u201c principal u201d liquid may be a better solvent for the polymer than the second liquid and may have a surface tension at least 5 preferably at least 10 lower than the surface energy of the polymer involved the second liquid may be a solvent or a non solvent for the polymer and may have a surface tension at least 5 preferably at least 10 greater than the surface energy of the polymer the principal liquid may be at least 70 preferably about 80 to 95 by weight of the total liquid medium the principal liquid may dissolve the polymer at the temperature and pressure at which the solution may be formed the dissolution may generally take place near or above the boiling temperature of the principal liquid usually in a sealed container to prevent evaporation of the principal liquid the principal liquid may have a greater solvent strength for the polymer than the second liquid also the principal liquid may have a surface tension at least about 5 preferably at least about 10 lower than the surface energy of the polymer the lower surface tension may lead to better polymer wetting and hence greater solubilizing power the second liquid which may generally represent about 1 to 10 by weight of the total liquid medium may be miscible with the first liquid the second liquid may or may not dissolve the polymer as well as the first liquid at the selected temperature and pressure the second liquid may have a higher surface tension than the surface energy of the polymer preferably the second liquid may or may not wet the polymer.