Carbon fiber Carbon fibers are produced by using heat to chemically change rayon or acrylic fibers. Carbonization occurs at temperatures of 1000^0 C to 2500^0 C in an inert atmosphere. Carbon fibers are converted to graphite at temperatures above 2500^0 C. Carbon and graphite fibers can also be made from pitch, a residual petroleum product. Products that use carbon fibers include heat-shielding materials, aircraft fuselages and wings, spacecraft structures, and sports equipment. You can golf, ride, sail, tennis, drive, cycle, fish, decorate or even fly Carbon Fiber! Carbon fibers are derived from one of two precursor materials Pitch and Pan.
Pitch is based carbon fibers have lower mechanical properties and are therefore rarely used in critical structural applications. Pan based carbon fibers are under continual development and are used in composites to make materials of great strength and lightness. The raw material of Pan, acrylonitrile, is a product of the chemical industry and can be manufactured as follows: Acrylonitrile is used as a raw material in acrylic fibers, ABS resin, AS resin, synthetic rubber, acrylamide and other materials. Global production capacity is 4. 67 million tons, approximately 60% of which is consumed for acrylic fibers.
In the early manufacturing processes acetylene and hydrogen cyanide were used as a raw material, whereas today nearly all AN is manufactured using what is called the Sohio process, whereby an reaction are applied from inexpensive propylene and ammonia. Technological advances, particularly surrounding research into improved catalysts for the Sohio process, are proceeding, promoted by a concern for energy conservation and lessening the environmental loading. The research aims include improved productivity, reduced byproducts, and lesser wastewater and waste gas. The Sohio process was perfected in 1960 by The Standard Oil Co. of Ohio, owing to the development of an epoch-making catalyst that synthesizes AN in a single-stage reaction using propylene and ammonia. The reaction took place using the fluid-bed od.
The P-Mo-Bi group is used as the catalyst and favorable fluidized conditions are maintained by adjusting the physical properties of the catalyst. The reaction gas contains not only AN, but also, hydrogen cyanide and other byproduct gasses, so AN products are obtained by having the reaction gas absorbed into water, then using evaporation separation. The Sohio process was epoch-making at the time it was developed, but improvements have been made in response to the following conditions: The AN yield of approximately 60% was not very high; The process circulated and used large amounts of water, requiring a lot of energy. Approximately 1. 5 tons to 2 tons of wastewater was generated for every ton of AN produced.
Treatment technology for the waste gas was incomplete. The conversion of Pan to carbon fibers is normally made in 4 continuous stages Oxidation, Carbonization (Graphitization), Surface treatment, and Sizing. Oxidation involves heating the fibers to around 300 deg C in air. This evolves hydrogen from the fibers and adds less volatile oxygen. The polymer changes from a ladder to a stable ring structure and the fiber changes color from white though brown to black.
In this picture you see the fiber changing color. The white Pan strands at the bottom pass through the air heated oven and begin to darken Quite quickly they turn to black and carbon fiber is like the Ford T, As Henry said 'Its any color you want, as long as it's black " Photo courtesy of Akzo Nobel The resulting material is a textile fiber which is fireproof, some companies actually sell this as an end product for example SGL Technic, under the trade name Pan ox. A summary of typical properties of the various grades of carbon fibers is given by To ray, although the units of are imperial sizing is a neutral finishing agent to protect the fibers during further processing () and to act as an interface to the resin system of the composite. Carbon fibers are used primarily in composites, these are structures containing two or more components, in the case of fiber reinforced composites this is the fiber and a resin.
A composite containing two types of fiber, carbon and glass, is known as a hybrid composite structure. The origins of textile reinforced composites are linked to the development of glass fibers, which commenced in 1938 by the Owens Corning Fiberglass Corporation. Original large scale applications included air filtration, thermal and electrical insulation and the reinforcement of plastics. As the technology of textile reinforced composites expanded, a growing demand from the aerospace industry for composite materials with superior properties emerged. In particular, materials with (1) higher specific strength, (2) higher specific moduli and (3) low density were required. Other desirable properties are good fatigue resistance, and dimensional stability.
Carbon fibers were developed to meet this demand. Carbon fiber is a high strength, high stiffness synthetic fiber that is used in a variety of structural and electrical applications. Carbon fiber is manufactured by heating, oxidizing, and carbonizing poly acrylonitrile polymer fibers. The resulting carbon fibers are typically molded into high strength composite materials for structural applications or are used in their pure form for electrical and friction applications. Carbon fiber composites have amazing structural properties. Carbon fiber composites are ten times stronger than steel, yet are still five times lighter.
In comparison to aluminum, carbon fiber composites are eight times stronger, two times stiffer, yet still 1. 5 times lighter. Carbon fiber composites have superior fatigue properties to all known metallic structures, and when coupled with the proper resins, carbon fiber composites are one of the most corrosion resistant materials available. In electrical applications, carbon fibers can be used to tailor the electrical properties of injection molding compounds, paints, and adhesives. The resulting products provide the benefits of plastics with the conductivity and electrical shielding capabilities of metals. When used in adhesives, the electrical conductivity of carbon can be used to enhance cure times in RF environments by an order of magnitude.
The electrical properties of carbon fiber and the ability to configure the material into a semi permeable membrane with defined mass transport properties make carbon an ideal choice for Next Generation fuel cell engines. In friction applications, carbon fiber is used to create materials that can withstand extremely high temperature coupled with brutal abrasive wear. Small amounts of carbon can even be used to control the explosive burn of airbag propellants, resulting in safer deployment of airbags in automotive applications. The applications for the amazing properties of carbon fiber continue to grow every day. In its most pure form, Polyacrylonitrile is used as the precursor polymer fiber to make carbon fiber. PAN intended for use to make Carbon fiber are high purity and contain high molecular weight molecules (i.
e. long chains Copolymers containing mostly are also used as fibers to make knitted clothing, like socks and sweaters, as well as outdoor products like tents. If the label of some piece of clothing says 'acrylic', than it's made out of a blended copolymer of poly acrylonitrile. PAN intended for common use in textiles is usually lower purity and contains shorter polymer chains (low molecular weight) Polyacrylonitrile is a vinyl polymer, and a derivative of the family of polymers. It is made from the monomer acrylonitrile by free radical vinyl polymerization. Carbon fiber is made by heating, oxidizing and carbonizing poly acrylonitrile polymer fibers.
First, the PAN fiber is heated in air. The heat causes the cyan o sites within the PAN polymer chain to form repeat cyclic units, of. This polymer is also known as the ladder polymer. Continuing the heating process in air, oxidation occurs. This process causes the carbon atoms to kick off their hydrogen atoms, and the rings become aromatic. The modified PAN polymer is now a series of fused pyridine-pyridine rings.
The heating process is continued in the absence of air. The heating process is now called carbonization, where the heat is raised to above 1300 oC. Adjacent polymer chains are joined together to give us a ribbon-like fused ring polymer. The newly formed ribbons continue to condense together to form the lamellar, basal plane structure of nearly pure carbon.
The polymer has nitrogen atoms along the edges of the basal planes and which are expelled as Nitrogen gas. These basal planes will stack to form microcrystalline structures. The size and orientation of these crystallites will alter the properties of the final car.