What’s the difference between styrofoam and polystyrene, anyway?
It really sticks in the craw of Dow Chemical that we call foam food containers “Styrofoam,” despite the fact that Dow has trademarked that name for more than 60 years.

گروه تولیدی ایران ورق

In a 2013 Washington Post article, Dow’s business director for building solutions in the Americas, Tim Lacey, sounded like he was at the end of his foam-laced rope.

“We’re doing everything we can to make sure that it’s used properly,” Lacey explained. “We don’t really know why everyone wants to land on the name Styrofoam, and why it serves as something people want to misuse.”

That’s because, when you’re using a cup, plate, or other material, you’re using a material that’s actually called expanded polystyrene. And as Dow Chemical and Owens Corning, the two primary manufacturers of extruded polystyrene, will tell you, it’s not a small or modest difference.

In a lot of ways, the process used to make a cup, versus building insulation (the primary modern use of extruded polystyrene) is the difference between a million pieces of foam and a solid brick. The cup you grabbed from the Shell station? That’s built using a molding process, in which relatively malleable balls of polymer are pressed into a specific shape after those polymers have been filled with gas. (Larger balls might be used for coffee cups, smaller ones for foam trays.)

As a result, there’s a lot of air in there, which makes the cup lightweight and flexible, while still gaining the insulation advantages that come with foam.

The problem is, there are cases where you can live with a little more weight and a little less flexibility, because you want the resulting material to be a lot stronger. That’s where the extrusion process comes in.

A good way to explain this is to go back to the way cheese curls are made, because those also use an extrusion process, except with flakes of corn instead of polymers of styrene oil. But there are some differences, however: You want air in your cheesy poofs, so you pop them straight out after they’re ready to puff up.

But let’s say you want to extrude something that was more crisp, closer to a tortilla chip than a Cheeto. You’d have to figure out a way to more tightly control how the extrusion process manages air to achieve more concentrated results. With Styrofoam, the extrusion process is managed in this way, designed to minimize the amount of air that gets through the material, so as to make the material very tough.

The result of this is that the material you get with extruders is designed for longer-term uses, like in houses. This clip from Owens Corning does a good job explaining why extrusion is desirable in the case of building materials: Simply, it’s tougher, because there’s less air than you’d find in expanded polystyrene. Because there’s less air, it’s very difficult for water to seep in through such material.

Building materials are meant to hold up for decades or longer. Single serving food? It only has to hold up as long as your delivery driver takes to get the Ethiopian food delivered to your door without the driver getting tsebhi birsen all over their vehicle.

The problem is, of course, it lasts a lot longer than that.

“The possibilities for various creations of Styrofoam, in its many shapes and sizes, are unlimited. It is our intent to offer suggestions for a variety of exciting experiences with this medium as an art form, to whet the appetite of the reader to create and to stir his imagination to devise and find his own mode of expression.”
— A passage from Creating with Styrofoam and Related Materials, a 1970 book for children that discusses the possibilities for using polystyrene in crafting—particularly by recycling used meat trays, packing materials, and other and turning them into works of art. After World War II, crafting and decoration were actually original uses for Styrofoam, particularly around Christmas.