PHYSICAL AGING BEHAVIOR OF A POLY(ARYLENE ETHERIMIDE)

The effects of physical aging on the mechanical and thermal behavior of a high performance engineering resin, poly(arylene etherimide) (PEI), were characterized as a function of aging time and temperature using dynamic mechanical spectrometry (dins), room temperature tensile tests, and differential scanning calorimetry (dsc). The aging temperature range investigated extended from Tg — 140°C to Tg—20 °C. dins and tensile measurements demonstrated that aging for 1000 and 10 000 min at temperatures as low as 7-140 °C had a significant influence on the mechanical behavior of PEI. Shift rates (/z), as defined by isothermal increases in the dynamic storage modulus (£') as a function of frequency, ranged from 0.4 to 3.0 with increasing aging temperature. Dynamic loss modulus measurements (Eʹ) demonstrated that PEI has a pronounced/3 relaxation which exhibits a significant decrease in magnitude with aging. Suppression of this relaxation paralleled dramatic changes in the room temperature stress-elongation behavior of PEI. Increases in yield strength after aging for 10 000 min were as large as 16%, while elongations at break decreased by as much as 64%. While mechanical measurements demonstrated aging effects for all temperatures studied, changes in thermodynamic behavior by dsc, occurred only after aging at temperatures greater than Tg—55 °C. © 1986, American Institute of Physics. All rights reserved.