The effect of biodegradable polymer blending on the disintegration rate of PHBV, PBS and PLA in soil

This study generates new insights into the disintegration phenomena that take place upon blending different classes of biodegradable polymers. Polymer blending is found to be an effective method to tailor the disintegration rate of these polymers in soil. It is shown that the biodegradation of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) can be accelerated by blending with poly(butylene succinate-co-adipate) (PBSA) and polycaprolactone (PCL). The observed high rate of disintegration of poly(butylene succinate) (PBS) in soil (severe deterioration in 4 weeks, and fragmentation in 4 months) does not fully align with its current reputation in the market as a polymer that is non-biodegradable in soil. Disintegration trials executed in soil media with different inoculants demonstrate that the biodegradation rate of PBS in soil is highly dependent on the specific soil conditions. Moreover, it is shown that the biodegradation of PBS can be substantially accelerated by blending it with PBSA (fragmentation in 8 weeks). Finally, it is shown that the disintegration of poly(lactic acid) (PLA) in soil can be enhanced by blending it with PCL. Experiments that monitor the CO₂ evolution of these blends, both in soil and in home composting environments, demonstrate that not just the disintegration, but also the overall biodegradation of PLA is enhanced by blending with PCL (39 % conversion to CO₂ in 12 months incubation in soil; 89 % conversion to CO₂ in 6 months incubation in home composting conditions). This opens up possibilities for targeted blending strategies to reduce potential accumulation of PLA-based plastics in soil environments.