In blow moulding, what is the parison?

• A. A rigid solid rod of polymer
• B. A hollow plastic tube
• C. A sheet of plastic used for casting
• D. A cooling chamber in the mold

Answer: (B)

A parison is a hollow plastic tube that serves as the starting material in blow moulding. It is formed from molten polymer and placed in the mold, where air is blown into it to inflate and shape it against the mold cavities, creating the hollow final part such as a bottle. The hollow nature is essential because the air pressure expands the tube to form the interior and exterior surfaces.

The other options don’t fit because a rigid solid rod wouldn’t allow inflation, a sheet of plastic is used in other forming methods like thermoforming, and a cooling chamber is a part of the tooling, not the starting material used to form the part.