Fibres from mixtures of rigid-chain and flexible-chain polymers

Abstract

In the present article we make an attempt to generalize the incomplete literature material on the characteristics of mixtures of polymers where at least one of them is a rigidchain polymer, as applicable to fibre-forming polymers and to fibres based on them. From the behavioral features of the polymer mixtures and the complex of properties acquired by the mixed fibre, it seems advisable to subdivide mixtures of flexible- and rigid-chain polymers on the basis of the ratio of the two components in them (systems with a large and with a low content of the rigid-chain polymer). Phase Equilibria in Three-Component Systems Involving a Solvent and Rigid- and FlexibleChain Polymers. PPTA and other rigid-chain polyamides are lyotropic liquid-crystalli ne (LC) substances, since they do not melt up to the decomposition point and form the LC state only in solution. Another group of fibre-forming LC polymers, mainly aromatic polyesters and polyazomethines, is characterized by a weaker intermolecular interaction due the absence of hydrogen bonds, and melts at lower temperatures; they belong to the thermotropic substances. A transition from the crystalline to the LC state is effected on the melting of these substances. Phase separation has been studied as yet only for the lyotropic polymers. As concerns mixtures involving thermotropic polymers, investigation of these is attended with large difficulties, caused by the occurrence of slow exchange reactions between the heterochain polymers in the case where they are mixed at high melt temperatures. Thereupon, apparently a physical mixture of the polymers can exist only for a short time, being transformed with the passage of time into a block-copolymer and a true statistical copolymers. The phase equilibrium state in a solution of a rigid-chain polymer with rod-like mole