Water-repellent and breathable clothing
Functional clothing and materials Nina Forsman 24.9.2019 Hydrophobicity?
< 90° > 90° > 150° hydrophilic hydrophobic superhydrophobic Surface hydrophobicity vs absorption Water-proof -> diving Water-repellent -> rain
absorption Water-repellency is not a problem, neither breathability. It is the combination that is tricky. What makes a surface hydrophobic? 1. Low surface energy -> oils, waxes etc. 2. High surface roughness
How is this achieved on textiles? Existing water-repellent textiles Membranes, e.g. GoreTex - Microporous structure of polytetrafluoroethylene (PTFE, Teflon) Other microporous polymer membranes and coatings Polyurethane, acrylics, polyamino acids … Closely woven fabrics Ventile, Poplin Existing water-repellent textiles
Biomimetic fabrics Stomatex, closed cell foam neoprene, mimicking transpiration in plant leaves Sympatex, membrane made of polyether-ester block copolymer Super-Microft, microscale roughness like the lotus leaf Shoe sprays
Wax bars Fjällräven What about eco-friendliness? Water-resistant and breathable
Unmodified textile Wax particles Continuous wax film
H2O H2O H2O vapor vapor vapor
H2O H2O liquid liquid
H2O liquid
Cellulosic textile
24.9.2019 8 Wax particles
10μm
Carnauba wax Wax dispersion
Images: www.ehow.com www.newdirectionsaromatics.com www.sonicator.com Layer-by-Layer deposition of the coating
24.9.2019 10 Natural polycations (binding agents) Poly-L-lysine (PLL) Chitosan Cationic starch - Protein - Comes from - Comes from potato, - Antibacterial and a shrimps shells rice, corn etc. bit hydrophobic - Reasonably priced - Naturally anionic - Expensive - Cheap - Used in the textile industry The wax particle coating
water vapor Anionic wax water particles
Cation, e.g. PLL, cationic starch
Forsman et al, Carbohydrate Polymers, 2017, 173:392-402 24.9.2019 12 Curing temperature Curing at 70 °C gives the highest contact angle,
but better long-time water- resistance is achieved with melted particles The modified textiles repel water well
24.9.2019 14 Water-resistance tests Hydrostatic head
Spray test sample result (scale 0-5) 2BL PLL/wax, 105 °C 2-3 2BL PLL/wax, 70 °C 2-3 2BL CS/wax, 105 °C 1-2 commercial shoe spray 1-2 17 cm
The fabric itself also affect the results Ref = untreated Breathability reference S = shoe spray G = thin layer Greenland wax GG = thick layer Greenland wax W70 = wax particles, cured at 70 °C W105 = wax particles cured at 105 °C Water contact angle = = angle contact hydrophobicity Water Water vapor permeability = breathability = permeability vapor Water
Wax particle coating best Greenland wax compromise between water-repellency and breathability Long term water-repellency Morphology: SEM images
Reference 2BL PLL/wax 2BL+ 105C
Cotton
Linen
24.9.2019 18 Surface roughness of the textiles
The surface roughness of the textiles adds to the hydrophobicity Working with our method
Not washable with detergents The coating cane be applied by dipping, spraying or brushing Pigments can be added to the wax dispersion Design: Matilda Tuure Photos: Valeriya Azovskaya 24.9.2019 21 Other methods found in literature Fluorocarbons, nanoparticles and silica Food for thought o What are the properties of the material - In terms of the application (clothing)? - In terms of the environment? o What level of functionality do we need? o Durability and persistence, what is desirable and what is not?
Designers decide what we wear, not engineers. Summary - Low surface energy + high surface roughness - Non-toxic, breathable and water-resistant textiles using wax particles on cellulose - Utilization of the intrinsic properties of the fabric. How can design help? Thank you! Questions?
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