Improved processability, compatibilization, mechanical properties and biodegradability of polylactic acid/crystalline cellulose composites compatibilized with glycerol citrate

Polylactic acid (PLA)/crystalline cellulose (CC) composites have emerged as alternatives to non-biodegradable plastics in the food packing industry. However, PLA and CC are incompatible. Furthermore, compatibilizing agents used in PLA/CC composites are usually toxic, because they are derived from petrochemicals and are expensive. This study reports, for the first time, the use of glycerol citrate (GC) as a compatibilizing agent for the PLA/CC composites. GC is biodegradable, inexpensive and non toxic. All the composites were prepared by blending PLA (80% w/w), CC (20% w/w), and GC (0, 3, 6, 9 to 12% w/w). The composites exhibited both the Newtonian and pseudoplastic behavior. The Cole-Cole diagram and scanning electron microscopy (SEM) analysis provided evidence that GC improved the interactions between PLA and CC. GC did not act as a nucleating agent for PLA. Thermal stability of the PLA/CC composites prepared with and without the GC were statistically identical. Tensile modulus and strength of the PLA/CC composites increased with GC content, with tensile strength enhanced to between 23.6 and 78.7%. Furthermore, GC reduced moisture resistance of the PLA/CC composites, but the biodegradability rate increased to between 225 and 610%, and the maximum enhancement in opacity (OP) was 39.3%.