Rayon
This fibre is made from cellulose, i.e., it is a regenerated cellulosic fibre. Its raw material is wood pulp or cotton linters. Pure cellulose is extracted and is reprocessed under controlled conditions to form fibres once again.
Hence the name regenerated fibre. The purified cellulose is treated with chemicals and a thick, viscous honey-coloured spinning solution is obtained. It is then forced through the holes of a spinneret (Fig. 11.5), into a suitable medium so that the liquid flowing continuously through the spinneret holes solidifies into filamenty fibres. Mainly three types of Rayons are known: Viscose Rayon, Cuprammonium Rayon and High-wet-Modulous Rayon. Different chemicals are used for obtaining above types of Rayons.
(a) COMPOSITION:
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Mainly it is cellulose in the regenerated form.
(b) PROPERTIES:
(i) Microscopic Structure: Under the microscope, it is a rod-like structure having uniform diameter and smooth walls. A number of striations are visible in its longitudinal section. (Fig. 11.6)
(ii) Lentgh: It is a long filament fibre.
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(iii) Colour: It is transparent, but desirable colour can be imparted before forcing the solution through the spinneret. This dyeing is called solution dyeing.
(iv) Lusture: It is very highly lustrous. Its lustre can be reduced by adding a delustering agent (titanium dioxide) to the spinning solution.
(v) Strength: It varies from fair to excellent depending upon the process of manufacture. It loses its strength when wet.
(vi) Elasticity: It is generally low.
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(vii) Absorption: Greater than natural cellulose fibres.
(viii) Thermal Properties: Burns very quickly with smell of burning paper. Ironing temperature is 275oF.
(ix) Chemical Resistance: Like cotton, Rayon is easily damaged by acids but it is resistant to normal alkalis.
(x) Dyes: It can be dyed easily with Direct, Vat or Sulfur dyes. It is colorfast to washing and sunlight.
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(c) USES
It is very lustrous and so it was initially called as artificial silk. It is inexpensive fabric for apparel and household use. Also it can be conveniently used for blending with other fibres like Viscose rayon. Mixed with polyst called as artificial silk. It is inexpensive fabric for apparel and household use. Also it can be conveniently used for blending with other fibres like Viscose rayon. Mixed with polyster, the fabric is available by the trade name, lizzy-bizzy.
(d) CARE
It posseses moderatre strength which weakens when wet. Therefore, it needs to be washed with gentle handling. Also it can be dry cleaned.