10/30/2026
By Marley O'Neil

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a master's thesis defense by Olivia Hosterman for “Investigating the Interactions Between Riverine Water and Biofilm Growth on Plastic Films.”

  • Defense date: Tuesday, Nov. 10, 2026
  • Time: 11 a.m. – 12:30 p.m.
  • Location: Ball Hall 302

Committee

  • Advisor: Grace Chen, Ph.D., Associate Professor, Plastics Engineering, UMass Lowell
  • Akshay Kokil, Associate Teaching Professor, Plastics Engineering
  • Margaret Sobkowicz Kline, Professor, Plastics Engineering, UMass Lowell
  • Collin Ward, Associate Scientist, WHOI

Abstract

Plastic pollution is an ever-growing concern within our water systems and environment, yet the interactions between waterways and plastic are still unknown. This research aims to understand the degradation of polypropylene (PP) films in riverine water by varying the light sources: ultraviolet A (UVA), complete darkness and natural light. To accelerate degradation and biofilm growth, the temperature varied between room temperature, 22°C, and an elevated temperature of 33°C. Through the immersion of the films in riverine water samples collected from the Merrimack River, the properties of the films were tested to document changes in the physical, mechanical, chemical and surface properties of the films, as well as to observe the subsequent growth of biofilm on the surface. Measurements of physical properties such as weight and thickness were collected to see if any notable degradation took place. Differential scanning calorimetry (DSC) was completed on select samples to calculate the change in the film’s crystallinity. Tensile testing of the films took place to observe the change in modulus throughout the sampling periods as well as probe for potential bulk degradation. Changes in the chemical properties were identified through Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR). Surface properties such as contact angle, scanning electron microscopy (SEM) and atomic force microscopy (AFM) documented the surface, visualized biofilm growth and determined the effect on the surface. Over the 24-week immersion period, under UVA light at 33°C, less biofilm growth was observed compared to the dark environment at 33°C and the natural light tank at room temperature, resulting in a lower contact angle. UVA light has been known to be used for water disinfection, resulting in lower amounts of biofilm accumulated on the film surface. Even the smallest amounts of biofilm can affect the contact angle of the surface due to the hydrophilic nature of biofilm. Overall, these findings demonstrate that environmental conditions, particularly light and temperature, influence biofilm formation and surface changes in PP films, providing insight into the intricate pathways leading to plastic degradation in natural riverine environments.