Mechanical recycling of SMC composites for Automotive and Truck applications

Sheet Molding Compound (SMC) is widely used for its stiffness, durability, and Class-A surface quality, but its thermoset nature has historically limited recycling options. MCR has demonstrated that mechanically recycled SMC can be reintegrated into high-quality applications without compromising performance or manufacturability, using AOC resins for its SMC formulations.

MCR has developed SMC formulations incorporating recycled material sourced from post-industrial waste and end-of-life vehicle components. Using standard production processes and commercially available resin systems supplied by AOC, the company has demonstrated that recycled SMC can meet the requirements of automotive and truck applications.

SMC recycling

SMC has traditionally been considered difficult to recycle because thermoset matrices do not remelt. However, MCR has been working on mechanical recycling since 1997, initially processing clean production scrap. Over time, this approach was expanded to include more complex waste streams such as painted, bonded, and end-of-life SMC components, significantly increasing the potential for circular material flows.

The recycling process involves shredding, grinding, and milling SMC waste into a powder with a controlled particle size distribution. This recycled powder is used as a functional filler in new SMC formulations, partially replacing mineral fillers such as calcium carbonate. Particle size optimization proved essential to maintaining processability, with flow behavior affected more than mechanical performance.

Realistic conditions

MCR deliberately validated the approach under realistic and challenging conditions by using untreated end-of-life parts, including painted and bonded components. Even in these worst-case scenarios, recycled SMC could be successfully reintroduced into new formulations with stable and predictable performance.

Validation trials were conducted on representative automotive and truck parts, including panels, front modules, and coated components. All parts were produced on standard industrial equipment without process modifications, confirming immediate industrial applicability.

Performance validation

Extensive testing covered mechanical properties, bonding performance, screw retention, impact resistance, and fatigue behavior. Results showed that recycled SMC performs comparably to conventional materials, with no negative impact on fatigue and, in some cases, slight improvements.

Surface quality and paint adhesion were also assessed. While untreated end-of-life material occasionally resulted in reduced paint adhesion after aging, this effect was fully mitigated using in-mold coating (IMC). With IMC, all formulations achieved consistent surface performance, highlighting the robustness of SMC systems for circular applications.

From a technical and commercial perspective, recycled SMC provides a viable alternative to virgin mineral fillers, reducing raw material consumption while maintaining performance. Importantly, it can be implemented without changes to tooling, processing, or assembly operations, enabling seamless integration into existing value chains.

Great collaboration

The development of these solutions was supported by close collaboration between MCR and AOC. Combining recycling expertise with advanced resin technology enabled the creation of materials that meet both sustainability targets and industrial performance requirements.

Looking ahead, MCR continues to expand its recycling capabilities, including improved processing of mixed and post-consumer waste streams. Together with partners such as AOC, further developments will focus on increasing recycled content and supporting OEM qualification, reinforcing the role of thermoset composites in a circular automotive economy.

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