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

New types of morphology in immiscible polymers blends, obtained by a process named dynamic quenching process [Cassagnau P, Michel A. French Patent, No 0004420, 6 April 2000], are presented. The dynamic quenching process consists of crystallizing under shear or elongational flows, a semi-crystalline polymer (or solidifying an amorphous polymer) dispersed in melt thermoplastic matrix. Using this new process, polybutylene terephthalate (PBT) and polycarbonate (PC) have been dispersed in an ethylene vinyl acetate (EVA) copolymers matrix in a twin-screw extruder. A coral structure of the PBT domains and a fine nanoscale (100×300 nm2) of PC rods have been so elaborated. The development of the morphology during processing was qualitatively discussed in terms of crystallization under shear or elongational flows of fine PBT droplets dispersed in a melt EVA matrix. Coral PBT structure forms a network-type structure, which confers to the material an yield stress behavior. Considering EVA/PC blends, the mechanism of the morphology development is different. As PC is an amorphous polymer, the viscosity ratio and the elasticity of the PC phase considerably increases with decreasing temperature to the PC glass temperature. Furthermore, the dynamic quenching process can be used as a way to control and to form a rod morphology at high concentrations of PC.