Processes

Thermoplastic Coating

Thermoplastic powders can be coated using either the fluidised bed dip coating process or by electrostatic spraying. The materials are supplied in powder (or liquid) form and are usually applied in the factory by standard fluid-bed (fluidised bed) or electrostatic spray techniques.Process methods vary. Both thermoplastics and thermosets widely used in coating of numerous materials. Roller coating similar to calendering process. Spread coating employs blade in front of roller to position resin on material. Coatings also applied via brushing, spraying, and dipping.

• Coating processes comparison

Plastic Coating Types

• Plastic powder coating
  Plastic powder coating is the process of applying a thermoplastic to the surface of metal items to provide long-term corrosion, impact and chemical resistance whilst offering an attractive decorative finish. Plastics tend to be applied a little thicker than standard paints and are generally impermeable to water or aggressive chemicals.
• Fluidised Bed Coating
  A method of applying a coating of a thermoplastic resin to an article in which the heated article is immersed in a dense-phase fluidized bed of powdered resin and thereafter heated in an oven to provide a smooth, pin-hole-free coating.
• Electrostatic spraying
  Electrostatic spraying is the most commonly used powder application method. In electrostatic spraying, an electrical charge is applied to the dry powder particles while the component to be painted is electrically grounded. The charged powder and grounded workpiece create an electrostatic field that pulls the paint particles to the workpiece. The coating deposited on the workpiece retains its charge, which holds the powder to the workpiece. The coated workpiece is placed in a curing oven, where the paint particles are melted onto the surface and the charge is dissipated.
• Flame Spraying
  Method of applying a plastic coating in which finely powdered fragments of plastic, together with suitable fluxes, are projected through a cone of flame onto a surface.
• Extrusion Coating and Laminating
  Mechanical process of building a laminate by bonding repeated laminations, or layers, of material onto one another. If the layers have a grain, such as in wood, they are often bonded with their grains at different angles to achieve greater strength in the finished material.
• Dip Coating
  Process that consists of applying a coating to a part by simple dipping in a bath. For example, this method is used to coat tools with Plastisol or to produce gloves.
• Curtain Coating
  A method of coating which may be employed with low viscosity resins or solutions, suspensions, or emulsions of resins in which the substrate to be coated is passed through and perpendicular to a freely falling liquid "curtain" (or "waterfall"). The flow rate of the falling liquid and the linear speed of the substrate passing through the curtain are co-ordinated in accordance with the thickness of coating desired.

Applications
Plastic coating are widely used in pumps, vessels, valves, and pipelines for process industries. They are used in food industries, gas, oil industries and also in water treatment industries.