Strain Induced Plastic-to-Rubber Transition of An SBS Block Copolymer and Its Blend with PS.
CALIFORNIA UNIV BERKELEY DEPT OF CHEMICAL ENGINEERING
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The strain softening phenomenon in polystyrene-b-butadiene-b-styrene and its blends with polystyrenes were investigated by means of electron microscopy and small angle x-ray scattering. Samples were cast from mixed solvents of tetrahydrofuran and methyl ethyl ketone 9010 by volume. The structure of these samples consist of randomly oriented alternating lamellar domains of the two components. Their mechanical behavior is plastic-like in that they exhibit yielding and necking when first stretched to around 200. After the necking has propagated throughout, the samples show typical rubber-like behavior. This phenomenon may be called the strain induced plastic-to-rubber transition, and is believed to occur as a result of structural changes from alternating lamellar domains to fragmented PS domains dispersed in a PB matrix.