AbstractThe evaporation of the solvent 1,2,3,4‐tetrahydronaphthalene from the ternary system polystyrene/polybutadiene/tetrahydronaphthalene was studied. Ternary solutions of precisely known weight concentrations were prepared and then dried under vacuum and elevated temperatures. When the solution was assumed completely dried to a solid, the solvent content was calculated by difference. The deviation between the two solvent contents, namely, that known by exact weighing of components and that calculated after drying, was found to be significant, the reason for this discrepancy resting in the fact that solvent is assumed entrapped in the polystyrene fraction of the polymer residue. The possibility of the formation of interpenetrating networks causing this solvent entrapment is discussed as is a possible means of achieving more efficient solvent evaporation.