NASA Technical Memorandum 84516 NASA-TM-84516 19820025654

LARC-TPI:A MULTI-PURPOSETHERMOPLASTICPOLYIMIDE

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Anne K. St. Clair and Terry L. St. Clair

£{BHP H;!BOPVJune 1982

f',,L{G! 61982LANGLEYRESEARCHCENTER

LIBRARY,NASA

HA.... TOl',l_VIRGINIA

National Aeronautics andSpace Adm,nis/ratJon

LangleyResearchCenterHampton, Virginia 23665

https://ntrs.nasa.gov/search.jsp?R=19820025654 2020-07-22T13:11:57+00:00Z

INTRODUCTION

Linear aromatic polyimidesare presentlyunder considerationfor appli-

cations on future aircraft and spacecraft. As a class, linear polyimidesare

attractiveto the aerospaceindustrybecause of their toughnessand flexi-

bility, remarkablethermaland thermo-oxidativestability,radiationand sol-

vent resistance, low density,and excellentmechanicaland electrical

characteristicsover a wide temperaturerange. However, the processingof

these materials is tediouscompared to other engineeringplastics. A soluble

polyamic acid precursormust first be dissolved in a high-boilingsolvent,and

later converted to the polyimideby heating to a high temperature

which causes evolutionof water and residual solvent. The preparationof void-

free moldings, large-arealaminatesor adhesive joints with such a material

becomes exceedinglydifficult.

The use of meta-substitutedaromatic diamines in the preparationof linear

polyimides has been a major advancementtoward improvingthe processabilityof

these polymersand loweringthe glass transitiontemperature(1). A further

advancementhas been the synthesisof these polyimidesin a nontoxic, low-

boiling ether solvent (2). The adhesive lap-shearstrength of a meta-oriented

polyimidewas improved2 to 5-fold by synthesisin bis(2-methoxyethyl)ether

(diglyme) (3,4). More recently,this material was used as an adhesive for bond-

ing ultrathin polyimidefilm in the proposedNASA-SolarSail Program (5). The

small-area sail joints (0.64 cm overlap) allowedan easy escape for volatiles

during processing. However,the need still exists for a high-temperatureadhes-

ive that can bond larger areas without the evolutionof volatilesand the entrap-i

ment of voids.

LARC-TPI is a linear thermoplasticpolyimidewhich is presentlybeing

developed at NASA-LangleyResearchCenter as an adhesive for the large-area

bonding of metals and films. This material is a linear polymerwhich contains

a meta-substituteddiamine and is prepared in an ether solvent. Unlike con-

ventionalpolyimides,LARC-TPI can be imidized and freed of volatilesat a

reasonably low temperature(230°C)and then be processedas a thermoplastic.

In an effort to exemplifythe multiple uses of this material, this paper re-

ports the preliminarydevelopmentof LARC-TPIas an adhesive,molding powder,

compositematrix resin, high-temperaturefilm and fiber.

EXPERIMENTAL

Preparationof LARC-TPI

The monomers used in the preparationof LARC-TPIwere 3,3',4,4'-benzo-

phenone tetracarboxylicdianhydride(BTDA) and 3,3'-diaminobenzophenone(3,3'-

(DABP). The BTDA was used as received from Gulf Chemicals*,m.p. 215°C, after

drying overnight in a vacuum oven at 140°C. The 3,3'-DABPwas obtained from

Ash Stevens, m.p. 150°C,and used as received.

The polymerizationwas performedin a closed vessel at 20°-25°Cat a

concentrationof 15% solids by weight in reagent grade diglyme. The 3,3'-DABP

(21.2 grams) was slurried in 302.6 grams of diglyme by mechanical stirring. To

this mixture, BTDA (32.2 grams) was added and stirringwas continuedfor at least

four hours to insure the complete reaction of monomers. If the polyamic acid

tended to precipitateafter an appreciableviscosityhad been reached, small

amounts of ethanolwere added to redissolvethe polymer.

The resin thus preparedwas used directly for coatingadhesive substrates,

as a compositematrix resin in the prepreggingof graphite fibers,and for

spinning fibers. The resin could be cast as a thin film onto glass and heated

to 300°C for one hour to prepare a flexible,self-supportinghigh-temperaturefilm.

The LARC-TPI resin was also precipitatedas a solid by pouring into rapidly

Use of trade names or manufacturersdoes not constitutean official endorsement,either expressedor implied,by the NationalAeronauticsand Space Administration.

2

stirringwateror methanol; a moldingpowderwas madeby dryingthis

solidand heatingto completeimidization.

Characterization

The inherent viscosityof the polyamic acid solutionwas obtained at a con-

- centrationof 0.5% in dimethylacetamideat 35°C. Thermomechanicalpropertiesof

LARC-TPI were obtained by torsionalbraid analysis (TBA).Glass braids were

coated with a 7% polymersolution and preheatedto 220°C in air before obtaining

TBA spectra. Glass transitiontemperatures(TgS) of various films, composites,

and moldingswere measured by thermomechanicalanalysis (TMA) on a DuPont 943

Analyzer in static air at a heatingrate of 5°C/min. Thermogramsof

films were obtained by thermogravimetricanalysis (TGA) by heatingat a rate of

2.5°C/min. in static air. Melt-flowpropertiesof LARC-TPImolding powder were

observed by use of a parallelplate rheometeraccessorywith the DuPont 943

ThermomechanicalAnalyzer in static air at 5°C/min.

Adhesive Bondin9

A LARC-TPI adhesive scrim cloth was prepared for bonding 2.54 cm wide 6AI-

4V titanium adherendscleanedby the Pasa Jell I07 acid surfacetreatment. The

resin was coated onto a ll2 E-glass (A-llO0finish)cloth and heated for one

hour at IO0°C and I/2 hr. at 200°C after each coat. Enough coats were applied to

produce a final cloth thicknessof 0.25-0.31mm. Single lap-shearspecimenswere

prepared by sandwichingthe cloth between primed adherendsusing a 1.27 cm over-

lap. The specimenswere bonded as follows:

" (1) RT to 325°C at 7°C/min.,apply 1.38 MPa (200 psi) at 280°C,

(2) Hold 5 min. at 325°C, and

(3) Cool under pressure.

Lap shear tests were performedon a TT-6 InstronTestingMachine according

to ASTM D-lO02.

3

Film LaminatingProcess

LARC-TPIwas used as an adhesive to bond thin polyimideKapton®H-film

measuring 0.025-0.076mm in thickness. The Kapton film was cleanedwith ethanol,

primed with a thin coat of LARC-TPI adhesive resin, and graduallyheated in air

to 220°C for one hour to remove excess solvent and complete imidization. The

primed film was then thermoplasticallybonded to another primed or unprimed

sheet of Kapton film as follows:

(1) Place sandwich between platens preheatedto 232°C,

(2) Apply 0.35-2.07MPa {50-300psi),

(3) Heat to 343°C and hold 5 min., and

(4) Cool under pressure.

Thin film laminateswere also prepared by placing a self-supportedadhe-

sive film of LARC-TPI staged to 220°C between two sheets of Kapton film and pro-

ceeding accordingto the above process. Metal-containinglaminatesWere made by

placing conductivemetal sheets or foils between primed sheets of Kapton and bond-

ing as describedabove.

Preparationof Molded Discs

Molded discs were prepared from LARC-TPI powder which had been imidizedat

220°C. Approximately20 grams of molding powder was placed in a 5.72 cm diameter

steel mold and cured by the followingcycle:

(1) Heat to 200°C in an open mold,

(2) Insertmold top and apply 6.89 MPA (lO00 psi),

(3) Heat to 2600C, and

(4) Graduallycool under pressure.

Fracturetoughnesstesting of the 0.16 cm thick discs was perfomledat the

Naval ResearchLaboratory,Washington,D.C. Round compact tension test specimens

were prepared from the LARC-TPI discs and tested for GI (the opening-modestrainc

4

energyreleaserate)(6). Flexuralstrengthand Izodimpactstrengthweremeasured

accordingto ASTM D-790and D-256,respectively.

Fabricationof Composites

Diluted LARC-TPIresin (5% solids)was appliedas an initialcoat to drum-wound

Celion 6000 graphitefibers in an effort to ensure good wettingof the fibers. The

regularresin at 15% solidscontentwas appliedto the fibers in three subsequent

coats. The prepregwas air-driedon the rotary drum, cut into 7.6 cm by 17.8 cm

segments and stackedinto a 12-ply unidirectionalpreform. The preformedbillet was

heated under full vacuumfrom room temperatureto 204°C and held for four hours.

Upon coolingto room temperatureunder vacuum,the consolidatedbillet was placed in

a matched-metalmold and laminatedin a hydraulicpress accordingto the following

cycle:

(1) RT to 335°C at 5°C/min.,

(2) Apply 4.14 MPa (600 psi) at 200°C,

(3) Hold 1/2 hour at 335°C, and

(4) Cool under pressure.

Mechanicaltests on the compositewere performedon an InstronTestingMachine

TT-6. Flexural strengthand moduluswas determinedaccordingto ASTM D-790. Short

beam shear strengthwas determinedusing a span-to-thicknessratio of 4.

Spinningof Fibers

Fibers were spun from a 15% solids LARC-TPIpolyamicacid solution into a

methanol coagulationbath at room temperature. Approximately0.69 MPa (100 psi)

nitrogen was used to pressurizethe solutionthrough a teflon spinneretwith an ori-

fice measuring .15 mm in diameter. Yellow fibers were spun onto a 7.62 cm diameter

teflon roller rotating at 25 rmp which was locatedin the coagulationbath. The

fibers were imidizedby soaking for 24 hours in a 50/50 pyridine/aceticanhydride

solution and were then dried either in air or in a forced air oven at 150°C.

Single-fibertensilepropertieswere measured at room temperature.

RESULTSAND DISCUSSION

Resin ChEmistryand Properties

LARC-TPI was synthesizedaccordingto the reaction scheme shown in Figure I.

Reaction of the monomers in the ether solventdiglymeyielded a highly viscous poly-

amic acid which had an inherentviscosityof 0.70 dl/g. The thermal imidizationof

this polyamic acid resin resulted in a linear high molecularweight polyimidewhich

could be processedas a thermoplasticdue to its unique molecular structure.

According to the TBA spectrum in Figure 2, LARC-TPI exhibiteda relativelylow

Tg of 229°C after thermal imidizationat 220°C in air. Upon furtherheating at _°C/

min. to 350°C, the polymer had a Tg of 266°C as demonstratedby the TBA spectrum in

Figure 2 on cooling from 350°C. LARC-TPIcan be processedafter imidizingat a

reasonablylow temperatureand then heated further to increase its final use temp-

erature.

LARC-TPI is a very thermo-oxidativelystable polymeras evidencedby the

thermogramsshown in Figure 3. The dynamic TGA curve obtained on film heated to

300°C in air showed essentiallyno weight loss prior to 400°C. Weight loss of the

material did not exceed 2-3% after isothermalaging at 300°C for 550 hours.

Because it is processableas a thermoplasticafter imidizationand thermally

stable at high temperatures,LARC-TPI shows potentialfor a varietyof applications

(Table l).

6

StructuralAdhesive Properties

LARC-TPIwas recentlya candidatefor the large-areabonding of an experimental

graphite compositewing panel in the NASA-SupersonicCruiseResearch (SCR) Program,

Figure 4. The materials in this programwere screenedas structuraladhesiveson

both titanium and polyimide/graphitecompositeadherends. Preliminarybonding

results on LARC-TPIwere generatedboth in-houseand in studiesat Boeing Aerospace

Company (NASA Contract NAS1-15605). LARC-TPI exhibitedexcellentlap shear

strengthson titanium at room temperature;and the elevatedtemperaturestrengths

were above minimum strengthsset by the SCR program. The increase in bond strength

after aging at 232°C was indicativeof a post-cureeffectwhich is characteristicof

LARC-TPI adhesive. Although lap-shearspecimenswere not post-curedafter bonding

in the presentstudy, a moderate post-curewould advantageouslyincreasethe Tg

and would thereforeincreasethe use temperatureof the adhesive.

The abilityof LARC-TPIas a structuraladhesivein bondingpolyimide/graphite

and polyimide/glasscompositeshas been demonstratedand reportedelsewhere (3).

Compositeand composite-to-titaniumlap shear strengthsaveraged approximately20.7

MPa (3000 psi), but failuresoccurred in the compositesrather than in the adhesive.

FilmLaminating

A needexistsin the aerospaceindustryfor reliableflexibleelectricalcir-

cuitrythatcan withstandextremetemperaturevariationsand retainflexibility.

Problemsto date havebeendue partiallyto the presenceof voidsin film laminates

causedby volatilesgeneratedby the adhesiveand/orthe inherentrigidityof some

adhesives.Becauseit is bothflexibleand imidizedpriorto bonding,LARC-TPI

showsmuch potentialas a high-temperatureadhesivefor laminatinglargeareasof

polyimidefilm.

A film-laminatingprocesshas beendevelopedwherebyfilmsprimedwitha thin

coat of LARC-TPIadhesivearebondedtogetherusingtemperatureand pressure

(Figure5). As an alternateprocess,LARC-TPIpolyamic acid adhesivefilm may be

imidizedby heatingprior to being sandwichedbetweenpolyimidefilm. When using

either processto produceflexiblecircuits,a conductivemetal may be interposed

between layersof the polyimidefilm. Metal-containinglaminateshave been made

using aluminum,brass, copper and stainlesssteel sheets or foils.

Large-areapolyimidefilm laminateswere made which varied in size from

77.4 cm2 to 645 cm2. A laminatewas also preparedusing 8 plies of polyimide

film. Larger areas and thicker laminatescan be made using the process in Figure 5

as long as the entire laminatingarea receivesan even distributionof temperature

and pressure.

In this study, over forty Kapton film laminateswere prepared,all of which

were clear yellow, flexible,and 100% void-free. ConventionalT-peel (ASTM D-1876)

and 180°-peel(ASIM D-903) testingof the film laminateswas attempted,but no data

was generatedon the adhesive. Failuresoccurred due to tearingof the Kapton film

indicatingthat the strengthof the LARC-TPIexceeds that of the Kapton film.

In additionto peel strength,the successof a flexiblefilm laminatefor cir-

cuit applicationsis determinedby its abilityto withstanda dip in hot solder.

Most laminateswill blister (due to the adhesive)after just a few seconds. LARC-

TPI lamiates,however,have withstooda full 10 seconddip in 288°C solder without

blistering.

Moldings

Molded discs were preparedfrom LARC-TPImolding powderby heatingto 260°C

under 6.89 MPa (1000 psi) pressure. Propertiesof the moldings are listed in Table

2. Discs measuring5.72 cm in diameter and 0.16 cm in thicknesshad a densityof

approximately1.40 g/cm3. Discs were flexiblebut low in Tg when heated only to

260°C during moldingwith no post cure. Higher TgS in the range of 275:C have

been achievedfor moldings pressed at higher temperatures.

8

LARC-TPImoldingsused for measuringflexural strengthwere in the form of

12.7 cm x 1.27 cm x 0.64 cm bars, and a span of 10.2 cm was employed. The deflec-

tion to break for these specimenswas nearly twice that displayedby commercial

polyimides. Data on LARC-TPImoldings was suppliedby R. T. Traskos,Rogers

" Corporation,Rogers,Connecticut 06263.

Composites

Once imidized,conventionallinearpolyimidesordinarilydo not have enough

flow duringmolding to be used as compositematrix resins. Becauseof its low Tg

and uniquemeta-orientedmolecularstructure,however,LARC-TPIhas the necessary

flow propertiesand has demonstratedthe abilityto form compositeswith graphite

fibers. The cure cycle used to mold B-stagedLARC-TPI/Celion6000 billets into com-

positesis displayedin Figure 6. The 12-ply laminatespress-moldedby this cycle

had a final thicknessof 1.73 mm. Cross-sectionsof the laminateswere examined by

an opticalmicroscopeand found to have no lines of demarcationbetweenthe resin

and fibers.

Propertiesof the LARC-TPI/Celion6000 compositesare listed in Table 3. An

averageof two specimenseach was used to obtain flexuralstrengthand moduluswith

a ±5% variationin the data. The short beam shear strengthrepresentsan average

strengthof six specimenswith a ±10% data variation. The low value for flexural

modulusmay be attributedto the high resin content(40.4% by weight) of the

composite.

Films and Fibers

Linear polyimidesare a prime choice for films and coatings in aerospace

•applicationsdue not only to their thermal stability,but becauseof their tough-

ness and flexibility(10). Tough and flexiblefilms were easily made from LARC-TPI

amic acid solutioncast onto glass plates. Propertiesshown in Table 4 are

characteristicof films air-cured1 hour each at 100°, 200°, and 300°C having a

final thicknessof approximately0.025 mm (1 mil). Tensile properties(Table4)

reportedelsewherewere reasonablein view of the fact that they were recordedon

unorientedfilms havinghad no specimenthermaltreatmentfollowingthe cure cited

above.

The direct wet-spinningof fibers from a LARC-TPIpolyamic acid solutionhas

been demonstratedby the procedureoutlinedin Figure 7. After soaking in a

pyridine/aceticanhydridebath for 24 hours, the fibers were found by infraredspec-

troscopy to be completelyimidized. Cross-sectionsof the fibers were examined by

opticalmicroscopy and found to be rounded in shape and to have solid cores.

Although the strengthsobtainedfor these fibers are low comparedto commercial

high-strengthfibers, preliminaryresultsshow strengths(tenacity= 1.33-1.46g/d)

to be comparablewith those of many common textilefibers.

CONCLUSIONS

LARC-TPI is a linear aromaticpolyimidewhich shows potentialas a thermoplas-

tic for a varietyof high-temepratureapplications. It is a high molecularweight

polymerwhich is flexible,tough, and thermooxidativelystable at elevatedtempera-

tures (300°C). Becauseof its unique meta-orientedmolecularstructure,LARC-TPI

may be processedas a thermoplasticafter imidizationand the removalof solvent.

After processing,it can be furtherheated to increasethe final use temperature.

LARC-TPI is being evaluatedprimarilyas an adhesivefor bondingmetals, com-

posites, and films. As a structuraladhesive,this new materialhas demonstrated

adequate adhesivestrengthsfor certain advancedaircraft applications. LARC-TPI is

also being evaluatedas an adhesivein the large-areabondingof polyimidefilm to

produceflexible,100% void-freelaminatesfor flexible circuit appliations. LARC-

TPI film laminateshave withstooda dip in 288°C solder and are highly resistantto

peel forces.

10

In additionto being used as an adhesive,this resin can be precipitatedto

form a molding powder and thermoplasticallymolded at 260°C. Graphite composites

have been preparedusing LARC-TPI as a matrix resin with promisingresults.

LARC-TPI also shows potentialas a materialfor making high-temperaturefilms and

for spinninghigh-temperaturefibers.

II

REFERENCES

1. V. L. Bell, "Processfor PreparingThermoplasticAromatic Polyimides,"U.S.Patent 4,094,862,June 13, 1978.

2. D. J. Progar,V. L. Bell, and T. L. St. Clair, "PolyimideAdhesives,"U.S.

Patent 4,065,345,December27, 1977.

3. T. L. St. Clair and P. J. Progar, "Solventand StructureStudiesof Novel

PolyimideAdhesives,"ACS PolymerPreprints,16(1), 538 (1975).

4. D. J. Progar and T. L. St. Clair, "PreliminaryEvaluationof a Novel Polyimide

Adhesive for BondingTitanium and Composites,"Preprints,7th NationalSAMPE

TechnicalConference,_, 53 (1975).

5. A. K. St. Clair, W. S. Slemp, and T. L. St. Clair, "High-TemperatureAdhesives

for BondingPolyimideFilm,"AdhesiveAge, Vol. 22(1), 35 (1979).

6. R. Y. Ting and R. L. Cottington,"A Comparisonof Test Methods in Polymer

Fracture Evaluation,"ACS OrganicCoatings and PlasticPreprints,41, 405

(1979).

7. T. L. St. Clair,A. K. St. Clair, and E. N, Smith, "Solubility-StructureStudy

of Polyimides,"Structure-SolubilityRelationshipsin Polymers,Ch. 15, pp.199-215,AcademicPress, Inc., New York (1977).

8. V. L. Bell, B. L. Stump, and H. Gager, "PolyimideStructure-Property

" J. Polym. Sci. Polym ChemRelationships.II. PolymersFrom IsomericDiamines,Ld., 14, 275 (1976).

9. L. T. Taylor, V. C. Carver, and A. K. St. Clair, "Incorporationof Metal Ions

Into Polyimides,"ACS SymposiumSeries, No. 121, Modificationof Polymers,pp.

71-82 (1980).

10. A. K. St. Clair, "How PolyimdesWiden Space Frontiers,"Shell Polymers,Vol.

4(2), 50 (1980).12

TABLEi, APPLICATIONSFORLARC-TPI

(I) STRUCTURALADHESIVEFORMETALS& COMPOSITES

(2) ADHESIVEFORLAMINATINGPOLYIMIDEFILM

(3) MOLDINGPOWDER

(4) COMPOSITEMATRIXRESIN

(5) HIGH-TEMPERATUREFILM

(6) HIGH-TEMPERATUREFIBER

TABLE2. PROPERTIESOFLARC-TPIMOLDINGS

DENSITY 1.40 G/CM3COMPACTTENSION 1.37 G/CM3FRACTUREENERGY 662 J/M2BEGINNINGFLOWTEMPERATURE 225°COF MOLDINGPOWDER

MAXIMUMFLOWTEMPERAIURE 255°COF MOLDINGPOWDER

TG OF DISCSMOLDEDAT 260°C 225°C(MOLDEDAT >260°C* 275°C

FLEXURALSTRENGTH 159 MPA (23 KsI)DEFLECTIONTO BREAK* 1.10CM (0-435IN)NOTCHEDIZODIMPACTSTRENGTH* 21.4N-M/M (0.4FT-LB/IN)(-64CM X 1-27CM BAR)

*R.T. TRASKOS, SPECIAL PROJECTS GROUP, LURIE R&DCENTER, ROGERS CORPORATTION,

ROGERS, CONNECTICUT

TABLE3, PROPERTIESOF LARC-TPI/CELION6000COMPOSITES

RESINCONTENT 40,4%

DENSITY 1,55g/cm3

Tg (NOPOSTCURE) 244°CFLEXURALSTRENGTH 1600MPo (232ksl)

FLEXURALMODULUS 100GPa (14,5x 103ksl)AT ROOMTEMPERATURE

SHORTBEAMSHEARSTRENGTH 43 MPo (6,3ksl)AT 177°C

TABLE4. LARC-TPIHIGH-TEMPERATUREFILM PROPERTIES

TG (FILMCUREDAT 500°C) 259°CSOLUBILITYIN ORGANICSOLVENTS(7) INSOLUBLE

TENSILESTRENGTH(8) 136 MPA (19.7KSI) _

YIELDSTRENGTH(8) 119 MPA (17.3KSI)ELONGATION(8) 4.8%

TENSILEMODULUS 3720MPA (540KSI)POLYMERDECOMPOSITIONTEMPERATURE 570°C

VOLUMERESISTIVITY(9) 2.0 x 1016OHMS-CM

0 0

,,,,,\C/_c "_C" C _15% D1g]ymeII II0 0

BTDA m,m'-DABP RT

FigureI. LARC-TPIChemistry.

Pretre0ted1 hr. 220oc

In air 266°C229°Cz

=E:< \-_1

.- \<z:-'- I \"' I,,, I

I:5 i,,, /"_ /

// Heat

-"- _ Cool/

I I I I0 lO0 200 300 400

TEMPERATURE,°C

Figure2. TorsionalBraidAnalysisof LARC-TPI.

O -- • • , ,ii

DynamicTGA _ 0 IsothermalTGA

20 300oc

40 __ 2o B...I

4-P 41-_ 60

:_ 80 DT/dt = 2,5°C/mln,,,, I I I I I I

IO0 , , f , , __ 0 200 400 6000 200 400 600

Tempereture,°C Hoursat 300°C

: Figure3. Thermogramsof LARC-TPIFilm.

DATA T1/T1 LAPSHEARSTRENGTH,TI/T1 LAPSHEARSTRENGTH• FROM MPo(psl) AFTER3000hrsat 232oc

RT 232°C MPo (psi)232oc

BOEING 36,5 13,1 20,7AEROSPACE (5300) •(1900) (3000)

NASA- 41,4 17,9LANGLEY (6000) (2600)

71.Icm

° r

] :L.'_-..................... or" _', Gr/PlComposlte LARC-TPIAdhesiveooo oooooo ooo ooooo oooooo 0

,GI/PIHoneycomb

Figure4. StructuralAdhesiveApplicationsof LARC-TPI.

PROCESS: POLYIMIDEFILMLAMINATES(I)PLACESANDWICHBETWEEN

PREHEATEDPLATENS(232°C) I Polyimidefilm I LARC-TPIADHESIVE

(2) APPLYo,q-2,1 MPaPRESSURE I Polyimidefilm. I(3)HEATTO 3430C_HOLD5 MIN, OF

(4)COOLUNDERPRESSURE •I Polyimide film I LARC-TPI

RESULTS:CLEARVOID-FREELAMINATE ADHESIVEJ Polyimide film _ FILM

/.. MULTI-PLYLAMINATES _/

I Poh(imid e film ') METAL-CONTAININGLAMINATESPot _d.f_ (AI,CU,Steel,Brass)

I Polyimide film I J Polyimide film II

J .Polyimide film J f " N!_Tal II I

J Polyimide film I I Pol¥imide film II

I Polyimide film J

Figure5. Processfor PreparingHigh-TemperatureFilmLaminates.

o 300 \• \

• _ \200 APPLY \

LLJ 4,IMPo \,,, (600psi) \I--

]00

00,5 1,0 1,5 2,0

TIME,HOURS

Figure6. Cure Cycle for LARC-TPI/CelionComposites.

_r

_-0,69 MPa(100 psi)

II _LABC;TP!_ _Teflon Spinneret

,,ll.so,ut_.n__r__ _ - __,,Coagulation Bath

PROCEDURE:(1) Polymer solution pressurized through a 0,15 mm(6 m11) spinneret onto o 7,62 cmroller,

(2) Fibers soakedfor 24 hrs In 50/50 pyrldlne/acetic anhydride,

(3) Fibers dried In air or oven @150°C,

PRELIMINARYRESULTS:Fiber Denler 23-38

Fiber Tenacity 1,33-1,46 g/d

Figure7. Spinningof LARC-TPIFibers.

1. Report No. 2. GovernmentAccessionNo. 3. Recipient'sCatalog No.NASATM-84516

4. Title and Subtitl'e 5. Report Date

June 1982LARC-TPI:A MULTI-PURPOSETHERMOPLASTICPOLYIMIDE 6 Pedo(mingOrganization(]ode

505-33-33-02

7. Author(s) 8. Performing Organ(zatlon Report No.

Anne K. St. Clair and Terry L. St. ClairlO. Work Unit No.

9. Performing Organization Name and Address

NASA-Langley Research Center il. Contractor GrantNo.Hampton, VA

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address Technical Memorandum

National Aeronauticsand Space Administration 14 SponsoringAgency CodeWashington,DC 20546

15. Supplementary Notes

This paper was presented at the 26th National SAMPESymposium, Los Angeles, CA,April 1981.

161 Abstract

A linear thermoplasticpolyimide,LARC-TPI,has been characterized

and developedfor a variety of high-temperatureapplications. In its

fully imidized form, this new material can be used as an adhesive for

bonding metals such as titanium,aluminum,copper, brass, and stainlessI

' steel. LARC-TPI is being evaluatedas a thermoplasticfor bonding

large pieces of polyimidefilm to produce flexible,I00% void-free

laminatesfor flexible circuit applications. The furtherdevelopment

of LARC-TPI as a potentialmolding powder,compositematrix resin,

high-temperaturefilm and fiber is also discussed.

171 Key Words (Suggested by Author(s)) 18. Distribution Statement

Polyimides MoldingThermoplastic FiberAdhesive FlexibleCircuitry Unclassified- UnlimitedFilmComposite SubjectCategory 27

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price"

Unclassified Unclassified 24 A02

,.30_ ForsalebytheNationalTechnicalInformationService.Springfield.Virl]inla22161