NASA CASE NO.

PRINT FIG. N/A

NOTICE

I

LAR 15229-_.-CU

The invention disclosed in this document resulted from research in aeronautical and

space activities performed under programs of the National Aeronautics and Space

Administration. The invention is owned by NASA and is, therefore, available for

licensing in accordance with the NASA Patent Licensing Regulation (14 Code of

Federal Regulations 1245.2).

To encourage commercial utilization of NASA-owned inventions, it is NASA policy

to grant licenses to commercial concerns. Although NASA encourages

nonexclusive licensing to promote competition and achieve the widest possible

utilization, NASA will provide the necessary incentive to the licensee to achieve

early practical application of the invention.

Address inquiries and all applications for license for this invention to NASA Patent

Counsel, Langley Research Center, Code 143, Hampton, Virginia 23681-0001.

Serial No.: 08/186,054

01/18/94 LaRC

(NASA-Case-LAR-I5229-I-CU)

POLY(ARYLENE ETHER-C0-IMIDAZOLE)S

AS TOUGHNESS MODIFIERS FOR EPOXY

RESINS Patent Application (NASA.

Langley Research Center) 21 p

N94-29451

Unclas

G3/27 0003778
AWARDS ABSTRACT 

POLY(ARYLENE ETHER-CO-IMIDAZ0LE)S AS TOUGHNESS MODIFIERS 

FOR EPOXY RESINS 

NASA Case No. LAR 15229-1 -CU 

Thermosetting materials based on epoxy chemistry were one of the first systems 

developed for use as coatings, adhesives and composite matrices. The use of high 

temperature thermosetting materials in composites is a major area of interest. Fiberreinforced organic composites for aerospace structural applications offer the 

advantages of higher strength to weight ratios, improved fatigue characteristics, 

corrosion resistance and higher stiffness (modulus) as compared to their metal 

counterparts. Epoxies offer certain advantages over other materials such as low 

density, tack, drape, processability, and low cost. Once cured, these polymers exhibit 

high glass transition temperatures (Tg) and good mechanical properties. 

By the present invention, poly(arylene ether-co-imidazole)~ (PAEI) were prepared by 

reacting an aromatic bisphenol, a bisphenol imidazole and an activated aromatic 

dihalide or dinitro compound in the presence of potassium carbonate in a polar aprotic 

solvent at elevated temperatures under nitrogen. The resulting PAEl is a random 

copolymer having pendant imidazole units along the polymer backbone. These 

imidazole units provide reactive sites for an epoxy. The distance between PAEl-epoxy 

crosslinks can be controlled by varying the amount of imidazole present along the 

polymer backbone. The distance between the epoxy end groups and the PAEl units is 

less than that obtained with thermoplastic oligomers in which reactive sites are only at 

the ends. A comparison of the PAEl modified epoxies with those of the prior art shows 

that the PAEl modified system had a significantly greater increase in the fracture 

toughness. 

The novelty of this invention resides in the structure of the poly(arylene ether-coimidazole). By controlling the molecular weight, these polymers are soluble in epoxy at 

high concentrations. As a result, the modified system is tough with only a limited 

decrease in the glass transition temperature. 

Inventors: Patricia D. McDaniel 

100 Cypress Crossing 

Yorktown, VA 23692 

John W. Connell 

204 Henry Lee Lane 

Yorktown, VA 23690 

Employer: Graduate Student NASA LaRC 

College of William & Mary 
Inventors: 

Paul M. Hergenrother 

305 Old Dominion Road 

Yorktown, VA 23692 

Employer: NASA LaRC 

initial Evaluator: Terry L. St. Clair 

Serial No.: 08/186,054 

Filed: January 18,1994 
LAR 15229-1 -CU -1 - PATENT APPLICATION

POLY(ARYLENE ETHER-CO-IMIDAZOLE)S AS TOUGHNESS MODIFIERS

FOR EPOXY RESINS

5

10

15

20

25

3O

Origin of the Invention

The invention described herein was jointly made by employees of the

United States Government and a contract employee in the performance of work

under NASA Grant number NCC1-150 and is subject to the provisions of Public

Law 96-517 (35 U.S.C. 202) in which the contractor has elected not to retain

title.

Background of the Invention

1. Field of the Invention

The present invention relates to epoxies. In particular, it relates to the

toughening of epoxies using poly(arylene ether-co-imidazole)s as modifiers.

2..__. Description of the Related Art

Thermosetting materials based on epoxy chemistry were one of the first

systems developed for use as coatings, adhesives and composite matrices.

The use of high temperature thermosetting materials in composites is a major

area of interest. Fiber-reinforced organic composites for aerospace structural

applications offer the advantages of higher strength to weight ratios, improved

fatigue characteristics, corrosion resistance and higher stiffness (modulus) as

compared to their metal counterparts. Epoxies offer certain advantages over

other materials such as low density, tack, drape, processability, and low cost.

Once cured, these polymers exhibit high glass transition temperatures (Tg) and

good mechanical properties.

Despite these advantages, epoxies have several deficiencies which

restrict their use in certain applications. A fully cured epoxy resin is comprised

of a highly crosslinked complex matrix which causes the cured polymer to be

brittle or lack damage tolerance. In addition, epoxies have high moisture
5

10

15

2O

25

3O

LAR 15229-1-CU -2- PATENT APPLICATION

absorption and limited thermo-oxidative stability.

In order to use epoxies as structural materials for the aerospace

industry, the polymer must exhibit rigidity, resistance to creep, high Tg and high

impact strength or damage tolerance. However, damage tolerance and/or high

impact strength are qualities of elastomers rather than thermosets. This is

currently the major problem in designing commercially viable high performance

resins.

To overcome this deficiency, several approaches have been taken which

provide a toughened epoxy system whose morphology allows for toughness

and stability while under stress at elevated temperatures without having an

adverse affect on the modulus, Tg and processability of the polymer. The most

widely used method of thermoset modification has been by the dispersion of a

ductile second phase into the matrix. Predispersion of rubber particles into an

epoxy resin, prior to curing, generally improves fracture toughness but

compromises thermal resistance and hot/wet properties. The development of

a low cost epoxy with improved toughness while maintaining its other properties

would greatly expand the use and broaden the market for these materials.

Blends of thermosets with elastomers, glassy thermoplastics or reactive

thermoplastics are being evaluated as potential toughening matrices wherein

specific attributes of several polymers are combined in a single material. An

example of a reactive thermoplastic modified epoxy is described in Pak et al.

("Synthesis and Characterization of NovelToughened Thermosets Derivedfrom

Pendent Amines on the Backbone of Poly(arylene ether sulfone)s", Polymer,

Volume 34, Number 4, 1993.). They randomly incorporated pendent aryl

amines onto the backbone of poly(arylene ether sulfone)s to give copolymers

which have the following structure:

(-0 CH 0, - _ CH, 0 )

CH3 O CH_ __NH2
5

10

15

20

25

3O

LAR 15229-1-CU -3- PATENT APPLICATION

and subsequently reacted them with liquid epoxy resin and 4,4'-diaminodiphenylsulfone (DDS). It was demonstrated that selected compositions could

significantly improve the fracture toughness of the epoxy networks. For a

poly(arylene ether sulfone) having a 2.5 mole percent crosslink site which was

loaded at 25 weight percent into epoxy, the fracture toughness was 2.28+_0.43

MNm 3_ as compared to the control which had a fracture toughness of

0.75+_0.08 MNm -3e. However, at a 10 weight percent loading of the same

polymer into the epoxy, the fracture toughness was only 0.92+0.06 MNm -3_2.

It was also observed that when the concentrations of the crosslink site of the

reactive thermoplastic toughener increased, there was relatively little

improvement in the fracture toughness.

In another case where reactive thermoplastics are used as toughening

agents, thermoplastic oligomers endcapped with a reactive group (i.e. phenol,

amine, or epoxy) are blended into the epoxy. The system is cured and the

thermoplastic is incorporated into the matrix via the reactive end group.

Hedrick et al. ("Chemical Modification of Matrix Resin Networks with

Engineering Thermoplastics: 1. Synthesis, Morphology, Physical Behavior and

Toughening Mechanisms of Poly(arylene ether sulfone) Modified Epoxy

Networks", Polymer, Volume 32, number 11, 1991 .) modified epoxy resins with

either phenolic hydroxyl or aromatic amine terminated aryl ether sulfone

oligomers and thermally cured them with 4,4'-diaminodiphenyl sulfone. The aryl

ether sulfone oligomers were miscible with the epoxy precursor and upon

network formation a two phase structure developed in which the polysulfone

formed discrete particles evenly dispersed in the epoxy matrix. The resulting

networks showed an increase in fracture toughness from 0.6x106 MNm -3_

(control) to 0.8x106 MNm 3_2 (for 10%) to 1.1x106 MNm -3_ (for 15%).

An object of the present invention is to increase the toughness of

epoxies by reacting the epoxy with poly(arylene ether-co-imidazole)s.

Another object of the present invention is to prepare molded parts from

the toughened epoxies.
LAR 15229-1-CU -4- PATENT APPLICATION

Another object of the present invention is to prepare composites from the

toughened epoxies.

5

10

15

2O

Summary of the Invention

Poly(arylene ether-co-imidazole)s (PAEI) were prepared by reacting an

aromatic bisphenol, a bisphenol imidazole and an activated aromatic dihalide

or dinitro compound in the presence of potassium carbonate in a polar aprotic

solvent at elevated temperatures under nitrogen. The resulting PAEI is a

random copolymer having pendant imidazole units along the polymer backbone.

These imidazole units provide reactive sites for an epoxy. The distance

between PAEI-epoxy crosslinks can be controlled by varying the amount of

imidazole present along the polymer backbone. The distance between the

epoxy end groups and the PAEI units is less than that obtained with

thermoplastic oligomers in which reactive sites are only at the ends. A

comparison of the PAEI modified epoxies with the poly(arylene ether sulfone)

modified epoxies of Pak et al. shows that the PAEI modified system having a

10 mole percent crosslink site and a i0 weight percent reactive thermoplastic

exhibited an increase in fracture toughness of 1.75 fold. This is significantly

greater than the fracture toughness reported by Pak et al. for their epoxies

which were modified with poly(arylene ether sulfone)polymer having the same

percentage of crosslink sites and reactive thermoplastic. For this system, Pak

et al. reported an increase in fracture toughness from 0.75+0.08 MNm 3_

(control) to 0.84+_0.12 MNm -3_2.

25

30

Description of the Preferred Embodiments

The poly(arylene ether co-imidazole)s of the present invention have the

repeat unit:
5

LAR 15229-1-CU -5- PATENT APPLICATION

wherein Ar is a member selected from the group consisting of:

10

15

20

25 wherein Y is a member selected from the group consisting of: a direct bond,

-O-, -S-, -CO-, -SO2-,-CH2-,-C(CH3)2-,-C(CF3)2-,

3O

,o, ?

p --P--

, , and ---P--oI

CH3

CH3
LAR 15229-1-CU -6- PATENT APPLICATION

wherein Ar' is a member selected from the group consisting of:

5

10

0 0 0

-_ -_'-_

--, --S02--- , --,

0 0 0 0

-_ o , " --__

_ P"--" T

@

0 0 0 0 0 0

---C -- , ---C --, --C --

15

2O

wherein R 1is a member selected from the group consisting of:

25

and

N,_NH

R3

3O

wherein the catenation is meta meta, meta para, or para para;
LAR 15229-1 -CU -7- PATENT APPLICATION

wherein R: is a member selected from the group consisting of:

-@-:-G-,- .... ,°©_

5 wherein G is a member selected from the group consisting of: a direct bond,

-CH2-,-O-,-S-,-CO-, and-SO2-;

10

15

wherein R 3 is a member selected from the group consisting of: -H, -CH 3,

_©_o_©

Z 7

20

wherein Z is a member selected from the group consisting of: -CH 3,

-CF 3, -OCH 3, -NO 2, -I, -CI, -Br, -F, -CH_CH 3, and phenyl; and

25

wherein the ratio of

-- ('--O-Ar-O

3O

ranges from about 99 to 1 to about 1 to 99.

In a preferred embodiment of the invention, this ratio is 90 to 10.
5

LAR 15229-1-CU -8- PATENT APPLICATION

Of particular mention is that when a phosphine oxide unit is selected for

an Ar' and/or a Y substituent, not only does the copolymer offer increased

toughness to the epoxy but it also causes the final composition to be atomic

oxygen resistant. This is important for low earth orbit space applications where

atomic oxygen resistance is necessary.

In a preferred embodiment of the invention, Ar is a member selected

from the group consisting of:

10

15

--r,'_,_cH_d---,,"y-j

Cll_

Ar' is a member selected from the group consisting of:

2O

0 0 0 0

o_-- "'_ "

--C _ end --C--

,

R_ is

25

NyNH

R3 ;and

30 R 3 is phenyl.
5

LAR 15229-1-CU -9- PATENT APPLICATION

The modified epoxies prepared with these particular PAEIs showed a

significant increase in toughness with only a 10 weight percent loading of the

PAEI.

In a most preferred embodiment, Ar is

10

15

Ar' is -CO-; R1 is

NyNH

R3

; and

R3 is phenyl.

2O

25

3O

This particular PAEI exhibited the highest degree of solubility in the epoxy

resin while maintaining a favorable Tg. In addition, it gave significantly

improved toughness results as compared to samples prepared using other

PAEIs to toughen the epoxies.

In preparing the toughened epoxy, the epoxy resin which was preferred

for the present invention was that of N,N,N',N'-tetraglycidyl-4,4'-

methylenebisbenzenamine which is commercially available from Ciba-Geigy

Corporation as Araldite_ XU MY 722. The PAEI was added to the epoxy resin

and allowed to react at 100°C until a homogeneous melt was obtained. A

stoichiometric ratio of epoxide equivalent weight to the preferred curing agent,

4-aminophenyl sulfone, commercially available from Aldrich Chemical Company
5

10

15

2O

25

30

Imidazole

LAR 15229-1 -CU -10- PATENT APPLICATION

as 4,4'-DDS, was added to the mixture. A vacuum was applied throughout the

process to degas the system. The following scheme shows the reaction

mechanism for the reaction of a PAEI with an epoxy.

0 N'%/N-CH2- _ 0

/X _ /X

CEpoxy H21CH....,. _ [_ + CH2_CH...,_.

,/

Imidazole/Epoxy bond formation

Test specimens were hot-melt cast into RTV silicone molds and cured

according to the following cure cycle: 1 hour at 80'_C; 1 hour at 100_C; 4 hours

at 150°C; and 6 hours at 200°C. The specimens were slowly cooled to room

temperature prior to removal from the molds. This same cure cycle is followed

for preparing composites.

The Tg, solution viscosity and solubility in the neat epoxy resin were

measured for a series of PAEIs having various molecular weights. Inherent

viscosities ranged from 0.42 to 0.91 dL/g for the PAEls. The Tgs for these

PAEIs ranged from 147 ° to 237°C. All of the soluble systems formed tough,

creasable films.

Polymer solubility in the neat epoxy resin facilitated processing of the

modified resins. A polymer Tg close to that of the cured epoxy system was

targeted to maintain use temperature.

High molecular weight PAEIs were found to have a limited solubility in

the epoxy resin making incorporation of high thermoplastic loadings difficult.

Therefore, a controlled molecular weight version was prepared using bis(4-

fluorophenyl)ketone, 9,9-bis(4-hydroxyphenyl)fluorene (90%) and 2-phenyl-4,5-
5

10

15

20

25

LAR 15229-1-CU -11- PATENT APPLICATION

bis(4-hydroxyphenyl)imidazole (10%). This controlled molecular weight PAEI

was found to be soluble in the epoxy at high concentrations which results in

toughened modified systems with a limited decrease in glass transition

temperatures.

Neat resin moldings for the high molecular weight polymer were

fabricated at 340°C for 1hour at 300 psi. The moldings were well consolidated

and void free. Miniature compact tension specimens yielded stress intensity

factors of 1.83 MNm=/2when tested at room temperature. The modified epoxy

specimens were opaque with slightly crazed fracture surfaces indicative of

ductile failure while unmodified epoxy specimens had clear, smooth fracture

surfaces which is indicative of brittle fracture. The stress intensity factors for

the notched three point bend fracture specimens exhibited increased toughness

with increasing polymer content.

The modified system undergoes a phase separation during cure as

indicated by increasing tubidity with increasing polymer concentration and was

confirmed by Scanning Electron Microscopy. This phase separation is

desirable because separation during cure of a predominately thermoplastic

second phase serves as an energy absorbing mechanism enhancing crack

resistance and toughness.

The following are examples which illustrate the preparation and use of

PAEIs in epoxy systems for applications such as composites and molded parts.

These examples are merely illustrative and intended to enable those skilled in

the art to practice the invention in all of the embodiments flowing therefrom,

and do not in any way limit the scope of the invention as defined by the claims.
LAR 15229-1-CU -12-

EXAMPLES

Example 1

PATENT APPLICATION

5

The following example illustrates the reaction sequence for the synthesis

of a poly(arylene ether-co-imidazole) having the following repeat unit:

10

15

20

25

3O

Into a 100 ml three neck round bottom flask equipped with a mechanical

stirrer, thermometer, nitrogen inlet, moisture trap and reflux condenser was

placed 9,9-bis(4-hydroxyphenyl)fluorene (80.8804 g, 0.23 mol), 2-phenyl-4,5-

bis(4-hydroxyphenyl) imidazole (8.4213 g, 0.03 mol), bis(4-fluorophenyl)ketone

(55.9597 g, 0.26 mol), pulverized anhydrous potassium carbonate (81.52 g,

0.59 mol, 15% excess), dry N,N-dimethylacetamide (DMAc) (540 ml, 20%

solids) and toluene (80 ml). The mixture was heated to about 135°C for four

hours and then heated to 155°C overnight under nitrogen. The viscous yellow

solution was precipitated into a water/acetic acid mixture, collected, washed

successively in water and methanol and dried at 125°C. The yield was 97.8 g

(72%) of white polymer having a glass transition temperature of 237°C. The

inherent viscosity of a 0.5% solution in chloroform at 25°C was 0.63 dL/g.

The same procedure was followed to prepare poly(arylene ether-coimidazole)s which had the same repeat unit but differed by the stoichiometric

ratio of 9,9-bis(4-hydroxyphenyl)fluorene to bis(4-fluorophenyl)ketone where the

amount of 2-phenyl-4,5-bis(4-hydroxyphenyl) imidazole remained constant at

10 mole percent of the copolymer. The copolymer stoichiometry is summarized

in Table 1 and the final neat copolymer properties are summarized in Table 2.
LAR 15229-1-CU -13-

Table 1

PATENT APPLICATION

5

1:1 Stoichiometry

10 mole % offset favoring bisphenol

10 mole % offset favoring dihalide

5 mole % offset favoring bisphenol

5 mole % offset favoring dihalide

Polymer 1

Polymer 2

Polymer 3

Polymer 4

Polymer 5

10

15

20

Table 2

Polymer

2

3

I1 a

(g/mol)

4814

3505

2524

4 5478

5 4294

TGA b

(°C)

458.1

430.5

461.0

430.5

491.5

0.498

0.183

0.143

0.279

0.222

11 inh d

dL/g

0.34

0.16

0.13

0.23

0.19

Tg _

(°C)

243

223

205

251

226

"Gel Permeation Chromatography/Differential Viscometry

_GA at 2.5°C/min

Clnherent Viscosity in unstabilized tetrahydrofuran at 35°C with

0.5% wt% solutions

alntdnsic Viscosity in N-methylpyrolidone with 0.02 molar LiBr at 60°C

"Differential Scanning Calorimetry 20°C/min

25
LAR 15229-1-CU -14-

Example 2

PATENT APPLICATION

5

10

15

2O

25

30

Another poly(arylene ether-co-imidazole) was prepared which has the following

structure:

Into a 100 ml three neck round bottom flask equipped with a mechanical

stirrer, thermometer, nitrogen inlet, moisture trap and reflux condenser was

placed [(4-hydroxyphenyl)-2-propyl]benzene (12.4339 g, 35.89 mmol), 2-phenyl4,5-bis(4-hydroxyphenyl) imidazole (1.3094 g, 3.99 mmol), 1,3-bis(4-

fluorobenzoyl)benzene (12.8522 g, 39.87 mmol), pulverized anhydrous

potassium carbonate (19.01 g, 137.54 mmol, 15% excess), dry N,Ndimethylacetamide (DMAc) (107 ml, 20% solids) and toluene (45 ml). The

mixture was heated to about 135°C for four hours and then heated to 155°C

overnight under nitrogen. The viscous orange solution was precipitated into a

water/acetic acid mixture, collected, washed successively in water and

methanol and dried at 125°C. The yield was 22.14 g (89%) of white polymer

having a glass transition temperature of 158°C. The inherent viscosity of a

0.5% solution in DMAc at 25°C was 0.48 dL/g.

The same procedure was followed to prepare poly(arylene ether-coimidazole)s which had the same chemical composition but differed by the ratio

of [(4-hydroxyphenyl)-2-propyl]benzene to 2-phenyl-4,5-bis(4-hydroxyphenyl)

imidazole with the molar amount of 1,3-bis(4-fluorobenzoyl)benzene remaining

constant at a stoichiometric ratio of 1:1. Table 3 summarizes the various

properties for the polymers prepared with varying [(4-hydroxyphenyl)-2-

propyl]benzene/2-phenyl-4,5-bis(4-hydroxyphenyl) imidazole ratios.
5

10

LAR 15229-1-CU -15-

Table 3.

PATENT APPLICATION

X:Y

100:0

90:10

70:30

50:50

Tg

(°C)

157

159

171

Temp. of 5%

Weight Loss f (°C)

402

404

185

30:70 199 387

90:10 213 367

367

425

Intrinsic Viscosity g

(dL/g)

0.70

0.44

0.44

0.42

0.42

0:100 220 374 0.55

f TGA at 2.5°C/min

g 35°C in THF

15 Example 3

The procedures for Examples 1 and 2 were followed to prepare other

poly(arylene ether-co-imidazole)s which have the repeat unit:

2O

25

-- -O-Ar-O )- --0

where the backbone of the copolymer was varied and the mole percent of the
LAR 15229-1-CU -16-

imidazole crosslink site remained at 10 mole percent.

viscosities for these copolymers are given in Table 4.

PATENT APPLICATION

The Tg and inherent

Table 4

-(o-_,o@_^, _G)(o_o-_^,_)-

Mole % ql.h, dug

Ar Ar' hnldazole Tg, nO _s_lv_

10 147 ......

-Or_@-!:,%

-_©-_',__

L---lt3

O

iI

--C I

O

I!

--C--

O

o --c--

o o

10

10

10

O

. 10

--C I

186

2O7

171

237

O.gl (TIIF

0.50

(CH2CI2)

0.48

(OMAc)

0.63

(0ttCI3)
LAR 15229-1-CU -17-

Example 4

PATENT APPLICATION

5

10

Into 125 ml reaction vessel equipped with a mechanical stirrer and

vacuum evacuation outlet, was placed 40.14 g (62% w/w) N,N,N',N,-

tetraglycidyl-4,4'-methylenebisbenzenamine, 6.5 g (10 % w/w) of the polymer

represented in example 1. The mixture was stirred at 100°C until a clear

homogeneous melt was obtained. 18.29 g (28% w/w) of 4,4'-

diaminodiphenylsulfone (DDS) were charged into the vessel, the mixture was

stirred and heated at 100°C until the DDS dissolved. The resin was degassed

under vacuum for 20 min. The glass transition temperatures obtained by DSC

at 20°C/min for the modified epoxy resin system are summarized in Table 5.

Table 5

15

2O

Weight % Polymer Tg (°C)

0 190

5 186

10 151

2O 154,224

Example 5

25

The resin prepared in Example 4 was hot-melt cast into RTV silicone

molds and cured according to the following cycle: 1 hour at 80°C; 1 hour at

100°C; 4 hours at 150°C; and 6 hours at 200°C. The specimens were slowly

cooled to room temperature prior to removal from the molds and tested in

accordance with ASTM E-399. Notched three point bend specimens yielded
LAR 15229-1-CU -18- PATENT APPLICATION

an increase in fracture toughness of 1.7 fold for the modified epoxy resin.

Table 6 compares the test data to that of the related art.

5

10

Table 6

Weight %

Polymer

0(control)

10

15

2O

K1¢

MN/m =_

O.388 _+0.O2

0.528 +0.03

0.660 -+0.05

Klch

MN/m _2

0.75-+0.08

0.75+0.06

0.84-+0.12

0.85+0.04

0.89-+0.06

Klc i

MN/m 3_2

0.6

15

h Pak et al. 1993

J Hedrick et al. 1991

Example 6

2O

A prepreg for a composite part is prepared by coating carbon fibers with

the modified epoxy resin prepared in Example 4. The prepreg material is then

stacked in a mold and cured according to the following cycle: 1 hour at 80°C;

1 hour at 100°C; 4 hours at 150°C; and 6 hours at 200°C. The composite

specimen is slowly cooled to room temperature prior to removal from the mold.
°.

LAR 15229-1-CU PATENT APPLICATION

POLY(ARYLENE ETHER-CO-IMIDAZOLE)S AS TOUGHNESS MODIFIERS

FOR EPOXY RESINS

5

10

15

Abstract of the Disclosure

A toughened epoxy was prepared by reacting an epoxy resin with a

poly(arylene ether-co-imidazole) (PAEI). The epoxy resin comprises N,N,N',N'-

tetraglycidyl-4,4'-methylenebisbenzenamine and 4-aminophenyl sulfone. The

PAEI was prepared by reacting an aromatic bisphenol, a bisphenol imidazole

and an activated aromatic dihalide or dinitro compound in the presence of

potassium carbonate in a polar aprotic solvent at an elevated temperature. The

epoxies which were modified with these particular PAEIs showed a significant

increase in toughness with only a 10 weight percent loading of the PAEI into

the epoxy. These toughened epoxies were used to prepare composites and

molded parts.

%