Sunday, 30 June 2019

High Performance Polymers in Electrification: A Must-Have Or A Nice-To-Have (Part 3: Autonomous Driving)

Welcome back to the third part of the high performance plastics for electrification series. In the previous parts, we have discussed the polymeric materials used in battery systems and traction motors. Now, we a look at the high performance plastics used for autonomous driving applications.

Autonomous driving
  • Connectors
Connectors need to be reliable while driving (manual and autonomous driving mode) as well as when the OEM is assembling the different parts of the car in the manufacturing line. Therefore, connectors need to fulfil different requirements:
  • JEDEC MSL1 level of shelf life (=infinite);
  • no corrosion (especially pins; plastic parts need to be free of halogens, red phosphor, and ionic heat stabilizers);
  • continuous use temperatures of 140°C-180°C;
  • high chemical resistance;
  • high electric strength;
  • and CTI of 600 Volts (PLC0).

Connectors need to have a high ductility level too. Easy identification of high voltage connectors, insulators, and circuit breakers is achieved by coloring polymers in orange (color coding compulsory above 60 V). Polymers such as polyphthalamide (PPA) with a Tg of 120°C and above (Tg of 140 up to 180°C are possible) can handle the requirements listed above offering high mechanical strength with low moisture uptake, similarly to polyesters. Apart of aliphatic polyamides and polyesters, semi-aromatic polyamides such as PPA and polyarylamide (PARA) can be obtained in a non-halogenated flame retardant compound. Advantages of PARA are the high stiffness, excellent low creep, low moisture uptake and impact properties.

  • Light Detection and Ranging (LiDAR) and Radio Detection and Ranging (Radar) sensors
High performance plastics play an important role in connectors on the one hand as well as in sensors for autonomous driving on the other. An aliphatic polyamide absorbs water and moisture. This absorption is linked to a dimensional and mechanical change. LiDAR and radar housings need to be dimensional stable since their job is to scan the environment and create an accurate picture of the surrounding. Therefore, using polymers such as polycarbonate (PC), polyethersulfones (PESU), and polyphenylene sulfide (PPS) ensure the high dimensional stability combined with nearly no moisture uptake. Those polymers ensure safe communication of the different sensors over the life time of the vehicle.
  • Battery temperature sensors
Minimal temperature changes (+/- 1 °C) in the Li-ion batteries can impact their loading efficiency. Therefore, accurate management of the temperature by sensors is essential for keeping the batteries at their highest effectiveness level. For this type of sensors, polyethersulfones are best suited since their Tg is around 220°C and they show excellent dimensional stability. Furthermore, this stability is needed for keeping the sealing performance of the sensor’s O-ring seals.
  • 5G communication sensors
With the arrival of 5G mobile technology, our cars will be able to communicate with each other and the environment. Requirements for 5G related applications are mainly high speed data transmission, infrared transmission, retention of environmental influences and dimensional stability. Polymers such as polyether imides (PEI) and polysulfones are suitable to fulfill these requirements since their amorphous structure allows for tight tolerances and low CLTE, creep resistance and good IR transmission.
  • Outlook
In next steps, automotive exterior designers start to seamlessly integrate LED lighting systems with infrared transparency for LiDAR sensor systems [1]. In such application concepts, polycarbonates can play an important role. The integration of LiDAR systems into the car bumper will lead to another challenge: having clean lenses. This may be ensured by using fluorinated coatings which are based on fluoropolymer chemistry (e.g.  perfluoropolyether - PFPE).
  • Wrap-up
Electrification brings a whole mix of performance plastics in several applications. I have listed the material requirements and applications we discussed in this post including the previous two parts in two tables, which can serve as guidance through selecting the optimal polymer for your application.

Electrification application matrix for supporting polymer material selection

Material requirements of high voltage components in electric vehicles

Thank you for reading this third part of the electrification blog series! If you enjoyed it please do like and share it with your network.
Till next time!
best regards,
Herwig Juster
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