Instructions for use
The production of soft, durable, and electrically conductive
polyester multifilament yarns by dye-printing them with carbon
Fugetsu, Bunshi; Akiba, Eiji; Hachiya, Masaaki; Endo,
Citation Carbon, 47(2): 527-530
Typearticle (author version)
Hokkaido University Collection of Scholarly and Academic Papers : HUSCAP
The production of soft, durable, and electrically conductive polyester
multifilament yarns by dye-printing them with carbon nanotubes
Bunshi Fugetsu1*, Eiji Akiba2, Masaaki Hachiya3, Morinobu Endo 4
1 Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810,
2 Kurary Living Co., LTD., Umeda kita-ku, Osaka 530-8611, Japan
3 Chakyu Dyeing Co., LTD., Ichinomiya-City, Aichi 494-0001, Japan
4 Faculty of Engineering, Shinshu University, 4-17-1, Wakasato, Nagano-shi, 380-8553,
*Corresponding author: Graduate School of Environmental Science, Hokkaido University,
Sapporo 060-0810, Japan. Fax: +81 11 706 2272. Email address: email@example.com (B.
Continuous yarns and/or fibers composed of carbon nanotubes (CNTs) are highly
attractive due to their intrinsic ability to form a variety of macroscopic objects by simply
knitting and/or weaving of the yarns/fibers. The production of continuous yarns of pure CNTs
has been accomplished by “dry-spinning”, the mechanical process of spinning either the
single-walled CNTs directly from a CVD (chemical vapor deposition) gaseous reaction zone
[1, 2] or with the multi-walled CNTs previously grown as a vertically oriented CNT forest [3,
4] . In contrast, “wet-spinning”, the spinning of a “super-acid (100 + %sulfuric acid)
suspension”  of the single-walled CNTs, produced purely CNT-based continuous fibers.
The pure CNT-based yarns and/or fibers retained the advantageous properties of the
individual nanotubes, such as the high electrical and thermal conductivities. However, the
preparation of industrial quantities of the single-walled CNTs or the multi-walled CNT
forests, the precursors for making the CNT-based yarns/fibers, is presently impractical.
Continuous fibers containing a few wt % of CNTs, obtained, for example, by
incorporating the single-walled CNTs into PVA polymers [6, 7], have shown excellent fiber
properties, but electrical and thermal conductivities were low because of limitations on the
contents of CNTs. Despite the production of continuous fibers with up to 60 wt% CNT
content , the development of the CNT-based continuous yarns/fibers having high industrial
applicability remains a challenging issue.
In this study, we used CNTs as “dyestuffs” for producing CNT-based continuous yarns by
directly dye-printing of polyester multifilament continuous yarns. To our best knowledge,
this is the first use CNTs for direct dye-printing of continuous multifilament yarns. CNTs,
even the multi-walled types, are characterized by extremely large aspect ratios, because of
their nanometer sized diameters and their micrometer (~ few hundred micrometers) sized
length. This so-called one-dimensional morphology of CNTs results in stronger adhesion
properties (in comparison with the so-called zero-dimensional materials, such as carbon
blacks), suggesting a possible application for directly employing CNTs as dyestuffs for
dyeing of fibers, yarns, and textiles. Such application, as demonstrated in this study, was
achieved by using CNTs at molecular levels (or tubular levels) for dispersions as dyestuffs.
Typical CVD products of multi-walled CNTs (Baytubes® C 150P), received as powders, have
been used for preparing the CNT-based dyestuffs. Briefly, 300 g of the CNT powders were
introduced into 10 L of an aqueous solution containing 40 g of 3-(N,N-
dimethylmyristylammonio)-propanesulfonate and 30 g of polyoxyethylene lauryl ether
sulfonate, to prepare the raw CNT-suspension. This suspension was then used as the
precursor for preparing the CNT-based dyestuffs by dispersing the CNT-aggregates at the
molecular level using a continuously operating bead-mill system. Three essential strategies
are involved in the preparation of the CNTs-based dyestuffs. i) Wetting of CNTs: air and
moisture were displaced from the surfaces of the CNT-aggregates by replacing them with the
dispersants. This objective was accomplished in the process of preparing the raw CNT-
suspensions and the best wetting efficiencies were obtained by using a combination of 3-
(N,N-dimethylmyristylammonio)-propanesulfonate, a zwitterionic type of surfactants and
polyoxyethylene lauryl ether sulfonate, an anionic type of surfactant, as the dispersants. ii)
Grinding of the “wetted CNT-aggregates”: CNT-aggregates, after being well wetted by the
blended zwitterionic/anionic dispersants, were easily dispersed into individual tubes by very
mild mechanical shear forces through the use of a continuously operating bead-mill system.
(Hereafter, CNT-aggregates, after being dispersed into individual tubes, will be referred as
the “molecular level (or tubular level) of dispersion”.) Particle size distributions, as
measured using a dynamic light scattering size distribution analyzer (Fig. 1), showed that
95% of the overall particles exhibited mean diameters smaller than 270 nm, suggesting that
most of the dispersion of CNTs in the CNT-based dyestuffs occurred at the molecular level.
iii) Addition of a small amount of polymers into the dyestuffs: the electric resistivity of the
CNT-dyed yarns can be precisely controlled at certain levels by controlling the ratios of
carbon nanotubes to polymers in the dyestuffs. In this study, anionic polyurethanes, received
as emulsions, were used as the typical polymers. The CNT-based dyestuffs have a life time
(the mean diameter of CNTs monitored using the dynamic light scattering size distribution
analyzer was used as the essential indicator) longer than 18 months.
Commercially available polyester multifilament yarns (20 dtex/24 filament) were dyed
directly through a dye-printing approach (Fig. 2). Briefly, the polyester multifilament yarns
were passed through a dye-bath containing the CNT-based dyestuffs. Temperature of the
dye-bath was maintained at 40 ˚C. A micro-wave vibration system was used to vibrate the
polyester multifilament yarns, so that each filament of the multifilament yarns was dyed
thoroughly by the CNT-based dyestuffs. The CNT-dyed multifilament yarns were further
cured at 170 ˚C , which was about 100 ˚C higher than the glass transition temperature (Tg, 69
˚C) of the polyester multifilament yarns, for about 30 seconds, by passing the yarns through a
cure oven. The resulting CNT-dyed multifilament yarns were black yet bright (Fig. 3). SEM
images of the CNT-dyed multifilament yarns (Fig. 4) revealed a CNT-skin, with the CNTs
arranged into continuously interconnected networks over the surfaces of the yarns. Each
filament was coated by a continuous CNT-skin, with a coating thickness of approximately
400 nm. The outer skin, established by the continuously interconnected CNT-networks,
functions as an electrically conductive layer (ECL) and the value of its electrical resistivity
ranged from 103 to 109 ohm/cm, as verified by the contents of CNTs in the ECL.
Electrical resistivity measurements, obtained using a two-electrode resistance measuring
meter (Table 1), demonstrated a highly uniform resistivity along the yarn direction.
Furthermore, the CNT-dyed multifilament yarns have shown excellent stable electric
resistivity, even under elongation. The yarns broke at an elongation ratio of approximately
The 103 ohms/cm level CNT-dyed multifilament yarns were woven into fabric (20 m
× 0.6 m) by using the CNT-dyed yarns as the wefts (horizontal yarns) and the regular
polyester textured yarn for the warps (vertical yarns). This orthogonally blended fabric was
then cut into pieces of smaller size (20 cm × 30 cm) to evaluate their thermoelectric behaviors
by gripping both ends of the CNT-dyed yarns of the fabric samples between two copper
plates (electrodes). Typical plots of the time-temperature dependence, over the applied
voltage range of 5 - 40 V (Fig. 5) illustrated that the orthogonally blended fabric functioned
as an electrical heater when the applied voltages exceeded 20 volts.
The CNT-dyed multifilament yarns showed excellent electrical conductivity even
after being water-washed. For example, for the 105 ohm/cm level CNT-dyed multifilament
yarns, the electrical resistivity was 2.52 × 105 ohm/cm prior to washing and 8.23 × 105
ohm/cm (the average value of twenty measurements) after 20 min of washing in tap-water at
75 ˚C. This high tolerance for washing indicated that the CNT-dyed multifilament yarns are
useful for anti-static uniforms.
CNT-dyed multifilament yarns with an electrical resistivity level of 109 ohm/cm have
been used for establishing brushes for the photocopying machines; excellent static-control
performance was obtained.
In conclusion, polyester multifilament yarns with each filament being suffused with a
continuous CNT-skin can be produced in industrial quantities by using CNTs at the
molecular level of dispersions as dyestuffs. This thin CNT-skin functions as an electrically
conductive layer with excellent adhesion, toughness, and durability. The direct use of CNTs
in dyeing opens new applications of nanotechnologies in yarn/textile productions.
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Table 1 Data on measuring of electric resistivity (ohm/cm) of twenty randomly chosen
samples (10 cm of each sample) of the 103 ohm/cm level CNT-dyed multifilament yarns.
Figures and Captions
Fig. 1. Dynamic light scattering size distribution of CNTs in the CNT-based dyestuffs.
Fig.2. Schematic illustration of the dye-printing system for mass production of the CNT-
dyed multifilament polyester yarns.
Vibration 200 Hz
Dyeing bath (40 ˚C)
Curing oven (170 ˚C)
Cumulative Percent (%)
Size Percent (%)
Fig. 3. Photos of the polyester multifilament yarns before (left-photo) and after (right-photo)
being dye-printed with the CNT-based dyestuffs. The yarns were about 10,000 meters long.
Fig. 4. SEM images of the CNT-dyed multifilament yarns. CNTs have established an
electrically conductive layer with the individual carbon nanotubes arranged as a continuously
interconnected network over each filament of the yarns.
Ultimate Timperature (
Fig. 5. Temperature-time dependence observed for the fabric samples obtained using CNT-
dyed 103 ohms/cm level multifilament yarns as the wefts and regular polyester textured yarn
for the warps. The applied voltages were 5, 10, 15, 20, 30, and 40 volts, respectively (from
the bottom curve to the top curve).