Abstract
The interaction between amorphous non-polar polymer and non-polar solvent was examined using atactic polypropylene-n-paraffine systems with sorption method. In the higher relative vapor pressure region of sorption isotherm, the smaller the solvent molecule is, the more is it sorbed. The Flory-Huggins' parameter X1, is not constant in these systems over the whole relative vapor pressure range. In the case of polypropylene-n-pentane system, X1 versus pressure relation has a maximum, while that of the golypropylene-n-heptane system has a minimum at certath relative vapor pressures. These trends are explained by the combination of surface adsorption mechanism, increase of affinity of polymer to solvent with increase of pressure, and swelling effect (effect of elasticity of polymer network chains) which resists sorption.
The sorption isotherm of polypropylene-n-heptane system at 25°C is lower than that at 35°C. From the X1 vs. P/P0 relations, it is observed that when the temperature is low, the effect of swelling mechanism becomes remarkable because the region which does not contribute to the sorption increases.
It is clear that the atactic polypropylene has the distinct cohesive energy distribution, and from lower to higher cohesive energy region in succession, the polymer achieves a mare stable solvated state by the dissolving action of solvent.
