Thermorheological behavior of polyethylene: Effects of microstructure and long chain branching

The independent and combined effects of long and short chain branching on t he thermorheological behavior of polyethylene are described. The activation energy of linear poly(ethylenebutene) increases,vith butene content to app roximately 33-34 kJ/mol and then levels off for butene contents between 7 a nd 25 wt %. Long chain branched homo-polyethylene is thermorheologically co mplex and is most sensitive to temperature at low frequency. A technique fo r determining the activation energy spectra of thermorheologically complex materials is proposed. Short and long branches in the same system synergist ically increase the zero-shear rate activation energy.