Before detailing the process of plastic fluorination, it is important to distinguish between fluorine and fluoride. Fluorine is a chemical element, the lightest halogen, and exists at standard conditions as a toxic, pale yellow diatomic gas. On the other hand, fluoride is a mineral that naturally occurs in foods and water and helps prevent tooth decay, which is why it is added to some toothpaste. While both are important, we will focus on fluorine and the process of fluorinating plastics.
The fluorination of plastics is the process of treating plastic materials with fluorine gas or other fluorine-containing compounds to modify the plastics’ surface properties. The goal is to boost the material’s resistance to chemicals, solvents, moisture, and temperature extremes while improving its surface energy and adhesion characteristics. The fluorination process gives drums and bottles additional flexibility, increased sealing ability, high impact strength, and stack load-bearing capability.
The fluorination process begins when the plastic items are placed into a fluorination chamber or vessel and closed tightly. Then, a vacuum pump extracts the air from the chamber. Next, the chamber is filled with a gas mixture of fluorine and nitrogen until the necessary processing pressure is achieved. The countdown begins once the required quantity of gas is in the chamber. A circulation pump is used during this part of the process to guarantee uniform gas dispersal.
The fluorine atoms then react with the plastic’s surface, replacing some of the hydrogen atoms with fluorine atoms. There are eight levels of fluorination, and each higher level offers more barrier protection against aggressive permeates.
After the plastic is treated with fluorine, the containers must be removed from the fluorination chamber. To do this, the fluorine must first be evacuated from the chamber. The gas in the chamber evacuates to a bed of activated alumina that adsorbs any remaining fluorine before venting innocuous gas to atmosphere.
The chemical modification that occurs during the fluorination process alters the surface properties of the plastic. It is made more hydrophobic, increases surface energy, and improves the plastic’s resistance to chemicals, UV degradation, and the effects of high temperatures. Notably, the fluorination process is a surface treatment, meaning that it does not alter the bulk properties of the plastic. A fluorinated surface remains stable, and the created benefits do not devalue with exposure to environmental factors and repeated use.