PITCH-BASED BICOMPONENT CARBON FIBERS

Abstract

Bicomponent carbon fibers may comprise an inner region that is at least partially surrounded by an outer sheath, each comprising at least one carbonized pitch. The inner region comprises 70 wt % or greater mesophase pitch that has been carbonized, and the outer sheath comprises up to 70 wt % mesophase pitch that has been carbonized. An amount of mesophase pitch in the outer sheath is lower than in the inner region. The bicomponent carbon fibers may be formed by extrusion of first and second pitch compositions having the requisite amounts of mesophase pitch, followed by carbonization.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of U.S. Provisional Patent Application No. 63/589,424, filed Oct. 11, 2023, which is incorporated by reference in its entirety.

FIELD

The present disclosure relates to carbon fibers and, more particularly, to carbon fibers produced by pyrolysis of pitch.

BACKGROUND

Carbon fibers have found many commercial applications, particularly those where high strength and lightweight materials are desired or required. Among many desirable features, carbon fibers may exhibit high stiffness, high strength to weight, and resistance to high temperatures. With ever-increasing performance requirements for a range of applications, there continues to be an ongoing increase in demand for carbon fibers having higher quality and improved mechanical properties, such as increased strength.

Carbon fibers are commonly produced through pyrolysis (carbonization) of polyacrylonitrile (PAN) or pitch. Pitch is a viscoelastic polymer-like substance originating from petroleum. As-produced pitch is usually isotropic, but as-produced pitch may be rendered anisotropic through heat treatments that result in ordering and alignment of the aromatic molecules contained therein, which may result in a liquid crystalline phase. Anisotropic pitch having a liquid crystalline phase is often referred to as mesophase pitch, and this term will be used herein. Besides production of carbon fibers, pitch compositions may be utilized as a starting material for various carbon products and applications such as, for example, refractory materials, carbon/carbon composites, synthetic graphite, graphite parts, binder and impregnated pitch for electrodes, binder and impregnated aluminum production anodes and cathodes, impregnated pitch for steel electric arc furnace electrodes, carbon foam for heat transfer applications and sound absorbers, roofing products, lubricants, consumer products (e.g., cosmetics), and the like.

Pitch-based carbon fibers may be manufactured at low cost, such as through spinning (extrusion) techniques employing an expansion zone or similar flow disturbance upstream from a spinneret. Alternative pitch-based carbon fiber manufacturing techniques may include formation of a mesh as well as introduction of baffles to the spinning process. Continuous fibers may be wound onto spools, and nonwoven fabrics, such as melt-blown or spunbond fabrics, may include fibers laid into fibrous webs or mats.

Pitch-based carbon fibers may commonly exhibit high modulus of elasticity values, which may be up to about 900 GPa when utilizing mesophase pitch as a starting material. Although the modulus of elasticity values may be high, tensile strength values, in proportion, are often rather poor and may commonly reside in a range of about 3-4 GPa. In addition, the flexural strength and compressive strength values of pitch-based carbon fibers are commonly inferior to those of PAN-based carbon fibers. The resulting poor ductility, flexural strength, and compressive strength has therefore limited use of pitch-based carbon fibers in high-performance applications, such as in composite fiber materials subject to challenging loading conditions.

SUMMARY

In some aspects, bicomponent precursor fibers of the present disclosure comprise: an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer sheath comprises up to 70 wt % mesophase pitch and an amount of mesophase pitch in the outer sheath is lower than in the inner region.

In other aspects, bicomponent carbon fibers of the present disclosure comprise: an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one carbonized pitch, the inner region comprises 70 wt % or greater mesophase pitch that has been carbonized, and the outer sheath comprises up to 70 wt % mesophase pitch that has been carbonized and an amount of mesophase pitch in the outer sheath is lower than in the inner region.

In still other various aspects, methods for producing bicomponent precursor fibers comprise: providing a first pitch composition comprising 70 wt % or greater mesophase pitch, and a second pitch composition comprising up to 70 wt % mesophase pitch; and extruding the first pitch composition and the second pitch composition to produce a bicomponent precursor fiber comprising an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer region comprises up to 70 wt % mesophase pitch and an amount of mesophase pitch in the outer sheath is lower than in the inner region.

These and other features and attributes of the disclosed fibers and methods of the present disclosure and their advantageous applications and/or uses will be apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist one of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings. The following figures are included to illustrate certain aspects of the disclosure, and should not be viewed as exclusive configurations. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to one of ordinary skill in the art and having the benefit of this disclosure.

FIG. 1 is a cross-sectional diagram of a nonlimiting example bicomponent fiber with an at least partially eccentric inner region surrounded by an outer sheath.

FIG. 2 is a cross-sectional diagram of a nonlimiting example bicomponent fiber with a concentric inner region surrounded by an outer sheath.

FIG. 3 is a cross-sectional diagram of a nonlimiting example bicomponent fiber with an inner region that is partially surrounded by an outer sheath and exposed to an outer surface of the bicomponent fiber.

DETAILED DESCRIPTION

The present disclosure relates to carbon fibers and, more particularly, to carbon fibers produced by pyrolysis of pitch.

As discussed above, there are various issues associated with pitch-based carbon fibers. To address these issues, the present disclosure provides bicomponent carbon fibers made from a bicomponent precursor fiber. As used herein, the term “bicomponent fiber” refers to fiber-like materials having two or more components (e.g., preferably two components) that are distributed with a composition gradient between the two. That is, a first region of a bicomponent fiber may have a first composition and a second region of the bicomponent fiber may have a second composition. Depending on context, such bicomponent fibers may refer to a bicomponent precursor fiber or a bicomponent carbon fiber. The term “bicomponent precursor fiber” refers to a bicomponent fiber that may be converted to a bicomponent carbon fiber through pyrolysis of one or more components therein, such as the pitch compositions in a pitch-based bicomponent precursor fiber.

Pitch-based carbon fibers may have a very high modulus of elasticity compared to other types of carbon fibers; however, pitch-based carbon fibers may exhibit relatively low compressive strength values. The present disclosure provides pitch-based bicomponent carbon fibers having balanced compressive and flexural strength, as well as tensile stiffness in the longitudinal and transverse directions, each as compared to conventional pitch-based carbon fibers, thereby facilitating potential new applications for this class of carbon fibers. To accomplish the foregoing, a bicomponent arrangement of different pitch compositions within a carbon fiber precursor may be utilized, each having a different loading of mesophase pitch. More specifically, a higher loading of mesophase pitch (e.g., 70 wt % or above based on total fiber mass) may be utilized in an inner region of the bicomponent fiber, whereas an outer sheath having a lower loading mesophase pitch (e.g., 20 wt % to 70 wt % based on total fiber mass) or even no mesophase pitch may be utilized. Thus, the amount of mesophase pitch in the inner region may differ from the amount of mesophase pitch in the outer sheath. Without being bound by theory or mechanism, the higher loading of mesophase pitch in the interior of the bicomponent fiber may allow stiffness to be maintained, while the lower (or no) loading of mesophase pitch within the outer sheath may promote an increase in compressive strength. Still further without being bound by theory or mechanism, the graphite grain size in non-mesophase pitches tends to be high, which results in a low modulus but increases the compressive strength. Hence, it may be desirable to limit the amount of mesophase pitch in the outer sheath. Similarly, mesophase pitch tends to have large, well-aligned graphitic crystals, which result in improved stiffness values. Therefore, mesophase pitch may be desirable to include in the inner region in high amounts. Such bicomponent fibers may be readily produced by co-extrusion of two pitch compositions having different loadings of mesophase pitch, followed by pyrolysis of the pitch to form the resulting bicomponent carbon fiber. Extrusion may comprise melt spinning to produce a continuous filament or melt blowing to produce a non-woven filament mat.

Accordingly, bicomponent precursor fibers of the present disclosure may comprise an inner region that is at least partially surrounded by an outer sheath, in which the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer sheath comprises up to 70 wt % mesophase pitch. The amount of mesophase pitch in the outer sheath is lower than in the inner region, such as about 20 wt % to about 70 wt % mesophase pitch. The balance of pitch in the inner region and the outer sheath may comprise isotropic pitch. Bicomponent carbon fibers of the present disclosure may be produced by carbonizing such bicomponent precursor fibers. Such bicomponent carbon fibers may comprise an inner region that is at least partially surrounded by an outer sheath, in which the inner region and the outer sheath each comprise at least one carbonized pitch, the inner region comprises 70 wt % or greater mesophase pitch that has been carbonized, and the outer sheath comprises up to 70 wt % mesophase pitch that has been carbonized. The amount of mesophase pitch that has been carbonized in the outer sheath is lower than in the inner region, such as about 20 wt % to about 70 wt % mesophase pitch that has been carbonized. The balance of pitch in the inner region and the outer sheath may comprise isotropic pitch that has been carbonized.

The bicomponent fibers disclosed herein (e.g., bicomponent carbon fibers or bicomponent precursor fibers) may have a substantially circular cross-section. That is, the outer profile of the cross-section may be round or nearly round (e.g., less than 5% eccentricity deviation from a perfect circle). Other geometric cross-sections such as triangular, square, pentagonal, hexagonal, ovular, or the like are also within the scope of the present disclosure.

The inner region and the outer sheath of the bicomponent fibers (e.g., bicomponent carbon fibers or bicomponent precursor fibers) may be arranged such that the outer sheath at least partially surrounds the inner region, including configurations in which the outer sheath completely surrounds the inner region such that the inner region is encased within the interior of the bicomponent fiber. When the inner region is not fully surrounded by the outer region, a portion of the inner region may extend to the outer surface of the bicomponent fiber, as shown hereinafter. The outer sheath may be located at a position radially outward from a longitudinal axis of the bicomponent fiber. The outer sheath may form an arc of any number of circumferential degrees (e.g., a 5° arc to a 360° arc) relative to the longitudinal axis, such that the outer sheath at least partially surrounds the inner region. The number of circumferential degrees in the arc defined by the outer sheath may similarly correlate with the fraction of the outer surface of the bicomponent fiber that comprises the outer sheath.

In some fiber configurations, the inner region and the outer sheath may be at least partially eccentric. The term “eccentric” means that the inner region is offset from the longitudinal axis of the bicomponent fiber. A diagram showing a cross-sectional view of a nonlimiting example bicomponent fiber (e.g., a bicomponent carbon fiber or a bicomponent precursor fiber) that includes an at least partially eccentric inner region surrounded by an outer sheath is shown in FIG. 1. In FIG. 1, bicomponent fiber 100 includes outer sheath 102 and inner region 104, each having centers 102c and 104c, respectively, wherein centers 102c and 104c are non-coincident.

In some fiber configurations, the inner region and the outer sheath may be concentric. A diagram showing a cross-sectional view of a nonlimiting example bicomponent fiber (e.g., a bicomponent carbon fiber or a bicomponent precursor fiber) that includes a concentric inner region surrounded by an outer sheath is shown in FIG. 2. In FIG. 2, bicomponent fiber 200 includes outer sheath 202 and inner region 204, each having shared center 203c.

In some configurations, the inner region may be exposed to an outer surface of the bicomponent precursor fiber, including configurations in which the inner region is substantially tangent to the outer surface of the bicomponent fiber. FIG. 3 is a diagram of a cross-sectional view of a nonlimiting example bicomponent fiber (e.g., a bicomponent carbon fiber or a bicomponent precursor fiber) in which the inner region is partially surrounded by an outer sheath and exposed to an outer surface of the bicomponent fiber. In FIG. 3, bicomponent fiber 300 includes outer sheath 302 and inner region 304, in which inner region 304 is exposed to outer surface 303c and may be substantially tangent to outer surface 303c. In some examples, not depicted in FIG. 3, inner region 304 may form a portion of outer surface 303c.

Bicomponent carbon fibers of the present disclosure may be obtained following pyrolysis/carbonization of a corresponding bicomponent precursor fiber, preferably following oxidation thereof. That is, the bicomponent precursor fibers may represent a “green” form of the bicomponent carbon fibers. The inner region of the bicomponent fiber (e.g., a bicomponent carbon fiber or a bicomponent precursor fiber) may constitute about 40 wt % or greater, or about 45 wt % or greater, or about 50 wt % or greater, or about 55 wt % or greater, or about 60 wt % or greater, or about 65 wt % or greater, or about 70 wt % or greater, or about 75 wt % or greater, or about 80 wt % or greater, or about 85 wt % or greater, or about 90 wt % or greater, or about 95 wt % or greater of a total mass of the bicomponent fiber, up to about 99 wt % of the total mass of the bicomponent fiber. Depending on how one wishes to balance the modulus of elasticity and the compressive strength, the ratio of the inner region and the outer sheath may be varied accordingly.

In the bicomponent precursor fiber, the inner region may comprise at least one pitch, which may comprise about 70 wt % or greater, or about 75 wt % or greater, or about 80 wt % or greater, or about 85 wt % or greater, or about 90 wt % or greater, or about 95 wt % or greater, or 100 wt % mesophase pitch, such as about 70 wt % to about 99.9 wt %, or about 80 wt % to about 99.9 wt %, or about 90 wt % to about 99.9 wt %, or about 70 wt % to about 80 wt %, or about 75 wt % to about 90 wt %, or about 90 wt % to 100 wt % mesophase pitch, each as measured relative to a total mass of the inner region. The outer sheath likewise may comprise at least one pitch, which may comprise no mesophase pitch (0 wt % mesophase pitch) up to about 70 wt % mesophase pitch, such as about 1 wt % to about 70 wt %, or about 10 wt % to about 70 wt %, or about 20 wt % to about 70 wt %, or about 20 wt % to about 60 wt %, or about 20 wt % to about 50 wt %, or about 30 wt % to about 65 wt % mesophase pitch, each as measured relative to a total mass of the outer sheath.

A combined amount of mesophase pitch in the inner region and outer sheath, based on total mass of the bicomponent precursor fiber, may range from about 25 wt % to about 99 wt %, or about 50 wt % to about 99 wt %, or about 70 wt % to about 99 wt %.

Following pyrolysis to form a bicomponent carbon fibers from a bicomponent precursor fiber, the corresponding amounts of mesophase pitch in carbonized form may be present in the inner region, the outer region, and overall in the combined amount in the inner region and the outer region of the bicomponent carbon fiber.

The at least one pitch may comprise any suitable pitch material. Examples of suitable pitch materials include, but are not limited to, coal tar, coal tar pitch, liquefied coal pitch, ethylene tar pitch, petroleum pitch, the like, or any combination thereof. Suitable pitch materials may have a softening point from 100° C. to 500° C., or about 200° C. to about 400° C., or about 250° C. to about 350° C. Suitable pitch materials may have a density from about 1 g/cm³ to about 1.5 g/cm³. Once at least partially melted to perform extrusion the pitch may be a viscous fluid, in which the viscosity may depend upon the relative amounts of isotropic and mesophase pitch contained therein.

Bicomponent carbon fibers of the present disclosure may exhibit features allowing for increased compressive and tensile strength values compared to conventional pitch-based carbon fibers. For example, bicomponent carbon fibers of the present disclosure may have a Young's modulus (ASTM C1557-20) from about 200 GPa to about 600 GPa, or about 300 GPa to about 500 GPa. As another example, bicomponent carbon fibers of the present disclosure may have a compressive strength (ASTM D3410) of about 0.5 GPa to about 3 GPa, or about 0.5 GPa to about 1.5 GPa, or about 1.5 GPa to about 3 GPa; a flexural strength (as measured using single-fiber three-point bending, as described in Naito, et al. (2009) “Flexural Properties of PAN- and Pitch-Based Carbon Fibers,” J. Am. Cer. Soc., v. 92, pp. 186-192) of about 1 GPa to about 4 GPa, or about 1 GPa to about 2.5 GPa, or about 2.5 GPa to about 4 GPa; a transverse compressive modulus (as measured for single fibers, as described in Naito, et al. (2017) “Transverse compressive properties of polyacrylonitrile (PAN)-based and pitch-based single carbon fibers,” Carbon, v. 118, pp. 168-183) of about 5 GPa to about 20 GPa, or about 5 GPa to about 10 GPa, or about 10 GPa to about 20 GPa; a transverse compressive strength (as measured for single fibers, as described in Naito, et al. (2017) “Transverse compressive properties of polyacrylonitrile (PAN)-based and pitch-based single carbon fibers,” Carbon, v. 118, pp. 168-183) of about 0.5 GPa to about 2 GPa, or about 0.5 GPa to about 1 GPa, or about 1 GPa to about 2 GPa; and a compressive strain to failure ratio (ASTMD3410) from about 0.05% to about 2%, or about 0.05% to about 1.0%, or about 0.1% to about 0.6%, or about 0.1% to 0.4%.

Bicomponent precursor fibers or bicomponent carbon fibers of the present disclosure are not believed to be particularly limited in diameter or aspect ratio. Example diameters include, but are not limited to, about 4 μm to about 25 μm, or about 5 μm to about 10 μm, or about 10 μm to about 15 μm, or about 15 μm to about 25 μm. Example aspect ratios may include, but are not limited to about 50 or greater, or about 100 or greater, or about 200 or greater, or about 500 or greater, or about 1000 or greater, or about 2500 or greater, or about 5000 or greater, or about 10000 or greater, or even about 50000 or greater.

The bicomponent precursor fibers of the present disclosure may be formed by extrusion to define the inner region and outer sheath. Extrusion may utilize an extrusion apparatus operating at any extrusion rate suitable to produce the bicomponent precursor fiber. One of ordinary skill in the art will be able to select and implement an extrusion process with a suitable extrusion apparatus to produce the bicomponent precursor fibers described herein. Preferably, a first pitch composition and a second pitch composition may be co-extruded to form the bicomponent precursor fiber. Alternately, a first pitch composition may extrude to define the inner region, which may then subsequently be overcoated (e.g., by extrusion or another suitable coating process) to define the outer sheath upon the inner region. The first pitch composition may comprise 70 wt % or greater mesophase pitch, and the second pitch composition may comprise up to 70 wt % mesophase pitch, such as 20 wt % to 70 wt % mesophase pitch, to produce a bicomponent precursor fiber and subsequently produced carbon fiber defined as above.

The above bicomponent precursor fibers may be formed into bicomponent carbon fiber following at least partially oxidizing and/or carbonizing of the bicomponent precursor fiber described above.

Oxidizing may comprise heating the bicomponent precursor fiber to an elevated temperature in a low-oxygen environment, such as a gas mixture comprising nitrous oxide, oxygen, or any combination thereof. A low-oxygen environment for use in conjunction with at least partially oxidizing the bicomponent precursor fiber according to the present disclosure may have an oxygen content of less than 15 mol %, or less than 10 mol %, or less than 5 mol %, or less than 1 mol %, such as 1 mol % to 20 mol %, or 1 mol % to 15 mol %, or 1 mol % to 10 mol %, or 1 mol % to 5 mol %. Alternately, oxidizing the bicomponent precursor fiber may take place in air or in an environment having an increased oxygen content relative to air. Air or an environment having an increased oxygen content relative to air may allow oxidation to be conducted over a shorter period of time. Oxidizing the bicomponent precursor fiber may take place at a temperature of about 100° C. to about 400° C., or about 100° C. to about 300° C., or about 200° C. to about 400° C., or about 200° C. to about 300° C. In non-limiting examples, oxidizing the bicomponent precursor fiber may take place for about 30 minutes to about 4 hours, or about 45 minutes to about 2 hours. Without being bound by theory or mechanism, oxidation of the bicomponent precursor fiber may convert the initially linear structure of the pitch into a ladder structure having crosslinks. Any suitable heating technique may be utilized to conduct the oxidation of the bicomponent precursor fiber.

After optionally at least partially oxidizing the bicomponent precursor fiber, the bicomponent precursor fiber may be carbonized (pyrolyzed) to convert the pitch into a carbon material, including graphite. Carbonizing may comprise heating the bicomponent precursor fiber to an elevated temperature, preferably in the absence or near-absence of oxygen. In non-limiting examples, heating to promote carbonization may take place at a temperature of about 900° C. or greater or about 1200° C. or greater, such as about 700° C. to about 1600° C., or about 900° C. to about 1500° C., or about 900° C. to about 1400° C., or about 1000° C. to about 1500° C. In some cases, heating above 1600° C. may be conducted, such as about 1600° C. to about 2500° C., or about 2000° C. to about 3000° C. Graphitization may occur at a temperature of about 2000° C. or greater.

ADDITIONAL EMBODIMENTS

Embodiments disclosed herein include:

• • A. Bicomponent precursor fibers. The bicomponent precursor fibers comprise: an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer sheath comprises up to 70 wt % mesophase pitch and an amount of mesophase pitch in the outer sheath is lower than in the inner region.
  • B. Bicomponent carbon fibers. The bicomponent precursor fibers comprise: an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one carbonized pitch, the inner region comprises 70 wt % or greater mesophase pitch that has been carbonized, and the outer sheath comprises up to 70 wt % mesophase pitch that has been carbonized and an amount of mesophase pitch in the outer sheath is lower than in the inner region.
  • C. Methods for making bicomponent fibers. The methods comprise: providing a first pitch composition comprising 70 wt % or greater mesophase pitch, and a second pitch composition comprising up to 70 wt % mesophase pitch; and extruding the first pitch composition and the second pitch composition to produce a bicomponent precursor fiber comprising an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer region comprises up to 70 wt % mesophase pitch and an amount of mesophase pitch in the outer sheath is lower than in the inner region.

Embodiments A-C may include one or more of the following elements in any combination:

• • Element 1: wherein the inner region has a substantially circular cross-section.
  • Element 2: wherein the inner region and the outer sheath are concentric.
  • Element 3: wherein the inner region and the outer sheath are at least partially eccentric.
  • Element 4: wherein the inner region is exposed to an outer surface of the bicomponent precursor fiber.
  • Element 5: wherein the outer sheath comprises 20 wt % to 70 wt % mesophase pitch.
  • Element 6: wherein the bicomponent carbon fiber has a Young's modulus of about 300 GPa to about 500 GPa, as measured by ASTM C1557-20.
  • Element 7: wherein the bicomponent carbon fiber has a compressive strain to failure ratio of about 0.1% to about 0.6%.
  • Element 8: wherein the bicomponent carbon fiber has a diameter ranging from about 4 μm to about 25 μm.
  • Element 9: wherein extruding forms the inner region with a substantially circular cross-section.
  • Element 10: wherein extruding forms the inner region and the outer region such that the inner region and the outer sheath are concentric.
  • Element 11: wherein extruding forms the inner region and the outer sheath such that the inner region and the outer sheath are at least partially eccentric.
  • Element 12: wherein extruding forms the inner region and the outer sheath such that the inner region is exposed to an outer surface of the bicomponent precursor fiber.
  • Element 13: wherein the first pitch composition and the second pitch composition are co-extruded to produce the bicomponent precursor fiber.
  • Element 14: wherein the method further comprises at least partially oxidizing the bicomponent precursor fiber.
  • Element 15: wherein oxidizing occurs in a gas mixture comprising nitrous oxide, oxygen, or any combination thereof.
  • Element 16: wherein the method further comprises: pyrolyzing the bicomponent precursor fiber to form a bicomponent carbon fiber.

Exemplary combinations applicable to one or more of A, B, and C include, but are not limited to: 1, and 2 or 3; 1 and 4; 1 and 5; 2 or 3, and 4; 2 or 3, and 5; 4 and 5; 1 and 6; 2 or 3, and 6; 4 and 6; 5 and 6; 1 and 7; 1 and 8; 2 or 3, and 7; 2 or 3, and 8; 4 and 7; 4 and 8; 5 and 7; 5 and 8; 6 and 7; 6 and 8; 7 and 8; 9, and 10 or 11; 9 and 12; 10 or 11, and 12; 9 and 13; 9 and 14; 9, 14, and 15; 9, and 14-16; 10 or 11, and 13; 10 or 11, and 14; 10 or 11, and 14 and 15; 10 or 11, and 14 and 16; 10 or 11, and 14-16; 12 and 13; 12 and 14; 12, 14, and 15; 12, 14, and 16; 13 and 14; 13-15; 13, 14, and 16; and 13-16.

Additional embodiments of the present disclosure are directed to the following non-limiting clauses:

• • Clause 1. A bicomponent precursor fiber comprising:
  • an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer sheath comprises up to 70 wt % mesophase pitch and an amount of mesophase pitch in the outer sheath is lower than in the inner region.
  • Clause 2. The bicomponent precursor fiber of clause 1, wherein the inner region has a substantially circular cross-section.
  • Clause 3. The bicomponent precursor fiber of clause 1 or clause 2, wherein the inner region and the outer sheath are concentric.
  • Clause 4. The bicomponent precursor fiber of clause 1 or clause 2, wherein the inner region and the outer sheath are at least partially eccentric.
  • Clause 5. The bicomponent precursor fiber of any one of clauses 1, 2, or 4, wherein the inner region is exposed to an outer surface of the bicomponent precursor fiber.
  • Clause 6. The bicomponent precursor fiber of any one of clauses 1-5, wherein the outer sheath comprises 20 wt % to 70 wt % mesophase pitch.
  • Clause 7. A bicomponent carbon fiber comprising:
  • an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one carbonized pitch, the inner region comprises 70 wt % or greater mesophase pitch that has been carbonized, and the outer sheath comprises up to 70 wt % mesophase pitch that has been carbonized and an amount of mesophase pitch in the outer sheath is lower than in the inner region.
  • Clause 8. The bicomponent carbon fiber of clause 7, wherein the inner region has a substantially circular cross-section.
  • Clause 9. The bicomponent carbon fiber of clause 7 or clause 8, wherein the inner region and the outer sheath are concentric.
  • Clause 10. The bicomponent carbon fiber of clause 7 or clause 8, wherein the inner region and the outer sheath are at least partially eccentric.
  • Clause 11. The bicomponent carbon fiber of any one of clauses 7, 8, or 10, wherein the inner region is exposed to an outer surface of the bicomponent carbon fiber.
  • Clause 12. The bicomponent carbon fiber of any one of clauses 7-11, wherein the bicomponent carbon fiber has a Young's modulus of about 300 GPa to about 500 GPa, as measured by ASTM C1557-20.
  • Clause 13. The bicomponent carbon fiber of any one of clauses 7-12, wherein the bicomponent carbon fiber has a compressive strain to failure ratio of about 0.1% to about 0.6%, as measured by ASTM D3410.
  • Clause 14. The bicomponent carbon fiber of any one of clauses 7-13, wherein the bicomponent carbon fiber has a diameter ranging from about 4 μm to about 25 μm.
  • Clause 15. The bicomponent carbon fiber of any one of clauses 7-14, wherein the outer sheath comprises 20 wt % to 70 wt % mesophase pitch.
  • Clause 16. A method comprising:
  • providing a first pitch composition comprising 70 wt % or greater mesophase pitch, and a second pitch composition comprising up to 70 wt % mesophase pitch; and
  • extruding the first pitch composition and the second pitch composition to produce a bicomponent precursor fiber comprising an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer region comprises up to 70 wt % mesophase pitch and an amount of mesophase pitch in the outer sheath is lower than in the inner region.
  • Clause 17. The method of clause 16, wherein extruding forms the inner region with a substantially circular cross-section.
  • Clause 18. The method of clause 16 or clause 17, wherein extruding forms the inner region and the outer region such that the inner region and the outer sheath are concentric.
  • Clause 19. The method of clause 16 or clause 17, wherein extruding forms the inner region and the outer sheath such that the inner region and the outer sheath are at least partially eccentric.
  • Clause 20. The method of any one of clauses 16, 17, or 19, wherein extruding forms the inner region and the outer sheath such that the inner region is exposed to an outer surface of the bicomponent precursor fiber.
  • Clause 21. The method of any one of clauses 16-20, wherein the first pitch composition and the second pitch composition are co-extruded to produce the bicomponent precursor fiber.
  • Clause 22. The method of any one of clauses 16-21, further comprising:
  • at least partially oxidizing the bicomponent precursor fiber.
  • Clause 23. The method of clause 22, wherein oxidizing occurs in a gas mixture comprising nitrous oxide, oxygen, or any combination thereof.
  • Clause 24. The method of any one of clauses 16-23, further comprising: pyrolyzing the bicomponent precursor fiber to form a bicomponent carbon fiber.
  • Clause 25. The method of any one of clauses 16-24, wherein the outer sheath comprises 20 wt % to 70 wt % mesophase pitch.
  • Clause 26. The method of any one of clauses 16-25, wherein extrusion comprises melt spinning to produce a continuous filament or melt blowing to produce a non-woven filament mat.

All documents described herein are incorporated by reference herein for purposes of all jurisdictions where such practice is allowed, including any priority documents and/or testing procedures to the extent they are not inconsistent with this text. As is apparent from the foregoing general description and the specific embodiments, while forms of the disclosure have been illustrated and described, various modifications can be made without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the disclosure be limited thereby. For example, the compositions described herein may be free of any component, or composition not expressly recited or disclosed herein. Any method may lack any step not recited or disclosed herein. Likewise, the term “comprising” is considered synonymous with the term “including.” Whenever a method, composition, element or group of elements is preceded with the transitional phrase “comprising,” it is understood that we also contemplate the same composition or group of elements with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “is” preceding the recitation of the composition, element, or elements and vice versa.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by one or more embodiments described herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the elements that it introduces.

One or more illustrative embodiments are presented herein. Not all features of a physical implementation are described or shown in this application for the sake of clarity. It is understood that in the development of a physical embodiment of the present disclosure, numerous implementation-specific decisions must be made to achieve the developer's goals, such as compliance with system-related, business-related, government-related and other constraints, which vary by implementation and from time to time. While a developer's efforts might be time-consuming, such efforts would be, nevertheless, a routine undertaking for one of ordinary skill in the art and having benefit of this disclosure.

Therefore, the present disclosure is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to one having ordinary skill in the art and having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present disclosure. The embodiments illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein.

Claims

1. A bicomponent precursor fiber comprising:

an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer sheath comprises up to 70 wt % mesophase pitch and an amount of mesophase pitch in the outer sheath is lower than in the inner region.

2. The bicomponent precursor fiber of claim 1, wherein the inner region has a substantially circular cross-section.

3. The bicomponent precursor fiber of claim 1, wherein the inner region and the outer sheath are concentric.

4. The bicomponent precursor fiber of claim 1, wherein the inner region and the outer sheath are at least partially eccentric.

5. The bicomponent precursor fiber of claim 1, wherein the inner region is exposed to an outer surface of the bicomponent precursor fiber.

6. The bicomponent precursor fiber of claim 1, wherein the outer sheath comprises 20 wt % to 70 wt % mesophase pitch.

7. A bicomponent carbon fiber comprising:

an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one carbonized pitch, the inner region comprises 70 wt % or greater mesophase pitch that has been carbonized, and the outer sheath comprises up to 70 wt % mesophase pitch that has been carbonized and an amount of mesophase pitch in the outer sheath is lower than in the inner region.

8. The bicomponent carbon fiber of claim 7, wherein the inner region has a substantially circular cross-section.

9. The bicomponent carbon fiber of claim 7, wherein the inner region and the outer sheath are concentric.

10. The bicomponent carbon fiber of claim 7, wherein the inner region and the outer sheath are at least partially eccentric.

11. The bicomponent carbon fiber of claim 7, wherein the inner region is exposed to an outer surface of the bicomponent carbon fiber.

12. The bicomponent carbon fiber of claim 7, wherein the bicomponent carbon fiber has a Young's modulus of about 300 GPa to about 500 GPa, as measured by ASTM C1557-20.

13. The bicomponent carbon fiber of claim 7, wherein the bicomponent carbon fiber has a compressive strain to failure ratio of about 0.1% to about 0.6%, as measured by ASTM D3410.

14. The bicomponent carbon fiber of claim 7, wherein the bicomponent carbon fiber has a diameter ranging from about 4 μm to about 25 μm.

15. The bicomponent carbon fiber of claim 7, wherein the outer sheath comprises 20 wt % to 70 wt % mesophase pitch.

16. A method comprising:

providing a first pitch composition comprising 70 wt % or greater mesophase pitch, and a second pitch composition comprising up to 70 wt % mesophase pitch; and

extruding the first pitch composition and the second pitch composition to produce a bicomponent precursor fiber comprising an inner region that is at least partially surrounded by an outer sheath, wherein the inner region and the outer sheath each comprise at least one pitch, the inner region comprises 70 wt % or greater mesophase pitch, and the outer region comprises up to 70 wt % mesophase pitch and an amount of mesophase pitch in the outer sheath is lower than in the inner region.

17. The method of claim 16, wherein extruding forms the inner region with a substantially circular cross-section.

18. The method of claim 16, wherein extruding forms the inner region and the outer region such that the inner region and the outer sheath are concentric.

19. The method of claim 16, wherein extruding forms the inner region and the outer sheath such that the inner region and the outer sheath are at least partially eccentric.

20. The method of claim 16, wherein extruding forms the inner region and the outer sheath such that the inner region is exposed to an outer surface of the bicomponent precursor fiber.

21. The method of claim 16, wherein the first pitch composition and the second pitch composition are co-extruded to produce the bicomponent precursor fiber.

22. The method of claim 16, further comprising:

at least partially oxidizing the bicomponent precursor fiber.

23. The method of claim 22, wherein oxidizing occurs in a gas mixture comprising nitrous oxide, oxygen, or any combination thereof.

24. The method of claim 16, further comprising:

pyrolyzing the bicomponent precursor fiber to form a bicomponent carbon fiber.

25. The method of claim 16, wherein the outer sheath comprises 20 wt % to 70 wt % mesophase pitch.

26. The method of claim 16, wherein extrusion comprises melt spinning to produce a continuous filament or melt blowing to produce a non-woven filament mat.