Plastics News Europe - June 2019 - 12

automotive plastics

From magnesium to
thermoplastic
With automobile makers under heavy
pressure to reduce emissions, every
kilogram of vehicle weight counts.
Innovations from materials manufacturers
are opening the door for further
lightweighting. By Karen Laird

eplacing metal with plastics has
long been a key strategy for vehicle manufacturers to shed
weight. Moreover, automobile designers have embraced the design
freedom and the possibility for parts
consolidation which plastics can offer.
Lighting and car interiors, in particular, have benefitted from new developments in thermoplastic materials,
which today feature excellent haptics
and aesthetic properties, although
according to Norwin van Riel, technology leader Automotive TS&D at
Trinseo, the use of plastics is also 'expanding to the exterior'. "Big steps
are being taken in semi-structural and
under-the-hood applications," he
said. He pointed to Trinseo's collaboration with Renault where, using long
glass fibre-filled PP, the car maker successfully reduced the weight of the
tailgate of its Clio model by 15%.
"Front-end modules, door modules -
these are all becoming possible."

Norwin van Riel:
"Big steps are
being taken in
semi-structural
and under-thehood applications"

Speaking with Plastics News Europe at the recent PIAE - Plastics in
Automotive Engineering - event in
Mannheim, Germany, van Riel emphasised the importance, as a materials supplier, of working closely with
the customer on metal replacement
applications. "Replacing materials in
existing applications is very challenging," he said. "It is extremely important to be involved from the very

BMW used the LGF ABS alloy for an instrument carrier on
the next-generation 2019 3 series.

beginning, in order that the expertise we have about materials is incorporated into the development of the
new component."
At PIAE, Trinseo presented the results of one such collaboration, 'a development with long glass fibre not
on the market today," said Frank
Schumann, global marketing manager automotive performance plastics.

Material development
and design
In the past, car makers looking for
stable and reliable materials for
semi-structural and structural components opted to use steel, magnesium,
or aluminium, as obtaining the required stiffness and stability was difficult when using thermoplastics.
"These always need to be reinforced
with glass fibre," said van Riel.
Hence when Tier One supplier
Dräxlmaier needed an innovative
material solution for the instrument
carrier in the new BMW 3 series,
Trinseo knew that a reinforced thermoplastic was the answer. "The
original part was made from magnesium," said Schumann. "We needed
a solution which would offer the
same degree of dimensional stability
and narrow tolerances. It was not an
easy proposition."
Working closely with Dräxlmaier,
the decision was made to use a
glass-reinforced ABS material. "ABS
solved problems that other materials
presented," said van Riel. "The water
uptake is less, compared to PA, and,
because it's an amorphous polymer,
there is less warpage than with PP."
He added: "PP is cheaper. But ABS offers more stiffness at the same glass

fibre content. And there is no need to
use PA in the car interior - to do so
would be overengineering the part."
However, ABS presented a number
of other challenges. "The development was not straightforward," van
Riel added. "We reformulated the material to ensure the fibres would disperse more easily during processing.
There were adhesion and wetting issues to be overcome, as well. In the
engineering phase, we provided support in the form of price recommendations and optimised the production
process, carrying out simulations to
finetune the mould design, using finite element analysis to model the design and gating of the tool."

Successful replacement
Ultimately, the LGF ABS composite
developed offered an outstanding
lightweight alternative for the original magnesium from which the part
was made. "We achieved a 30%
weight savings with the new material, improved the process and produced a high dimensionally stable
part," said Schumann.
As a structural polymer, the new
composite offers not only lower
weight than magnesium, but also low
VOC and low odour properties, and
enables faster production cycle times.
"The length of the glass fibre used
impacts the mechanical performance
and appearance," van Riel explained.
In combination with a grained surface,
the appearance is very acceptable, he
added. "It is not an aesthetic part - it
is not visible," he said. "That is the
next challenge we are working on: developing aesthetically pleasing visible
components."

june 2019

Plastics News Europe - June 2019

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