Foam extrusion behavior and correlation between foam morphology and foam properties of externally plasticized cellulose acetate using inert gases

Today, polystyrene (PS) and polypropylene (PP) are the standard polymers for producing extruded foam sheets for packaging. Basically, these polymers are based on non-renewable resources and are non-biodegradable. Additionally, alkanes (e.g. butane) are widely used for the production of extruded PS foam sheets. In comparison to other physical blowing agents (PBA) such as inert gases, alkanes have a high global warming potential (GWP). Both, the polymers and the alkanes used do not fulfill the requirements of sustainable packaging products, which are, especially in the food packaging sector, more important than ever. Cellulose esters such as cellulose acetate (CA) are a promising class of bio-based polymers for producing sustainable foam sheets for thermoformed packaging trays. This contribution presents recent results of foam extrusion using externally plasticized CA and two types of inert gases, namely CO2 and N2, as eco-friendly blowing agents. The foam extrusion behavior, physical foam properties such as foam density, and foam morphologies were investigated.