Ultralong Lifetime of Active Surface of Oxygenated PET Films by Plasma-irradiation and Bonding Elements

Abstract

Biaxially oriented polyethylene terephthalate (PET) films can be bonded directly by oxygen plasma irradiation and low temperature heat press around 100°C. The irradiated films were kept in the atmosphere for six years, yet they can be bonded tightly as well. Dry-and wetpeel tests indicate that two bonding elements can be suggested, hydrogen bonding and chemical bonding. The films are bonded by these two elements at lower temperatures, but by the pure chemical bonding at higher temperatures. FTIR results on the non-irradiated, irradiated and bonded samples indicate that OH and COOH groups are created at the surface, they are responsible for the hydrogen and chemical bondings. Dehydrated condensation reaction is proposed for the chemical bonding. It is briefly mentioned on two origins for the long lifetime of irradiated active surface.

Water adsorption and desorption on plasma-activated PET film surface, indication of hydrogen bonding

“…It indicates a very small absorption on the lower-k side caused by the plasma-created COOH in the case of plasma-irradiated PET. 5,[13][14][15][16] Then, we know from the previous results 5, [13][14][15][16] that the COOH groups are formed on the irradiated surface. The absorptions due to water (H 2 O) and the OH group appear at approximately 2700-3800 cm ¹1 ; these absorption spectra are magnified and shown in Fig.…”

“…The above results are important for clarifing the mechanism underlying the ultralong lifetime of plasma-induced bonding ability of the PET and other plastic films, we have reported so far. 5,[13][14][15][16] Usually, the lifetime of plasma effects on the plastic films is very short, that is, only a few days. 23) The predominant mechanism proposed for the short lifetime is that the plasma created surface functional groups, such as OH, COOH, and C=O, penetrate inside of the plastic materials.…”

“…However, we have to collect the organic solvents in used lamination processes, because they cause environmental problems. 12) We demonstrated the direct bonding between PET and PET, [13][14][15][16] and PET and other plastic films 4) by a plasma irradiation technique and low thermal press 5,[13][14][15][16] without using any glues. The bonding force is stronger than the film cohesion force, as demonstrated in Fig.…”

“…5,13) We propose that the mechanism of bonding involves dehydrated condensation reactions between the plasma-created active OH and COOH groups 17,18) at the interface of two irradiated films under the low temperature press. [13][14][15][16] It was found that this plasma irradiation effect on bonding capability can be maintained for more than six years when the irradiated films are kept in the normal atmosphere. 5,14) One of the origins might be the finding that the irradiated surface having the OH and COOH groups is overspread with atmospheric water.…”

“…[13][14][15][16] It was found that this plasma irradiation effect on bonding capability can be maintained for more than six years when the irradiated films are kept in the normal atmosphere. 5,14) One of the origins might be the finding that the irradiated surface having the OH and COOH groups is overspread with atmospheric water. 5,19) Then, in this work, we investigated the activity of irradiated surface of PET films in terms of water adsorption and desorption on the surfaces of films.…”