Effect of lignin as accelerator of the biodegradation process of poly(lactic acid)/lignin composites

The biodegradation time of poly(lactic acid) (PLA) in the environment can be long, according to environmental conditions. Therefore, the introduction of organic materials from renewable sources, such as lignin, is interesting since it can result in a lower biodegradation time. In this study, PLA was melt blended with 5, 10 and 15 wt% of Kraft lignin. The composites were prepared using a high-speed mixer rotating at 3000 rpm. In this process, the mixing, melting, and homogenization take place by the high friction between the rotor and the polymer. Test specimens were obtained by hot pressing. The thermal, mechanical and morphological properties of the composites were evaluated. Test specimens for Izod impact strength tests of all compositions were buried in the aquarium apparatus and kept at room temperature with humidity controlled. The samples were removed at 0, 30, 60, 90 and 180 days. After each time interval, the samples were evaluated by Izod impact strength tests and scanning electron microscopy. The results obtained demonstrate that lignin is a great option to accelerate the biodegradation of PLA in the garden soil. The composite of PLA/lignin with an addition of 10 wt% of lignin is the better option for the manufacture of the biodegradable packages since it has similar thermal and mechanical properties to neat PLA and has a higher biodegradation rate.