The viscoelastic responses for the melts of low density polyethylene (LDPE)/ethylene-vinyl acetate copolymer (EVA)/nanoclay composites containing different contents of nanoclay were studied.It is found that the viscoelasticity dependence of the melts on shear rate

shear strain and shear history is related with the dispersion and amount of nanoclay added.A negative primary normal force difference (N1) appears when the composites are sheared at lower shear rate during steady flow

while N1 is independent of the nanoclay amount at higher shear rates.Moreover

compared with the polymer matrix

the composites exhibit different dependence of transient stress or N1 on the strain.The viscoelastic responses of polymer matrix are independent of the pre-shear that the samples are exposed to.However

for the composites containing 3 wt% or more nanoclay

the level of transient stress

stress overshoot and the steady stress observed in flow reversal experiments with pre-shear are found to be lower than those of the samples without pre-shear.With the increasing of nanoclay content

the differences of transient stress at steady state increase for the composites with and without pre-shear

and a positive N1 instead of a negative one appears for the composites subjected to pre-shear.It is believed that the layers of nanoclay are exfoliated or intercalated by polymer chains

resulting in the formation of directors in the polymer matrix.The reason for the composites melts showing abnormal nonlinear viscoelastic response is ascribed to alignment or orientation of the directors under shear stress.