Synergistic effects of shear flow and nucleating agents on the crystallization mechanisms of Poly (Lactic Acid)

This paper presents a study of the effects of microscopic particles of talc on the crystallization kinetics of PLA. Our study covers the quiescent conditions and the case where a shear flow is applied “short term shearing”. The incorporation of talc increases the crystallization rate; it enhances the nucleation mechanism through additional heterogeneous nuclei. The microstructure is highly affected by the addition of talc due to the increase of the number of nuclei (i.e. reduced crystalline size). The application of a shear flow increases the ability of PLA to crystallize even in the presence of talc particles. The impact of shear rate becomes dramatically important just after a critical shear rate of 0.1 s⁻¹. It turns out that the shear rate enhances more the crystallization of PLA with talc than the pure PLA under quiescent conditions. Consequently, a supplementary contribution “synergistic effects” is responsible of the relative enhancement of the crystallization of PLA in the presence of shear flow and talc. With combining different experimental analysis techniques and modeling of the crystallization kinetics, the synergistically effects were quantified in terms of the nucleation density induced by the mutual interaction between shear flow and particles.