|
|
|
| Mechanical Spectroscopy Investigation of Poly(vinyl acetate) Melt |
| WU Xuebang,ZHU Zhengang,ZHOU Xuemao,LIU Changsong |
| (Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China) |
|
|
|
|
Abstract The molecular relaxation dynamics in poly(vinyl acetate) (PVAc) was studied by mechanical spectroscopy above the glass transition temperature (Tg). The temperaturedependent mechanical spectra reveal the existence of two relaxation modes: α, ascribed to the glass transition, and α′, which might be related to the liquidliquid transition. The relaxation time follows VogelFulcherTamman law for both of the relaxation modes. A detailed analysis of the frequencydomain spectra above Tg shows a dynamic crossover at temperature TB ≈387 K through the temperature dependence of relaxation time, relaxation strength, and shape parameter. According to the phenomenological coupling model, the crossover is suggested to be caused by the strong increase of intermolecular cooperativity below TB with decreasing temperature.
|
|
Received: 01 May 2009
Published: 31 May 2010
|
|
|
|
|
|
|
|
|
