Seal strength optimized films made of crystallizable biopolymers

• Applicants: Professor Dr.-Ing. René Androsch; Professor Dr.-Ing. Jens-Peter Majschak; Professor Dr.-Ing. Michael Nase
• Subject Area: Plastics Engineering ; Biomaterials ; Production Automation and Assembly Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542457034

In the course of replacing the fossil raw material base, biopolymers and natural fiber-based materials are increasingly coming into focus. The demand for recyclability is leading to a trend towards recyclable or biodegradable mono and composite packaging materials. Both trends make biogenic mono materials and separable or biodegradable composite packaging materials (e.g., biopolymer-coated papers) interesting and raise questions about how to combine functionality, a biogenic raw material base, and recyclability or biodegradability in the best possible way. Against this background of medium to long-term development, there is, among other things, a lack of knowledge regarding the properties of biobased sealing films and their interactions in the converting process. These include e.g. poly(L-lactic acid) (PLLA), polybutylene succinate (PBS) and starch-based polymers. PLLA is the most commonly used. Unmodified PLLA is too brittle for many applications and only becomes processable with additives or blending partners. In addition to the direct use of plasticizers, blends of PLLA and PBS can also be realized with the aim of producing flexible films for packaging purposes. The planned research work is intended to investigate structure-changing influences, in particular from the processing, on the seam strength using the example of heat contact sealing of bioplastics. This will improve the application potential of such plastics, e.g. in food packaging. For the formation of the sealed seam, dependencies on material selection, process control during film production and sealing, and microstructure will be investigated. This basic objective includes in particular: (I) Development of a measurement methodology for recording the spatially resolved temperature-time profile in the cross-section during the sealing of films. (II) Extension of the understanding of the microstructural changes occurring during sealing and their effects on the sealing seam properties, also considering the processing history during film production. (III) Further development and application of the experimental methodology for the fracture mechanical evaluation of the sealing seam properties with the aid of concepts of elastic-plastic fracture mechanics.

• DFG Programme: Research Grants