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. POLYM. ENG. SCI. 46:659–669, 2006.