The DSC cooling and second heating thermograms of virgin PLAs and nanocomposites are illustrated in Figure . Figure shows the cooling curves of pure HPLA and its nanocomposites without any crystallization occurring in either material. While the introduction of nanomaterials could not promote crystallization, due to the large molecular weight and high D-lactide content (4.25 mol%) of HPLA, it is reasonable to expect that HPLA will not crystallize when rapidly cooled (10°C/min). Figure depicts the second heating curves of the same materials. While HPLA showed a very weak cold crystallization peak around 120°C, with the introduction of GNP and NC, the cold crystallization peaks started at earlier temperatures around 100 and 110°C, respectively. This demonstrates the nanomaterial's nucleation effect on HPLA crystallization. However, in the case of HPLA/NC samples, cold crystallization started earlier compared to HPLA/GNP samples. According to the steady-state viscosity analysis, HPLA/GNP samples have a much lower viscosity, resulting in higher mobility. However, rheological time sweep analysis revealed higher thermal degradation in HPLA/NC samples, and a similar situation could occur during DSC. As a result of thermal degradation and lower chain length, HPLA/NC could have earlier cold crystallization due to higher chain mobility. points. This effect was much stronger in the LPLA/GNP samples. While the crystallisation percent of the LPLA/NC ones ranged from 4% to 6%, this range increased to 9% to 31% for the LPLA/GNP ones. This could be due to the higher mobility of the LPLA/GNP samples, which facilitated easier chain alignment and crystallization. Figure shows the second heating curves of the same materials. Neat LPLA showed a cold crystallization starting around 90°C. The addition of NC initiated cold crystallization around 80°C, and this temperature increased with the NC content. This is in line with the finding that the material had higher viscosity thus less mobility in the steady-state rheological analysis with increased NC content. The cold crystallisation of the LPLA/GNP samples started around 80°C and cold crystallization peak got smaller with 3wt.% of GNP. The steady-state viscosity analysis showed that the LPLA/GNP samples have higher mobility, which causes that the mostly of the crystallization was carried out during cooling. When the LPLA and HPLA nanocomposites are compared, the heterogeneous nucleation effect of nanomaterials is more significant in the case of LPLA due to its lower molecular weight and D-lactide content, while the LPLA/GNP samples have the highest crystallinity.