Iso-free Volume Theory on Crosslinked Polymers
1962 Volume 19 Issue 204 Pages 219-223
Details
1962 Volume 19 Issue 204 Pages 219-223
Flory's iso-free volume theory of glass transition phenomena has been widely accepted. However, its original expression. (T. G. Fox and S. Loshaek: J. Polymer Sci., 15, 371 (1955)), should be modified in the case of crosslinked or crystalline polymers, since the localization of the free volume may cause a certain decrease in the value of specific volume below the glass temperature.
Experimental results on styrene-butadiene copolymers and alkyd resins show that a linear relationship between vg and Tg still hold in these cases but the sign of B is negative.
The concept of localization of free volume can account for these results, definingthe degree of localization of free volume by where αa and αb denote the thermal expansion coefficient above and below the glasstemperature respectively.
β is supposed to reflect the mode of crosslinking and other detailed structural factors.
