Relaxation phenomena in homopolymers and copolymers of ethylene and propylene

The physical properties of ethylene–propylene copolymers depend partly on the overall proportions of the monomers and on the arrangement of the two monomers within the polymer. The effect of composition upon the glass transition and related relaxation is reported, with comparisons drawn from dilatometry, dynamic mechanical loss, and measurements of nuclear magnetic resonance absorption. The relaxation times ranged from about 103 sec. to about 10−7 sec. The copolymers varied in composition from an ethylene: propylene mole ratio of 85:15 to a ratio of 16:84, and the homopolymers were also studied. The relaxation phenomena are interpreted qualitatively in terms of the expected temperature dependence of the spectra of frequencies of molecular motion.