Plant-based polylactic acid (PLA) bioplastic is hailed as a biodegradable material, but it takes a long time to break down in the natural environment. In light of this, scientists at Washington State University (WSU) have developed a method to recycle it into a resin for 3D printing or additive manufacturing.
What is the PLA?
PLA is a polyester derived from fermented plant starch such as corn, cassava, maize, sugar cane or sugar beet pulp. These renewable compounds contain sugar fermented into lactic acid, which is then converted into PLA.
However, despite its many advantages over conventional polymers, including its lack of toxins, reduced energy consumption (65%) and reduced greenhouse gas emissions (68%), degradation of PLA is quite slow. at room temperature.
Yu-Chung Chang, postdoctoral researcher and co-corresponding author of the study, explains the environmental impact of PLA:
“[PLA] is biodegradable and compostable, but once you examine it, it turns out that it can take up to 100 years to decompose in a landfill. So, in reality, it still creates a lot of pollution. We want to make sure that when we start producing PLA at million ton scale, we know how to deal with it.
New method for recycling PLA into 3D printing resin
In a procedure created by Chang and his colleagues, the long chains of molecules that form PLA are disassembled using the inexpensive chemical aminoethanol. These chains are reduced to simple monomers, the fundamental constituents of plastic. The procedure can be performed in mild conditions and takes about two days.
The monomers are remixed to create a liquid 3D printer filament that can be light cured, like those already used in some 3D printers. When the team used the PLA-derived resin to 3D print test products, it was found that its thermal and mechanical properties matched or bettered those of other commercial resins.
“We found a way to immediately turn this into something stronger and better, and hopefully that will inspire people to recycle these things instead of just throwing them away. We have made stronger materials directly from scrap. We think this could be a great opportunity.
By comparison, recycling plastic waste usually requires shredding it into small pieces and then re-melting it into a usable filament. The melting temperature for the process is 160 to 180°C (320 to 356°F).
Now the WSU team wants to use the method to create recycled filaments from other types of plastics, such as polyethylene terephthalate (PET), a plastic commonly used in plastic bottles. The research, led by Professor Jinwen Zhang, was published in Green Chemistry on July 12, 2022.