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Mechanical properties of SBS block copolymers. I. Effect of structure and selective solvent casting on dynamic viscoelasticity
Author(s) -
Kalfoglou Nikos K.
Publication year - 1979
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1979.070230816
Subject(s) - cyclohexane , copolymer , materials science , styrene , viscoelasticity , dynamic mechanical analysis , solvent , polymer chemistry , toluene , dynamic modulus , composite material , chemical engineering , polymer , organic chemistry , chemistry , engineering
Thermomechanical spectra of poly(styrene‐ b ‐butadiene) copolymers were obtained at 110 Hz and between −120 and 120°C. The molecular parameters studied were the styrene content (35%–45%) and, at constant composition (39% styrene), the length of the copolymer blocks. The films studied were cast from selective solvents, methyl ethyl ketone (MEK), cyclohexane, and toluene, a common solvent. MEK‐ and toluene‐cast films were quite similar in their dynamic viscoelasticity and more rigid than the corresponding cyclohexane‐cast films. Solvent differentiation was more evident at the higher styrene content. No evidence of a relaxation due to a mixed interphase was obtained. At constant composition a morphological transformation takes place when the length of the blocks exceeds a certain limit; this affected the dynamic modulus of the cyclohexane‐cast films. The results were analyzed using two‐phase models proposed by the composite theory. For some samples results on the effect of annealing and prestretching are also reported.
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