• Maidens, A. V.
• Olmsted, P. D.
• Ryan, A. J.
• Terrill, N. J.
• Fairclough, J. P. A.
• Bras, W.
• Dolbyna, I. P.
• Heeley, Ellen L.

Abstract

An experimental study of the early stages of crystallization in iPP has shown a qualitativedifference between the behavior at low supercooling with that observed with a deep quench. To addressprevious misgivings in the limits of resolution of crystallites by wide-angle scattering, a new detectorhas been used that has many orders of magnitude improvements in count rate. At low degrees ofundercooling there is a substantial gap between the appearance of a peak in the small-angle scattering,associated with electron density modulations, and the resolution of crystallites. This early growth inelectron density has been analyzed in terms of a spinodal decomposition process and the stability limitof isotactic polypropylene determined for three different samples of varying molecular weight. Theunderlying physics of the early stages of crystallization are discussed and a number of scenarios eliminated;at high temperature Avrami kinetics are not observed whereas at low temperatures the structure inboth the small-angle and wide-angle regimes grow contemporaneously following secondary nucleation.

Topics

• density
• impedance spectroscopy
• spinodal decomposition
• molecular weight
• crystallization