NASA CASE NO.

PRINT FIG. _N/A_

LAR 15083-1

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.: 08/299,384

09/01/94 LaRC

(NASA-Case-LAR-15083-1) A SOLVENT

RESISTANT COPOLYIMIDE Patent

Application (NASA. Langley

Research Center) 20 p

N95-14108

Unclas

G]/27 0029853
AWARDS ABSTRACT 

A SOLVENT RESISTANT COPOLYIMIDE 

NASA Case Number: LAR 15083-1 

High performance polyimides are rapidly finding new uses as matrix resins for 

composites, moldings and films in addition to their traditional use as adhesives. 

Since these materials display a number of performance characteristics such as 

high temperature and solvent resistance, improved flow for better wetting and 

bonding, high modulus, and chemical and hot water resistance, they are useful 

for the manufacture of lighter and stronger aircraft and spacecraft structures. 

By the present invention, a solvent resistant copolyimide has been prepared by 

reacting 4,4'-oxydiphthalic anhydride (ODPA) with a diamine blend comprising 

3,4'-oxydianiline (3,4'-ODA) and p-phenylene diamine (p-PDA). Films prepared 

from the copolyimide were found to be resistant to immediate breakage when 

exposed to solvents such as dimethylacetamide (DMAc) and chloroform. The 

adhesive properties of the copolyimide were maintained even after testing at 

23") 150°, 177" and 204°C. 

The novelty of this invention resides in the structure of the copolyimide, which 

had not been prepared previously. The nonobviousness is found in the 

unexpected combination of properties which includes excellent adhesion, 

increased Tg after further curing at higher temperatures, and improved solvent 

resistance as compared to LaRCTM-IA. 

Inventors: Alice C. Chang Terry L. St. Clair 

308 Marl Ravine Road 17 Roberts Landing Drive 

Poquoson, VA 23662 

Employer: Lockheed Eng. & Sciences Co. NASA LaRC 

Initial Evaluator: Darrell R. Tenney 

Serial No.: 081299,384 

Filing Date: 911194 
LAR 15083-1 -1- PATENT APPLICATION

A SOLVENT RESISTANT COPOLYIMIDE

5

Cross-Reference to Related Applications

This application is related to co-pending patent application serial

number , filed , entitled "Copolyimides prepared from

ODPA, BTDA and 3,4'-ODA" and co-pending patent application serial number

, filed , entitled "A Direct Process for Preparing SemiCrystalline Polyimides".

10

15

Origin of the Invention

The invention described herein was jointly made by an employee of

the United States Government and in the performance of work under a NASA

Contract and is subject to the provisions of Section 305 of the National

Aeronautics and Space Act of 1958, as amended Public Law 85-568 (72 Stat.

435; 42 U.S.C. 2457).

2O

Background of the Invention

1. Field of the Invention

The present invention relates to copolyimides. In particular, it relates

to copolyimides prepared from 4,4'-oxydiphthalic anhydride, 3,4'-oxydianiline,

and p-phenylene diamine.

25

3O

2. Description of the Related Art

High performance polyimides are rapidly finding new uses as matrix

resins for composites, moldings and films in addition to their traditional use as

adhesives. Since these materials display a number of performance

characteristics such as high temperature and solvent resistance, improved

flow for better wetting and bonding, high modulus, and chemical and hot

water resistance, they are useful for the manufacture of lighter and stronger

aircraft and spacecraft structures.
5

10

15

LAR 15083-1 -2- PATENT APPLICATION

One example of this type of polyimide is that prepared by St. Clair et

al. in "Polyimide Molding Powder, Coating, Adhesive and Matrix Resin",

U.S. 5,147,966. This particular polyimide, referred to hereafter as LaRCTMIA, exhibits excellent thermooxidative stability and is melt processable at

temperatures ranging from 325°-350°C. LaRCrM-IAhas a melt temperature

(Tm) of 295.2°C, an enthalpy of 33.2 J/g and a glass transition temperature

(Tg) of 229.6°C. As a result of these properties, this polymer has shown

potential use for molded parts, films, tubing, aircraft wiring insulation and as a

matrix resin for a composite. Unfortunately, it is not resistant to solvent when

the polymer is subjected to stress.

Shoji et al. (European Patent Application number 91304893.0) also

prepared LaRCTM-IAalongw!th several other readily processable polyimides

and copolyimides. An example of one such copolyimide is that prepared from

3,4'-diaminodiphenyl ether (3,4'-ODA), 4,4'-oxydiphthalic anhydride (ODPA)

and pyromellitic dianhydride (PMDA), which has the repeat units:

O N _---_O N oN O

O

2O

25

Some of these polyimides exhibited excellent processability, good chemical

resistance and outstanding transparency in addition to excellent heat

resistance. However, none of the polyimides were subjected to solvent uncler

stress. Rather, they were tested as powders.

An object of the present invention is to prepare a copolyimide which is

resistant to solvent when subjected to stress.

Another object of the invention is to prepare a solvent resistant

copolyimide by mixing a diamine blend with a dianhydride.
LAR 15083-1 -3- PATENT APPLICATION

Another object of the invention is to prepare composites, films and

adhesives from the solvent resistant copolyimide.

5

10

Summary. of the Invention

The foregoing and additional objects of the invention were obtained by

preparing a solvent resistant copolyimide by reacting 4,4'-oxydiphthalic

anhydride (ODPA) with a diamine blend comprising, based on the total

amount of the diamine blend, about 75 to 90 mole percent of 3,4'-oxydianiline

(3,4'-ODA) and about 10 to 25 mole percent of p-phenylene diamine (p-PDA).

The resulting copolyimide has the repeat units:

o

15

wherein x is 75 to 90 mole percent of the copolyimide and y is 10 to 25 mole

percent of the copolyimide.

2O

25

The copolyimide may be endcapped with up to about 10 mole percent of a

monofunctional aromatic anhydride and has unbalanced stoichiometry such

that a molar deficit in the 4,4'-oxydiphthalic anhydride is compensated with

twice the molar amount of the monofunctional aromatic anhydride.

The solvent resistant copolyimide was used to prepare composites

which had similar properties to LaRCTM-IA. Films prepared from the

copolyimide were found to be resistant to immediate breakage when exposed

to solvents such as dimethylacetamide (DMAc) and chloroform. The

adhesive properties of the copolyimide were maintained even after testing at

23 °, 150 °, 177 ° and 204°C.
5

10

15

20

25

LAR 15083-1 -4- PATENT APPLICATION

Description of the Preferred Embodiments

By the present invention, a solvent resistant copolyimide was prepared

by reacting 4,4'-oxydiphthalic anhydride (ODPA) with a diamine blend. The

diamine blend comprises, based on the total amount of the diamine blend,

about 75 to 90 mole percent of 3,4'-oxydianiline (3,4'-ODA) and about 10 to'

25 mole percent of p-phenylene diamine (p-PDA). In a preferred embodiment

of the invention, the diamine blend comprises, based on the total amount of

the diamine blend, 90 mole percent of 3,4'-oxydianiline and 10 mole percent

of p-phenylene diamine.

The copolyimide may be endcapped with up to about 10 mole percent

of a monofunctional aromatic anhydride and have unbalanced stoichiometry

such that a molar deficit in 4,4'-oxydiphthalic anhydride is compensated with

twice the molar amount of the monofunctional aromatic anhydride. For the

present invention, the preferred monofunctional aromatic anhydride is

phthalic anhydride. In a preferred embodiment, the unbalanced stoichiometry

is such that a 2.5 to 5.0 percent molar deficit exists for 4,4'-oxydiphthalic

anhydride and 5.0 to 10.0 mole percent of phthalic anhydride is used as an

endcapper. In a most preferred embodiment the copolyimide is prepared

from 4,4'-oxydiphthalic anhydride and a diamine blend, comprising 90 mole

percent of 3,4'-oxydianiline and 10 mole percent p-phenylene diamine, and

the unbalanced stoichiometry is such that a 4.0 percent molar deficit exists for

4,4'-oxydiphthalic anhydride and 8.0 mole percent of phthalic anhydride is

used as an endcapper.

Composites, films and adhesives were prepared from the copolyimide.

Testing indicated that the copolyimide had a Tg and a melt viscosity which

was comparable to LaRCTM-IA. However, when the copolyimide was further

cured at 350 °, 371° and 400°C, the Tg was unexpectedly higher than

LaRCrM-IA which had been cured under the same conditions (Table 1).
LAR 15083-1

Cure Temperature

300oc

-5- PATENT APPLICATION

Table 1

Effect of Cure Temperature on Tg

Modified System Tg, °C

LaRCrM-IA 233.0

10% PMDA 235.0

10% p-PDA 236.8

25% PMDA 237.2

25% p-PDA 239.9

350°C LaRCTM-IA 233.0

10% PMDA 238.6

240.2

371°C

400°C

10% p-PDA

25% PMDA 243.0

J

25% p-PDA 242.5

LaRCTM-IA 231.0

10% PMDA 240.2

10% p-PDA 242.3

25% PMDA 253.3

25% p-PDA 250.4

LaRCTM-IA 240.2

10% PMDA 241.0

10% p-PDA 268.0

25% PMDA 276.1

25% p-PDA 268.9
LAR 15083-1 -6- PATENT APPLICATION

Solvent resistance testing showed that a film of the copolyimide remained

creasable in acetone, methylethyl ketone, and toluene as did LaRCTM-IA and

the copolyimide of Shoji et al. but when subjected to DMAc and chloroform,

there was improved solvent resistance for the copolyimide which had been

further cured at 350 °, 371 o and 400°C as compared to LaRC'rM-IA and the

copolyimide of Shoji et al. which had been cured under the same conditions

(Table 2).
LAR 15083-1 -7-

Table 2

Solvent Resistance Testing

PATENT APPLICATION

Cure Temperature

300°C

Modified System

LaRCTM-IA

DMAc

++

3% PMDA ++

3% p-PDA ++

6% PMDA ++

6% p-PDA

10% PMDA

10% p-PDA

25% PMDA

25% p-PDA

++

++

Chloroform

++

++

++

++

++

++

+ ++

++ +

+ ++

350°C LaR(_TM-IA ++ ++

3% PMDA + ++

3% p-PDA ++ ++

6% PMDA + ++

6% p-PDA ++ ++

10% PMDA + ++

10% p-PDA +

25% PMDA + +

25% p-PDA + +

(-) SIGNIFIES CREASABLE FILM

(+) SIGNIFIES THAT FILM BREAKS AFTER IMMERSION AND CREASING

(++) SIGNIFIES THAT FILM BREAKS INTO TWO PIECES WITHIN ONE MINUTE OF

IMMERSION
LAR 15083-1 -8-

Table 2 Continued

PATENT APPLICATION

CureTemperature ModifiedSystem DMAc Chloroform

371°C LaRCTM-IA ++ ++

3%PMDA + +

3%p-PDA ++ ++

6%PMDA + +

6%p-PDA ++ ++

10%PMDA + +

10%p-PDA

25%PMDA + +

25%p-PDA +

i

400°C LaRCTM-IA + +

3% 15MDA

3% p-PDA + +

6% PMDA

6% p-PDA

10% PMDA

10% p-PDA

25% PMDA

25% p-PDA

+ +

+ +

+ +

(-) SIGNIFIES CREASABLE FILM

(+) SIGNIFIES THAT FILM BREAKS AFTER IMMERSION AND CREASING

(++) SIGNIFIES THAT FILM BREAKS INTO TWO PIECES WITHIN ONE MINUTE OF

IMMERSION
5

LAR 15083-1 -9- PATENT APPLICATION

The following are examples which illustrate the preparation and use of

a solvent resistant copolyimide for applications such as composites, films and

adhesives. 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.

EXAMPLES

10

15

2O

25

The polymers of examples 1-4 were prepared for comparative purposes

using the monomers disclosed by Shoji et al. in combination with the

procedure of the present invention.

(,,

For comparative purposes, a mixture of 4,4'-oxydiphthalic anhydride

(ODPA) (29.1898g, 0.0941 mole) and pyromellitic dianhydride (PMDA)

(0.6347g, 0.0029 mole) was added to a stirred solution of 3,4'-oxydianiline

(3,4'-ODA) (20.0242g, 0.1 mole)in gamma-butyrolactone (GBL) ( 228.4 ml!,

to provide a concentration of 15% solids by weight at ambient temperature.

The mixture was stirred for three hours and the phthalic anhydride endcapper

(0.9776g, 0.0066 mole) was added to control the molecular weight. Stirring

was continued overnight. The polyamic acid solution mixture became

viscous. A portion of this polyamic acid solution (approximately 25 grams)

was removed and was reserved for film casting. Glacial acetic acid (GAA)

(27 ml, 10% of the total solvent weight) was added to the remaining resin and

the reaction mixture was heated to 120°C and maintained at that temperature

overnight in order to imidize the polyamic acid. It was observed that the

polyimide began to precipitate from the solution after one hour at 120°C. The

precipitate was collected by filtration, stirred in hot ethanol for 2 hours, filtered

and dried under vacuum at 180°C overnight.
5

10

15

LAR 15083-1 -10- PATENT APPLICATION

Differential scanning calorimetry (DSC) testing showed that the

copolyimide had a melt temperature of 297.1°C, an enthalpy of 35.7 J/g and a

Tg of 230.3°C. (These properties are comparable to LaRCrM-IA.)

A film was cast from the portion of the polyamic acid solution which

was reserved prior to imidization. The polyamic acid solution was cast onto a

glass plate using a 20 mil doctor blade and was air dried in a dust-free, low

humidity chamber until it was tack free. The tack-free film was cured in a

forced-air oven at 100°, 200° and 300°C for one hour at each temperature.

Portions of the film were further cured at 350°, 371o and 400°C. After curing

at each temperature, a sufficient sample was removed for solvent resistance

testing and thermal analysis.

Solvent resistance testing was conducted by bending a strip of film and

immersing it in either acetone, methyl ethyl ketone, toluene, DMAc or

chloroform for a period of one minute. Results from this testing are provided

in Table 2.

2O

25

30

A mixture of ODPA (28.6867g, 0.0912 mole) and PMDA (1.2695g,

0.0058 mole) was added to a stirred solution of 3,4'-ODA (20.0242g, 0.1

mole) in GBL (228 ml) to provide a concentration of 15% solids by weight.

The solution was stirred for three hours and phthalic anhydride (0.9776g,

0.0066 mole) was added as an endcapper to control the molecular weight.

Stirring was continued overnight. The solution mixture became viscous and a

portion of the polyamic acid solution was reserved for casting a film. Glacial

acetic acid (27 ml) was added to the remaining resin and the reaction mixture

was heated to 120°C and maintained at that temperature overnight. It was

observed that the polyimide powder began to precipitate from the solution

after heating for one hour at 120°C. The precipitated polyimide was collected

by filtration, stirred in hot ethanol for 2 hours, filtered and dried under vacuum

at 180°C overnight. The resulting polyimide powder had a Tg of 230.7°C, a
LAR 15083-1 -11- PATENT APPLICATION

melt endotherm (Tm) of 285.3°C and an enthalpy of 39.7 J/g. The melt

viscosity at 330°C was 66,674 poise. The solvent resistance testing results

are provided in Table 2.

5

10

Example 3

The procedure of Example 1 was followed to yield a copolyimide

comprising a mixture of ODPA (27.0834g, 0.0873 mole), PMDA (2.1158g,

0.0097 mole) and 3,4'-ODA (20.0242g, 0.1 mole) in GBL (177.5 ml) to

provide a concentration of 15% solids by weight. Phthalic anhydride

(0.9776g, 0.0066 mole) was used as an endcapper and GAA (27 ml) was

used as a dehydrating agent. The resulting copolyimide had a TG of

232.5°C, a Tm of 307.0°C and an enthalpy of 33.1 J/g. The melt viscosity at

330°C was 79,498 poise. The solvent resistance is provided in Table 2.

15

20

ExamDle 4

The procedure of example 1 was followed to yield a copolyimide

comprising ODPA (22.5695g, 0.0728 mole), PMDA (5.2894g, 0.0243 mole)

and 3,4'-ODA (20.0242g, 0.1 mole) in GBL (221 ml) to provide a

concentration of 15% solids by weight. Phthalic anhydride (0.9776g, 0.0066

mole) was used as an endcapper and GAA (27 ml) was added as a

i

dehydrating agent. The resulting polyimide powder had a Tg of 233.2°C, a

Tm of 287.0°C and an enthalpy of 24.7J/g. The melt viscosity at 330°C was

81,464 poise. The solvent resistance is provided in Table 2.

25 Exam.Die 5

A mixture of p-phenylene diamine (p-PDA) (0.3244g, 0.003 mole) and

3,4'-ODA (19.4235g, 0.097 moles) was dissolved in GBL (259 ml). Next,

ODPA (30.0926g, 0.097 moles) was added at ambient condition and stirring

was continued for 3 hours. The endcapper, phthalic anhydride (0.9776g,
LAR 15083-1 -12- PATENT APPLICATION

0.0066 mole) was added and stirring was continued overnight to allow for the

formation of the polyamic acid. A portion of the polyamic acid solution was

reserved for film casting. GAA (27 ml) was added to the remaining polyamic

acid solution and the mixture was heated to approximately 120°C. The

procedure of example 1 was followed for testing the solid polyimide and the

cast film. The resulting polyimide powder had a Tg of 230.3°C, a Tm of

297.1°C, an enthalpy of 35.7 J/g and melt viscosity of 61,064 poise at 330°C.

The results from the solvent resistance testing are provided in Table 2.

10

15

Exam.Die 6

The procedure of example 1 was followed to prepare a copolyimide

comprising ODPA (30.0926g, 0.097 mole), 3,4'-ODA (18.8227g, 0.094 mole),

and p-PDA (0.6489 g, 0.006 mole) in GBL (228 ml) to provide a 15% solids

by weight solution. Phthalic anhydride (0.9776g, 0.0066 mole) was added as

an endcapper and GAA (27 ml) was added as a dehydrating agent. The

resulting polyimide powder had a Tg of 230.7°C, a Tm of 285.6°C and an

enthalpy of 33.4 J/g. The melt viscosity at 330°C was 70,278 poise. The

films cured at 371 ° and 400°C had improved solvent resistance (Table 2).

20

25

The procedure of example 1 was followed to provide a copolyimide

comprising ODPA (18.0556g, 0.058 mole), 3,4'-ODA (10.8131g, 0.054 mole),

and p-PDA (0.6489g, 0.006 mole)in N-methyl pyrrolidinone (NMP) (150 ml).

The resulting polyimide powder had a Tg of 237.8°C, a Tm of 297.8°C and an

enthalpy of 46.3 J/g. The melt viscosity at 330°C was 79,498 poise. The film

had a tensile modulus of 426.8 Ksi and the solvent resistance was excellent

(Table 2).

30
5

10

15

LAR 15083-1 -13- PATENT APPLICATION

Exam01e 8

The procedure of example 1 was followed to prepare a copolyimide

comprising ODPA (30.0926g, 0.097 mole), 3,4'-ODA (15.0182g, 0.075 mole),

p-PDA (2.7036g, 0.025 mole). Phthalic anhydride (0.9776g, 0.0066 mole),

GAA (26 ml) and GBL (216 ml) were charged. The resulting copolyimide had

a Tg of 234.6°C, a Tm of 278.7°C and an enthalpy of 26.1 J/g. The melt

viscosity at 330°C was 81,464 poise. The films had good solvent resistance

(Table 2) and the tensile modulus was 4576.8 Ksi. The Tg for films cured at

371 o and 400°C was 250.4°C and 268.9°C, respectively (Table 1).

Exam01e 9

The procedure of example 1 was followed to provide a copolyamic acid

resin comprising ODPA (655.2121g, 2.112 mole), 3,4'-ODA (396.4792g, 1.98

mole), and p-PDA (23.7917g, 0.22 mole), in NMP (1920 ml) to provide a

35.7% solids by weight solution. Phthalic anhydride (26.0691g, 0.176 mole)

was added as an endcapper. The resulting polyamic acid had an inherent

viscosity of 0.41 dL/g and Brookfield viscosity of 163,000 cps.

2O

25

Exam01e 10

The copolyamic acid resin of example 9 was used to prepare

composite laminates. The unidirectional prepreg was fabricated by both

standard drum winding procedures and a multi-purpose tape machine. The

prepreg was B-staged first in an oven set at 250°C for one hour, and then at

in a press set at 315°C for one hour without pressure. After heating at 315°C

for one hour, 1.72 MPa (250 psi) pressure was applied for 30 minutes. The

temperature was increased to 350°C and pressure applied for one hour to

yield a composite laminate. The composite was cooled in the press and the

pressure was released when the temperature was below 200°C. The

composites were tested to determine their physical properties using test
LAR 15083-1 -14-

methods which are known to those skilled in the art.

are given in Tables 3 and 4.

I

PATENT APPLICATION

Results from this testing
Me_gan_al Prope_es

SBS $_engUl, Ks_

0° Ftexural Streng_, Ksi

0° Ftexural Modulus, Msi 0° tlTRI Compression

Streng_, Ksi

Testing Condition, °C

25

93

150

177

25

93

150

177

25

93

150

177

25

Table3

IM7/LaRC'r"-IA

16.70

14.99

13.86

8.32

195.6

165.0

139.8

131.8, ",

12.3

12.0

12.9

13.2

179.9

Examt_e9

16.08

12.78

9.83

8.03

216.1

175.9

133.6

106.2

18.9

16.1

16.5

15.3

169.7

MOdUlus, isi 25 20.0 23.8

CAI Slzencj_, Ksi 25 44.3 41.4

Moclulus, Msi 25 7.9 7.5

OHC S_'encj_, Ksi 45.8

33.0

25

177

46.1

34.3

t"

3>

_O

010

CO

C_I!I

"I_

3>

.-_ mZ

"0

"13

t"0>0Z
TestType

Open Hole Compression

Strength

Compression After

Impact Strength

Open Hole Compression

Strength After Isothermal

Aging at 350°F for

1000 hours and Thermal

Cycling From -67°F to

350°F

k._yup

(0o/ +'5/90) 4 ° o

58/34/8

42/50/8

25/50/25

25/50/25

58/34/8 (I0cycles)

58/34/8 (1O0 cycles).

Table 4

Strength (ksi)

77°FtDry

64.4

54.3

49.0

Strength (ksi)

350°F/Wet

39.7

39.4

27.7

47.0

Interlaminar Shear Strength Unidirectional

43.5

Data Not Available

Data Not Available

20.2

41.6

3.6

t"

O1

O

Go

I

O3

|

>

-I

m

Z

-4

>

r-

(3

-I

o

Z
5

10

LAR 15083-1 -17- PATENT APPLICATION

The copolyamic acid resin of example 9 was used to prepare adhesive

specimens. The resin was diluted to 25% solids by weight and was brush

coated onto a 112 E-glass cloth having an A-1100 finish to form an adhesive

tape. After each coat was applied, the tape was placed into a forced-air oven

and heated for one hour each at 100 °, 175 ° and 225°C. The copolyamic acid

resin was reapplied to the cloth until the thickness was approximately 13 mil.

The tape was heated to obtain less than 2% volatiles. The prepared

adhesive tape was used to bond lap shear specimens with titanium

adherends. The specimens were heated at 325°C and 25 psi for one hour in

order for bonding to take pace. The specimens were tested at various

temperatures using conventional test methods known to those skilled in the

art. The results from this testing are given in Table 5.

15 Table 5

Test Condition LaRCTM-IA Example 9

Strength (psi) Strength (psi)

23°C 4437 4952

150°C 4554 4245

177°C 3833 3872

204°C 2104 2700
LAR 15083-1 PATENT APPLICATION

A SOLVENT RESISTANT COPOLYIMIDE

5

10

15

/_,bstract of the Disclosure

A solvent resistant copolyimide was prepared by reacting 4,4'-

oxydiphthalic anhydride with a di_mine blend comprising, based on the toial

amount of the diamine blend, about 75 to 90 mole percent of 3,4'-oxydianiline

and about 10 to 25 mole percent p-phenylene diamine. The solvent resistant

copolyimide had a higher glass transition temperature when cured at 350 °,

371° and 400°C than LaRCTM-IA. The composite prepared from the

copolyimide had similar mechanical properties to LaRCTM-IA. Films prepared

from the copolyimide were resistant to immediate breakage when exposed to

solvents such as dimethylacetamide and chloroform. The adhesive

properties of the copolyimide were maintained even after testing at 23 °, 150 °,

177 ° and 204°C.