Page 154 - Handbook of Adhesion Promoters

8.6 Metal 147

8.6 METAL

No improvement in adhesion between brass-plated steel cords and rubber was observed
with loading of hexamethoxymethylmelamine in the range 1.3–5.2 phr but the adhesion
retention after humidity aging was observed with the same loading of hexamethoxymeth-
1
ylmelamine. A controlled formation of copper sulfide and zinc oxide in the interphase of
hexamethoxymethylmelamine-containing material improved the adhesion in humidity-
1
aging environments.
The galvanized steel/organic coating adhesion was improved by a duplex system
2
with a layer of glycidoxypropyltrimethoxysilane between the zinc and the coating. The
pretreatment increased the adhesion of the paint, especially when the pretreated substrate
2
was cured 1 h at 200°C.
The humidity exposure of zinc-coated steel with waterborne primer and polyester
topcoat was less deleterious than the salt spray. A higher concentration of an adhesion pro-
3
moter enhanced durability. The locus of failure is generally in the organic phase but a sig-
3
nificant amount of failure was observed at or close to the coating/substrate interface.
Ink-jet printed conductive copper patterns were fabricated using a conductive copper
ink containing 3 wt% silane (3-aminopropyltrimethoxysilane) coupling agent as an adhe-
4
sion promoter.
Silicon alkoxides sol-gel pre-treatments (γ-glycidoxypropyltrimethoxysilane, tetra-
ethoxysilane, and methyltriethoxysilane) act as coupling agents between metal substrates
5
and organic coatings. The hot dip galvanized steel sheets and copper AlSi Mg aluminum
7
alloy have an improved corrosion resistance and a reduced delamination of the coating
5
when pretreatment is used.
Diethylenetriamino-diethylphosphate was used as adhesion promoter with diglyci-
6
dylether of bisphenol A resin and OH–terminated polydimethylsiloxane. The lap shear
6
strength almost doubled with the use of this adhesion promoter.
The primer containing 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropy-
7
ltrimethoxysilane produced high shear bond strength between dental resin and titanium.
Using sum frequency generation vibrational spectroscopy for polybutadiene-modi-
fied epoxy rubber at surfaces and buried interfaces with gold, it was found that the vinyl
methylene groups were highly tilted and twisted at the surface whereas the vinyl methyl-
8
ene groups were highly tilted at the Au interface (Figure 8.5). The segregation and mor-
phological structure formation of the adhesion promoter on the substrate surface generally
occur when the matrix is in contact with the substrate, leading to the desired chemical or/
8
and physical interaction towards the substrate.

Figure 8.5. Chain alignments on silica and gold. [Adapted, by permission, from Fang, Y; Li, B; Yu, J; Zhou, J;
Xu, X; Shao, W; Liu, X, Surf. Sci., 615, 26-32, 2013.]