The powder coating of wood and wood composites

摘要

Powder coating is a technique whereby "dry paint" is electro-statically applied (by Corona or Tribo techniques) to,in the main,metallic substrates.After electrostatic spraying the ground powder could be described as a high Tg (>40°C),non cross-linked,non-coalesced particulate film.This loosely coherent layer is then fused by thermal energy to form a highly viscous 'liquid coating',having a melt viscosity many orders of magnitude greater than for a solvent borne coating processed at the same temperature.This highly viscous material then increases in viscosity,as it cross-links,to form a three dimensionally cross-linked,tough,chemically resistant film.This film exhibits excellent mechanical properties when all cross-linked functional groups are cross-linked to about 90% conversion.