The structure of adsorbed silane films formed by the adsorption of trichlorosilane molecules containing long alkyl chains from solution onto aluminium substrates has been investigated. The structure of the adsorbed films is dependent on the alkyl chain length. When the chain length is equal to or greater than 18, the molecules form a film in which the hydrocarbon chains are densely packed together and orientated away from the substrate. As the chain length is reduced the films become progressively more disorientated. When a terminal vinylic group is present on the molecules, the films can be activated after adsorption to yield a hydroxyl group that is available for further reaction with a polyurethane resin. The ability of 10-undecenyltrichlorosilane and 18-nonadecenyltrichlorosilane to act as adhesion promoters has been investigated using the blister test. Both these silanes yielded adhesive fracture energies of 18 J m -2 under dry conditions. When water was present, only the joints pretreated with 18-nonadecenyltrichlorosilane exhibited a high resistance to moisture attack. In these joints the dense packing of the hydrocarbon chains impeded the diffusion of water to the interface. In the case of the adsorbed 10-undecenyltrichlorosilane films, the disorientated nature of these films allowed the water to reach the interface more easily, resulting in rapid joint failure.
Посилання на статтю:
Self-assembling monolayer silane films as adhesion promoters / N. G. Cave* and A. J. Kinloch // Polymer. – 1992. – Vol 33. – P. 1162-1170.
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