a method for the separation of a mixture of polyvinyl chloride particles and polyethylene terephtalate particles comprising the steps of applying a solution composed of a low density solvent of polyvinyl chloride , water and sodium hydroxide to flakes of polyvinyl chloride and polyethylene terephtalate whereby the polyvinyl chloride absorbs the solvent contained in the solution , which changes the density of the polyvinyl chloride so that it is less than the density of the polyethylene terephtalate . the plastics may then be differential density separated by flotation or centrifugation and recovered .