Density and chemical test of textile fiber


A rough estimation of density can also identify the fibres. The chemicals taken for density will be inert chemicals like benzene, carbon tetrachloride, toluene with a known density. When the density of the fiber is heavier than the density of the chemical, the fiber will sink to the bottom.
On the other hand, when the density of the fiber is lower than the density of the chemical, it will float at the top.

The density of some of the fibres are mentioned in Table

Fibre                                                 Density (g/cc)
  1. Cotton and other cellulosic fibers     1.54
  2. Acetate fibre                                     1.32
  3. Silk                                                   1.32
  4. Wool                                                 1.32
  5. Nylon                                                1.14
  6. Polyester                                          1.38
  7. Acrylic                                               1.17

Density and chemical test of textile fiber


When different types of fibres are treated with, a chemical, they will produce different coloration.
The chemical will be- 20 ml of solution A containing an equal amount of zinc chloride and water and 0.2 ml of solution B containing potassium iodide and water in the proportion of 1:5.
When cellulosic fibers are treated with shirt stain A for one minute and then rinsed, different fibres will have different coloration, as mentioned in Table

The coloration of cellulosic fibres with shirt stain A

  1. Scoured cotton                    Lilac
  2. Bleached cotton                  Violet blue
  3. Mercerized cotton               Purple
  4. Viscose Rayon                    Bright pink
  5. Cuprammonium rayon         Bright blue


The solubility of fiber in a particular chemical reagent is a means of identification. The fiber can be placed in a chemical, at a particular temperature and the solubility will confirm the type of fiber. The solvents of each of the fibres are shown in Table

Solvents of different fibres

     Chemical                                                         Fibres
  1. Sodium hypochlorite (5% chlorine, 25°C)       Wool and Silk
  2. Cold 70% Sulphuric acid                                 Silk
  3. 75% Sulphuric acid (at 25°C)                         Cellulosics
  4.  Sodium zincate (cotton insoluble)                  Viscose
  5. Glacial acetic acid (at 25 C)                            Acetate, Triacetate
  6. Cold acetone                                                   Acetate, Triacetate
  7. Methylene chloride (at 25°C)                           Triacetate (acetate insoluble)
  8. Hydrochloric acid (1:1Xat 25°C)                       Nylon 6, Nylon 66
  9. Formic acid (at 25°C)                                        Nylon 6, Nylon 66
  10. DMF cold                                                            Acrylic
  11. DMF at a boil (Nylon 66 insoluble)                     Nylon 6
  12. Ammonium thiocyanate (70% solution at a boil) Acrylic
  13. Meta cresol, 95°C                                                 Polyester
  14. Chloro-phenol (at a boil)                                       Polyester
  15.  Meta xylene (at boil)                                        Polypropylene

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