24 February 2010, Leverkusen – Bayer MaterialScience has
announced that thanks to a combination of two new dispersion technologies, aqueous
suspensions of its Baytubes carbon nanotubes (CNTs) can now be produced which
contain single tubes which show high electrical and thermal conductivity. According
to the company, multifilament yarns coated with such CNT dispersions can be
woven to efficient fabric heaters which have already performed well in
preventing the water in water storage tanks of Japan’s JR Hokkaido ‘Ryuhyo-Norokko’
train from freezing.
Bayer MaterialScience says that the aqueous suspensions of
carbon nanotubes (CNTs) containing individual tubes offer interesting
perspectives for a number of new applications which depend on a high electrical
or thermal conductivity, respectively. In particular, this applies to
multifilament yarns coated with such CNT dispersions and an interesting
development using multifilament yarns is a new fabric heater made by weaving
CNTEC conductive yarns from Kuraray Living Co., Ltd. The fabric is said to generate
heat homogeneously all over the surface because of its outstanding conductivity
and is said to be the first commercial use of Baytubes CNTs from Bayer MaterialScience
in the Japanese market.
Bayer MaterialScience says the fabric heater is lightweight,
thin and compact and shows a long-lasting bending resistance. The company says
it can be used for instance for car seats, household electrical appliances, for
heating of clothes and as an anti-freezing material.
Tests carried out on the Ryuhyo-Norokko, a train running
through Japan’s cold north island, where the temperature drops to around -20 °C
in wintertime, are said to have prevented water in the tanks from freezing.
Normally the train uses only potbelly stoves for heating. According to JR
Hokkaido Railway Company the fabric heater performed well in preventing the
water from freezing and a seat heating application using the fabric is still on
trial on another JR Hokkaido train line. It is anticipated that the aqueous
dispersions might also be suitable for the compounding of various kinds of
materials, Bayer MaterialScience says.
In the course of their production CNTs usually form large
and stable agglomerates where the tubes are tightly entangled to each other.
Dispersing such agglomerates into individual tubes which show a maximum of
electrical and thermal conductivity has so far been a challenge, says Bayer
MaterialScience. Thanks to a new dispersion technology using a zwitterionic
surfactant developed and patented by Prof. Dr. Bunshi Fugetsu from Hokkaido
University it is now possible to produce stable aqueous suspensions containing
CNTs at a mono-dispersed (tubular) level in industrial quantities, the company
says.
To achieve this, a unique method for non-destructive
dispersion of CNT agglomerates into individual tubes developed by the Inoac
Technical Center Co., Ltd. is applied as well. The products are said to show a
stable and homogeneous conductivity and a durability that easily covers the
service life that is required for industrial products. Through a combination of
both technologies it is possible to disentangle the agglomerates of Baytubes in
an efficient and stable way.
