Novia UAS and Tampere University met again as part of the collaboration around their anti-icing coating. This time it was planned to do the measurement of the woodchips adhesion by shear test from the previously coated boxes and the centrifugal adhesion test from the coated sample plates.
Researchers Katrin Asplund and Julien Walser from Vaasa drove to Tampere for a week to proceed to the experimentations with woodchips and coated boxes. The experimentations took place at Tampere University ICE laboratory in the cold room set at -10°C and around 40% humidity. There were 6 tests with the boxes, different polyethylene (PE) surfaces and 2 steel boxes sprayed with coating. The measurements were recorded at room temperature to determine how long it would take to separate the frozen woodchips from the boxes. A pressure was applied every 5min by a Kern-SAUTER FK 25 force gauge to determine also the force needed to remove the wall.
Centrifugal ice adhesion tester CAT is used to determine the adhesion. In principle, this machine shows the relation between the adhesion strength of an ice cube frozen on the CAT blade and the rotation speed at a constant angular acceleration. When the samples detach, they hit the dome and activate a sensor recording the time and the rotation speed.
With smaller sample sizes, the CAT allowed more testing. Altogether, 9 surfaces were tested with similar surfaces as in the box tests, e.g., polyethylene surfaces, steel surface with added chemicals and Teflon tape for reference. A cube of woodchips and water mixture were frozen on top and then put in the CAT to determine the adhesion.
Measurements show promising results concerning surface coating for frozen woodchips adhesion on containers. Simple solutions, like environmentally friendly or antifreeze lubricants, keeping a liquid layer between woodchips and surface at cold temperature are a good step forward. Further investigation should be made to study the durability of those coatings by cyclic measurement. More tests would be required as well to see the behavior of those coatings on larger scale containers.