Influence of Molecular Weight and Composition on the Morphology and Mechanical Properties of SBS-Polystyrene-Mineral Oil Blends

Linda S. Flosenzier, John M. Torkelson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The relationship between the tensile properties and morphology of styrene‒butadiene‒styrene (SBS)‒mineral oil‒polystyrene blends has been evaluated. The SBS‒mineral oil system (Kraton D2104, 21 wt % total styrene content, Shell Chemical Co.) exhibits a morphology of polystyrene spheres in a continuous butadiene‒oil matrix, and the mechanical properties are characteristic of a cross-linked rubber. When the mineral oil is removed, the polystyrene domains become cylindrical and the mechanical properties correspondingly show increased stresses and a reduced ultimate elongation. Monodisperse polystyrene was blended into the SBS‒mineral oil system: mineral oil is solubilized exclusively into the butadiene phase of the copolymer and the SBS‒mineral oil‒homopolymer blends seem to behave similarly to SBS‒homopolymer blends. As the total styrene content is increased through blending, a transition from a spherical to cylindrical styrene domain morphology is observed. Higher styrene content blends also exhibited yielding and necking, which are indications of polystyrene domain continuity. The solubility limit of the homopolystyrene in the copolymer morphology was dependent on homopolymer molecular weight. Only the lowest molecular weight polystyrene blend showed no evidence of homopolymer segregation at the highest total styrene content (40 wt %). For polystyrene molecular weights greater than the styrene block length of the copolymer, the solubility limit was significantly reduced. The dependence of mechanical properties on homopolymer molecular weight and morphology is more sensitive than has previously been observed.

Original languageEnglish (US)
Pages (from-to)735-742
Number of pages8
Issue number2
StatePublished - Mar 1 1992

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry


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