Influence of Heat Treatment on Mechanical Properties of Polyoxadiazole Yarns and the Relationship of These Properties to Electrical Conductivity in the Carbonized State

The effect of heat treatment of Arselon and Arselon-C polymer yarns in the range 325-400°C on their strength, rigidity modulus, and electrical conductivity followed by carbonization up to 900°C was studied. The minimal strength was shown to correspond to the maximum electrical conductivity at a treatment temperature of ~375°C. The rigidity modulus increased locally if the treatment temperature was increased over 375°C. A hypothesis that the polymer fiber should contain structural units capable of adequately forming carbon phases and ordering them for an efficient transition into carbon fibers was proposed and justified based on an analysis of the fiber mechanical and electrical properties. Results of mechanical tests and electrical measurements were described well in terms of classical and previously proposed models of the fiber as a system, succession, and translation of the fiber properties during heating and carbonization.