In polymer processing, the molecular orientation induced by flow has a significant effect on the crystallization kinetics and final morphology of the polymer produced. The impact on processing operations and object properties is extremely important and recently scientific and technological researchers have begun to quanitify these effects. The international conference 'Flow-Induced Crystallization of Polymers', held in October 2001 in Salerno, Italy, was timely and well attended. An interdisciplinary approach was taken and presentations were made on topics ranging from real-time measurement, through modelling, to final morphology and properties of polymers. Invited and other selected contributions from the conference are collected here, in this volume of Macromolecular Symposia

Structure formation in crystallizing polymers, as occurring during processing, has not been treated so far in a coherent form. This fact explains, why this monograph is written as the ?rst book devoted to this subject. A quarter of a century ago the underdevelopment of this subject was obvious. Trial and error dominated. In fact, other apposite subjects as polymer melt rheology or heat transfer, had reached high levels. A great number of books has been devoted to them. Mold ?lling of amorphous polymers and the solidi?cation of these polymers by vitri?cation can nowadays be simulated numerically with a high degree of accuracy. In the solidi?ed sample even residual stresses and corresponding birefringence effects can accurately be 1 calculated . However, semicrystalline polymers, which form the majority of industrial po- mers, have been excluded from these considerations for good reasons. In fact, great uncertainties existed about the formation of quality determining crystalline str- tures. In particular, polyole?ns suffered from this shortcoming. In 1983 this fact instigated the polymer research group at the Johannes Kepler University in Linz to start with pertinent activities. The urgency of this kind of studies becomes evident, if advantages and hitches of these polymers are considered. 1. Versatility of processing: Injection molding into a great variety of shapes and sizes, from thin walled beakers to garden chairs, not to forget pipe and pro?le extrusion, cable coating, ?ber spinning, ?lm blowing. 2. Product qualities: Ductility, low density, good electric insulation, corrosion resistance, surface quality.

The effects of shearing and elongational flows on flow induced crystallization in polymer melts were investigated for the two-phase system of high molecular weight polyethylene suspended in a linear low density polyethylene carrier phase. Shearing flow was produced by a counter-rotating couette device and elongational flow was produced by means of a four roller mill device. Deformation and bursting of droplets were observed in both of these flows, however, shearing flow was found unsuitable for quantitative studies, since the orientation of the optical axes in the carrier and suspended phases were not coaxial. Hot stage and dichroism studies indicated that crystallization occurs in the suspended phase in the four roller mill, at temperatures above which quiescent crystallization would occur. In-situ birefringence measurements were made and initial crystallization rates were determined and found to depend upon both stress and strain in the deforming droplet. This was very suggestive of a viscoelastic phenomenon, not simply, a nucleation and growth controlled mechanism, thus the separability, of flow effects and nucleation and growth crystallization, is brought into question by this complex behavior. A first order approximation based on molecular rheology has been used to gain qualitative and quantitative insights on the observed trends.