Influence of light induced accelerated ageing on surface properties of cardboard packaging coated by tio2 nanocomposites

Although the primary role of packaging is to protect its content, it also acts as the carrier of both relevant information and visual identity. To enhance its properties, packaging materials are often coated with material which could provide barrier against chemicals, atmospheric conditions, or electromagnetic radiation. This paper focuses on the change of surface properties, i.e., wetting of a coated cardboard surface when packaging material is exposed to light induced accelerated ageing. Prepared printed cardboard was coated with nanocomposites composed of commercial water-based varnish and defined mass concentration of nanosized TiO2. The prepared samples were subjected to accelerated ageing in a light chamber equipped with Xenon lamp. The characterization of the samples included determining contact angles with liquids of known surface tension and calculating surface free energy, determining water vapour transfer rate and performing burst resistance tests (Mullen burst test). It can be concluded that the UV radiation influenced the cardboard substrate and varnished samples where AcA made some changes in the polar component due to forming of new oxidation products, which are less polar from its -OH group. However, with the introduction of nanoparticles, the UV influence was lowered in terms of surface parameters. The smallest TiO2 weight ratio (0.25%) lowers the WVTR by 56%. Moreover, with increase of TiO2 nanoparticles weight ratio, water permeability decreases significantly where the 0.5% TI/NC provided the best result (decrease of63%). Regarding the mechanical properties, although bursting strength of samples coated with nanocomposites is higher than the one coated by WB, there is no visible dependence between mechanical properties and weight ratio of nanoparticles. This research showed that addition of TiO2 nanoparticles will improve commercial varnish and will increase protection against UV radiation in terms of adhesion to the substrate and water vapour barrier.