Question 1

What plastic is used under a car bonnet?

Accepted Answer

Engine-bay components are typically glass-filled polyamide (PA66 or PA6) for the most thermally demanding parts (intake manifolds, valve covers), and glass-filled or talc-filled polypropylene (PP) for less demanding parts (fan shrouds, battery housings, fluid reservoirs). All grades are formulated to meet ISO 16750 thermal cycling and chemical resistance requirements.

Question 2

Why are some engine parts plastic now?

Accepted Answer

Plastic engine components weigh 30–50% less than the aluminium or steel parts they replace, which improves fuel economy and CO₂ emissions. Glass-filled PA66 intake manifolds, for example, save about 1.5 kg per vehicle versus aluminium. Plastic also enables more complex internal geometry (like integrated coolant channels) that would require multi-piece metal assemblies.

Question 3

Can plastic engine covers handle high temperatures?

Accepted Answer

Engine-bay polymers are formulated to specific continuous-service temperatures: glass-filled PA66 handles 150–180 °C continuously; PP-based grades top out around 130 °C. Components placed near the exhaust manifold or turbocharger require higher-grade polymers (PPS, PEEK) or stay in metal. Manufacturers map under-hood thermal zones during platform development to assign the right material to each part.

Question 4

What plastic is used for EV battery housings?

Accepted Answer

EV battery module housings increasingly use flame-retardant polypropylene (FR-PP) — a halogen-free formulation that meets UL94 V-0 and provides high voltage tracking resistance for bus-bar proximity. Glass-filled PA is also used for some structural components. The shift from aluminium to plastic battery housings can save 30–40% on weight at module level, an important factor in EV range.

Question 5

Which polymers are most common for automotive under-hood?

Accepted Answer

Most common materials are Polypropylene. Choice depends on regulatory requirements, mechanical performance, and cost target.

Question 6

What regulations apply?

Accepted Answer

Key regulations include ISO 16750 thermal. Suppliers must provide a Declaration of Compliance documenting that the specific grade meets the applicable standards.

Question 7

What lead times can I expect?

Accepted Answer

Distributor stock items: 1–3 days. Producer-direct prime: 1–4 weeks. Off-spec or near-prime spot lots: same week. Plan inventory accordingly.

Polymers for automotive under-hood

Recommended polymers

Regulatory considerations

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