Biomaterials for additive manufacturing
March 23, 2018
A thermoplastic-based composite feedstock known as carbon fiber–ABS is the workhorse of polymer- composite 3D printing at DOE’s Manufacturing Demonstration Facility, located at ORNL.
It was the material that created the first 3D-printed car (the Strati), one of the first 3D-printed buildings (the AMIE Demonstration Project), the world’s largest solid 3D-printed component (a tool for The Boeing Company), and myriad other parts and objects.
While carbon fiber–ABS is easy to work with and offers great performance, it is a nonrenewable, petroleum-based product. ORNL researchers are working to bring additive manufacturing into the green economy by developing renew- able alternatives.
Plant-based fibers have been investigated to improve the properties of biobased polymer resins and make them easier to work with. One of these alternatives uses plant-based poly- lactic acid reinforced with cellulose nanofibrils from woody plants. Known as CNF-PLA, it has proven to be stronger and is projected to be cheaper than a comparable version of carbon fiber–ABS.
Another alternative formulation of the renewable material includes bamboo as the reinforcing fiber. It was used to print seating for two outdoor pavilions—as well as a large serving stand that supports a big 3D-printed overhead structure—last winter at the DesignMiami architecture exposition in Florida.
According to ORNL materials scientist Soydan Ozcan, the material is very promising and has great potential in many areas that do not require that fibers be long, continuous strings. “This material is also lower cost,” Ozcan added, “and it is performing in many ways close to carbon fiber–ABS in mechanical properties.”
Ozcan noted that the renewable material supports the environment in at least two ways. First, it has a far lower carbon footprint than petroleum-based options. Second, while the production of carbon fiber and carbon fiber–ABS is energy intensive, far less energy goes into the production of biopolymers and plant-based fibers such as bamboo.
The potential benefits of biomaterials, however, go even further, supporting a larger economy. In a sense, Ozcan said, this mimics the evolution of petroleum-based products over the past century. “When we look at the petroleum industry, it’s not just the business of selling gasoline for your car, but it’s also about the whole petrochemical industry, benefitting all products, bringing the cost down together.
“We have to create value from byproducts such as polymers and reinforcement materials that can be used to produce a wide range of products using additive and other manufacturing techniques.”
Looking forward, the researchers also hope to support American farming by making use of crops such as poplar that can be widely grown domestically, linking agriculture with biofuels and biomaterial products. The new Center for Bioenergy Innovation at ORNL is working on advanced poplar strains that tolerate a wide variety of growing environments.
Agriculture may become even more tightly linked with biofuels and biomaterials products because additive manufacturing can succeed in relatively small manufacturing operations, Ozcan noted.
“The way we are manufacturing is changing,” he said. “Additive manufacturing is making it possible to have one machine close to the feedstock or close to the end users.
“Can you create local agricultural businesses in conjunction with manufacturing? Can we plant locally, and can we manufacture locally and create businesses in local areas? Those are some of the questions that we are asking ourselves.”