In order to have all the films with the same thermal history alsothe PLA pellets were extruded and pelletized again. The films wereprepared by using a single screw extruder and before the inser-tion in the hopper the pellets of PLA and PLA/ZnO (obtained fromthe twin-screw extruder) were again dried in oven for 24 h at 65◦Cunder vacuum. The single screw extruder has, as terminal, a cal-ender characterized by two counter-rotating cylinders that allowthe film passing through them still in the plastic state and a thirdcylinder functional to direct the output material up to the collectingcylinder. The extrusion was conducted at 160/170/180/170/180◦C,from the hopper to the die and the screw speed was 40 rpm. Theextruder and the chill roll unit were Collin E 20T and Collin CR 72T(Ebersberg, Germany).