Dehesive coating for packages

When flowable goods such as food or personal care products are removed from their containers, up to 20 percent of the original contents can remain in the packaging. Besides the economic loss to consumers, these residues negatively impact recycling: higher costs arise for additional energy, time and water required, and, if the products in question are pharmaceuticals, chemicals or pesticides, the rinsed-out leftovers also have to be disposed of in a suitable manner.

Fraunhofer IGB has developed surface modifications for packaging materials that lead to decreased adhesion of contents. The research forms part of a joint project with the Fraunhofer Institute for Process Engineering and Packaging IVV (Freising near Munich) and several industrial partners, funded by the German Ministry of Education and Research.

The aim is to reduce the amount of residues left in the packages by at least half. At the same time, this additional function must not negatively affect the packaging’s basic mechanical or barrier properties or other aspects of its processability. Product safety is also paramount.

Plasma process enables nano-coatings

The surface modifications are applied using low-pressure vacuum plasma (PECVD) processes, where very thin polymeric layers are deposited on the inside of the packaging during the gaseous phase. The layers are typically thinner than 50 nanometers, while the required thickness of the coating depends on the roughness of the packaging material and can be adjusted by varying process parameters such as pressure, gas flow, or treatment time.

To achieve dehesive properties, the interaction forces between package surface and fill goods must be minimized. This effect can be obtained by creating coatings with specific chemical composition and adapted physical properties. We evaluate predominantly hydrophobic coatings (e.g. silanes, siloxanes, fluorosilanes, and fluorocarbons).

Evaluation and scale-up

In preliminary laboratory experiments, plasma coatings were applied to packaging surfaces and the properties of these coated surfaces are evaluated. Experiments to measure the ability to remove products from these coated surfaces were carried out using a purpose-built test stand. This allows correlation of surface properties with the adhesion of contents to the surfaces in question. Coatings that show much better results and reduced residual amounts have already been identified.

The focus of further collaboration with our project partners was on scaling up from lab bench to full-size industrial production.