About thirty years ago, carbon fiber was heralded as the new wonder material. However, carbon fiber was certainly not new, although it has since proved to be an extremely useful reinforcement material. Thomas Alva Edison, who made this first sound recordings in 1877, turned his attentions to the incandescent electric lamp and in 1880, patented the use of carbon fiber as filament material for his electric lamp. To achieve his aim, in a period of some 15 months, Ddison and his associates in the laboratory at Menle Park, New Jersey, USA built a new type of generator, found a suitable element material and incorporated it in glass globe operating under a high vacuum.
To find a satisfactory element material, Edison was reputed to have tried more than 1600 kinds of materials. Until eventually, Edison hit on the idea of carbonizing a loop of ordinary cotton thread, which glowed in a vacuum for more than half of that eventful day of 21 October, 1879. This filament as later replaced by carbonized “Bristol cardboard” that burned for 170 hours. The incandescent electric lamp had arrived.
The carbon filament were, at a later date, developed by Edison by dissolving cellulosic material like natural cellulose or cotton in a solvent, such as zinc chloride, to give a dope which could be extruded through a die into a bath containing a liquid (spin bath), which would regenerate the cellulose in the form of a thread or filament. The filament material was cut into lengths and carbonized in the absence of air in a heated gas furnace. The material was inherently weak and subsequent improvements were made by cracking a layer of pyrolytic carbon onto the surface. This was carried out by placing the filament in the vapor of a hydrocarbon, such as benzene, and pressing an electric current to cause the hydrocarbon to decompose and crack onto the surface of the filaments with resultant improved properties.
Edison also took out a UK patent dated 10 November 1879, which preceded, by some 12 months, a UK provisional patent taken out by J.W.Swann for lamp filaments made of carbon. These patents of Edison and Swann are the first recorded UK patents dealing with carbon fiber. In 1889, Hughes and Chambers patented a process to produce carbon filaments from a mixture of methane and hydrogen pyrolyzed in an iron crucible yielding hair-like carbon filaments, but the process was uneconomic. A further improvement as made in 1909 by Whitney, who took a product comprising an impure carbon core surrounded by an outer layer of pyrolytic carbon and heated it in a carbon tube electric furnace to temperature from 2300C-3700C reputedly, converting the outer layer of the pyrolytic carbon into a more graphitic form with improved electrical properties, but the fiber remained weak and very brittle. To overcome the brittleness, the filaments were shaped into the intended element construction before the final graphitizing procedure. The use of carbon filaments for electric lamps was relatively short-lived, being replaced circa 1910 by the more robust metallic wires such as tungsten.