CA2041560A1

CA2041560A1 - Adhesion between carbon fibers and thermoplastic matrix materials in carbon fiber composites

Info

Publication number: CA2041560A1
Application number: CA 2041560
Authority: CA
Inventors: Julia A. King; Daniel A. Buttry
Original assignee: Hoechst Celanese Corp
Current assignee: CNA Holdings LLC
Priority date: 1990-05-08
Filing date: 1991-04-30
Publication date: 1991-11-09
Also published as: KR910020220A; US5106680A; EP0456465A1; JPH04228677A

Abstract

ADHESION BETWEEN CARBON FIBERS
AND THERMOPLASTIC MATRIX MATERIAL
IN CARBON FIBER COMPOSITES
ABSTRACT OF THE INVENTION

Adhesion between carbon fibers and thermoplastic matrix materials, used in carbon fiber composite materials, is promoted by the use of a bridging agent. The composite material includes: a plurality of carbon fibers; a thermoplastic matrix material intermingled among the plurality of carbon fibers; and a bridging agent adhering the plurality of carbon fibers to the thermoplastic matrix material. The bridging agent includes compounds having multifunctional groups that are capable of chemically bonding with a functional group of the carbon fiber and a functional group of the thermoplastic matrix material; but it excludes multifunctional amine compounds having metal-oxygen bonds.

Description

5~
ADHESION BETWE~N C~RBON FIBERS
AND THERMOPLASTIC MATRIX MATERIALS
IN CARBON FIBER COMPOSITES

Field Of The Invention The instant invention is directed towards promoting adhesion between the carbon fibers and the thermoplastic matrix materials used in carbon fiber composite materials.

Backqround Of The Invention Composite materials used in high performance applications are typically be.ing prepared from polyacrylonitrile (PAN) based carbon ~ibers and a thermoset matrix material, such as an epoxy. Although such materials exhibit excellent strength and stiffness properties, they are generally limited to moderate operational temperatures (e.g., less than 177C) and are relatively brittle (i.e., low impact strength). These limitations are mostly due to the thermoset matrix or resin system. ~onsequently, much interest has been generated in the development of better matrix materials. Much or this interest has been directed toward thermoplastic matrix or resin systems.

~ any th~rmoplastic resins have significantly higher use temperatures and are tougher (i.e., higher impact strength) than the thermosets (i.e., epoxies) currently used. In addition, most thermoplastic resins are solvent resistant, and have thermal and environmental stability suitable for high performance applications, such as aircraft structures. Also, since thermoplastics consist of L56~
mole~les that are physically bonded together as opposed to thermosets which consist of chemically bonded molecules, thermoplastics can be reformed. This facilitates repairs to composite structures.
Consequently, the use of thermoplastic matrix materials in high performance applications, such as advanced aerospace systems, is anticipated.

One common problem with thermoplastic matrices is that the adhesion of these materials to carbon fibers is typically weaker than that of thermosetting materials. Good fiber-matrix adhesion is necessary in order to produce composites with desirable mechanical properties. If the fiber-matrix adhesion is poor, the composite will fail at the fiber-matrix interface, thus reducing the shear strength and other mechanical properties of the composite. Standard s~rface treatments of carbon fibers, which are designed for thermoset resins, generally result in little improvement in carbon fiber-thermoplastic matrix adhesion. since no chemical reaction occurs during the fabrication of thermoplastic matrix composites, the likelihood of forming covalent chemical bonds between the fiber and the thermoplastic matrix material is greatly diminished. The formation of chemical bonds at the interface has been shown to be a significant factor in improving the interfacial bond strength in many composite systems.

Very little information has been published regarding the adhesion of carbon fibers to t~ermoplastic matrix materlals. Thermoplastic matrices are, in general, new to the composites industry. ~n fact, 2~

onl~ two major groups of researchers have published results of studies concerning the adhesion of carbon fibers to thermoplastic matrices.
T.A. DeVilbiss and J.P. Wrightman, "Surface Characterization In Composite And Titanium Bonding: Carbon Fiber Surface Treatments For Improved Adhesion To Thermoplastic Polymers," Final Report to NASA-Langley Research Center, Grant No. NAG-1-343, September 1987., and W.D. Bascom, "Interfacial Adhesion Of Carbon Fibers," NASA
Contractor Report 178306, Contract NASl-17918, August 1987.

DeVilbiss and Wrightman studied the adhesion of PAN-based carbon fibers to polysulfone, polycarbonate, and polyetherimide thermoplastic matrices. They used Hercules AU~ and AS4, Dexter Hysol XAU and XAS, and Union Carbide T-300U and T-300S carbon fibers in their studies.
The letter "U" in these fiber designations indicates that the fibers were not commercially surface treated. The letter "S" designated that they were commercially surface treated. DeVilbiss and Wrightman determined the shear strength for both the commercially treated and untreated carbon fibers. In addition, they conducted one anodization treatment in 0.5 M sulfuric acid and one in 0.5 M sodium hydroxide on each type of untreated carbon fiber. Both treatments were conducted at 6 volts for 15 minutes.

\

For all these composite systems, they reported shear strengths in the range of 1~ to 27 MPa (2.0 to 3 9 ksi), which is less than half that of most carbon/epoxy composites. In all three matrix materials, the adhesion was the best for either the sulfuric acid or sodium hyd~xide anodized AU4 carbon fiber. The failure location (i.e., the matrix, the interface, or the fiber) was not given.

Bascom et al studied the adhesion of three different PAN-based carbon fibers, Hercules AS4 and ASl, and Grafil XAS, to several different thermoplastic matrices using the embedded single fiber test.
Also see: W.D. Bascom, K.J. Yon, R.M. Jensen, and L. Cordner, "The Adhesion Of Carbon Fibers To Thermoset And Thermoplastic Polymers,"
Conference: Chemistry and Properties of High Performance Composites:
Designed Especially for Chemists, West Point, New York, October 198~;
and W. D. ~ascom, "Su~ace A~d Intar~ci~l Prop~rtl~ 0~ C~rbon Fibers," NASA-CR-182890, Progress Report NAG-1-706, October 1, 1987 -April 15, 1988. Bascom et al determined that the XAS Eibers demonstrated better adhesion to these thermoplastics than the AS
fibers because of the lower surface basicity of the XAS fibers relative to the AS4 fibers. The AS fibers are more graphitic, and thus, they have a more basic fiber surface than XAS fibers. Water is strongly adsorbed onto these highly basic, graphitic regions present the AS fibers. Apparently, this adsorbed water inhibits the adsorption of thermoplastic matrices. For a polar matrix system, such as epoxy, this situation is not a problem, since the water-is easily displaced by the polar epoxy polymer.

A very limited amount of information has been published concerning the adhesion of carbon fibers to crystalline thermoplastics. Polyetheretherketone (PEEK) is a relatively new, 2~ 6~

part `lly amorphous/partially crystalline (semicrystalline) engineering thermoplastic, whose service temperature is above 200C.
PEEK is produced by ICI Corporation, and th~ majority of the information concerning the fiber-matrix adhesion of PEEK composites is proprietary. However, the open literature does contain a few reports concerning the adhesion of PEEK to various fibers. S. Hamdan and J.R.G. Evans, "The Surface Treatment And Adhesion Bonding Of Polyetheretherketone. Part I. Adhesive Joint Strength," Journal of Adhesion science and Technoloqy, Vol. 1, No. 4 (1987) pp. 281-289., and J.A. Peacock, B. Fife, E. Nield, and R.A. Crick, "Examination Of The Morphology Of Aromatic Polymer Composite (APC-2) Using An Etching Technique," comPosite Interfaces, H. Ishida and ~.L. Koenig, Eds., Elsevier Publishing Co., Inc. (1986) pp. 299-305.

Hamdan and Evans reported tha~ the fiber-matrix adhesion of 20 percent fiber volume glass/PEEK composites was improved by chromate etching the PEEK for 30 minutes at 50C and by plasma etching the PEEK
in oxygen for 15 minutes. Their conclusions were based on lap shear strength tests. Peacock et al used an etching tecllnique t~ observe the matrix morphology in Hercules AS4/PE~K composites. They determined that their AS4/PEEK unidirectional composites displayed excellent short beam shear strength (viz., 105 MPa or 15.2 ksi) due to the fact that nucleation from the AS4 fibers dominated the morphology.
Discrete spherulitic growth occurred at the AS4 surface before initiation started in the matrix. Thus, a high degree of intimacy between AS4 and P~EK was achieved. This nucleation that takes place 2~5r~i~
on tne AS4 surface is believed to be stress induced. Crystal growth was oriented perpendicular to the AS4 surface.

Generally, after a carbon fiber is commercially surface treated, a matrix compatible sizing (e.g., a thin layer of epoxy resin) is applied to the fiber surface. The sizing protects the fibers from being damaged when handled, and also helps preserve the surface functional groups. Bascom reported that a 0.1 weight percent application of a phenoxy sizing (PKHC, Union Carbide) on the AS4 sur~ace slightly improved the adhesion of AS~/polycarbonate composites. The embedded single fiber test was used to quantify the ~iber-matrix adhesion. No explanation was offered for the observed adhesion improvement.

Recently, titanium-based and zirconium-based coupling agents for carbon fiber/thermoplastic matrices have been developed. S. Monte and G. sugarman, Ken~React Reference Manual, Kenrich Petrochemicals, . . .
Bayonne, New Jersey (1987). For example, organotitanate coupling agents have been shown to improve the flexural modulus of carbon fibe~/polyetheretherketone (PEEK) and carbon fiber/acrylonitrile -butadiene-styrene (ABS) composites. Ibid. PEEK and ABS are thermoplastic matrix materials. This adhesion improvement, as taught by Monte and Sugarman, is due ~o the direct reaction of the hydroxyl groups on the carbon fiber sur~ace with the metal (Ti or Zr)-oxygen bond on the. coupling agent. The chemical formulas for several specific titanium-based and zirconium-based coupling agents are as follows:

6~
o o Il ll RO ~ Ti (O - P - O - P (OC8H17)2)3 O~I

RO - Ti (O - C2H~ - NH - C2H4 - NH2)3 ( 6 4 2)3 Accordingly, there is a continuing and ongoing need to explore the adhesion between carbon fibers and thermoplastic matrix materials.

Summary Of The Invention The instant invention is directed to a carbon fiber composite material comprising: a plurality of carbon fibers; a thermoplastic matrix material intermingled among said plurality of carbon fibers;
and a bridging agent adhering said plurality of carbon fibers to said thermoplastic matrix. The bridging agent includes compounds having multifunctional groups that are capable of chemically bonding with a 'nctional group of the carbon fiber and a functional group of the thermoplastic matrix material, for example, multifunctional amine compounds and azo compounds, but it excludes those multifunctional amine compounds that include metal~oxygen bonds.

Alternatively, the instant invention is directed to a method for adhering carbon fibers to a thermoplastic matrix material in a carbon 6~
fib composite material comprising the step of: adding a bridging agent to the thermoplastic matrix material and the carbon fibers prior to the consolidation of the carbon fiber composite material.

Description Of The Drawinqs For the purpose of illustrating the invention, there is shown in the drawings a procPssing technique and form which is presently prererred; it being understood, however, that this invention is not limited to the precise arrangement and instrumentality shown.

Figure 1 is a pho-tomicrogr~ph o~ the sheared interface of a carbon fiber composite material that was not treated with the bridging agent.

Figure 2 is a photomicrograph of the sheared interface of a carbon fiber composite material that was treated with the bridging agent.

Figure 3 is a schematic illustration of a "single bath"
continuous process for treating commingled carbon fibers and fibers of the thermoplastic matri~ material with the bridging agent.

Figure 4 is a schematic illustration of a "three bath" continuous process for treating commingled carbon fibers and fibers of the thermoplastic matrix material with the bridging agent.

15~
Detailed Description Of The Invention Adhesion between carbon fibers and the thermoplastic matrix materials used in carbon fiber composite materials, according to the instant invention, shall be discussed hereinafter.

The following terms shall have the following meaning:

"Carbon fiber" - a fiber of carbonous material which is suitable for use in composite material applications.

"Thexmoplastic matrix material" - a high polymer that softens n exposed to heat and returns to its original condition when cooled. Exemplary thermoplastic matrix materials include, but are not limited to, liquid crystalline polymers (LCP), polyetheretherketone tPEEK), polyphenylene sulfide (PPS), polyethylene sulfone (PES), polycarbonate, polyetherimide, ABS. The thermoplastic matrix material may be in any form, for example, a fiber or a powder. Thermoplastic matrix material does not include "thermoset matrix material".
'hermoset matrix materials are high polymers that solidify or "set"
irreversibly when heated. An exemplary thermoset matrix material is epoxy.

"Bridging agent" - a material added to or coated on the carbon fibers and/or the thermoplastic matrix materials before consolidation of the carbon fiber composite material that promotes adhesion bet~een the carbon fibers and the thermoplastic matrix material after 5~n con ,lidatlon. Exemplary bridging agents include, but are not limited to, those compounds having multifunctional groups that are capable of chemically bonding with a functional group of the carbon fiber and a functional group of the thermoplastic matrix material, for example, multifunctional amine compounds and azo compounds, but exclude those multifunctional amines that include metal-oxygen bonds. Further definition of specific bridging agents shall be found hereinafter.

It is theorized (however the invPntion is not limited to this theory) that adhesion between the carbon fibers and the thermoplastic matrix materials can be promoted by "bridging" together the carbon fiber and the matrix material. This "bridging" occurs when one of the functional groups on the bridging agent reacts with and bonds to a functional group on the carbon fiber and on the matrix material. In other words, the brid~ing agent forms a link, anchored by chemical bonds, between the carbon fiber and thermoplastic matrix material.
Therefore, it is believed that adhesion occurs as a result of covalent bonding of the bridglng agent between the carbon fibers and the _hermoplastic matrix material.

For example, compare Figures 1 and 2. Figure 1 is a scanning electron microscope (SEM) photomicrograph (x780) of a sheared interface of an untreated (i.e., no bridging agent) carbon fiber/LCP
composite. Figure 2 is a SEM photomicrograph (x780) of a sheared interface of a treated (i.e.~ with bridging agent, ~-aminophenyl sulfone) carbon fiber/LCP composite. Note, in the former, the lack of 2~5~
fib~_ls interconnecting the fibers, whereas, in the latter, a larger number of fibrils interconnect the fibers. The fibrils comprise the LCP matrix material. Thus, the use of a bridging agent promotes the carbon fiber/LCP adhesion because, after shearing, more of the thermoplastic matrix material adheres to the fiber when the composite is treated than when the composite is not treated.

Multifunctional amine compounds belong in the class of compounds called bridging agents. Multifunctional amine compounds include those compounds having two or more amine groups. It is believecl that one amine group reacts with a carboxyl.ic acid group present on the carbon fiber surface to form amide bonds, Whereas, another amine reacts with an ester group of the LC~ to form an amide bond, or it reacts with a sulfone group of the PES, or it reacts with the ketone group of PE~K.
The following multifunctional amines are representative of this portion of the bridging agents: 1,4-diaminopiperazine hydrochloride;
diethylenetriamine; 1,12-diaminododecane; 1,3-diaminopropane;
1,8-diaminonaphthalene; urea; 1,4-phenylenediamine; and 4-aminophenyl sulfone [H2N(C6H4)s2(c6H4) 2]

Azo compounds having a second reactive group also belong in the class of compou~ds called bridging agents. The azo group upon th~rmal decomposition (such-as would arise in the consolidation of composite materials) results in the formation of a carbon radical that can react with any C-C bonds on the carbon fiber surface under the condition (for example temperatures greater than 300C) found in the formation of odrbon fiber composite materials. The second reactive group could include those groups discussed above with regard to the multi~unctional amine compounds. The ~ollowing azo compounds are representative of this portion of the coupling agents:
aminoazoben~ene; 4-4' azobis (4~cyanovaleric acid); and Fast Garnet 6 4) (C6H3)N2 p-CH3-mHS04 ]. Please note that in the foregoing compounds, the molecules contained at least one azo moiety and another reactive group, which would be reactive with a group on the thermoplastic matrix material.

Referring to Figures 3 and 4, two methods b~ which the bridging agent may be appliecl to the tow consisting of the intermingled carbon fibers and thermoplastic matrix material are illustrated. By either method, the tow is drawn through a bath of the solvated bridging agent and then subjected to heat so that any excess solvent is vaporized.

In Figure 3, a "single bath~' method 10 is illustrated. The tow 12 i5 unwound from a supply spool 14. Next, tow 12 is passed through a bridging agent bath 16. The bridging agent-wetted tow is then dried, by tAe use of an air blower 18 and tube furnace 20.
~hereafter, the tow is taken up on a rewind spool 22. --In Figure 4, a "three bath" method 30 is illustrated. The tow 32 is unwound from a supply spool 34. Then, the tow is passed through an acid bath 36. Acid bath 3G ensures that the carboxylic acid yroups present on the surface of the carbon fiber are protonated. The acid ~:~4~5~

batl. 36 may comprise a 0.1 M HCl solution. The protonated tow is then drawn through an alcohol bath 38. Alcohol bath 38 ensures the removal of residual acid from the tow and thereby preven~s contamination of the bridging agent bath. The alcohol bath may comprise 2-propanol.
The washed protonated tow is then drawn through a bridging agent bath 40. Thereafter, the tow is dried, via blower 42 and furnace 44, and taken up on rewind spool 45, as with the single bath method.

The short beam shear (SBS) test, ASTM Standard D2344-76, was used to determine the ultimate shear strength are ~13, using Equation 1.
r13 = 0.75 Pmax/A Eqn. (1) where:
Pmax - maximum value of applied force, and A = cross-sectional area of the test specimen.
Note that the short beam shear test measures the interlaminar strength. The SBS ratio, discussed herein, is SBS strength of the treated composite divided by the sBS s~rength of the untreated composite.

The dimensions of the typical SBS test specimen were 15.2 mm (0.60"~ in length, 12.7 mm (0.50")..in width, and 2.0 mm (0.08") in thickness. As recommended by the ASTM procedure for carbon fiber composites, a 5:1 span/depth (thickness) ratio was used. Accordingly, a span of 10.2 mm (0.40"~ was used. For these tests, an Instron Model 1125 electromechanical testing machine was used, along with a 5kN load cell. The crosshead speed was held constant at 1 mm/min. A strip chart recorder was used to monitor the force applied to the test specimen.

2C 14:~5~
rhe composite panels were fabricated under the following conditions: pressure ~ 200 psi; temperature - 300C; and time at temperature and pressure - 20 minutes.

Examples In Examples 1-23, a tow band containing carbon fibers intermingled with Hoechst Celanese's VECTR~N~ A900 grade fibers ta random copolymer consisting of about 73 mole percent p-hydroxy benzoic -cid and 27 mole percent 6-hydroxy-2-naphthoic acid) was treated with -~rious multifunctional amine compounds. The tow band comprised about 60~ 1 percent by volume carbon ~iber. The carbon fiber ~s a PAN-based carbon fibers, ~or example, Hercules' surface treated 3k AS~
(3,000 fibers/tow); Grafil's surface treated 6k XAS (6,000 fibers/tow); or Grafil's 6X XAU (6,000 fibers/tow).

Referring to Table 1, the tow band was treated in either a "one bath" (Figure 3) or "three bath~ (Figure 4) process. (If the "one bath" process was used, then no residence time is given for the first _wo baths.) Treatments were conducted at room temperat~re (approximately 23C). All reagents used were commercially available from Aldrich Chemical Company Inc. of Milwaukee, Wisconsin.

The hot air blower and furnace (a Lindberg tube furnace, 0.61 meters iII length) was set so that all excess solvent is vaporized from the fiber. Weight percent refers to the weight of the reagent used per total weight of the tow band (total weight of the tow band was ap~ Jximately 41.3 grams). The tow band length was about 143 meters (470 feet).

The composition o~ each bath is given. The residence time that the tow band resided in the bath is given. The average treated SBS
strength is given. The SBS ratio is given.

The reagents listed in Table 1 are as follows: APS -4-aminophenyl sulfone; DAPP HCL - 1,4-diaminopiperazine hydrochloride;
DETA - diethylenetriamine; DADD - 1,12-diaminododecane; DAP -1,3-diaminopropane; DAN ~ diaminonaphthalene; Urea; PDA - 1,4 phenylenediamine.

Ueight of Vol~me of 0.1 M HCL 2~Propanol Amine Average Treated Troatmcnt t~eight Aminc Used Solvent Bath Bath Bath SBS Strength SBS

No. NDme Percent (g) Used ~ml) Solvent tseconds) ~seconds) (seconds) tMPa) (Ksi) Ratio 1 APS-11.0 0.417 1000 Ethanol - 15.0 50 7.3 1.07 APS lA 1.00.416 1000 Ethanol1Z.5 17 5 15 0 58 B 4 1.22 APS lAR 1~00.416 1000 Ethanol12.5 17.5 15.0 53 7.7 1.13 APS lOA 10.04.183 3200 Ethanol11.2 17.5 25.0 51 7.4 1.08 DAPP HCl 1 1.00.408 1300 Uater 10.0 49 7.2 1.05 6 DAPP HC1 10 1.0 4.187 1300 Uater 10.0 53 7.7 1.12 7 DETA-l1.0 0.427 13002 Propanol 10.0 51 7.4 1.08 8 DETA 10 10.04.112 13002 Propanol 10.0 52 7.6 1.11 9 DETA-lOOA 100.0 41.300 8002 Propanol 20.0 17.5 13.7 48 6.9 1.01 10 DADO l 1.00.413 1300MeShanol 10.0 54 7.8 1.06 11 OADD-lA 1.00.414 1300Methanol20.0 17.5 15.0 45 6.6 0.96 12 DAOD lU 1.00.417 1300 Uater20.0 16.2 15.0 48 6.9 1.01 13 DADO 5 5.02.076 1300Methanol 10.0 54 7.8 1.09 14 DADD 10 10 04 129 1300Methanol - - 10.0 55 7.9 1.08 15 DAP-l1 0 0.517 1300Methanol 10.0 51 7.3 1.07 16 DAP-1010.0 5.040 1300Methanol 10.0 51 7.4 1.08 17 DAN-11.0 0.422 1300 Acetone 10.0 50 7.2 1.05 18 DAN-1010.0 4.205 1300 Acetone 10.0 50 7.2 1.05 t9 Urea-11.0 0.421 1300Methanol 10.0 50 7.2 1.05 20 Urea-10 10.04.131 1300Methanol - 10.0 50 7.3 1.06 21 PDA l1.0 0.413 1300Methanol 10.0 49 7.0 1.03 22 PDA-1010.0 4.135 1300Methanol - 10.0 45 6.5 0.95 23 PDA-2020.0 8.262 1300Methanol - 10.0 46 6.6 0.97 The numbers following the reagents correspond to the weight percent of the reagent. The letters (A, R, W) following the reagents indicate either acid bath (A), repeat of ireatment (R), or distilled water was used as the solvent (W).

In Examples 24-31, a tow band containing carbon fiber intermingled with LCP (as discussed in the foregoing Example Nos.
1-23) were treated with various azo compounds. In these examples, treatment was conducted in a "one bath" (Figure 3) process. The residence time of tow band in the treatment bath was about 10 seconds.
All other aspects are the same as set forth in Examples 1-23.

Referring to Table 2, the reagents listed are as follows: AAB-4 aminoazobenzene; ABCV~-azobis (4-cyanovaleric acid); GBC-Fast Garnet GBC salt.

Ueight of Volume of Average Trea~ed Treatment~eightReagent Used Solvent S9S Strength SBS

No. NamePercent (g) Used tml)Solvent (MPa) (Ksi) Ratio 24 M B-l 1.0 0,419 1300 Methanol 51 7.5 1.06 25 MB-10 10.0 4.160 1300 Me~hanol 50 7.2 1.05 26 MS-20 20.0 8.278 130D Methanol 50 7.2 1.04 27 AaCVA l 1.0 0.413 1350 Uater49 7.1 1.00 28 ABCVA-10 10.0 4.130 1300Methanol 51 7.4 1.05 29 ABCVA-40 40.0 16.520 1300Methanol 37 5.4 0.76 30 GBC l 1.0 0.412 1300 Uater 50 7.2 1.05 31 G3C-1010.0 4.133 1300 ~ater 50 7.3 1.06 s~
In Comparative Examples 32-48, a tow band containing carbon fiber intermingled with LCP (as discussed in the foregoing Example Nos.
1-23) was treated with various compounds, outlined below, for comparison. In these examples, treatment was conducted in a "one bath" (Figure 3) process or a "three bath" (Figure 4) process. All other aspects are the same as set forth in Examples 1-23.

Referring to Table 3, the reagents listed are as follows:
O O
Il 11 LICA 38 ~ RO - Ti ( ~ P - o - P (OC8H17)2) OH
LICA 44 - RO - Ti (O - C2H4 - NH - C2H4 - NH2)3, LZ97 - RO - Zr (OC6H4 - NH2)3' (LICA38, LICA44, and LZ97 are available from Kenrich Petrochemicals, Inc., Bayonne, New Jersey), Nafion - a perfluorinated ion exchange powder, prepared from Nafion 11~ perfluorinated membrane, in a mixture of lower aliphatic alcohols and water (Nafion is available from Pont, Wilmington, Delaware), PS - phenylsulfone, EA - ethylamine.

5~i~

Ueight of Volune of 0.1 M HCL 2-Propanol Coupling Avernge Treated Treatment Ueight Reagent Solvent Bath Bath Agent 9ath SBS Strength SBS
No. Name Perccnt Used (9~ Used ~ml) Solvent ~seconds~ ~seconds) ~seconds~ ~MPa) (Ksi~ Ratio 32 LICA 38-15 15.06.200 SS002-Propanol ~ 11.4 S0 7.3 0.97 33 LICA 44 0.5A O.S 0.232 SS002-Propnnol13.8 15.0 15.0 56 8.1 1.0934 LICA 44 1A l.0 0.418 SS002-Propanol15.0 17.5 17.5 56 8.1 1.08 35 LICA 44-12 12.0S.000 SS002-Propanol - 11.4 51 7.3 0.98 36 LZ 97-O.SA O.S 0.217 750 DMF 12.5 17.5 11.2 52 7.5 1.05 37 LZ 97-1A 1.0 0.418 700 DMF 11.2 17.5 13.7 52 7.5 1.05 38 LZ 97-2A 2.0 0.821 620 DMF 12.5 17.5 13.7 52 7.5 1.06 39 LZ 97-SA 5.0 2.065 540 DMF 11.2 17.5 13.7 54 7.9 1.14 40 LZ-97 10A 10.04.130 600 DMF 11.2 17.5 13.7 57 8.3 1.20 41 LZ 97-10 10.04.172 600 DMF - 9.6 56 8.1 1.18 42 LZ 97-17 17.07~000 1200Kenplast PG - 9.6 56 8.1 1.08 43 Nafion14.0 4.370487 Uater - - 10.0 43 6.2 0.91 44 PS-1 1.0 0.4191300 Ben2ene - 10.0 47 6.8 1.00 45 PS-10 10.0 4.1301300 ~en2ene 10.0 S0 7.2 1.05 46 NH3Gaseous ammonia at 41 PSIG, 62 C for 3 hours N/A 6.29 0.92'7 EA-11.0 Untcr lO.0 NtA 7.11 1.02 48 EA-lOlO.0 Unter 10.0 NtA 7.09 1 .oa The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims

1. A carbon fiber composite material comprising:
a plurality of carbon fibers;
a thermoplastic matrix material intermingled among said plurality of carbon fibers; and a bridging agent adhering said plurality of carbon fibers to said thermoplastic matrix material.

2. The carbon fiber composite material according to claim 1, wherein said bridging agent comprises compounds having multifunctional groups capable of chemically bonding with a functional group of one said carbon fiber and a functional group of said thermoplastic matrix material.

3. The carbon fiber composite material according to claims 1 or 2, wherein said bridging agent excludes multifunctional amine compounds having metal-oxygen bonds.

4. The carbon fiber composite material according to claims 1 or 2, wherein said bridging agent includes multifunctional amine compounds and azo compounds.

5. The carbon fiber composite material according to claim 4, wherein said multifunctional amine compounds are selected from the group consisting of: 1,4-diaminopiperazine hydrochloride;

diethylenetriamine; 1,12-diaminododecane; 1,3-diaminopropane;
1,8-diaminonaphthalene; urea; 1,4-phenylenediamine, and 4-aminophenyl sulfone.

6. The carbon fiber composite material according to claim 4, wherein said azo compounds are selected from the group consisting of:
aminoazobenzene; 4-4' azobis (4-cyanovaleric acid); and Fast Garnet GBC salt.

7. A method for adhering carbon fibers to a thermoplastic matrix material in a carbon fiber composite material comprising the step of: adding a bridging agent to the thermoplastic matrix material and the carbon fibers prior to the consolidation of the carbon fiber composite material.

8. The method for adhering according to claim 7, wherein said bridging agent comprises compounds having multifunctional groups capable of chemically bonding with a functional group said carbon fiber and a functional group of said thermoplastic matrix material.

9. The method for adhering according to claims 8 (or 9), wherein said bridging agent excludes multifunctional amine compounds having metal-oxygen bonds.

10. The method for adhering according to claims 8 or 9, wherein said bridging agent includes multifunctional amine compounds and azo compounds.

11. The method for adhering according to claim 10, wherein said multifunctional amine compounds are selected from the group consisting of: 1,4-diaminopiperazine hydrochloride; diethylenetriamine;
1,12-diaminododecane; 1,3-diaminopropane; 1,8-diaminonaphthalene;
urea; 1,4-phenylenediamine; and 4-aminophenyl sulfone.

12. The method for adhering according to claim 10, wherein said azo compounds are selected from the group consisting of:
aminoazobenzene; 4-4' azobis (4-cyanovaleric acid); and Fast Garnet GBC salt.