REMARKS ON THE ALPHA AND BETA TRANSITIONS IN SWOLLEN POLYAMIDES

The glass transition (alpha) and secondary transition (beta) are compared in various aliphatic polyamides swollen by water, alcohol and acid. For all these polymer-solvent systems, the evolution of the temperature T alpha with the equilibrium sorption ratio presents two regimes. In the low-concentration regime, the dependence of T alpha on the number n of absorbed solvent molecules per accessible amide group follows a master curve independent of the nature of the system. No master curve is, however, observed for the beta transition. In the second regime, above a critical ratio n(*) dependent on the nature of both the solvent and the polymer, T alpha levels off, and the maximum concentration of absorbed solvent is proportional to n(*). These effects are explained in terms of solvent clustering around the amide groups.