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Water repellency of fabrics

This document discusses water repellency in fabrics. It defines water repellent fabrics as those where water drops roll off rather than soaking in. A fabric's water resistance depends on fiber surface, porosity, and water impact force. It distinguishes water-repellent fabrics, which are permeable but resist water under low pressure, from waterproof fabrics, which have fewer pores and resist water under high pressure. The document outlines different types of water repellent finishes and several test methods used to evaluate water repellency in fabrics.

Engineering◦
Welcome to our presentation Md. Yousuf Hossain ID:131-23-3294
Topic Water repellency of fabric
Definition • water repellent fabrics are those which resist being wetted by water, water drops will roll off the fabric. A fabric’s resistance to water will depend on • the nature of the fiber surface, • the porosity of the fabric • the dynamic force behind the impacting water spray.
Distinguish between water-repellent and water-proof fabrics water-repellent fabrics water-proof fabrics i. Water Repellent Fabrics have open pores and are permeable to air and water vapour. i. Water-Proof Fabrics have fewer open pores and are less permeable to the passage of air and water vapour. ii. Water-repellent fabrics will permit the passage of liquid water once hydro-static pressure is high. ii. Water-Proof Fabrics are resistant to the penetration of water under much higher hydrostatic pressure. iii. A fabric is made water-repellent by depositing a hydrophobic material on the fibre’s surface. iii. however. Waterproofing requires filling the pores as well as depositing a hydrophobic material on the fibre’s surface.
Water-repellent fabrics water-proof fabrics
necessity of water repellency property in fabrics
necessity of water repellency property in fabrics
necessity of water repellency property in fabrics
Md. Shamim Hossain Id: 131-23-3328
Water repellent finishes • Water repellents are chemical finishes • Resist the penetration of water into the fabric • Permits the passage of moisture or air through the fabric • There are three types of water repellent finishes:  non-durable finishes  semi-durable finishes  durable finishes
Non-durable finishes • This type of water repellent finish is usually based on paraffin wax-aluminum acetate emulsion. • non-durable finishes are easily removed in laundering or dry-cleaning. • non-durable finishes do not provide satisfactory resistance to liquids. • Examples: Aquarol AX, Aridex WP, Dryon, Repelex etc
Semi-durable finishes • These are wax or salt solutions. • They are emulsified off the fabric in laundering. • They ate resistant to dry-cleaning. • Examples: Bishopel, Dryon A-B, Nalan W etc
Durable finishes • There are several types of durable water repellents, such as 1. Pyridinium compounds  It is Applied to cotton, linen & viscose rayon fabrics.  It also endures repeated washings as well as dry-cleaning.  It improves the fabric’s appearance. 2. Melamine resins & stearamides compounds  It is used on cotton, rayon etc.  These have excellent repellency and good tolerance to laundering. 3. Silicone compounds  These are excellent water repellents.  The finish is usually more resistance to dry cleaning than to laundering. Examples: Aerotex, Hydro-Pruf, Zelan, Zepel etc.
Md. Jowel Miah Id: 131-23-3377
Several test methods of water repellency of fabrics  AATCC TM22: Water Repellency-Spray Test  AATCC TM35: Water Resistance: Rain Test  AATCC TM42: Water Resistance: Impact Penetration Test  AATCC TM70: Water Repellency-Tumble Jar Dynamic Absorption Test  AATCC TM127: Water Resistance: Hydrostatic Pressure Test
Working procedure of spray test method • Step-1: The sample fabric is mounted on a metal hoop.
Working procedure of spray test method • Step-2: Then the metal hoop attached with sample fabric is fixed on the instrument at 45ᵒ angle.
Working procedure of spray test method • Step-3: Now the beaker is filled with 250 cc water.
Working procedure of spray test method • Step-4: pour the distilled water into the funnel.
Working procedure of spray test method • Step-5: spray the whole quantity of water on the test specimen for a period of 25 - 30 sec.
Working procedure of spray test method • Step-6: After spraying has finished the sample holder is removed and the surplus water removed by tapping the frame 6 times against a solid object.
Assessment technique
Water repellency of fabrics