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(d) Super-drawing technique [1]
In this technique, no molecular orientation is involved. Staple fibre with linear density less than 0.5
dtex can be produced with high drawing ratios. This technique is based on the principle that yarn can
be stretched as much as 10-75 times; much beyond their conventional draw ratios (3-6 times) if the
drawing is carried out at a minimum crystallising temperature and at special selected drawing
conditions, including the temperature range and the type of heating the fibre.
(e) Sheath-core spinning method [1]
In this method, two different polymers are mixed, melted, and mix-annealed under specified
conditions. The conjugate fibre comprising of a concentric circular sheath and a core is manufactured,
and the sheath portion is removed to form ultra-fine fibres.
(f) Some other methods [1]