How the Plastics Industry Uses Nitrogen
It’s hard to imagine a life without plastic. It’s everywhere you look, from the disposable coffee cup sitting on your desk to the plastic bag holding your favorite midday snack. Given the prevalence of plastic in our daily lives, it’s not a surprise to learn that the plastics industry makes up 14.,2% of the manufacturing sectors contribution to South Africa's GDP. It might be surprising, however, to learn that a key element that keeps this busy industry up and running is nitrogen!
How is Nitrogen Used in Plastics Manufacturing?
Nitrogen is a gas that is used extensively because it is inert and dry, meaning it’s extremely beneficial in maintaining the integrity of products and processes. In plastics manufacturing, N2 helps maintain the polymer’s integrity and strength, as well as assists in preventing any type of discoloration/oxidation that might otherwise occur.
- Injection Molding. One thing you don’t want to happen when creating and molding plastics? Contact with oxygen, which can lead to the discoloration and oxidation mentioned above. Nitrogen displaces any oxygen that exists in the mold.
- Gas Assist Injection Molding (GAIM). While a similar process to injection molding, gas assist injection molding is an application that involves multiple steps and focuses on the creation of large/thick plastic parts. The first step is simple – partially filling the mold with the polymer. In order to ensure that the formed plastic doesn’t shrink during the drying stage, the partially filled mold is injected with high-pressure N2; the polymer then expands, filling the entire mold, and doesn’t breakdown or shrink during cooling.
- Plastic Extrusion. This process results in plastic pipes and tubing – and even items like weather stripping. Raw plastic material is melted and pressed through a die. This creates a long, continuous shape that’s in the shape of a tube. Like with other plastics applications, nitrogen displaces the oxygen. This prevents the formation of any residue, as well as prevents any harm to the equipment and end product.
- Tank Blanketing. Before being sent to the molding process, molten plastic is placed in a tank. Gaseous nitrogen then blankets the tank, ensuring that the polymer does not come into contact with oxygen (essentially purging the oxygen away from the polymer).
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