This document discusses water repellency and breathability in fabrics. It defines water repellency as water globules not spreading on a textile surface. Breathability requires fabrics to be soft, lightweight, durable, and allow rapid moisture transfer while regulating heat and moisture. Various testing methods are described to evaluate breathability properties. Coatings like polyurethane can be applied to generate micro pores for breathability. Applications include protective clothing, outdoor wear, and roofing membranes where breathability and water resistance are important.

1. Water repellency & Waterproof
Breathable Fabrics and repellency test
method

2. Water repellency
Water repellent is a state characterized by the non-
spreading of water globules on a textile material.This
term is not normally applied to a water-repellent finish
impervious to air.This is generally referred to as water
proof. It is generally done by treated fabric with fat,
wax, rubber etc.
14/3/2014 Vignesh Dhanabalan (M.Tech) - vigneshdhanabalan@hotmail.com

3. Requirements of Water Repellency
Textiles
Purpose and Scope
• This method of test is especially suitable for screening if
any textile has been given a water-repellency finishes. It
is not intended for use in measuring the penetration of
water through the fabric.
Terminology
• Water Repellency: in textiles, the characteristic of a fiber,
yarn or fabric to resist wetting
14/3/2014 Vignesh Dhanabalan (M.Tech) - vigneshdhanabalan@hotmail.com

4. Water Repellency Classification
Grade Classification
100 (ISO5 ) Excellent
90 (ISO 4) Very Good
80 (ISO 3) Good
70 (ISO 2) - ---
50 (ISO 1) - ---
0 ----
14/3/2014 Vignesh Dhanabalan (M.Tech) - vigneshdhanabalan@hotmail.com

5. Principles of moisture vapor transfer:
Absorption, transmition and desorption of
the water vapor by the fibers.
Diffusion of the water vapor through the air
spaces between the fibers.
Transmition of water vapor by forced
convection

6. Capillary pressure and capillary raise are determined using
P = 2γLV cos  / Rc , L = ((Rcγ cos /2)* t1/2
P = capillary pressure L = liquid pressure
Rc – capillary radius t and  - time and viscosity
Transport Mechanism:
Capillary’s diameter and surface energy

7. Properties required for breathable fabrics:
Soft feel, light weight and Durable
Easy care/launderability
Rapid drying to prevent
catching cold.
Good air and water vapor permeability.
Rapid moisture absorption and conveyance capacity
Optimum heat and
moisture regulation
(thermo-regularity
effect)
Absorption of
surplus heat.
Dimensionally stable even when
comes in contact to water
No/Minimum water
absorption of the layer of
clothing just positioned to
the skin.

8. Producing breathable fabrics:
Smart Breathable fabrics (PCP)
SMP – PU material Micro porous Membrane
Densely Woven Fabric
(Micro denier<10 micron)
Closely woven fabrics
(oxford weave) up to 20 min

9. Various methods for
generating microspores
membrane and coating:
•Mechanical fibrillation (Film) - PTFE films – biaxial stretched- negative poissons
ratio - 50– 400 µm – crystallinity of polymer >98% - 9 billion pores /inch2 -
•Wet coagulation - ultrafine pores < 1µm – salt leaching - Requires Precise
control below 3 µm.
•Thermo coagulation - volatile solvent - PU dissolved in methyl ethyl ketone,
toluene, and water, having 15–20% solid
•Foam coating - fluorocarbon (FC) polymer, PU coating – soft n flexible - abrasion
•Radio frequency (RF)/ion/UV or E beaming - Sputtering ofTeflon by Ar gas

10. Application of Polyurethane coating:
• Pore dia of 0.0004 µm possible
•PU-based film designed (Permatex) by J.B. Broadley coated on fabrics offers a
vapor permeability of at least 70%.
•Grabotter membrane (Grabo Ltd.) used in waterproof shoes is a PU-based film.
•Micro porous PU film is being produced by Acordis (Tarka) is applied by a
transfer process from the release paper and it can be applied to almost any type
of substrate.
Knife coating
Floating knife
Extrusion
Calendaring
Curtain coating
Gurave coating
Reverse roll

11. Testing of Breathability of Fabrics using different techniques:
S.no Methodology Standard Purpose
1 Sweating Guarded Hot Plate
Tests
(ISO 11092, ISO
1999, and ASTM F
1868)
Measurement of thermal and water-vapor resistance under
steady-state conditions
2 Upright Cup Method ASTM E96 Water Vapor Transmission of Materials , permeability,
plastics (general), plastic sheet and film, sheet material3 Inverted Cup Method ASTM E96
4 Desiccant Inverted Cup Test
Method
E96 M-05
5 Dynamic Moisture
Permeation Cell Test
ASTM F 2298
Standard Test Methods for Water Vapor Diffusion
Resistance and Air Flow Resistance of Clothing Materials
Using the Dynamic Moisture Permeation
6 Moisture vapor transmition
cell
ASTM D1653 - 13 Moisture vapor transmition behavior of fabric
7 Dynamic moisture
permeable cell
ASTM F2298-
03(2009) e1
Moisture transmition capability of cell

12. Relative water vapor permeability (%):
Heat loss when the fabric is placed on the measuring head X 100
Heat loss from bare measuring head
The main requirements for WVPI are based on
•Water vapor permeability index percentage.
•Resistance to water penetration.
•Cold cracking temperature.
•Surface wetting (spray rating) after cleaning.
For a typical breathable fabric the acceptable parameters should have
•Water-vapor permeability (min 5000gm-2 for 24 hrs)
•Water proofness min 130 cm (hydrostatic pressure)
•Wind proofness less than 1.5 ml/cm2/second @ 1M bar

13. Water Proof rating:
Waterproof Rating
(mm)
Resistance provided Withstand capabilities
0-5,000 mm
No resistance to some resistance
to moisture
Light rain, dry snow, no pressure
6,000-10,000 mm
Rainproof and waterproof under
light pressure
Light rain, average snow, light pressure
11,000-15,000 mm
Rainproof and waterproof except
under high pressure
Moderate rain, average snow, light pressure
16,000-20,000 mm
Rainproof and waterproof under
high pressure
Heavy rain, wet snow, some pressure
20,000 mm+
Rainproof and waterproof under
very high pressure
Heavy rain, wet snow, high pressure
For example : 10000/10000 – First number represents water proofness of fabric and
second number represents breathability of the fabric. Higher the value better is the result

14. Application
3M incise tape 9948Neo-G knee support
Breathable snow protect
mountain wear
Fire man
Protective
Apparel
Racer Suite
Ventile Roofing Membrane
Somatex Casing layer
14/3/2014

15. Conclusion:
• Comfort property has become the most prime objective of the
buyer/consumer where breathability of the fabric with water
proofness has been the primary importance in areas that do not
enjoy the evergreen nature.
• Extensive research is required to understand the relationship
between segmental ventilation and local comfort of the fabric
subjected to active usage of the person.

16. Thanks to all.