Shear Damping Function Measurements for Branched Polymers

VEGA DA; MILNER ST

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS

Wiley

Lugar: USA; Año: 2007 vol. 45 p. 3117 - 3136

0887-6266

We present results for step-strain experiments and the resulting damping functions of polyethylene blends of diferent structures, including solutions of linear, star and comb polymers. Remarkably, an entangled melt of combs exhibits a damping function close to that for entangled linear chains. Diluting the combs with faster-relaxing material leads to a more nearly constant damping function. We nd similar behavior for blends of commercial low density polyethylene LDPE. Our results suggest a simple picture: on timescales relevant to typical damping-function experiments, the rheologically active portions of our PE combs as well as commercial LDPE are essentially chain backbones. When strongly entangled, these exhibit the Doi-Edwards damping function; when diluted, the damping function tends toward the result for unentangled chains described by the Rouse model- namely, no damping.