Fraunhofer Introduces Innovative PLA-Based Flexible Film

Flexible, single-use plastic films often found in shopping and garbage bags are predominantly manufactured from petroleum-derived low-density polyethylene (LDPE). These films have a significant carbon footprint and contribute to environmental pollution. A team at the Fraunhofer Institute for Applied Polymer Research IAP has now developed a flexible and recyclable plastic film material based on polylactide (PLA) bioplastic, paving the way for its commercialization. In recognition of their efforts, they will be awarded the Joseph von Fraunhofer Prize for 2024.

Recycling and defossilization are essential for sustainable plastics. Ideally, plastics are broken down into their basic components after use and then used to create new plastics with the same properties. However, some material is lost in the cycle of production, use, and reuse. " To further promote the circular economy, these losses need to be offset using non-fossil raw materials. This poses a challenge since bio-based equivalents for fossil plastics with the same properties are generally unavailable," explains Dr. Antje Lieske, Head of the Polymer Synthesis department at Fraunhofer IAP in the Potsdam Science Park. " Lieske further points out that while various additives can improve these properties, they may disrupt recycling processes, incur high costs, pose environmental risks, and importantly, they are not derived from bio-based sources.

Polylactide (PLA), a biopolyester, presents a promising solution to this issue: it is bio-based, biodegradable, easily recyclable, and boasts significant market potential among bioplastics. Its high stiffness makes it ideal for rigid packaging like disposable cups, but it has not been suitable for flexible disposable packaging, such as shopping bags, which are a major source of plastic waste. Dr. Antje Lieske, along with her colleagues André Gomoll and Dr. Benjamín Rodríguez at Fraunhofer IAP, has addressed this challenge.

“We integrated plasticizers, known as polyethers, directly with the polymer chain to enhance the material's flexibility over the long term," explains Dr. Benjamín Rodríguez. " Polyethers are commercially available, non-toxic, and can be manufactured from bio-derived raw materials. Previously, plasticizers were added to PLA as separate additives, but over time, these molecules would migrate out, causing the PLA to become stiff and rigid again. To prevent this, we anchored the polyether to the polymer. We synthesized PLA-based block copolymers, where the polyether chain segment is covalently linked to PLA chain segments at both ends.”

The result is an innovative, flexible PLA material that is free from migrating plasticizers and composed of at least 80 percent bio-based content, unlike LDPE. “In the long term, we might increase this proportion to nearly 100 percent,” explains Gomoll. “Additionally, our material can be cost-effectively produced from commercially available raw materials through a simple synthesis process. This process can be carried out locally by medium-sized companies as a continuous operation, without the need for large-scale synthesis plants. Previously, PLA could only be profitably produced in large-scale plants, excluding smaller companies from manufacturing. Moreover, the new PLA material can be processed into plastic films using conventional equipment similarly to LDPE and can be chemically recycled with significantly less energy input than LDPE,” adds Gomoll.

These distinctive material properties led the Polymer-Group company to commercialize the product. In 2023, SoBiCo GmbH, a subsidiary of the Polymer-Group, launched a production plant for the new PLA block copolymers in Pferdsfeld, western Germany. The facility currently produces 2,000 tons of the new bioplastics annually under the brand name Plactid®. In the long term, production is expected to scale up to 10,000 tons of the flexible PLA material each year.

This new class of bioplastics will significantly enhance the sustainability of plastic packaging materials. Beyond flexible packaging films, the innovative material has the potential to open up entirely new applications, such as in the automotive sector, the textile industry, and additive manufacturing.