Quiescent and shear flow-induced crystallization of isotactic polypropylene

Autori: L. Bove, E. Somma, G. Titomanlio, M.R. Nobile
Presentato al: Southern Europe Conference on Rheology
Anno: 1999
Volume: 2
Issue: Unico
Casa Editrice: SIR-Cuen Napoli
Lingua: English


Abstract
In most shaping processes of thermoplastic polymers the thermonechanical treatment, which the melt undergoes before solidification, influences the crystallization kinetics of polymers (1-2). It is possible to observe the effect of a shear flow on the crystallization monitoring the evolution of the storage modulus (G'). This rheological parameter, because of its great sensitivity to structural changes, undergoes an increase of orders of magnitude during the transition of the material from the melt to the solid state(3-4).
In this work the rheological properties of a standard iPP, during isothermal crystallization starting from a melt in quiescent conditions as well as after a shear flow at higher temperature have been studied. Temperatures were selected in order to achieve a crystallization kinetics accessible to observation.
Quiescent results have also been compared to calorimetric measurements (DSC) performed under similar thermal histories.


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