In general, by the reinforcement with inorganic particulates, the transparency of films is significantly affected which can limit the potential applications in packag­ing. In case of cellulose-chitosan nanocomposites, the optical transparency of the films is often considered as auxiliary criterion to judge the miscibility of the compo­nents. In an earlier investigation, the transmittance of UV/Vis light (200-1000 nm) of the casted films of cellulose nanocrystals reinforced nanocomposites was shown to decrease slightly from 90 to 85% with 0 to 10 wt.% of CNCs /CNWs. Above 10 wt.% of CNCs loading, the transmittance is significantly decreased.

Fernandes et al.39 have demonstrated an improved transparency with nanocom­posites prepared using longer NFCs nanocomposites in two different types of chito — san with different molecular weight. Both low and high molecular weight chitosan (LCH and HCH) were modified to dissolve in acetic acid and water. The four types of nanocomposites with 0-20 wt.% NFC in HCH and water-soluble HCH (WSHCH) and 0-60 wt.% NFC in LCH and water-soluble LCH (WSLCH) prepared via solu­tion casting exhibited a transparency up to 20-90% depending NFC content. Up to 5 wt.% of NFC, the optical transmittance was unaffected. They have also exhibited a significant increase in thermal stability, for example, the initial-degradation tem­perature (7’di) from 227°C to 271°C.39 In a similar approach, highly transparent (up to 90% optical transmittance) and flexible films were also produced using bacterial cellulose (BC) (Fig. 16.2).44

These materials have the great potential to be exploited in food and antimicro­bial packaging applications where the transparency, mechanical properties, thermal stability are required with inherent antimicrobial activity and biodegradability (after disposal).