Dynamic elastic behavior or high polymers at audiofrequencies

Abstract

AbstractA brief description is given of the use of a resonant‐bar type apparatus for measurement of the dynamic elastic modulus and the associated damping or internal friction of a solid polymer. Each different type of polymer is found to exhibit a characteristic internal friction spectrum when explored over the temperature range from liquid nitrogen temperatures to the melting point. These spectra are characterized by the occurrence of one or more peaks in the mechanical loss data centered about certain temperatures, accompanied by an associated drop in dynamic modulus. By variation of polymer composition and of polymer structure, by addition of low molecular weight compounds, and by subjection of samples to irradiation, considerable additional information can be gained that would be helpful in determining the nature of the molecular mechanisms that are responsible for the observed transitions. Dynamic mechanical data are presented and discussed for a series of poly(alpha olefins) with methyl, ethyl, propyl, isopropyl and isobutyl side chains to depict the effects of crystallinity, side chain length and side chain structure on the observed transitions.