Composition effect on the core–shell morphology and mechanical properties of ternary polystyrene/styrene–butadiene rubber/polyethylene blends

Abstract

The morphology of ternary polystyrene/styrene-butadiene rubber/polyethylene (PS/SBR/PE) blends has been investigated in the limits of a constant content of the major component (PS; 75 wt%) while changing the weight ratio of the two minor constitutive polymers. A core-shell structure for the dispersed phase has been predicted from the spreading coefficients and observed by transmission electron microscopy. Actually, upon increasing the relative content of PE with respect to SBR, the structure of the dispersed phase changes from a multicore structure to a PE/SBR core-shell morphology. The size of the PE subphase in the mixed dispersed phase increases sharply at a PE content that corresponds to phase inversion in the parent SBR/PE binary blends. The ultimate mechanical properties of these blends are sensitive to the strength of the SBR interphase between PS and PE. Some synergism has been observed in the PE/SBR composition dependence of the tensile strengths at yield and break.

Ternary polymer blend with core–shell dispersed phases: effect of the core-forming polymer on phase morphology and mechanical properties

“…1). Thus, small change in the surface tension of PO does not expectedly change the positive sign of the spreading coefficient calculated for the PS/SBR/LDPE system [10]. As a rule, the average number of polyolefinic subphases per SBR dispersed phase is very close to 1 when calculated by image analysis.…”

“…11 illustrates this extreme case. For the cases (1) and (2), the modulus can be calculated by the Kerner equation on the assumption that the stress distribution is uniform throughout the PS and the SBR phases and that the average stress is actually the macroscopic stress in the PS/SBR binary blend of the same relative content as in the ternary blend [10]. Therefore, the modulus of the binary PS/SBR blends has been calculated by Eq.…”

“…In a previous communication [10], the morphology of polystyrene/styrene butadiene rubber/low density polyethylene (PS/SBR/LDPE) ternary blends has been investigated in relation to the weight ratio of the SBR and LDPE minor components which are dispersed in the PS matrix. In agreement with λ 31 , a core-shell structure has been observed for the dispersed phase, LDPE forming systematically cores in the SBR phase.…”

Dependence of phase morphology and mechanical properties of PS/SBR/PE ternary blends on composition: transition from core–shell to triple-phase continuity structures

“…Actually, these properties for the PS/SBR/PE ternary blends are not basically different from those ones for either the PS/SBR or PE/SBR binary blends of the same content of dispersed (SBR) phase. It must be noted that a previous communication [12] showed that at constant content of the matrix (PS; 75 wt%) the SBR/PE composition of the core-shell dispersed phase had strong influence on the mechanical properties. In that case, the effect of the core on the stress-strain measurement was not masked by the SBR shell.…”

“…A previous paper from this laboratory has focused on the morphology and mechanical properties of ternary polystyrene/styrene-butadiene rubber/polyethylene (PS/SBR/PE) blends [12]. The range of compositions investigated was such that the content of the major phase (PS) was kept constant, in contrast to the ratio of the two minor (PE and SBR) components that was changed.…”