Tiny Bubbles

Photograph of expanded polystyrene (plastic foam) taken through a microscope (enlarged 200 times) with a polarization filter. 

Image by Jan Homann, via Wikimedia Commons

Cups, containers, coolers, crafts: the white, light, squishy, and crumbly stuff we call “styrofoam” is everywhere. But what exactly is this stuff, and why is the mayor of New York City trying to get rid of it?

Styrofoam is a particular type of plastic foam (extruded polystyrene, or XEPS), trademarked by the Dow Chemical Company and used mainly for building insulation and crafts. The more familiar material in cups and packing peanuts is also plastic foam; its technical name is expanded polystyrene (EPS).

Styrene, the main component of polystyrene, was discovered nearly 175 years ago, but it wasn’t commonly used until the 1930s. Originally found in the resin of tropical trees, styrene is now made from petroleum by-products. Polystyrene is the hard, brittle, clear, or colored plastic used for CD cases, drink cups, and petri dishes in science labs. Any plastic item marked “6–PS” is made of polystyrene.  

It may seem strange to put the two words plastic and foam together since we usually think of plastic as being hard and shiny, not light and frothy. But this stuff is actually foamed. EPS starts as tiny pellets of solid polystyrene infused with pentane gas. When the pellets are heated with steam, the gas forms millions of microscopic bubbles, expanding the beads into “cells” of foam 40 times their original size. (These cells are the little blobs you get when you crumble a foam cup.) Then the cells are fused together, molded, and cut into many shapes and forms, ranging from flimsy take-out containers to massive, dense blocks used in construction. Learn more about the process here.

Plastic foam is not just versatile. Since it combines a small amount of material with a large amount of air (about 95% air by volume), it’s cheap, light, and a very good insulator, keeping houses warm, coffee and burgers hot, and iced drinks cold.

For decades, however, people have been concerned about polystyrene. The polystyrene manufacturing process releases chemicals into the ground, water, and air. The fumes from liquid styrene can damage the nervous systems of people who work with it. Used plastic foam takes up a lot of space in trash and landfills. And it doesn’t biodegrade, even in water; instead, it breaks up into ever-smaller pieces that can choke fish and other animals.

Expanded polystyrene (plastic foam) food packaging, thrown away outside restaurant.

Image by Nino Barbieri, GFDL, CC-BY-SA-3.0, via Wikimedia Commons

EPS is also recycled much less often than other materials, partly because it can’t be melted down and remolded like glass, metal, or some other plastics. Recycling companies have to invest in special equipment to squeeze out all the air in the foam, compacting it so it can be reused.

The problems of EPS have led many to stop using plastic foam. In 1990 McDonald’s formed a partnership with the Environmental Defense Fund, an environmental group, to cut down on the solid (nonfood) waste it produced. This included waste generated behind the counter as well as food and drink packaging. In addition to using less material, introducing reusable items, recycling, and composting, the company decided to use paper wrappings for burgers and sandwiches instead of polystyrene foam “clamshells.”

Entire communities have joined the anti-plastic foam movement. San Francisco, Seattle, and Portland, Oregon, are among the many cities, towns, and counties that have full or partial bans on EPS food and drink containers. In February 2013 Mayor Michael Bloomberg of New York City proposed a similar ban. In his State of the City address, the famously outspoken mayor said, “Something that we know is environmentally destructive, that is costing taxpayers money, and that is easily replaceable, is something we can do without. . . . And don’t worry: the doggie bag and the coffee cup will survive just fine.”

Dunkin’ Donuts issued a statement that “a polystyrene ban will not eliminate waste or increase recycling; it will simply replace one type of trash with another.” Since we keep buying food and drinks to go, they have to be put into something, but many people feel that any replacement is better than EPS. As with all environmental issues, the search for solutions continues.

Jane E. Boyd, Ph.D., is a museum curator and freelance writer in Philadelphia, specializing in the history of science, technology, and medicine. 

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