Superstructure formation in thermoplastic elastomer and oil systems. Formation of a novel microcellular porous structure

Abstract

A novel microcellular porous structure, the product of a small proportion of a semi-crystalline thermo-plastic elastomer (TPE) and a large proportion of low molecular weight oil, is examined. The structure is formed by the phase separation of a homogeneous mixture of TPE and oil. The system exhibits a unique three-dimensional continuous polymer network consisting of interconnected spherical cells of a few tens of micrometers in diameter. The detailed phase separation process is investigated utilizing optical microscopy, SEM, and DSC. A modulated structure, apparently attributable to spinodal decomposition, is observed in the initial stage of phase separation. However, during its evolution, this structure evolves into a clear network structure of a polymer-rich phase and clusters of a spherical oil-rich phase. Time evolution of D of a typical structure during the phase separation process at constant temperature is estimated to be D ∼ t1 in the initial stage and D ∼ t1/3 in the late stage. The character and role of differences in Mw of components in the phase separation of the TPE/oil system are discussed in relation to the results of other studies.