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.
Thanks to the combination of two new dispersion technologies aqueous suspensions of Baytubes carbon nanotubes (CNTs) can be produced which contain single tubes and thus show a high electrical and thermal conductivity. Multifilament yarns coated with such CNT dispersions can be woven to efficient fabric heaters. Such heaters already performed well in preventing the water in water storage tanks of JR Hokkaido's "Ryuhyo-Norokko" train from freezing.
An interesting development using multifilament yarns is a new fabric heater made by weaving CNTEC® conductive yarns from Kuraray Living Co., Ltd. This fabric generates heat homogeneously all over the surface because of its outstanding conductivity and is supposed to be the first commercial use of Baytubes® CNTs from Bayer MaterialScience in the Japanese market.
The fabric heater is lightweight and thin, compact and shows a long-lasting bending resistance. It can be used for instance for car seats, household electrical appliances, for heating of clothes and as an anti-freezing material. Tests revealed that it may for example be installed in the water storage tank of JR Hokkaido's "Ryuhyo-Norokko" train. Inside this train the temperature drops to around -20 °C in wintertime, because so far no heating devices other than potbelly stoves are available. According to JR Hokkaido railway company the fabric heater performed well in preventing the water from freezing. A seat heating application of the fabric heater is still on trial on another JR Hokkaido train line. It is anticipated that the aqueous dispersions might as well be suitable for the compounding of various kinds of materials.
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. 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. 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 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.
Source: Bayer