Ultrasonic wave propagation, dynamic mechanical analysis, and dielectric analysis were used to monitor relaxation phenomena during the nonisothermal postcure of unsaturated polyester networks. The measurements covered 6 decades of frequency. As a result, the residual reactive groups, immobilized in the glassy state by vitrification during an isothermal cure step, gained molecular mobility, which promoted the formation of additional crosslinks. After the postcure, the reaction was complete, and the maximum achievable glass-transition temperature was reached. Moreover, the frequency and temperature dependence of the two relaxations, one related to the glass-transition temperature of the partially cured sample and the other to the glass transition of the fully cured sample, was evaluated. The Williams–Landel–Ferry equation was used to model the frequency dependence of the main -relaxation data obtained with the different techniques.

Relaxations during post-cure of unsaturated polyester networks by ultrasonic wave propagation, dynamic mechanical analysis and dielectric analysis

LIONETTO, Francesca;MAFFEZZOLI, Alfonso
2005

Abstract

Ultrasonic wave propagation, dynamic mechanical analysis, and dielectric analysis were used to monitor relaxation phenomena during the nonisothermal postcure of unsaturated polyester networks. The measurements covered 6 decades of frequency. As a result, the residual reactive groups, immobilized in the glassy state by vitrification during an isothermal cure step, gained molecular mobility, which promoted the formation of additional crosslinks. After the postcure, the reaction was complete, and the maximum achievable glass-transition temperature was reached. Moreover, the frequency and temperature dependence of the two relaxations, one related to the glass-transition temperature of the partially cured sample and the other to the glass transition of the fully cured sample, was evaluated. The Williams–Landel–Ferry equation was used to model the frequency dependence of the main -relaxation data obtained with the different techniques.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11587/109098
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 30
  • ???jsp.display-item.citation.isi??? 27
social impact