The present work studies the effect of interfacial adhesion on the brittle ductile transition (BDT) in PVC/NBR by strengthening the interfacial adhesion through an increase of the acrylonitrile (AN) content in NBR The rubbers

NBR18 and NBR26

consist of 18 and 26 wt % of AN

respectively There are two BDT master curves for PVC/NBR blends

when impact strength ( S I ) is plotted against matrix ligament thickness ( T=T(d

σ

φ )

where d is the NBR particle diameter

σ the dispersity of particle diameter

and φthe volume fraction of dispersed phase

respectively.)Below the critical value Tcof T

the blend becpmes extremely tought.At any given T the SI of PVC/NBR26 is lower than that of PVC/NBR18

and the transition in PVC/NBR26 occurs at a lower T value

indicating that strong interfacial adhesion is not favorable for achieving high toughness.The stress whitening zone and SEM photograph of fracture of the samples shows that

as interfacial adhesion is too strong

interfacial debonding and hence cavitation is hindered

thereby delaying the occurrence of shear yield deformations.