ISSN:
0887-6266
Keywords:
polycarbonate, cyclic stress and aging of
;
differential scanning calorimetry (DSC) of polycarbonate under cyclic stress
;
craze initiation and fatigue in glassy polymers
;
glassy initiation and fatigue in glassy polymers
;
glassy polymers, stress and enthalpy relaxation in
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Possible effects of cyclic stress on physical aging in polycarbonate were investigated using differential scanning calorimetry (DSC) measurements. When the enthalpy overshoot by DSC of specimens of different previous thermophysical aging histories is measured as a function of the cyclic stress amplitudes, two characteristic regimes are observed. By correlating with optical microscopic observations, these regimes are identified as the incubation and crazing stages (denoted regimes I and II, respectively). The enthalpy relaxation behavior in Regime I is similar to thermophysical aging, indicating that the glassy structure as a whole is initially shifted to one where molecular mobility is retarded by relatively low amplitude cyclic stress. A strong interaction is also seen between the enthalpy overshoot and previous physical aging. That is, the more the material is previously aged, and the shorter the incubation period, the longer the crazing region is. As a result, brittle failure occurs over a wider load range compared with less aged specimens.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/polb.1992.090300301
Permalink
