Mechanical Relaxation Peak Research Articles

Amorphous linear polyethylene: Annealing effects

Abstract The effect of annealing amorphous linear polyethylene films prepared by an improved ultraquenching technique at temperatures just below and above a dynamic mechanical relaxation peak (torsion braid) observed at ∽190K has been characterized by electron microscopy and torsion braid analysis. Based on the results described, this peak is believed related to the lower glass transition temperature Tg(L), the Tg of wholly amorphous linear polyethylene, whereas the β peak at 260K is Tg (upper). Annealing just below Tg (L) results in a growth in size of the nodules observed in the as-quenched samples, whereas annealing above Tg (L) can result in the growth of single crystal-like structures, spherulites, and shish-kebobs. Storage of the crystallized samples at room temperatures results in a decrease in size of the relaxation peak during subsequent torsion braid spectroscopy measurements. The results indicate significant amounts of molecular motion can occur during crystallization even at Tg.

A possible high-frequency mechanical relaxation peak in b.c.c. metals

A possible high-frequency mechanical relaxation peak in b.c.c. metals

Theory of Mechanical Relaxation Peaks in Cold‐Worked Metals

AbstractInternal friction peaks, which appear in cold‐worked metals above the Bordoni peak temperature, are considered, on the basis of a point defect‐associated dislocation model, to be due to relaxation. Calculated data regarding activation energies, pre‐exponential factors, and relaxation strengths are compared with experimental data of ten metals, an alloy, and an ionic crystal. These data thus gives experimental values for the binding energy between dislocations and the point defects concerned (e.g. vacancies, interstitial atoms, impurity atoms, etc.).