K. Biswas, T. Saito, P. Cao, N. Ghezawi, K. Grady, D. Wood, R. Ruther, D. Gilmer
Oak Ridge National Laboratory,
United States
Keywords: self-healing chemistry, addition reaction-based healing, self-healing VIP
Summary:
We will describe the development of novel multi-layered barrier films with self-healing properties for vacuum insulation panels (VIPs). VIPs contain an evacuated core that is sealed within barrier films. Evacuating the core eliminates gas conduction, which is the dominant heat transfer mode in insulation materials. Thus, VIPs can achieve a low conductivity of ≤0.004 W/m-K, vs. ≥0.024 W/m-K of current fiber and foam-based building insulations. Durability of the barrier film of the VIPs is a critical parameter. If the film is punctured or cut, the VIP loses its vacuum and its conductivity rises to 0.02 W/m-K. The risk of damage to the films exists during handling, installation and service life. A self-healing barrier film will remediate any cuts or punctures to maintain the film impermeability and, hence, the internal vacuum and low conductivity of VIPs can be retained. The self-healing technology utilizes an addition reaction between two chemicals, without the need for any external stimuli. The chemicals are incorporated as coatings in a multi-layered film and are initially kept separate with a partition layer. If the film is damaged, the chemicals would mix, react and heal the damage. The self-healing films are being developed via scalable processes using slurries of the self-healing chemicals. The slurries will be coated using equipment that is compatible with high-speed, low-cost roll-to-roll (R2R) manufacturing methods such as slot-die coating, tape casting, and spray coating. Prototype films are being developed and will be tested for the efficacy of the self-healing mechanism via puncture tests in a custom vacuum chamber. Initial puncture tests of small-scale film samples demonstrated the proof-of-concept. The small-scale tests indicated that the chemicals reacted and healed the puncture immediately to maintain the system vacuum.