Internal friction in polyoxymethylene

Mechanical relaxation was studied in bulk polyoxymethylene by means of a torsion pendulum. The magnitude of the large γ peak at 203°K. (for f = 1.1 cycles/sec.) decreases with increasing density. The magnitudes of the β peak at 260°K, and the α peak at 400°K. do not depend on density. The β peak is small unless the specimen contains water or has just been cooled from a temperature above ca. 370°K. The activation enthalpies of the α and γ relaxations are 24 and 27 keal./mole, respectively. The relaxation time distribution and activation enthalpy of the γ relaxation do not depend on density.