DENSITY MEASUREMENT
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)
- Cotton and other cellulosic fibers 1.54
- Acetate fibre 1.32
- Silk 1.32
- Wool 1.32
- Nylon 1.14
- Polyester 1.38
- Acrylic 1.17
STAINING TEST
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
- Scoured cotton Lilac
- Bleached cotton Violet blue
- Mercerized cotton Purple
- Viscose Rayon Bright pink
- Cuprammonium rayon Bright blue
CHEMICAL TEST
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
- Sodium hypochlorite (5% chlorine, 25°C) Wool and Silk
- Cold 70% Sulphuric acid Silk
- 75% Sulphuric acid (at 25°C) Cellulosics
- Sodium zincate (cotton insoluble) Viscose
- Glacial acetic acid (at 25 C) Acetate, Triacetate
- Cold acetone Acetate, Triacetate
- Methylene chloride (at 25°C) Triacetate (acetate insoluble)
- Hydrochloric acid (1:1Xat 25°C) Nylon 6, Nylon 66
- Formic acid (at 25°C) Nylon 6, Nylon 66
- DMF cold Acrylic
- DMF at a boil (Nylon 66 insoluble) Nylon 6
- Ammonium thiocyanate (70% solution at a boil) Acrylic
- Meta cresol, 95°C Polyester
- Chloro-phenol (at a boil) Polyester
- Meta xylene (at boil) Polypropylene