**3.3 Material characterizations**

Tensile properties were measured using a universal testing machine (EMIC, DL3000) based on ASTM D-638. Izod pendulum impact resistance was determined using a CEAST Resil Impactor tester based on ASTM D256. The data related to all the mechanical properties were based on the average of eight tested specimens.

Melting temperature (Tm), melt enthalpy (ΔHm) and crystallinity degree (χc) of the materials were determined using a Differential Scanning Calorimeter (STA 6000, Perkin Elmer) during the second heating scan. Samples weighing between 25 and 30 mg were heated from room temperature to 300°C at a heating rate of 10°C/min (first heating scan). The temperature was then lowered to 30°C at a heating rate of 10°C/min, and the samples submitted to a second heating scan under the same conditions as the first. Crystallinity degree was calculated using Eq. (1).

$$\% \text{ Cristalinidade} = \frac{\Delta \text{H}\_{\text{f}}}{\Delta \text{H}\_{100\%}} \ge 100 \tag{1}$$

where ΔHm is the endothermic enthalpy, ΔH100% the theoretical melting enthalpy of 100% crystalline PP (209 J/g) [56], and wt% the amount of PP in the blend or composite.

*Study of the Technical Feasibility of the Use of Polypropylene Residue in Composites… DOI: http://dx.doi.org/10.5772/intechopen.81147* 

The cryogenic-fractured surface morphology of the materials was examined under a scanning electron microscope (SEM, FEI, Quanta 400, accelerating voltage at 25 kV, 800X). The fractured samples were coated with gold.

### **3.4 Statistical analysis**

The statistical analysis of the results was performed using STATISTICA 6 software. Analysis of variance (ANOVA) was applied to test for significant differences between the means. Residual normality and homogeneity of variances (Cochran C and Bartlett methods) were determined before univariate tests of significance and Fisher's least significant difference (LSD) test, using a significance level of α = 0.05.
