Chemical and physical effects during spontaneous relaxation of a network-structure glass

David L. Sidebottom, G. P. Johari

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Changes in the dielectric properties during isothermal ageing of a network-structure glass have been measured. The height of the sub-Tg relaxation peak initially increases on ageing, reaches a maximum value and then decreases. The initial increase is caused by the chemical reactions that increase the glass transition temperature towards a limiting value and produce an -OH group in a relatively loosely packed region of the amorphous matrix. When the matrix becomes almost completely crosslinked or when no further reaction occurs, spontaneous densification causes a decrease in the height of the β-relaxation peak. Thus the effects of isothermal ageing involves two process: chemical, that dominates during the early period, and physical, that ultimately determines the dielectric behavior. The increase in the dielectric permittivity as a result of chemical reaction calculated from the increase in Tg and the configurational entropy theory is one third the measured value. This indicates that the molecular rotational diffusion in local regions of the amorphous matrix involves also groups other than those produced by the chemical reaction. The stretched exponential decay parameter was calculated from the limited data here and using a procedure given earlier. Its value of 0.11 is independent of the ageing time.

Original languageEnglish
Pages (from-to)205-211
Number of pages7
JournalChemical Physics
Volume147
Issue number1
DOIs
StatePublished - Oct 15 1990
Externally publishedYes

Fingerprint

chemical effects
Aging of materials
Chemical reactions
Glass
chemical reactions
glass
matrices
densification
Densification
Dielectric properties
glass transition temperature
dielectric properties
Permittivity
Entropy
permittivity
entropy
causes
decay

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Spectroscopy
  • Atomic and Molecular Physics, and Optics

Cite this

Chemical and physical effects during spontaneous relaxation of a network-structure glass. / Sidebottom, David L.; Johari, G. P.

In: Chemical Physics, Vol. 147, No. 1, 15.10.1990, p. 205-211.

Research output: Contribution to journalArticle

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