Water Repellent and Water Proof Finishes

Certain end use of textiles such as umbrella cloth, swim suit, sports wear, rain coat, tarpaulin etc. need water repellency or water proofing.
When a uniform coating of suitable substances such as rubber is produced on the surface of the fabric, the interstitches between the warp and weft yarns are blocked by the continuous film of that substances and water will not pass through the fabric. This phenomena is known as water repellent or water proof finishes.
water repellent and proof structure
However, the rubber treated fabric becomes impermeable to air as well as moisture, when a treated fabric is impermeable to water and air then this type of finishes is called water proof finish.
When the protection from water is desired as in apparel purpose, the treated fabric should be permeable to air but not in water. This type of finish is called water repellent finish.
Method of Application: Water repellent or proof finishes are produced by the use of water insoluble metal soap like aluminum stearate. This is usually done by treating the fabric first with an aqueous solution of the metal that is aluminum acetate or lead acetate, that passing through water soluble soap like sodium stearate.
chemical-bond-of-water-proof-and-repellent-finish
Paraffin wax or vegetable waxes are used along with aluminum stearate to increase the water repellent effect.
schematic-diagram-of-water-repellent-and-proof-finish
Agents for Water Repellent and Water Proof Finishes: The following agents are commercially used for water repellent or proof finishes. They are,
  1. Bteanoxy methyl pyridinium chloride 
    bteanoxy-methyl-pyridinium-chloride
  2. Bteanamide= C17H35CONH2.
  3. Methylate methylol stearamide = C17H35CONCH2OH
  4. Methylene bis-stearamide 
    methylene-bis-stearamide
  5. Methylol stearamide 
    methylol-stearamide

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