Phase behavior and its viscoelastic response of polylactide/poly(epsilon-caprolactone) blend
作者：Wu, Defeng，Zhang, Yisheng，Zhang, Ming，Zhou, Weidong
關鍵字：Experimental study ; Modeling ; Temperature effect ; Phase reversal ; Composition effect ; Viscoelasticity ; Rheological properties ; Molten state ; Morphology ; Lactic acid polymer ; Heterogeneous mixture ; Polymer blends ; Polycaprolactone ;
論文來源：期刊
具體來源：European Polymer Journal
發表時間：2008年
Polylactide (PLA)/polycaprolactone (PCL) blends with various blend ratios were prepared via melt mixing. The morphology, linear and non-linear viscoelastic properties of the blend were studied using scanning electron microscope (SEM) and cone-plate rheometer. Three typical immiscible morphologies, i.e., spherical droplet, fibrous and co-continuous structure can be observed at various compositions. The elasticity ratio was proposed to play an important role together with the viscosity on the phase inversion because PLA/PCL blend presents a high viscosity ratio between two components. Two emulsion models were used to predict the linear viscoelastic properties of the blend with various morphologies. The Palierne model gives better fit compared with the G-M model, but both fail to predict the viscoelastic properties of the co-continuous blend. The viscoelastic behavior of those blends shows different temperature dependence due to their different morphologies. The principle of time-temperature superposition (ITS) is only valid for the co-continuous blend while fails with the rheological data of those blends with discrete spherical and fibrous domain structure. Moreover, although the discrete phase is difficult to be broken up due to the high viscosity ratio of the systems, the change of viscoelastic responses of those blends before and after preshear shows large difference, indicating that different morphologies have different sensitivity to the steady shear flow.