School of Graduate Studies

School of Graduate Studies
School of Graduate Studies

A less wasteful plastic bag – Meet Steacy Coombs

Masters student in the Department of Chemical Engineering  

by Phil Gaudreau, October 2020

Steacy CoombsHave you ever wondered what goes into some of the plastic products we use every day?

Single-use plastic bags consist of high-density polyethylene, a type of polymer. As anyone who has ever put something sharp or heavy in a plastic bag knows, these bags are not very durable.

 This is because high-density polyethylene has what chemists call a linear macromolecular structure. Think of it like a bridge with no supports–its lack of branching means the molecules, and therefore the bag, are not very durable.

In comparison, low-density polyethylene, which is used for food packaging and plastic wrap, has many branches in its macromolecular structure, making it much more flexible.

Getting the right macro molecular structure when making polymers can involve a lot of trial and error in manufacturing. Steacy Coombs, Sc'19, hopes to change that.

“Typically in the industry, the materials are made before the process is known,” says Coombs. “They make the material and hope it works. It can take multiple batches and trial and error to figure out whether it’s actually going to work for what they want to do.”

Her research studies the structure of polymers and how it affects the processability and rheological properties.

Under the supervision of Jeffrey Giacomin, Queen’s Engineering and Applied Science Professor and Canada Research Chair in Rheology, Coombs has investigated specific macromolecular architectures to determine the properties before that polymer is ever even manufactured or invented. The end goal is to reduce the waste that is produced during the creation of plastics and polymers.

It was in Coombs' fourth year of chemical engineering that she became interested in polymer science following a conversation with Dr. Giacomin.

“My interest in research grew while I was part of the Queen's Biomedical Innovation Team in my third year,” Coombs says. “That led me to complete a research internship at DuPont and a thesis project, which then made it easier when I decided to pursue a masters.”

She didn’t immediately turn that passion into a graduate study program, however. After completing her undergraduate degree, Coombs worked in industry for a couple of years before her job was eliminated during COVID-19 cutbacks.

After being laid off during the pandemic and with few job prospects, she reached out to Dr. Giacomin in the spring and started volunteering to help with his research. Through this opportunity Coombs was able to publish some of her own research, preparing her for her masters studies in the fall. This head start means Coombs is optimistic she can fast track her two-year masters and complete it in half the time.

“Hopefully, we’re far enough along in our research that I am able to defend this spring,” says Coombs.

Once her masters is complete, Coombs plans to complete her PhD. This will allow her to pursue a teaching position, or possibly academic consulting, in order to increase female representation in academia.

To learn more about graduate programs with the Queen’s department of Chemical Engineering, visit their website.