In addition, the book provides basic introductory information on the role of plasticizers in the modification of polymers, basic quality requirements, and the latest trends in the synthesis and use of plasticizers in industry, also presenting the available methods of PET recycling, with particular emphasis on chemical recycling, analysis of the PET market, the availability of postconsumer PET, and its value as a raw material for other products. Based on the authors’ research, the book discusses the use of postconsumer PET in the synthesis of monomeric and oligomeric plasticizers. Synthesis conditions are shown in detail, and the influence of the structure of synthesized softeners on their basic quality parameters are assessed and compared with selected commercially available products. In the final sections, the book covers the economic challenges and benefits of this process and its application to newly developed products.