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Mesomorphic films have been prepared from isotropic solutions of cellulose diacetate and triacetate in N-methylpyrrolidone by evaporating the solvents methylene chloride or methyl ethyl ketone. The films have high mechanical properties and are able to fibrillate as a result of realization of a liquid-crystalline state. In heat stretching of the films up to 300%, structural rearrangements take place which are characterized by reorientation of rod-like structures in the direction of deformation. The finer anisometric elements located in such structures are oriented perpendicularly to the direction of stretch.

The nature of relaxation processes in two types of hydrocellulose fibres has been examined, plus their connection with strength properties.

It is possible to increase the molecular orientation in POD fibres by using orientation actions on the spun fibre in the section which is most favorable for polymer orientation.

Five relaxation transitions have been detected for PABI rigid-chain polymer by the method of dynamic mechanical losses, at 50, 140, 220, 380, and 480°C. An effect of relaxation transitions on the temperature dependence of strength has been demonstrated.