Acetylated microfibrillated cellulose as a toughening agent in poly(lactic acid)

Composites from poly(lactic acid) (PLA) and acetylated microfibrillated cellulose (MFC) were prepared by a solvent casting technique. MFC, mechanically isolated from never‐dried bleached birch Kraft pulp, was used as a reinforcement. The acetylation reaction was carried out at 105°C in toluene and proved to be an effective way of increasing the dispersion of MFC in a nonpolar solution of PLA in chloroform. The maximum acetyl content (10.3%) was achieved after 30 min of reaction time. This could be translated to a degree of substitution (DS) of 0.43. The acetylation was confirmed by Fourier transform infrared spectroscopy. MFC with a higher DS exhibited a more pronounced effect on the properties of PLA. Mechanical testing showed that Young's modulus increased by approximately 70% and the tensile strength increased by approximately 60% at a fiber weight fraction of 20%. At an MFC loading of 10 wt %, the strain at break and toughness, expressed as the work of fracture, increased by around 500%. The Young's modulus increased by approximately 15%, whereas the tensile strength remained the same. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012