3.2.3. Film morphology
SEM micrographs of the surface and freeze-fractured cross-section of FPI/FSG films without and with 100% BEO in the absence and presence of 3% ZnONP are illustrated in Fig. 4. The slightly rough surface was noticeable in the control FPI/FSG blend film (without BEO and ZnONP). No obvious separation was observed in the matrix of FPI/FSG blend film, indicating the compatibility between FPI and FSG. Roughness of surface structure was more pronounced in films incorporated with BEO and ZnONP than that found in the control film. The increases in the roughness could be due to the distribution of ZnONP as well as BEO droplet throughout the filmmatrix. Thismight be also associated with the coexisting of
protruded film structure as indicated by the increased thickness of resulting films (Table 1). Furthermore, nanocomposite films showed distinctive ZnONP images on their films surfaces as evidenced by the appearance of white particles on the surface and cross-section of films. Those ZnONP were uniformly dispersed in the nanocomposite films, leading to effective force transfer from protein matrix to ZnONP reinforcing phase. This could be associated with the higher TS of FPI/FSG nanocomposite film with 3% ZnONP,compared with other films (Table 1).