CA1255544A - Carbon fiber strength - Google Patents

Carbon fiber strength

Info

Publication number
CA1255544A
CA1255544A CA000540393A CA540393A CA1255544A CA 1255544 A CA1255544 A CA 1255544A CA 000540393 A CA000540393 A CA 000540393A CA 540393 A CA540393 A CA 540393A CA 1255544 A CA1255544 A CA 1255544A
Authority
CA
Canada
Prior art keywords
yarn
fibers
fiber
resin
precursor
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.)
Expired
Application number
CA000540393A
Other languages
French (fr)
Inventor
Manfred Katz
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.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
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 EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Application granted granted Critical
Publication of CA1255544A publication Critical patent/CA1255544A/en
Expired legal-status Critical Current

Links

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
    • D01F11/14Chemical after-treatment of artificial filaments or the like during manufacture of carbon with organic compounds, e.g. macromolecular compounds

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Reinforced Plastic Materials (AREA)
  • Ceramic Products (AREA)
  • Chemical Treatment Of Fibers During Manufacturing Processes (AREA)
  • Inorganic Fibers (AREA)

Abstract

TITLE
Improvement of Carbon Fiber Strength Abstract Carbon fibers from pitch are treated with carbonizable resin precursor and carbonized to give an improvement in carbon fiber strength.

Description

TITLE
Improvement of Carbon Fiber Strength Background of the Invention The production of carbon fiber from pitch is well known. See, for example, U.S. Patent N~s.
4,005,183 and 4,504,454. It is believed that the maximum tenacity which these fibers are capable of achieving is not attained due in part to defects in the fibers and/or at the fiber surface. The present invention seeks to enhance the fiber tenacity of such fibers.
Summary of the Invention This invention provides a method for increasing the tenacity of pitch-based carbon fiber yarn comprising impregnating a pitch-based carbonized or partially carbonized fiber yarn with a carbonizable resin precursor, polymerizing the precursor in situ to form the resin and subjecting the impregnated yarn to a temperature in excess of 1000C in an inert atmosphere to carbonize the resin.
; Detailed Description of the Invention ;
The carbon fiber yarn to be strengthened in accordance with the present invention is a pitch-based yarn. This yarn may be prepared by the general procedures described in UOS~ Patent No.
4,005,183. Eitber carbonized or partially carbonized yarn may be employed.
A ~olution of a carbonizable resin precursor ~ is applied to the yarn. The object is to impregnate the fibers of the yarn with a material which will polymerize or polymerize further to a resinous product which will remain in place and leave a carbon residue within the fiber upon carbonization. Thus, ~255544 the term "resin precursor" is intended to include unpolymerized or partially polymerized materials.
Polymerization or resinification is often facilitated by application of heat. The resin must be capable of being carbonized, the usual temperature of carbonization being above 1000Co Among suitable carbonizable resin precursors are partially polymerized phenolic condensation products, epoxy resins, furfural, furfuryl alcohol, partially polymerized furfuryl alcohol resin, urea condensation products, acrylic resins, vinyl resins, propylene glycol, etc. A sufficient amount of carbonizable resin precursor must be absorbed by the yarn to provide strengthening. Amounts yielding between about 0.1 and 10% of resin based on the weight of the yarn prior to impregnation have been found satisfactory. Preferably the weight gain is kept below 5~, particularly with partially carbonized fiber because such fibers are less able to absorb the resin precursors.
It is preferred that the resin precursor have a high coking factor, that is, a high percentage of carbon yield when subjected to carbonization.
Volatile impregnants which are entirely driven off in the heatinq step are clearly unsuitable.
The yarn is passed through a bath containin~
the carbonizable resin precursor. If the resin prerur~or is furfuryl alcohol, a partially polymerized furfuryl alcohol or combination thereof, it is desirable to incorporate a latent catalyst along with the precursor. These are commercially available and recommended for the purpose of catalyzing the polymerization of the resin precursor at elevated temperatures. One such catalyst is a complex of boron trifluoride and monoethylamine.

.
~:~S5S44L

Another catalyst is maleic anhydride. Use of a latent catalyst permits application of a low viscosity solution to the fiber with subsequent polymerization at the elevated temperatures. If the precursor were to polymerize significantly prior to application, the treating bath would be so viscous as to allow only a coating to be formed. Under such circumstances, the ~ibers of the yarn would stick to each other and become damaged or adversely affected for use in composites where penetration of matrix medium between the yarn fibers is of utmost importance. Suitable solvents are those which will readily evaporate without leaving any harmful residues. Acetone has been found useful for this purpose.
As mentioned above, the viscosity of the impregnation bath should be sufficiently low as to permit permeation of the resin precursor into the fibers of the yarn, i.e., to fill the voids, cracks and other defects of the fiber. If the bath is too viscous, the yarn itself, rather than the fibers thereof, will entrap such amounts of resin precursor I as to cause the fibers to ~tick tv each other. Such I fibers often break when attempts are made to separate them from each other. It will be understood that the resin content of the impregnating solution increases with age because partial polymerization is taking place. As this occurs, the viscosity of the bath increases and will influence the degree of fiber permeation.
Upon removal of the yarn from the bath, excess surface fluid is gently removed as by padding with an absorbent material to avoid damaging the yarn. Exposure of the yarn to air at room ~ 5~
temperature for extended periods allows solvents from the impregnating solution to evaporate and the resin precursor to partially cure. Alternatively, this may be achieved by slowly heating the yar~ from room temperature to final polymerization temperatures. In any event, the yarn must be heated to completely polymerize the impregnant. Conditions for such polymerization arle well known in the art.
In general, the yarn will !be heated to temperatures in the range of about 100 to 200C for periods of at least five minutes. Following this polymerization, the yarn is subjected to carbonization conditions, namely, treatment in an inert atmosphere, e.g., nitrogen, argon, etc., at temperatures of above 1000C until the resin has carbonized.

Testing Procedures Tenacity, elongation and modulus (T/E/M~ are measured according to ASTM D-3379-75.
The following examplcs are submitted to illustrate the invention and are not intended as l limiting. In each case, the pitch-based yarn was ! impregnated by passage through a bath containing the resin precursor.
1 The yarn conta;ned 496 filaments each having `~ 25 a diameter of about 10 microns. The carbonized yarn (at 1600C~ had an initial modulus of about 900 to ~000 grem~ per denier ~gpd).

Example 1 Carbon fiber yarn was impregnated with furfuryl alcohol containing 1~ latent catalyst (commercially available complex of boron trifluoride and monoethylamine ~BF3.MEA). The fibers were heated at 4C/min. to 150~C and held at 150C for 32 minutes ~2~;S544 : to polymerize the furfuryl alcohol. After polymerization the fibers were found to have gained 1.45% of their original weight. The fibers were then carbonized at 15B4C. An 11% improve~ent in tensile strength over the control fiber resulted tT/E/rl impregnated fiber: 14.6gpd/1.22%/1055gpd, T/~/M
control fiber: 13.2gpd/1.17~/988 gpd).

Example 2 Carbon fiber yarn was impregnated with the solution used in Example 1. The solution had been aged for 22 days. The furfuryl alcohol was polymerized under the same conditions as in Example 1. After polymerization, the fibers were found to have gained 8.7~ of their original weight. The fibers were then recarbonized at 1584C. A 22%
improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber:
16.1gpd/1.25~/997gpd, T/E/M control fiber:
13.2gpd~1.17~/988gpd).
Example 3 Carbon fiber yarn was impregnated using a 90/10% by wt. mixture of furfuryl alcohol and furfural ~odified furfuryl alcohol resin with 2~ of the latent catalyst of Example 1. The fibers were heated at 4C/min~ to 120~C and held at 120C for 32 minutes to polymerize the furfuryl alcohol/resin.
.fter polymerization, the fibers were found to have gained 3.2~ of their original weight. The fiber~
were then recarbonized at 1600C. A 29% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 14.2gpd/1.23%/10259pd, T/E/M c~ntrol fiber: ll.Ogpd/.95~/1081gpd).
Example 4 Carbon fiber yarn was impregnated using a 3l;æ~i;~5~4 90/10% by wt. mixture of furfuryl alcohol and furfural modified furfuryl alcohol resin with 2% of-the latent catalyst of Example 1. The fibers were heated at 4C/min to 120 and held at 120C for 32 minutes to polymerize the iEurfural modified resin.
After polymerization, the Eibers were found to have gained 6.1% of their original weight. The fibers - were then recarbonized at 1600C. A 24~ improvement in tensile strength over the control fiber resulted (T/E/M impregnated iber: 15.1gpd/1.18~/1148gpd, T/E/M control fiber: 12.2gpd/1.023%/lOg5gpd).
Example 5 Carbon fiber yarn was impregnated using a 10~ by wt. solution of furfural modified furfuryl alcohol resin dissolved in acetone. The fibers were then heated at 4C/min to 120C and held at 120C for 32 minutes. The resulting weight gain was 7.7~ of j their original weight. The fibers were recarbonized at 1600C. A 12~ improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 15.0gpd/1.41%/945, T/E/M control fiber:
13.4gpd/1.34~/868gpd).
Example 6 - Comparative Example i Carbon fiber yarn was impregnated using acetone containing 5% of the latent catalyst of Example 1. The fibers were then heated to 4C/min to j 120C. and held at 120C for 32 minutes. The i resultins weight gain was less than 1~. The fibers were then recarbonized at 1600C. No increase in strength resulted (T/E/M impregnated fiber:
13.7gpd/1.13%/1131gpd, T/E/M control fiber:
14.~gpd/1.07%/1272gpd). This example shows treatment with a non-resin forming medium did not result in strength improvement.

~25ss~4 Example 7 Carbon fiber yarn was impregnated using propylene glycol containing 5% of the latent catalyst of Example 1. The fibers were then heated at 4C/min to 200C and held at 200C for 32 minutes. A resin was formed from propylene glycol under these conditions. The resulting weight gain was less than 1%. The fibers were then recarbonized at 1600C. A
10% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 13.2gpd/
1.05%/1133gpd, T/E/M control fiber:
12.Ogpd/.947%/1141gpd).
Example 8 Partially carbonized yarn (heated to 1000C~
was impregnated with furfuryl alcohol containing 2%
of the latent catalyst of Example 1 which had been aged 72 hours. The fibers were heated at 4C/min to 120C and held at 120C for 32 minutes to polymerize the furfuryl alcohol. The resulting weight gain was less than 1%. The fibers were then oarbonized at 1599C. A 24.5~ improvement in tensile strength over the control fiber resulted. (T/E/M impregnated fiber: 14.5gpd/1.18~/1083gpd, T/E/~ control fiber:
l 11.6gpd/97%/1080gpd~.
! 25 Example 9 Carbon fiber was impresnated with furfural containing 2% of the catalyst of Example 1. The fibers were heated at 4C/min to 120CC and held at I20C for 32 minutes to polymerize the furfural.
~ 30 After polymerization, the fibers were found to have gained 0.1% of their original weiqht (weight gain from dipping was 3~ he fibers were then recarbonized at 1600C. A 14% improvement in tensile ~trength over the control fiber resulted (T/~/M

- ~255544 impregnated fiber: 13.8gpd/1.06%/1194gpd, T/E/M
control fiber: 12.2gpd/1.023%/1095gpd).
Exampl~ 10 Carbon fiber was impregnated using a 95/5%
by wt. mixture of furfuryl alcohol and furfural modified furfuryl alcohol resin with 5~ maleic anhydride added as a latent catalyst. The fibers were heated at 4C/min to 120C and held at 120C for 32 minutes to polymerize the furfuryl alcohol/resin.
After polymerization, the fibers were found to have gained 6.1~ of their ori~inal weight ~weight gain aftçr dipping was 160%). The fibers were then recarbonized at 1594C. A 20% improvement in tensile strength over the control fiber resulted ~T/E/M
impregnated fiber: 14.6gpd/1.17%/1155gpd, T/E/M
control fiber: 12.2gpd/1.02%/1087gpd).

Claims (5)

Claims:
1. A method for improving the tenacity of pitch-based carbon fiber comprising impregnating pitch-based carbon fiber yarn or partially carbonized yarn with a carbonizable resin precursor, polymerizing the precursor in situ to form the resin and subjecting the impregnated yarn to a temperature in excess of 1000°C in an inert atmosphere to carbonize the resin.
2. The method of claim 1 wherein the precursor is furfuryl alcohol.
3. The method of claim 1 wherein the precursor is partially polymerized furfuryl alcohol.
4. The method of claim 1 wherein a sufficient amount of precursor has been absorbed by the yarn to provide a weight gain after polymerization of between 0.1% and 10% based on the weight of the yarn prior to impregnation.
5. The method of claim 1 wherein a latent catalyst is employed to catalyze polymerization of the precursor.
CA000540393A 1986-06-25 1987-06-23 Carbon fiber strength Expired CA1255544A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US87821786A 1986-06-25 1986-06-25
US878,217 1986-06-25

Publications (1)

Publication Number Publication Date
CA1255544A true CA1255544A (en) 1989-06-13

Family

ID=25371603

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000540393A Expired CA1255544A (en) 1986-06-25 1987-06-23 Carbon fiber strength

Country Status (4)

Country Link
EP (1) EP0251596A1 (en)
JP (1) JPS636115A (en)
AU (1) AU7458587A (en)
CA (1) CA1255544A (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02221159A (en) * 1989-02-23 1990-09-04 Mitsubishi Pencil Co Ltd Production of carbon fiber reinforced carbon composite material
JPH0416555A (en) * 1990-05-11 1992-01-21 Nippon Oil Co Ltd Production of carbon-carbon composite material
JPH0416556A (en) * 1990-05-11 1992-01-21 Nippon Oil Co Ltd Production of carbon-carbon composite material
GB9202486D0 (en) * 1992-02-06 1992-03-25 Dunlop Ltd Carbon-carbon composite material
JP5483701B2 (en) 2010-02-08 2014-05-07 日曹金属化学株式会社 Zinc based alloy
US9550701B2 (en) 2013-07-25 2017-01-24 Honeywell International Inc. Carbon-carbon composites including isotropic carbon encapsulating layer and methods of forming the same

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3908061A (en) * 1972-03-10 1975-09-23 Dow Chemical Co Composite materials comprising resin matrix and carbon fibers
US4115528A (en) * 1977-08-15 1978-09-19 United Technologies Corporation Method for fabricating a carbon electrode substrate

Also Published As

Publication number Publication date
JPS636115A (en) 1988-01-12
AU7458587A (en) 1988-01-07
EP0251596A1 (en) 1988-01-07

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