Measurements of first and second normal stress differences in a polymer melt

Abstract A study of the first and second normal stress differences was made in order to determine the properties for an LDPE melt at high shear rates. Time dependent measurements of N 1 and N 2 were carried out using cone/plate and plate/plate rheometry, in order to extend the shear rate for rotational rheometry up to 120 s −1 . Measurements utilizing the pressure hole method extended the shear rate range to approximately 1000 s −1 . For N 1 there is an overlap in the data, that is within the experimental error, for N 2 the data is inconsistent in behaviour. Both N 1 and N 2 initially demonstrated a power law behaviour, but converged to a plateau at high shear rates. This behaviour is believed to be a true response of an oriented polymer network and not slip.