Crystallization behavior of zinc oxide/poly(lactic acid) nanocomposites

In this work, films of commercial PLA Ingeo 4043D with nano-zinc oxide particles (nano-ZnO) with average diameter around 100 nm and ZnO concentrations of 0.1, 0.25, 0.3 and 0.5 mass% were prepared by flat die extrusion. The addition of nano-ZnO had an objective to promote the crystallization of PLA, but it decreased the thermal stability of the films. Both neat PLA and PLA/nano-ZnO composites films did not crystallize during the cooling, but crystallize during a first heating, showing a cold crystallization process, which was significantly influenced by the heating rate. A low chain mobility was evidenced by the values of relaxation time (T1H). This low chain mobility avoided the high degree of crystallization of the films which were predominantly amorphous. For all films, an enthalpic relaxation phenomenon was detected during the first heating. The glass transition temperature (T-g) was shifted to higher values as the heating rate and nanofiller content are increased. Addition of nano-ZnO in PLA films did not increase their crystallinity, indicating that it is not an effective nucleating agent for this low-crystallinity PLA grade.

Automated summary

By adding nano-zinc oxide particles to commercial PLA films, the intention was to enhance the crystallization process of PLA. However, it was found that the addition of nano-ZnO reduced the thermal stability of the films and did not significantly increase their crystallinity.