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Influence of addition of organic fillers on the properties of mechanically recycled PLA


Poly(lactic acid) (PLA) is one of the most used biobased and biodegradable polymers. Due to their high stability, some of the newest grades of PLA are only degradable under severe industrial conditions. For these grades, mechanical recycling is a viable end-of-life option, with great environmental advantages. However, the polymer undergoes degradation during its service life and in the melt reprocessing, which leads to a decrease in properties that can compromise the recyclability of PLA. The goal of this work was to evaluate the usefulness of adding small amounts of two organic fillers, chitosan, and silk fibroin nanoparticles, during the recycling process for improving the properties of the recycled plastic. The degradation level of the aged polymer and the nature and amount of filler affect the performance of the recycled plastics. The fillers reduce the degradation during the melt reprocessing of PLA previously subjected to severe hydrolysis, thus increasing the intrinsic viscosity of the recycled plastic. A careful selection of the added organic filler lead to recycled plastics with improvements in some key mechanical, thermal, and barrier properties. Thus, the use of organic fillers represents a cost-effective and environmentally sound way for improving the mechanical recycling of bioplastics.

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Fig. 8



Poly(lactic acid)


Silk fibroin nanoparticles


Silk fibroin


Scanning electron microscopy


Differential scanning calorimetry


Thermogravimetric analysis


Water vapor transmission rate


Silk fibroin nanoparticles obtained by acid hydrolysis


Silk fibroin nanoparticles obtained by desolvation


Fourier-transform infrared


Attenuated total reflectance

T g :

Glass transition temperature

T cc :

Cold crystallization temperature

T m :

Melting temperature

ΔH cc :

Cold crystallization enthalpy

ΔH m :

Melting enthalpy

X c :

Crystallinity degree

T 10 :

Temperature at which 10% of the mass

T max :

temperature of maximum degradation rate


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The authors would like to thank the Institute of Polymer Science and Technology (Madrid, Spain), for collaborating in the SEM measurements.


This work was supported by MINECO-Spain (project CTM2017-88989-P), Universidad Politécnica de Madrid (project UPM RP 160543006), and the European Commission (Horizon 2020, project 860407-BIO-PLASTICS EUROPE). Dr. Lozano-Pérez’s research contract at IMIDA was partially supported (80%) by the ERDF/FEDER Operational Programme “Murcia” CCI N° 2007ES161PO001 (Project No. 14-20/20).

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Correspondence to Joaquín M. Martínez Urreaga.

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Beltrán, F.R., Gaspar, G., Dadras Chomachayi, M. et al. Influence of addition of organic fillers on the properties of mechanically recycled PLA. Environ Sci Pollut Res 28, 24291–24304 (2021).

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  • Poly(lactic acid)
  • Mechanical recycling
  • Silk fibroin nanoparticle
  • Chitosan
  • Gas barrier properties
  • Mechanical properties
  • Thermal properties