Hydroxyl-terminated oligomers (PHO-diol) were obtained by transesterification when BDO was selected as the diol. This latter can notably be obtained from biomass or from waste plastics, such as poly(butylene adipate terephthalate) (PBAT) or poly(butylene succinate) (PBS), which are depolymerized by chemical hydrolysis . The chain ends of PHO-diol were then modified with hexyl (mono)isocyanate (HI), to obtain an end-capping with short alkyl chains (PHO-hexyl) with the aim to improve the additive's dispersion into the matrix, and its plasticizing effect. To test the different additives, formulations were made from rigid PVC and TPU, at different plasticizer concentrations. Commercial references based on phthalate groups, such as DPHP and DIDP were used. The chosen TPU was synthesized with a high content in cycloaliphatic sustainable betulin, which brings high rigidity and brittleness to the polymer, preventing its processability and thus making it hardly exploitable. These different formulations were then evaluated and characterized to determine the plasticizers efficiency, initially in terms of Tg evolution and mechanical properties.