Abstract
In this work, physical characterisation of film formation and film properties of coating and adhesive formulations was performed. Organic/inorganic nanocomposite coatings draw remarkable academic and industrial interest, due to their expected enhancement of combined properties. Film formation and film properties, such as drying, transparency, and final film quality of coating systems containing Laponite clay were studied, in particular the influence of excess surfactant on the drying process. It was found that excess surfactant in the system does affect the physical characteristics of the film formation process. Experiments using magnetic resonance profiling and photographs found lateral flow of liquid from the edges to the centre. Reducing the amount of surfactant in the system improves film quality by reducing lateral flow during film formation. In pressure sensitive adhesive (PSA) applications, such as labels or tapes, it is vital that the films remain optically transparent, regardless of the exposure to high humidity or water. Core/shell PSAs were investigated to determine their drying, water whitening, moisture absorption from high humidity, and adhesive properties. The dependence of these properties on pH and poly (acrylic acid), PAA, was studied. It was found that the hydrophilic pathways created by PAA shells do not contribute to faster drying. In addition, this investigation disproves the idea that a "hairy layer" of PAA keeps the film more open and leads to faster drying. It was found that films with hydrophilic boundaries absorbed more water. The water is evenly distributed along the boundaries, so that films still retain their transparency. It was proved that transparency or water whitening is not necessarily a reliable measurement of water uptake, at least for this system. The findings from this study define guiding principles for organic/inorganic nanocomposite coatings and core/shell PSAs, to have better film formation characteristics and film properties.