RELATION BETWEEN TEXTURE AND RHEOLOGICAL PROPERTIES OF MESOPHASE PITCH

The type and extent of plastic deformation of mesophase pitch (MPP) pr epared from coal tar pitch free of quinoline-insoluble matter (QI) at temperatures <400 degrees C in a stirred reactor were studied. The pla stic behaviour of cooled and subsequently reheated MPP depends on the ratio of anisotropic mesophase to isotropic matrix and the character o f the continuous phase. When the continuous phase is the matrix, MPP i s fusible if the mesophase is finely dispersed, but it merely softens if the mesophase is coarsely dispersed. When the continuous phase is t he mesophase, MPP softens only and exhibits intermediate or low deform ability, depending on the size of domain structures and the degree of anisotropy of the mesophase. The transformation of mesophase from disp ersed into bulk form may be interpreted as a reversible transition of a sol-gel system.