VEN ACTIVATE FLAME
Flame of plastic workpieces before the coating
Prior to coating plastic workpieces, they can be flame heated using a gas burner to improve their look and feel. This is not a heat treatment but rather a selective utilisation of the chemical effect of the gas flame.
Treatment of surfaces to improve the adhesion strength of glues, coatings and print media by means of flame impingement is a well-established process for some years in numerous industrial sectors.
An addition, significant improvement of the adhesion strength can be achieved by separating a reactive silicate layer, which is generated by flame pyrolysis. Very dense and adherent silicate layers with high surface energy are formed on metal, glass, ceramics and plastics by the combustion of a silane additive component in a fuel gas atmosphere.
During flame heating, the surface is briefly subjected to the direct effect of a gas flame fed with extra oxygen.
This causes the breaking of molecular bonds in the surface of the substrate to be treated, and the binding of active ions, mainly OH and COOH groups existing in the flame. In this manner, polar groups are generated in the originally non polar material, thereby allowing the secure adherence of printing inks, paints/lacquers, adhesives etc.
The formation of polar groups measurably increases the surface energy of the treated substrate.