As this air touches the hot plastic (molten polymer), it absorbs heat.

A complete IBC "piece" or system typically includes several integrated parts:

Numerical Study of Internal Bubble Cooling (IBC) in Film Blowing

A dedicated exhaust pipe, usually located in the middle of the die, pulls the warm air out.

In a standard blown film process, molten plastic is extruded through a circular die to form a tube, which is then inflated into a bubble. IBC systems add a sophisticated air-exchange loop inside this tube: