Recyclability of polypropylene after exposure to four different environmental conditions

Global demand for plastics, especially in the packaging sector, is increasing exponentially due to the worldwide shift from reusable plastics to single-use plastics. Packaging plastics consist mainly of polyethylene (PE), and polypropylene (PP)). Therefore, PP and PE contribute a significant portion of plastic waste polluting terrestrial and aquatic environments. In this study, the effect of UV radiation on polypropylene exposed to four different environmental conditions (air, double distilled water (DDW), potable water and saline water) was observed for 30 days. Physical, chemical, and mechanical changes were evaluated to assess the potential for mechanical recycling. Results show that all physical, mechanical, and chemical properties were severely affected for samples exposed to the air environment, followed by DDW and potable water medium, causing the material to be less elastic and more brittle. Samples exposed to saline water were found to be resistant to mechanical changes. Cracks, holes, and flakes were seen in SEM images of samples exposed to air and DDW medium, but no changes were seen on the surfaces of samples exposed to potable and saline water. Variation in surface roughness of samples with changes in their media was observed in AFM 2D topographical images. Changes observed in samples exposed to different media suggest that PP recovered from the terrestrial environment gets fragmented within 1 month making it difficult to collect and therefore, it is no longer fit for recycling. However, PP recovered from the marine environment does not deteriorate within 1 month and can be sent for recycling.

Automated summary

The study found that polypropylene exposed to different environmental conditions undergoes significant physical, chemical, and mechanical changes when influenced by UV radiation. Samples exposed to air suffered the most severe damage, while samples exposed to saline water showed resistance to mechanical changes.