*3.2. Surface Morphologies of the Hybrid Filler and PP Composite*

Figure 3a,c presents the surface morphologies of dried SiP SS and SP under a laser microscope with 50× magnification. A SiP SS is a single-distributed spherical silica particle and has a smooth surface with average size of 3–4 μm, having features such as high mobility and outstanding dispersity. Meanwhile, A SiP SP has a rough surface and irregular shape with an average size of 2–7 μm. According to the manufacturer, SiP SP demonstrates hydrophobic properties by chemically replacing the hydroxy groups on the silica surface with organic silicone compounds.

**Figure 3.** Morphological image of SiP particles: (**a**) SiP SS 50X, (**b**) SS/CNF 1000X, (**c**) SiP SP 50X, and SEM image of hybrid filler, (**d**) SP/CNF 1000X.

The structures of both hybrid fillers can be directly observed by using SEM. The SEM images in Figure 3b,d (SS/CNF and SP/CNF) illustrate that the SiPs were relatively homogeneously dispersed in the CNF matrix. It was verified that both types of SiPs were deposited predominantly on the surface of CNFs and prevented CNF agglomeration during the drying process. Both SiP SS and SP helped the dispersion of CNFs via a synergism effect. Silica not only offered a great surface area for coherence, but also provided aid in the dispersal of CNFs, which in turn reduced and minimized agglomeration. According to Sharip et al. [18], conventionally water-dispersed CNFs were employed to prepare a bio-nanocomposite, which required higher cost and energy. Hence, an ethanol/water mixed solvent method was used to address the setbacks of the conventional approach.
