In this
rule of thumb post, we discuss the use of metal fibers, carbon fibers and glass
fibers in plastics compounds to increase the EMI shielding effectiveness.
In another post, I showed already the importance of EMI shielding for new e-mobility
applications and polymer material selection.
Key questions for new plastic compounds are:
1) How
high is the additive level to fulfill the set requirements? In our case, how
much steel, carbon, glass fiber is needed to reach a sufficient shielding effectiveness
according CISPR 25 (A1 and A2 level)
2) What
is the impact of the compound modification on the processing equipment and what
is the impact on the allover properties such as mechanical, thermal and chemical
properties?
Finding
answers to the above questions, the research institute Fraunhofer LBF conducted
a study [1]. They investigated PA 6.6 base resin pellets loaded with 10%
stainless steel fibers, 20% carbon fibers, and 30% long glass fiber and
compared them to the unreinforced PA 6.6 pellets. The test conducted was a DKI platelet
wear testing method. With this method it is possible to find out the impact of
the different compounds on the production processing equipment such as
injection moulding machines.
Results
The
study showed that the 10% stainless steel fiber PA 6.6 compound resulted in approximately
the same EMI shielding performance as the 20% carbon fiber PA 6.6 compound.
Furthermore, the stainless steel fiber compound results in a much lower wear
and tear of the equipment, compared to the other compounds, especially carbon
fiber.
Table 1 shows the amount of stainless steel
fibers needed to achieve a certain EMI shielding level [1].
 |
| Table 1: amount of stainless steel fibers needed to achieve a certain EMI shielding level [1]. |
Figure 1 shows the filler addition needed to achieve a certain EMI shielding level [1].
 |
| Figure 1: filler addition needed to achieve a certain EMI shielding level [1]. |
Conclusions
Plastic compounds modified with stainless steel fibers are an effective alternative to carbon fiber loaded compounds since a low filler load is needed resulting in lower wear and tear of moulding equipment and keeping the allover properties in balance.
Thanks for reading and #findoutaboutplastics
Herwig
Literature
[1] https://www.bekaert.com/-/media/Files/Download-Files/BFT/White-papers/Whitepaper-4--Shielding-EN.pdf?la=en
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