Cellulose Enhanced Poly(Lactic Acid) to Fabricate Nano‐Scale Foams Characterized by High Volume Expansion Ratio

ABSTRACT Nano‐scale poly(lactic acid) (PLA) foams characterized by high volume expansion ratio (VER) endow materials with finer microstructures and unique properties, while it remains great challenges for preparing those foams. In this work, the epoxy chain extender ADR and carboxylate cellulose nano‐fiber (CNF‐C) were employed to help fabricate nano‐scale PLA foams with high VER. It was demonstrated that ADR promoted the formation of branched structures, creating favorable conditions for foams exhibiting high VER. The CNF‐C strengthened the rheological and crystallization properties of samples, where they combined with crystals to serve as attachment sites for bubbles. The micro‐cellular to nano‐cellular PLA foams were successfully obtained by introducing CNF‐C and changing foaming temperature. Interestingly, the average cell diameter of CPLA/CNF‐C5 foams prepared at 114°C could reach 160 nm, the cell density approached 2.33 × 10 15 cell/cm 3 , and the VER was as high as 5.2. The obtained nano‐foams possessed much better compression properties than those of the micro‐foams, and the nano‐foams maintained excellent thermal insulation performances. Generally, the PLA foams with nano‐scale cells were successfully obtained, where the VER was at the leading level. This advancement endowed nano‐scale foam materials with superior properties and much broader applications.