However, in our process, adhesion between the polymer film and the steel sheet was achieved by a postheating treatment after the nip exit thanks to infrared ovens, which leads to a very good final adhesion.
We can then assume that the postheating step will induce blowing of the entrapped air and coalescence of different microbubbles to develop finally macrobubbles.
We have noticed that the postheating stage has a decisive effect on the quality of the coated substrate.
Each sample is thus designated first by a figure, corresponding to a set of conditions listed in Table 3, and then by a letter A or B, giving information on the existence or not of a postheating stage.
For A-type samples (without postheating stage), it seems that no bubbles at all are observed.
After the postheating stage, bubbles are observed on B-type samples.
All the corresponding samples obtained after postheating stage (Samples 4B, 5B, and 6B) show some bubbles.
After the postheating stage, it seems that the bubbles are more numerous and bigger when the film is thinner (Sample 11B).
Other web process heating applications include curing, preheating, postheating
, thermal bonding, laminating, fusing and sintering.