Polyolefins are naturally permeable to certain gases and liquids. The volatilization of ingredients through the walls of plastic containers, however, presents problems. This can be prevented by barrier fluorination because it optimizes the uppermost monomer layers of plastics by means of a substitution reaction of hydrogen by fluorine atoms. It can be used inline as well as offline.
This form of plastic pretreatment is absolutely consistent, since it is carried out in a vacuum as well as in overpressure and thus has a geometry-independent and three-dimensional effect. The process is reproducible and cost-effective.
Barrier fluorination forms barrier layers on plastic surfaces, preventing permeation of volatile hydrocarbons. The products in the vacuum chamber are exposed to an atmosphere of a fluorine-nitrogen mixture (F2/N2). For best results, treatment duration, fluorine concentration profile, and process temperature are selected to meet the product and treatment goals. Due to the above-mentioned process conditions, the fluorine atoms are uniformly attached to all of the resulting radical sites of the plastic surfaces. As a result, the plastic surface is “densified” at the molecular level, so that the molecules of the fillers barely penetrate through the wall of the plastic container, meaning that permeation is reduced.