NEW POLYMER PROCESSING AIDS OF YHE PHTALIC CLASS The paper presents results concerning the synthesis and characterization, as polymer processing aids, plasticizers and/or lubricants, of some diesters of unsymmetrical structure of phtalic anhydride, by taking into account aliphatic alcohols such as C3, C4, C6, C2-6, izo C10 and izo C13, along with complex alcohols of aliphatic-aromatic nature, such as phenoxy-ethanols. Three series of unsymmetrical diesters were performed considering as special alcohols the 2-phenoxyethanol, 2-<(o-sec butyl)phenoxy>ethanol and 2-<(p-nonyl)phenoxy>ethanol, respectively. The variation of the representative plasticizing and/or lubricating properties as a function of both the length of the aliphatic chain introduced by the aliphatic alcohol and the length and position of the alkyl pendant group existent on the aryl ring of the complex alcohol, was studied. Considering these alternatives, it was possible to obtain either plasticizing or lubricating properties as a function of the structural features. Thus, on the basis of the results recorded it was fully proved the valability and the consistency of the polyfunctionality and assimetry principles.