Amorphous polymers solidify through molecular entanglement and glass transition rather than neat crystallization.

When liquid water cools, its molecules quickly line up in perfect rows to form ice. Many polymers cannot do this. Their chains are too long, bulky, and awkward to arrange themselves quickly. Instead, as they lose heat, their motion slows down. The chains simply drape over one another, tangling hopelessly. This messy state is called amorphous. As temperature drops further, the polymer crosses a vital line called the glass transition temperature. Below this point, there is not enough thermal energy for the chains to slide past each other. They lock in place, turning a soft, gummy liquid into a hard, rigid solid.