Optimization of PLA foams produced by supercritical method

Concerns about the environmental impacts caused by the improper disposal of solid waste have become increasingly discussed in academic and industrial circles. Contamination of the environment, especially by microplastics, is a major concern, as these microscopic particles can enter the trophic chain, affecting various organisms, including humans.

As an alternative, the use of plastics from renewable sources and with a higher biodegradation rate has been gaining prominence in research. Poly(lactic acid) (PLA) is one such material. However, PLA has disadvantages such as low elasticity in the molten state, which is crucial for foaming processes, and a slower biodegradation rate compared to other biodegradable polymers. To overcome these challenges, chemical modification and the introduction of fillers are viable alternatives.

In this context, the main objective of this research was to study the influence of chemical modification and the introduction of cellulose nanocrystals (CNC) on the properties of PLA, with a view to producing foams using supercritical CO2 as the foaming agent. For the chemical modification of PLA, GMA was used as the modifying agent, in the presence of peroxide as the initiator. As for the strategy for incorporating fillers, the CNC was chemically modified by mechano-chemistry, using octadecyl n-isocyanate as a modifying agent to increase compatibility with the PLA matrix.

The results showed that the chemical modification of PLA resulted in significant changes in the cell structures of the foams, while the introduction of CNC in higher concentration resulted in smaller cell structures.

Thesis available on: https://cnrs.hal.science/LGP2/tel-04783407v1