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Title:
CARBON FIBER SIZING AGENTS FOR IMPROVED EPOXY RESIN WETTABILITY AND PROCESSABILITY
Document Type and Number:
WIPO Patent Application WO/2017/151722
Kind Code:
A1
Abstract:
The present invention provides aqueous sizing compositions for carbon fibers comprising, as solids, from 50 to 100 wt.% or, preferably, 80 wt.% or more, or, more preferably, 94 wt.% or more of one or more ethoxylated oleamides having a weight average of from 3 to 30 ethylene oxide groups or, preferably, from 4 to 25 ethylene oxide groups, as well as the carbon fibers sized with the aqueous sizing compositions. The aqueous sizing compositions enable one to provide sized carbon fiber containing epoxy resin articles having improved matrix resin infusion into the fiber and good coefficient of friction, assuring good processability.

Inventors:
BANK DAVID H (US)
BAUMER RICHARD (US)
BOUCK KEVIN J (US)
CAI JUN (US)
LANGHORST MARSHA L (US)
REESE JASON A (US)
WANG WEIJUN (US)
YOUNG TIMOTHY J (US)
Application Number:
PCT/US2017/020124
Publication Date:
September 08, 2017
Filing Date:
March 01, 2017
Export Citation:
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Assignee:
DOW GLOBAL TECHNOLOGIES LLC (US)
International Classes:
D06M13/419; C08J5/04; D06M13/17
Domestic Patent References:
WO1996010616A11996-04-11
Foreign References:
JPH08260254A1996-10-08
CN104928933A2015-09-23
GB380851A1932-09-12
EP0790337A11997-08-20
GB2175576A1986-12-03
US5783305A1998-07-21
Other References:
J. L. THOMASON; L. YANG: "Temperature dependence of the interfacial shear strength in glass-fibre polypropylene composites", COMPOSITES SCIENCE AND TECHNOLOGY, vol. 71, 2011, pages 1600 - 1605
Attorney, Agent or Firm:
MERRIAM, Andrew (US)
Download PDF:
Claims:
We claim:

1 . An aqueous composition for sizing carbon fibers comprising from 50 to 1 00 wt.%, based on the total solids in the composition, of an ethoxylated oleamide having a weight average of from 3 to 30 ethylene oxide groups.

2. The aqueous composition as claimed in claim 1 , wherein the ethoxylated oleamide has a weight average of from 9 to 20 ethylene oxide groups.

3. The aqueous composition as claimed in claim 1 , wherein the ethoxylated oleamide has a weight average of from 4 to 25 ethylene oxide groups.

4. The aqueous composition as claimed in claim 1 , wherein the aqueous composition comprises from 80 to 100 wt.%, based on the total solids in the composition, of the ethoxylated oleamide.

5. The aqueous composition as claimed in claim 1 , wherein the aqueous composition comprises from 94 to 100 wt.%, based on the total solids in the composition, of the ethoxylated oleamide.

6. The aqueous composition as claimed in claim 1 , wherein the total solids content in the aqueous composition ranges from 0.1 to 5 wt.%.

7. The aqueous composition as claimed in claim 1 , wherein the composition is substantially free of bisphenol A.

8. A carbon fiber composition comprising sized carbon fibers treated with a sizing composition of from 0.1 to 5 wt.% as solids, based on the total weight of the thus treated fibers, the sizing composition containing from 50 to 1 00 wt.%, based on the total solids in the composition, of an ethoxylated oleamide having a weight average of from 3 to 30 ethylene oxide groups.

9. The carbon fiber composition as claimed in claim 8, wherein the fibers comprise carbon fibers as continuous carbon fibers, carbon fiber bundles or chopped carbon fibers.

10. An epoxy resin composition comprising one or more epoxy resins, epoxy hybrid resins or epoxy resin blends, and sized carbon fibers treated with from 0.1 to 5 wt.%, based on the total weight of the thus sized carbon fibers, of a sizing composition of from 50 to 100 wt.%, based on the total solids in the sizing composition, of an ethoxylated oleamide having a weight average of from 3 to 30 ethylene oxide groups.

Description:
CARBON FIBER SIZING AGENTS FOR IMPROVED EPOXY RESIN

WETTABILITY AND PROCESSABILITY

The present invention relates to aqueous compositions for sizing carbon fibers comprising one or more ethoxylated oleamides, as well as to carbon fibers treated therewith and epoxy compositions containing the thus treated carbon fibers. More particularly, the present invention relates to aqueous sizing compositions comprising one or more ethoxylated oleamides having a weight average number of ethylene oxide groups of from 3 to 30 or, preferably, from 4 to 25, the compositions having a solids content of from 0.1 to 5.0 wt.%, as well as to sized carbon fibers treated with from 0.1 to 3 wt.% of the composition solids, for example, chopped carbon fibers, and epoxy resin compositions containing the sized carbon fibers.

Carbon fibers are brittle and require sizing materials on their surface as lubricants to enable improved fiber processing and protect the fibers from damage during handling and the fabrication of intermediates, e.g. fabric. Acceptable sizing compositions provide low friction and consistent handling that allow for easy processing and that prevent residual build-up on processing equipment. In addition, carbon fibers are used to reinforce or fill resin matrix materials; thus, the sizing compositions must be compatible with resin matrix materials formulated to contain the sized carbon fibers.

U.S. patent no. 5,783,305, to Masaki et al. (Masaki) discloses that a reaction product A) made from ethoxylated monoalkyl esters of bisphenol A and saturated aliphatic dicarboxylic acids can be used as sizing agents for carbon fibers and allow the thus treated carbon fiber to be processed so as not to give fluffs. Masaki also discloses that the sizing agents can further comprise up to 1 .5 parts by weight of an alkylene oxide adduct of an amide of a polyamine and a fatty acid per each part of reaction product A). However, while such carbon fibers can be processed without making any fluff, the compositions of Masaki fail to provide a bisphenol A free sizing composition and fail to disclose acceptable epoxy matrix resin wettability of the sized fibers.

The present inventors have endeavored to provide sizing compositions for carbon fibers that allow for acceptable carbon or graphite fiber processing without fraying, good interfacial bonding between the fibers and the resin matrix, and that provide improved resin matrix uptake or infusion into the carbon fibers in making epoxy resin composites. STATEMENT OF THE INVENTION

1 . In accordance with the present invention, aqueous compositions for sizing carbon fibers comprise from 50 to 100 wt.%, or, preferably, from 80 to 100 wt.%, or, more preferably, from 94 to 99.5 wt.%, or, even more preferably, 97 wt.% or more, based on the total solids in the composition, of an ethoxylated oleamide having a weight average of from 3 to 30 ethylene oxide groups, or, preferably, from 4 to 25 ethylene oxide groups, or, more preferably from 9 to 20 ethylene oxide groups.

2. In accordance with the present invention as in item 1 , above, wherein the ethoxylated oleamide comprises the ethoxylated reaction product of oleic acid or its salt with an amine that contains one or more hydroxyl groups, preferably, one or more primary hydroxyl groups, such as an alkanolamine, a dialkanolamine or a trialkanolamine.

3. In accordance with the present invention as in any one of items 1 , or 2, above, wherein the total solids content in the aqueous compositions ranges from 0.1 to 5 wt.% or, preferably, from 0.2 to 5 wt.%, or, more preferably, from 0.2 to 3 wt.% or, even more preferably, 2 wt.% or less and/or 0.35 wt.% or more.

4. In accordance with the present invention in any one of items 1 , 2, or, 3, above, wherein the composition has a viscosity at 20 °C as determined with a fluids rheometer (ARES RFSIII, TA Instruments- Waters LLC, New Castle, DE) equipped with a cup and bob fixture and taking the intersection between two sets of data, one taken from an experiment that varied shear rates, in steady shear flow, of from 0.03 to 300/s, and a second one at varied oscillation frequencies, in oscillatory shear flow, of from 100 to 0.1 rad/s of from 100 to 0.1 rad/s of from 0.8 to 100 centipoises (cPs), or, preferably, from 0.8 to 20 cPs, or, more preferably, from 1 to 10 cPs.

5. In another aspect of the present invention, carbon fiber compositions comprise sized carbon fibers treated with a sizing composition in the amount of from 0.1 to 5 wt.% as solids, or, preferably, from 0.2 to 3 wt.% as solids, or, more preferably, from 0.2 to 3 wt.%, or, even more preferably, less than 2 wt.% as and/or 0.35 wt.% or more solids, based on the total weight of the thus treated fibers, the sizing composition containing from 50 to 100 wt.%, or, preferably, from 80 to 100 wt.%, or, more preferably, from 94 to 99.5 wt.%, or, even more preferably, 97 wt.% or more, based on the total solids in the composition, of an ethoxylated oleamide having a weight average of from 3 to 30 ethylene oxide groups, or, preferably, from 4 to 25 ethylene oxide groups, or, more preferably from 9 to 20 ethylene oxide groups. 6. In accordance with the present invention as in item 5, above, wherein the ethoxylated oleamide comprises the ethoxylated reaction product of oleic acid or its salt with comprises the ethoxylated reaction product of oleic acid or its salt with an amine that contains one or more hydroxyl groups, preferably, one or more primary hydroxyl groups, such as an alkanolamine, a dialkanolamine or a trialkanolamine.

7. In accordance with the present invention as in any one of items 5, or 6, above, wherein the fibers comprise carbon fibers as continuous carbon fibers, carbon fiber bundles or chopped carbon fibers.

8. In yet another aspect of the present invention, epoxy resin compositions comprise one or more epoxy resins, for example, bisphenol A or bisphenol F epoxy resin, epoxy hybrid resins or epoxy resin blends, and sized carbon fibers treated with from 0.1 to 5 wt.% or, preferably, from 0.2 to 5 wt.%, or, more preferably, from 0.2 to 3 wt.%, or, more preferably, 2 wt.% or less and/or 0.35 wt.% or more, based on the total weight of the thus sized carbon fibers, of a sizing composition of from 50 to 1 00 wt.%, or, preferably, from 80 to 100 wt.%, or, more preferably, from 94 to 99.5 wt.%, or, even more preferably, 97 wt.% or more, based on the total solids in the composition, of an ethoxylated oleamide.

9. In accordance with the present invention as in item 8, above, wherein the ethoxylated oleamide in the sizing composition has a weight average of from 3 to 30 ethylene oxide groups, or, preferably, from 4 to 25 ethylene oxide groups, or, more preferably, a weight average of from 9 to 20 ethylene oxide groups.

10. In accordance with the present invention as in item 8 or 9, above, wherein the epoxy resin compositions comprise from 65 to 400 phr or, preferably, from 90 to 300 phr or, more preferably, from 95 to 300 phr of the sized carbon fibers.

1 1 . In accordance with the present invention as in any one of items 8, 9 or 10, above, wherein the fibers comprise continuous carbon fibers or chopped carbon fibers.

12. In accordance with the present invention in any one of items 8, 9, 10, or 1 1 , above, wherein the epoxy resin compositions comprise a sheet molding compound of chopped carbon or graphite fibers or a woven or non-woven article of continuous carbon or graphite fibers.

13. In accordance with the present invention as in any one of items 5 to 12, above, wherein the carbon fibers comprise carbon or graphite fibers. 14. In accordance with the present invention as in item 1 3, above, wherein the carbon fibers have a first layer of surface oxidation and as second layer, the sizing composition.

15. In accordance with the present invention as in any one of items 1 to 4, above, wherein the aqueous composition for sizing carbon fibers is substantially free, or, preferably, free of bisphenol A.

16. In accordance with the present invention as in any of items 5 to 7, wherein the sized carbon fibers are substantially free, or, preferably, free of Bisphenol A.

Unless otherwise indicated, conditions of temperature and pressure are room temperature and standard pressure, also referred to herein as "ambient conditions".

The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

The endpoints of all ranges directed to the same component or property are inclusive of the endpoint and independently combinable. Thus, for example, a disclosed range of from 0.5 to 15 wt.%, or, preferably, from 0.5 to 5.0 wt.%, or, more preferably, from 1 to 3 wt.% means any and all of from 0.5 to 15 wt.%, or, preferably, from 0.5 to 5.0 wt.%, or, more preferably, from 1 to 3 wt.%, or from 0.5 to 1 wt.%, or from 0.5 to 3 wt.%, or, preferably, from 3 to 5 wt.%, or, preferably, from 1 to 5 wt.%, or from 1 to 15 wt.%, or from 3 to 15 wt.%, or from 5 to 15 wt.%.

As used herein, the term "aqueous" means water or water mixed with up to

50wt.%, or up to 25 wt.%, or, preferably, from 0 to 10 wt.%, based on the total weight of a mixture of water and solvent, of one or more water miscible solvents which is volatile under ambient conditions, such as a lower alkanol, an ether, or a ketone.

As used herein, the term "phr" means per hundred parts resin, by weight.

Unless otherwise indicated, the resin refers to the total amount of resin in a given composition, including blends and combinations of more than one different resin, as well as curing agents and reactive diluents.

As used herein, the term "polyamine" means any amine containing compound having three or more amine groups including terminal amine groups.

As used herein, the term "solids" or "total solids" excludes organic solvents and refers to the non-volatile content of a composition, wherein volatiles comprise anything that boils or is a gas at 100 °C, such as water, ammonia or methyl ethyl ketone. As used herein, the term "substantially free of bisphenol A" means that the composition or article contains less than 500 ppm, on a solids weight basis, of added bisphenol A or of bisphenol A as an impurity such as, for example, the amount of unreacted bisphenol A in any ethoxylated bisphenol A.

As used herein, unless otherwise indicated, the term "weight average number of ethylene oxide groups" means that amount determined by measuring the weight average molecular weight of a given compound by gel permeation chromatography (GPC) against poly(ethylene glycol) molecular weight standards sufficient to resolve the number of ethylene oxide groups to within a single such group, subtracting the molecular weight (formula weight) of the groups other than ethylene oxide groups, for example, bisphenol A, from the weight average molecular weight, and then dividing the result by the molecular weight of ethylene oxide.

As used herein, the term "wt.%" refers to weight percent.

The present inventors have found that a layer of a sizing composition of ethoxylated oleamide on a carbon fiber results in enhanced epoxy matrix resin infusion, improved fiber processability, and good interfacial bonding in the fabrication of high performance carbon fiber composites. At the same time, the sizing composition provides fiber processability and reduced fluff while ensuring

compatibility with the epoxy resin compositions that can be used as matrix resins without a need for epoxy resin in the sizing composition.

The aqueous sizing compositions of the present invention are made by simple mixing of one or more ethoxylated oleamides (the number of ethylene oxide groups and the amine containing portions thereof can vary) in an aqueous medium. The ethoxylated oleamides compounds of the present invention are water dispersible. Thus, the aqueous sizing composition of the present invention can be made by simple mixing of the ingredients with or in an aqueous medium.

The ethoxylated oleamides of the present invention can be made by reaction of oleic acid or its salts with an amine containing one or more hydroxyl groups, preferably, one or more primary hydroxyl groups, such as, a hydroxy functional amine, a hydroxy functional diamine, for example, ethanol amine, diethanol amine, followed by ethoxylation in a conventional manner.

The ethoxylated oleamides of the present invention can be purchased, for example, the SERDOX NXC series of specialty materials from Elementis Specialties, Netherlands B.V. In the aqueous sizing compositions of the present invention, too high a number of ethylene oxide groups in the ethoxylated oleamide can degrade compatibility of the sized carbon fiber with matrix, whereas to low a number of such groups can adversely impact the wetting of the fiber with the sizing composition.

Preferably, the performance of the aqueous sizing compositions in terms of all of fiber processability, interfacial bonding, reduced carbon fiber fluff, and compatibility with the epoxy resin matrix is best when the aqueous sizing composition aqueous sizing compositions contain 100 wt.%, or 94 wt.% or more, or 97 wt.% or more of the ethoxylated oleamide of the present invention.

The aqueous sizing compositions of the present invention can include up to 50 wt.% or, up to 20 wt.% or, more preferably, up to 6 wt.%, or, most preferably, 3 wt.% or less wt.% as solids, based on total solids wt.%, of one or more formulation chemicals. Suitable formulation chemicals can comprise nonionic surfactants, emulsifiers, water dispersible epoxy resins, thermoplastic resins, and antifoaming agents, such as silicone containing oils.

The aqueous compositions of the present invention can be substantially free or free of bisphenol A; however, the compositions may contain ethoxylated bisphenol A having a weight average of from 2 to 30, or, preferably, from 3 to 20 ethylene oxide groups.

A suitable ethoxylated bisphenol A can be made in a conventional fashion by addition of ethylene oxide to bisphenol A. An ethoxylated bisphenol A can also be purchased, for example, the SYN FAC 9000 series of bisphenol A ethoxylates from Milliken Chemicals, Inc, Greenville, SC.

Suitable carbon fibers in the present invention can be any such as Type I (high modulus - HM) and Type I I (high tensile strength - HT) carbon fiber, and can also include graphite fibers. Carbon fibers can be formed in a conventional fashion from polyacrylonitrile (PAN), pitch or hydrocarbon feedstocks, and Rayon™ cellulosic polymer feedstocks, for example, any such polymers having high strength and high moduli of elasticity. Such carbon fibers can have a tensile modulus of elasticity ranging from 165 GPa to 800 GPa and further preferably ranging from 200 GPa to 800 GPa at room temperature.

Preferably, for increased adhesion of the sizing composition of the present invention to a given carbon fiber, the carbon fibers of the present invention are preferably subject to surface oxidation treatment and thereby have a first layer of surface oxidation. The suitable carbon fibers may be subjected to liquid phase or vapor phase surface oxidization treatment in advance of sizing. Suitable methods for surface oxidization treatment may include subjecting carbon fiber to

electrochemical oxidation using the carbon fiber as the anode, with an electrolyte solution of an oxidant compound having any of a hydroxyl (C-OH) group, carbonyl (C=O) group, carboxyl (COOH) group, an ammonium bicarbonate as the and varied current densities [31 ]. Oxidation treatment in an electrolytic aqueous solution is preferable because of its advantages, including its convenience. Solutions for electrolytic treatment are not particularly limited, and may be a sulfuric acid solution or an ammonium carbonate solution, for example. To minimize damage to the carbon fiber, an appropriate example of electricity for electrolytic treatment ranges from 0 (no treatment) to 1 00 coulombs per gram of carbon fiber.

The carbon fiber sizing methods of the present invention may comprise the surface oxidation treatment and then treating the carbon fibers with the sizing composition as a second layer, for example, in an aqueous bath, followed by drying the thus treated carbon fibers.

The aqueous sizing compositions of the present invention can be applied to the carbon fibers as sizing solution bath at an elevated temperature, e.g. of from 30 to 100 °C. In a sizing bath, the amount of size retained on the carbon fibers and the effectiveness of the bath depend on sizing times, bath temperature, sizing line speeds, and carbon fiber tension.

The drying of the sized carbon fibers of the present invention may comprise drying at room temperature or heating to elevated temperatures to remove water or solvent in air or inert atmosphere.

The sized carbon fibers of the present invention can then be processed by winding, such as around a bobbin, and then chopping to make chopped carbon fibers, by weaving so as to form a fabric or a wound thread, or spreading the fibers such as for use in forming tape.

The sized carbon fibers of the present invention, whether chopped or continuous, can be further processed by contacting them with a matrix resin comprising epoxy resin compositions (as in a prepreg), or by laying chopped random carbon fibers on an epoxy resin composition film, as in sheet molding compounds (SMC), or by extruding the carbon fiber or a spread fiber array with the epoxy resin compositions as in bulk molding compounds (BMC), or by compression molding which comprises placing the sized carbon fiber as a woven or non-woven fabric in a mold, injecting the matrix epoxy resin compositions and pressing, or by filament winding of resin infused fibers onto a substrate, such as a pressure vessel. In such further processing, the prepreg, resin infused fiber, the chopped random fiber or SMC materials are intermediates that can later be cured and yet even further processed, such as by compression molding. Any of the intermediates can be made as or formed into a specific three dimensional shape for further processing.

The epoxy resin compositions of the present invention can further comprise the sized carbon fibers of the present invention in combination with other reinforcing fibers to provide strength to the polymer matrix for reinforcement. Fibers suitable for epoxy resin matrix reinforcement include, for example, ceramic fibers, synthetic organic fibers, natural fibers, mineral fibers, metal fibers, and other forms of fibers.

Suitable epoxy resins for use in making the epoxy resin compositions of the present invention include any epoxy resin compositions, for example, bisphenol A or bisphenol F epoxy resin, as well as epoxy novolac resins, epoxy hybrid resins, e.g acrylic epoxy hybrids or polyester epoxy hybrids or urethane epoxy hybrids, or epoxy resin blends.

The epoxy resin compositions of the present invention can comprise a prepreg, a sheet molding compound of chopped carbon or graphite fibers, an extruded bulk molding compound of carbon or graphite fibers, a woven or non-woven article of continuous carbon or graphite fibers, or a non-woven article of chopped or random carbon or graphite fibers.

Epoxy resins used in the present invention may be combined with an appropriate curing agent, such as an aromatic or aliphatic amine, internal mold release agent, viscosity modifiers such as diluents or thickeners. Epoxy resins are formulated to achieve desired processing characteristics, such as, for example, infusion epoxy resin formulation into the carbon fiber intermediate, such as chopped fiber or fabric; to achieve desired processing characteristics of epoxy and carbon fiber

intermediates, such as uncured (B-staged) carbon fiber and epoxy mixtures intermediates such as prepregs and sheet molding compounds with appropriate tack for handling and viscosity for molding; or to achieve final desired molded composite article performance attributes, such as glass transition temperature, composite tensile and flexural strength and fiber volume fraction.

EXAMPLES The following examples serve to better illustrate the invention, which is not intended to be limited by the examples.

The following materials were used in the examples

Unsized carbon fibers are 12K A42 carbon fiber (DowAksa, Yalova, Turkey). After a conventional carbon fiber graphitization process, the carbon fiber was treated with a basic electrolyte.

CHEMITYLEN AK-1 is a commercial sizing material of 20-30 wt% of unsaturated polyester, 1 0-20 wt% of liquid bisphenol A diglycidyl ether epoxy resin, and 50-60 wt% of water (Sanyo Chemical Industries, Ltd, Kyoto, Japan).

Ethoxylated bisphenol A (BPAEO) sizing material of the following formula:

Ethoxylated oleamides having ethylene oxide groups, include SERDOX NXC3 materials with 3 such ethylene oxide groups (Elementis Specialties, Netherlands B.V.), SERDOX NXC6 materials with 6 ethylene oxide groups (Elementis), and SERDOX NXC14 with 14 ethylene oxide groups (Elementis). For example, the ethoxylated oleamide sold under the name SERDOX NXC 3 has the following formula, wherein n = 3:

Resin infusion studies were conducted with D.E.R. 383 glycidyl ether of bisphenol A liquid epoxy resin (Olin Corporation, Clayton, MO).

Unless otherwise indicated, the term "liquid epoxy resin" means D.E.R. 383 bisphenol A glycidyl ether liquid epoxy resin.

Interfacial shear strength (IFSS) tests were conducted with a formulated epoxy matrix resin, as is disclosed in the following paragraph. A matrix epoxy resin was formulated from a blend of 100 wt.% of D.E.R. 383 bisphenol A glycidyl ether liquid epoxy resin 4 phr (which in this formulation is based on the weight of the DER 383 epoxy resin) of Licolub WE-4 montanic acid (Clariant SE, Germany), 2.5 phr of Technicure™ NanoDicy™ dicyandiamide curing agent (A &C Catalysts, Inc., Linden, NJ), 3.0 phr of Curezol™ 2MZA-PW imidazole curing agent (Shikoku Chemicals Corporation, Japan) and 6 phr of Baxxodur™ ECX210 (MSDS indicates a mixture of 1 ,3-Cyclohexanediamine, 4-methyl- and 1 ,3- Cyclohexanediamine, 2-methyl- (BASF Corporation, Florham Park, NJ).

The following Test Methods were used in the Examples:

Sizing level: The indicated sized fiber was weighed before placing the fiber in a furnace purged with nitrogen. The fiber was then heated to 450 ° C and then held at the temperature for 1 5 min. After cooling to room temperature, the pyrolyzed fiber was weighed again. The sizing level was calculated as the weight difference before and after pyrolysis as a percentage of the original fiber weight. An acceptable sizing level result is from 0.2 to 3 wt.%, preferably from 0.35 to 2 wt.%.

Matrix Resin Infusion into Fiber Bundle (Washburn method): A piece of 75 mm length of the indicated fiber was cut from a fiber tow. The cut fiber was doubled over and inserted into a 2.54 cm (1 inch) long, 1 .5 mm inner diameter (I.D.) clear, semi- flexible plastic tube. The loose ends of the fiber were trimmed. The tube with the fiber was hung on a microbalance (Kruss K12 tensiometer, Kruss GmbH, Hamburg, DE). The indicated resin was pre-heated to 40 °C prior to infusion A container filled with indicated matrix resin was placed underneath the trimmed ends of the fiber. To start the measurement, the resin was raised until it touched the bottom of the fiber sample. The weight of resin infused over time by the fiber was recorded to evaluate resin uptake by the fiber bundle. The data recording was stopped when there was no change in weight over a 20 second period. The resin infusion experiment was usually completed in 5 to 15 min.

For each fiber and resin combination, three experiments were carried out to obtain an average of the amount of resin infused into the fibers.

Coefficient of friction (COF): One end of a single 12k (filament bundle) carbon fiber tow was clamped in a 100 N load cell installed on an INSTRON device (model #5567A, Illinois Tool Works, Inc., Norwood, MA), while the other end was threaded through a zig-zag pattern of five (5) stainless-steel pins (0.635 cm (0.25")" in outer diameter) and secured to a 100 g mass, such that the carbon fiber tow was suspended from the load cell, with the mass below all of the metal pins. The total wrap angle of the tow with the pins was 360 degrees. The position of the fiber was adjusted such that the end of the tow connected to the 100 g mass was at least 50 mm below the lowest pin on COF test apparatus. The load cell was then engaged; the initial force on the load cell was recorded; and the fiber was displaced upwards 50 mm at 100 mm/min. Following ASTM D3108 (2013), the coefficient of friction μ was calculated as follows:

Equation I: μ = ln(F/F_.oad)/e

Wherein,

F is the average measured force during the last 20 mm of vertical displacement of the carbon fiber tow with the 100 g mass connected

Fi_oad is the measured preload due to the 100 g mass connected to the tow Θ is the total contact angle of the tow with the pins which, for each pin is the angle created by the leg of the tow below the pin and above the pin; here Θ equals 2π radians or 360 deg.

For each sized fiber tested, five specimens were tested to obtain an average COF. The metal friction pins of the COF apparatus were cleaned with an alcohol wipe after testing each set of fibers.

Interfacial Shear Strength (IFSS): The formulated matrix epoxy resin and sized fibers were subject to a microbond test to determined IFSS. The microbond test measures the force required to displace a drop of the indicated cured epoxy resin cured so that it adhered around a single carbon fiber filament sized with the indicated composition. See, for example, J. L. Thomason and L. Yang, "Temperature dependence of the interfacial shear strength in glass-fibre polypropylene

composites," Composites Science and Technology, 71 (201 1 ) at 1600-1605. In the test, the sized fiber is glued to a paper tab and the cured resin droplet is adhered on the free end of the sized fiber. The IFSS test fixture is installed in the grips of a tension test instrument tension test instrument (TA.XT PLUS (Texture Analyser Stable Micro Systems, Godalming, Surrey, UK). The cured resin droplet is suspended from the test fixture, consisting of a metal slit -25 urn in width and having approximately parallel edges, with the fiber hanging through the slit. The paper tab is clamped into immovable grips below the test fixture; the Texture Analyzer is actuated to displace the cured resin droplet (bead length L) from the sized fiber (fiber diameter D), and the peak force (Fp) is recorded. The IFSS is then calculated using Formula (I), below:

Comparative Example A: Unsized carbon fibers were sized with CH EMITYLEN

™ AK-1 sizing material which was diluted with water to obtain a diluted sizing dispersion with 2.5 wt.% solids. The sized carbon fiber had a sizing level of about 1 .5 wt.%. Based on three trials with the carbon fiber, the average total amount of the epoxy (D.E.R. 383) resin infused into the fiber bundle was 0.069 g of resin. The sized fiber had a COF of 0.33; and, the sized fiber and cured formulated matrix epoxy resin droplet had an IFSS of 62 MPa.

Example 1 A:

Using a continuous process, unsized carbon fiber was pulled by a 5 roller feed Godet set roller unit (model FR-N0.6-SRV, Izumi International, Inc. Greenville, SC) from the creel stand and then fed through a bath of a prepared, room temperature (-20 °C), aqueous sizing composition of ethoxylated oleamide having a weight average number of 3 ethylene oxide groups (Serdox™ NXC 3, Elementis Specialties Netherlands B.V.). The aqueous sizing composition was diluted with water to prepare a solution with 0.6 wt% solids. The sizing application time was 4 seconds. The sized carbon fiber tow was pulled by the tension controlled winder from the sizing bath through the dryer, maintained between 149 to 1 53 °C via a controller, at a line speed of 3 m/min, for a total drying time of 43 sec to remove the water and produce sized carbon fiber. The dried carbon fiber tow is collected on the spool of the winder. The fiber tension was monitored between the dryer and the winder, using a hand held tension meter (ELECTROMATIC DTMB-1 K, Electromatic

Equipment Co., INC), and found at the winder to be 500-700 g. Finally, sized fiber was placed in a vacuum oven (vacuum strength of 23 cmHg) for 4 hrs at 1 15 °C. The sizing level of the sized fiber in this example was 0.7 wt%.

The average total amount of resin infused by the fiber bundles in three trials of the matrix resin was 0.092 g, of D.E.R. 383 liquid epoxy resin.

Compared to the sized fiber in Comparative Example A, epoxy resin uptake by the sized fiber of Example 1 A was significantly greater. The COF of the sized fiber in this example was 0.27. This was lower than the COF of the sized fibers in Comparative Example A. The IFSS of the sized fiber and cured resin droplet in this example was 65 MPa, which was similar to that of the sized fibers in Comparative Example A.

Example 1 : Unsized carbon fibers were sized in the manner of sizing used in Example 1 A, except with a sizing material of an ethoxylated oleamide having a weight average of 14 ethylene oxide groups (Serdox™ NXC 14, Elementis). The material was diluted with water to prepare a solution with 0.6 wt.% solids. The sizing level of the sized fiber in this example was 0.6 wt%.

The average total amount of resin infused into the fiber bundle from three trials was 0.101 g of D.E.R. 383 liquid epoxy resin.

Compared to the sized fiber in Comparative Example A, there was a substantial increase in D.E.R. 383 resin infusion uptake. Compared to Example 1 A, the D.E.R. 383 resin infusion update increased about 10%, indicating that increasing the average number of ethylene oxide groups in the ethoxylated oleamide above 3 groups improves epoxy resin infusion of sized carbon fiber. The COF of the sized fiber in this example was 0.26. These data suggest that the sized fiber in this example should have better processability than fibers from Comparative Example A when contacting metal fiber processing equipment.

The IFSS of the sized fiber and cured resin droplet in this example was 59 MPa, which was similar to that of the sized fibers in Comparative Example A.

In conclusion, the inventive sizing compositions of an ethoxylated oleamide with a from 3 to 20 ethylene oxide (EO) units provide enhanced epoxy resin infusion, improved fiber processability, and good interfacial bonding in the fabrication of high performance carbon fiber composites.