Barrier prediction for aluminium foil in laminates 16TH TAPPI EUROPEAN PLACE CONFERENCE 17th TAPPI European PLACE Conference 20-22 May 2019 Crown Plaza Hotel Porto Portugal Barrier prediction for aluminium foil in laminates Presented by: Guenter Schubert Hydro Aluminium Rolled Products GmbH R&D Bonn Your company logo

Structure Manufacturing aluminium foil Definition of pinhole, hole and break-through Origin of pinholes in thin aluminium foil Detecting and measuring pinholes and porosity Permeation model and calculation scheme Conclusions

Structure Manufacturing aluminium foil Definition of pinhole, hole and break-through Origin of pinholes in thin aluminium foil Detecting and measuring pinholes and porosity Permeation model and calculation scheme Conclusions

Structure Manufacturing aluminium foil Definition of pinhole, hole and break-through Origin of pinholes in thin aluminium foil Detecting and measuring pinholes and porosity Permeation model and calculation scheme Conclusions

Structure Manufacturing aluminium foil Definition of pinhole, hole and break-through Origin of pinholes in thin aluminium foil Detecting and measuring pinholes and porosity Permeation model and calculation scheme Conclusions

Definition of pinhole, hole and break-through (according to DIN/EN 546-4) Pinholes (pores)  < 200 µm, statistically distributed Holes  > 200 µm, statistically distributed (no metallurgical inclusions) Holes from rolling  > 200 µm periodically recurring, e.g. in the distance of a roll circumference Any kind of holes is not acceptable!

Process chain of foil manufacturing Hot rolling Cold rolling Soft foil Hard foil Roughing Casting slabs Milling Preheating Finishing Separating / Slitting Annealing Doubling Continuous strip casting 600 mm thick ingots are cast, the cast skin with its heterogeneities is removed and the ingots are heated to 500 to 600 °C for hot rolling. Hot rolling is carried out in reversing mode down to 20 to 40mm (roughing) and then in line in a tandem mill down to 2mm to be wound. An alternative route, using continuous strip casting, also ends up with a metal strip of some single millimetres thickness. Cold rolling is carried out in 6 to 8 steps reducing thickness by about 50% in each step. Generally an intermediate annealing after the first 2 cold roll passes will take place. Before the last cold roll step, two foils are coiled up together (called “doubled”). After separating the foil, the foil is cut into customer’s desired dimensions and finally annealed at about 300 °C, carried out in the range of several days, depending on coil width, foil thickness and temperature applied.

Pinhole detection – Using the pinhole camera… Detector plain (e.g. the eye) Cone of scattered light Stay with your text inside this frame Aluminium foil Pinhole Detecting pinholes is easy, because foil is absolutely impervious to light and pinholes let the light go through. Illumination from the background

Transport model for laminates carrying pinholes in the aluminium foil Passage surface area Polymer Polymer Polymer Polymer Al Al Al Al D Pinhole Pore Pore Pore This picture shows how oxygen passes through a laminate. Behind the pinhole the path in the polymer is not directed, but the oxygen molecule can move in any direction with the result of a much larger passage surface area at the interface between the coating and the atmosphere than the projection of the cross-sectional area of the pinhole itself.

Conclusions Aluminium foil as a 100% crystalline metal inhibits any transport of matter Conditional of manufacturing, there is no thin foil absolutely free of pinholes As soon as pinholes are coated with polymers, their contribution to a permation rate can not be measured at all Relative to their size, the effect of small pinholes is stronger A worst case permeation calculation system gives an indication of permeation rate (input: specific permeation rate and thickness of the polymers on one or both sides of the foil; number and average size of pinholes) The functional barrier of aluminium foil persists even in the presence of pinholes

“Thank You” for your patience Your company logo “Thank You” for your patience Presented by: Guenter Schubert - Foil Converting - Hydro Aluminium Rolled Products GmbH, R&D Bonn guenter.schubert@hydro.com