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.
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