*3.1. Morphology of Graphene Sheets in a Nanocomposite Matrix*

The tailored process included designing a suitable screw configuration, paired with coordinating extruder conditions and blending techniques. This subsequently created a suitable medium for the graphene platelets to disperse readily, and distribute thoroughly within the multimodal-HDPE matrix, as demonstrated in Figure 3a,c. The mean particle size of the detected graphene particles and %area fraction (200 × <sup>200</sup> <sup>μ</sup>m2) was around 0.5 <sup>μ</sup>m2 and 0.0063, respectively. Graphene monolayers are transparent under an optical microscope, opacity of 2.3 ± 0.1%, while the optical loss become greater in the wrinkled and overlapped samples [34,35]. L. J. Cote et al. [35] found that the average light scattering from the wrinkled region was about 3.7 times that of the overlapped areas. For the nanocomposite produced using the pre-existing commercial approach, however, the mean particle size of the graphene agglomerates was calculated to be 4.12 μm2, with maximum particle size of around 4.7 μm2, and a %area fraction of 79.4 (see Figure 3b,d). The %area fraction and mean particle size were calculated based on transmission electron microscope (TEM) and light microscopy analysis, graphene particles of less than 0.05 μm2 or 500 nm were excluded from the calculations, i.e. the average lateral size

of graphene platelets ranges between 150–500 nm. A decrease in the %area fraction means a better distribution and fewer agglomerates.

**Figure 3.** (**a**,**b**) Light microscopy images and (**c**,**d**) TEM images show the dispersion and distribution of 1 wt.% loading of graphene platelets within the multimodal-HDPE matrix (PE-g-1%). Images for the similar nanocomposite produced by a pre-existing processing protocol (**right**), were compared with PE-g-1% produced in this study (**left**). The TEM and light microscopy images were taken at 10k and 20x, respectively.
