Various plastic manufacturing processes rely on nitrogen. Nitrogen is one of the most commonly used gases for injection molding. As an inert gas, it displaces oxygen inside the mold and ensures the injection molding process goes smoothly. Oxygen holds moisture, so its presence inside the mold can cause defects.
Plastic manufacturers also use nitrogen for plastic extrusion. In this production method, a polymer is pressed through a long, molded shape to create a continuous form. Nitrogen displaces the oxygen in extruders to prevent damage to the product and the machine.
In gas-assist injection molding (GAIM), nitrogen plays a slightly different role. GAIM is a multistep process used for large plastic components. A major challenge in producing large plastic parts is that the formed plastic can shrink as it dries. Nitrogen is added to the mold to ensure the polymer expands to fill every cavity. This process prevents the polymer from shrinking during the cooling phase.
Liquid nitrogen is often used on rubber and plastic molded parts post-molding for cryogenic deflashing.