Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/145—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
  • D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles

Definitions

• the invention relates to carbon fibers and particularly, a process for improving the mechanical properties of a carbon fiber.
• the invention relates to polyacrylonitrile (PAN)-based carbon fibers and mesophase pitch-based carbon fibers. These carbon fibers have found considerable commercial value because of the mechanical properties they possess. In particular, carbon fibers having high values of Young's Moduli are in'greater demand for specialized products.
• PAN polyacrylonitrile
• a PAN-based carbon fiber is produced by spinning polyacrylonitrile into a fiber, infusibilizing the fiber by raising it to an elevated temperature in air, and thereafter carbonizing the infusibilized fiber at an elevated temperature in an inert atmosphere under tension in a threadline to produce a carbon fiber.
• a mesophase pitch-based carbon fiber is produced by spinning a mesophase pitch into a fiber, infusibilizing the fiber by raising it to an elevated temperature in air, and thereafter carbonizing the infusibilized fiber at an elevated temperature in an inert atmosphere.
• the temperatures used for carbonizing mesophase pitch based carbon fibers are at least greater than about 1000°C and usually more than 1000°C and usually more than 1500°C.
• PAN-based fibers are usually carbonized at about 1300°C.
• a carbon fiber having a very high value of Young's Modulus requires elevated temperatures greater than about 2300°C and preferably greater than about 2700°C.
• the carbonizing step for PAN-based fibers and mesophase pitch-based - fibers is carried out in a threadline operation.
• a threadline operation is carried out by passing an infusibilized fiber along a linear path through a heated chamber.
• the heated chamber commonly referred to as a furnace, must be maintained at a positive pressure in order to exclude air.
• the infusibilized fiber moves at the rate of several feet per minute so that the residence time at the elevated temperature is relatively short.
• the invention relates to a process for improving a carbon fiber, comprising the steps of winding the carbon fiber onto a bobbin which is thermally and mechanically stable at temperatures greater than 2000°C and which is chemically compatible with the carbon fiber, and thereafter, subjecting the carbon fiber to a heat treatment at a temperature greater than 2000 C.
• the temperature rate for carrying out the heat treatment can be as high as from about 200°C to 500°C per hour with the final temperature being maintained for a period of from one to two hours.
• a temperature rate of from about 50°C to about 100°C per hour would enable the holding time at the final temperature to be reduced to one half hour and possibly less.
• the fiber should be maintained in the inert atmosphere until it has been cooled to a temperature at least below about 200°C to minimize the oxidation of the carbon fiber upon exposure to air.
• the final temperature for the heat treatment should be greater than about 2700°C.
• the bobbin for carrying out the new process comprises a cylindrical body made of material such as-stainless steel, or refractory oxides or boron nitride, or graphite.
• a layer of a compressible resilient carbon mater such as carbon felt can be positioned on the outside surface of the cylindrical body to receive the carbon fiber and thereby minimize the stresses on the carbon fiber during the heat treatment.
• the bobbin can be with or without end flanges.
• the bobbin should have end flanges and more preferably, the end flanges should be movable so that after the heat treatment the end flanges can be moved to abut the carbon fibers because it is known that the heat treatment results in the shrinkage of the longitudinal space occupied by the carbon fiber. Moving the flanges to abut the carbon fiber simplifies,the unwinding of the carbon fiber from the bobbin.
• the cylindrical body of the.bobbin can have an inside diameter of three inches and outside diameter of about three and a half inches with an overall length of about eleven inches.
• the carbon.felt should have a thickness of about 1/4 inch to about 1/2 inch thick.
• the layers of the carbon fiber adjacent to the bobbin are damaged,but it may be advantageous to sustain the damage of a portion of the carbon fibers and thereby avoid the use of carbon felt.
• the wind angle of the carbon fiber onto the bobbin can be generally from about 0,1° to about 2.5 0 and preferably less than about 0.4° for a bobbin having flanges.
• the tension used for winding the carbon fiber onto the bobbin should be less than about 200 g.
• fibers are spun from a spinneret which produces usually about two thousand continuous filaments and these fibers are brought together and handled together during additional operations.
• the bundle of filaments is referred to as "yarn".
• the process applying to a carbon fiber also applies to yarn comprising a plurality of carbon fibers.
• the yarn comprised two thousand filaments, each filament having a diameter of 10 microns.
• the yarn was carbonized in a threadline furnace in accordance with conventional practice at a temperature of 2400°C and thereafter, wound on to four separate graphite bobbins with a wind angle of 0.4 degrees.
• Each bobbin comprised threaded flanges on a threaded portion of the bobbin.
• the carbon yarn substantially filled the space between the flanges of each bobbin.
• the four bobbins were then loaded onto a graphite rack so that each bobbin was mounted in a horizontal position.
• the rack was placed in a graphite-susceptor induction furnace and heated under an argon atmosphere at the rate of 100°C per hour to 2950°C. The final temperature was maintained for two hours and then the furnace was allowed to cool to room temperature.
• the flanges on each bobbin were screwed inwardly to abut the carbon yarn and eliminate gaps which had formed between the flanges and the carbon arm.
• the yarn was unwound at the rate of 20 feet per minute with a tension of 150 g.
• the average Young's Modulus for the fibers taken from each of the spools A, B, C, and D was greater than 100 Mpsi. Furthermore, tests show that there was reasonable uniformity in the . properties of samples of the fibers taken from different locations in each bobbin. In addition, the fiber density was measured to be approximately 99% of the theoretical value.
• the excellent physical condition of the fibers is due to the use of the low winding angle of 0.4°. This angle and smaller angles are important for fibers being subjected to temperatures greater than 2700°C.
• a PAN-based yarn having 6,000 filaments was used in this example.
• the PAN-based yarn was prepared so that its nitrogen content was less than about 1% by weight. It is important to have a low nitrogen content for the PAN-based yarn used in the instant process so that the elevated temperatures do not cause damage to the yarn as the nitrogen being pyrolyized. out of the yarn.
• the PAN-based yarn was prepared as follows:
• the package was placed horizontally in a graphite tube induction furnace which was purged with nitrogen and fired at the rate of 50°C per hour to 800°C and thereafter temperature was raised at 250°C per hour to 1300°C. The final temperature was maintained for two hours and the package was allowed to cool back to room temperature: As a result of the heat treatment, the package had shrunk longitudinally about 1.5 to 2 inches from its original ten inch length.
• the package was then mounted horizontally on a tension-loaded payoff creel, and the yarn was unwound under a tension of approximately 50 grams, passed through a grooved-reel, tension-controlled drive system maintained at a tension of about 1,825 grams and thereafter through graphite tube electric resistance furnace having a hot zone maintained at a temperature of about 1830°C and five feet long.
• the yarn exiting the furnace was then subjected to a finish treatment in accordance with the prior art and wound onto bobbins made of cardboard in one thousand foot lengths. Twenty-two samples of the yarn were taken at about 1,000 foot intervals.
• the average tensile strength of the resulting fiber was 500,000 psi with a coefficient of variation of 1.3%.
• the average Young's modulus for the resulting fiber was about 41.2 million psi with a coefficient of variation of 2.9%.
• the average density of the fibers was 1.766 Mg per cubic meter with a coefficient of variation of 0.6%.
• the average yield was 3571 feet per pound with a coefficient of variation of 2.1%.
• This carbon yarn was the PAN-based yarn used in the instant process.
• the bobbin had a diameter of 4.5 inches, a length of 7 inches, and no carbon felt was used.
• the loaded bobbin was subjected to a heat treatment in a graphite tube induction furnace.
• the furnace was purged with argon and the temperature was raised at a rate of about 100°C per hour to 2950°C.
• the final temperature was maintained for two hours and then the furnace was allowed to cool to ambient temperature.
• the yarn obtained had excellent physical appearance, no wrinkles or the like, and excellent mechanical properties.
• the average strand properties were: 360 Kpsi tensile strength, 96.9 Mpsi meter.
• a commercially available PAN-based carbon yarn was used in the post heat treatment of the invention.
• The.yarn used had an average strand Young's modulus of about 33 Mpsi and an average tensile strength of about 400 Kpsi.
• the heating schedule and bobbin of Example 2 were used.
• the yarn After the heat treatment, the yarn had an excellent physical appearance and had an average strand Young's modulus of 70 Mpsi and tensile strength of 340 Kpsi.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Inorganic Fibers (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=23677750

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Cited By (3)

Citations (2)

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• 1983
  • 1983-09-23 CA CA000437386A patent/CA1219410A/en not_active Expired
  • 1983-09-26 JP JP17655783A patent/JPS5976926A/ja active Pending
  • 1983-09-26 EP EP83109581A patent/EP0104639A3/de not_active Withdrawn

Patent Citations (2)

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