Determination of the local three-phase morphology in laser transmission weld seams of isotactic polypropylene by Raman microscopic line-focus mapping

Bräuer P, Bahr L, Mayer E, Marschall M, Schmidt M, Will S (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Book Volume: 156

Article Number: 109126

DOI: 10.1016/j.polymertesting.2026.109126

Abstract

The absorption of laser energy during laser transmission welding (LTW) of certain thermoplastics such as isotactic polypropylene (iPP) affects their three-phase morphology (TPM) – comprised of crystalline (CF), mobile amorphous (MAF) and rigid-amorphous phase fractions (RAF) – and thus their mechanical properties, which are relevant for their production, processing and application. Therefore, this study serves to establish a spatially resolved and quantitative diagnostic to generate deeper insights into the cause-and-effect relationships between LTW parameters and the resulting TPM in iPP. Raman spectroscopy is developed as a quantitative TPM measurement technique in iPP. To that end, in situ Raman measurements are performed during the melting and crystallization of iPP. A spectral reconstruction routine is applied to the spectra to create a setup-independent Raman peak model. Furthermore, an improved Raman TPM model is established via model selection leveraging the Bayesian Information Criterion. The developed models are then applied to determine the effect of different LTW line energies on the local TPM in iPP welds using spatially resolved Raman microscopic line-focus mapping. Compared to the laser-unaffected iPP, the weld core shows a decrease in the CF, but an increase in the RAF and MAF contributions. For high line energies this effect is less pronounced as the system is given more time for crystallization after melting. In effect, higher line energies are advantageous to achieve a similar TPM in both the weld core and adjacent non-irradiated iPP.

Authors with CRIS profile

Involved external institutions

Bayerisches Laserzentrum gemeinnützige Forschungsgesellschaft mbH (BLZ) Germany (DE)

How to cite

APA:

Bräuer, P., Bahr, L., Mayer, E., Marschall, M., Schmidt, M., & Will, S. (2026). Determination of the local three-phase morphology in laser transmission weld seams of isotactic polypropylene by Raman microscopic line-focus mapping. Polymer Testing, 156. https://doi.org/10.1016/j.polymertesting.2026.109126

MLA:

Bräuer, Phillipp, et al. "Determination of the local three-phase morphology in laser transmission weld seams of isotactic polypropylene by Raman microscopic line-focus mapping." Polymer Testing 156 (2026).

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