This part of the UNE 53-277 series of standards contains the unified symbols for plasticizers. Only those symbols that are commonly used are included in this standard. 2 The purpose of this part of the UNE 53-277 series of standards is to prevent more than one symbol from being applied to a given plasticizer. The symbols are intended to be a suitable abbreviation of chemical names that appear in publications and other writings. NOTE- Plasticizer mixtures are not considered in this part of the UNE 53-277 series of standards.