## 3 Results and Discussion
Thus, it can be deducted that glycerol and nanoclay had an important influence on the films' tensile properties and, more specifically, that increasing the nanoclay and decreasing the glycerol concentrations led to the increment of the films' tensile strength. However, this also led to the decreasing of the films' extensibility, which can be observed from the fact that the films with higher nanoclay and lower glycerol concentrations had more units that broke in the short log exact break time (Figure 4). The increase in tensile strength induced by the addition of nanoclay and, on the other hand, the increase in elongation at break induced by increasing the glycerol content has also been observed in the work of [PERSON] et al. (2014) [33]. The explanations for these phenomena are the roles of glycerol as a secondary plasticizer and its interaction with water, which reduces intermolecular forces, and nanoclay particles as junction zones that make the film matrix stronger [34]. Glycerol, which acts as a secondary plasticizer, interacts with water, causing a reduction in intramolecular forces and, consequently, a reduction in the tensile strength values and an increase in the elongation at break values. Moreover, the maximal break cycle level appeared below the 0.5 log tensile quotient, therefore indicating that a great, time-independent resistance until failure occurred in parallel with higher break cycles. This also indicates that a long-lasting tensile load, applied  
Figure 3: Degradation model plot of the log tensile quotient against log exact break time overlaid by the 4 elongation groups and the 3 break cycle levels, including the regression lines with 95% confidence bands. consecutively and for equal durations, decreases the films' tensile strength. The negative impact of cyclic loading of stress on polymeric materials' tensile properties was investigated by [PERSON] et al. (2010) [35], who reported that moderate cyclic stress loading on amorphous polyethylene causes decreasing stiffness and increasing plastic flow deformation. This gradual deformation of polymeric materials, like starch films with montmorillonite, under a steady stress load is called \"creep deformation\" [36]. Three explanatory variables entered the multiple regression model, explaining 74% of the total variation and, in decreasing order of importance: break cycle 51.6%, sample ID 16.2% and log exact break time 5.7%, while the elongation level was rejected from the model as not important. The reliability of the model is depicted in the plot created by the actual vs. predicted values (Figure 6a), and the scattered position of the residuals vs. the log tensile quotient (Figure 6b) indicates the variance homogeneity in the model. In Figure 6a, the 95% confidence intervals do not cross the horizontal line, and in Figure 6b, the points are evenly scattered around the horizontal line without outliers (values > 2 standardized residuals), indicating an adequate homogeneity of variance. The regression model revealed an important prediction profile of the variables' effects (Figure 7). The log tensile quotient decreased gradually as the log exact break time and break cycle increased, favoring the highest log tensile quotient values in the sample 7_35_10.5. The latter achieved a 3.91 log tensile quotient at a 4.73 log exact break time (antiloged 113 s) and at 3 break cycles. Furthermore, according to [PERSON]'s pairwise mean differences between sample IDs based on the error mean square of the ANOVA model, it possessed the highest mean value in the pattern of decreasing mean values (Table 4): 7_35_10.5 > 7_35_1 > 7_50 1 > 7_50 10.5 = 4_50 1. Figure 4: Scatter plot of the log tensile quotient vs. sample ID overlaid by the 5 increasing levels of log exact break time and 3 levels of break cycle. Horizontal lines denote the means of the exact break time levels.