Dynamic crystallization kinetics and morphology of carbonaceous nanofillers-reinforced poly (lactic acid) foams

Carbon black (CB), multi-walled carbon nanotubes (CNT), and graphene oxide (GO)-reinforced poly (lactic acid) (PLA) foams were prepared. Morphological studies indicated that incorporating nanoparticles into foamed PLA (F-PLA) changed the sphericity degree, diameter, and homogeneity of cells. Among all samples, foamed PLA containing 0.25 phr GO exhibited the highest void content (+46%) compared to foamed neat PLA, while its cell density diminished by 21%. In contrast, despite a lower improvement in void content (+18%), foamed PLA containing 0.25 phr CNT experienced a +3% enhancement in cell density compared to foamed neat PLA. Also, the nanoparticles were well dispersed in un-foamed PLA without any obvious aggregation. The crystallization kinetics of foams were studied using DSC. The results revealed that PLA foams reinforced with 0.25 phr CNT and GO had a significant effect on crystallization promotion. The crystallization kinetics of foamed samples were studied using different models such as Jeziorny, Avrami, Ozawa, Kissinger, and Doyle-Ozawa. The results demonstrated that adding nanofillers did not affect the crystallization mechanism of foamed PLA. Also, incorporating up to 0.5 phr CNT and GO decreased the apparent crystallization activation energy compared to neat F-PLA. An almost similar trend was observed for the local crystallization activation energy.