PLATING ON PLASTICS
To plate successfully on A.B.S. (Acrylonitrile Butadiene Styrene) the
particles of Butadiene were dispersed and aligned as uniformly as possible on the surface.
Inspection by a scanning electron microscope of surfaces that were successfully plated
showed that the particles were spherical and regularly arranged. The surface layer after
being etched clear of Butadiene was left with numerous well-undercut symmetrical cavities
that provided secure mechanical keys for the metal plating. In a specimen with surface
stress (that did not plate well) the etched cavities, shallow and seldom undercut,
provided only a poor mechanical key. In addition, the stresses tended to relax during
subsequent temperature changes when the surface layer deformed thereby loosening the
Compoments were designed with the plating in mind. Good flow during
moulding was ensured with a minimum of residual stress. Holes and grooves were provided to
facilitate circulation of the plating solution. In the manufacturing process, the time and
temperature in moulding was strictly controlled, the use of silicones as mould-release
agents was avoided and the feed mechanism was very carefully cleaned after shut-downs.
Meticulous cleaning prior to etching and plating was essential. All
traces of mould-release agents and of greases were removed. Slow etching was maintained to
avoid too violent action near the undercut cavities in the surface and to improve the
accuracy of timing rinsing was thorough and finally the temperature of the plating
solution and the time of the process was strictly controlled. The chemical composition of
the solution was frequently monitored and adjusted and components were arranged in the
plating vat to allow free circulation of the solution on all sides.