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

Abstract

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 gsurface) 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 Tgsurface with respect to the glass transition temperature of the polymer bulk (Tgbulk), reported earlier, has been confirmed by the use of the new proposed approach. The quasi-equilibrium surface glass transition temperature Tgsurface 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 Tgsurface″ and the activation energy of the surface alpha-relaxation of PS has been calculated. © 2011 Springer-Verlag.