ENSACO® Conductive Carbon Black for polymer ... - Timcal Graphite

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Thermally
conductive polymers
NThe ability of a material to conduct heat is
known as its thermal conductivity. Thermal
conductivity itself is nothing else than transportation
of thermal energy from high to low
temperature regions. Thermal energy within
a crystalline solid is conducted by electrons
and/or discrete vibrational energy packets
(phonons*). Each effect, phonons and movement
of free electrons, contributes to the rate
at which thermal energy moves. Generally,
either free electrons or phonons predominate
in the system.
*Phonons
In the crystalline structures of a solid material,
atoms excited into higher vibrational frequency
impart vibrations into adjacent
atoms via atomic bonds. This coupling creates
waves which travel through the lattice
structure of a material. In solid materials
these lattice waves, or phonons, travel at the
velocity of sound. During thermal conduction
it is these waves which aid in the transport
of energy.
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Typical applications for TIMREX® Graphite and Coke
What is
thermal conductivity?
Scrap
PC 40 12
Typical data of thermal conductivity of graphite powders
pressed to density ≈ 2.2 g/cm 3 , 25°C
Thermal conductivity
of graphite
N The thermal conductivity in graphite is
generally dominated by phonons, and limited
by the crystallite size. In addition, due to
its particular structure, thermal conductivity
is different in the different directions of the
crystal. It is highly conducting along its layers
(ab direction) and not so well perpendicular
to the layers (c direction) because their is no
bonding between the layers. The thermal
conductivity of a perfect graphite crystal is
~3000 W/(m.K) in the ab direction and ~6
W/(m.K) in the c direction. NThe table
below shows the thermal conductivities of
TIMREX ® Graphite measured on pure
graphite compacts (obtained by Hipped
Samples; HIP 350 MPa, 1900°C). Thermally
conductive plastics can replace most metals
(i.e. aluminium and copper), ceramics, and
conventional plastics in heat-sensitive applications.
Thermal Conductivity W/(m.K)
20.00
15.00
10.00
5.00
Thermally
conductive polymers
Thermally conductive polymers are able to
evenly distribute heat generated internally
from a device and eliminate “hot spots.”
Possible applications for thermally conductive
plastics include heatsinks, heat exchangers,
appliance temperature sensors and many
other industrial applications. Also thermally
conductive elastomers can be found in a wide
variety of industrial applications such as gaskets,
vibration dampening, interface materials,
and heat sinks.
NVirgin polymers can be considered thermal
insulators having a thermal conductivity of
approximately 0.2 W/(m.K). By adding
TIMREX ® Graphite a final value up to 15-20
W/(m.K) can be achieved (as it is shown in
the following graph in which different types
of graphite powder were added to a PP
matrix) which represents an increase of 75 to
100 times compared to the unfilled polymer.
Thermal conductivity of graphite (in plane) - PP compounds
BNB 90
KS grades
10% KS+BNB90
0.00
0 20 40 60 80 100
Loading (% wt)