## 3 Results and Discussion
### Tensile Properties  
Tensile tests were conducted to estimate the tensile properties of all the prepared materials. Figure S1a,b in the supplementary data report, present the stress-strain curves of SCB-PE/ GNPs no BM and SCB-PE/ GNPs w BM respectively, along with neat SCB-PE. The estimated values of elastic modulus, tensile strength at yield and break, and elongation at break are reported in Table 2. In any case of the GNPs nanocomposites, the elastic modulus and the tensile strength at yield and break present higher values than neat SCB-PE. The reinforcement effect is a result of the effective stress transfer from the polymer to the GNPs. However, when the filler content exceeds 0.5 wt.%, the elongation at break decreases compared to neat SCB-PE. The presence of the GNPs particles restricts the macromolecular chains' mobility during the stress application. This results in stress concentration around the filler's particles and/or aggregates, where less energy is required to propagate a crack. Similar findings have been found by [PERSON] et al. for high-density polyethylene (HDPE)/GNPs nanocomposites [23]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **L110 (Å)** & **L200 (Å)** & **L110/L200** & **\(X_{c}\)\%** \\ \hline neat SCB-PE & 97.2 & 32.8 & 3 & 53.5 \\ \hline SCB-PE/0.5 GNPs no BM & 100.3 & 33.7 & 3 & 56.3 \\ \hline SCB-PE/1 GNPs no BM & 102.9 & 33.1 & 3.1 & 62.4 \\ \hline SCB-PE/2.5 GNPs no BM & 101.4 & 34.6 & 2.9 & 66.4 \\ \hline SCB-PE/5 GNPs no BM & 99.8 & 33.3 & 3 & 69.4 \\ \hline SCB-PE/0.5 GNPs w BM & 103.5 & 34 & 3 & 53.6 \\ \hline SCB-PE/1 GNPs w BM & 101.8 & 34.4 & 3 & 56.2 \\ \hline SCB-PE/2.5 GNPs w BM & 100.8 & 33.8 & 3 & 57.9 \\ \hline SCB-PE/5 GNPs w BM & 103.8 & 34.2 & 3 & 60.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Crystallinity degree values, lamellae thickness of (110) and (200) polyethylene’s crystalline planes and L110/L200 ratio of neat SCB-PE, SCB-PE/GNPs no BM and SCB-PE/GNPs w BM anocomposites. Additionally, it is observed that the elastic modulus and tensile strength at yield of the SCB-PE/GNPs w BM nanocomposites are larger in value than those of the SCB-PE/GNPs no BM samples. Elastic modulus increased values of SCB-PE/GNPs w BM nanocomposites are in agreement with the results of nanoindentation tests presented in our previous work [34]. Tensile strength at break follows similar behavior except for the SCB-PE/0.5 GNPs no BM nanocomposite, which presents the highest stress at break. The deformation upon failure also takes the largest value among the rest of the prepared materials for this sample. Overall, the tensile properties of the ball-milled nanocomposites present a more significant enhancement compared to the ones that were solely melt-mixed. Better dispersion of the GNPs and improved interfacial adherence induced by the ball-milling process result in better tensile properties of the SCB-PE/GNPs w BM nanocomposites, despite being less crystalline. During the ball-milling step, GNP particles are coated by the polymer matrix. This polymer coating on the surface of GNPs reduces the van der Waals forces between the platelets, which are the main cause of the aggregates' formation during the melt-mixing process, thus resulting in better dispersion of the filler in the SCB-PE matrix [34]. Similar results in regards to the elastic modulus improvement of thermoplastic/GNPs nanocomposites have been reported in the literature. More specifically, HDPE/GNPs nanocomposites prepared via melt-mixing containing 1 wt. % filler content presented a 5% elastic modulus increase [23], while the corresponding augmentation for SCB-PE/1 GNPs w BM is 47.7%. Linear low-density polyethylene (LLDPE)/GNPs nanocomposites were also studied in terms of their physicochemical properties. The tensile strength of the LLDPE/GNPs nanocomposite containing 1 wt. % GNPs increased by 5%; however, further increase in filler content led to reduced tensile strength values due to the agglomerated filler particles [35].