Implications of the Melt Elasticity of Ldpe in the Film Blowing Process

The rate and temperature dependence of the extrudate swelling func tion, approximated by the least squares logarithmic parabola equation, was evaluated for five branched low density polyethylenes (LDPE) which differed significantly in processability. Assigning rheological significance to the parameters of the approxima tion equation, an explicit measure of processability of LDPE into film was demon strated in the form of the Universal Swelling Coefficient, A ^∞ The derived character istic relaxation times for shear and elongation flows (τ ₁₂ and τ ₁₁ , respectively) were subsequently employed in estimating the Deborah (De) and Brinkman (Br) criterial numbers, which are useful in designing the extrusion film blowing process on the basis of the LDPE melt elasticity function.