Characterization of interfacial adhesion in binary polymer blends: a new approach based on positron lifetime study

A new method of characterizing the adhesion at the interface of partially miscible and immiscible binary polymer blends based on free volume concept is described here. The efficacy of the method is tested in four binary polymer blend systems namely PS/PMMA, PVC/EVA, PP/NBR and PVC/SAN. The usefulness of hydrodynamic interaction is exploited which is derived from free volume data to understand the changes at the interface. We understand that if the adhesion at the interface is good it exhibits large negative values for hydrodynamic interaction parameter alpha, a measure of excess friction at the interface. The thermal properties (indicated by T(g)) also improve for this condition. To show that the method is sensitive to the changes at the interface, we modified the interface through microwave and e-beam irradiation and found from a characterization, that blends with polar groups exhibit interface stabilization for microwave irradiation while e-beam is good for blends with no polar or weak polar groups.