Sorption and plasticization effects of ethanol–toluene–isooctane ternary mixtures in polyamide 6,6 and induced plasticization effects

• Sorption of ethanol–toluene–isooctane mixtures (EX) in polyamide 6,6 is quantified.
• As a non-polar solvent, toluene is absorbed in small amount in PA66.
• Toluene has a very strong plasticization effect (Tg drop) on PA66.

The equilibrium sorption of ethanol–toluene–isooctane ternary mixtures (EX) in polyamide 6,6 (PA66) films is studied. These mixtures being strongly non-ideal, the thermodynamical activity of each component must be determined in the vapor phase, so as to determine the equilibrium sorption in PA66. A GC (Gas Chromatography) analytical technique was used to quantify the composition of vapor phases at room temperature. After equilibrium sorption of PA66 films in contact with EX mixtures, the desorbing vapors were analyzed and quantified. It is found that, even though it is a non-polar solvent which is absorbed in relatively small amount in PA66, toluene has a stronger effect on the material than ethanol, relatively to its molar content. The presence of a small quantity of absorbed toluene increases ethanol sorption at a given ethanol activity. At a given molar content, the Tg drop induced by toluene is almost three times larger than that induced by ethanol. These observations indicate that toluene sorption is driven by complex molecular mechanisms and cannot be described by a mean-field picture.

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