Compatibility, steady and dynamic rheological behaviors of polylactide/poly(ethylene glycol) blends

Understanding the rheological behavior of plasticized polylactide (PLA) contributed to the optimization of processing conditions and revealed the microstructure-property relationships. In this study, the morphological, thermal, steady and dynamic rheological properties of the PLA/poly(ethylene glycol) (PEG) blends were investigated by scanning electron microscope, differential scanning calorimeter, and capillary and dynamic rheometers, respectively. The results illuminated that the melt shear flow basically fitted the power law, whereas the temperature dependence of the apparent shear viscosity (eta(a)) or complex viscosity (eta*) followed the Arrhenius equation. Both the neat PLA and PLA/PEG blends exhibited shear-thinning behavior. Because the incorporation of PEG reduced the intermolecular forces and improved the mobility of the PLA chains, the eta(a), eta*, and storage and loss moduli of the PLA/PEG blends decreased. The PEG content (WPEG) ranged from 0 to 10 wt %, both eta(a) and eta* decreased significantly. However, the decrements of eta(a) and eta* became unremarkable when WPEG exceeded 10 wt %. The reason was attributed to the occurrence of phase separation, which resulted in the decrease in the plasticization and lubrication efficiencies. This study demonstrated that the addition of the right amount of PEG obviously improved the flow properties of PLA. (C) 2015 Wiley Periodicals, Inc.