Wanjie Wang

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 (GN0 and entanglement molecule weight (Me) were calculated.

A rheological method for the determination of “super toughness point” of polymer blends: A blend system of nylon1212 with maleated poly(ethylene-octene)

The rheological behavior of a reactive blend system of nylon1212 with maleic anhydride grafted poly(ethylene-octene) was studied in correlating with the key mechanical parameters. Results illustrated that the “gel points” acquired from the dynamic rheological data and the “super-toughness points” of the blends have a corresponding relationship. Thus, just by simple composition designs and a small amount of samples, the super-toughness point could be conveniently determined by the dynamic rheological measurements. Furthermore, special “double network” morphology at the gel point was directly observed for the first time and the new mechanism of super-toughness has also been discussed.