Carbon black under the microscope | Forum

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freemexy Jul 30 '19
We know the term well, but there is much more to carbon black than meets the eye, which is why we are taking the opportunity to look a little more closely at the darkest colour that we know so well, and its history.Carbon black masterbatch

To begin, carbon black is so-named because it is derived from naturally-occurring fuel such as wood or petrochemicals and in plastics, it is produced through the incomplete combustion of a petroleum feedstock. It is, as DT Norman of the Witco Corporation in Houston puts in his white paper Rubber Grade Carbon Blacks, ‘an elemental carbon in the form of extremely fine particles having an amorphous structure’, with the features of the substance being controlled in production by partially combusting oil or gas.

Carbon black has a varied and long history. The earliest incarnation of carbon black, soot, can be traced back as a pigment to the ancient Egyptian and Chinese civilisations where it was utilised as an ink. Carbon black as we know it today, became more widely produced for industry and the decorative arts in the 19th century, when in the 1860s a smoky natural gas flame was used in the combustion process, with the carbon black deposits being moved into cool revolving drums. The resulting powder absorbed the light due to its fineness and it proved a stable pigment that was not affected by exposure to the light or the atmosphere. At this point, the term carbon black stuck, when previously the pigment had been referred to as lampblack due to a chimney-like production process.

This production system evolved in the mid-20th century when the oil furnace method was adopted.The oil furnace method has prevailed since 1947, utilising aromatic hydrocarbon oil as the raw material for incomplete combustion.

Asahi Carbon reveals that its oil furnace method elevates the feedstock’s combustion temperature to 1,000 degrees, with the entire process taking two seconds at most. The raw material is held in a separate chamber to the 1,300 degree furnace, and water is utilised to stop the reaction and control the temperature.

This is a slightly more sophisticated system than the lampblack method, which has been used since ancient times, burning the raw material and piping its emissions in an ‘L’ shaped chamber which is cooled with water where the substance gathers like soot in a chimney.