Can You Recycle Carbon Fibre?

Over the past couple of decades, research on carbon fibers has boosted our understanding of this material. During the initial times of this discovery, there was a lot of skepticism that revolved around the material traits of carbon fibers. However, now the material is common in almost all large-scale manufacturing industries from aerospace to sports. 

It is due to these fibers possessing very low density while being able to match steel’s strength. Faster cars, better sports equipment, and more economical flights have all been possible due to the special properties that carbon fibers portray. 

Though this material has revolutionized the way we design and create, there are certain challenges that need to be addressed around them. For instance, what about the reusability of these fibers? Can we really recycle carbon fiber? In humanity’s quest for a sustainable future, this question is now more important than ever. 

Understanding Carbon Fiber

What gives carbon fiber its strength? In order to understand that, you would need to dive into the microscopic world of material science. 

Carbon atoms, when arranged in specific ways, possess unique properties. Diamonds, which are deemed by humans to be forever, are the most common example one can think of while trying to think of unique properties portrayed by carbon atoms. 

Diamond gets its strength due to the densely packed tetrahedral arrangement of carbon atoms without slip planes. Similarly, carbon atoms are densely packed along the direction of the fiber axis to form the fibers and they are often embedded in a polymer resin resulting in an exceptionally strong composite material. 

Is Carbon Fiber Sustainable?

The fibers have many miraculous properties, but recyclability isn’t one. Although non-biodegradable, this has been a hot area for research. 

Any material can be called recyclable as long as there’s a known mechanism to recycle it. Even though carbon fiber was deemed unrecyclable until two decades ago, now there are ways carbon fiber (and carbon fiber composites) can be recycled using methods such as mechanical, chemical, and thermal treatments. 

Challenges of Recycling Carbon Fibers

Composite Nature

As the carbon fibers are embedded in an epoxy matrix, breaking down the entire composite is a daunting task. Since the composite seamlessly acts as a perfectly strong material, specialized methods are required to break it apart into individual components. 

It’s Really Durable!  

The same reason that makes these composites so durable and strong, is the very reason why breaking them down is energy intensive and requires specialized chemical and thermal methods. The more energy intensive the recycling process is, the less economical sense it makes to recycle. 

What About Degradation?

The point of recycling is to be able to reuse the recycled material. Very harsh thermo-chemical methods employed to recycle the carbon fiber composite might result in the recycled fibers not possessing their good traits. Loss in strength and durability of the fibers would mean that the rCF (recycled carbon fibers) can be used in far fewer applications.

Some Methods:

Two-step thermolysis:

• This involves decomposing the epoxy first followed by oxidizing and recovering the Carbon Fibers via Microwaves.
• Microwave and traditional thermolysis have demonstrated recovery ratios of 94.49% and 93.47%, respectively. The advantages include faster operation, improved recovery rates, and reduced energy consumption.
• Although, prone to degradation. Tensile property mostly remains unaffected. 

Solvolysis:

• PHYre showcases clean recycled carbon fiber through patented solvolysis.
• The company claims that this process works for 90% of existing composites.
• Besides the fibers, this process can recover the oligomers present in the matrix as a process by-product, attaining full recyclability.

Electrochemical Method:

• This method involves optimizing NaCl solution concentrations and applied currents to achieve efficient recycling.
• Recycled carbon fibers obtained through this technique exhibit tensile strength at approximately 80% of that of virgin fibers.

Remember, this article is a mere glimpse into the boundless universe of carbon fibers. The fact that numerous methods are being tried and tested in labs worldwide is a testament to a sustainable future for all!