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. 2021 Aug:76:105627.
doi: 10.1016/j.ultsonch.2021.105627. Epub 2021 Jun 10.

Study on the influence of advanced treatment processes on the surface properties of polylactic acid for a bio-based circular economy for plastics

Georgia Sourkouni  1 , Charalampia Kalogirou  2 , Philipp Moritz  1 , Anna Gödde  1 , Pavlos K Pandis  3 , Oliver Höfft  4 , Stamatina Vouyiouka  3 , Antonis A Zorpas  5 , Christos Argirusis  6
Affiliations

Study on the influence of advanced treatment processes on the surface properties of polylactic acid for a bio-based circular economy for plastics

Georgia Sourkouni et al. Ultrason Sonochem. 2021 Aug.

Abstract

New biotechnological processes using microorganisms and/or enzymes to convert carbonaceous resources, either biomass or depolymerized plastics into a broad range of different bioproducts are recognized for their high potential for reduced energy consumption and reduced GHG emissions. However, the hydrophobicity, high molecular weight, chemical and structural composition of most of them hinders their biodegradation. A solution to reduce the impact of non-biodegradable polymers spread in the environment would be to make them biodegradable. Different approaches are evaluated for enhancing their biodegradation. The aim of this work is to develop and optimize the ultrasonication (US) and UV photodegradation and their combination as well as dielectric barrier discharge (DBD) plasma as pre-treatment technologies, which change surface properties and enhance the biodegradation of plastic by surface oxidation and thus helping bacteria to dock on them. Polylactic acid (PLA) has been chosen as a model polymer to investigate its surface degradation by US, UV, and DBD plasma using surface characterization methods like X-ray Photoelectron Spectroscopy (XPS) and Confocal Laser Microscopy (CLSM), Atomic Force Microscopy (AFM) as well as FT-IR and drop contour analysis. Both US and UV affect the surface properties substantially by eliminating the oxygen content of the polymer but in a different way, while plasma oxidizes the surface.

Keywords: AFM; CLSM; DBD plasma; FTIR; Micro-plastics; Pre-treatment of polymers; Sonochemistry; UV photochemistry; XPS.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

None
Graphical abstract
Fig. 1
Fig. 1
Schematic presentation of the treatment and characterization procedure.
Fig. 2
Fig. 2
XPS spectra of the surface indicating the composition of the PLA samples treated with different methods for 1 h.
Fig. 3
Fig. 3
FT-IR spectra of samples treated for 1 h by different methods. US at 20 kHz and its combinations with UVA (left) and US at 860 kHz and its combinations with UVA (right).
Fig. 4
Fig. 4
Absorbance of surface groups derived from FT-IR spectra. The upper X-axis indicates the treatment time, where R is the reference material. The lower X-axis indicates the vibrational group on the surface.
Fig. 5
Fig. 5
Contact angle resulting from the drop contour analysis (on both sides) of the samples treated for 1 h using US, UVA and their combinations. The line at 90° indicates the angle above which the surface is considered more hydrophobic.
Fig. 6
Fig. 6
Contact angle resulting from the drop contour analysis of samples treated using DBD plasma. The samples have been measured once again after six days to find out if the surface properties are changing with time.
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