CREEP, STRESS RUPTURE, AND ISOTHERMAL AGING OF REINFORCED POLYPHTHALAMIDE

The effects of time, temperature, and particulate filler on the tensile behavior of short fiber-reinforced polyphthalamide (PPA) were investigated experimentally. Creep and stress-rupture characteristics and tensile properties before and after isothermal aging were determined. Temperatures ranged from 23 to 150 degrees C and tests lasted up to about 4000 h. Stress-rupture master curves were created, using a WLF-type analysis, which can be used for interpolation with reasonable accuracy. Creep rates were low but were affected by increased moisture absorption in the lowest temperature environment. All properties were affected by chemical degradation of the PPA matrix at the highest temperature. Under most conditions investigated, the mineral filler improved the creep resistance and stiffness of the PPA resin at the expense of strength and ductility. Scanning electron microscopy examinations of fractured specimens indicated that the mineral filler embrittled the matrix and may have damaged the fibers during processing. (C) 1995 John Wiley and Sons, Inc.