日本レオロジー学会誌 Vol. 45(2017) No. 3

Dynamic viscoelastic properties of standard pullulan samples with different molecular weights and narrow molecular weight distributions in ionic liquids are measured in non-entangled region over a wide range of chain overlapping (1 ≤ C [η] ≤ 12.6) and compared with Rouse-Zimm (RZ) theory with and without introducing correction term called long time (LT) term, proposed by Osaki et al. (J. Polym. Sci., Part B, Polym. Phys. Ed., 39, 211-217, (2001)). When chains are overlapped (say 2.5 ≤ C [η]), loss modulus data (G") can be well expressed by the RZ theory with experimentally determined longest relaxation time τ_RZ while storage modulus (G') was larger than the calculation. However, addition of LT term made reasonable correction for calculation of G' similar to the results for standard polystyrenes. To apply the RZ fitting for M_w estimation of unknown sample (fitting G" by RZ theory), estimation error for τ_RZ and resulting M_w are examined. At high C [η], relative error of estimated M_w was about 15%, as long as τ_RZ can be determined with small error and coincidence of τ_RZ and the longest Rouse relaxation time calculated from estimated M_w is confirmed. At lower C [η], this method tend to underestimate M_w and the error become larger.

To address the dual problems of the depletion of natural resources and the environmental impact of a growing volume of wastes, effective recycling of various products and materials has become an important challenge. Especially, the amount of plastic waste is extremely large, and thus it is very important to establish effective process of recycling them as soon as possible. However, the mechanical properties and durability properties of the products made from waste plastics are inferior to those of products molded from virgin plastics, and thus their application area is presently limited. The reason of above phenomena has been thought to be caused by chemical degradation. However, we recently found that the main cause of this inferior property was reproducible physical degradation from the investigation of pre-consumer recycle polypropylene. In this study, we used recycled post-consumer container and container and packaging plastics (polypropylene component was sorted) and investigated that the physical properties of them were reproducible or not. And we found that the tensile mechanical properties of them were reproducible almost to the virgin revel by changing molding conditions. This results indicate that in the case of recycled post-consumer container and packaging plastics, they are not chemically degraded and can use to value-added fields.

In our previous study, it was found that pattern electrodes with fine projections enhanced the electrorheological (ER) effect of particle suspensions whose particle content was low. In addition, the chain structures between electrodes were different between pattern and plate electrodes. In this study, we focused on the behavior of ER fluids under low electric field and measured the voltage when chain structures of poly(ethylene glycol) (PEG) / silicon oil suspensions could be observed with the naked eye. In case of the 10 wt% PEG (38 - 75 μm) particles / oil (50 cSt) suspension between pattern electrodes, the chain structures appeared at 85 V. This value was lower than the sample between plate electrodes (125 V). In addition, the voltage became higher by increasing the viscosity of oil and particle content. Furthermore, decreasing particle size also raised the voltage. When electric field is applied to PEG suspensions, particles aggregate on the negative electrode by electrophoresis. We considered that the higher voltage was required to create PEG chain structures when the effect of electrophoresis became stronger.