A bumper sees low-speed impact, car washes, sun load and paint. The compound needs toughening, weathering and paintability together.
Bumper bodies typically serve between -30 °C and 80 °C, must survive low-speed impact — regulations generally require no visible damage after a 4 km/h pendulum strike — and sit exposed to UV, rain and car wash chemicals for years.
All three point to the same conclusion: the material must stay tough at low temperature. Neat PP becomes near-brittle below 0 °C, so an EPDM or POE toughening phase is mandatory.
The mainstream answer is PP+EPDM-T20 or T25: 20-25% talc carries stiffness and dimensional stability, while EPDM lifts notched impact at -30 °C above roughly 5-10 kJ/m².
For on-line painting, paintability enters the picture too: PP is non-polar, requiring flame or plasma pre-treatment, or a paint-ready modified system.
Verify notched impact at room temperature and -30 °C, flexural modulus, colour and impact retention after heat ageing, ΔE after UV ageing, and cross-hatch paint adhesion.
The most often skipped item is low-temperature impact after painting — the film embrittles in the cold and lowers the impact capability of the whole assembly.
EPDM toughened with talc filling; notched impact 8 kJ/m² at -30 °C (35 kJ/m² at 23 °C), used for bumpers, exterior trim and outdoor products.
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Higher filler loading with impact modification, giving improved stiffness and heat resistance for exterior parts with tighter dimensional demands.
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Same impact modified system as the light grey grade in a blue-black shade, for exterior parts with specific colour requirements.
Request Data Sheet & Quote →A worked calculation showing 42% weight reduction and 28% lower piece cost, plus the three metrics that must be validated.
Low cost, low odour and easy processing are hard requirements in interiors, and the split between PP-TD20 and PP+EPDM is clear-cut.
Large thin-wall parts value stiffness, dimensional stability and low odour most — a combination PP-TD20 is hard to beat.
Send us wall thickness, temperature, load and volume — technical reply and pricing within 24 hours.
