Highlighting chemical bonding between nylon-6.6 and the native oxide from an aluminum sheet assembled by laser welding

in ACS Applied Polymer Materials (2020)

Polymer/metal hybrid assemblies are well suited for automotive and biomedical applications because of their ability to create lightweight structures with a wide range of design possibilities. Laser ... [more ▼]

Polymer/metal hybrid assemblies are well suited for automotive and biomedical applications because of their ability to create lightweight structures with a wide range of design possibilities. Laser welding is a promising technique for joining dissimilar materials thanks to its quickness, freedom of design and absence of adhesives. Still, the fundamental causes of adhesion in hybrid laser welding remain not well understood. Therefore the present work aims at highlighting a chemical bonding between a polymer, nylon-6.6 and a metal, aluminum. To access the interface information, the samples were first broken, leaving a residue on the surface, which was dissolved afterwards. The chemical reactive sites of nylon molecule able to react with aluminum surface were suggested and the feasibility of these reactions was analyzed in the light of the results obtained by means of X-ray photoelectron spectroscopy (XPS) and Time of flight secondary electron microscopy (ToF-SIMS). [less ▲]

Influence of Aluminum Laser Ablation on Interfacial Thermal Transfer and Joint Quality of Laser Welded Aluminum–Polyamide Assemblies

in Coatings (2019), 9(11),

Laser assisted metal–polymer joining (LAMP) is a novel assembly process for the development of hybrid lightweight products with customized properties. It was already demonstrated that laser ablation of ... [more ▼]

Laser assisted metal–polymer joining (LAMP) is a novel assembly process for the development of hybrid lightweight products with customized properties. It was already demonstrated that laser ablation of aluminum alloy Al1050 (Al) prior to joining with polyamide 6.6 (PA) has significant influence on the joint quality, manifested in the joint area. However, profound understanding of the factors affecting the joint quality was missing. This work investigates the effects of laser ablation on the surface properties of Al, discusses their corresponding impact on the interfacial thermal transfer between the joining partners, and evaluates their effects on the joint quality. Samples ablated with different parameters, resulting in a range from low- to high-quality joints, were selected, and their surface properties were analyzed by using 2D profilometry, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). In order to analyze the effects of laser ablation parameters on the interfacial thermal transfer between metal and polymer, a model two-layered system was analyzed, using laser flash analysis (LFA), and the thermal contact resistance (TCR) was quantified. Results indicate a strong influence of laser-ablation parameters on the surface structural and morphological properties, influencing the thermal transfer during the laser welding process, thus affecting the joint quality and its resistance to shear load. [less ▲]

Aluminum pretreatment by a laser ablation process: influence of processing parameters on the joint strength of laser welded aluminum – polyamide assemblies

in Procedia CIRP (2018)

Laser welding of metal – polymer assemblies is an innovative bonding process. It was already demonstrated that laser surface pretreatments of aluminum (Al), prior to laser welding with a polymer, impacts ... [more ▼]

Laser welding of metal – polymer assemblies is an innovative bonding process. It was already demonstrated that laser surface pretreatments of aluminum (Al), prior to laser welding with a polymer, impacts joints strength. This work adopts a design of experiments (DoE) approach to investigate the influence of several Al laser ablation parameters on joint strength of laser welded Al – polyamide (PA6.6) assemblies. Significant parameters were highlighted, process window was outlined, and optimal parameters were identified. After assembly failure, the joint area was evaluated using optical microscopy. Depending on the laser ablation parameters, the joint area can be enhanced resulting in a significant increase in the corresponding bearable shear load. [less ▲]

Chemical Bonds in Laser Welded Aluminum and Polyamide

Presentation (2017, September 14)

Automotive industry is showing an increasing interest towards polymer/metal assemblies, essentially in order to increase fuel efficiency through the reduction of car body weight. In parallel, these ... [more ▼]

Automotive industry is showing an increasing interest towards polymer/metal assemblies, essentially in order to increase fuel efficiency through the reduction of car body weight. In parallel, these assemblies are interesting for biomedical applications, because of the potential to obtain improved or new properties e.g. for implants. Laser welding is considered one of the most promising methods of joining dissimilar materials because of its unique advantages; the process is fast, can be adapted to complex geometries and is totally solvent free, which is a major asset for biomedical applications [1]. A strong adhesion between polyamide 6.6 (PA-6.6) and aluminum (Al) plates was obtained from laser welding in optimized conditions [2]. However, the root causes of this adhesion are not yet understood. Several effects may come into play, such as covalent binding, electrostatic binding, interdiffusion and mechanical interlocking. This is further complicated in “real life” samples by the high roughness of the metal sheet, the additives contained in the polymer, the Al and PA-6.6 surface composition and the difficulty to reach the metal-polymer interface. In order to gain information on the chemical binding between the oxydized Al surface and the PA-6.6, model samples were prepared by spin coating ultrathin PA-6.6 films on polished Al (99.999 % purity) plates (Fig. 1.). The two materials were subsequently welded by laser irradiation. FT-IR, XPS and ToF-SIMS have been used to carry out this study. The interface was reached by sputtering the polymer with low energy Cs+ ions in ToF-SIMS and Ar clusters GCIB in XPS. In this preliminary study, ions binding the Al with polymer were identified in both the positive (AlCH3O+, AlNH+, AlNH2 +, Al2NH+) AlCNO+, AlONH3 +) and negative polarities, (AlN-, AlNO-, AlCO-, AlCNO-). Depth profiles and images near the interface were obtained. Results obtained on our model samples will be compared with laser joints obtained on “real” samples. Ultimately, this work aims at providing guidelines for improving the mechanical resistance of the weld. [less ▲]