Determination of molecular weight distribution by melt rheology – a revision of Tuminello's model on isotactic polypropylene

Kaspar H, Strübbe N, Muscat D, Kaschta J (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Polymer Testing Elsevier

Book Volume: 155

Article Number: 109103

DOI: 10.1016/j.polymertesting.2026.109103

Abstract

The present work is creating an extended remake of a long-existing modulus model for extracting information about molecular weight distribution (MWD) from the melt rheology data of polymers. All key variables are redefined for isotactic polypropylene, iPP. Measurements of high-temperature size exclusion chromatography coupled with multi-angle laser light scattering, HT-SEC-MALLS, of three technical iPP grades differing in terms of their average molecular weight and the width of their distribution both, are projected onto their dynamic mechanical data recorded at T = 190 °C. For both scaling laws, η0 ∼ M w ^α and 1/ω ∼ M ^{α +1}, it clearly shows that the exponent α is passing a turnover from 3.6 to 3.0 as soon as the reptation molecular weight of M r = 4.9 × 10⁵ g/mol is exceeded. The latter quantity is related to the plateau modulus, which is reevaluated from literature data to yield G N ⁰ = 5.7 × 10⁵ Pa. With these two different exponents being employed to interpret the relaxation behavior of iPP melts, their overall cumulative molecular weight distribution, CMWD , can be derived correctly. Missing information at the low molar weight flank need to be filled up by using appropriate approximation functions. Additionally to the tanh-function being already in place, another useful model based on the distribution of a Schulz-Zimm type is introduced. Errors in data approximation can be effectively ruled out by the zero-shear viscosity η0 as an independent consistency criterion. The new model edition hides potentially existing short-chain branches, SCBs, and the quality of the obtained MWD s can compete with those ones from HT-SEC.

Authors with CRIS profile

Joachim Kaschta Lehrstuhl für Werkstoffwissenschaften (Polymerwerkstoffe) (LSP)

Involved external institutions

Technische Hochschule Rosenheim

Germany (DE)

How to cite

APA:

Kaspar, H., Strübbe, N., Muscat, D., & Kaschta, J. (2026). Determination of molecular weight distribution by melt rheology – a revision of Tuminello's model on isotactic polypropylene. Polymer Testing, 155. https://doi.org/10.1016/j.polymertesting.2026.109103

MLA:

Kaspar, Harald, et al. "Determination of molecular weight distribution by melt rheology – a revision of Tuminello's model on isotactic polypropylene." Polymer Testing 155 (2026).

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