PECULIARITIES OF RHEOLOGICAL BEHAVIOR OF FILLED POLYMER MELTS IN UNIAXIAL STRETCHING

The peculiarities of rheological behavior of filled polymer melts in u niaxial extension in a wide range of strain rates (from 2 x 10(-5) to 1 x 10(-1) s-1) have been studied. Linear polyethylene and 1,4-polybut adiene containing up to 21.5 vol.% of carbon black, silica, calcium ca rbonate or glass fibers were used. It has been found that the transiti on from uniform to nonunion stretching due to the neck formation is ty pical of all specimen compositions, when they approach steady-state st raining. Depending on the structure and rheological characteristics of the compositions general conditions for this transition have been est ablished. The general regularities for varying the rheological charact eristics of filled polymers in the course of their uniform stretching have been recognized. These regularities depend on the molecular chara cteristics of the polymer matrix and the presence in the compositions of the structural framework of high disperse filler or the network for med by the entangled fibers. Using polyethylene compositions it has be en shown that the introduction of small amounts of disperse or fibrous fillers can give rise to acceleration of the relaxation process in fi lled polymers.