Influence of Polymer Morphology in Polyethylene (PE) Materials on the Formation of Micro- and Nanoplastics

The presence of micro- and nanoplastics (MNPs) as an emerging class of contaminants has become a major concern for both the public and governmental authorities. MNPs originate from multiple sources and are widely introduced into freshwater systems. Recently, their release into drinking water from transmission pipelines has received growing attention, due to the potential health risks posed to consumers. The aim of this master thesis is to be able to evaluate MNPs release from High Density Polyethylene (HDPE) pipes to drinking water distribution networks and the relationship between the formation of those microparticles and influence of hydraulic conditions. For this purpose, a pilot-scale pipe set-up was developed to simulate a water distribution system, operating under pressure of 2 bars, flow velocity of 2.26 m/s and temperature between 25 °C and 30 °C. To assess the effects on the pipe surface over time, six HDPE pipe samples (same material as the experimental setup, but with a smaller diameter) were installed along the system. Hydraulic scouring tests were conducted for a period of 14 days. Optical Microscopy, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry (DSC) analyses were conducted to identify potential changes in the surface material after 1, 7, and 14 days of exposure. The pilot-scale testing system developed in this study, together with the sample insertion method, enabled experiments to be conducted under stable and well-controlled operating conditions. At the end of the test, qualitative analysis of SEM pictures revealed that the surface of the HDPE pipes underwent slight morphological changes, transitioning from an initially smooth and intact state to a rougher, partially peeled surface, causing the release of small fragments of plastic into the water. However, pronounced alterations in IR (Infra-Red) spectral regions, typically associated with degradation processes were not detected, suggesting that the material maintained its chemical structure. Furthermore, no significant changes in thermal properties were observed in the DSC analysis, supporting the absence of polymer degradation, despite the surface-level morphological alterations identified by microscopy.