Kinetics of Radical Decay and Molecular Dynamics in Oriented High Modulus Polyethylene

Abstract

The kinetics of decay of macroradicals in irradiated ultradrawn (draw ratio 200) high modulus polyethylene, single crystal mats of polyethylene and polyethylene with extended chain crystals was studied comparatively by the ESR technique. The results were analyzed from the viewpoint of correlations between the microstructure and temperature-dependent chain dynamics of the polymers. The actual absence of appreciable radical decay in the temperature range 200–300 K and a remarkable stability of considerable fraction of initial radicals at higher temperatures in high modulus sample were explained by extremely restricted motion of the fragments of unfolded tie molecules in trans-conformations predominating in the amorphous region of this polymer. In addition, direct evidences for drastic conformational changes in amorphous regions of polyethylene as a result of ultradrawing obtained by IR-spectroscopy are reported.

Key Words:

• High modulus polyethylene
• macroradicals
• decay
• electron spin resonance
• infrared spectroscopy
• molecular motion.