Morphologies and Rheological Properties of Ethylene-Propylene Block Copolymers

Abstract

Ethylene-propylene block copolymer (EPBC) is mainly composed of two component polymers, polypropylene (PP) and ethylene-propylene rubber (EPR). The dependence of morphologies as well as dynamic moduli of EPBC on the molecular characteristics of the components were investigated for four EPBC samples. From the results of the temperature dependence of dynamic moduli and the morphologies, it was suggested that the samples have heterogeneous structure composed of a dispersed EPR phase and a PP matrix phase in which a part of the EPR component dissolves. The concentration of dissolved EPR in the matrix increases with increasing propylene content of the EPR component. For the melts of the EPBC samples containing the EPR component of higher than about 70 wt% propylene contents, a secondary plateau was observed in the long time region on the dynamic viscoelasticity curves. To clarify the origin of this slow relaxation, the dynamic viscoelasticity were compared with three theories: Palierne's emulsion model, the thermal diffusional model and the blending rule. The comparison suggested that the blending rule can well explain the secondary plateau behavior originated from the existence of the high molecular weight EPR dissolved in the PP matrix.

Surface tension and interfacial tension of polyolefins and polyolefin blends

“…For copolymers with propene, the range of value of interfacial tension with iPP is between 0.5 mN/m and 1.1 mN/m at similar temperature (190-200 C) and compositions (24-27 wt%) though this can be only estimated from the density in the paper. 22,23 For copolymers with 1-butene, the same authors give values of 0.9 mN/m but the composition is not clearly indicated in the paper (presumably 24 wt% of butene according to density). Other reported values range from 0.6 mN/m (19.4 wt% butene) and 1 mN/m (12 wt% butene).…”

Nanoparticle retarded shape relaxation of dispersed droplets in polymer blends: an understanding from the viewpoint of molecular movement

“…The dispersed droplet/matrix morphology, with the minor component as dispersed droplets in a continuous phase of the major component, is oen observed. [5][6][7][8][9] Polymer blends with dispersed droplet/matrix morphology oen exhibit high elasticity and a long relaxation time, [10][11][12][13] and this long relaxation time has been considered to correspond to the process in which the deformed droplets recover their original spherical shapes. 14,15 Due to the deformability of liquid interface, the dispersed droplets deform signicantly in ow elds during mixing, leading to an increase in interfacial area between components.…”