Why does plastic become brittle?
Show answer & explanation
Answer: UV breaks molecular chains
Plastic dries out over time — Wrong. Plastic doesn't contain water to dry out. The brittleness comes from chemical changes in the polymer structure.
UV breaks molecular chains ✓ — Correct! UV light breaks the long molecular chains that make plastic flexible. Shorter chains can't bend without breaking. Heat and oxygen also contribute. That's why outdoor plastics degrade faster!
Cold temperatures freeze it solid — Wrong. Cold can make plastic temporarily stiffer, but that's reversible. Permanent brittleness comes from UV light breaking polymer chains and plasticizers evaporating over time.
Go deeper: UV degradation
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