Recycling of a starch-based biodegradable polymer

A new starch-based polymeric system, ZI1OU from Novamont, mainly composed of starch and polycaprolactone, was reprocessed several times in an extruder to investigate the recyclability of this biodegradable polymer. A previous investigation of the thermomechanical degradation in a mixer has been also done. The degradation is mostly due to the thermal stress but the presence of the mechanical stress strongly increases the degradation kinetic. During melt processing two concurrent processes take place: the first is the degradation, i.e. the breaking and shortening of polymeric chains, mostly occurring in the PCL phase; the second is the formation of some crosslinked structure in the starch phase. The rheological and mechanical properties, measured on samples subjected to repetitive extrusion operations carried out in a single screw extruder, clearly indicate that, in the adopted processing conditions, no significant modifications are observed. Only after five extrusions some decrease of these properties was measured.