Quality assurance for barrier coatings
Problem: Determining the quality of SiOx barrier coatings for plastic cups
Many packed foodstuffs must not be allowed to oxidise and the water content must not change if the contents are to remain palatable. The penetration of oxygen and moisture also enable the growth of bacteria and mould, and eventually results in spoilage of the packed product.
By means of plasma polymerisation, plastics packaging that otherwise has only a minor barrier effect can be provided with a coating with superior barrier properties (frequently SiOx). The producer of the plastic cups will generally have the coating process carried out by an external company but does not have any possibility to evaluate its quality. Because of the transparency and low layer thickness of the coats (around 20 nm), the coatings cannot be checked visually.
Methodology: Identification and description of the individual coats, plus benchmarking by comparing the coatings with systems specially developed at IKV for this type of application
- Quick test to identify the individual coats in the system by means of infrared spectroscopy
- Coat adhesion measurements using an adhesion analyser and comparison with empirical data from IKV for this type of coating
- Coating of similar cups at IKV to produce a reference
- Comparison of the attained barrier improvements
Result: Adequate quality of the supplier's coatings confirmed
Through this quick test, an SiOx coating was identified on all the supplied specimens. The adhesion measurements resulted in adequate values for the application.
The barrier improvements attained by the supplier's coatings are almost identical to those that can be obtained with the coatings developed at IKV.
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