This reading explores two facets of polymer degradation, plastic waste and medical use of biodegradable polymers. The first section, dealing with the issue of plastic waste, is meant to encourage students to act responsibly and realistically by critically exploring the different sides of the issue. As the reading points our, out petroleum supply is finite. While this thankfully limits the amount of petroleum-based plastic waste that can ever be produced, the students should understand that the finite petroleum supply also makes plastic waste a less-than-wise use of a nonrenewable resource. This reading is meant to encourage responsible use of plastics, and to this end it can be tied to the next reading, What Do Those Triangles Mean?
The section discusses a potential solution to both the problem of plastic waste and the problem of our limited supply of petroleum for making plastic. The polymer, poly(lactic acid) or PLA, which is biodegradable and made from a natural resource, is presented as an example of the role of science in solving the problems that science sometimes creates. The drawbacks of the material are also discussed.
The second section discusses an alternative to PLA, poly(3-hydroxybutyric acid), or PHB. PHB itself is not a particularly good plastic, but copolymers and other PHB derivatives can be produced by genetically engineered bacteria, and these show potential as plastic materials. But the main focus of the section is the medicinal use of biodegradable polymers. The two uses mentioned explicitly are degradable mechanical supports and controlled drug release.
Relevant National Science Education Standards
Science and Technology — The reading explores the technology of biodegradable plastics.
Science in Personal and Social Perspectives — The reading deals with polymers and issues of environmental quality wise use of natural resources. It also discusses how chemistry can help solve environmental and natural resource problems.
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