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dioxide established itself as the leading white pigment when it went into mass production in 1919. These developments in coating chemistry were paralleled (finally) by advances in coating technology. The various methods of brush application and spraying were supplemented by electrodeposition, electrostatic coating and powder coating techniques. Ambient air drying was joined by infrared and radiation drying methods (UV, electron beam), and the automation of coating processes continued to advance. It is also worth mentioning environmental technologies for the

- ciency and the so-called wrap around the work piece (see Chapter 4.3: Primers, Figure 4.4: Principle of the electrostatic coating method). For this method conductive substrates are necessary as well. The conductivity can be achieved by the use of conductive primers as explained in Chapter. 4.3. High speed bell atomizer The equipment manufacturers have further increased operating and transfer efficiencies by increasing brush speed (up to 1000 mm/s), increased fluid flows (>600 ml/min) and developed more reliable air bearing turbines so that transfer efficiency can

rather than internal charging (see above) or • insulating the entire spraying plant, including the coating supply system (a cumbersome proc- ess), or • insulating the spray gun only and supplying restricted quantities of coating by means of ”shut- tles” or similar vessels which are to be insulated separately (”canister system”) Spray application processes spray gun spray gun without electrostatic assistance workpiece coating film with electrostatic assistance Figure 6.16: Coating droplet deposition without/with electrostatic coating charging, according to [9] VIN

the barrier effect against sol- vents and inward water diffusion under humid climate conditions. Primers are made conductive by the use of conductive pigments (carbon black, doped mate- rials). Conductive primers allow the electrostatic coating of the non-conductive plastic. In the electrostatic coating process the coating is electrically charged at the atomizer (pneu- matic or high speed rotation), the work piece is grounded. The charged paint droplets move along the electrical field lines to the part where the static is discharged to the ground (see Figure 4

low contact the powder producer 4. Membrane obstructed 4. Check bottom of the bed 5. Plugged or broken membrane 5. Check the membrane C Electrostatic coating operation C1. Fluctuations in the coating thickness 1. Irregular powder feed 1a. 1b. 1c. Clean powder feed hoses, pump venturis and guns Check humidity of the air supply which can cause powder compaction Check powder free flowing properties 2. Inadequate gun distance to the workpiece 2. Readjust the distance between gun and workpiece 3. Inadequate conveyer speed in relation to the high voltage of

agents that can lead to blistering and delamination of the coating during oven drying. Increasing the electrical surface conductivity Surface conductivity (cf. DIN 53 482), e.g. for electrostatic coating, can be increased by means of the following, fundamentally different methods: • reduction of the plastic resistance in the compound • application of conductive films • technical equipment (special electrodes, special supports or holding devices for parts) which allow the charge to be discharged. Let us briefly consider just one of these: the application of

and in some cases an audible signal in the instrument. Commercial pore detectors of this type are generally now automated devices with electronic pore meters. Depending on film thickness, the applied voltage can be varied between 200 V and 15 kV, or applied in pulses of up to 35 kV in the case of very thick coatings. Thanks to their integral current limiting device, they are nevertheless perfectly safe to handle (similarly to electrostatic coating). Other instruments operate on the basis of the sponge method with conductivity detectors. In this case the

- porating an anti-electrostatic agent, most commonly on the surface. Therefore, anti-electrostatic surfaces are either manufactured from metal, or covered with an anti- electrostatic coating. Wood is often the preferred building material for con- structing a room or furniture that houses electronic equipment and flammable materials. However, wood must be treated with an anti-electrostatic agent before it can be used in applications requiring anti-electrostatic properties since wood is an electrical insulator and prone to the buildup of electrostatic charge. Graphite is