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[摘要]：Novel volume measurements on an epoxy resin subjected to carbon dioxide pressure jumps (PCO2) are used to investigate the structural recovery of glassy polymers after plasticizer jumps. Previously, we had investigated an epoxy resin after plasticizer concentration jumps using relative humidity (RH) and CO2 and evidenced structural recovery and physical aging responses.(1-6) In that work, two things were demonstrated: (a) qualitatively, the physical aging (after CO2 and RH jumps) and structural recovery (after RH jumps) responses are similar to those observed after temperature jumps, and (b) quantitatively, the responses are not the same and, moreover, they exhibit anomalous behaviors. The purpose of the present work is to further investigate the nature of the anomalous behaviors by investigating the structural recovery response of the same epoxy when subjected to PCO2-jump conditions. We provide new data using CO2-jumps and show intrinsic isopiestics, asymmetry of approach, and memory effect and then compare these with similar data for temperature-jump histories. We show that the extended Kovacs-Aldonis-Hutchinson-Ramos does not adequately describe the structural recovery of the epoxy resin after PCO2-jumps. This is consistent with what was previously observed in our laboratory on modeling the structural recovery data of the epoxy resin subsequent to relative humidity changes. Finally, we show a further anomaly in that the volume in CO2-jump experiments seems to evolve toward a different final state(23) than it does in temperature-jump experiments, suggestive of a metastable glassy state that differs from that of the temperature-jump created glass. |
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