TEMPO-oxidized cellulose nanofiber reinforced starch film with pH-responsive weakening and rapid marine-degradability

Abstract

Self-standing films made of starch are a promising material for single-use packaging owing to their higher abundancy, degradability, and economical processability. However, weak mechanical strength and poor freshwater durability restricted their application. Our previous research demonstrated that blending TEMPO-oxidized cellulose nanofiber (TCNF) with modified starch enhances mechanical strength and freshwater durability through hemiacetal bonding. In this study, we demonstrated pH-responsive weakening in seawater and rapid marine-microbial degradability of TCNF reinforced modified starch films. The TCNF was blended with hydroxypropyl starch (HPS) and di-aldehyde starch (aldS) to develop the films. pH-responsive swelling and weakening were performed in freshwater and seawater with a variable pH from 4 to 9. Moreover, marine microbial degradability was evaluated in artificial marine environment. TCNF/modified starch film rapidly lost up to 80 % of its strength in seawater and has shown higher marine microbial growth and degradability compared to neat TCNF film. The TCNF/HPS film demonstrated the ideal behavior of both pH-responsive weakening with adequate microbial degradability. Therefore, it has the potential to become the next-generation packaging material to help address the problem of floating debris.