Shear induced crystallization in poly(ε-caprolactone): effect of shear rate

We have studied the effect of shear rate on the very early stages of poly(ε-caprolactone) crystallization with in situ rheology and ex situ optical microscopy. The effect of shear rate is mainly to increase the nucleation density and to speed-up the crystallization process. Thermally-induced crystallization is separated from strain-induced crystallization allowing the construction of a ‘master curve’ indicating that the system obeys the shear rate—temperature—superposition. It was found that the free enthalpy difference in the melt Gm(γ̇,T)−Gm(γ̇=0,T) increases with the shear rate (γ̇) that can be qualitatively rationalized by the reduced entropy of the melt prior to crystallization.