Dynamic mechanical properties of PLA/PHBV, PLA/PCL, PHBV/PCL blends and their nanocomposites with TiO2 as nanofiller
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The effect of blending and the addition of small amounts of TiO2 nanoparticles on the dynamic mechanical properties of PLA/PHBV, PLA/PCL and PHBV/PCL blends is reported in this paper. The storage modulus of the PLA/PHBV blends was higher than those of both PLA and PHBV in the temperature region below the glass transition of PHBV, but the PLA/PCL and PHBV/PCL bends did not show a similar feature. The E′ values between the glass transitions of PLA and PHBV depended on the blend compositions and morphologies. The presence of titania nanoparticles had little effect on the E′ values of all the investigated blends. The cold crystallization transition of PLA shifted to lower temperatures in the PLA/PHBV blends, and shifts in the Tgs of the two polymers indicated partial miscibility at the polymer-polymer interfaces. This partial miscibility reduced the chain mobilities of these polymers, which could be seen in a reduction in the damping during their respective glass transitions. Blending and nanoparticle addition had little influence on the glass transition temperatures of PLA and PCL in the PLA/PCL blends, but the glass transitions of PHBV and PCL in the PHBV/PCL blends were respectively at higher and lower temperatures than those of the neat polymers, which is a somewhat abnormal observation. The PCL glass transition peaks became broader as a result of blending, which was attributed to the incompatibility of the polymers in the blends, because blending had no influence on the PCL crystallinity.
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