The type of fluorination the company performs most often is adhesion fluorination. This process enables a plastic surface to be influenced in such a way that a higher polarity is obtained, the total contact area of the surface is increased as a result and better adhesion is therefore possible. This might be necessary, for example, if different layers need to be bonded at the same time, or to prepare a surface for painting or flocking, or to improve the adhesion of glue. The fluorination process is also used for hydrophilization. With this process, surfaces are equally wetted, which in turn facilitates printing or, for example, in the case of dishwasher applications, makes them easier to dry. Fluor Technik System has the capability to fluorinate nearly all plastics to minimize dynamic friction. The company can also draw on extensive experience in the fluorination of rubber and silicone.
Fig. 1: Diagram of the fluorination process flow
The fluorination process (Fig. 1) can be carried out within different systems. These either consist of a process chamber, loaded with a batch each time (offline systems), or web systems, with which plastic web material is continuously fluorinated as it passes through (inline systems). A gas mixture comprising 10%fluorine and 90%oxygen is used as the fluorinating agent. The change in the surface properties is caused by the highly reactive fluorinated gas. This replaces a portion of the hydrogen atoms in the surface material with fluorine atoms. The fluorination process is therefore a chemical reaction and not a type of coating. The depth of penetration of the fluorine atoms into the substrate is confined to the molecular level. The properties of the base material and its dimensions remain completely unchanged. Only the surface energy and the polarity are influenced by the fluorine, and these effects are lasting and stable. Through targeted process control, the fluorination results can be precisely adjusted to the base polymer and the intended application. The basic process parameters are the dwell time in the process chamber, the temperature, and the fluorine concentration, which is determined by the pressure. These parameters enter into the fully automatic process control as a "prescription". All the parts to be fluorinated therefore receive an individual "prescription" that is tailored to the base material and the intended surface property as part of a process that is always replicable.
Fig. 2: COBRA NS screw vacuum pump
"The core component of a fluorination system is the vacuum technology," says Bernd Moeller, Managing Director of Fluor Technik System. "The is because the quality of the treated parts depends on the reliability of this technology." In his fluorination systems, he only uses vacuum systems from Busch that can be run completely "dry"; that is, without any operating fluids in the compression chambers. A COBRA NS (Fig. 2) screw vacuum pump is used as a backing pump and a Panda vacuum booster is installed upstream of this. COBRA NS screw vacuum pumps were developed by Busch for the semiconductor industry. They offer a high level of process reliability and thanks to their optimized screw profile, they achieve short evacuation times. COBRA NS screw vacuum pumps are hermetically sealed and therefore no fluorinated gas can escape into the surrounding area.
Both vacuum pumps, including the drives, are water cooled, which means that the operating temperature can be precisely adjusted. Various monitoring devices report any faults that might occur as soon as they are present. The temperatures of the vacuum pumps themselves, the operating fluid in the gears and the coolant temperature are constantly measured as part of this. The quantities of coolant and oxygen used to rinse the COBRA NS once the process has finished is also monitored.
Bernd Moeller has thoroughly tested the vacuum system from Busch and is utterly convinced that it represents a robust and reliable solution. The vacuum systems are in operation between 8 and 24 hours, depending on the applicable working hours. The gears of the COBRA NS screw vacuum pumps and the gears of the Puma vacuum boosters are lubricated with perfluorinated polyethers. This ensures that the reactive fluorine cannot bond with the operating fluid. In the case of vacuum reactors that are rectangular in shape, gas circulation is required within the process chamber in order to ensure that it fills all areas completely and evenly and to guarantee homogeneous surface processing. Water-cooled Puma vacuum boosters (Fig. 3) are also used in this process and are operated independently from the vacuum system.
Fig. 3: Puma vacuum booster as a gas circulation pump on a fluorination system
Fluor Technik Systeme receives the vacuum systems that are individually adapted to the relevant fluorination systems from Busch ready for connection and installs them together with the whole system directly at the client's premises. In addition to the technical advantages of the vacuum systems, Bernd Moeller also identifies a further key benefit from collaborating with Busch: After the fluorination systems are installed, these are commissioned by Busch's own technicians and the personnel who will be operating and maintaining the systems are provided with on-site training. Because Busch has a worldwide network of companies operating in their individual countries and forming a tightly knit service network, it is able to provide a local Busch service technician for start-up and training to explain the vacuum system to the customer. Service technicians can also offer maintenance for the customer's vacuum system.
About Fluor Technik System
For around 25 years now, Fluor Technik System has been manufacturing fluorination systems in the German city of Lauterbach in Hesse that are configured to its customers' individual needs. This tailored approach does not just apply to the hardware itself. The control system that can be used to call up the different programs is also adapted in line with the parts that the customer wants to fluorinate. Fluor Technik System installs the systems worldwide and commissions them using its own technicians. As a service provider, the company also offers the fluorination of plastic, rubber and silicone parts. The firm's customers come from a huge variety of sectors, and thus parts for the automotive industry and its suppliers, medical technology, aerospace technology and "white goods" are all pre-treated using fluorination.