Rheo-optical studies of high polymers. XVIII. Significance of the vertical shift in the time-temperature superposition of rheo-optical and viscoelastic properties

✍ Scribed by Onogi, S. ;Sato, T. ;Asada, T. ;Fukui, Y.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1970
• Tongue: English
• Weight: 682 KB
• Volume: 8
• Category: Article
• ISSN: 0449-2978
• DOI: 10.1002/pol.1970.160080715

✦ Synopsis

Abstract

To determine the true reason for the increase in birefringence and the decrease in relaxation modulus for high‐density polyethylene with rising temperature, changes in crystalline structure as well as in thermal, viscoelastic, and rheo‐optical properties with temperature were measured, by several techniques, including DSC, DLI, infrared dichroism, x‐ray diffraction, and NMR. The values for degree of crystallinity obtained from the DSC fusion curve, density, and infrared absorbances coincide very well and show almost no divergence till about 80°C. The optical vertical shift factor pT can be related to the ratio of the orientation function for the crystal c axis at an arbitrary temperature to that at the references temperature, f~ε~/f~ε0~. The mechanical vertical shift factor b~T~, on the other hand, is associated with the temperature dependence of the mobile fraction, as determined by NMR measurements, but not with variations in degree of crystallinity.