Dielectric Enhancement in Composite Films via Copper‐Coated Microcrystalline Cellulose and Poly(Lactic Acid)

ABSTRACT The aim of this work was to develop composite films from microcrystalline cellulose modified with copper via a green process for use as electrical capacity thin films. MCC/Cu contents of 1, 2, 3, 4, and 5 phr were mixed with PLA to prepare composite films via a one‐step cast film extrusion process. Compared to PLA film, the composite films had slightly lower crystallization and melting temperatures, unchanged glass transition temperature, increased crystallinity, higher dielectric constant, and lower loss tangent. The highest dielectric constant, 11.47, was found in PLA‐MCC/Cu2. The composite films were also successfully biaxially oriented with 2 × 2, 3 × 3, and 4 × 4 draw ratios. Crystallinity significantly increased after stretching the composite films, while the glass transition and melting temperatures remained unchanged. Furthermore, BOPLA‐MCC/Cu with a 4 × 4 draw ratio exhibited the highest dielectric constant of 51.05, representing a fivefold increase compared to unstretched films.