Fundamental study of the adhesion phenomena in polymer-metal hybrid materials obtained by laser welding

Abstract

On one hand, to lower the impact of the transport industry on the greenhouse gas emissions, hence their environmental impact, it is urgent to create lightweight structures. On the other hand, the biomedical industry is striving for more biocompatible and more functionalized implants. The two problems lead to the same solution: hybrid polymer-metal assemblies. The question now is to assemble such extremely different materials. Amongst all the technique available –mechanical fastening, adhesive bonding, and welding- one technique is catching more and more attention: laser welding. This technology presents many advantages, such as fast processing, easy automation, high design freedom and no need for intermediate materials. Nonetheless, the root causes of adhesion are still not well understood. The adhesion theory proposes four phenomena to explain it: mechanical interlocking, chemical bonding, diffusion and electrostatic interaction. In this thesis the chemical bonding at the interface was thoroughly investigated for two materials combinations of interest for the industry: aluminum/polyamide-6.6 and titanium/polyamide-6.6. For the two combinations three types of samples were prepared: welded samples, spin-coated samples and model samples. The welded samples consist in near industrial samples with thick metal and polymer sheets welded together. To analyze those samples, a new methodology was developed combining breaking the samples and dissolving the polymer residue to access the interface for XPS and ToF-SIMS analysis. The spin-coated samples consist simply in a spin-coated layer of polymer on mirror polished metal. The model samples consist in the deposition of a molecule presenting only the reactive part of the polymer structure, N-methylformamide. The combination of the XPS and ToF-SIMS results of the three samples allowed to determine the existence, the nature of the bond, a C-O-M bond (M=Al or Ti), and the reaction mechanism. The proof of concept of diffusion in the case of laser welding on the combination aluminum/polyamide-6.6 is also done at the end.

Date of Award	5 Feb 2021
Original language	English
Awarding Institution	University of Namur
Sponsors	M-era.net
Supervisor	Laurent Houssiau (Supervisor), Robert Sporken (President), Peter Plapper (Jury), Terryn Herman (Jury), Didier Léonard (Jury) & Celine NOEL (Jury)