In the present work, the importance of crystallization
kinetics modeling in polymer transformation processes
has been addressed. Despite the large amount of work done
in this field, a model able to describe the kinetics of a semicrystalline
polymer under a wide range of cooling rate still
lacks. Here, the research done on the crystallization kinetics
of a commercial iPP has been summarized, and the reconsideration
of the entire set of experimental evidences has
allowed proposing and tuning a complete model. The proposed
model has been proved able to reproduce all the
experimentally observed features (semi-crystallization
time during isothermal tests and semi-crystallization
temperatures during DSC ramps and fast quenches,
secondary crystallization, crystallinity evolutions during
quenches, final phase distributions, final spherulite
diameters).
The model has been built to be easily improved in the
future. One of these improvements will be the correct localization
of the mesomorphic phase development, as soon as related
kinetics experimental data will be available. Another
task will be to model the effect of pressure (for example
allowing shift of glass transition temperature, Tg, and of
melting point temperature, Tm, as effect of pressure). The
flow is known to have an enhancement effect on crystallization
kinetics, and to model this effect is a key issue in
crystallization studies (Flow-Induced Crystallization, FIC).
As long as the flow level is insufficient to produce a change
in morphology (if a properly defined Deborah number is
low enough, the flow will only accelerate the spherulite
development [76], whereas higher flow levels cause drastic
changes in morphology), the model proposed in this paper
to describe the quiescent crystallization kinetics is still
able to describe flow-induced crystallization, by providing
a properly shifted melting point temperature, Tm (the increase
in melting point due to the flow, which has an
entropic origin [40,42]). The theoretical basis to account
for FIC effects due to crystallites of different morphologies
are, anyway, already present in the propose treatise