Every day we interact with products manufactured using polymer chemistry — whether shower stalls, automotive parts, concrete structures or a wide range of plastics.
Modern fabrication utilizes additive manufacturing, in which a product is built by adding molecules to precise locations. This process is more commonly known as 3D printing. Additive manufacturing is more economical and potentially more sustainable because it requires less energy, produces less waste and overall uses less material.
However, some of the reactive diluents, compounds that are used to reduce the viscosity of resins — such as styrene — vaporize readily into the air and are harmful to humans and the environment.
Alternative diluents that are more environmentally friendly and can be used in manufacturing are a focus of research in Timothy Long’s laboratory in Arizona State University's School of Molecular Sciences.
Long, with fellow researchers from Virginia Tech, describe the versatility of new families of polyesters in their journal paper, "Vat photopolymerization of unsaturated polyesters utilizing a polymerizable ionic liquid as a non-volatile reactive diluent" in ScienceDirect.
Additive manufacturing using unsaturated polyesters with an ionic liquid diluent eliminates the release of volatile organic compounds (VOCs) while allowing the fabrication of complex parts with resolutions approaching the diameter of a human hair. This work solves major problems in the use of unsaturated polyesters, not only the elimination of VOCs, but also reducing waste.
“We can return waste polyester products back to their previous petroleum-derived monomers, aiming for carbon circularity,” Long said.
"Polyester resins represent one of the most important classes of polymer precursors, but the reliance on the volatile styrene as the co-monomer has been a significant limiting factor in their application," said Ian Gould, interim director of the School of Molecular Sciences. "Tim and his colleagues have come up with a very nice solution to this problem by using ionic forces to control the volatility.”
This research represents a partnership between the Biodesign Center for Sustainable Macromolecular Materials and Manufacturing and the Virginia Tech Department of Mechanical Engineering, with mechanical engineers and chemists working together to discover advanced materials for advanced manufacturing.
“Simply stated, the materials of 1950 are not suitable for the advanced manufacturing tools of 2021,” Long said.