Effects of uniaxial stretching and shrinkage on proton spin-lattice and spin-spin relaxation times of isotactic polypropylene

Abstract

An isotactic polypropylene film was stretched at 120 ~ in poly (ethylene glycol) and thermally shrunk at various temperatures. Proton spin-lattice, T1, and spin-spin, T2, relaxation times were measured using a broad line pulse spectrometer operating at 19.8 MHz in the temperature range 40 ~ ~ The temperature of T I minimum shifts to higher temperatures and the value of T 1 minimum increases in magnitude as the stretching ratio is increased. In contrast the temperature of T1 minimum shifts to lower temperatures as shrinkage is increased, whereas the value of T1 minimum increases in magnitude because of the increase in crystal]inky during shrinkage. T2a , the longest T 2 associated with the mobile amorphous regions, increases during shrinkage, indicating that chain mobility in the amorphous regions increases substantially during shrinkage. It was found that an orientation function of the amorphous regions, [a, correlates well with T2a.

Metallocenic Copolymers of Isotactic Propylene and 1‐Octadecene: Crystalline Structure and Mechanical Behavior

“…The values used are [28] r a ¼ 0.858 g Á cm À3 and r c ¼ 0.936 g Á cm À3 . Wide-angle X-ray diffraction (WAXD) patterns were recorded in the reflection mode at room temperature by using a Philips diffractometer with a Geiger counter, connected to a computer.…”