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Functional Textile Coatings Containing Flake-shaped Fillers: investigations on selected optical and electrical properties
University of Borås, Faculty of Textiles, Engineering and Business.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates the manufacturing and characterisation of functionalised textile coatings containing different types of flake-shaped fillers with angle-dependent colour-changing and electrically conductive properties, respectively. Common benefits of these types of flakes are their high aspect ratio, which offers low filler loading with high functional performance. However, when applied on flexible fabric, their impact on the mechanical properties and durability leads to that a trade-off between, for example, flexural rigidity and functional performance need to be taken into account. Both experimental studies, with different functional approaches, explore how formulation additives e.g. rheology modifiers and cross-linker and knife coating parameters e.g. gap height and speed influence the formulation viscosity, which in turn strongly influences the amount of solids deposited on the fabric, and the functional performance.

Multilayered mica pigments can provide an angle-dependent colour change based on the phenomenon of interference, and has great potential in application within the textile design and product authentication fields. However, optimal conditions for intense colour-changing effects using these types of flake-shaped pigments depend on a plane-parallel orientation to a flat substrate. The pigment orientation is challenged by textile substrates, which have a textured surface due to the cross-sectional shape of the fibre, the yarn composition and fabric construction. In addition, the semi-transparent nature of these types of pigments means that the substrate colour highly influences the colour-changing effects.

Metal flake-shaped fillers for high electrical conductivity applications are particularly advantageous for reliable power and signal transferring interconnections in the field of electronic textiles. As the conductivity depends on the electron transport between the metal flakes, the challenge is to establish and maintain the three-dimensional network of contacting surfaces between flakes. Although the network is held together and adhered to the substrate by an insulating polymer film matrix, it is highly sensitive to dimensional impact upon different

Place, publisher, year, edition, pages
Borås: Högskolan i Borås, 2018. , p. 69
Series
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 87
Keyword [en]
Flakes, fillers, textile coating, properties, multilayered mica, effect pigment, angle-dependent colour change, metals, conductivity, resistance measurements, e-textiles, flexibility, durability
National Category
Engineering and Technology
Research subject
Textiles and Fashion (General)
Identifiers
URN: urn:nbn:se:hb:diva-13691ISBN: 978-91-88269-90-4 (print)ISBN: 978-91-88269-91-1 (electronic)OAI: oai:DiVA.org:hb-13691DiVA, id: diva2:1183782
Public defence
2018-04-27, Vestindien C, Textile Fashion Centre, Skaraborgsvägen 3, Borås, 10:00
Opponent
Available from: 2018-04-04 Created: 2018-02-19 Last updated: 2018-04-10Bibliographically approved
List of papers
1. Effects of surface structure and substrate color on color differences in textile coatings containing effect pigments.
Open this publication in new window or tab >>Effects of surface structure and substrate color on color differences in textile coatings containing effect pigments.
2014 (English)In: Textile research journal, ISSN 0040-5175, E-ISSN 1746-7748, Vol. 84, no 2, p. 63-77Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Sage Publications Ltd., 2014
Keyword
Color-changing textiles, Special effect pigments, Coatings, Multi-angle spectrophotometric measurements, Surface structure, substrate color, Textile technology
National Category
Materials Engineering
Research subject
Textiles and Fashion (General)
Identifiers
urn:nbn:se:hb:diva-1778 (URN)10.1177/0040517513485626 (DOI)000329961700002 ()2320/13241 (Local ID)2320/13241 (Archive number)2320/13241 (OAI)
Note

Sponsorship:

FoU nämnden, Högskolan i Borås

Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2018-04-04Bibliographically approved
2. Influence of rheology modifiers and coating parameters on the color-changing effects of textile coatings with multi-layered mica pigments
Open this publication in new window or tab >>Influence of rheology modifiers and coating parameters on the color-changing effects of textile coatings with multi-layered mica pigments
2014 (English)In: Textile research journal, ISSN 0040-5175, E-ISSN 1746-7748, Vol. 85, no 9, p. 936-948Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Sage Publications, 2014
Keyword
color-changing textiles, structure-properties, special effect pigments, multi-layered mica pigments, textile coatings, coating parameters, rheology modifiers, Textile Technology
National Category
Materials Engineering
Research subject
Textiles and Fashion (General)
Identifiers
urn:nbn:se:hb:diva-3279 (URN)10.1177/0040517514557309 (DOI)2320/14562 (Local ID)2320/14562 (Archive number)2320/14562 (OAI)
Note

Sponsorship:

FoU nämnden, Högskolan i Borås

Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2018-04-04Bibliographically approved
3. Characterisation of Electrical and Stiffness Properties of Conductive Textile Coatings with Metal Flake-shaped Fillers
Open this publication in new window or tab >>Characterisation of Electrical and Stiffness Properties of Conductive Textile Coatings with Metal Flake-shaped Fillers
(English)In: Smart materials and structures (Print), ISSN 0964-1726, E-ISSN 1361-665XArticle in journal (Refereed) Submitted
Abstract [en]

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 basecoated woven fabrics, the latter in an encapsulated construction. With e-textiles as the intended application, the fabric stiffness, in terms of flexural rigidity and sheet resistance (Rsh), after durability testing (laundering and abrasion) was investigated and related to userfriendliness 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 Rsh, as determined by four-point probe (4PP) measurements; however, this improvement was at the expense of increased flexural rigidity 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 andRsh, as confirmed by Fourier transform infrared (FTIR) spectroscopy and 4PP measurements. However, the infrared camera images revealed the formation of hotspots within the bare conductor matrix, although low resistances and no microstructural defects were detected by SEM. These results stress the importance of thorough investigation to assure the design of reliable conductors applied on textiles requiring this type of maintenance.

Keyword
Conductivity, metal flake, coating, textile, coating parameters, encapsulation, fabric stiffness, durability
National Category
Materials Engineering
Research subject
Textiles and Fashion (General)
Identifiers
urn:nbn:se:hb:diva-13942 (URN)
Available from: 2018-04-04 Created: 2018-04-04 Last updated: 2018-04-04
4. Stability of encapsulated electrical interconnections coated on fabric exposed to mechanical strain.
Open this publication in new window or tab >>Stability of encapsulated electrical interconnections coated on fabric exposed to mechanical strain.
(English)In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069Article in journal (Refereed) Submitted
Abstract [en]

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.

Keyword
Electrically conductive textiles, interconnections, coatings, encapsulated, mechanical stability
National Category
Materials Engineering
Identifiers
urn:nbn:se:hb:diva-13943 (URN)
Available from: 2018-04-04 Created: 2018-04-04 Last updated: 2018-04-04

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