03/19/2026
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Master's Thesis defense by David Nguyen on: "Expanding Plastic Waste Sources for Valorization: Statistical Analysis of U.S. Plastic Waste and Acidolysis of Multilayer Films."

Candidate Name: David Nguyen
Degree: Master’s
Defense Date: Thursday, April 2, 2026
Time: 11 a.m. - 1 p.m.
Location: ETIC - 345

Committee:

  • Advisor: Grace Chen, Ph.D., Associate Professor, Plastics Engineering, UMass Lowell
  • Margaret Sobkowicz Kline, Ph.D., Professor, Plastics Engineering, UMass Lowell
  • Nese Orbey, Ph.D., Associate Professor, Chemical Engineering, UMass Lowell
  • Hsi-Wu Wong, Professor, Ph.D., Chemical Engineering, UMass Lowell

Abstract:
Plastic pollution remains a major environmental threat. Building a circular plastics economy could cut fossil-fuel demand and reduce leakage to the environment, but many plastics aren’t recyclable because they’re multi-material (e.g., multi-layer films) or too contaminated (e.g., landfilled waste). For example, multi-layer film packaging from Meal, Ready-to-Eat rations used by soldiers are often incinerated in burn pits when landfills aren’t available, destroying valuable material. Given the scale of this waste, our work aims to enable the valorization of landfilled plastic and multi-layer films into valuable materials and chemicals.

To evaluate landfilled plastics, we will statistically analyze plastic waste from over 600 landfill-bound samples collected across the U.S. from Summer 2024 to Spring 2026, recording material and product composition to estimate the variety and abundance of plastics entering landfills. To date, the most common categories are textiles, films, and PET (in that order). We hypothesize that thermochemical conversions such as hydrothermal liquefaction (HTL) can convert contaminated mixed plastics into valuable chemicals and oils. Thus, this work will quantify the fraction of samples suitable for HTL, infer population-level composition distributions, and assess regional drivers of plastic composition.

To valorize multilayer films, we will delaminate packaging via chemolysis so recovered materials can be separated and reused as feedstocks. We hypothesize that an acidolysis-based process can be optimized and scaled. Screening carboxyl-containing reagents identified formic acid and acetic acid as most effective in delamination time (30 and 60 minutes, respectively). Using a design-of-experiments approach, the fastest conditions with acetic acid were 80°C, 80 wt% concentration, and 50 mL, achieving delamination in 75 minutes. This work will also examine effects of stirring rate and film loading and demonstrate a 10x scale-up.