Biodegradation of Poly(lactic acid) Biocomposites Under Controlled Composting Conditions and Freshwater Biotope

• Main Authors: Pavel Brdlík, Martin Borůvka, Luboš Běhálek, Petr Lenfeld
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Polymers
• Subjects: biocomposites; poly(lactic acid); plasticiser; CaCo₃; nano-cellulose; aerobic biodegradation
• Online Access: https://www.mdpi.com/2073-4360/13/4/594

The influence of additives such as natural-based plasticiser acetyl tributyl citrate (ATBC), CaCO₃ and lignin-coated cellulose nanocrystals (L-CNC) on the biodegradation of polylactic acid (PLA) biocomposites was studied by monitoring microbial metabolic activity through respirometry. Ternary biocomposites and control samples were processed by a twin-screw extruder equipped with a flat film die. Commonly available compost was used for the determination of the ultimate aerobic biodegradability of PLA biocomposites under controlled composting conditions (ISO 14855-1). In addition, the hydro-degradability of prepared films in a freshwater biotope was analysed. To determine the efficiency of hydro-degradation, qualitative analyses (SEM, DSC, TGA and FTIR) were conducted. The results showed obvious differences in the degradation rate of PLA biocomposites. The application of ATBC at 10 wt. % loading increased the biodegradation rate of PLA. The addition of 10 wt.% of CaCO₃into the plasticised PLA matrix ensured an even higher degradation rate at aerobic thermophilic composting conditions. In such samples (PLA/ATBC/CaCO₃), 94% biodegradation in 60 days was observed. In contrast, neat PLA exposed to the same conditions achieved only 16% biodegradation. Slightly inhibited microorganism activity was also observed for ternary PLA biocomposites containing L-CNC (1 wt.% loading). The results of qualitative analyses of degradation in a freshwater biotope confirmed increased biodegradation potential of ternary biocomposites containing both CaCO₃ and ATBC. Significant differences in the chemical and structural compositions of PLA biocomposites were found in the evaluated period of three months.