New morphologies in immiscible polymer blends generated by a dynamic quenching process

New types of morphology in immiscible polymers blends, obtained by a proces s named dynamic quenching process [Cassagnau P, Michel A. French Patent, No 0004420, 6 April 2000], are presented. The dynamic quenching process consi sts of crystallizing under shear or elongational Rows, a semi-crystalline p olymer (or solidifying an amorphous polymer) dispersed in melt thermoplasti c matrix. Using this new process, polybutylene terephthalate (PBT) and poly carbonate (PC) have been dispersed in an ethylene vinyl acetate (EVA) copol ymers matrix in a twin-screw extruder. A coral structure of the PET domains and a fine nanoscale (100 x 300 nm(2)) of PC rods have been so elaborated. The development of the morphology during processing was qualitatively disc ussed in terms of crystallization under shear or elongational Rows of fine PET droplets dispersed in a melt EVA matrix. Coral PET structure forms a ne twork-type structure, which confers to the material an yield stress behavio r. Considering EVA/PC blends, the mechanism of the morphology development i s different.. As PC is an amorphous polymer, the viscosity ratio and the el asticity of the PC phase considerably increases with decreasing temperature to the PC glass temperature. Furthermore, the dynamic quenching process ca n be used as a way to control and to form a rod morphology at high concentr ations of PC. (C) 2001 Elsevier Science Ltd. All rights reserved.