Transient Elongational Viscosities and Drawability of Polymer Melts

摘要: Transient elongational viscosities of polyethylene melts from converging flow (entrance pressure losses) and uniaxial stretching after extrusion (Rheotens test) are compared with steady‐state obtained by isothermal homogeneous drawing in different rheometers. The laboratory tests allow predictions on differences the drawability (minimum film thickness) tubular blowing. If shear two low‐density (LDPE) same, material exhibiting lower level viscosity can be stretched to higher total strains before break. shape die is shown have a significant influence subsequent behavior due preorientations imposed during extrusion. Converging decreases drawability, whereas diverging dies yield an increase maximum pulling speed temperature dependence drawdown force Rheotens test predicted flow‐activation energy melt...