Cellulose modified by citric acid reinforced Poly(lactic acid) resin as fillers

As the most extensively researched thermoplastic aliphatic polyester, poly (lactic acid) (PLA) derived from renewable resources has shown it tremendous potential at replacing the petroleum-based polymers in many fields. The greatest challenge hindering the use of PLA is considered as its poor toughness. In terms of reproducible processes and products, cellulose has been applied to the PLA matrix as reinforcing fillers but the poor compatibility due to the inherent hydrophilicity of cellulose and hydrophobic nature of PLA is troubling. To solve this issue, we carried out an effective water-based method to render the cellulose surface with high carboxylic group content through the esterification of hydroxyl groups with citric acid in a solid phase reaction to strengthen the hydrogen bonding interaction with PLA. Consequently, the modified cellulose showed good dispersion in PLA matrix. The resulting flexural properties of PLA composites incorporated by the citric acid-modified cellulose and its fibrillated form as fillers were improved compared to those of the pristine PLA resin. The potential nucleating function of the modified cellulose was discussed and the filler proportion in the composite was optimized. Because of the well-established processing technique, we believe that citric acid-modified cellulose has an immense potential as a sustainable and cost-effective reinforcing filler for PLA, as a representative of bio-based polyesters. • Citric acid-modified cellulose (CAC) used as reinforcing fillers for PLA composite. • CAC dispersed into the PLA matrix with good compatibility. • CAC reinforced the flexural property of PLA.