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| Naji, M. |
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| Motta, Antonella |
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| Aletan, Dirar |
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| Mohamed, Tarek |
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| Ertürk, Emre |
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| Taccardi, Nicola |
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| Kononenko, Denys |
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| Petrov, R. H. | Madrid |
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| Alshaaer, Mazen | Brussels |
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| Bih, L. |
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| Casati, R. |
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| Muller, Hermance |
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| Kočí, Jan | Prague |
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| Šuljagić, Marija |
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| Kalteremidou, Kalliopi-Artemi | Brussels |
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| Azam, Siraj |
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| Ospanova, Alyiya |
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| Blanpain, Bart |
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| Ali, M. A. |
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| Popa, V. |
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| Rančić, M. |
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| Ollier, Nadège |
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| Azevedo, Nuno Monteiro |
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| Landes, Michael |
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| Rignanese, Gian-Marco |
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Sandino, Carlos
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Publications (5/5 displayed)
- 2022Extrusion foaming of linear and branched polypropylenes – input of the thermomechanical analysis of pressure drop in the die
- 2022Foamability of linear and branched polypropylenes by physical extrusion foaming - Input of the thermomechanical analysis of pressure drop in the die
- 2022Extrusion foaming of linear and branched polypropylenes - Input of the thermomechanical analysis of pressure drop in the die
- 2022Analysis and Modelling of Extrusion Foaming Behaviour of Polyolefins using Isobutane and CO2
- 2021Analysis and Modelling of Extrusion Foaming Behaviour of Low-Density Polyethylene using Isobutane and CO2
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conferencepaper
Foamability of linear and branched polypropylenes by physical extrusion foaming - Input of the thermomechanical analysis of pressure drop in the die
Abstract
This study aims to better understand the polypropylene (PP) foamability by physical extrusion foaming comparing branched chains with strain hardening versus linear ones. Trials were conducted in a single screw extrusion equipped with a gear pump for the gas dissolution step (same extrusion parameters, 1wt% CO2) and a static mixer cooler allowing to decrease the melt temperature before the final die (referred as foaming temperature). The effect of decreasing the foaming temperature on the PP foamability was analyzed.The foam density of branched PP varies from high to low values while decreasing the foaming temperature. This foamability transition coincides with an increase of the pressure drop in the die. As reported, branched PPs depict a better foamability than linear grades. As the pressure drop in the die is responsible of the polymer foaming, a thermomechanical analysis of the polymer flow was conducted to better understand the foamability transition.The pressure drop was calculated in the die using dedicated analytical expressions for the converging and capillary parts and a power law for the viscosity curve. Calculated pressures are lower than the measured values. The discrepancy is interpreted as an additional contribution due to the elongational flow in the converging channel, which can be estimated. The pressure drop variation with the foaming temperature follows an Arrhenius dependence in the case of linear grades. In the case of branched grades, the Arrhenius dependence is valid for large foaming temperatures but a large discrepancy is reported for low foaming temperatures. Two phenomena (presence of strain hardening for branched PP and/or of crystallization) can be at the origin of this discrepancy. These hypotheses will be examined and discussed for the different polymer grades in order to clarify the physical scenario for the foaming process.