Crystallization of Poly(ϵ-caprolactone) composites with graphite nanoplatelets: Relations between nucleation and platelet thickness

•PCL crystallization is highly dependent on the layered structure of graphite.•Graphene shows the best nucleation activity of all used graphitic fillers.•Particles with various structures restrain chain movements at various levels.•Nucleation is dominant role for all graphitic particles during crystallization.•All graphitic fillers can promote overall kinetics of PCL crystallization.

Poly(ϵ-caprolactone) (PCL) composites containing graphite with various layered platelet structures were prepared by solution mixing for crystallization study. The results reveal that the crystallization of PCL is highly dependent on the graphite structure. All three kinds of graphite particles, including graphene nanosheets, graphite nanoplatelets and natural graphite flakes, show evident nucleating effect on the PCL crystallization. But their nucleation activity reduces with increased platelet thickness. However, the presence of graphite particles, especially graphite nanoplatelets and graphene nanosheets, also impedes the movements of PCL chain and increases the system viscosity, resulting in an evident increase of crystallization activation energy. But the nucleating effect is dominant role in the current system because all composites show higher crystallization rates than the neat PCL. The obtained results of this work can provide additional way to design or to control crystallization of PCL composites.