Adhesion at Al-hydroxide-polymer interfaces: Influence of chemistry and evidence for microscopic self-pinning

Abstract

We present a combined chemical (auger electron spectroscopy) and microscopic (optical microscopy, scanning electron microscopy and scanning probe microscopy) study of the work of adhesion and delamination mechanisms at interfaces between a glassy polymer (glycol-modified polyethylene terephthalate) and Al covered with different types of surface hydroxides. A clear correlation between the measured work of adhesion and the chemical nature of the Al surface, specifically the hydroxyl coverage and the iso-electric point is found. The magnitude of the work of adhesion points to important contributions from plastic deformation in the glassy polymer for some cases. Delamination is shown to be accompanied by the formation of microscopic shear bands at such interfaces. The non-monotonous stress-strain behaviour of the glassy polymer that gives rise to the shear bands is also shown to lead to peculiar pinning events at the crack front. Evidence indicates that the occurrence of protrusions in the crack front deriving for example from the presence of stress concentrators and crack initiation sites ahead of the front, combined with mode and rate dependence of the local energy release rate along the front may pin the front at positions adjacent to a protrusion. It is believed such microscopic mode-dependent pinning phenomena may be relevant for the adhesion on patterned interfaces.

Direct joining of carbon-fiber–reinforced plastic to an aluminum alloy using friction lap joining

“…3, surface grinding of the A5052 increased the strength of the A5052/CFRTP FLJ joints. The presence of the surface oxides Al 2 O 3 and MgO and the hydroxide Al(OH) 3 affect the joining of the A5052 and the polyamide 6 in the CFRTP, which is the result of hydrogen bonding between NH and CH groups in polyamide 6 and -O or -OH groups in the oxide and hydroxide compounds [17,[32][33][34], respectively, on the A5052 surface. The hydroxide groups strongly contribute to the wetting of the A5052 surface by the molten polyamide 6 [17,32].…”

Accelerated growth of oxide film on aluminium alloys under steam: Part II: Effects of alloy chemistry and steam vapour pressure on corrosion and adhesion performance

“…The adhesion provided by the mechanical interlocking is one aspect which depends on the surface morphology of the conversion coating [21,22]. The adhesion mechanism also depends on the acid/base properties of the surface due to the possibility of forming chemical bonds with the top layer [23]. The organic molecules in the top layer will form chemical bonds with the conversion layer depending on the surface property.…”

Friction Lap Joining of Thermoplastic Materials to Carbon Steel

“…Various joining mechanisms such as chemical bonding (covalent bonding, hydrogen bonding), Van der Waals force, and the anchor effect have been reported to provide the bonding force for these materials. 9,26,27) The hydrogen bonding between the metal oxide (or hydroxide) layer on a metal surface and (1) a polar group, such as the hydroxyl (-OH) or carboxyl (-COOH) group, in corona-dischargetreated PE, and (2) the amide group (CONH) in PA6, has often been attributed with providing an effective joining force for direct joining of these materials. 9,[21][22][23][24]26) The polar group in plastic materials consists of some atoms that have different electronegativities.…”