Please cite this article in press as: O. Miesbauer, et al., Studies on the barrier performance and adhesion strength of novel barrier films for vacuum insulation panels, Energy Buildings (2014), http://dx.doi.org/10.1016/j.enbuild.2014.06.054 ARTICLE IN PRESS G Model ENB-5160; No. of Pages 7 Energy and Buildings xxx (2014) xxx–xxx Contents lists available at ScienceDirect Energy and Buildings j ourna l ho me page: www.elsevier.com/locate/enbuild Studies on the barrier performance and adhesion strength of novel barrier films for vacuum insulation panels Oliver Miesbauer a , Esra Kucukpinar a,∗ , Sandra Kiese a , Yoash Carmi b , Klaus Noller a , Horst-Christian Langowski a,c a Fraunhofer Institute for Process Engineering and Packaging IVV, Giggenhauser Strasse 35, D-85354 Freising, Germany b Hanita Coatings, Kibbutz Hanita 22885, Israel c Technische Universität München, Weihenstephaner Steig 22, D-85354 Freising, Germany a r t i c l e i n f o Article history: Available online xxx Keywords: Vacuum insulation panel Barrier film Poly(ethylene terephthalate) Aluminium Aluminium oxide Hybrid polymer Oxygen permeability Adhesion a b s t r a c t Novel cost efficient high barrier envelopes are developed for vacuum insulation panels. In order to fulfil the required maximum oxygen permeability (at 23 ◦ C and 50% relative humidity (RH)) of 1 × 10 -14 m 3 (STP) m -2 day -1 Pa -1 and water vapour transmission rate (at 23 ◦ C and 85% → 0% RH) of 1 × 10 -6 kg m -2 day -1 , hybrid polymeric (ORMOCER ® ) and aluminium barrier layers are combined. Using roll-to-roll processes, these materials are deposited from the liquid or gas phase on top of a poly(ethylene terephthalate) substrate film. The low adhesion strength observed between aluminium and ORMOCER ® layers is significantly increased by the deposition of an additional aluminium oxide layer between the two materials. The lamination of a polyethylene or polypropylene sealing film does not weaken the adhesion strength. The resulting barrier structure has reached an oxygen permeability of lower than 5 × 10 -14 m 3 (STP) m -2 day -1 Pa -1 (at 37 ◦ C and 30% RH). Electrochemical impedance spectroscopy gives evidence for a possible penetration of the ORMOCER ® lacquer into the aluminium oxide layer (synergis- tic effect), which explains the improved adhesion and barrier performance due to the aluminium oxide layer. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Vacuum insulation panels (VIPs) can meet the demand for durable, efficient, space saving and sustainable thermal insulation materials to be applied at buildings and refrigerators. The VIP core consists of a highly porous material having pore diameter in the micro- to nanometer scale and is encapsulated by a barrier envelope [1,2]. Typical VIP core materials used are open cell polyurethane, fumed and precipitated silica, glass fibres and aerogel based mate- rials. After evacuating the core material, the following mechanisms of heat transfer arise in a VIP: heat conduction by the residual gas (oxygen and nitrogen) or water vapour within the pores, heat con- duction by the solid skeleton of the core and radiation [1,3,4]. The first contribution is the most significant one and it is either due to gas or water vapour permeation from the environment into the ∗ Corresponding author. Tel.: +49 8161 491 507. E-mail addresses: oliver.miesbauer@ivv.fraunhofer.de (O. Miesbauer), esra.kucukpinar@ivv.fraunhofer.de (E. Kucukpinar), sandra.kiese@ivv.fraunhofer.de (S. Kiese), yoash@hanitacoatings.com (Y. Carmi), klaus.noller@ivv.fraunhofer.de (K. Noller), horst-christian.langowski@ivv.fraunhofer.de (H.-C. Langowski). VIP or due to outgassing from the core material or from the enve- lope. However, especially for more hygroscopic core materials such as fumed silica, a significant part of the water vapour within the pores is adsorbed at the inner surface of the core material resulting in heat conduction by this adsorbed phase or in heat transfer by evaporation, diffusion and condensation of water vapour [1,4]. In order to maintain the thermal insulation performance of VIPs during their intended lifetime, the barrier envelope has to sig- nificantly reduce the permeation of oxygen, nitrogen and water vapour into the VIP [1,4,5]. However, permeation takes place not only through the barrier envelope but also through the material of the sealing seam and through micro-defects possibly contained in it [5,6]. As an example, fumed silica based VIP having dimensions of 0.5 m × 0.5 m × 0.03 m is considered. After 50 years a maximum thermal transmittance of 0.2 W m -2 K -1 is allowed [7], which cor- responds to a thermal conductivity of 6.0 × 10 -3 W m -1 K -1 for such a VIP. In this case, the required barrier performance of a VIP envelope to gases is calculated for a temperature of 23 ◦ C and 50% relative humidity (RH) in the environment. In order to simplify the situation, it is assumed that 50% RH will be reached in the VIP core material within the considered time period of 50 years. http://dx.doi.org/10.1016/j.enbuild.2014.06.054 0378-7788/© 2014 Elsevier B.V. All rights reserved.