Page 271 - Handbook of Adhesives and Sealants

Surfaces and Surface Preparation 239

have also been treated with corona in environments other than air.
Metal foil surfaces have been treated with corona, but the effect is
only moderate, probably due to removal of organic contaminants by
the oxidizing exposure.

6.5.2.2 Flame treatment. Flame treatment consists of exposing a sur-
face to a gas flame for less than several seconds. Flame treatment
burns-off contaminants and oxidizes the surface of the polymer similar
to corona treatment. Flame treatment is used as a surface treatment
for many low energy polymeric parts prior to bonding, printing, or
painting. Figure 6.11 shows the flame treatment of a plastic bottle.
Flame treatment is believed to provide a polar surface that is con-
ducive to adhesion. A brief exposure to the flame oxidizes the surface
through a free radical mechanism, introducing higher surface energy
groups (hydroxyl, carbonyl, carboxyl, and amide groups) to the part’s

Figure 6.11 Flame treatment of a plastic bottle. The treatment will depend on
the gas mixture and flow rate, position of part relative to flame, and exposure
time.