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 ? 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, 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 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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