Modelling of the High‐Impact Polystyrene Morphogenesis

Abstract

Summary: High-impact polystyrene (HIPS) is a hetero-phase polymer with the so-called salami morphology. Salami morphology is formed by a continuous PS phase containing micron-sized PB domains. PB domains contain submicron-sized irregular PS occlusions. In our modeling work we addressed several weak points of Cahn-Hilliard model of HIPS salami morphology evolution. The weakest point of Cahn-Hilliard model is the inherently present Ostwald ripening destabilizing or competing with graft-stabilized domains. Two mechanism of formation of HIPS morphology are supported by the model: (i) encapsulation of graft-stabilized PS-rich domains in PB particles, and (ii) polymerization of styrene dissolved in PB-rich phase and subsequent phase separation leading to PS occlusions in PB domains.

Polystyrene Microstructured Foams Formed by Thermally Induced Phase Separation from Cyclohexanol Solution

“…Here we restrict ourselves to a comparison of characteristic sizes of produced morphologies. For a detailed investigation of the morphology type and controlling parameters see available literature …”

“…This formulation of the Cahn–Hilliard model assumes: (i) incompressibility of the polymer solution; (ii) no convection in the mixture (i.e., low Peclet number); (iii) isothermal mixture without any thermal diffusion effects; and (iv) constant and equal diffusivities of species representing the inverse drag force according to Maxwell–Stefan diffusion model of binary systems. Details of the model implementation can be found in our articles . Other formulations of the Cahn–Hilliard model accounting for various phenomena can be found in literature …”

“…Details of the model implementation can be found in our articles. [6,27,28] Other formulations of the Cahn-Hilliard model accounting for various phenomena can be found in literature. [29][30][31][32][33][34][35][36][37][38] The partial differential Equation (7) was solved after the domain discretization in two spatial and one time dimension by Livermore solver [39] implementation in the ODEPACK library in Fortran.…”

“…For a detailed investigation of the morphology type and controlling parameters see available literature. [6,27,28,[30][31][32][34][35][36][37][38]40,41,[47][48][49][50][51] Since the dynamics of the phase separation is influenced by the constitutive equations for the fluxes and by the value of diffusion coefficient, [6] we restrict ourselves to the comparison of final morphology profiles. This approach is also chosen by the fact that the kinetics of the spinodal decomposition is qualitatively well described by Cahn-Hilliard model but the lack of data about the diffusivities prohibits quantitative predictions of morphology evolution dynamics.…”

Mechanisms and Conditions that Affect Phase Inversion Processes. The Case of High‐Impact Polystyrene

“…The mechanism and conditions that dictate the phase separation of this system have not been demonstrated yet. This reaction‐induced phase separation may either follow a binodal or a spinodal decomposition and, although some authors argue that it can only follow the spinodal line, they report no actual measurements to support their views, which are often based on the curing reaction of epoxy resins. These reactions are performed without agitation and thus fail to provide the necessary energy input to favor nuclei formation (which is the accepted mechanism of binodal decomposition ), and so proceed following the spinodal.…”