Oligomer-Metal Interphase Tension

Earlier we considered the regularities of the effect of simfactants on the oligomer surface tension. The properties of adhesive-bonded joints are also determined by the character and the magnitude of the interaction at the adhesive-substrate interface, which to a greater extent is characterized by the magnitude of the interphase tension [82]. Study of the interphase tension is of great theoretical and practical interest, but at present there are no direct methods for its determination. 

Polarographic measurements were carried out using the LP-60 instrument with the EZ-2 autographic recorder and with the dropping mercury electrode. For aqueous solutions a silver chloride electrode served as anode in the case of nonaqueous solutions the bottom mercury was the anode. The anode potential did not change significantly in the aqueous and nonaqueous solutions with surfactants cathode polarization was checked by means of the three-electrode circuit relative to the normal calomel electrode. 

It is first necessary to select the range of copper ion concentrations in which the maximiun of the wave is most sensitive to the additions of the compounds under study. For this purpose an equal quantity of solution of the compoimds under study is added to solutions of various copper concentration and the difference in the maximum heights is determined before and after surfactant is added. The difference in magnitude increases initially with increase of the copper concentration, then, having reached a certain limit, remains practically unchanged. With these considerations, the copper concentration for the studies was taken as 0.26-0.43 kg/m because, in this case, linear dependence is observed between the maximum height and the copper concentration. 

Since the alteration of the polarization capacity (c) and rate, and the capacity itself, depend on the potential, a better picture of the adsorption can be obtained by using the relative values of Ac/ci = AV/V2, where V2 is the rate of the polarization with surfactant present. From the AVfY —E relationship one can estimate the adsorption of surfactant under study within a potential range limited only by the depolarization process. 

TABLE 2.7 Polarographic Study of Surfactant Adsorption in Water and in DMFA 

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For the study of the interphase tension at the boundary between the oligomer and a metal, a model system was used in which liquid mercury was used for the metal. The mercury was thoroughly purified and distilled prior to use. The interphase tension was determined hy the sessile drop method [230]. The error was estimated as 3mN/m. The oligomers and adhesives based on them were ED-20 epoxy resin-hased adhesive with PEP A curing agent (12%) and PN 609-2IM polyester resin-based adhesive with MEKP(O). 

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