Chemical Engineering August 2021 - 16

FIGURE 2. The possibility of battery fires has made flame retardance a critical property
for vehicle safety in EVs
has pushed plastics makers to view
flame retardance as a critical feature
for EV components, " says Sandra
Reemers, vice president of R&D at
Evonik High Performance Polymers.
BASF's Korson adds, " Many of the
applications for performance plastics
appear in the batteries, where thermal
runaway protection is key. "
Thermal management of the battery
and improved flame-retardant
properties are partly related to higher
voltages observed in EVs. Bert Havenith,
from DSM, says, the voltages
experienced in modern electric vehicles
are orders of magnitude higher
than those seen in conventional vehicles,
so there is a huge need for
improved electrical properties, such
as higher dielectric strength, higher
comparative tracking index (CTI),
a measure of the amount of voltage
an insulator can withstand with
50 drops of water without tracking
(electrical breakdown) values, as well
as better flame-retardant properties.
SABIC's Nagwanshi says " We
have developed and tailored specific
resins from our polymer portfolio that
we have modeled using computeraided
engineering (CAE) tools to
ensure they comply with safety requirements
and regulations, whether
these apply to a crash scenario or
some sort of system failure leading
to a fire in the battery pack. "
China's new GB 38031-2020 standard
requires a battery cell that has
caught fire to delay propagating to
other cells or battery modules for up
to five minutes so occupants have
time to exit the vehicle, Nagwanshi
says, and " SABIC's polymer mate16
rials
can
be key
in meeting
this
r equir e -
ment and
upcom -
ing safety
regulations
in other
countries. "
SABIC
has also
developed
a process
for adding
flame
retardancy
to resins. " The process features exceptional
dispersion of the additive
within the resin, " says SABIC's Nagwanshi,
" and that ensures uniform
flame-retardant protection
the entire part. "
across
An example of this resin technology
for EV battery pack applications
is SABIC's introduction of non-halogenated
flame retardant Stamax
resins for various electrification
components. Because of its unique
character, Stamax FR resin delivers
a higher level of fire shielding protection,
SABIC says. The exceptional
dispersion and distribution of the FR
additive within the polymer matrix,
even at high loadings, helps maintain
structural integrity of EV battery
components. " This is not possible
with competitive technologies,
which would require halogenated FR
chemistry to produce the same results, "
Nagwanshi says.
Temperature resistance is also a
key property for new grades of SABIC's
Noryl GTX resin family. SABIC's
Parikh says, " The expanded temperature
range of Notyl GTX resin has
the potential to provide value to the
OEMs at both ends of the temperature
spectrum. The high-temperature
resistance of the material allows for
plastic components to be assembled
to the frame of a vehicle prior to eCoat
or along with the body of a vehicle for
on-line painting. The low-temperature
ductile performance of the material
enables more predictable and repeatable
energy absorption at low-temperature
impacts. This predictability
can help engineers optimize their
designs and contribute to improved
vehicle and occupant safety. "
SABIC's Parikh continues, " In addition
to temperature and impact resistance,
our non-halogenated Noryl
resins
offers
flame
retardancy for
battery covers, modules, electrical
enclosure and other EV battery components.
Noryl GTX resin can also be
used for energy absorbers to aid in
crash protection. "
Flame retardancy in plastics also
has implications for rapid charging,
which is a key aspect of successful
electromobility. New standards allow
for charging up to 350 kW, which reduces
charging time to minutes, but
it also requires different materials for
the equipment. In these applications,
Evonik's flame-resistant Vestamid
PA12 and Vestakeep polyether ether
ketone (PEEK) are suitable for use
as insulation for cables or busbars in
the battery module or electric motor,
and as plug components for highvoltage
charging.
Sustainability
" The transition toward a circular
economy for industrial goods will
require the automotive industry and
its suppliers to rethink the ways that
vehicles and their materials are designed,
constructed, used, and handled
at end of life, " says ACC.
Dow's Mark Jablonka agrees that
the final big topic is circularity. " How
do you make sure, at end of life, that
your materials are not ending up in
landfill? " he says. Designing for circularity
is a tough challenge for the
industry overall, and a priority for
Dow. " We want to make sure all of
the materials on the vehicle end up
being recycled, either mechanically,
or by using advanced recycling techniques
like pyrolysis and gasification
with the lowest carbon footprint. "
DSM has also focused heavily on
sustainability, including reducing carbon
footprints of products and deriving
monomers from recycled waste or
from bio-sources. DSM has pledged
to offer bio-based or recycled versions
of all of its products by 2030. ■
Scott Jenkins
Editor's note: Additional comments regarding polymer
use in EVs can be found in an extended version of this
article at www.chemengonline.com.
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Chemical Engineering August 2021

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