*2.2. Composite Preparation*

The powders of ZnOc were mixed with iPP at two different compositions: 2% and 5% (see Table 1), in a twin screw extruder Collin ZK 25 (*D* = 25 mm and *L*/*D* = 24).


**Table 1.** Isotactic polypropylene/Zinc oxide coated with stearic acid (iPP/ZnOc) mixtures.

The temperature setting of the extruder from the hopper to the die was: 180/195/195/190/180 ˝C. The screw speed of the dispenser was 20 rpm while the speed of the extruder screws was 25 rpm.

Films of iPP and iPP/ZnOc were obtained by compression molding in a press at 210 ˝C and 100 bars. The films had a thickness of about 110–120 μm.

#### *2.3. Characterization*

The following technologies were used to determine the properties of the films:

#### 1) FT-IR Spectroscopy

Infrared spectra of the compression molded films were recorded with a PerkinElmer FT-IR spectrometer, model Paragon 500 equipment (PerkinElmer, Boston, MA, USA). The IR spectra were recorded in the range 4000–800 cm´<sup>1</sup> with 4 cm´<sup>1</sup> resolution and 20 scans.

2) Wide-Angle X-ray Diffraction

Wide-angle X-ray diffraction (WAXD) measurements were conducted using a Philips XPW diffractometer (Philips, Almelo, The Netherlands) with CuKa radiation (1.542 Å) filtered by nickel. The scanning rate was 0.02˝/s and the scanning angle was from 5˝ to 45˝. The ratio of the area under the crystalline peaks and the total area multiplied by 100 was taken as the crystalline percentage degree.

#### 3) Thermogravimetric Analysis

The thermal stability of the blends was examined by thermogravimetric analysis (TGA), using a PerkinElmer-Pyris Diamond apparatus (PerkinElmer, Boston, MA, USA) with a heating rate of 10 ˝C/min in air. Two measurements were performed for each sample.

4) Scanning Electron Microscopy

The surface analysis was performed using SEM, Fei Quanta 200 FEG (Fei, Hillsboro, OR, USA), on particles of the powders and on cryogenically fractured surfaces of composites. Before the observation, samples were coated with an Au/Pd alloy using an E5 150 SEM coating unit.

#### 5) Tensile Tests

Dumbbell-shaped specimens were cut from the compression molded films and used for the tensile measurements. Stress–strain curves were obtained using an Instron machine, Model 4505 (Instron, Torino, Italy) at room temperature (25 ˝C) at a crosshead speed of 5 mm/min. Ten tests were performed for each composition.

#### 6) Charpy Impact Test

The impact test allows for determining the degree of toughness of a polymer. Charpy impact tests were performed by using a pendulum CEAST (CEAST, Torino, Italy) with appropriate software for processing the data. The tests were carried out at room temperature on slabs obtained by compression moulding. Rectangular samples, with width of 3 mm, thickness of about 4 mm and length of 5 cm were used. The samples were cut from slabs obtained by using the same conditions adopted for the preparation of films.

7) Analysis UV-Visible Spectrometric

The UV-Visible spectrometry is useful for evaluating the ability of a material to minimize radiation potentially dangerous to the packaged food. The instrument used is a spectrometer Shimadzu UV-2101PC (Shimadzu, Columbia, MD, USA). UV-Vis spectra were recorded in transmission in the range 200–850 nm.
