Cohesive plateau

Similar to the tackifiers discussed earlier, plasticizers have a very dramatic softening effect on the rubbery plateau modulus of the PSA. For this reason, high levels of plasticizers have to be avoided to maintain good cohesive strength in the adhesive, especially at elevated temperatures. Indeed, if high cohesive strength is desired, the amount of plasticizer used in a PSA is typically kept to a minimum, if used at all. 

Soap solution admirably fulfils Plateau s second condition, its surface tension being only about 40 per cent, of that of water, while its cohesion is also very small and it is doubtless to this property that its emulsifying power is chiefly due. So far as viscosity is concei ned, this can have but little influence, for a 1 per cent, solution of sodium oleate, which has a viscosity very little different from tliat of pure water, is an excellent emulsifying agent. 

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