*2.8. Scanning Electron Microscope (SEM)*

The surface structure and morphology of fillers were analyzed using scanning electron microscope (SEM) (JEOL JSM-6460LA) (JEOL. Ltd., Tokyo, Japan). The morphology of raw OPEFB fiber, treated OPEFB cellulose and microcrystalline cellulose was studied under SEM to allow for comparison. Before images were captured, the fillers were coated with platinum using JFC-1600 Auto Fine Coater (JEOL Ltd., Tokyo, Japan) for getting the optimal SEM image of fillers. The surface and morphology of the raw OPEFB fiber and the treated OPEFB cellulose samples were taken at a magnification of ×500 and ×4000. Meanwhile, the morphologies of the microcrystalline cellulose and the ultra-sonicated nano-bentonite were taken at a magnification of ×30k and ×10k, respectively.
