Weathering impact on expanded cork agglomerates as simulated by artificial UV light irradiation

Abstract The weathering properties of expanded cork agglomerates and of cork are presented for the first time, using an accelerated test with UV irradiation. Impacts on surface colour were measured using CIELAb parameters, surface chemistry with ATR-FTIR spectroscopy and cellular morphology with SEM. The surfaces were bleached with ΔE 25.2 and 5.6 for expanded cork and cork, respectively. In cork, lignin was photodegraded as shown by the FTIR spectrum where the lignin peaks at 1505 and 1461 cm −1 disappeared while suberin characteristic peaks were present but with less intense methylene peaks at 2917 and 2852 cm −1 . In the expanded cork, both lignin and suberin were degraded by UV irradiation, leading to formation of an external layer of collapsed cells and cell wall fragments. The effect on the expanded cork agglomerates was higher than that on cork, since the high temperature steaming used for production of expanded cork chemically altered and made more fragile the cell walls. However, the impact of UV irradiation was restricted to the external one-cell layer and therefore does not negatively influence the integrity of the cork materials, their physical properties and in-use performance, but rather imparts a protective layer against further degradation. Expanded corkboards and cork may therefore be used in outdoor conditions without detrimental ageing effects.