Boosting Recycled Polypropylene: Milliken and ExxonMobil Deliver Automotive-Grade rPP

16.06.2025

Milliken and ExxonMobil joined forces to tackle the limitations of recycled polypropylene (rPP) in demanding automotive parts. Their solution – a synergy of DeltaMax® performance modifiers and Exact™ elastomers – delivers impact strength, stiffness, and flow rate improvements that meet OEM standards while supporting sustainability goals.

Challenge: High Standards for Recycled Plastics in Automotive Applications

As automotive OEMs increasingly adopt recycled polypropylene (rPP) for non-critical parts, attention has shifted toward high-performance functional components. These parts must withstand mechanical stress, offer temperature stability, and support fast injection molding cycles to remain cost-efficient.

Yet, both post-consumer and post-industrial rPP – even sourced from end-of-life vehicles – often fail to meet stringent OEM requirements for impact resistance, stiffness, and processability.

Solution: Smart Formulation with DeltaMax® and Exact™

Leveraging their long-standing collaboration, Milliken and ExxonMobil developed advanced rPP formulations using:

• Milliken's DeltaMax® performance modifiers to boost impact strength and melt flow
• ExxonMobil’s Exact™ polyolefin elastomers (POE) for rubber-like toughness and structural integrity

Seven trial blends were created, containing up to 25% Exact™ POE and rPP with ~15% polyethylene. These were tested for flexural modulus, tensile strength, Charpy impact at 25 °C and –20 °C, and melt flow rate (MFR).

"Creative solutions to boost performance of PP compounds containing post-consumer rPP are highly expected by Automotive OEMs to meet their own sustainability goals and increase the usage of recycled content," said Sébastien Dessenne, Automotive Program Manager at ExxonMobil.

DeltaMax® and co. are additives that give plastics specific properties. Without them, recycled PP would often be too brittle or too stiff.

Modern vehicles consist of up to 15% plastic – and that is no coincidence. 1 kg less vehicle weight saves around 0.1 liters of fuel per 100 km.

In the case of Milliken & ExxonMobil, the deflectors had to be tested in seven different formulations before they were OEM-ready.

Results: Meeting Mechanical and Sustainability Targets

Key outcomes of the optimized formulation include:

• Charpy impact: 50 kJ/m² at 25 °C and 4 kJ/m² at –20 °C
• Flexural modulus: approx. 900 MPa
• Tensile strength: above OEM benchmarks
• Melt flow rate: improved more than twofold, reducing processing costs and carbon footprint

These benefits stem from the combined action of POE and DeltaMax, enabling excellent matrix compatibility and dispersion.

"We harnessed the synergy between Exact™ Polyolefin Elastomers and DeltaMax to enable developing critical automotive parts that incorporate post-consumer rPP," shared Dr. Philippe Scheerlinck, Senior Market Development Manager for Milliken’s Chemical Business. "Allowing the creation of viable rPP compounds that deliver sustainability benefits across the value chain is a major win, and we’re proud to play a role in solving this challenge together with our partners at ExxonMobil."

Industry Impact: A Scalable Model for Sustainable Plastics

By demonstrating that recycled materials can meet high-performance criteria, Milliken and ExxonMobil offer a replicable path for OEMs seeking both quality and climate accountability. This dual approach – technical performance plus environmental gain – positions rPP as a viable, circular alternative to virgin plastics in automotive manufacturing.