Which polymer is widely used in plastic bags?

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

Answer: (A)

The key idea is why a polymer works well for thin, flexible film like plastic bags. Polyethylene can be melted and blown or extruded into very thin, durable films, which is exactly what bag material needs. Its two common forms—low-density and high-density—offer different balances of softness and strength. LDPE makes bags that are very bendable and less likely to tear from folding, while HDPE provides sturdier bags that still form into film easily. This combination keeps manufacturing simple, fast, and inexpensive, with good moisture resistance and chemical stability, which is ideal for everyday bags. Because of these film-forming properties and cost advantages, polyethylene is the polymer most widely used for plastic bags. Other polymers don’t fit the same needs: polystyrene is rigid and brittle, not suitable for flexible bags; polypropylene can be used in some cases but isn’t as flexible or economical for thin film; PVC raises environmental and processing concerns and isn’t preferred for common bag use.