Nuclear Magnetic and Mechanical Relaxations in the γ-Loss Band of Linear Polyethylene Treated with Fuming Nitric Acid

Abstract

Measurements of the NMR second moment and mechanical loss tangent for solution-crystallized polyethylene treated with fuming nitric acid at 80°C for 20 h reveal a relaxiation region around –140°C. The relaxation (correlation-time) spectrum for this relaxation region is in good agreement with that for the γ3-relaxation, which is one of the component relaxations of the γ-loss band of untreated polyethylene crystallized from the melt or solution. The γ1- and γ2- relaxations existing in untreated polyethylene are greatly decreased by this treatment. The observed change in the second moment in the γ3- region (ca. 1.5 gauss2), is explained as being due to the rotational motion of part of the ciliary chain on the lamellar surface. It is found that absorbed water changes this relaxation into a new one similar to the γ2-relaxation.