Effects of moisture on the dimensional and viscoelastic properties of glassy polymers

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Title: Effects of moisture on the dimensional and viscoelastic properties of glassy polymers
Author: Zheng, Yong
Abstract: One cause of long -term dimensional changes in glassy polymers is the gradual evolution of the glassy structure and viscoelastic properties through aging processes in the glassy state . Many applications of polymers involve changes in relative humidity (RH ) , under which the materials exhibit aging processes that may differ from those in constant RH conditions . In this work , results from a study of a glassy epoxy subjected to isothermal RH -jumps are reported . Similar to the temperature jump experiments of Kovacs , the volume recovery responses in different histories , intrinsic isopiestic (constant RH ) , memory effect and the asymmetry of approach , are obtained . In addition , the effects of structural recovery on sorption and desorption of water and the physical aging responses of this epoxy resin are also measured . The experimental results qualitatively support the hypothesis that water has an effect similar to temperature on structure (volume , enthalpy ) of the glass -forming material . However , quantitatively , at the same RH -temperature states , the glasses formed by RH jumps show anomalous differences from those formed by temperature jumps . The conventional TNM -KAHR model is modified to fit the experimental results of isothermal RH jump experiments . Furthermore , application of the potential energy landscape theory to describe the glasses formed by relative humidity jumps , and especially to the observed differences between temperature glass and concentration glass , is discussed .
URI: http : / /hdl .handle .net /2346 /21289
Date: 2003-12

Citation

Effects of moisture on the dimensional and viscoelastic properties of glassy polymers. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /21289 .

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