Balancing Degradability and Physical Properties of Amorphous Poly(d,l-Lactide) by Making Blends

The problem in using the existing biodegradable polymers for day-to-day commodity and specialty applications (non-physiological) is the trade-off between the degradability and physical properties of polymers. Therefore, the authors study the properties of polyester films made by solution blending of amorphous poly(d,l-lactide) and semi-crystalline poly(l,l-lactide) (PLLA) with an aim to achieve a good balance of mechanical properties and degradability under environmental conditions. The degradation test using proteinase K enzyme shows faster degradation of blends in comparison to homopolymers by weight loss. Faster fragmentation of blends and fragments of lower masses in comparison to PLLA is also seen in immature compost with bulk degradation as the main mechanism of degradation. A detailed investigation shows increased crystallinity and the formation of crystalline stereo-complex in fragmented samples that may limit degradation after a stage causing microplastics persisting for a longer period. Therefore, further degradation studies in compost for at least 8-10 weeks are recommended. Other environmental sinks, such as activated sludge water, fresh, and seawater, provide either extremely slow or no degradation excluding the use of such blends for applications intended for these sinks. In future, smart solutions are required to enhance the degradation of polylactide in different environmental sinks.

Automated summary

The study found that blends of poly(l,l-lactide) degrade faster than homopolymers, but still result in persistent microplastics in compost. Further research on the degradation of polylactide in different environmental conditions is recommended to find better solutions.