Recently, a team at the Fraunhofer Institute for Applied Polymer Research IAP invented a flexible and recyclable plastic film material based on poly(lactic acid) (PLA) bioplastics, which will be awarded the 2024 Josef von Fraunhofer Prize.
Dr. Antje Lieske of the research team said that because of its high stiffness, PLA is ideal for rigid packaging such as disposable cups, but not for flexible disposable packaging such as shopping bags, due to the fact that shopping bags are one of the main sources of disposable plastic waste.
To solve the problem, the team combined plasticizers (i.e., polyethers) directly with the polymer chains to make the material more flexible in the long term.
Polyethers are non-toxic, commercially available, and can also be produced from bio-based feedstocks. Until now, plasticizers have been blended into PLA as additives. Over time, however, the plasticizer molecules migrate out of the material, causing the PLA to harden again. To prevent this migration, the team anchored the polyether to the polymer and synthesized PLA-based block copolymers in which the ends of the polyether chain segments are covalently linked to the PLA chain segments.
"The end result of the synthesis was a new flexible PLA material that is free of migrating plasticizers and, unlike high-pressure polyethylene (LDPE), is at least 80% bio-based. In the future we may be able to increase this percentage to close to 100%," explains the team's Dr. André Gomoll. "In addition, our material can be produced economically, efficiently and directly from commercially available raw materials by mid-sized companies through a simple synthesis process. Finally, the material can also be processed into plastic films using conventional processing equipment in a manner similar to LDPE - and can be chemically recycled with much less energy input than LDPE."
This new bioplastic will make an important contribution to sustainable plastic packaging materials. In addition to flexible packaging films, the material may also open up entirely new uses, such as in the automotive industry, the textile industry and 3D printing.
