Highly-toughened and dimensionally-stable TEMPO cellulose nanofiber/bio-PBSA nanocomposites fabricated via Pickering emulsion process

Abstract

Bioplastic poly(butylene succinate-co-adipate) (PBSA) has several advantages because of its flexibility and high biodegradability. PBSA, however, possesses poor mechanical properties and dimensional instability. To overcome this, PBSA composites with TEMPO-oxidized cellulose nanofibers (TOCN/PBSA) were fabricated via the Pickering emulsion method. Porous bio-nanocomposite TOCN/PBSA mediums were made by the Pickering emulsion method, followed by the subsequent lyophilization to obtain TOCN/PBSA films by compression molding. It was confirmed that the Pickering-emulsion condition was a key factor to control the TOCN dispersion state in composite films. The Young's modulus of TOCN/PBSA composite films increased to 305 MPa at the TOCN concentration of 5 wt%, which was almost twice as high as that of pure PBSA. The studies on the morphology and tensile testing also revealed that the dispersion state of TOCNs was important to achieve excellent reinforcement effects and to suppress the fracture of composite films caused by stress concentration. The coefficient of thermal expansion at the TOCN concentration of 5 wt% was reduced to ∼25 × 10−5 K−1, half the value of pure PBSA. It was concluded that compounding TOCNs via the Pickering emulsion method was a very effective reinforcement method to improve the mechanical properties and the dimensional stability of PBSA.