Characterization of the primary and secondary crystallization kinetics of a linear low-density polyethylene in quiescent- and flow-conditions

Abstract

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Application of a multi-phase multi-morphology crystallization model to isotactic polypropylenes with different molecular weight distributions

“…Experiments were performed in the Pirouette extended dilatometer (IME Technologies), which has been employed in several works performed in our group during the last years (see References [34,35,28,30]). This apparatus is able to monitor the specific volume of a material in a broad range of temperature (T = 25-300°C) and pressure (p = 1-1200 bar) and it possesses the exceptional ability to apply shear flow in a Couette cell (γ̇= 1-180 s ) to the molten polymer.…”

“…The pioneering work in understanding and modelling flow-induced crystallization started by the Janeschitz-Kriegl group [24] was developed and implemented during the last twenty years in our group [25][26][27][28]19,29,30]: the temperature and pressure dependence of growth of different crystal phases and of the overall nucleation density was determined using an optimization routine to fit experimental data and described by phenomenological equations, the effect of flow on the increase in the number of nuclei and on oriented structures formation was evaluated by considering the momentary stretch of the high molecular weight tail of the material, using different approaches over the past years. The structure development in non-isothermal conditions after flow at different pressures was computed using a modified set of Schneider rate equations [31] combined with Kolmogorov-Avrami equation [32] to account for impingment.…”

The prediction of mechanical performance of isotactic polypropylene on the basis of processing conditions

“…Quasi-isothermal crystallization experiments were performed with a custom modified JHT-350 Linkam stage equipped with a pneumatically actuated temperature jump-stage [33]. The cold stage was set at temperatures of 100, 110 and 120 C respectively.…”

Modeling Flow-Induced Crystallization

“…Because flow-induced point-like nucleation has been extensively described in the literature, we focus here on FIC under strong flow conditions, yielding highly oriented crystal structures. We focus on experimental data obtained for iPP, but similar modeling has been successfully used to predict FIC kinetics for linear low density polyethylene (LLDPE) and poly(1-butene) [29,81] and is now being applied to poly(lactic acid).…”