THE

LOTUS
EFFECT
WATER- REPELLENT AND
SELF-CLEANING PROPERTIES
The lotus-effect is a natural phenomenon
which could be observed on the surface of
the lotus flower leaves and refers to the
high-water repellence they exhibit. Small dirt
particles are collected by the water droplets
themselves thanks to a complex micro- and
nanoscopic structure of the surface, thus
reducing the adhesion.
This natural phenomenon has inspired
nanotechnologists to develop such a
technique which using the same
nanostructures forms hydrophobic coatings
with a self-cleaning-effect.
THE LOTUS EFFECT IN TEXTILE
• Water-repellent coating technologies include
dip-coating, impregnation, padding, sol-gel, plasma,
and spray coating. Water-repellent-based coating
materials explored include silane, silicone,
polyurethane, fluorochemical, wax, stearic acid,
acrylate-based coatings, and even unconventional
materials like polyvinyl alcohol, super hydrophobic
precipitated calcium carbonate (SHPCC), boric acid,
and boron-based coatings.
THE LOTUS EFFECT IN TEXTILE
•Different coating materials exhibit distinct
water-repellency mechanisms. Paraffin-based coatings are
primarily deposited through mechanical incorporation,
filling fiber pores and spaces between yarns. Silicone and
fluorocarbon products form a thin hydrophobic layer on
the fiber surface. Nanoparticles can increase surface
roughness, enhancing water hydrophobicity and
repellency. Fatty acid resin-based coatings are deposited
via chemical reactions with the fiber surface.
THE LOTUS EFFECT IN TEXTILE
•To achieve water repellency, the critical
surface tension of the coating needs to be
lower than the surface tension of water,
allowing water to be repelled.
Superhydrophobic surfaces exhibit the highest
water repellency, with a water contact angle
(WCA) exceeding 150° and a water sliding
angle (WSA) less than 10°
THE
LOTUS
EFFECT
ON REAL TEXTILES
A Novel Method To Produce
Sustainable Wind Resistant
And Water Repellant Fabric
For Outdoor Sport Clothing
A journal by Veerakumar Arumugam, Alfred Iing Yoong Tok and
file:///C:/Users/ACER/Downloads/arumugam-et-al-2023-a-novel-method-to-produce-sustainable-
Vitali Lipik
wind-resistant-and-water-repellant-fabric-for-outdoor-sport.pdf
Introduction
Water repellant and breathable feature of clothing can
prevent water from environment and meanwhile
actively funnels perspiration away from the body to
keep wearer feeling dry during outdoor sports. Several
characteristics in a finished apparel can be achieved
through traditional layering system by combining
various elements such fabrics, water repellant
polymers, films and membranes.
Introduction
These kind of sandwiched multifunctional fabrics are
commercially produces using several technologies such as
coating of polyurethane (PU) using organic solvents,
hot-melt lamination using fluorocarbon resins and acrylic
paste, dot-lamination of polymeric films, and lamination of
porous membranes etc. Majority of the manufacturers are
using durable water repellent (DWR) finishes by depositing
hydrophobic substances such as fluoropolymers,
fluoro-chemicals, silicones and waxes and/or laminating
premade or extruded polymeric film on fabric surface with
thermal or adhesive bonding to achieve required functional
performances.
Introduction
The primary drawbacks of these kind of coated or laminated
waterproof fabric contains per and polyfluorinated compounds
(PFCs), which are harmful to human health and environment. Also,
they are complex to produce which often involves multiple
procedures with each associated process adding further cost to the
final apparels, more solid product waste and additional energy
consumption. The conventional techniques also alter the material
properties of the underlying textiles that may detrimentally affect
the mobility of the clothing assemblies, poor abrasion resistance,
and causes sweat and soil build up within the layers.
Experimental
Materials
In this work, polyester (Polyethylene
Terephthalate) multifilament yarn of 75D/72f, was
used as base yarn and low melt polyamide
(co-polyamide 6 and 66) multifilament yarn of
100 denier was used as matrix yarn to develop
fabric during knitting.
Experimental
Fabrication of Samples
The PLAITED KNITTED TECHNIQUE was used to develop fabric
with polyester in the back of the knit (close to the body);
combined with low melt polyamide in the face (outer surface)
was developed using customized 24 gauge, 6-feeders, 16-inch
circular knitting machine. The polyester (43%) and low melt
polyamide (57%) were used to create required plaited knit fabric.
The schematic demonstration (Figure 1) shows that the unique
method to develop wind resistant and water repellent fabric
through sequence of fabrication stages
Experimental
Spray Rating Test was conducted following American
Association of Textile Chemists and Colorists (AATCC)
TM22-2017-e with the help of GESTER Instruments to
determine fabric resistance to surface wetting. In this
test, the water is sprayed on fabric specimen which was
clamped tightly using ring. The sprayed water produces
a pattern on the fabric surface which is then compared
against the provided standard spray test chart to
provide a repellency rating for the specimen.
Experimental
Water Contact Angle (WCA) was measured using the
Contact Angle System Dataphysics OCA 15 Pro to check
hydrophobicity of fabric with different thermal
treatment conditions. The measurements were
performed with DI water droplet of 6 μL ejected at 1 μL
per second rate. The values of WCAwere measured in
five different positions and the mean value of the
contact angles was taken
Experimental
Water Vapor Transmission (WVT) was tested in accordance
with ASTM Test Method E96. In the test, fabric is affixed in a
dish containing distilled water and weighed at different
times to determine the rate of vapor movement through
the specimen from the water to a controlled atmosphere.
Specifically, dish assembly is placed into a testing chamber,
supplied by Lab think,where sample measurement is
performed hourly for 24 h. The test was performed 3 times
for each sample to obtain an average WVT reading.
Results and
Discussion
Water Repellency
It was observed that fabric is higher in
water repellency when thermally
processing at higher temperature (120°
C), pressure at 0.5 MPa and time of 30 s.
Results and
Discussion
Hydrophobicity (Water Contact Angle)
The highest WCA (120.1°) was obtained for fabric (FM6)
which reveals its hydrophobic character, this could
probably be due to the combined and optimized
treatment conditions of time temperature and
pressure. Some fabric samples (FM1, FM4, FM15) show
hydrophobic behavior with WCA greater than 90°,
which are near to optimized processing conditions
Results and
Discussion
Water Vapor Transmission
The water vapor diffusion occurs only through the pore
spaces of the fabrics and/or membranes. The diffusion
of moisture through polyamide is higher than other
synthetic polymers, as polyamide has tendency to
absorb moisture (around 4% at 65% relative humidity)
within the structure and due to sorption and
desorption behavior.
Performance Evaluation Of
Water-repellent Combat
Uniforms Using A Static
Manikin And Human Subjects
Under A Rainfall Tower System
A journal by Juyoun Kwon, Kijoon Kim, Jeongkyun Ju &
https://fashionandtextiles.springeropen.com/articles/10.1186/s40691-020-0024
Joo-Young Lee
4-3
Introduction
Water-repellent military uniforms which protect soldiers from
getting wet are beneficial. Such uniforms can be beneficial for
soldiers although the water-repellent fabrics have different
properties from waterproof fabrics which exclude water under
pressure such as heavy/driving rain or cross bodies of water.
Water-repellent coatings could minimize soldier’s contact
with cold water and thus minimize the saturation of their
clothing in general. The hypothermia of soldiers subject to
cold and rain could be minimized through water repellent
combat uniforms. Furthermore, water-repellent combat
uniform may be somewhat helpful in protecting soldiers from
chemical and biological (CB) contaminations.
Introduction
There are a number of test factors to evaluate the
water-repellant performance of textiles: contact
angle, time of wetting, time to dry, the droplet
weathering, liquid adsorption, drop roll off, or
vertical wicking resistance. However, these test
factors are typically conducted on plain fabrics and
do not take into account factor such as clothing
design, closures, openings, layering, or seams.
Methods
Physical characteristics of experimental combat uniforms
Two kinds of water-repellent (WR) combat uniforms,
which were newly-developed for the present study, were
compared to the current Korean combat uniform.
Original textiles of the combat uniform (Polyester 70%
and Rayon 30%) were coated using C-6 fluorinated water
repellents (Company M) and perfluorinated compounds
free (PFC-free) water repellents (Company T) but with
the different techniques of two different companies.
Methods
Test using artificial rainfall and a static manikin
This study evaluated the performance of
water-repellent uniforms based on static
manikin as well as human wear trials, and
the identical measurement sites in the
manikin and human wear trials were selected
from the measurement locations presented
in the BS EN 14360 (2004).
Methods
Test using artificial rainfall and a static manikin
A rainfall tower system was installed with an
artificial rainfall system that caused rain to fall
from a height of 10 m above the ground. The
static manikin was a replica of an adult male (a
height of 182 cm, consisting of the head, torso,
buttocks, arms, hands, legs, feet, etc.). A
Cylindrical humidity sensors were attached to
the 11 body regions of the manikin surface to
determine when rainwater penetrated the
combat uniform.
Methods
Human wear trials in the rainfall tower system
Eight healthy male subjects (28.4 ± 5.42 y in age, 174 ± 5
cm in height, and 71.4 ± 8.6 kg in body weight) participated
in the three experimental conditions of the three combat
uniforms. Informed consent was obtained from all subjects.
The experiment was approved by the institutional review
board of Seoul National University (IRB # 2008/002-004).
Three identical combat uniforms were selected for the static
manikin test. Human subjects wore briefs, combat boots, a
combat uniform shirt and trousers. The order of participation
was counter-balanced to avoid any possible order effect.
Methods
Human wear trials in the rainfall tower system
Subjects evaluated themselves via questionnaire
during the 20-min recovery session, just after
30-min of walking, under the rain system, in order
to evaluate the water-repellent properties under a
rainfall condition. Subjects evaluated themselves in
terms of tactile skin sensation, softness, wetting
time, heaviness of wet clothes, humidity sensation,
thermal sensation and thermal comfort on a
seven-point categorical scale.
Results
Manikin Test
The current combat uniform (no water repellent)
was wet in 10 min, whereas water-repellent
combat uniforms, especially WR_T, were wet later
or not wet even after 60 min. For the heavy rain
condition, lower body parts even covered by
water-repellent uniforms were wet in 60 min
Results
Human Test
The wetting time was quicker for the Control(no
water repellent) than for WR_T but no significant
difference was found among the three uniforms.
For Control and WR_M, time of wetting did not
differ for the four regions, but upper back and
forearm were different for WR_T (P < 0.05). All
three combat uniforms tended to be wet in the
upper back region the quickest, while the forearm
part tended to be wet the latest.
Discussion
Although the level of water repellency of the new
fabric itself (both WR_M and WR_T) was
evaluated as the identical level 5, through the
various variables of the rainfall test, these
water-repellent uniforms were classified into
sub-levels of water repellency (e.g., excellent or
fair class). Wetting in under 10 min can be
regarded as a fail case, while over 20 min is an
excellent level and between 10 and 20 min is a fair
level. As stated, these criteria are potential, not
definitive.