For the wide range of products available in supermarkets, fresh food must be transported safely over long distances. Transport boxes made of hollow-chamber multiwall sheets, which are similar to corrugated cardboard boxes, are particularly suitable for this purpose. Like these, they have a low weight and yet are highly resilient. Unlike cardboard boxes, they are waterproof, water-resistant and easy to clean.
At present, hollow-chamber multiwall sheets are made of fossil-based plastic, mostly polypropylene (PP). Bioplastics blends available on the market were previously not suitable for demanding profile sheet extrusion. Researchers at Fraunhofer UMSICHT have developed a tailor-made blend system made of bioplastics with similar properties to the PP blend to be replaced.
The challenge of profile extrusion
The basis for the material development was polylactic acid (PLA), a comparatively inexpensive, commercially available bioplastic that is biodegradable under industrial composting conditions. However, the properties of pure PLA or market-available PLA blends were not sufficient for industrial profile sheet extrusion. Here, improvements had to be made by adding further blend partners and additives, especially with regard to the rheological parameters of the melt and the morphology of the final mixture.
The material development was scientifically substantiated by systematic investigations of the relationships between composition, melt properties and processing of the mixture. Material development was carried out at the plastics technology center of Fraunhofer UMSICHT in Willich specialized in such projects with bioplastics. To test the processing properties, trials were carried out at a globally active manufacturer of hollow chamber profile tools. The biodegradability of the material under industrial composting conditions according to DIN EN ISO 14885-1 was verified in our own biodegradation laboratory.