Factors affecting the strength of a polyhydroxy ether

The effects of moisture content, aging, annealing, irradiation, temperature, and rate of testing on the tensile yield strength of the polyhydroxy ether derived from bisphenol A and epichlorohydrin are described and discussed. In particular, annealing at temperatures below Tg is shown to cause significant increases in strength which are associated with an endothermal process in the glass transition region having an activation energy of 32.8 kcal./mole. The nature of this process and its occurrence in other polymers is discussed. Annealed and unannealed specimens are shown to obey the previously proposed empirical relationship, 1/σ = a + m log t, where σ is the tensile yield strength, t is the time to yield. The values of the constants a and m have been derived.