A Comparative Investigation of the Rheological Properties of Melts of Unimodal and Bimodal Polyethylene under Shear and Elongation

Abstract

An investigation was made of tube grades of high-density polyethylene with a unimodal and a bimodal molecular weight distribution during shear and longitudinal deformation under constant force conditions. It was shown that these polymers have similar melt flow indices and flow curves but differ considerably in other characteristics during shear deformation and in their behaviour during longitudinal deformation.

Mechanochemical tuning of molecular weight distribution of styrene homopolymers as postpolymerization modification in solvent‐free solid‐state

“…[ 6 ] In this regard, bimodality has shown to be the most suitable characteristic of MWDs to control rheological, mechanical and processability properties simultaneously, which is attributed to the fact that the component with lower molecular weights influences in the processability and the component with higher molecular weight regulates the mechanical properties. [ 1–3,7–9 ] Methods to control MWD are generally based on the manipulation of specific variables during the polymer synthesis or performed using melt or solution blending of different MWDs. [ 8–14 ]…”

“…[6] In this regard, bimodality has shown to be the most suitable characteristic of MWDs to control rheological, mechanical and processability properties simultaneously, which is attributed to the fact that the component with lower molecular weights influences in the processability and the component with higher molecular weight regulates the mechanical properties. [1][2][3][7][8][9] Methods to control MWD are generally based on the manipulation of specific variables during the polymer synthesis or performed using melt or solution blending of different MWDs. [8][9][10][11][12][13][14] In the literature, we have found reports regarding the feasibility of tuning MWDs using mechanochemical degradation with different techniques; yet, these works were focused on the interpretation of mechanochemical degradation, the establishment of kinetic degradation rate or finding the limiting molecular weight.…”