T H E L E A D E R I N N A N O T U B E T E C H N O L O G Y

L O W E R A D D I T I V E L O A D I N G V S . C O M P E T I T I V EC O N D U C T I V E A D D I T I V E SFIBRIL™ nanotubes exhibit high conductivity

thanks to their graphitic carbon structure,

nanoscale size, and high aspect ratio

(length/diameter (L/D)). Because of this,

they form electrically conductive networks in

insulating materials far more efficiently and at

far lower loading levels than other conducting

additives such as metal fiber, carbon fiber,

nickel-coated graphite, or carbon black.

The graph below illustrates the calculated

relationship between aspect ratio and filler level

required to achieve percolation threshold in

plastics. At the 1-5% loadings of FIBRIL™

nanotubes typically required to achieve electrical

conductivity in plastics,

there is a higher

preservation of the

base resin’s physical,

mechanical, aesthetic,

and processing

properties, such as

toughness, surface

smoothness, and

low viscosity.

M A S T E R B A T C H E S D E S I G N E D F O R M A X I M U M D I S P E R S I O N O F F I B R I L ™ N A N O T U B E SAs-made, nanotubes are so small - about

10-12 nm in diameter and 10-15 µm in length -

that they are relatively shear insensitive. Using

its proprietary technology for dispersing nanotubes

in thermoplastic resins, Hyperion supplies

masterbatches that contain 15-20% nanotubes by

weight, pre-dispersed in a polymer matrix.

FIBRIL™ Nanotube Masterbatch LetdownR e c o m m e n d a t i o n s

T H E L E A D E R I N N A N O T U B E T E C H N O L O G Y

P R O V I D E H I G H S H E A R D U R I N GM A S T E R B A T C H L E T D O W N When letting down masterbatches

containing FIBRIL™ nanotubes,

excellent melt mixing between the

high-viscosity masterbatch and the

letdown (dilution) resin is critical for

application performance. A poor

letdown gives a non-homogeneous

mixture of the high viscosity master-

batch resin mixed with the lower

viscosity letdown resin. This two-phase

mixture can be visualized as small

islands of masterbatch in the larger sea of

the letdown resin. These small islands

of masterbatch will act as a macro-sized

spherical conductive additive instead of

the nano-sized, high aspect ratio nanotubes.

The sample will perform as if the nanotubes

were poorly dispersed, when, in fact, the

dispersion is good, but the mixing is the issue.

Letdown should occur under high shear conditions

(via a twin-screw extruder at a slow feed rate.)

Several papers have been published that can guide

the letdown of Hyperion’s masterbatches to make

high quality compounds.

1] Rheological behavior of multiwalled carbon

nanotube/polycarbonic composites; Petro Potschke,

T.D. Fornes and D.R. Paul, Polymer 43 (2002)

3247-3255

2] Nylon 6 nanocomposites by melt compounding;

J.W. Cho and D.R. Paul, Polymer 2001; 42-1083 –

This paper has the screw design that was used in

the first paper.

The chart above shows viscosities of the master-

batch (15% nanotubes), neat polycarbonate (PC)

compound (0% nanotubes), and 4 nanotube

letdown loadings, 0.5, 1, 2, and 5%, respectively.

At low shear rates, the masterbatch (15% nano-

tubes) is almost four orders of magnitude more

viscous than the pure PC (0% nanotubes) used

in this letdown study. However, the masterbatch

exhibits a strong shear-thinning (non-Newtonian)

effect, whereas the neat PC shows only a small

shear dependence. Thus, at high shear, the melt

viscosities of the masterbatch and the letdown resin

become more similar and there is a higher likeli-

hood of good melt-mixing.

H Y P E R I O N C A T A L Y S I S I N T E R N A T I O N A L , I N C .

38 Smith Place, Cambridge, MA 02138 USAPhone: +1.617.354.9678 Fax: +1.617.354.9691

Web: www.hyperioncatalysis.com

™ FIBRIL is a trademark of Hyperion Catalysis International, Inc. LD 10/04© 2002 Hyperion Catalysis International, Inc. All rights reserved.