Polyurethane fibres f r o m a h i g h -m o l e c u l a r -w e i g h t p o l y m e r containing not l e s s than 85% (by wt.) polyurethane [1] a r e e l a s t o m e r i e . Having highly-elastic p r o p e r t i e s , these fibres a r e used to p r e p a r e elastic f a b r i c s in making sports clothing, medicinal elastic bandages, bathing suits, j e r s e y s , and socks or stockings.Polyurethane fibres were first produced on an industrial scale in 1959 in the USA by the Du Pont company under the t r a d e n a m e " L y c r a " [2, 3]. At p r e s e n t they a r e produced in West G e r m a n y (Dorlastan, Enkaswing), Japan (Opelon, Espa, Neolon), Great Britain (Spanzel), Belgium (Sarlan), Italy (Lunel), and the USSR (Polyurethane Fibre). Polyurethane f i b r e s a r e spun by s e v e r a l methods, f r o m a p o l y m e r p r e p a r e d f r o m v a r i o u s r a w m a t e r i a l s . In 1977, worldwide, about 10,000 m e t r i c tons of polyurethane e l a s t o m e r i c fibres, was produced; by 1980 their output had r i s e n to 20,000 m e t r i c tons [4].