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CA2007067A1 - Composite metal-loaded carbon fibers - Google Patents

Composite metal-loaded carbon fibers

Info

Publication number
CA2007067A1
CA2007067A1 CA 2007067 CA2007067A CA2007067A1 CA 2007067 A1 CA2007067 A1 CA 2007067A1 CA 2007067 CA2007067 CA 2007067 CA 2007067 A CA2007067 A CA 2007067A CA 2007067 A1 CA2007067 A1 CA 2007067A1
Authority
CA
Canada
Prior art keywords
percent
fiber
heavy metal
fibers
metal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2007067
Other languages
French (fr)
Inventor
Martin E. Ketterer
Morton M. Glick
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CNA Holdings LLC
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of CA2007067A1 publication Critical patent/CA2007067A1/en
Abandoned legal-status Critical Current

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Classifications

    • DTEXTILES; PAPER
    • D01NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01FCHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F11/00Chemical after-treatment of artificial filaments or the like during manufacture
    • D01F11/10Chemical after-treatment of artificial filaments or the like during manufacture of carbon
    • D01F11/12Chemical after-treatment of artificial filaments or the like during manufacture of carbon with inorganic substances ; Intercalation
    • D01F11/124Boron, borides, boron nitrides
    • DTEXTILES; PAPER
    • D01NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01FCHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F11/00Chemical after-treatment of artificial filaments or the like during manufacture
    • D01F11/10Chemical after-treatment of artificial filaments or the like during manufacture of carbon
    • D01F11/12Chemical after-treatment of artificial filaments or the like during manufacture of carbon with inorganic substances ; Intercalation
    • DTEXTILES; PAPER
    • D01NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01FCHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/20Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
    • D01F9/21Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F9/22Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Inorganic Fibers (AREA)
  • Artificial Filaments (AREA)

Abstract

(h) Abstract of Disclosure Disclosed is an improved composite loaded carbon fiber and a process for its production. Incorporated within the fiber is a combination of a boron compound and a heavy metal salt wherein the heavy metal is selected from the elements contained in Groups IVB, VB and VIB of the Periodic Table. These composite metal loaded carbon fibers show high thermal oxidation resistance and low degradation when compared to prior art carbon fibers. They have great utility in the aircraft and space technology because of their high oxidation resistance and their ability to retain structure at high temperature over extended periods of time.

Description

Z~7~7 ~a) Title of Intention MPRO-vE~ CQM?O~IT~ M~TAL-~OA~r D C~BO~ _IBERS
(b) Cross Reference to Related AP~lications NONIE
~c) Statement as tO ri~hts to In~en~ion ~ade ~nder_ Federally SPonsored Research and De~elopment This invention was made with Government support unaer subcontract ~ith Science Ap~lications Interna~ional, a corporation under prime cont.act number ~AS1-1l967 aharded by the ~a~ional Aeronautics S~ace ~dministra~ion l~ASA) and under Air Force Contract Number F3361~-8~-C-~Ol9. The Go~rernment ,has certain rights to this invention.
~d; Bac~r~-~r.~ 0~ T~
1. Field of In~ention This in~ention relates to carbon fibers and a proces~ for their production. ~ore particularly, this in~ention relates to metal-loaded carbon fibers and a process for their production.

.. . ... . . . . . _ .
2. ~rior .^.rt C~rbon fibers hat~e attract~d attention as a reinforcing material for various composi~e materials aue lo ~heir ni~h strength, chemical and heat resistance and low weight. Due to these fatorable characteristics, the~ ha~-e successfully been employed as materials for aircraft, spacecraft, sports equipment and for many indus~rlal uses. Ai~nougn tnese IiDers generaiiy possess outst~nding pnysical cnaracteris~ics, they frequentl~
5u~rer ~~orU rOC_ ^xi~tio.. resist3nce at hi,~o- te~.pe-atureC in that the~ are completel~- ashe~, ~'or example, by contact with air ,: ~: ' , '' ~ .

~ ~ i z(~07~

at ~00 C after about three hours.
To impro-~e these o~idation ch~racteristics, protective s~stems ror the fibers ha~e been prepared b~ using a combination of three general approaches: surface coating, oxygen diffusion barrier layers, ~nd matrix modification.
Surfaoe coe~ing ~-ith ceramics is ~idel~ used, but the anisotropic thermal expansion of high strength/high modulus :
carbon fiber due to thermal c~cling ma~es i~ diIficult ~o maintain the integrit~ of protective barriers (with differing '-thermal e~pansions) around the reinforcing carbon fibers. ' Barrier a~-ers and ma~ri~ additi-es are also onl~ effecti~e until crac~ing occurs. In particular, in the event of PA matrix '~
breech, the exposed carbon fiber will possess the same ~ ;
~eficiencies as non-modified carbon fiber, unless o.~idation resistant carbon fibers are prepared which maintain their s'~ ~al r.'A~r--'~ a~ hi~hor t~?eraturAC. Such fibers can be '~ ''produced ~.tr. ar. G~;ida~iOn resi~ant add~tite andjor surface-coating. For example, ~I.S. Patent ~o. ~,16~,~01 discloses a process for the production of metal ~oaded, carbon ~ibers produced b~- m~reg~atin~ e preformed organic polymeric fiber hith a solution Or a specific metal compound, s'abili~ing ~hat fiber b~ a s~stem of heatin~ and stretchin~, and carbonizing the fiber ' ~Y heatin~ it to a hi~h temperature in a non-o~idizin~
atmosphere. The metal is introduced into the preformed organic polymeric fiber by dissol-ing the metal salt in a ba~h and immersin~ ~he ~iber in tha_ bath. Amon~ _he metals disclosed are -2- ''"'' '' - 2~()7~67 metals from group I~'B, group ~'B and group ~'IB of the periodic .. . . .
t~ble, as well ~s Doron, aluminum, siiicon, thorium, uranium snd plutonium. Although the '301 patent disclos~es the impregnation of a precursor fiber with certain metals, it fails to disclose the loadlng of carbon fibers ~itn a combination of boron and certain heavy metals to produce greatly improved, metal loaded carbon fibers, the impregnating of the ~letal into a pol~acr~lonitrile precurso. fiber Gr the spec.r-c p,ocess cr 'his invention.
U.S. Patent ~o. ~,197,279 discloses acrylic carbon fibers cor.'aining a phosrhorus com~oner.+ and/c- 2 bo-on com~onent Pr.c, in aadltion, conla~ning a zinc component andfor a caicium component. ~lthough this patent d-scloses the impregn2'ion of f~recursor acr~ic fibers, including pol~acr~lonitrile fi~ers, it ~ails to disclose the impregnation of a precursor fiber with a combination of boron and certain hea~y metals, as is disclosed in thi-s in;-en.ion.
U.S. Patent No. 3,803,056 discloses a process for the production of carbon fibers con~aining titanium, tant~lum, niobium, zirconium or o~ner such hea~ me~ais. nowever, tr,e patent fzils to disclose the pol~a r~lonitrile pr~cursor fiber used in the present invention and requires the introduction of from aDout G.Oi~ to about 6 percent nitrogen to tne precursor fiber. In addition, the patent process requires mixing the fibers in a hot me~al sal. solu'ion and faiis to suggest the combination impregnaiion of the fibers ~itn hea~- metals and :'' '.
boron. Thus, there are significant differences between this patent and thst of the i~stan~ inven~ion.
Accordingl~, it is object of the present inv~ntion to prepare improved composite metal loaded carbon fibers.
It is a furt~er object of this invention to prepare metal loaded carbon fibers containing boron and a heavy metal.
It is a still further object of this invention to disclose hlgn thermai o~idation resistant and 1G-~ de~rada~ion me'a~ 'oa~ed carbon fibers wherein the fibers are impregnated ~ith a combination of boron and certain he~v~ metals.
.hese and other objeots, as ~-ell as 'he s,^s2e, natu-e and uti~ization of the proaucl ana the process io produce tna~
product ~ill be apparent to those s~;illed in the art f-om a revie~ of the follo~ing detailed description and appended claims.
Ie) Summar~ of Invention In accordance with the present in~ention there is provided an ~mpro~-ed composite metal ioaàed csrbon fibe~ comprising a fiberous material containing from about 98.9 to about ~0 percent carbon o~ weight, about 0.1 to about 1~ percer.t boron and aDout i to about 1~ percent a hea~y me~ai seiectea f'rom Ihe group ^onsisting Or elements of Group I~'B, G~oup ~'B and G~oup ~I~ of ., .
the periodic table. , There is also provided a process f'or Ine proauc~ion of' tnese improved composite metal loaded carbon fibers as follo~s: ; ' a. preparing a pol~-meric f_lamen- spinning so`u~io..;

b. spinnin szid pol~meric filament solution into ' ; " , _ ~ _ ~`` ` ` Z1~7~67 filaments;
c. introducing in~o tne filaments a combination of a Doron compound and at least one heavy metal salt, wherein the hea-~y metal is selected from the group consisting of elements contained in Groups I~'B, ~'B and ~'IB or ,he periodic table;
d. insolubilizing the combination of the boron compound and the hea~-y metal salt into the filaments to form a precursor ~iber;
f. stabilizing the precursor fiber; and g. carbonizing the precursor fiber to form a combination loaded boror. and ;ea~- me.al carbofi riber.
T'hese composite metal loaded carbon fibers Aave great utilit~ because o~ their hi~h streng.h and cxidation ,resistance at hioh temperatures for use as materials for aircraft and spacecraft and for other industrial uses where high oxidation resistance is important.

-- .. - (.') D~-t-liG-A--DG-sr-rl~tion-of--nt~-n~ion The precursor carbon filament of the present invention is derived from a polymeric fibrous materiai. ~niie tbe polymeric fibrous material may ,be proauced from a reOaeneraled celiuiosic material, such as a-cr., in a pre _-~e~ embodiment, ~he fiber-formina polymer is either an acr~lonitrile homûpol~mer or an acryloni~rile copol~mer. An acryloni~rile homopolymer is particularly preferred. Suitable copol~mers commonly contain at least about 9; moi percer.t o. recur,inO acryloDitriie uni~s and up to abou~ ; mol percent Gr one o. more mono-in-1 uni~s _;_ ~\
` ~ 2~7~67 .
copolymerized therewith. Representative monovin~l units ~hich ma~ De incorporaled in tne acr~loDitriie copolymers include !, ' ~ ' ,' ~':, ' :' ' st~rene, methyl acrylate, methyl methacrYlAte, vinyl acetate, vin~l chloride, vinylidene chloride, viny:L p~ridine, ~nd the li~e. The acr~lic po~mers may be formed b~ standard polymerization processes which are well known in the srt. Minor ~uantities of preoxidation of graphitization catalysts may opiionall~- De incorporated n the bulk acr~lic pol~er prior to spinning.
The solvent utilized to form the polyacrylonitrile spinning solu'ion ~a be an~ con~e~tio~z1 s2inr.ing sol-ent and, in ~ ~:
preferred embo~iment, the soi~enl is àimetn~-iacetamide. Tne standard technical or commercial ~rade o~ dimeth~lacetamide ma~
oe employed as the solvent in the formation of the spinning solution.
The spinning solution may be prepared by dissol~-ing sufficient acr~-lic pol~-mer in the àimeth~iacetamide sol~e~t ~o yield a solution suitable Por extrusion containing from about 10 to ~û percent acr~lic pol~-mer b~ weight based upon the total weign~ of ~ne soiution, an~ preferably from aDOUt i~ to 2 pe~cer.t ~ weigh . In a ps~ticularl~ prefer~ed embodiment of the invention, the spinning solution contains the acrylic pol~mer in a concen~ration o~ ~boul 16 to ~û percenl by weight base~ upon the total weight of the solution. The low shear visCosit~r of the spinning solution should be ~thin the range of about 90 .o 3,00û
poise meæsured at -~ C. If the spinning solution lo~ shea.

2~:)7067 viscosit~ is much belo~ about 80 poise measured at 25 C, spinning brea~do~ns commonly occur. If the spinnin~ solution low shear viscosity is much above about 3,000 poise measured at 25 C, extremely high spinning pressures are required and plugging of the extrusion oriIice ~ay occur.
The spinning solutior. 2dd tionall~ ma- use lithlu~ chlo. de as a dope additive. The incorPoration of litbium chloride serves the function of louering and preser~ing upon standing the viscosit~ of the spinning solution. The desired solution fluidit~ and mobilit,~ are accordingly efficiently maintained e-~en upon the passage of time. Inclusion of lithium chloride at a level of about 0.5 to about 2 percent by ueight based on the total wei~ht of the solution reduces the iscosity of the dope by ai)out ;0 percent and allo~s the preparation of an improt~ed stabilit~ dope. Howe-~er, this impro~ement of viscosit~ ma~ be s~ .o~ g ~ .e re--e~'~os ^' ~ o u~
to about ,7 percrr.t G~ beight h'her do2es G. abo-,~ to 2' percent are used. Houever, these high percentage dopes ~a~
require ~:cessive pressure at the srinneret and reduce tha sDeed of spinnin~ belo~- those normall~ achie~ed b3 lo~er percer..age dopes. ~opes conlainir.g acr~lic pGl;mer ~ilh a concentration G~
about 16 to 18 percent produce satisfactor~ spinning, solutions ~lthout tbe addition of a lithlum chloride additive. Thus~ in a preferred embcdiment acr~lic ~ol~mer conce~trations of zbout 1~
to about 1~ percent ~ill contain no liihium ch~oride as an additi~e.

/~ ~
2~)07C~6~

If lithium chloride is add~d to the solution, it may be dissolved in the dimethylacetamide solvent either simultaneousl~
~-ith ths acrylic polyn?e~ or before or after the acrylic polymer i5 dissolved therein Minor quantities of preoxidation or graphitization catalysts may optionally be incorporated in the s~inni~ solution The spinning solution is preferably filtered, such as by passage through ~ plate anà frame press pro~ided hitn an appropriate filtration medium, prior to wet spinning in order to assure the remo~al of any extraneous solid matter which could possibl~ obstruct tne ex'rusion o.ifice au.ing the spinning operation.
Tne spinning solution, containing tne fiber forming acr~iic ~o~Smer dissol~ed therein, is e~truded into a coagulation bath under conditions capable of forming an acrylic filament ha~ing an irte~al structure ~hick is c~a~le u~on ~ubseouent th~rmal ~eatmer.t-of -~iel~lng the i~ro~ec ca~cn .i1 ~ents OI the present in~ention It has been found that acrylic filaments are produced when a coagulation bath is utilizeB ha~ing a temperature of about ~ to 4~ C Ipreferabl~ about 1~ to 3~ C) hhich consists essentialiy of about ~ to 8~ percent by weight of a non-solvent for the acr~lic ~ ~ G _ _ G ~ ~ ~ C -- ? ' ' G-- . r ~ _ the ac-~lic fila~ent. lne ~c~-c~l~erts useful rO- ~he coagulation bath includs t~s~ ~n~entionally used in a coagulation bath for acrylic filamentis such as eth~-lene gl~-coll ~706~

methanol, isopropanol, water etc. hith methanol and eth~lene gi~coi the preferred non-solvents, The preferred solvent utilized in the coagulation bath is dimethylacetamide. When dimethylacetamide is used in con~enlrations greater than about ~ pe-cent b~ h~eight, fi?ame~t breakage tends to occur at the spinneret. When emplo~ing dime~hylacetamide in the coagulation bath in concentrations less than abou~ 1~ percen. b~ weight, the resulting filamer,ts tend LG
lose their subctantially round cross section and have a tendency to exhibit a more pronounced bean-shaped configuration. Thus, in a prefe..ed em~o~imen' the coagulatic~ bath consists essential~
of about 6G to 7~ percent D~' ~eight of etAylene glycol or methanol and about 2~ to about -~0 percent b~ weigh~ of dimeth~lacetamide.
The temperature o~ the spinnin~ solution At the time of its e~trusion should be within the ran~e of about 10 ~ to a~out ~ ~

snd- pre.erskl~~ at ~bout 20 ~ to 30 C. In 8 p~rtic~lar;3-preferred embodiment of the invention, the spinning solution is ~,,ovi~ed 2_ roo-.. tempe~atu.e, e.~. ab-u~ , h~ here~;
facili~ates expeditious handling and storage of the same.
The spinnerei utilized ~uring the extrusion ma~ con~ain a single hole through which a sin~le filament is e~:truded, or r-~fA-z~l~ r~ s'i ;.~ e- ~.e~e~"- r - ~
of fila~ents m~- be simultaneousl~ Q~;'ruded in ~arn o- tow form.
For instance, tows of up to 20,000-or more, continuous filaments ma~- be formed. The spinneret pr2ferabl~- contains holes ha~ing _~_ :: ''. ' 21D0~

diameter betheen about D0 to 1~0 microns when producing relalively ;ow deni~r fiiaments having as-spun denier of about to 24 denier per ~ilament, and holes of about 300 to 500 microns when producing relatively high denier filaments having ~n as-spun den~er of about 100 to 1,~00 denier pe~ fiiament. E;trusion pressures between about 100 and 700 psi ma~ be convenientl~
selected, and preferabl~ between about 100 and 400 psi. Spinning or extrusion speeds OL about 0.5 ~G about 2~ meters per minute and preferably from about 7.5 to about 15 meters per minute ma~
be used.

. .
T~,rou~ho~ ~he ex'.usion process, the coagul~ion bath ts preferabl~ circulated. A relati~el~ constant composition wi~nin the coagula~ion bath ma~- be maintained th-ou~h the continuous hithdra~al and purification of the same. Alternati~ely, additional non-solvent may be continuously added to the coagulation bath to preserve the desired proportion of solvent to non-sol~ent wit~.in the same. lne length of time for the fibers to be held in the coagulation bath is at least about 6 seconds.
ror instance, residence ~imes OI abou~ 6 ~o 300 seconds ma~- be con~enien~i~ selec~ea. ~esioence times iess than about ~ seconàs tend to result ir. an insufficientl~; de~eloped fiber strurture hithin the as-spun filaments.
Tne resulting as-spun filament is immeaia~ely passed ~nrougn an imbibition bath after emerging from the spin bath. For greate- absorption of the borcr. and me'al sal~ into the precurscr fiber, the fiber should be preshelled ~o the greates~ extent -iO- , `` ` 20~7067 possible. For example, the precursor fiber could be preswelled in ~aler or otAer such material prior to immersio~ in the concentrated imbibing solution. The preferred preswelling agent is an aromatic alcohol.
lmbibition or impregnation of the precursor fiber can be carried out b~ sever~l methods. For example, when the metal salt is highlp soluble in water, the imbibation step can be carried ou. merel~ b~ immersin6 the shollen organic fiber in a conce~trated aqueous solution of such metal salt. In ~nother example, to impregnate the blend with ~ boron compound, the preswollen precu~sor fibe~s ma~- be spra~e~ with a hea~ bo-ic acid soiulion with a concentration of aDoul i ~ percent or iess.
A major ad~antage of the impregnation teehnique is the uniform dispersion of ver~ fine particles within the resulting fiber. To increase the extent of the impre~nation the temperature of the bath can be ele~ated as long as such elevation does not in~erfere hith~ the non-sol~e~t used in the bath._ ror example, hhen eth~lene gl~col is used as the non-solvent the temperature of the bath can be eie~ated ~ithin Ihe range of aDou L
~0 C to about 1~0 G end preferabl~ from about 80 to about 100 G.
Hohe~er, when methanol is used as a non-sGl~ent such increases in temperature would not be proper. Some ele~ation in temperature ma~ be usefùl to increase the dispersion of the particles but excess heating would not prove useful. To increase the extent of the impregna.ion, the temp^rature of the bath can be ele~a~ed, :
: ' -11- ','.. ' ;~007~ i7 :. ' . .
usually in the range of about aO C to about 150 C and preferabl~
from about 80 C to about 100 C depending on the nature of the non-solvent.
Immersion time in the imbibation bath will depend on several factors including the desired percentage of ~netal salt hithin the .i~er, ~he temperature of ~he bath a~d the speed a~ wh.ch tbe particular metal salt will be absorbed into the precursor fiber.
In preferred embodiment the immersion tim~ at preferred temperatures is from about 0.5 to about 1~ seconds. If the preferred metal salt is not readil~ dissol~able in water, other suitable solvents can be used, sucA as bromoform, carbon tetrachloride, diethyl ether, nitrobenzene, methanol and other alcohols and other organic materials that do not interferingl~
reac~ ~ith the precursor fiber.
The metal salts employed for impregnation are salts of ~ e-r^-~. -a ~.e~ e~_lc ~ .E:e -9-~ S _ ~'e tempera~ures; Included hi-thin the hea~ metals sre ~he grou~
consisting of elements of groups I~rB, group ~B and group VIB of the pQriodic table and are prQf~rabl~ selected from the grou~
consisting of titanium, tan~alum, niobiuc., chro~lium, mol~-bdenum, anadium, nafnium, ~irconium and thorium and, mos' prefe.abl~, tantalum, tit~nium, niobium, zirconium and hafnium.
~ he ro1 Ub !~ S9 lts of there metals usQful 40r the DI~OS5' of this invention include salts h'i ~ h s~ror.~ and ~eal ac ds, preferabl~ those which have high solubilit~-. An~- salt of the neav~r metals which is soluble in the imbibina fluid can be used.

- 2~070~

T~pical metal salts employed include chloridesl fluorides, aceta~es, oxaia~es and any other metal salt readil~ soluble in the chosen imbibation bath. For example, when niobium is the .
chosen heavy metal, niobium pentachloride is a preferred niobium sait.
The amount of the metal salt to be added to the fiber is, o~
course, dependant upon the desired concentration of metal in the finai pro~uct. The concerltra~iGn of the me'al in the fiber increases as the carbonization process is conducted. Thus, to produce carbon fibers with concentration of metal from about 0.
to about 20 peroen~ ~he _oncent.a'ion of 'he met 1 in 'he fiber prior to carbonation sbould range from ~bout ~.o perceni IO about 10 percer.~.
Although the concentration of tbe metal salt within the fiber follo~ing imbibation may vary, in a preferred embodiment the percentage of metal salt incorporated in the precursor fiber should be from-about 0.~ t~..about 1~ percent based on tne. totsl weight of the precursor fiber.
L;ading boron into the precursor fiber is somewnat more complicatec and usuaiiy requires e~posure OI lnê prêCUrSOr Iiber .
to moro thæn one bath containing a boron compound. In a preferred process for adding boron to the precursor fiber, a solution of boric acid witn a concentration Irom aDoU~ 1 to about 1~ percent may be added to the coagulation bath or incorporated in'o the metal sal ~ imbibatio3 bath. Furthe-, boric ac d can be combined with other liquids durino subsequent drawing or dr~;ing ,,,, :,, ", -.~ ., ~ :. :
-i3-:, ' r~ ~ 20C~7067 ;

operations to increase the concentration of the boron in and on Ine precursor fiber. After each treatment ~ith the bGric aci~
the fibers are preferably lightly riDsed with a ~ater ~ash to remove any excess boric acid from the fiber surface. By these additional tre2tments ~ith boric ac'd, an increase in the percentage of boron in the precursor fiber is accomplished such that the preeursor fiber prior to carbonizatiDn has a loading of f.o~, about 0.1 ~e.cer.t ',. absut ; pe.cent boron ~ased or. t~.e total ~ei~ht of the precursor fiber.
Following the imbibition step, the imbibed metal must be 13solubilized so it does nc: ~as~. out Or ~ ho fiber n subsequent treatmenls. '~arious ~ecnniques can be used to insoiubiiize the be~s con'aLning the me'al. For e~ample, the fibers mây be insolubilized by treating the fiber with a chemical to secure the metal within the fiber, For example ~hen tantalum pentachloride is used as a salt, it is insolubled by converting it to tantalum o~ide b~ treatin8 Ihe- tbe fiber containin~ the tantaiu~
pentachloride ~ith aqueous ammonia. The aqueous ammonia is collecleu in a tray througn ~-nicn the fibers are passed around s~ewed roii, erfectivei~ gi~ing .he yarn an ai~aiine dip treatment. Ihis dip tray is constantl~ ~ithdra~n and r,ecirculated to l;eep the ammonia fresh. ~any other ,procedures can De utiiized for ~ne insoiubiization of tbe Iibers as iong as tne metal is sufIiciently insolubiiized ~hat it does nol ~ash OUI
ot- the .Lbers on subsequent ..^a nont. I'ne concen~ra'-on G'- the ammonia in the insolublization bâth ~.a~ range from about 10 . :~ ,~ :, . .,: . ., . ~ . . - . .. . . ..

70~;7 percent to about 40 percent.
AI~er insolubilization the fibers can be hashed in a ~ater bath to remove any excess AmmOnia. Various techniques m~y be used for the remov~l of the e~cess solution include blotting tho-oughi~ ~ith cloths, ~acuum filtration and ~ash baths. In a preferred embodiment~ the filament is next washed with water to remove not onl~ e~;cess solution but also all residual ~mountc of so'Yen., coagulatior. bath, a..J inGr~anic com~ound (~ hium chloride).
The hater wash treatment is conveniently conducted in an n-lir.e oper2~icn arte~ ~he ~ilamen lea~es the imbiba ion and inSoiUDiliZatiOn bath. Conventionai fila~ent ~ash roils ma~ be u~ilized. The filamen~ alte~na~i~el~ may be ~ashed ~ith ~Pter h~hile hound upon a perforated bobbin, or by the use of other washing means, as wlll be apparent to those s~illed in the art.
The as-spun and washed acrylic filament is drawn or stre~ched from ~bout 1~ *imes its original length up to the point at which the filament breaks, to orient the same and to thereb~- ennance its tensile properties. Total drah ra,ios from about i.~ o i~:i may commoniy be seiected. lhe drawirlg is common~y conducted at an ele~ated temperature and preferably ~t a total draw ratio of between about 2:1 and 12:1. The dense inlernal filament s~ructure makes possiDle tne use oî ~he relatively high total draw ra~ios indicated. As ~iil De apparent to ~hose s~.illed in .he ar,, ,he dra~ing of the aC-spun and ~ashed acr-;lic filament ma-~- be conducted by a ~-arie+y o.

, ~ )70~7 techniques. For instance, it is possible for the drahing to be conduc~ed ~hile the filament is (a) immersed in a hea~et liquid draw medium, (b) suspended in a heated gaseous stmosphere, ~e.g., at a temperature of about 120 to about 200 C) or (c) in contact hith a heated solid surface (e.g., at a temper~ture of aDOUt 130 IO ilû C). If desired, the totai drah imparted to the filament ma~- be conducted b~- a combin2tion of the foregoing techr.iques.
~hen draw techniques ~b) and (c1 are utilized, it is essential that the acr~lic filament be pro~ided to the draw zone in sn essentiall~ dr~- form. ~'hen drah technique ~a) is employed, the acrylic filament is subsequentl~ washed to remove the drah medium and is dried. Additionally, the liquid draw medium ~ay also ser~e a washing and/or coagulating function hherein residual quantities of dimethylacetamide are removed from the ~ater hashed fiber.
h a ~ re~ C~ J ' ru~h~ ir.;~ ^ r. ~ ~.e -~ GS `. _ ~
acr~lic filament' i-s''at leas~ pa'r~iaii~ arahn hniie immersed in a hot liquid bath. In a preferred embodiment the filament is dra~n hh~7e imme-se~ in _ ho' h-â'e- bat~. m~i nt2ir.od 2+ a tempQratu-Q

from about 80 C to about 100 C and at a draw ratio of about 1:1 to about 3:1. When additionall~r boron is to be added to the fiber, the bath hater ma~ contain boric acid in the range from abou L 5 LU a~O'u ~ ~ O ~erC7h ~ . ~f ~r t~ ,.o~ ~at~r,'bvric ~
~he filamen~s ma~ be ~ashea in a ha~er hash a~ relati~e'~- cool 'em~e-~! -es fr^2 abou' 10 ~^ a~out 50 C.
In another preferred embodiment of the in~ention, the --lti--"
-: . ,. . : .

., .. .... , ,. ... , . ~ ~. . :

'~ Z~)7~
~, .
filament ma~- be drahn hhile immersed in a hot gl~cerin bath at a temperature of about 80 to about llO C and at a draw ratio of about 1.5:1 to about 3~ ashed in cool water ~e.g., at e temperature of about 10 to about 50 C), and subsequentlY drawn at a drah ratio of abou~ 3:1 tO about 6:} hhile in contact ~ith a hot snoe at a ~empera~ure of about 10G to about ~G C ~nd preferably at a temperature of About 1~0 to about 160 C.
The dra~n acri-lic filaments optionally ma~- be plied to form ~-arns or to~-s of increased total denier as ~ill be appa~ent to those s~illed in the art, prior to thermai conversion into the impro~ed carbon filaments of the present in~ention, as described ~e-o2~tsr.
The metal/boron loaded prec~sor fiber is stzbili2ed in preparation for the carbonization step. ~o stabilize the fibers the metal compound imbibed organic fibers are heated under controlled conditions, to a temperature of about 200 C to about ~ .ende. 'he fibar .. lamm2~'e. I~ is ne_essa-~- lo he2' the metal compound imbibed fiber at a rate sufficiently lo~ to a~oid isnition of the fiber. , The first heating step may be preformed in a nonoxidin~
ir.err a mos~'~ore~ G~ 7~or e~:ample, that pro~iàed ~;~ r.i~rogorl, helium, argon, neon and the like or a ~acuum. Ho~e~e., if i' is ~-desir2blo t^ re~uco tho quar.tity o4 oarbo~ remeiRin~ from the polymer pyrolysis step, a portion or all of the first heating s~ep m2.. be preformed ln an ox~gen cor.taininO a^mcsphere. ~n ~he stabilization or preoxidation process, the fiber undergoes a ;

. .

,......
:. .

~07C~67 series Or reactions which oxidize and cross lin~ the molecules.
.
~he net reaction is exothermic and the oxidation reaction tends to form a s~in core structure in the fiber cross section. To control the exotherm and the skin core formation, stabiliz~tion is done in a mu~ti-staae process ~-ith incremental i~creases in temperature as the fiber slowl~ passes through the various stages. Controlled tension is maintained to prevent misorien.ation of t,.e mo~ecular chains and a correspondin~ loss in tensile propert~.
The precursory fiber is fed through a tensioning device and feed role svand to a drye-. ~he ma-e -al is heate~ to a temperature from ~bout 180 G to about 210 C to remo~e any resioual sol~en~, moisture, and lubricant. During this dr~-ing the fibers usually undergoes a shrin~age of abou~ 1 to approximately 10 percent. The yarn then passes through a series of ovens with incremental increases in temperature from a~out 6~0 C-to about ~v8~ C.~ An'~add ~ional iO to abou~ '~ percen-shrin~age is experienced as the yarn undergoes the stabilization.
~s indirated, roll speed are set to 2^commodzte the shrinXa~e and to ~air.tain an accepvable tensiGr. le-;e . As the G~idation and the cross iinking reactions progress, the -,;arn ~,a~- change ccio~s until it finally appears blac~. After heating for a period from about 1 to Pbout D hour9 ~t the ele~ated temperature~ the ,~arn i~
sufficientl,~ o~:idiived snd cross lin~ed to proceed ~th the carb~nization step.
The stabilized ,~-arn is processed throu~h an induction ., '' ` 2~)~)7067 furnace purged with nitrogen. Carbonization temperatures range from about 12~0 C to about 2~00 C and are dependant upon the specific metal additi~e and the desired final species. During carbonization, elements such as hydrogen, oxygen and nitrogen are graduall~ evolved fro~ the fibers structure. The resul L is ~,T~SS l~ss f~o~ ~he precurso. fiber of ~ar~ing percenta~es ~hile the loaded metal is generall~ full~ retainecl. The ~eight percent of the metal increases as the mass ioss of the fiber increases.
However, under certain circumstances the percentage conce,ntration of the boron ~ill not increase, because of its loss during the s~abili-ation or carbonizaticn p.ocesses. Pe~io~s from about to about ~ hours may be employed, while much shorter times may also be employed.
The fibers produced b~- this process are comprised of fiberous materials containin~ b~ weight from about 99 percent to Pbc~t 7Q percent car~on and about 1 percent to about 30 percent a hea-;~ me~al selec~ed ~~om the-elements co~tained in ~roup I~B, group ~'B and group ~'IB of the periodic table and boron. khen combin~tion loading using both a heav~ metal selected from the elements of groups T~'R ~ grouip ~JR an.~ grou~ ~'IB of th~ periodic ~able and boron are used, Lhe composi Le me Lal loaded carbon ribe~
is comprised o~' a fiberous materials containing by weight of about 98.6 to about 70 percent carbon. about 0.5 to about 1 percent boron and about 1 to about 1~ percent the heavy metal.
Tne composite metal loaded fibers ha-e sho~-n surprisin~
si~nificant improvements o~er unloaàed fibers or fibGrs loaded - :
with a sin~le metai. In particular, these fibers ha~e signiIicanli~ iower ra~es o~ oxidation than unloaded or singie metal loaded carbon fibers and exhibit a higher retention of tensile strength after being exposed to an oxidizing environment.
.nes- bigh strength, ;,ir. modulus carb&n fibers ~itn boron and hea~ metals impregnated thereiD can be of great use in those situations hhere high temperature stabilit~ is important such as in aircraIt or space equipmen;. In ~ar,ic~la., the abilit~ .o ~esist degradation at high temperature alon~ ~ith the hi~h tensile strength are ~aluable qualities which are quite useful in materi~ls _or military equip~er., ~-hich is s~bjected to ~ bh temperature and stress. In addition, tne fiDers can De used IO
produce produc,s ~hich maintain their structural ir.~e~rit-;
~ithout the use of protecti~e coatings.
The ~ollohing examples are given as specific illustrations of the invention. All parts and percenta~es are by ~eight unless other~ise s~a~ed. It should be ~naers;ood _no~e~er that zhe in~ention is not limited to the specific details set forth in the examples.
~x_mpie 1 A 1S ~-e~t pe.cent po!yacr~lonitrile ho~.opol~mer dissol~e~
in dimethylacetamide solution ~as e~truded at a rate of /.9 grams per minute through ~ - 300 hole, 10~ micron diame~er spinnerels lnto a spin bath containing 30 percent dimethylacetamide and rO
percer.t mezhanol. I..e s~'ie~ precursGr f.bers ~e;e then ~a sec hrou~h a dip solution contair.ing ~ heirnt percent TaCij, r . . . .: .. , ; . . . . ;:.:

, .. : . ~. , , , ,, . ,, ~ . , 20070~

percent H3B03, 18 percent dimeth~lacetamide and 73 percent methar,ol to incorporate the t~ntalum and boron into the precursor fiber. The dip bath ~as maintained ~t a temperature of about 25 C. After passing through the dip bath the filaments were ~ashed ~ith a 28 percent aqueous ammo~ium solution and ar.
adcitional ~a~er - nse ~. a rz.e of 10 meters per m~nute. The fibers ~ere then subjected to a hot ~ater draw containing ~ 10 percent H3B03 solution at 8~ C at a draw ratio of 2.8:l. The fibers here then ~ashed a~ain in a ~ater hssh bath at a line speed of 28 meters per minute and then dried at a 108 C on a heated roll. The fiber ~as then drahn at a draw r2tio of 2.~
in a steam tube maintained at a tempera~ure of 12~ C . .he fibers were then heated again at a temperature of 108 C, on a heate~ ro1' at a roll speed of tO me.,ers per minute. Anal~sis of the .ibers sho~ed 1 percer.' b~ ~ei5h' ~f tan~alum and 2.6 percent boron loadina.
~ he fiber here tnen stab.li~ed b-j feeding the~ th.ou~h a dr~in~ stage. The feed rate was 10 inches per mi~ute and the fibe-s ~'ere dried at 195 C for g.8 minutes, 220 C for 22.1 minutes, 2~0 C for 86 minutes, 260 C for 91.2 minutes and 2~ C
for 96.1 minutes. The overall shrin~a~e of the fiber after this . ...
dr~ g pro~-ess has lc.i percer.'.

Tbe fibers were then carboni~ed at a temperature o. a~ou~

~,OS0 C in an ir.duc.ion .urnace fo. abou. ~ ~inutes. The ~eed rate of the fibers into the o~en ~'8S 21.2~ inches per minute. - -The atmosphere of the o~en has flushed ~ith nitro~en during the ''' . ,~

'': . ' .

` ` ` 2007~)67 carboniza~ion process.
The carbon fibers showing i.5 percent tantalum a~d ~.9 percent boron e~hibited a tensile strength of 270 ~si and a modulus of 38.2 Msi. (ASTM D3379 and D1577~. After oxidation ~t a temperature of 500 C for 21 hours (ASTM D~10,~, .ensile s~. ength ~as 236 ~a~ ~'' tk en in~tial modulus of 35.9 Msi.
ThermGgra~ometric analysis of the carbon fiber at a heating rate of 20 per minute in air showed a 6 percent weight loss at 860 C
and a ~0 percent wei~ht retention at 1000 C.
Exam~le 2 ~-As a comparison, an unloaded polyacrylonitrile precursor fiber was prepared and processed into carbon fiber. A 15 weight percent pol~acr~rlonitrile homopolymer solution in dimethylacetamide was extruded at a rate o~ 7.9 grams of pol~er per minute through two 300 hole, 100 micron diameter spinnerets inlo a spir. bath contai~ir.~ 30~ ~Lmeth~. ~ a~etamid~ ~ a~ou' .^
percent methanol. The swollen fiDers were then ~:ashed in a hater bath on thO washrolls at a rate of 10 meters per minute. The ri~er 'naa t~e-. d-a'~ .... 2 ~C_ h'a_e_ ~aLh ma~t2ine~ ~L the -~
temperature of 92 C at a drah ratio of 2.8 to 1. The fibers here then thice hashed ~gain in a water wash and then dried on a heated roll at a roll rate of 28 meters per ~inute at 108 C. The fibers were then drawn ln a steam tu~e heated to a ~empera~ure 124 C at a drah~ ratio of Z.6 to 1 and rolled on hea~ed rolls `maintaining at a tempera~ure of 108 C at a ra~e of 10.2 me~crs per minute.

.. . ~ . ., ,., . . ~ . .. . : , , .

-. ,. ~
. . , . ~ :

-` 2~7~:)67 ~ ~
These fibers ~ere then stabilied b~- heating in ~n o~en at temperatures of 196 C for 9.8 ~inutes, 235 C for 22.1 minute~, 2~0 C for 86.2 minutes, 260 C for 93.2 minutes and 275 C for 95.3 minutes. The fibers were then carbonized at a feed rate of 21.25 inches per minute at a temperature of about 2,050 in nitrogen atmosphere. Tne unloaded carbon fibers sho~ed a 5 percent ~-eight loss at l90 C and a residue of onl~ l.ô percent at 900 C.
ExamPle 3 An 16 ~eight percent polracr~lonitrile homGpol~er dissol~ed in dimethylacetamide solution was extruded at a rate l.9 grams per minute through 2 - 300 hole, 100 micron diameter spinnerets nt^ D sp'n bath co~ain~ng ~0 perce~t d~methvlacetamide Pnd 70 percen~ methanol. The s~ollen p-ecursor fibers h-ere thsn passed through a dip solution containing 14 percent ZrO~Ac]~, 1.0 percent H3BO3, 18 percent dimethylacetamide and 67 percent water to incorporate the zirconium and boron into the precursor fiber.

~he dip batn has maintained at a temperature G~ abGU' 2~ C.
After passing through the dip bath the filament.s were ~-ashed ~ith a 28 percent aqueous ammonium solution and an additional ~ater rinse at a rate of 10.~ meters per minute. ~he fibers ~-ere then suDjected ~o a nol hater drah soiution at 92 o. lhe I ibers were ~ ha3he~ agPln ~n a hater hash bath a' a l_ne s~eed Or ~9.6 meters per minute anà then dried at a 108 C on a heated roll.
~he ~iber has then drahn at a d-a~ -atio of 2.0:1 in a stea~ tube maintained at a temperature of 12} C. The fibers here then heated again at a temperature of 108 C on a heated roll at a roll ~ `- Z~7CJ67 speed of 60 meters per minute. Anal~sis of the fiber showed 2.12 weign~ perce~t zirconium and G.~ percent b~ron.
The fiber were then stabilized b~ feeding them through a drying stage. The feed rate was 8.~ inches per minute and the fibers were tried a' 21û C fvr about 10 minutes, 23û C for about 2û minutes, 2~ ~ fo. abo~t 70 minuLes~ 265 C for abou~ ~0 minutes and 27~ C for about ~0 minutes. The o~-erall shr n~age of the fiber after this dr~ing process was 16 percent.
The ribe s ~ere then carbor.i~ed at a temperature of abGut 2,û~0 C in an induction furnace for abGut 2 minutes. ~he feed rate of the fibers into the oYen was 16 inches per minute. The a+mos2h_-e cf t~.e o~en. wQs flusked witk nitrogen during the carbonization process.
The carbon fibers exhibited a tensile stren~th of 232.1 ~si, a modulus of 32.1 Msi (ASTM D3379 and D1677~ and elongation of 0.,2 percent. After oxidation at a ~emperature of ~20 C for 24 hours ~.~ST~ DA102~, tensile strength ~as 232.1 Xsi, i~i+ial modulus h~as 31.8 Msi and elongation was 0.76 percent.
Thermogravometric anal~sis in air showed a ~6 percent weight loss after 300 minutes of 700 C.

E~;D rn~l e A 16 heigh~ percent pol~acr~lo~itrile homopol~-mer disso~ed in dimo+h.~aco amido solution ~as e~;truded at a r~te of 7.9 grams per minute through 2 - 3~0 hole, 100 micron diameter spinnerets into a s~in ba'h -on~aining 3G percen dimeLh~-lacetamide and ,0 percent methanol. The swollen precursor fibers were then passed .. . .

~706~7 through a dip solution containing 18 percent ZrO[Ac]2, 2.0 percent H3BO3, 18 percent dimeth,~lacetamide and 62 percent water to incorporate the zir,conium and boron into he precursor fiber.

The dip bath was maintained at a temperature of about 25 C.
After passing through the dip batb the filaments were washed with a 28 percent a~ueous ammonium solutiGn and an additional ~-ater rinse at a rate of 10.5 ~eters per minute. The fibers ~ere the~

subjected to a hot hater drau at 90 C. The fibers were then ~ashed again in a ~a'er h-ash bath at a line speed of 29.6 meters per minute and then dried at a 108 C on a heated roll at a roll ~ ' '. ` I' t. . `' ' . ..
speed of 60 meters per minute. Analysis of the fiber showed 3.9 weigrlL percent zircvrl um ar.J ^.3~ pe,ce..~ b_-o,..
The fiber here then stabilized b~ ,eeding them through a ,' dr~in~ stage. The feed rate has 8.5 inches per minute and the flbers ~.ere c`ried at 210 C for about 10 minutes, ~0 C for about 20 minutes, 265C for about 70 minutes, 26S C for about 70 ' minutes Rnd 275 C for about 70 minutes. Tne o~eraii shrinka~e of ~;
the fi~er after this dr~ing process ~'2S 16 percent.
The fibe~s wero then carbonized at at tempera~ure of about 2,050 C in an induction furnace for about ' minutes. The feed '~ ' rate of the fibers into the o~en was 16 inches per minute. The ''', a~mosphere of the o~en h~as ~lushe~ ~ith nitro~en d~-in~ the ,'', carbonization process.
The ca-bo3 f_bers e~:h~bited a ter.sile strength of 22~.7 Ksi, - ;
2 modulus of "9.~ ~si (AST~ D3379 and D1577) and elongation of , ''-' 0.l6 percent. A.ter oxidation a' a temperature oS 520 C fo. ~4 ~; ' ' -2~-''~'' :' .
. .

, .. , . .. , . .. , . . ., . i . ,.. . , . ~ .. . . .. . . ..

` 2007067 ~

hours (ASTM D~10 ), tensile strength h'~S 188.6 ~si, initial moduius was 29.0 Msi and eiongation was 0.6~ percent.
Thermogra~ometric anal~sis showed a 36 perce!nt weight loss after 300 minutes at 700 C in air.
Exa~le ~
A ~6 ~eight p~~cent p~l~acr~;lonit~ile homopolymer dissolvet in dimeth~lacetamide solution ~as extruded at a rate of 7.9 gra~s per minute through 2 - 300 hole, lO0 micron diameter spinnerets into a spin bath containing 30 percent dimethylaceta~ide and 70 percent methanol. The swollen precursor,fibers were then passed throu~ a dip sGlu~ion containing ~ percent TaCi~, 6 percent H~B0~, 18 percent dimethylacetamide and 69 percent methanol to ., ~
incorporate the tantalum and boron into the precursor fiber. The dip bath was maintained at a temperature of about 25 C. Af~er passing through the dip bath the filaments were washed hith a 28 percent aqueous ammonium solution ana an aadi~ionai h~a~er rinse .. . . . ... . ..
at a rate of 10 meters per minute. The fibers were then subjected to a hot water dra~ containing a 5 percent H3B03 solution at 87 C. The fibers were then ~ashed again in a ha~er wash bath at a line speed of 28 meters per minute and then dried a' a 10~ C on a heated roll. ~e fiber has then dra~n a second time at a draw ratio of 2.5 to 1 in a steam tube maintained at a Le~per a ~ur e Or 1~ C. The fibe s ~-e~e t~er. hea~ed again ~' a tem~erature of 108 C on 8 heated roll at a roll speed of lO
meters per minute. Anal,~sis of ~he fiber showed a 4.4 weight percent zirconium and 2.3 percent boron.
-~6-,: . , : :;: , ;~

-- ` Z~al7~67 ~:
The fiber were then stabilized b~ feeding them throug~ a dr~ing staj~e. The feed rate was ~.~ ir.ches per minule and the fibers were dried at 195 C for about 10 m~nutes, 220 C ~or about 20 minutes, 250 C for about 70 minutes, 260 C for i~bout 70 minutes and 275 C for a .. o~-erall shrin~age of the fiber afler this ar~ing process ~as 1~ percent.
The fibers here then carbonized at a temperature of about 2,050 C in an induction furnace for about 2 minutes. The feed rate o. the fibers into the o~en was iC inches per minute. The atmosphere of the oven was flushed with nitrogen during the ;~
carbonization process.
Thei ~arbon ribei~s exh b ted a ~ensile ctre-.g+h of 73 I's~, a modulus of 33,8 Msi (~STM D3379 and Dl~.r) and elongation of 0.81 p~rcent, ~fter o~;ida~ion a~ a temperature cf 5~0 C for ~4 hours (AST~ Di~102), tensile stren~th has 25~.8 Ksi, initial modulus has 32.4 Msi and elongation was 0.80 percent. Thermogravometric .
anal~-sis in air showed a 10 per^ent ~eight loss after 3Q0 r~inutes at ~00C.
ExamPle 6 .~s a comparison, an unloaded pol~acr~lonitrile precursor r-~er has ~e~a~ed an~ ~.ocesse~ ~nto ca~~on fi~sr. .~ 16 heigh' percent pol~acr~:lonitrile homopol~mer solu~ion in ~imet~ laceta~ e has e~;truded at a a -a'e of 18.1 grams Or polymer per minute through four 300 hole, 100 micron diameter spinnerets into a spir. bath containing 30~O dir.e~hylacetamiàe ar.d about 70 percent methanol. The fibers were then washed in a -2~- , .. . .

- ZO~)70~;7 water bath on two washrolls at a rate of 10.7 meters per minute.
The fibers were then drawn in ~ hot gl~cerine batb maintained at the temperature of 9~ C a~ a dra~- ration of 3.3 to 1. The ~ibers were then t~ice washed again in a hater wash and then dried on a heated roll at ~ roll rate of 35 meters per minute at 108 C. The fibers were then drah~ o-er a not shoe heated io a tempera~ure of 180 G at a dra~ ratio of ~.3 to 1 to a final roll speed of 80 meters per minute.
These fibers ~ere then s~abili~ed by heating in an oven at temperatures of 195 C for 9.8 minutes, 23~ for 22.1 minutes, 250 C for 86.2 minutes, 260 C for 93.2 minutes and 2~5 C for 95.3 minutes. The fibers were tnen carDonized at a ~eed rate of 20 inches per minute at a termperature of about 2,060 in a nitrogen at~os~here. ~he unloaded ca bon ~lDers e~;hibited a tensile strength OL 32~.~ E;si, a modulus Or ~9 3 Msi, and an elongat-on of 0.8~ percent. After oxidation at a termperature of 520 C for .. , . .. . .. . ~
24 hours, tensile strength was 115.6 I;si, modulus was 36.4 Msi, and elongation ~as 0.41 pe-cent. Thermogra~imetric anal~-sis in air sh~e~ a 88 perce..~ ~e.~ loss af~er 300 ~ nutes a' .00 C.
As is apparent, the filaments produced from this process ~ith a combination of boron and heavy metals exhibited enhanced proper~ies, speciLically enhanced cxida~ion charac e-is~ cs, particuiarl~ afte~ hea~ing, and thermal stability. Fur~her, ~he ~eig~.'/st-ength reten'icn ~as a slcnificant improvement o~-er prior art unloaded or single metal loaded fibers.

-,8-

Claims (13)

1. A composite metal loaded carbon fiber comprising a fiberous material containing by weight from about 98.9 to about 70 percent carbon, about 0.1 to about 15 percent boron and about 0.5 to about 15 percent a heavy metal selected from elements of group IVB, group VB and group VIB of the periodic table.
2. The metal loaded carbon fiber of Claim 1 wherein the heavy metal is tantalum.
3. The metal loaded carbon fiber of Claim 1 wherein the heavy metal is niobium.
4. The metal loaded carbon fiber of Claim 1 wherein the heavy metal is hafnium.
5. The metal loaded carbon fibers of Claim 1 wherein the heavy metal is zirconium.
6. A process for the production of a composite metal loaded carbon fiber comprising:
a. preparing a polymeric filament spinning solution;
b. spinning said polymeric filament solution into a polymeric filament;
c. introducing into the polymeric filament a combination of a boron compound and at least one heavy metal salt, wherein the heavy metal is selected from the group consisting of elements in group IVB, group VB and group VIB of the periodic table;
d. insolubilizing the combination of the boron compound and the heavy metal salt within the polymeric filament to form a precursor fiber;

e. stabilizing the precursor fiber; and f. carbonizing the precursor fiber to form a composite boron and heavy metal loaded carbon fiber.
7. The process of Claim 5 wherein the heavy metal is tantalum.
8. The process of Claim 5 wherein the heavy metal is niobium.
9. The process of Claim 5 wherein the heavy metal is hafnium.
10. The process of Claim 5 wherein the heavy metal is zirconium.
11. The process of Claim 5 wherein the polymeric filament is either an acrylonitrile homopolymer or an acrylonitrile copolymer.
12. The process of Claim 5 wherein the polymeric filament spinning solution contains about 10 to 30 percent polymeric material by weight based on the total weight of the solution.
13. The process of Claim 5 wherein the precursor fiber contains from about 0.1 to about 5% by weight a boron compound and about 0.5 to about 15% by weight a heavy metal salt wherein the heavy metal is selected from the group consisting of elements contained in Group IVB, Group VB and Group VIB of the Periodic Table.
CA 2007067 1989-01-11 1990-01-03 Composite metal-loaded carbon fibers Abandoned CA2007067A1 (en)

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WO2021252582A1 (en) * 2020-06-10 2021-12-16 Cytec Industries, Inc. A process for producing polymer fiber having at least one additive, and carbon fibers made therefrom

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ES2154710T3 (en) 1994-12-16 2001-04-16 Hoechst Trevira Gmbh & Co Kg HYBRID THREAD AND DEFORMABLE TEXTILE MATERIAL PERMANENTLY SHRINKABLE AND SHRINKED, MANUFACTURED FROM THE SAME, ITS MANUFACTURE AND USE.
DE19513506A1 (en) * 1995-04-10 1996-10-17 Hoechst Ag Hybrid yarn and permanently deformable textile material made from it, its production and use
US6820406B2 (en) 2001-05-14 2004-11-23 Cargill, Incorporated Hybrid yarns which include plant bast fiber and thermoplastic fiber, reinforcement fabrics made with such yarns and thermoformable composites made with such yarns and reinforcement fabrics
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EP3397797B1 (en) 2015-12-31 2023-08-30 UT-Battelle, LLC Method of producing carbon fibers from multipurpose commercial fibers

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US3803056A (en) * 1968-06-28 1974-04-09 Minnesota Mining & Mfg Heat resistant black fibers and fabrics derived from regenerated cellulose,containing certain heavy metals
US3997638A (en) * 1974-09-18 1976-12-14 Celanese Corporation Production of metal ion containing carbon fibers useful in electron shielding applications

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US5618624A (en) * 1995-02-22 1997-04-08 Hoechst Trevira Gmbh & Co. Kg Formable, heat-stabilizable textile pile material
WO2021252582A1 (en) * 2020-06-10 2021-12-16 Cytec Industries, Inc. A process for producing polymer fiber having at least one additive, and carbon fibers made therefrom

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