The effect of a small amount of modified microfibrillated cellulose and ethylene–glycidyl methacrylate copolymer on the crystallization behaviors and mechanical properties of polylactic acid

Abstract

With the purpose of improving the crystallization rate and toughness of polylactic acid (PLA) comprehensively, chemical modified microfibrillated cellulose (MMFC) and ethylene–glycidyl methacrylate copolymer (EGMA) were used in the preparation of the PLA/MMFC/EGMA composite. After controlled acetylation using acetic anhydride, MMFC exhibited an improved hydrophobicity, resulting in a much better dispersion in PLA matrix. To clarify the impact of MMFC on the crystallization behaviors and mechanical properties of PLA, PLA/MMFC composites with 1–20 wt% of MMFC were characterized using differential scanning calorimetry (DSC) analysis and stress–strain curves. It was revealed that in the presence of only a small amount of MMFC (3 wt%), the crystallization rate of PLA was enlarged for seven times when the crystallization occurred at 120 °C, and the tensile modulus and tensile strength were both increased by 25% compared with pure PLA. The effect of EGMA component on the crystallization and mechanical properties of PLA was considered based on the characterization of the PLA/MMFC/EGMA composite. It was confirmed from DSC thermograms that a small amount of EGMA (5 wt%) did not exhibit any negative impact on the crystallization of PLA in the case of PLA/MMFC-3 wt%/EGMA-5 wt% composite. Meanwhile, in the presence of the EGMA, PLA/MMFC-3 wt%/EGMA-5 wt% composite showed an obvious increase of elongation-at-break from 9.1 to 20.8 compared with pure PLA. A remarkable improvement of crystallization behavior and toughness of PLA was achieved due to cooperative effect of the small amount of MMFC and EGMA in the PLA composite.