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Extrusion foaming of linear and branched polypropylenes – input of the thermomechanical analysis of pressure drop in the die

  • Carlos Sandino ORCID logo , Edith Peuvrel-Disdier EMAIL logo , Jean-François Agassant , Patrice Laure ORCID logo , Séverine A. E. Boyer ORCID logo , Geoffrey Hibert and Yves Trolez
Published/Copyright: July 14, 2022
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International Polymer Processing
From the journal International Polymer Processing Volume 37 Issue 4

Abstract

This paper aims at a better understanding of the polypropylene (PP) physical extrusion foaming process with the objective of obtaining the lowest possible foam density. Two branched PPs were compared to the corresponding linear ones. Their shear and elongation viscosities were measured as well as their crystalline properties. Trials were conducted in a single screw extruder equipped with a gear pump and a static mixer cooler to adjust the melt temperature at the final die. The effect of decreasing this temperature on the PP foamability and on the pressure drop in the die was analyzed. The foam density of branched PPs varies from high to low values while decreasing the foaming temperature. In the same processing conditions, the foam density of linear PPs does not decrease so much, as already evidenced in the literature. The foamability transition coincides with an increase of the pressure drop in the die. The originality of the work lies in the thermomechanical analysis of the polymer flow in the die which allows the identification of the relevant physical phenomena for a good foamability. The comparison of the experimental pressure drops in the die and the computed ones with the identified purely viscous behavior points out the influence of the foaming temperature and of the PP structure. At high foaming temperature the discrepancy between experimental measurements and the computed pressure drops remains limited. It increases when decreasing the foaming temperature, but the mismatch is much more important for branched PPs than for linear ones. This difference is analyzed as a combination of the activation energy of the viscosity, the elongational viscosity in the convergent geometry of the die which is much more important for branched PPs than for linear ones, and the onset of crystallization which occurs at higher temperature for branched PPs than for linear PPs.

Keywords: chain architecture; extrusion foaming; polypropylene; thermomechanical analysis
Corresponding author: Edith Peuvrel-Disdier, Mines Paris, PSL University, Centre de mise en forme des matériaux (CEMEF), CNRS UMR 7635, CS 10207, 06904 Sophia Antipolis cedex, France, E-mail:

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: None declared.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

Appendix

Differential scanning calorimetry crystallization curves for the different polypropylene grades are depicted in Figure A.

Figure A: Crystallization curves for branched grades (A), for linear grades (B).
Figure A:

Crystallization curves for branched grades (A), for linear grades (B).

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Received: 2022-03-10
Accepted: 2022-05-22
Published Online: 2022-07-14
Published in Print: 2022-09-27

© 2022 Walter de Gruyter GmbH, Berlin/Boston

Articles in the same Issue

  1. Frontmatter
  2. Editorial
  3. Special issue for John Vlachopoulos
  4. Review Article
  5. Calendering of thermoplastics: models and computations
  6. Special Issue Contributions
  7. Film casting of polycarbonate/multi-walled carbon nanotubes composites using ultrasound-assisted twin-screw extruder: experiment and simulation
  8. Effect of mixing conditions and polymer particle size on the properties of polypropylene/graphite nanoplatelets micromoldings
  9. Extrusion foaming of linear and branched polypropylenes – input of the thermomechanical analysis of pressure drop in the die
  10. Improving the thickness distribution of parts with hybrid thermoforming
  11. Synergistic material extrusion 3D-printing using core–shell filaments containing polycarbonate-based material with different glass transition temperatures and viscosities
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  14. Factors determining the flow erosion/part deformation of film insert molded thermoplastic products
  15. The extrusion of EPDM using an external gear pump: experiments and simulations
  16. News
  17. PPS News
https://doi.org/10.1515/ipp-2022-0025
Keywords for this article
chain architecture; extrusion foaming; polypropylene; thermomechanical analysis

Articles in the same Issue

  1. Frontmatter
  2. Editorial
  3. Special issue for John Vlachopoulos
  4. Review Article
  5. Calendering of thermoplastics: models and computations
  6. Special Issue Contributions
  7. Film casting of polycarbonate/multi-walled carbon nanotubes composites using ultrasound-assisted twin-screw extruder: experiment and simulation
  8. Effect of mixing conditions and polymer particle size on the properties of polypropylene/graphite nanoplatelets micromoldings
  9. Extrusion foaming of linear and branched polypropylenes – input of the thermomechanical analysis of pressure drop in the die
  10. Improving the thickness distribution of parts with hybrid thermoforming
  11. Synergistic material extrusion 3D-printing using core–shell filaments containing polycarbonate-based material with different glass transition temperatures and viscosities
  12. TPU-based porous heterostructures by combined techniques
  13. Surfactant-free oil-in-oil emulsion-templating of polyimide aerogel foams
  14. Factors determining the flow erosion/part deformation of film insert molded thermoplastic products
  15. The extrusion of EPDM using an external gear pump: experiments and simulations
  16. News
  17. PPS News
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