Results
Bottle Type 1: External Coated PET Bottles
The oxygen ingress into an external coated (blue line) and the respective reference PET bottle without coating (red line) are shown over a period of more than 25 days. In the first 48 hours the increase of the oxygen concentration in non-coated bottles and bottles with the external coating is non-linear due to the additional migration of oxygen out of the PET bottle wall. The external barrier coating reduces the rate of permeation, resulting in a significantly decreased slope compared to the slope observed for non-coated PET bottles.
Bottle Type 2: PET Bottles with External Coating and / or Different Contents of Oxygen Scavanger
Oxygen ingress into differently treated PET bottles of the same type; (A) non-coated PET bottle with 2 % scavenger, (B) external coated PET bottle with no scavenger, (C) external coated PET bottle with 1 % scavenger, (D) external coated PET bottle with 0.5 % scavenger. The combination systems (C) and (D) hold oxygen ingress to less than 1 ppm over six months, which could not be accomplished with the active (scavenger (A)) or passive barrier (external coating (B)) alone.
Bottle Type 3: Internal Coated PET Bottles
The inner coating provides an efficient barrier to oxygen (red line), and prevents oxygen desorption from the PET bottle wall into the product during the first few days of storage contrary to bottles coated externally.
In this case a thin layer of amorphous carbon, typically 100 to 200 nm thick, is applied to the inner surface of the bottle. This is deposited from high-energy plasma of acetylene gas within a high vacuum environment.
Bottle Type 4: Multilayer Bottles Containing Oxygen Scavanger
Most common multilayer structures combine two layers of PET and a middle layer of Nylon MXD6 (metaxylylene diamine nylon) in three layer structures. The high barrier material is present in separate layers which are made by simultaneous or sequential co-injection (blue line). The combination of a multilayer structure adding an active barrier within the middle layer decreases oxygen ingress significantly, which could not be accomplished with a multilayer structure without an active barrier (red line).