Sustainable starch foam film

The aim of the project is to develop a flexible, foamed film based on the renewable raw material starch as a sustainable alternative to fossil-based foams (e.g., LDPE) for packaging and construction applications. The starch-based foam film is intended to provide good shock absorption, elasticity, and smooth surface, making it well suited for packaging applications and, alternatively, for effective impact sound insulation in the construction industry.

To this end, the research team developed starch-based compounds with the highest possible starch content and optimized them for processing on conventional extrusion lines. Physical blowing agents (e.g._, CO_₂) are used to create a fine, closed-cell foam structure. Target densities are below 50 kg/m³ and film thicknesses are greater than 2 mm. Fraunhofer UMSICHT developed the formulation: starch is converted into thermoplastic starch (TPS) with the aid of processing aids. Using suitable blending partners, plasticizers, and additives, the compound overcomes the typical weaknesses of TPS: brittleness and moisture sensitivity.

Another key objective is assessing CO₂-neutral recycling at the end of the product's useful life. This includes examining various end-of-life options, such as material recycling (in-house recycling) and industrial compostability.

Foamed packaging films are often used only once and rarely recycled; thermal recycling is therefore the dominant method. At the same time, there is a growing demand for lightweight, cushioning packaging in e-commerce, as well as for sustainable insulation and acoustic solutions in the construction industry. The project addresses this gap with an industrially compostable starch-based foam film that can replace fossil-based materials both technically and economically.

Fraunhofer UMSICHT has many years of expertise in the area of starch-based compounds, film processing, and biodegradability/compostability testing (DIN CERTCO/BPI-approved laboratory). Together with IKV (foam extrusion), Loick (scale-up and market), SHS (data/process intelligence), and Gefinex (industrial manufacturing), this project addresses the entire value chain - from formulation to industrial processing.

Issues addressed and practical benefits:

• Substitution of fossil-based LDPE foams with starch-based, compostable alternatives with comparable performance
• Processing on standard plastic processing equipment, resulting in low investment barriers and rapid scale-up
• Cost advantages due to higher starch content combined with improved melt strength, flexibility, and damping
• Sustainability-based end-of-life options (material recycling, compostability) and targeted concepts for waste streams in packaging and construction
• For packaging: lightweight, shock-absorbing, fine-cell cushioning films, weldable, suitable for varying product sizes
• For construction: potentially high-performance impact sound insulation with a stable, closed-cell structure

The project team has developed a base formulation that can be individually adapted for different applications and/or processing methods. The base formulation remains process-stable during long compounding runs and has shown promising rheological properties for foaming. The researchers demonstrated the scale-up of granulate production based on this formulation during the project.

Various film samples were produced from the base formulation:

1.  Flat film (non-foamed) with good mechanical properties and a smooth, pleasant-to-the-touch surface; potentially suitable for other applications.

2. Flexible, physically foamed film

Characteristics of the foamed film (base formulation)

Further material formulations, process parameters and blowing agent proportions are being systematically investigated for optimization. Two promising formulations have already been identified in compounding: they showed higher melt elongation; foam film tests are still pending.

• Loick Biowertstoff GmbH
• Institut für Kunststoffverarbeitung an der RWTH Aachen (IKV)
• SHS plus GmbH
• Gefinex GmbH