Polyhydroxyalkanoates (PHAs) in extrusion coating of fiber-based substrate

In recent years the need to find alternatives for fossil-based materials in packaging solutions has become stronger due to various reasons. The interest towards utilizing bio-based and/or biodegradable materials for barrier packaging applications has greatly increased. Paper and paperboard as such are biodegradable and bio-based materials but need improvement in barrier properties through coating or lamination processes. Several bio-based polymers already exist, but they may lack the required barrier performance or their processability in film extrusion and especially in extrusion coating is challenging. Thus, both material properties and processability should be studied and developed further.

This work explores the processability and end-use properties of bio-based biodegradable thermoplastic coatings, particularly Poly(hydroxyalkanoates) (PHAs), in extrusion coating and casting. PHAs are linear polyesters produced mainly from microorganisms, including through bacterial fermentation of sugars or lipids. In this work, the selected polymers have been casted into films and coated at roll-to-roll pilot line on fibre-based substrate and their processability in extrusion has been analysed. The final coated structures produced were characterised for their barrier and mechanical properties.

This work targeted on creating extrusion coated fibre-based packaging solution that is both bio-based and biodegradable. It was observed that coatings with good processability and promising barrier performance levels were achieved. In addition, by certain means, excellent adhesion between the thermoplastic coating and fibre surface can be achieved.