Effect of Oxidation Treatment on the Mechanical Properties of Crystalline Fluorinated Polymer/Cellulose Nanofiber Composites Prepared by Melt‐Compounding Method

ABSTRACT Changes in the mechanical properties of polyvinylidene fluoride (PVDF)/cellulose nanofiber (CNF) composites prepared by the melt‐compounding method were investigated before and after 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO) free radical oxidation of the nanofiller. The TEMPO‐oxidized CNF formed needle‐like crystals using the cast film technique and showed higher dispersibility than the unoxidized CNFs. In PVDF/CNF composites kneading at 200°C for 5 min, TEMPO‐oxidized CNF showed excellent dispersibility. By contrast, the crystallinity and mechanical properties of the composites were improved by blending with unoxidized CNFs. This tendency was also confirmed during the structural formation of the composites subjected to uniaxial drawing. Among the drawn and oriented composites, the PVDF/TEMPO‐oxidized CNF composites exhibited superior elongation properties, whereas the PVDF/CNF composites had superior Young's modulus and maximum stress values. It was suggested that homogeneously dispersed TEMPO‐oxidized CNF may promote the rigidification of the amorphous regions of PVDF in the composites.