Ask A Scientist
Question: Why is it that chewing gum doesen’t melt or even burn very well when put into an open fire (like a campfire)?
Asked by: Shannon Constable
School: Sidney High School
Teacher: David Pysnik
Hobbies/Interests: Member of future Farmers of America, loves the outdoors and Horseback riding
Career Interest: veterinarian
Answer from Kenneth McLeod
Professor of Bioengineering, Binghamton University
Ph.D. School: Massachusetts Institute of Technology
Research Area: The behavior of complex systems, in particular, the behavior of living tissue with respect to growth, adaptation and repair
Interests/hobbies: Snowboarding, gardening, home remodeling.
Family: Wife Suzanne - son K.C., 18, and daughter, Juliana, 10
Good observation Shannon. If it doesn’t burn, it must contain something that is resistant to high temperatures, and the core ingredient of gum has exactly that property. This component is butyl rubber and it is used in all chewing gums. Don’t worry, this chemical has been approved as edible. In addition to its heat resistance, butyl rubber has another important property which we make use of in gum. Its most important property is that it is the best sealant of all the known rubbers. Butyl rubber holds air 13 times better than natural rubber. As a result, the major application of butyl rubber is in the lining of tires. When butyl rubber was first discovered (in the late 1930s) it was primarily used to make inner tubes for tire, but now that there are tubeless tires, butyl rubber is incorporated into the tire on the inside. Because we have butyl rubber on the inside of our car tires, we don’t have to put air into our tires every day. But, from a gum point of view, the great thing about butyl rubber is that it lets us blow giant bubbles! Butyl rubber is a great material, it has excellent resistance to aging, weathering, chemicals, moisture, ozone, and tearing. It does not bounce at normal environmental temperatures, which makes it a great shock and vibration absorbing material, and best of all, the raw materials are plentiful, easily obtained, and cheap. Another important property of butyl rubber is that it is blood compatible. This feature allows it to be used in biomedical applications such as artificial joint materials.