On the scaling law of the evolution of lap-shear strength with healing temperature at amorphous polymer-polymer interfaces and surface glass transition

摘要

The evolution of lap-shear strength (σ) with healing temperature T_h at symmetric and asymmetric amorphous polymer-polymer interfaces formed of the samples with vitrified bulk has been investigated. It has been found that the square root of the lap-shear strength behaves with respect to healing temperature as σ~(1/2) ~ T_h both at symmetric and asymmetric interfaces. Basing on this scaling law between σ and T_h, the values of the surface glass transition temperature (T_g~(surface) have been estimated for a number of amorphous polymers by the extrapolation of the experimental curves σ~(1/2) ~ T_h, for symmetric polymer -polymer interfaces and, in some cases, for asymmetric, both compatible and incompatible, polymer-polymer interfaces, to zero strength. A significant reduction in surface glass transition temperature T_g~(surface) with respect to the glass transition temperature of the polymer bulk (T_g~(bulk), reported earlier, has been confirmed by the use of the new proposed approach. The quasi-equilibrium surface glass transition temperature T_g~(surface) of amorphous polystyrene (PS) has been predicted in the framework of an Arrhenius approach using the plot "logarithm of healing time -reciprocal surface glass transition temperature T_g~(surface'') and the activation energy of the surface alphα-relaxation of PS has been calculated.