Which polymer is used to make Styrofoam cups?

• A. Polystyrene
• B. Polyethylene
• C. Polyvinyl chloride
• D. Polytetrafluoroethylene

Answer: (A)

Expanded polystyrene foam is used to make Styrofoam cups. Polystyrene is a polymer built from styrene units; when processed into small beads and heated with a blowing agent, those beads expand and fuse into a light, insulating foam full of tiny air pockets. Those air pockets slow heat transfer, so beverages stay at the desired temperature longer while the cup stays stiff enough to hold liquid. This combination of low weight, good insulation, and low cost makes polystyrene ideal for disposable cups. Other common plastics have different uses: polyethylene is flexible and widely used for bags and bottles, vinyl chloride is durable for pipes and siding, and PTFE (Teflon) handles high temperatures and nonstick needs but is expensive and not suited for foam cups.