# New Flexible Protective Coating for Printed Smart Textiles
###### Abstract  
In the field of food packaging, the addition of exfoliated layered silicates in polymers has been established to improve the polymers' gas barrier properties. Using these polymers as coatings to protect smart textiles from oxidation and corrosion while maintaining their textile properties should significantly extend their lifetime and promote their market penetration. The aim of this study was to print new polymer dispersions containing layered silicates to protect screen-printed conductive structures, and to test the resulting samples. For this, appropriate printing parameters were determined by statistical design of experiments. According to these results, conductive structures were printed and protected with the selected coating. The abrasion resistance and the continuity of the protective layer of the printed samples were then measured. A continuous protective coating of approximately 70-80 \(\upmu\)m thickness was applied on a conductive structure. The printed samples showed a very high resistance to abrasion (unchanged by 85,000 abrasion cycles) while remaining flexible and presenting a lower water vapor permeability (<2.5 g/m\({}^{2}\) d) than the coatings commonly used in the textile field.  
protective coating; smart textiles +
Footnote †: journal: Applied Sci.  
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[PERSON]  
accelerates and intensifies these corrosion processes and leads to a loss of the metals' electrical conductivity. This limits their high application potential for printed electronics in smart textiles [13; 14; 15] and prevents applications in humid environments [16; 17; 18; 19].  
Barrier requirements for coatings with low water vapor and oxygen diffusion rates go far beyond the coating requirements for electrical insulation. The coatings established in textile technology, such as polyurethane, polyacrylates and silicones, generally meet electrical insulation requirements (especially for the low-voltage power supplies commonly used in smart textiles), and ensure waterproofing. However, the coatings do not meet the barrier requirements for water vapor and oxygen in electronic assemblies sensitive to oxidation and water vapor. On the other hand, the coating materials commonly used in electrical engineering do not maintain the typical properties of textiles (flexibility, shape adaptation, textile feel, etc.). Therefore, the development of new coatings is needed to meet the requirement of smart textiles by protecting the sensor structures efficiently.  
Few polymers are effective barriers against both water vapor and oxygen [20].Several approaches for flexible barrier layers are described in the scientific literature [21]. For example, highly flexible barrier layers were realized by multilayer polyurethane-EVOH combinations [22; 23]. On the other hand, coatings with increased water vapor and oxygen barriers have been achieved by incorporating layered silicates into aqueous polymer dispersions or polymer melts [24].  
This study focuses on using polymeric coating systems which have not yet been established as textile coatings to print and test a new thin and flexible coating for printed smart textiles with a barrier effect against water vapor. For this, we developed several polymeric systems with diffusion-inhibiting polyurethane dispersions mixed with layered silicates. The most appropriate coating was involved in the fabrication of a printed smart textile. The abrasion resistance of the printed textile samples as well as their insulation properties were tested.