Biofilms on Plastics Slow Photo-Oxidation while Promoting Surface Degradation

Area of Science:

• Environmental science
• Materials science
• Microbiology

Background:

• Plastic debris in natural environments undergoes aging.
• The role of biofilms in plastic weathering is not well understood.

Purpose of the Study:

• To investigate the influence of biofilms on the weathering of polyethylene terephthalate (PET) under UV irradiation.

Main Methods:

• PET bottles were exposed to freshwater to form biofilms.
• Biofilm-covered PET was subjected to UV irradiation.
• Surface morphology, roughness, crystallinity, and mechanical properties were analyzed.

Main Results:

• Biofilms intensified UV-induced surface alterations and increased roughness significantly (from ~22 nm to ~874 nm).
• Biofilms increased brittleness and reduced impact strength, facilitating deeper UV penetration and cavity formation.
• UV exposure alone caused photo-oxidation and increased hydrophilicity, while biofilms showed a dual protective/aggressive role.

Conclusions:

• Biofilms have a complex, dual role in plastic weathering, acting as both protectors and aggressors.
• Biofilm-induced degradation can enhance plastic fragmentation and potentially influence additive leaching.
• Plastic weathering in natural environments is more complex than in laboratory settings with pristine materials.