Flame Treatment Meets Quality Management, 2002 PLACE Conference Proceedings

Flame treatment is used since 50 years as a method of improving the adhesion on plastic and paperboard surfaces. The range of applications is as wide as the range of plastics processing itself, it is used for pretreatment of bottles and containers, household parts, automotive components, medical products as well as in web applications such as blown and cast film pretreatment, laminations and paperboard treatment prior to extrusion coatings.

The treatment is effected by direct exposure of the substrate to a gas flame for a short period of time. The flame carries some excess oxygen, which takes part in the combustion, building intermediate products in form of active ions such as hydroxyl and carboxyl groups. These ions are bound into the surface, thus building polar groups, which enable a reaction with the coating to be applied. Therefore, flame treatment is not a heat application, but the controlled use of a chemical property of the flame.
The parameters, which define the efficiency of the treatment, are:

1. The burner design
2. The air/gas-ratio of the flame
3. The power output of the burner
4. The distance from the burner to the surface
5. The speed or the dwell time of the flame on the substrate