Study on the viscoelastic behavior of SEEPS block copolymer based on a modified BSW model
Studies on the viscoelastic behavior of styrene-[ethylene-(ethylene-propylene)]-styrene block copolymer (SEEPS) were carried out, and some characteristic viscoelastic parameters were calculated. The longest relaxation time τmax was obtained through simulating the relaxation spectrum on the basis of a modifiedBaumgaertel-Schausberger-Winter (mBSW) model. The results revealed that there exists a “second plateau” in the low frequency region of the master curves. The reason for this phenomenon is attributed to the entanglement of macromolecular chains. It is suggested that the hard blocks, polystyrene, act as entanglement points, resulting in a topology restraint to the movement of macro-molecular chains. Meanwhile, it is found that the horizontal shift factors (aT) vs temperature in the master curve could be fitted to theWilliams-Landel-Ferry (WLF) equation andArrhenius equation respectively and the flow activation energy (Ea) is 127.88 kJ/mol. In addition, the plateau modulus (GN 0 and entanglement molecule weight (Me) were calculated.
KeywordsSEEPS time-temperature superposition principle dynamic viscoelastic behavior relaxation time spectrum
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