Linear viscoelasticity, probe tack, and extrusion flow results of SEBS copolymers

Microphase-separated poly(styrene-b-ethylene-co-butyleneb-styrene) copolymers of different molecular weights with polystyrene (PS) volume fraction φ = 0.30 are investigated. Linear dynamic viscoelastic data reveal the blocking effect of the ordered PS microdomains, which produces a predominantly elastic response at low frequencies, associated with a mechanical relaxation. These results are correlated with tack and extrusion flow measurements, which involve polymer/metal adhesion processes. Nonlinearity implied in some experiments alters the ordered morphology of low molecular weight samples producing a viscous dominant behavior. Dissipation is reflected in viscous-like adhesion and lack of viscoplastic response in extrusion flow experiments. For the highest molecular sample, only a rubbery or entangled state (G′ > G′ and G′ > 10⁵ Pa) is observed in the linear viscoleastic regime. This is associated with the lack of adhesion seen in both, probe tack experiments and capillary flow measurements. This lack of adhesion gives rise to a plug-flow as the polymer slips in the capillary wall. POLYM. ENG. SCI., 50:1449-1456, 2010.