US3660140A - Treatment of carbon fibers - Google Patents
Treatment of carbon fibers Download PDFInfo
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- US3660140A US3660140A US47490A US3660140DA US3660140A US 3660140 A US3660140 A US 3660140A US 47490 A US47490 A US 47490A US 3660140D A US3660140D A US 3660140DA US 3660140 A US3660140 A US 3660140A
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- fibers
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- nitric acid
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- 229920000049 Carbon (fiber) Polymers 0.000 title claims abstract description 22
- 239000004917 carbon fiber Substances 0.000 title claims abstract description 22
- 239000000835 fiber Substances 0.000 claims abstract description 41
- 238000000034 method Methods 0.000 claims abstract description 20
- 239000011347 resin Substances 0.000 claims abstract description 19
- 229920005989 resin Polymers 0.000 claims abstract description 19
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000011159 matrix material Substances 0.000 claims abstract description 16
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 16
- 238000010992 reflux Methods 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 8
- 229920000647 polyepoxide Polymers 0.000 claims description 6
- 230000000593 degrading effect Effects 0.000 claims description 5
- 239000003822 epoxy resin Substances 0.000 claims description 5
- 230000009471 action Effects 0.000 claims description 3
- 239000000805 composite resin Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 229920001721 polyimide Polymers 0.000 claims description 2
- 239000009719 polyimide resin Substances 0.000 claims description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 5
- 239000002131 composite material Substances 0.000 description 11
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910001868 water Inorganic materials 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- RSWGJHLUYNHPMX-UHFFFAOYSA-N Abietic-Saeure Natural products C12CCC(C(C)C)=CC2=CCC2C1(C)CCCC2(C)C(O)=O RSWGJHLUYNHPMX-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- KHPCPRHQVVSZAH-HUOMCSJISA-N Rosin Natural products O(C/C=C/c1ccccc1)[C@H]1[C@H](O)[C@@H](O)[C@@H](O)[C@@H](CO)O1 KHPCPRHQVVSZAH-HUOMCSJISA-N 0.000 description 1
- 241000605112 Scapanulus oweni Species 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 229920006122 polyamide resin Polymers 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- KHPCPRHQVVSZAH-UHFFFAOYSA-N trans-cinnamyl beta-D-glucopyranoside Natural products OC1C(O)C(O)C(CO)OC1OCC=CC1=CC=CC=C1 KHPCPRHQVVSZAH-UHFFFAOYSA-N 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Images
Classifications
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F11/00—Chemical after-treatment of artificial filaments or the like during manufacture
- D01F11/10—Chemical after-treatment of artificial filaments or the like during manufacture of carbon
- D01F11/12—Chemical after-treatment of artificial filaments or the like during manufacture of carbon with inorganic substances ; Intercalation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
- C08J5/06—Reinforcing macromolecular compounds with loose or coherent fibrous material using pretreated fibrous materials
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
- Y10S264/19—Inorganic fiber
Definitions
- ABSTRACT A method of treating high modulus, high strength carbon fiber to improve its bonding characteristics in a resin matrix comprising immersing the fiber in concentrated nitric acid for 4-8 hours at refluxing temperature.
- carbon fiber is exposed toboiling nitric acid by immersion therein for an extended period of 4-8 hours.
- Carbon-resin composites fabricated with carbon fibers treated according to the present invention exhibited a high resistance to shear failure while maintaining high flexural strengths.
- FIG. 1 is a graph illustrating the effect of contact time on composite short beam shear strength
- FIG. 2 is a graph illustrating the relation between fiber volume and composite short beam shear strength
- FIG. 3 is a graph illustrating the relation between fiber volume and composite flexural strength
- FIG. 4 is a graph showing the correlation between specific surface area and short beam shear and transverse tensile strength.
- the technique of treating carbon fibers according to the present invention comprises immersing carbon fibers in boiling, concentrated nitric acid for a period of time sufficient to activate the fiber surface with little or no concomitant degradation in fiber properties.
- the process was performed on a batch basis by winding the yarn onto a spool and lowering it into an acid filled resin kettle which was provided with a reflux condenser and which served as the reaction vessel.
- the spool was comprised of two series of parallel rods concentrically arranged at two selected radial distances from a central rod, all rods being coated with Teflon and supported between two Teflon coated hubs.
- the carbon yam was wound about each series of parallel rods so that there existed a space between the yarn layers.
- the yarn was rinse cycled by rinsing in distilled water for three 15 minute periods, rinsing in a dilute solution of ammonium hydroxide for 10 minutes, rinsing in distilled water and then rinsing in acetone for two 15 minute periods.
- the yarn was air dried'in a hood and finally dried in an air-circulating oven at 100 C for 15 minutes, impregnated with resin by passage therethrough and wound onto a drum in tape form and processed into a com- 7 posite.
- lI-703 '1horncl-50 (52.5 1.45 moo 00. 1 22 7 lI-700 MG-50 (e1). 1. an 7, 500 121, u 28. 4 PI-703- HMG50 (55).. 1.53 7,450 116. 25.5 PIT-703 HMG-50 (55) uni-t outed. l. 52 5, 000 63. (l 24. 0 PIT-700 HMO-50 (57) untreated" 1. 54 4, 880 81. 8 21. 0 PI703.. Thornel-50 (50) untreated... l. 43 4-, 000 r 60. 0-
- FIG. I the effect of various contact times of carbon fiber with 70% HNO at 120 C on short beam shear strength of a composite having a 2,256-0820 epoxy resin matrix is shown.
- FIGS. 2 and 3 show the comparison between untreated fibers and those treated according to the present invention with respect to the effects of fiber volume on shear and flexural strength. In each case, the treated fibers display a significant increase'in strength regardless of volume fraction.
- a method for improving the bonding characteristics of high strength, high modulus carbon fibers with resin matrix material without significantly degrading the mechanical properties of the fibers which comprises, prior to impregnating the carbon fibers with said matrix material, subjecting said fibers to the action of concentrated nitric acid at refluxing temperature for a period of time sufficient to increase the specific surface area of the fibers to 3.4-7.3 m lg.
- a method for improving the bonding characteristics of high strength, high modulus carbon fibers with resin matrix material without significantly degrading the mechanical properties of the fibers which comprises, prior to impregnating said carbon fibers with said resin matrix material, exposing said fibers to the actionof concentrated nitric acid at refluxing temperature to cause an increase in the number of active sites the fiber is immersed at the fiber surface as measured by NaOH absorbed per unit area and continuing the exposure of the fiber to the acid at treated fiber. It thus appears that both the increase in surface 7 area and in surface reactivity contribute to the improvement I least until the number of active sites at the fiber surface ceases to increase.
- a method for the production of a carbon filament-resin composites having a high resistance to shear failure while maintaining high flexural strength comprising, exposing high modulus, high strength carbon filaments to concentrated nitric acid at refluxing temperature for atleast 4 hours, and impregnating said treated carbon filaments in a resin matrix.
Abstract
A method of treating high modulus, high strength carbon fiber to improve its bonding characteristics in a resin matrix comprising immersing the fiber in concentrated nitric acid for 4- 8 hours at refluxing temperature.
Description
United States Patent Scola et a1.
[54] TREATMENT OF CARBON FIBERS [72] Inventors: Daniel A. Scola, Glastonbury; Hilton A.
Roth, Cheshire, both of Conn.
United Aircraft Corporation, East Hartford, Conn.
[22] Filed: June 18,1970
[21] Appl.No.: 47,490
[73] Assignee:
[52] U.S.Cl. ..l17/47R,23/209.1,8/115.5,
8/140, 260/37, 264/D1G. 19, 117/161 P, 117/161 1 Z8 51 111:; C1. ..C0lb 31/07, 844d 1/092 [58] Field ofSearch. ...23/209.1;8/1l5.5,115.6,140; 117/47 R, 47 H, 106 R, 118,228; 264/DIG. 19;
[56] References Cited UNITED STATES PATENTS 2,615,932 10/1952 Marko et a1 ..117/47 R 2,669,598 2/1954 Marko et a1 ..1 17/47 R java [151 3,660,140 51 May 2,1972
3,529,934 9/1970 I Shindo ..23/209.l 3,294,572 12/1966 Piccione ...1 17/47 R 3,550,247 12/1970 Evanset a1 ..117/228 FOREIGN PATENTS OR APPLICATIONS 438,995 6/1964 Japan .23/209.1
OTHER PUBLICATIONS Derwent Japanese Textiles V01. 7, No. 15, pg. 6-tit1ed Carbon Fibres.
Chemical Abstraets V01. 64 p. 12862 c (1966).
Primary ExaminerWi11iam D. Martin Assistant Examiner-Michael Sofocleous Attorney-John D. Del Ponti [5 7] ABSTRACT A method of treating high modulus, high strength carbon fiber to improve its bonding characteristics in a resin matrix comprising immersing the fiber in concentrated nitric acid for 4-8 hours at refluxing temperature.
8 Claims, 4 Drawing Figures 1 TREATMENT or CARBON FIBERS BACKGROUND OF THE INVENTION resins such as thou suitable for use in applications of the aerospace industry, e.g. the epoxy or polyamide resins. The bond of such fibers to the resins has characteristically been poor typically yielding graphite fiber-resin matrix composites with low shear strengths; generally in the range of 3',500-4,500 psi for low fiber content composites (-45 vol 20 and below 3,500 psi for high fiber content composites (45-65 vol%).
While it has been suggested to surface treat carbon fibers in order to improve their shear strength by various methods,
such as for example, by oxidation, the resulting degradation of 2 5 other fiber properties, especially tensile strength, has been a problem.
SUMMARY OF THE INVENTION In accordance with this'invention carbon fiber is exposed toboiling nitric acid by immersion therein for an extended period of 4-8 hours. Carbon-resin composites fabricated with carbon fibers treated according to the present invention exhibited a high resistance to shear failure while maintaining high flexural strengths.
An understanding of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings, wherein:
FIG. 1 is a graph illustrating the effect of contact time on composite short beam shear strength;
FIG. 2 is a graph illustrating the relation between fiber volume and composite short beam shear strength;
FIG. 3 is a graph illustrating the relation between fiber volume and composite flexural strength; and
FIG. 4 is a graph showing the correlation between specific surface area and short beam shear and transverse tensile strength.
DESCRIPTION OF THE PREFERRED EMBODIMENT The technique of treating carbon fibers according to the present invention comprises immersing carbon fibers in boiling, concentrated nitric acid for a period of time sufficient to activate the fiber surface with little or no concomitant degradation in fiber properties.
The process was performed on a batch basis by winding the yarn onto a spool and lowering it into an acid filled resin kettle which was provided with a reflux condenser and which served as the reaction vessel. The spool was comprised of two series of parallel rods concentrically arranged at two selected radial distances from a central rod, all rods being coated with Teflon and supported between two Teflon coated hubs. The carbon yam was wound about each series of parallel rods so that there existed a space between the yarn layers. After the nitric acid treatment, the yarn was rinse cycled by rinsing in distilled water for three 15 minute periods, rinsing in a dilute solution of ammonium hydroxide for 10 minutes, rinsing in distilled water and then rinsing in acetone for two 15 minute periods. After the rinse-cycling the yarn was air dried'in a hood and finally dried in an air-circulating oven at 100 C for 15 minutes, impregnated with resin by passage therethrough and wound onto a drum in tape form and processed into a com- 7 posite.
During experimentation, commerciallyavailable Thornel I 50 yarmI'Iitco HMO-50 and Morganite I yarns were utilized with conditions and resulting properties as shown in'lables I and Il.
TABLE I.-GRAPI-IITE FIBER, EPOXY RESIN COMPOSITES Short beam Flexurnl properties shear (avg) strength, Fillet Composite p.s.i. Strength, Modulus, content. Density, Number Yarn (size) 'Ireatment 8/1) 5/1 10 p.s.i. 10 psi. 0 g. c. T-EO (H2O) None 3, 760 60.1 11. 3 83 1. 370 T- (H 0) (I 3, 780 (i3. 0 ii. (i 37 l. 33'. T-50 (H2O) 2, 080 03. l 16. 3 -18 I. 430 l50 (H O) 2, 600 70. 2 30. ii 0'. I. 475 T-50 (PVA) 3, 760 03. 8 13.0 30 1. 410 T-50 (PVA) 4, 250 74. 0 10.0 12 I. 390 'I50 (PVA) l, 720 80. 1 l7. 3 5-1 I. 416 'l50 (PVA) 7, 058 115. 3 .10. 7 53 1. 460 'I50 (H20) 7, 750 7!). 4 12. 0 31 1. 356 T450 (20) ii, 500 78. 2 ll. 5 37 1. 350 'I50 (IVA) 7, 7-10 107. 3 l7. 7 52 I. 405 'l50 (PVA H, 004 108.0 27. ii 52 I. 408 'l50 (I'VA) 7, 450 101. 5 31. 8 48 1. 450 I-50 (IVA) .do 7, 600 I01. 5 20. 5 54 1. 472 MG-50 (none) ][N()Il, 4 hrs. rellux. 8,240 105.0 21.7 41 1. 400 (Io 70%'IIN( 0111's. l'eIluX 8, 200 104. 8 32. ii 43. (i I. 430 do... 70% lINOs, 8 hrs. rellux. 8, 500 106. {I 24.1 40. 4 1. 375 .do. 70%I1N03, 10 hrs. reflux. 8, 300 110.0 25.1 45.1 1. 435 All). 70% HNOa, 8111's. reflux. 0 770 126. 7 28. 7 00. 4 I. 544 (Io tl0 7, 250 I35. 1 27.2 [53.5 1.523 ...(l0 0,420 124.8 02.0 1.508 .110 .(10 7,140 120,3 20,0 02.0 1.526 .1) (It) J, .130 7. li 213.5 53. 7 1. 11 (In 00.. H, lilill 128.1 15,0 51. 5 l. 480 J5 do NOllt. 1, M0, 70. -l .'-l.! 51.11 I. -12" .fti l\ lur .',nui'lu l (unlrrnlrtl) 7(l,',, "N01, 8 hrs. rvllux 7,515 00.3 l) l.-lli|i .7 Noll! 11,530 lJ. J 1.571)
10 l 0'14 ne o1.
TABLE II 1 lclylmidc/graphlte composites made with nitric acid treated fiber (8 hours) Q I Shear Flexural Flexual lolyimide I Density, strength strength modulus, rosin Fiber (v/o) g./co.- (p.s.i.) (K s. i.) b 10 p.s.l
lI-703 '1horncl-50 (52.5 1.45 moo 00. 1 22 7 lI-700 MG-50 (e1). 1. an 7, 500 121, u 28. 4 PI-703- HMG50 (55).. 1.53 7,450 116. 25.5 PIT-703 HMG-50 (55) uni-t outed. l. 52 5, 000 63. (l 24. 0 PIT-700 HMO-50 (57) untreated" 1. 54 4, 880 81. 8 21. 0 PI703.. Thornel-50 (50) untreated... l. 43 4-, 000 r 60. 0-
I Span-to-depth 1 6/1. b 4- polnt flex test.
Further tests, wherein the tensile strengths of treated and untreated yarns were made are shown in Table III.
TABLE ill 1 l'Ir-nsile strengths of untreated and treated graphite yarns] I Yarn strength p.s.i.)
UARL tested Before After I treattreat- Percent Yarn type Surface treatment merit ment change 'lhorncl-50 (PVA) 70% IINO 8 hrs., 181 188 +3. 9
lot #06238'1415. 120 C. '1hornol-50 (PVA) -.do 254 249 1.9
lot #09208T-3E. 'lhornel-50 (IVA) "do"... 179 213 +16 lot #06228T-3W. Illtqo l-IMG-so .(lo 219 200 8. 7
lot #C-07158-10A llitco HMO--50 'do v 239 232 3. 0
lot #C-12l08-1. llltco HMGtO' 70% HNO;, 8 hrs., 23%! .230 -3. 8
lot #C-12l08 1. 120 0., then- NH OHwash.
In FIG. I, the effect of various contact times of carbon fiber with 70% HNO at 120 C on short beam shear strength of a composite having a 2,256-0820 epoxy resin matrix is shown.-
lt can be seen, as a result of testing, that in order to achieve significant shear strength improvement, a minimum of 4 hours contact time is necessary. Further it can be seen that contact times of greater than 8 hours while not detrimental, produce no significant increasein shear strength.
FIGS. 2 and 3 show the comparison between untreated fibers and those treated according to the present invention with respect to the effects of fiber volume on shear and flexural strength. In each case, the treated fibers display a significant increase'in strength regardless of volume fraction.
It is believed that the great improvement of bonding characteristics of the carbon yarns treated according to the present nitric acid treatmentprocess are due primarily to the increase inspecific surface area and in the increase of surface reactivity caused by the treatment. Increasing the exposure of the fiber causes a steady increase in the surface area with a very gradual increase in'shear and transverse tensile strength. The results in Table lV'below, for example, indicate that there exists a definite correlation between the surface properties (specific surface area and the concentration of acid sites per unit area'of fiber based on sodium hydroxide adsorption) and the observed increases in shear strength. in the treatment, it has been found that the number of acid sites per unit area increases initially and then levels off and diminishes. in the particular experiment illustrated by Table IV,.it can be seen that while the concentration of acid sites/unit area falls off as the surface area increases to 24 mlg, it is still greater than the unlIitcO lulu-50 graphite yarn-=1mlunirlirrt-tionnl ll.\ltl 5r) epoxy resin composites 1! b H Compositeproperties Fiber properties 1 Short Specific NaOI-I NaOH beam surface adsorbed adsorbed shear I .Flber area, mole/g. mole/m. strength volume, Treatment m. /g. fiber fiber of p.s.i. percent None 0.87 0. 006 0. 074 4, 490 64 HNOG oxi tion (4 hr.) 3. 4 2. 04 0. 5, 600 64 HNO oxidation (8 hr.) 7. 3 3.0 0. 41 6, 090 5i) HN O oxidation (12 hr.) 10. 5 3. 60 t). 34 U, 500 (55 IINO3 oxidation (18 hr.) 24. 0 5. 9 0. 25 7,000 64 What is claimed is: I 4 1; A method for improving the bonding=characteristicsof high strength, high modulus carbon fiber with resin matrix material without significantly degrading the mechanical properties ofthe fiber'which comprises, prior to impregnating the carbonfibers with said resin matrix material, immersing said carbon fibers in concentrated nitric acid at refluxing temperature for at least 4 hours.
2. The method of claim 1 wherein from 4 through 8 hours.
3. The method of claim 2 wherein the acid is nitric acid.
4. A method for improving the bonding characteristics of high strength, high modulus carbon fibers with resin matrix material without significantly degrading the mechanical properties of the fibers which comprises, prior to impregnating the carbon fibers with said matrix material, subjecting said fibers to the action of concentrated nitric acid at refluxing temperature for a period of time sufficient to increase the specific surface area of the fibers to 3.4-7.3 m lg.
5. A method for improving the bonding characteristics of high strength, high modulus carbon fibers with resin matrix material without significantly degrading the mechanical properties of the fibers which comprises, prior to impregnating said carbon fibers with said resin matrix material, exposing said fibers to the actionof concentrated nitric acid at refluxing temperature to cause an increase in the number of active sites the fiber is immersed at the fiber surface as measured by NaOH absorbed per unit area and continuing the exposure of the fiber to the acid at treated fiber. It thus appears that both the increase in surface 7 area and in surface reactivity contribute to the improvement I least until the number of active sites at the fiber surface ceases to increase. I
. 6. A method for the production of a carbon filament-resin composites having a high resistance to shear failure while maintaining high flexural strength comprising, exposing high modulus, high strength carbon filaments to concentrated nitric acid at refluxing temperature for atleast 4 hours, and impregnating said treated carbon filaments in a resin matrix.
7. The method of claim 6 wherein said filaments are exposed for 4-8 hours.
8. The method of claim 6 wherein said resin is epoxy or polyimide resin.
Claims (7)
- 2. The method of claim 1 wherein the fiber is immersed from 4 through 8 hours.
- 3. The method of claim 2 wherein the acid is 70% nitric acid.
- 4. A method for improving the bonding characteristics of high strength, high modulus carbon fibers with resin matrix material without significantly degrading the mechanical properties of the fibers which comprises, prior to impregnating the carbon fibers with said matrix material, subjecting said fibers to the action of concentrated nitric acid at refluxing temperature for a period of time sufficient to increase the specific surface area of the fibers to 3.4-7.3 m2/g.
- 5. A method for improving the bonding characteristics of high strength, high modulus carbon fibers with resin matrix material without significantly degrading the mechanical properties of the fibers which comprises, prior to impregnating said carbon fibers with said resin matrix material, exposing said fibers to the action of concentrated nitric acid at refluxing temperature to cause an increase in the number of active sites at the fiber surface as measured by NaOH absorbed per unit area and continuing the exposure of the fiber to the acid at least until the number of active sites at the fiber surface ceases to increase.
- 6. A method for the production of a carbon filament-resin composites having a high resistance to shear failure while maintaining high flexural strength comprising, exposing high modulus, high strength carbon filaments to concentrated nitric acid at refluxing temperature for at least 4 hours, and impregnating said treated carbon filaments in a resin matrix.
- 7. The method of claim 6 wherein said filaments are exposed for 4-8 hours.
- 8. The method of claim 6 wherein said resin is epoxy or polyimide resin.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US4749070A | 1970-06-18 | 1970-06-18 |
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|---|---|
| US3660140A true US3660140A (en) | 1972-05-02 |
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| US47490A Expired - Lifetime US3660140A (en) | 1970-06-18 | 1970-06-18 | Treatment of carbon fibers |
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3791840A (en) * | 1970-10-21 | 1974-02-12 | Union Carbide Corp | Treatment of carbon fibers to improve shear strength in composites |
| US3894884A (en) * | 1972-08-28 | 1975-07-15 | Celanese Corp | Process for the enhancement of low modulus carbon fibers |
| US3914504A (en) * | 1973-10-01 | 1975-10-21 | Hercules Inc | Sized carbon fibers |
| US3919387A (en) * | 1972-12-26 | 1975-11-11 | Union Carbide Corp | Process for producing high mesophase content pitch fibers |
| US3931392A (en) * | 1974-01-10 | 1976-01-06 | The United States Of America As Represented By The Secretary Of The Navy | Enhancement of ultimate tensile strength of carbon fibers |
| US4009305A (en) * | 1972-12-22 | 1977-02-22 | Kureha Kagaku Kogyo Kabushiki Kaisha | Process for the surface treatment of carbon fibers |
| US4049613A (en) * | 1976-09-07 | 1977-09-20 | General Electric Company | Polyetherimide composites |
| US4336283A (en) * | 1974-05-21 | 1982-06-22 | The United States Of America As Represented By The Secretary Of The Navy | Plasticization of carbon fibers |
| US4571317A (en) * | 1976-02-25 | 1986-02-18 | United Technologies Corporation | Process for producing binderless carbon or graphite articles |
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| US2615932A (en) * | 1949-03-24 | 1952-10-28 | Olga Burkli | Process for manufacturing porous carbon electrodes |
| US3294572A (en) * | 1963-03-08 | 1966-12-27 | Pittsburgh Activated Carbon Co | Impregnation of carbon with silver |
| US3529934A (en) * | 1967-01-06 | 1970-09-22 | Nippon Carbon Co Ltd | Process for the preparation of carbon fibers |
| US3550247A (en) * | 1967-02-02 | 1970-12-29 | Courtaulds Ltd | Method for producing a metal composite |
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- 1970-06-18 US US47490A patent/US3660140A/en not_active Expired - Lifetime
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US2615932A (en) * | 1949-03-24 | 1952-10-28 | Olga Burkli | Process for manufacturing porous carbon electrodes |
| US2669598A (en) * | 1949-03-24 | 1954-02-16 | Olga Burkli | Process for manufacturing porous carbon electrodes |
| US3294572A (en) * | 1963-03-08 | 1966-12-27 | Pittsburgh Activated Carbon Co | Impregnation of carbon with silver |
| US3529934A (en) * | 1967-01-06 | 1970-09-22 | Nippon Carbon Co Ltd | Process for the preparation of carbon fibers |
| US3550247A (en) * | 1967-02-02 | 1970-12-29 | Courtaulds Ltd | Method for producing a metal composite |
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| Title |
|---|
| Chemical Abstracts Vol. 64 p. 12862 c (1966). * |
| Derwent Japanese Textiles Vol. 7, No. 15, pg. 6 titled Carbon Fibres. * |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3791840A (en) * | 1970-10-21 | 1974-02-12 | Union Carbide Corp | Treatment of carbon fibers to improve shear strength in composites |
| US3894884A (en) * | 1972-08-28 | 1975-07-15 | Celanese Corp | Process for the enhancement of low modulus carbon fibers |
| US4009305A (en) * | 1972-12-22 | 1977-02-22 | Kureha Kagaku Kogyo Kabushiki Kaisha | Process for the surface treatment of carbon fibers |
| US3919387A (en) * | 1972-12-26 | 1975-11-11 | Union Carbide Corp | Process for producing high mesophase content pitch fibers |
| US3914504A (en) * | 1973-10-01 | 1975-10-21 | Hercules Inc | Sized carbon fibers |
| US3931392A (en) * | 1974-01-10 | 1976-01-06 | The United States Of America As Represented By The Secretary Of The Navy | Enhancement of ultimate tensile strength of carbon fibers |
| US4336283A (en) * | 1974-05-21 | 1982-06-22 | The United States Of America As Represented By The Secretary Of The Navy | Plasticization of carbon fibers |
| US4571317A (en) * | 1976-02-25 | 1986-02-18 | United Technologies Corporation | Process for producing binderless carbon or graphite articles |
| US4049613A (en) * | 1976-09-07 | 1977-09-20 | General Electric Company | Polyetherimide composites |
| DE2735501A1 (en) * | 1976-09-07 | 1978-03-09 | Gen Electric | POLYAETHERIMIDE COMPOSITIONS |
| FR2363606A1 (en) * | 1976-09-07 | 1978-03-31 | Gen Electric | COMPOSITE MATERIALS BASED ON POLYETHERIMIDE AND CARBON FIBERS |
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