The role of interfacial contact in immiscible binary polymer blends and its influence on mechanical properties

In this paper an immiscible blend comprised of a crystalline(polyethylene) and an amorphous(polycarbonate) component was studied. Depending on whether the crystalline material is the dispersed phase or matrix, high levels of voiding or good apparent contact, respectively, can be observed. It is shown that the system PC dispersed in HDPE displays a tensile modulus which mimics theoretical behaviour for perfect adhesion even in the absence of an interfacial modifier. The complementary blend of HDPE in PC with the voided interface displays all the characteristics of PC containing dispersed air. The transition from one behaviour to the other is closely related to the estimated region of phase inversion. The same pseudo-adhesion behaviour was not observed in a second amorphous/crystalline system (polystyrene and polyethylene). It is suggested that in order for this behaviour to occur a contraction of crystalline matrix must take place onto a rigid dispersed phase (below its glass transition).