Giuseppe Titomanlio

Crystallization kinetics and solidified structure in iPP under high cooling rates

Abstract A wide set of isothermal and non-isothermal crystallization experiments were carried out in this work on an iPP resin. Several experimental techniques were adopted in order to characterize crystallization kinetics and final morphology of the material, also under cooling rates comparable to those encountered during material processing (up to several hundred K/s). The whole set of data was taken as a reference to identify a kinetic model which describes the evolution of the structural organization of iPP (α crystalline phase and mesomorphic phase) as a parallel of two non-interacting kinetic processes competing for the available amorphous volume. Kolmogoroff equation was adopted to describe the crystallization of the α form. Avrami–Evans–Nakamura isokinetic approach was adopted to describe the evolution of the mesomorphic phase. Resulting kinetic model satisfactorily describes the whole set of experimental data including those obtained on samples solidified under high cooling rates, and reveals that a correct description of the evolution of the α phase during solidification can be attained only if the evolution of the competing mesomorphic phase is kept into account. The effect of cooling rate during solidification from the melt on diameters of spherulites, observed on solidified samples, is also satisfactorily described by model predictions.

On the Simulation of Thermoplastic Injection Moulding Process: II Relevance of Interaction Between Flow and Crystallization

Abstract The relevance of enhancement of crystallisation kinetics by effect of shear flow and rheology during polymer solidification to the phenomena taking place during the injection moulding process has been shown by means of simulations performed on the basis of Lord and Williams [1, 2] model and its recent extensions [3 to 5]. A key point of the simulation was the solidification criterion based on a critical crystallization index; on the basis of simple calorimetric and rheological tests in the limit of zero shear rate, values of a few percent were given to the solidification crystallinity value. Many experimental features of pressure history both in the runner and in the cavity are recovered by model predictions, if both effects mentioned above are properly accounted for. However, predictions for gate sealing time, although improved, still have a sensitivity to gate thickness lower than that shown by the experiments. Similar conclusions, obviously, regard also the mass entering in the mould during holding. Another mechanism which sums up to shear stresses to accelerate thin gate solidification has still to be identified.

Measurement and modelling of the film casting process 1. Width distribution along draw direction

In the cast

Measurement and modelling of the film casting process: 2. Temperature distribution along draw direction

lm process a polymer melt is extruded through a slit die, stretched in air and cooled on a chill roll. During the path in air, while the melt cools, a reduction of both thickness and width takes place; obviously, thickness and width reductions are functions of draw ratio and stretching distance. Width distribution along the draw direction was measured on a iPP resin supplied by Montell as function of both 8ow rate and take up velocity. Final

Crystallinity and Linear Rheological Properties of Polymers

lm width was found to decrease as take up velocity increase and, surprisingly, as extrusion 8ow rate increases. Thus draw ratio increase, attained by either lowering extrusion 8ow rate or by rising take up velocity, can lead to either enlargement or reduction of

Molecular orientation and strain in injection moulding of thermoplastics

nal

On the Behavior of HPMC/Theophylline Matrices for Controlled Drug Delivery

lm width. The process of stretching in air was modelled with coupled one-dimensional equations of continuity and motion based on work of Barq, Haudin, Agassant, and Bourgin (Int. Poly. Process. 9 (1994) 350) the crystallinity generation term, according to the Nakamura non-isothermal model, was included in the equation of energy lumped along the thickness direction. The polymer was considered as a viscous 8uid (non-Newtonian), the apparent viscosity being function of temperature and strain rate. Furthermore, the e?ect of crystallinity on viscosity was somehow accounted for. The model equations were solved numerically. A modi

A general code to predict the drug release kinetics from different shaped matrices.

ed expression of heat transfer coe@cient with respect to the model of Barq et al. (1994) was applied leading to a better agreement between model predictions and data with reference to width distribution along the draw direction and

Relevance of Crystallisation Kinetics in the Simulation of the Injection Molding Process

nal

On the Simulation of Thermoplastic Injection Moulding Process

lm thickness. ? 2001 Elsevier Science Ltd. All rights reserved.