Creating Circular Composites: Challenges and Opportunities for Polymer Materials Engineers

The world of composites is evolving rapidly, and sustainability is at the forefront of this transformation. The sustainability concept of circularity has gained prominence, presenting both challenges and exciting opportunities for the composites industry. Materials and design engineers should consider these opportunities in the market and explore various avenues to help make their composites more circular. Let's explore some of the key means and outcomes of achieving circularity within the composites industry.

Means to a More Circular End

Chemical Recycling: Sometimes referred to as advanced or molecular recycling in the plastics world, chemical recycling of composites involves breaking down the composite’s matrix resin into molecular components by pyrolysis or solvolysis, allowing for the recovery of its fiber reinforcement. In pyrolysis, the polymer matrix is oxidized at temperatures >500°C, recovering energy plus the fibers. In solvolysis, the chain length of matrix polymers is reduced toward monomers while removing the matrix from the fibers so that both the fibers and matrix chemical products can be recovered. Pyrolysis is more likely to damage the recovered fibers and reduce their properties in subsequent cleaning steps to remove the pyrolysis char, but some composites or mixed material applications require this route. 

Mechanical Recycling: In contrast to chemical recycling, mechanical recycling does not affect the chemistry or composition of the composite being recycled. Its size is simply being reduced to a scale that renders it effective in a second-life application. Composites can be ground into small particles for use as engineered fillers or maintained at larger scales where fibers remain of reasonable length to be reused as fiber reinforcement in their next life.  

Recycling Materials into New Composites: Repurposing manufacturing waste to create new composites prevents it from going into landfills. This not only reduces waste but also lowers greenhouse gas emissions and offers opportunities for carbon capture. Likewise, utilizing post-consumer recycled (PCR) materials as composite components can significantly reduce the carbon footprint* of those composites. For instance, Avient engineers successfully used 100% PCR PET in composite unidirectional tapes and laminates, and PCR nylon 6 from reclaimed fishing nets in a LFT composite.

Circularity Takes a Village, and Everyone Benefits 

The shift towards circular composites is not a solitary endeavor. It's a collective effort that involves stakeholders at every point of the value chain. From manufacturers and engineers to end-users, everyone has a role to play in achieving sustainability goals, and everyone must benefit to be truly sustainable. 

As materials engineers, it's crucial to consider several factors when adopting more circular composites. These include the energy required for recycling, environmental impacts, carbon emissions, the value of the next life of the material, its longevity, and the economics of the entire process.

Business challenges exist in transitioning toward more circular composites, including collection and sorting complexities, strategic collaborations, and economic viability. Engaging consumers and end-users in this sustainable journey is also vital for success. Although there are existing models to guide us, achieving circularity requires collaboration across the entire value chain.

Avenues to Circular Solutions

To make composites more circular, explore a variety of fibers and a range of resins. Closing the loop is key to success, and it involves dedicated resources, external collaborations, and a willingness to start small and scale up as you learn along the way. Remember, the goal is progress, not perfection.

Materials engineers play a pivotal role in the quest to make composites more circular and sustainable. Embracing advanced recycling techniques, optimizing manufacturing processes, and engaging stakeholders across the supply chain are crucial steps on this journey. As we navigate the sustainability challenges and opportunities in the world of composites, let's work together to unlock a more circular and environmentally friendly future for the industry. 

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Looking for more sustainability inspiration? Download Avient’s 2022 Sustainability Report.

*Conducting a comprehensive carbon footprint analysis is essential to making informed choices