Strain and strain-rate formulation for flow-induced crystallization

It has been suggested that isothermal flow-induced crystallization is jointly linked to strain and strain rate. Here we test this idea further by studying some results of Bove and Nobile on isotactic poly (1-butene). We also present some new experimental results on polypropylene in finite amplitude sinusoidal oscillation. The ranges of strain amplitude and frequency are from 0.1 % to 10% and from 0.1 to 30 Hz, respectively. The experimental data are compared with the results calculated by using a multimode PTT model with a suspension-based theory; both strain and strain rate are involved in the flow-induced crystallization. A fairly good agreement between experiments and calculations has been observed. We conclude that a simple strain plus strain-rate function gives a reasonable description of flow-induced crystallization at low shear rates.