Solubilities and Fick diffusion coefficients in blowing-agent-loaded polypropylene melts

Schmidt P, Jander JH, Gupta S, Ratka M, Bonten C, Klein T, Fröba AP (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Book Volume: 359

Article Number: 130136

DOI: 10.1016/j.polymer.2026.130136

Abstract

For the accurate modeling of bubble growth in blowing-agent-loaded polymer melts during physical foaming processes, accurate blowing agent solubility and Fick diffusion coefficient D11 data at process-relevant conditions are required. In this context, this work reports on the characterization of blowing-agent-loaded polypropylene (PP) melts by the determination of the solute mass fraction wsolute and D11 at process-relevant temperatures T and pressures p. To develop comprehensive structure-property relationships, binary mixtures based on linear PP (linPP) or long-chain-branched PP (lcbPP) or ternary mixtures based on their blends with dissolved nitrogen (N2), carbon dioxide (CO2), or 1,1,1,2-tetrafluoroethane (R134a) are studied at T between (433 and 533) K and p corresponding to blowing agent mass fractions wN2 ≤ 2% and (wCO2 or wR134a) ≤ 8%. The isochoric-saturation method (ISM) is applied to determine wsolute and combined with axisymmetric drop shape analysis (ADSA) to measure the volume swelling Sw required for its evaluation. To determine D11 and the associated wsolute, dynamic light scattering (DLS) is applied and combined with polarization-difference Raman spectroscopy (PDRS), which is calibrated using wsolute data measured by the ISM. Here, the applicability of DLS for studying ternary polymer-based mixtures was demonstrated and it was shown that the accessed diffusion coefficients can be interpreted as quasi-binary diffusion coefficients characterizing diffusive mass transfer of the blowing agent in the molten polymer blend. For the studied systems, a wsolute-independent behavior of D11 was identified and it was demonstrated that wsolute and D11 are not significantly influenced by the characteristics of the different PP types.

Authors with CRIS profile

Involved external institutions

Universität Stuttgart Germany (DE)

How to cite

APA:

Schmidt, P., Jander, J.H., Gupta, S., Ratka, M., Bonten, C., Klein, T., & Fröba, A.P. (2026). Solubilities and Fick diffusion coefficients in blowing-agent-loaded polypropylene melts. Polymer, 359. https://doi.org/10.1016/j.polymer.2026.130136

MLA:

Schmidt, Patrick, et al. "Solubilities and Fick diffusion coefficients in blowing-agent-loaded polypropylene melts." Polymer 359 (2026).

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