This experiment began as an initiative by the Center for Sustainable Polymers (an NSF CCI Center) to bring the topics of polymers and the environmental concerns of plastics into the high school classroom. The unique and versatile properties of polymers allows for design and mechanical testing, thus the opportunity for introducing engineering principles set forth in Next Generation Science Standards (NGSS).
The discovery that purchased pellets of poly(ε-caprolactone) (PCL), a degradable plastic, can be melted and pulled into thin, flexible threads catalyzed the idea to connect degradable plastics with absorbable medical sutures and non-degradable plastics with non-absorbable sutures. The versatile, multi-part experiment subsequently designed includes:
- pulling sutures from different molecular masses of PCL;
- comparing their tensile strength with three types of purchased real medical sutures;
- exploring their rate of degradation in aqueous base.
A fourth inquiry-driven module allows students to design their own polymeric mixture by melt blending PCL and commercially available compostable consumer products derived from poly(lactide) (PLA).
Our experience from implementation of the medical sutures experiment in outreach programs, high school classrooms, and a college environmental science course is that students acknowledge the prevalence and alarming accumulation of plastics on land and in our water and feel it is a compelling societal/sustainability problem to be solved. Discussions of how green chemistry principles are being applied by scientists to synthesize plastics from renewable feedstocks, like corn, and design them for degradation are a natural extension of the experiment. Fun- the threads can be pulled across classrooms – Engaging – data collection and analysis - Relevant – from cell phones to sneakers, plastics are here to stay, and – Green Chemistry – a strategy for a sustainable solution.
This work was funded through a grant from the Minnesota Pollution Control Agency Grant – Swift # 52526 which supported co-author Deborah K. Schneiderman who discovered that threads could be pulled from PCL. Further development was funded by the University of Minnesota Center for Sustainable Polymers under Grants CHE-1413862 & CHE-1136607, and the Research Experiences for Teachers (RET) Program of the National Science Foundation under Award Number DMR-1559833. We also acknowledge St. Paul Central High School teachers Craig Karlen and Alka Goyal for early testing and feedback for this experiment, Michael Wentzel from Augsburg College, and students of Cassandra Knutson’s AP chemistry classes spring 2016 and fall 2016.