JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 25

process has an influence on the property
profile at various reinforcing fibre amounts
(30% and 40% by weight, Fibre 1).
In the end, Process 1 proved to show the
best overall performance for both reinforcement levels, and the combination of Fibre 1
together with Coupling 1 and Process 1 offered the highest property profile that could
be achieved (Fig. 3). These lab tests were
confirmed on an industrial scale.
With successful tests completed, the resulting solution was named reSound™ NF.
reSound is the brand name used by PolyOne
to signify a solution contains at least 30%
renewable-sourced materials.
The properties of the reSound NF solution
obtained at an industrial scale combining
the different technologies (fibre, coupling,

Fig. 3: Performance comparison between the two
processing methods on Fibre 1 at 40%

and compounding) are very similar to
the original target, with the advantage of a
density reduction of at least 5% versus short
glass fibre alternatives (Fig. 4).

Processing studies
prove potential
Injection moulding of tensile bars proved
the mechanical performance and easy
processability of reSound NF compounds.
Like most natural fibre-reinforced thermoplastics, reSound NF solutions should be
processed at temperatures below 200°C in
order to maintain the integrity of the fibres.
Using low temperatures also offers potential
energy savings and short cooling times, for
efficient yield at manufacturer facilities.
Further testing revealed that reSound NF
solutions are compatible with and show
robust property retention when moulded
on machinery outfitted with the MuCell®
foaming process from Trexel. The retention
is as robust as PP-SGF for tensile properties,
even more robust for flexural properties, and
clearly more stable for impact properties.
So the use of reSound NF formulations
without foaming offers a lightweighting
opportunity for automotive Tier suppliers
not yet equipped with MuCell technology,
while the combination of reSound NF
and MuCell foaming technologies opens
additional possibilities for OEMs and Tiers
to further reduce their part weight while
keeping a high level of performance.

Finally, tests were also conducted to determine the influence of production scrap
- such as moulding sprues reintroduced
into the process - on the performance of
reSound NF solutions. Tensile bars were
moulded, reground, and moulded again
with the regrind material only. This was
repeated three times.
The results showed a very stable performance towards regrinding for reSound NF
formulations versus PP-SGF. It seems the
limitation in the on-line re-introduction of
reground PP-SGF into the manufacturing
process does not apply to reSound NF compounds, which offer a potential "no scrap"
process for users.

Large part moulding
PolyOne and Fraunhofer ICT (Germany)
selected two representative tools in order to
perform both processing and mechanical
tests. One of these tools is the Pegasus semistructural flat tripod represented in Figure 5.
This part was moulded in Fraunhofer ICT's
technical centre with four types of materials
(Table 2).
The two PP-SGF materials were moulded
at 240°C and 190°C while the reSound NF
grades were moulded at 190°C, a recommended injection moulding temperature
of the melt. The tool temperature was set at
50°C and the injection moulding parameters
were recorded. The injection moulding
pressure at 190°C was similar for PP-SGF30
and its equivalent reSound NF lightweight
alternative, around 850 bars. The process
was confirmed to be very stable for all the
materials. The same comparative processing
approach was used at injection moulding
machine supplier Arburg in Germany on a
mould for the Fraunhofer ICT beam geometry, a 390 mm-long, open-ribbed beam.
Similar conclusions were reached.
Both Pegasus and ICT beam parts were
tested at Fraunhofer ICT in tensile and

No102 January - February 2016 / jec

Feature Automotive

Fig. 4: Comparison of reSound NF 40% natural fibre-reinforced solution vs.
ultimate target profile

Some customers
value the flexibility
of using a concentrate and diluting it
with a neat resin in
order to adjust final
reinforcement levels
vs. application needs,
or to go below a 30%
reinforcement level.
Therefore, trials were
conducted in order to
evaluate the applicability of this process
with a 50%-reinforced reSound NF.
This concentrate was

mixed with neat PPh on an injection moulding machine in order to respectively obtain
a 40%- and a 30%-reinforced material. The
results obtained confirmed a robust and
compatible behaviour towards this dilution
process.

composites magazine 25

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016