vulcanized rubber modified 2.1 functional epoxy
novolac resin was prepared containing 10 phr rubber using
(A) 3500 av. M.W. acrylonitrile-butadiene
polymer, 26% acrylonitrile, about 1.9
COOH average functionality,
(B) 3500 av. M.W. acrylonitrile-butadiene
polymer, 18.6% acrylonitrile, about 1.85
COOH average functionality.
Adhesives prepared and tested as in the examples
above gave
Lap Shear Climbinq Drum Tee Peel
; (A) 4150 psi 88 lb/inch 7.0 lb/inch
(B) 4790 18 lb/inch 7.7 lb/inch
F. Environmental Stabilitv of Bonds
The adhesive formulations from Example 8-C were
; used to prepare lap shear samples that were subsequently
- placed under an applied stress and exposed to a programmed
temperature-humidity environment. The lap shear samples
were held at these conditions until the ~ample failed (broke).
16,540-F -22-
~ . .
1037188
Conditions Required to Cause Failure
Sample (Av. of 2 samPles)
A 57 C~ 1500 psi stress: 2 days d.ry
~ 2 hrs. ~ 98% rel. humidity
B 57CJ 1500 psi: 2 d.ays d.ry I 1 hr.
@ 98% rel. humid.ity
C 57C~ 1500 psi: 1 day d.ry, < 50%
rel. humidity
D 40C~ 1500 psi: 1 hr. dry
16,540-F -23-
