Textiles with dynamically color-changing effects depending on the observation angle were achieved by applying a coating paste containing multicolor effect pigments using a knife-over-table coating method. Black and white textile substrates with different structure characteristics depending on yarn type (multifilament and spun) and thread count (high and low) were studied and compared to a paper test chart as a smooth reference. The influence of surface structures on effect pigment coatings were investigated and compared with TiO2 coatings. Scanning electron micrographs showed that the substrate surface roughness increased when constructed of multifilament yarns with high thread count, spun yarns with higher thread counts and spun yarns with lower thread counts. Multi-angle spectrophotometer measurements of effect pigment-coated samples showed that the color differences in form of the CIE L*a*b*-coordinates varied to great extents, depending on detection angles, surface roughness and color of the substrates, compared to TiO2-pigment coatings with insignificant color-changing effects. The parallel alignment of effect pigment platelets was more easily achieved on the test chart. As a result, the color-changing effect was less intense on coated textiles. The effect were approximately reduced by half when coated on a substrate constructed of spun yarns compared to one made of multifilament yarns.

In order to optimize the color-changing effects of textile knife-coatings containing multi-layered mica pigments (effect pigments; EPs), the properties and structure of the coating formulation/layer during and after application were investigated. Three pigment coating formulations were prepared by first mixing the EP dispersion into a water-based polyurethane binder. Different types of rheology modifiers (RMs), liquid dispersion of sodium polyacrylates (LDPSAP), hydrophobically alkali swellable emulsions (HASEs) and hydrophobically modified ethoxylated polyurethane, were then added to the dispersion. The rheological behavior of the coating formulations was characterized in terms of the shear rate dependence of the viscosity. The formulations were applied onto the same type of textile substrate using a knife-coating technique. The choice of RM as well as variations in gap height and coating speed increased the solids deposit. The increased amount of coating deposits (thicker coating layers) corresponded to more and better dispersed EPs within the coated layer as well as more horizontally oriented platelets as confirmed by scanning electron microscopy. Multi-angle spectrophotometer measurements showed that the CIE L*a*b* color coordinates varied strongly depending on detection angle. The variations of the absolute values of L* and a* were more pronounced between –15° and 15° detection angles, corresponding to angles with the greatest visual color changes. The slowly coated samples with higher solids deposit were measured to be lighter and of higher chroma compared to samples coated at a higher speed. Generally, the color-changing effects were governed by the choice of RM and coating parameters in terms of variations of the amount of coating deposited onto the samples.

Two conductive formulations containing different types of micron-sized metal flakes (silver-coated copper (Cu) and pure silver (Ag)) were characterised and used to form highly electrically conductive coatings (conductors) on plain and base-coated woven fabrics, the latter in an encapsulated construction. With e-textiles as the intended application, the fabric stiffness, in terms of flexural stiffness and sheet resistance (R_sh), after durability testing (laundering and abrasion) was investigated and related to user friendliness and long-term performance. Bare and encapsulated conductors with increasing amounts of deposited solids were fabricated by adjusting the knife coating parameters, such as the coating gap height (5, 20, 50, and 200 μm), which reduced the R_sh, as determined by four-point probe (4PP) measurements; however, this improvement was at the expense of increased flexural stiffness of the coated fabrics. The addition of a melamine derivative (MF) as a cross-linker to the Cu formulation and the encapsulation of both conductor types gave the best trade-off between durability and R_sh, as confirmed by 4PP measurements. However, the infrared camera images revealed the formation of hotspots within the bare conductor matrix, although low resistances (determined by 4PP) and no microstructural defects (determined by SEM) were detected. These results stress the importance of thorough investigation to assure the design of reliable conductors applied on textiles requiring this type of maintenance.

In this study, two different conductive coating formulation containing silver (Ag) and silver-coated copper (Cu) flakes are studied to evaluate the electromechanical stabilityof encapsulated conductors coated on textiles in a multilayer construction. Consideringe-textiles as a possible application area with integrated conductors functioning as interconnections, the purpose is to obtain a fundamental understanding of the deformation behaviour when subjected to tensile and compressive strains during bending. The results show that an increased Ag conductor thickness with flakes <5 μm was a favourable combination regardless of encapsulation thickness providing samples with minimal stress responses upon bending deformations at angles of -180°, -90°, 90°and 180°, and, sheet resistance (Rsh) values of 0.01 Ω/sq. It was shown that the conductor layer changed shape depending on the bending angle resulting in alternating convex and concave arcs at -180° and a more uniform curvature at 180°. The findings were correlated to lower and larger Rsh ratios, respectively, which are denoted as the thinner encapsulated Ag conductors and the Cu conductors of different thicknesses, respectively. Up to ten repetitive bendings at angles between -180° and 180° did however induce stresses within the material resulting in an increased Rsh by a factor of>10.