Dielectric and microwave welding

  Thermoplastics containing polar groups can be welding by techniques using radio and microwave frequency radiation. The dielectric loss in the polymer dissipates energy, heating it; application of pressure then forms a bond. Welding times are typically a few seconds. Coupling of the radiation with the polymer requires the presence of polar groups such as OH^-, NH3-etc.^[1]

Polymer fluidized-bed coating

  In polymer fluidized-bed coating the work piece, heated to 200-400℃, is immersed for 1 to 10 seconds in a tank containing coating powder, fluidized by a stream of air at 0.1-0.5 atmospheres. The hot workpiece melts the particles, which adhere to it, forming a thick coating with excellent adhesion. In electrostatic fluidized-bed coating the bed is similar but the air stream is electrically charged as it enters the bed. The ionized air charges the particles as they move upward, forming a cloud of the charged particles. the grounded workpiece but a subsequent hot curing is necessary. The precess is particularly suitable for coating small object with simple geometries.

Thick films can be applied in a single application, and the coating toughness is as good as or superior to liquid counterparts. Powder coating are available in a wide variety of glosses and texture that are packaged as “ready to use ” coatings. Powder contamination (other color post-modifcation is not possible with powder coatings as in tinting of liquid paints. Powder coating applications are those that will sustain the precessing temperatures required for polymer ,elting, curing , and film formation).^[1]