End-of-life recycling continues to be a thorn in the side of the composites industry. A lack of cost-effective recycling solutions leaves a lot of composite products headed for the landfill at end-of-life. That is good for neither the industry nor various regions around the country struggling with shrinking landfill space.
So what do we do? We find a way to recycle composites like carbon fiber-reinforced plastics so that they be reused two and three times without significant loss of structural integrity. That may now be possible, thanks to new technology that relies on a completely different kind of epoxy resin.
How Carbon Fiber Parts Are Made
The current process for making carbon fiber parts is pretty straightforward, explains Rock West Composites. Carbon fiber sheets or panels are impregnated with an epoxy resin before being laid in a mold. Once a layup is finished, the entire mold is vacuum-bagged to remove air and evenly distribute the resin. The mold is then put into an autoclave where the part is cured under high heat.
Rock West explains that the epoxy resin used in this process is a thermosetting resin. High heat curing turns the resin into a strong plastic material. The carbon fibers embedded within give the plastic additional strength and durability.
This process works very well for its intended purpose. However, thermosetting resin is the biggest enemy of recycling. Either high heat or chemical processing is necessary to separate the resin from embedded carbon fibers. Unfortunately, both processes reduce the integrity of the fibers. Both are also quite expensive.
Let’s Change the Resin
As recycling companies have been working out ways to make high heat and chemical processing more attractive to the industry, another company has quietly produced a way of fabricating composite parts that makes recycling comparatively easy. Their process is based in a new kind of resin that is much easier to separate from fibers.
Their resin is a reactive resin rather than a thermosetting product. It is a resin that does not require high heat or pressure for fabricating, so making parts using this resin is a lot easier and more cost-effective. Likewise, recycling composites fabricated with the process does not require high heat, either. The reactive resin can be separated from fibers by way of a reactive catalyst.
Recycling carbon fiber in this way has very little impact on the structural integrity of the fibers. They can be reused in layouts featuring the same reactive resin. A second recycling of the same material does reduce its integrity somewhat, but not significantly enough to render the fibers useless. They can be used to third time before subsequent recycling requires them to be chopped and/or milled for future low-grade fabricating.
Removing the Heat Changes Things
It would be hard to underestimate the importance of this new technology. Removing the heat from both sides of the composites equation changes things drastically.
For starters, a tremendous amount of heat energy is needed just to align carbon molecules to produce carbon fiber thread. That makes producing raw materials quite expensive. But then add in the high heat curing required to turn carbon fiber and thermosetting resin into a carbon fiber reinforced plastic. Autoclaves produce a tremendous amount of heat; they use a tremendous amount of energy to do so.
Remove high heat from the fabricating process and you save money. Remove it from the recycling process and you save even more. Thanks to a new kind of reactive resin, both are now possible. It will be interesting to see where all of this leads.