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.

What is claimed is: 
     
         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.