Thin plasma-polymerised layers on PET-substrates under the influence of NaOH solution

Plasma-enhanced chemical vapor deposition coatings are already used to reduce the gas permeation of polyethylenterephthalat-bottles. To apply the coatings for refillable bottles, a corrosion protection has to be developed to protect the barrier coating and the bottle. This is necessary because the SiO_x-barrierlayer has a low resistance to the NaOH solution used for the washing process.

For the experiment, PET-foils and Si-Wafers are coated. Therefore, a possible interlayer (3 nm) and barrierlayer (30 nm) are deposited with a pulsed microwave plasma. The HMDSO-based protection layer has a thickness of 30 nm. The process parameters for the corrosion protection are varied to identify a correlation between the parameters and the resistance. To assess the resistance to NaOH solution, an analysis of oxygen permeation, Fourier-transformation measurement, and SEM-examination are used. Optical emission spectroscopy is done to analyse the electron density, electron temperature, and gas temperature.

The presented results correlate the power and pulsing during the deposition process with the layers’ resistance against NaOH solution. A lower power increases the resistance. With pulsing of 2 ms/160 ms compared to 1 ms/160 ms a layer is deposited, which has a higher resistance to NaOH solution.